:COUPLING AGENT EFFECTS ON THE INTERFACIAL

ADHESION IN A SHEATH/CORE TYPE BICOMPONENT FIBER,

A Thesis Present to the Faculty of the college of

~ngineering and Technology Ohio university

In partial Fulfillment of the ~equirements

for the Degree Master of Science

By Jian-xing Li/ - March 1989

Acknowledgement

I wish to thank my advisors, Dr. John collier and Dr.

Billie Collier for their advice, guidance and help. I

would like to thank the college technical staff for their

help to modify the equipment, the ~ational science

Foundation for supporting this project, Avtex ~ibers

Incorporated, Allied Chemical and Dow corning corporation

for supplying the viscose rayon, nylon and polypropylene

monofilament, and the coupling agents. I wish to express

my special thanks to Mr. Richard L. Rabe for his help and

for his assistance with the photographic work.

Abstract

Rayon/nylon-6 and rayon/polypropylene bicomponent

S/C fibers were produced by a coating process. The purpose

of this research is to promote the interfacial adhesion

between skin and core materials to improve the durability

of the coating.

Fiber pretreatment techniques were used to improve

the surface properties of fiber before it was coated in

order to promote the interfacial adhesion of the S/C

fiber. Water was used to remove the spin finishes on the

synthetic fiber. Coupling agent solutions were used to

pretreat the fibers. Both pretreatment techniques were

sufficient to promote the interfacial adhesion at the

certain conditions. The effects of the pretreatment on

both adhesion and tensile properties of the S/C fibers

were determined.

TABLE OF CONTENTS

Page

....................................... List of Tabes IV

..................................... List of Figures VI

............................. Chapter I . Introduction 1

Chapter I1 . ~iterature Review ....................... 2

A . Bicomponent Fiber ........................... 2

B . The Properties of Rayon. .................... Nylon. and Polypropylene 7

1 . Rayon .................................... 7

2 . Nylon .................................... 14

............................ . 3 Polypropylene 1 8

................................. C . Spin Finish 21

........................ D . Interfacial Adhesion 22

............................. E . Coupling Agents 26

F . Interfacial Adhesion Test ................... 29

Chapter I11 . Experimental ........................... 3 3

A . Material and Equipment ...................... 3 3

B . Fiber Pretreatment Procedure ................ 3 5

1 . Removal Spin Finish ...................... 3 5

.............. 2 . Coupling Agent Pretreatment 36

C . Fiber Coating Procedure ..................... 36

D . Fiber Analysis and Testing .................. 4 5

1 . Linear Density ........................... 4 5

2 . Tensile Properties ....................... 46

.......... 3 . Interfacial Adhesion Properties 4 7

I1

a . Sample Preparation ................... 48

b . Test Procedure ....................... 48

.......................... . c calculation 49

4 . Surface Properties ......................... 49

a . Dyeability ........................... 49

............ b . Microscopical Observation 50

. ................... Chapter IV Result and Discussion 52

............................. . A Rayon/PP Fibers 52

. ..................... 1 Interfacial Adhesion 52

......... a . Effect of Spin Finish Removal 53

b . Effect of pH of the coupling ........................ Agent Solution 53

c . Effect of the Concentration of ........... the Coupling Agent Solution 55

d . Effect of Water Pretreatment Time ..... 59

e . Effect of Coupling Agent ...................... Pretreatment time 61

. ........................ 2 Tensile Properties 63

a . Effect of Coupling Solution .......................... Concentration 63

b . Effect of pH of the Coupling ......................... Agent Solution 63

c . Effect of the Pretreatment Time ........ 63

d . Summary of Pretreatment Effect on Tensile Properties .................. 64

. ................... 3 Qualitative Observation 64

I11

a . Microscopical Observation ............. 64

b . Dyeability ............................ 67

........................... B . Rayon/Nylon Fibers 72

...................... 1 . Interfacial Adhesion 72

a . Effect of Water Pretreatment Time ..... 73

b . Effect of Concentration of ........... the Coupling Agent Solution 76

........ . c Summary of Pretreatment Effect 78

........................ . 2 ensile Properties 79

................... . 3 Qualitative Observation 79

. ............. Chapter V Conclusion and Recommendation 84

A . Conclusion ................................... 84

B . Recommendation ............................... 85

References ............................................ 86 Appendices ........................................ 90

.......... A . Coupling Agent Solution Preparation 90

B . Experiment Data .............................. 91

TABLES

Table Page

Ranges of concentrations for

rayon spinning bath ......................... 11

Average degree of polymerization

for cellulosic fibers ....................... 11

Properties of rayon fibers .................. 13

Properties of nylon-6,6 and nylon-6

fiber ....................................... 17

Properties of olefin fibers ................. 2 0

Formation of acid coagulation bath .......... 36

Operating conditions of tensile test ........ 46

Formation of the dye solution ............... 5 0

Effect of pH of 2-6032/water solution

on the adhesion of rayon/PP fibers .......... 5 5

Effect of Z-6032/water solution

concentration on the adhesion of

rayon/PP fibers ............................. 59

Effect of pretreatment on rayon/

PP fibers ................................... 61

Effect of pretreatment on the

adhesion of rayon/nylon 6,6 fibers .......... 79

Effect of concentration of 2-6032

solution on tensile properties of

PP and rayon/PP fibers ...................... 91

B-2. Effect of pH of 2-6032 solution on

tensile properties of PP and rayon/

................................... PP fibers 92

B-3. Effect of water and 2-6032 solution

pretreatment on tensile properties

.......................... of rayon/PP fibers 93

....... B-4. Tensile properties of rayon/PP fibers 94

B-5. Effect of water pretreatment time

on tensile properties of nylon and

...................... rayon/nylon 6,6 fibers 95

B-6. Effect of water and 41-6106

pretreatment time on tensile

properties of nylon 6,6 and

..................... rayon/nylon 6,6 fibers 96

B-7. Effect of water and Q1-6106

solution pretreatment time on

tensile properties of rayon/

............................. nylon 6,6 fibers 97

FIGURES

Figure Page

1 . Side-by-Side type bicomponent fiber .......... 3

2 . Pictorial drawing showing the bilateral structure of a wool fiber .......... 3

3 . Sheath-Core type bicomponent fiber ............ 5

4 . Cross sectional view of a fiber coating die .................................. 5

5 . Matrix fiber ................................. 6

6 . Molecular structures of sodium ............. cellulose xanthate and cellulose 9

7 . Stress-strain curves of high-tenacity .................... and regular viscose rayon 12

........................ 8 . Formation of nylon 6. 6 15

.......................... . 9 Formation of nylon 6 15

10 . The hydrogen bonding of nylon 6 and .................................... nylon 6. 6 16

.............. . 11 The polymerize of polypropylene 19

......... . 12 Molecular structure of polypropylene 19

13 . Schematics of autohesion of simple .......................... liquids and polymer 24

14 . Structure of microscopic rootlike ..................................... cavities 27

. ............. 15 Principle of the pull-out method 30

16 . The microdeboding apparatus of ................................ pull-out test 31

Coupling agent solution

....................... pretreatment procedure 37

......... The new single fiber coating process 39

......... The old single fiber coating process 40

.................................... ~ c i d bath 41

The cross sectional view of

................. the single fiber coating die 43

Position of the fiber in the

die and in the acid bath ..................... 44

Effect of spin finish removal on

coating weight loss of rayon/PP

fibers ....................................... 54

Effect of pH of 2-6032 solution on

coating weight loss of rayon/PP

fibers ....................................... 56

Effect of concentration of 2-6032

solution on coating weight loss

........................... of rayon/PP fibers 58

Effect of water and coupling agent

pretreatment time on coating weight

...................... loss of rayon/PP fibers 60

Effect of 2-6032 solution and water

pretreatment time on coating weight

...................... loss of rayon/PP fibers 62

Photomicrograph of rayon/PP fibers

with water pretreatment for one hour ......... 65

VIII

29. Photomicrograph of rayon/PP fibers

......... with water pretreatment for 24 hours 66

30. Photomicrograph of rayon/PP fibers

with water pretreatment for one hour

and 2-6032 solution pretreatment for

................................... 52 seconds 68

31. Photomicrograph of rayon/PP fibers

with water pretreatment for one hour

and 2-6032 solution pretreatment for

............ 52 seconds (duplicate experiment) 6 9

32. Photomicrograph of rayon/PP fibers

with 2-6032 solution pretreatment

............................... for 51 seconds 70

3 3 . Effect of water pretreatment time

on coating weight loss of rayon/

............................. nylon 6,6 fibers 74

34. Effect of water pretreatment time

on coating weight loss of rayon/

nylon 6,6 fibers treated with coupling

agent 41-6106 solution for 22 sec ............ 75

35. Effect of concentration of 41-6106

solution on coating weight loss of

....................... rayon/nylon 6,6 fibers 77

3 6 . Photomicrograph of rayon/nylon 6,6

fibers with water pretreatment

for two hours ................................ 81

37. Photomicrograph of rayon/nylon 6,6

fibers with 41-6106 solution

pretreatment for 52 seconds .................. 82

38. Photomicrograph of rayon/nylon 6,6

fibers with no pretreatment .................. 83

1

CHAPTER I. INTRODUCTION

A new sheath/core type bicomponent fiber produced by

a coating process has been obtained at Ohio university,

which has both synthetic fiber mechanical properties and

natural fiber surface properties. The Sheath/Core (S/C)

fibers which were produced by the previous investigator

have the expected properties with the exception of the

durability of the coating. The coating could be dislodged

by finger touching (1,2,3,4) . ~t is necessary to improve the interfacial adhesion of the S/C fibers before they can

be used commercially.

The techniques of spin finish removal and coupling

agent solution pretreatment were used to improve the

interfacial adhesion of the fibers. Water as a solvent was

used to remove the spin finishes which were on the

synthetic fibers. This removal was done so that the

coating would have good contact with the core fibers to

improve the interfacial adhesion. Aqueous solutions of two

Dow Corning proprietary coupling agents, 2-6032, Specific

for polypropylene (PP), and Q1-6106, specific for nylon

were used to treat the core fibers. These agents form

chemical bonds or improve the interfacial compatibility

between the fiber layers, thereby promoting adhesion. The

durability of the coating was promoted by using those

pretreatment for rayon/PP and rayon/nylon 6,6 bicomponent

fibers.

CHAPTER 11. LITERATURE: REVIEW

A. Bicomponent Fibers

Fibers which are made of different polymers or

variants of the same polymer can be combined into a single

fiber in order to take advantage of the special

characteristics of each polymer such fibers are called

bicomponent or bicomponent bigeneric fibers (5).

Production of bicomponent fibers represent one of the new

techniques for producing man-made fibers so that some call

these kinds of fibers as "third-generation man-made

fibers1' (5) . A bicomponent fiber is defined by the American

Society for Testing and Materials (ASTM D-123) as: "a

fiber consisting of two polymers which are chemically

different , physically different , or both (6) . There are

two types of bicomponent fibers : side-by-side (S/S) type

and sheath-core (S/C) type. Side-by-side fibers are

produced by feeding the different polymers to the

spinneret orifice together so that they exit from the

spinneret opening side-by-side (Fig. 1) (5) . The structure of S/S bicomponent fiber is similar to that of the natural

fiber wool which is shown in Fig.2 (7). The characteristic

of this kind of fiber is its crimp due to the dissimilar

materials. The two components react differently to

moisture and other conditions resulting in differential

Fig.1 Side-by-Side type bicomponent f iber

PARA C M T E X

' WOOL FIBER I

Pictonal drawing showing the bilateral structure of ' a wool fiber.

4

shrinkage. There have been a number of fibers produced

with crimp induced by the side-by-side structural

differences ( 8 , 9 ) .

S/C fibers require that one component be completely

surrounded by the other. The polymer is generally fed into

the spinneret as shown in Fig. 3 (5) . S/C type fibers can also be made by a coating process (Fig.4) (1). The

externalproperties of S/C type fibers are offered by one

polymer and the internal properties are offered by another

polymer. Generally, the load will be carried by the core

material and the surface properties such as sorptivity and

dyeability will depend on the skin material. In this

project, S/C type bicomponent fibers were made by a

coating process in order to obtain fibers with good bulk

properties and good surface properties.

Bicomponent bigeneric fibers are defined by ASTM (D-

4466) (10) as fibers Blessentially a physical combination

or mixture of two or more chemically distinct constituents

or components combined at or prior to the time of

extrusion." This type of matrix fiber (M/F) is shown in

Fig.5 (11). Matrix fibers are formed by mixing two totally

different generic types of polymers together during or

just prior extrusion. These fibers have characteristics of

both materials.

Fig . 3 Sheath-Core type blcomponsnt f i b e r

DIE BOO! / LEIO PCTIDH /

FIBER

, coatinq

Flp.4 Cross sectional view of a f i b e r coating d i e

,droplets of /component B in 'component A !

~ i g . 5 Matrix f i b e r

B. Properties of Rayon, Nylon, and Polypropylene

(1) . Rayon Rayon has played an important part in the textile

industry since 1891. Rayon was the first commercially

successful man-made fiber. Although the fiber is man-made,

the raw materials which are used to make rayon still come

from natural sources.

The Federal Trade Commission (FTC) identifies rayon

as "a manufactured fiber composed of regenerated

cellulose, as well as manufactured fibers composed of

regenerated cellulose in which substitutes have replaced

not more than 15 per cent of the hydrogen of the hydroxyl

groups (5) . Several different rayon fibers have been

produced, with their differences dependent on processing

conditions.

Cuprammonium rayon made by dissolution of cellulose

in cuprammonium and subsequent extrusion into a water

bath,is no longer produced in the United States due to

environmental problem of copper ions in the water waste.

The other two rayon fibers, viscose rayon and high-wet-

modulus rayon, are made by the viscose process which is

discussed here (12).

The raw materials for viscose rayon are pure cotton

or wood cellulose, or the cellulose in any of the

vegetable fibers. In the manufacture, the cellulose is

steeped in an alkali solution to form soda cellulose with

a white color.

(C6H1005)n + n NaOH ----- (C6HgO5Na)n 4- n H20

cellulose caustic soda soda cellulose water

The soda cellulose is aged to reduce the molecular

weight of the cellulose and it is then treated with carbon

disulfide to produce sodium cellulose xanthate with bright

orange color.

soda cellulose carbon sodium cellulose disulf ide xanthate

The sodium cellulose is dissolved in dilute sodium

hydroxide to form a honey-color liquid which is called

viscose. The viscose is ripened to reach the proper

viscosity. In order to produce filament fibers, the

viscose is spun into an acid bath. The pure cellulose

within the viscose is coagulated by sulfuric acid (12,13).

sodium sulfuric cellulose carbon sodium cellulose acid (viscose disulfide sulfate xanthate (dilute) type rayon)

The molecular structures of sodium cellulose xanthate and

cellulose are shown in Fig.6 (12).

The acid bath generally contains sulfuric acid,

Sudium Cellulose Xanthate

n c-0 7-:\ ,n \ 4 \ /O\ /OH n

\ o \ C-C / \ j\r C -o O / I I n n I H on W H

Cellulose

Fig. 6 Molecular Structure of Sodium

Cellulose Xanthate and Cellulose

10

sodium sulfate, glucose, zinc, and water. Sulfuric acid is

used to regenerate cellulose from the viscose; sodium

sulfate is used to hasten the pre'cipitation of filaments;

glucose is added to improve the softness and pliability of

the filaments; zinc sulfate helps to decrease the serrated

cross section; and water is to provide the necessary

volume (12). The range of the concentrations for rayon

coagulating bath is shown in the Table 1 (1).

One of the disadvantages of viscose rayon is its poor

wet strength which discourages machine washing of rayon

fabrics. Consequently manufacturers have modified the

processing conditions to produce a viscose rayon fiber

with higher wet strength. This fiber, high wet modolus

(I-IWM) rayon, is produced by retaining a higher degree of

polymerization in the cellulose during the viscose

process than that of the general cellulose. Table 2 shows

the average degree of polymerization for cellulosic fibers

(12). HWM rayon has higher average molecular weight than

regular rayon giving it higher wet and dry strength (Fig.7

(14) , Table 3 (12) ) .

TABLE 1 Ranges o f Concent ra t ions f o r

Rayon Spinning Ba th

Weight Component Pe rcen t

S u l f u r i c Acid 7-10

Sodium S u l f a t e 12-18

Water 60-80

Zinc S u l f a t e 0- 1

Glucose 0- 4

TABLE 2 Average Degree of Polymerization (dp) for Cellulosic Fibeni

Fiber Degree of Polymerization

cotton 9,000-10,000 viscose rayon

regular 300-500 high- tenacity 400-600 high-wet-modulus 800-1,000

cuprammonium rayon 400-500 saponified cellulose rayon 500-700

- --

SOURCE: J . W. S. Hearle and R. H. Peters, Fiber Strudure (London: Bu~tenvorth k Co., 1963:1, p. 12.

Elongation ( ~ e r cent)

Fig. 7 Stress-strain curves of high-tenacity

and regular viscose rayon

TABLE 3 Properties of Rayon Fiben

V ~ s c o s e - Htgh Wet Property Regular ,Medtum H ~ g h Modulus Cuprarnmontum

shape

luster strength

in gpd dry wet

Elastic recoveryielongation percent of recovery at 2% extension % elongation

dry wet

resiliency density moisture absorption

20"Cl65% RH saturation

dimensional stability resistance to:

acids alkalies sunlight microorganisms insects

thermal reactions: to heat to flame

Shape can be controlled by the manufacturei Therefore, i t is uniform in appearance. Length and denier are determined by the manufacturer for the desired end use. Available in both filament and staple lengths. Diameter varies from 12 to 100 micrometers.

Can be controlled by the manufacturer-from dull to bright.

15-30 15-20 9-26 6.5-18 10-17 20-40 17-30 14-34 7-33 17-33 low low low low-medlum low

1.50-1.52 for all

10.7-16 (for all viscose types) 12.5 25- 27 (for all viscose types) 27.0

Poor poor poor good good

Resistance to concentrated acids is poor; to cold dilute acids, good Resistance to strong alkalies is poor; to weak, good. average for regular, medium, high good good Mildew will destroy the fiber. Silverfish wlll damage all types of rayons.

Exposure to high temperatures eventually degrades the fiber. AU types of rayon bum readily.

14

2. Nylon

Nylon was the first fiber to be synthesized from

materials none of which had previously been fibrous in

nature (16t17t18t19). ~ccording to the Federal Trade

Commission, nylon is "a manufactured fiber in which the

fiber-forming substance is a long-chain synthetic

polyamide in which less than 85 per cent of the amide (-C-

NH-) linkages are attached directly to two aromatic rings

I! (11) . Although a variety of structures is covered by

this definition, only nylon 6 and nylon 6,6 are produced

in this country.

In the manufacture of nylon 6,6 , hexamethylene

diamine and adipic acid are reacted to form nylon 6,6

salt. The salt is then polymerized under a certain

pressure and temperature to form nylon 6,6 (Fig.8) (20).

Nylon 6 is made by polymerizing caprolactam (Fig. 9) (20) . Hydrogen bonding can be formed between the molecules of

nylon (Fig.lO), which increases the degree of

crystallization giving nylon fibers higher tensile

properties. The properties of nylon fibers are shown in

Table 4 (12).

Comparing Table 3 with Table 4, nylon fibers have

very good strength and wrinkle resistance, whereas rayon

fibers are noted for surface properties such as moisture

sorption. A composite fiber could offer the advantage of

both. Therefore a coating process was designed to make a

H, NIGH,),-NH7 + HOOC-(CH, 1,--COOH - hexamethylene diam~ne a d ~ p ~ c ac~d

Hear H,N-(CH,),-NH; OOC-(CH, ),-COOH -----.)

nylon salt

water nylon 6.6

Fig. 8 Formation of nylon 6,6

caprolrtom nylon 6

Fig. 9 Formation of nylon 6

F i g . 10 The hydrogen bonding of n y l o n 6

and n y l o n 6 , 6

TABLE 4 Properties of Nylon 6,6, Nylon 6, and Qiana Fibers

Property

shape

luster strength, dry

wet e l a s t ~ c recovery elongatron dry

wet resil~ency density morsture absorp t~on

standard cond~t ions saturation

d ~ m e n s ~ o n a l s tab~li ty reslstance to:

acrds

alkal~es sunlight

reslstance to mlcrwrganrsms Insects

thermal reactrons to heat Ironing temperature to flame

Nylon 6.6 Nylon b;

Shape is controlled by the ma~iufacturer. Filaments are uniform In appear- ance; length and diameter are determined by the manufacturer for specl- fied types of end-uses.

Fiber is available in filament or staple length. F iben are translucent. Luster is controllable, from bright to dull 1.3-9.0 gpd 3 5-'9.0 gpd 4.0-7.6 gpd 3.2-8.0 gpd 1009'0 at 4% extension for all types 19-40% 16-50% 20-4670 18-55% good goodl 1.14 I 14

3 8-4.5% 8.09'0 excellent

3 5-!j OO/a 8 5% excellent

All nylon has poor reslstance to a c ~ d s Some m ~ n e r a l acrds, as well a s some organlc acids, drssolve nylon f~bers

Resistance of all nylons IS good Sunlight is destruct~ve to nylon f~bers unless spec~al f rn~shes have been

added

h1gh high resistant to most, may be darn,rged by ants. crickets, and roaches

All nylons wlll soften and eventually melt. 1 W C - 175°C 150°C Heat sensrtive; shnnk from flame, melt, drip, b u m In open flame; consid-

ered to be se l f -ex t lngu~sh~ng Some f l n ~ s h e s and dyestuffs may alter be- havior rn flame

18

rayon/nylon sheath-core bicomponent fiber. The advantages

of the bicomponent fiber have been evidenced by prior work

( 1 , 2 , 3 , 4 )

3.Polypropylene

Fibers composed of polyethylene or polypropylene are

defined as olefines. Polypropylene is made from propylene

by opening the double bonds in a chain growth

polymerization reaction in the presence of organometallic

catalysis (Fig. 11) (21) . In the formation of polypropylene, three different

stereochemical forms of the polymer are possible (Fig.12).

An atactic polymer is produced if methyl side chains are

randomly arranged on either side of the carbon backbone.

This polymer is not capable of the crystalline packing

necessary for fiber formation because of the irregular

occurrence of the bulky methyl groups. A more steroregular

polymer, termed syndiotactic, is formed if the methyl

groups lie alternately on each side of the carbon chain,

but crystalline packing is still somewhat inhibited. The

tightest packing of polymer chains is possible in the

isotactic form of polypropylene, where all the methyl

groups are on one side of the chain. This enables the

formation of crystalline areas which gives isotactic

polypropylene its fiber forming characteristics (19,20).

The properties of polypropylene fibers are listed in

I i I l l H t I H H H H H

t{-<-=c-tl I I I

I - C-C - C - i -c-i-i - C- - c -- - C t l , I I ' I I

C I i , H CH, H CH, H CH, H C H , I 1 1 I

p r t ) , l \ I L Y - I C pol\ prop),lene

Fig. 11 The polymerization of polypropylene

\

H\ /c<Cnl H y c \

C-CH, ,' 'H H,-,

\ C-CH,

H, / 'H

H y C , H,C-C-H

", ,, /

d C . \

l a ) Ib )

Fig. 12 Molecular structure of polypropylene

( a ) isotactic, (b) synditactic, (c) atactic

Table 5 . P r o p e r t i e s of O l e f i n F i b e r s

f'olyt,fhyler~e P o l y p ~ o p y l e r ~ ~

shape Contrilllcd t i u l ~ r i ~ ni'ini~l.lctirrt~. Iwt usually olcfiri fibcrs arc round luster Cnntrtdlo~1 . l ~ i d rn,i\. 1.c. h g h t tn dull strength 1.5-3 fl gpd fol- Ic>~~-pressurc 3.5-8.0 gpd,

4.0-7.0 gpd fnr high prcsslrre elastic recoven I()()%, at 2'Yo cx t t ,~~s ivn for both e l o ~ i g a t ~ o n 20- Fr71%t 15-50°i, r e s i l i r r i ~ good guod density 0.92-0.96 0 90-0,9 1 moisturc absorbency less tliari I % to1 i-(lth d~mens inna l stability if s t ab~l i t c t l , good resistdllce unlcs.; s r ~ l ~ j e c l c d to tcvnpcraturcs above 120°C resistance to:

acids exccllen t excellent alkalies excellcn t e ~ c e l l ~ n t o r ~ a r i i c solvents medium nicdlum sunlight s lo~vly degradc~c sIo\~.l! cjr,gr.idz~ rnic~.oorganisms good good insccts good g o l d

thermal reactions to heat shrinL a t 7j°C di r ink at 120°C'

n d t .it low te11iperatu1-e nit.lt a t 170°C' to flame both f ~ b r r s burn and emit hcav!,, sooty. \vary snioke

21

Table 5 (20).

Polypropylene fibers have high strength and wrinkle

resistance, but poor dyeability and absorptivity.

Therefore polypropylene is another choice as a core

material of the rayon coated fibers.

C. Spin Finish

Spin finishes, also called spinning finishes,

dressings, treating agents, spinning lubricants, coatings,

fiber finishes, processing agents, textile treating

agents, textile treating compositions, and conditioning

agents, are antistatic lubricants applied to the surface

of man-made fibers as soon as practical after formation

(22). The purpose of addition of a spin finish is to

reduce the friction and the static electrical charges

between the filaments and processing equipment. Natural

fibers, such as cotton and wool, do not require spin

finishes because they have cotton wax or wool wax on their

surfaces enabling them to be processed on carding and

spinning equipment. However man-made fibers do not have

this inherent surface property so they cannot be processed

without spin finishes (22,23) . Spin finishes usually consist of a lubricating

ingredient to reduce friction, an antistatic agent to

reduce the static electrical charges on the surface of the

yarn during the processing, an antioxidant or thermal

22

stabilizing agent to promote the thennostability of the

fibers, and an emulsifying agent to form an aqueous

emulsion (24). The lubricants may be fatty acid esters,

white mineral oils, and or other synthetic lubricants. The

antistatic agents are mostly long chain alkyl or aralkyl

compounds of the non-ionic anionic or cationic type.

Different kinds of spin finishes should be used for

different kinds of fibers. However, spin finishes should

have good solubility, i.e. they should easily be

completely removed from the fibers under mild scouring

conditions before application of dye or another finish to

the textile. Incomplete removal of a spin finish can cause

dyeing problems and potential soiling spots in the final

fabric. Use of a selfmulsifiable type of lubricant and

addition of an emulsifier assure the easy removal of the

spin finish by water or other chemicals under mild washing

conditions ( 2 3 ) .

D. Interfacial adhesion

Adhesion occurs when two dissimilar bodies are held

together by intimate interfacial contact so that

mechanical force or work can be transferred across the

interface. The interfacial forces can be formed by van der

Waals forces, chemical bonding, or electrostatic

attraction (25) .

23

There are three kinds of adhesion: thermodynamic

adhesion, chemical adhesion, and mechanical adhesion.

Thermodynamic adhesion refers to equilibrium interfacial

forces or energies associated with reversible processes.

Chemical adhesion involves chemical bonding at the

interface. Mechanical adhesion arises from microscopic

mechanical interlocking which is over substantial portions

of the interface (25).

In order to obtain good interfacial adhesion, it is

necessary to form an adhesive bond between the materials.

This involves first the establishment of interfacial

molecular contact by wetting. The molecules will then

undergo motions toward preferred configurations to achieve

an adsorptive equilibrium, diffuse across the interface to

f orm a diffuse interfacial zone, and/or react chemically

to form primary chemical bonds across the interface (25).

During the S/C type bicomponent fiber development the

previous workers considered using the autohesion property

of polymers. When two phases attain molecular contact by

wetting, segments of the macromolecules will diffuse

across the interface to some extent (Fig. 13) (26) . For

simple liquids, wetting and diffusion occur

simultaneously, and the interface disappears

instantaneously upon interfacial contact. For polymers,

autohesion is a two stage process; wetting is followed by

interdiffusion. The autohesion will be complete only after

Fig.13 Schematics of autohesion of simple

liquids (top) and polymer (bottom)

2 5

extensive interdiffusion of chain segments across the

interface to reestablish the entangled network. Although,

interdiffusion coefficients for polymers are very small,

some local segmental diffusion still can occur to form a

diffuse interfacial layer of 10--1000 between two

incompatible polymers. Suitable temperature and pressure

conditions are required for this autohesion. A previous

worker used a coextrusion process to produce nylon 6 core

and rayon skin bicomponent fiber. However this process was

not viable as the temperature required for extrusion of

the core material exceeded the thermal stability of the

rayon viscose used to form the skin (27). Therefore the

fiber coating process as described above was used for the

rayon/nylon bicomponent fibers. However, since skin and

core are not formed at the same time there is less

opportunity for interdiffusion of the polymers, and

adhesion between skin and core was not satisfactory.

To solve the durability problem, the spin finish

should be removed from the uncoated fiber so that the core

material would have better contact with the coating and

improve the thermodynamic adhesion. Modh (3) and McDonald

(28) tried to improve the interfacial adhesion of

rayon/nylon fibers by passing the nylon fiber through an

acid bath and subsequent bleach rinse to remove the spin

finish. This was not sufficient, however because either

the spin finish was not completely removed by that method

26

or the thermodynamic adhesion between the two materials

was not strong enough. If thermodynamic adhesion is not

strong enough to hold the core material and the skin

material together, chemical adhesion and mechanical

adhesion methods should be considered.

Mechanical adhesion refers to the formation of

micromechanical interlocking which can produce strong

adhesive bonds resistant to hydrolytic and thermal

degradation. The adherent surface must have sufficient

numbers of microscopic undercutting or rootlike cavities

(Fig.14) (24).

Chemical adhesion refers to forming interfacial

chemical bonding which can increase the adhesive bond

strength by both preventing molecular slippage at a sharp

interface (which has little or no interfacial diffusion

occurring) during fracture and increasing the fracture

energy by increasing the interfacial attraction. Chemical

adhesion can be obtained by inserting small amounts of

adhesion promoting functional groups or using coupling

agents (25,29,30).

E. Coupling Agents

Coupling agents are several classes of compounds

which can promote adhesion apparently by chemically

coupling the adhesive to the adherents (31). Generally, a

S u r f a c e t o p o g r a p h y of c o p p e r foil Pecl s t r e n g t h , g lcm

Flat 670

0.3-u m d e n d r i t e s

0. 3 - D m d e n d r i t e s - + oxides -

3- v m Pyramids w 2- urn Low hills +

0 .3- IJ m d e n d r i t e s

2 - L m Lorv hills +

0 . 3 - ;l m d e n d r i t e s + o x i d e s

- 3 - s m Pyramids +

0. 3- ;. m d e n d r i t e s + o x i d e s

Nickel foil with k n o b b e d nodules

Fig. 14 Structure of microscopic rootlike cavities

28

coupling agent has two different functional groups, one

which can react with the adhesive, and another which

reacts with the adherent. If those actions occur, the

coupling agent may act as a bridge to bond the two

materials together with a chain of primary bonds. This

could be expected to lead to the strongest interfacial

bond (30).

Organosilanes are used as coupling agents for resin

and glass, and have the general structure R--Si--X. The X

is a hydrolyzable group such as an alkoxy group or

chlorine. It can hydrolyze to silanol groups and then

react with the silanol groups on the glass surface to form

ether linkages. The R is an alkyl or a functional alkyl

group, which can react with appropriate chemical groups in

the resin (25). Therefore the resin and the glass are

chemically coupled together.

Generally, if a coupling agent has a nonreactive

functional group, it will not promote adhesion (32).

However, in some cases, coupling agents can promote

adhesion by improving interfacial compatibility (33). It

is expected to promote the interfacial adhesion of the

experimental rayon coated fibers described above by using

coupling agents to form chemical bonding and/or improve

the interfacial compatibility between the core material

and the skin material.

29

F. Interfacial Adhesion Test

There are several methods to test interfacial

adhesion properties of coated fibers. The general method

is the coating pull-out test (34,35,36,37,38). A single

fiber pull-out technique is shown in Fig.15 (34).

Fig.lS(a) illustrates the Shiriajeva method for a small

fiber-resin seam. There are two small diameter glass rods

supporting the resin. When the resin is cured, the fiber

is cut on one side of the seam. The other end is then

loaded in tension until it is pulled out (35). For a

thinner and more fragile fiber, a Duraluminum ring is used

instead of the glass rods (Fig.15 (b) ) (34). Adhesion

strength is measured as following:

Adhesion Strength = F/ (Z*d*l)

where: F is the force required for pull-out.

d is the diameter of the fiber.

1 is the length of the withdrawn fiber.

Another single fiber pull-out technique is shown in

Fig.16 (36). The fiber with coating beads attached is hung

on load cell hook. The debonding blades are adjusted to

touch the fiber. The blades are then translated by a

positioning motor to the position of the beads. The force

required to pull off the beads is measured (36). A higher

force indicates better interfacial adhesion.

Because those kinds of instrument are not available

in the lab and the rayon coating requires acid for

Fig . 15 P r i n c i p l e of t h e p u l l - o u t method

(a ) S h i r i a j e v a ; (b ) modif ied f o r

carbon f i b e r s .

u u -,

1. d i a l indicator 4 . sonp l e 7. translat ion stage

2 . fast dr ive motor 5 . tronslable blade 8 . optoelectronic l i m i t sensor / 3 h o o k f r o n l a a d c e I l 6 . f i r e d b l o d e - 9 . slow dr ive motor

F i g . 16 The microdeboding a p p a r a t u s of p u l l - o u t t e s t

coagulation, another method was found to measure

interfacial adhesion.

The Ameraican Assiociation of Textile Chemists and

Colorists (AATCC) Accelerator is used to test abrasion

resistance of fabrics under standard AATCC method 93-1984

"In this test an unfettered fabric specimen is driven by an impeller (rotor) along a zigzag course in a generally circular orbit within a cylindrical chamber, so that it repeatedly impinges on the walls and abradant liner of the chamber while at the same time being continually subjected to extremely rapid, high velocity impacts, subjected to flexing, rubbing, shock, compression, stretching and other mechanical forces in the cyl indrica 1 corklined chamber. Abrasion is produced throughout the specimen by rubbing of fiber against fiber, surface against surface, and surface against abradant. Evaluation is made on the basis of weight loss of the specimen. (39)

The test condition is harsh enough to take the

coating off the composite fibers. If the test does not

cause any damage to the core materials, the method could

be used to measure the durability of the coated fibers

because all of the weight loss would be due to loss of

coating.

CHAPTER 111. EXPERIMENTAL

The experimental materials, equipment, fiber

pretreatment methods, coating procedure, as well as

methods for determination of fiber properties are

described in this section.

A. Materials and Equipment

The following is a list of materials and equipment

which were used for this project.

MATERIALS :

1. High wet modulus viscose rayon solution, supplied by

Avtex Incorporated.

2. 101.6 micron diameter nylon 6 monofilament, supplied

by Allied Chemicals.

3. 105.7 micron diameter polypropylene (PP) monofilament,

supplied by Allied Chemicals.

4. 98% reagent ACS sulfuric acid, purchased from Fisher

Scientific.

5 . Anhydrous sodium sulfate, low in nitrogen, purchased

from Fisher Scientific.

6. ACS methylene chloride, purchased from Fisher

Scientific.

7. Glacial acetic acid, purchased from Fisher scientific.

8. 41--6106 adhesion promoter, supplied by Dow Corning

Corporation.

9. 2--6032 silane adhesion promoter, supplied by Dow

3 4

Corning Corporation.

10. Distilled water, supplied by the Ohio University

Polymer Lab.

11. Dye, Solophenyl red 3BL, purchased from Dyestuffs and

Chemicals Division CIBA-GEIGY Corporation.

12. Sodium Chloride U.S.P., purchased from Fisher.

13. Dry nitrogen gas, cylinder with Fisher Scientific

0-28000 KPa, flow control, purchased from AGA company.

14. Plastic cones with 3'51' angle and 170 mm length

donated by Textube.

15. FISHERbrand microscope slides, purchased from Fisher.

16. FISHERbrand disposable cover slips, purchased from

Fisher.

EQUIPMENT

1. 500 ml Pyrex separator funnel with stop cock and one

hole stopper.

2. Fiber coating die, manufactured by Ohio University

Physics shop and DuPont, with an additional 1/74"

diameter land section machined by the College

technical staff.

3. 3 inch diameter 60 inch and 70 inch length Pyrex glass

tubes.

4. 3 inch diameter 12*12 inch Pyrex glass breach tubes.

5. 3 inch Pyrex glass tube seals.

6. Take up mechanism with transverse.

7. Stainless steel tank with the inside dimensions

20*11.75*8 inches.

8. Instron TTD tensile tester.

9. DuPont 951 Thermogravimeteric Analyzer.

10. Accelerotor, AATCC standard instrument.

11. Wild M5A microscope.

12. Pressure transducer, Omega PX931-025GV.

13. Pressure meter, Omega DP350.

B. Fiber Pretreatment Procedure

In order to promote the interfacial adhesion

properties of coated fiber, it is necessary to improve the

surface properties of the uncoated fiber. One of the

method to accomplish this is removal of the spin finish

from the uncoated fiber. If sufficient interfacial

adhesion were still not achieved, a coupling agent would

be used to pretreat the fibers. The methods employed to

remove the spin finish and pretreat the fiber with a

coupling agent are described below.

1. Removal of Spin Finish

Spin finishes generally are water soluble and should

be easily removed under mild washing conditions (23,24).

Therefore distilled water was chosen as a solvent. This

pretreatment included the following steps: First, the

uncoated fiber from a large fiber spool was rewound onto

small fiber cones. Then the fiber cones were immersed in

distilled water for 1, 2, 4, 6, 10, or 24 hours. The cones

36

were removed from the water and washed with distilled

water for one to two minutes. They were then left to dry

at room temperature for several hours.

2. coupling agent pretreatment

The coupling agent/water solutions were prepared in

three different concentrations (appendices A-1). Two glass

guides were set in a 500 ml or 1000 ml beaker in order to

obtain a longer residence time of the fiber in the

solutions. The fiber was passed around the guides then

linked to the take up (Fig.17). The pretreatment time,

i.e. the residence time of the fiber in the coupling agent

solution, was calculated by the take up speed and the

total length of the fiber passing the solution.

C. Fiber Coating Procedure

The coagulation bath for the fiber coating process

was prepared according to the formulation shown in Table

6.

Table 6. Formulation of acid coagulation bath

Chemicals Amount

Sulfuric Acid

Sodium Sulfate

Distilled Water

To take

Fig.17 Coupling agent solution pretreatment p r o c e s s

38

Eighteen liters of distilled water were placed in the

stainless steel tank, and 1.135 L of sulfuric acid were

added very slowly. After 10 minutes, 3000 g sodium sulfate

was added. It was necessary to stir the solution

continuously in order to dissolve the sodium sulfate

completely. The acid solution was stored in the tank until

ready for use.

The fiber coating apparatus was assembled as shown in

Fig. 18 for a single fiber coating process. There are

several differences between this apparatus and that used

by a former researcher (Fig.19) (1,2,3,4). The

predominant difference is the structure of the acid bath.

This new acid bath consists of nine parts: a 3 inch

diameter and 70 inch length glass tube, two 3 inch

diameter and 6*12 inch branch glass tubes, four 3 inch

tube seals, and two 3 inch diameter and 1/8 inch thick

polyethylene plates with a 1/16 inch hole in the center

(Fig.20). The bath was altered to give the fiber a longer

residence time before reaching any guide, and so prevent

peeling of coating areas which were not fully regenerated.

The new acid bath has a strict structure. There are no

guides in the bath so that the viscose rayon could be

solidified in the bath before touching any other surfaces.

Another difference is the addition of a pressure

transducer linked to the die enabling the feed pressure in

the die to be measured during the coating process. In

ffl ill

(I]

U (I] m ri :--a aJ CL

m

aJ e 1 U

(I] -/ V) m 4 C3

-.

ri a

42

addition, the bleach bath used in other work was omitted

because there had been no significant effect of this

treatment on the properties of the coated fiber except

whitening. The single fiber coating die previously used

was retained (Fig.21).

The fiber coating equipment was assembled in the

following manner (Fig.18). The filament core was threaded

through the die, the acid bath, the drying tube, and then

linked to the take up. Before addition of the acid

solution to the acid bath, the take up was started to

assure that the fiber could move in the system smoothly

and that the die was positioned correctly in order for the

fiber to pass through the center of the holes of the

plastic plates which were at the ends of the acid bath

(Fig.22) . The latter was done by adjusting the end of the acid bath nearest the die then leveling the acid bath. The

fiber would then be in the center of the holes.

After the fiber was set in the system, the acid

solution was added to the bath. The wash water, dryer, and

the take up were started, the viscose reservoir was opened

and the nitrogen cylinder opened and set at the selected

feed pressure. As the filament passed through the die, the

viscose rayon surrounded and coated its surface. When the

coated fiber passed through the acid bath, the cellulose

was regenerated from the viscose, forming a solid rayon

coating. Then the coated fiber was washed with water to

Fig. 21 The cross sectional view of the single

fiber coating die.

45

remove any remaining acid. The fiber was then dried by

warm air and wound on the take up.

D. Fiber Analysis and Testing

Fiber analysis and testing included linear density,

tensile properties, interfacial adhesion, and surface

properties.

1. Linear Density

The linear density of the fibers was measured with a

duPont 951 Thermogravimeteric Analyzer according to ASTM

D-1577 Standard Test Method of Linear Density of Textile

Fibers (33). A fiber skein was prepared by wrapping a 2

meter length of fiber around a 5/8 inch diameter bottle,

removing the coil from the bottle, then wrapping the end

of the fiber length around the coil and tieing the ends.

Five skeins of each sample were prepared.

Before the test, the samples were kept at 70°F and

65% relative humidity for 72 hours. A skein was weighed on

the ~hermogravimetric Analyzer, and linear density

calculated according to the equation:

Average linear density (dtex) = W/(L*n)

Where: W is weight of bundle, mg.

L is length of the fiber, m.

n is number of fibers in the bundle.

46

2 . Tensile Properties

The tensile properties of the fibers were measured

with an Instron model TTD constant-rate-of extension

tensile tester according to ASTM 3822-82 Standard Test

Method of Tensile Properties of Single Textile Fibers

(10). The tests were made with a 200 pound load cell and

pneumatic fiber grips controlled by a Hercules Air-Val

foot controller and Campell-Hausfied 3/4 HP compressor.

Table 7 . shows the operating conditions of the tensile

tester.

Table 7 . The Operating Conditions of Tensile Test

Instron crosshead speed 5 in/min

Chart speed 12 in/min

Gage length 5 in

Recorder pen travel 100 g/in

The fiber samples were kept at 70°F and 65% relative

humidity for 7 2 hours before the test. For each sample,

the test was repeated five times and the average values

for tenacity, breaking elongation, and modulus reported.

Tenacity is defined by ASTM as: the tensile stress

expressed as force per unit linear density of the

unstrained specimen (lo), and is calculated by:

~reaking tenacity (gf/tex) = M /T

Where: M is breaking load, in grams-force.

T is linear density, in tex.

Elongation at the breaking load is defined by ASTM

as: the elongation corresponding to the maximum load (lo),

and is calculated by:

Elongation at the breaking load ( % ) = 100 B / C

Where: B is the fiber elongation, cm.

C is the calculated effective specimen

length,cm.

Initial Modulus is defined by ASTM as: the slope of

the initial straight portion of a stress-strain curve

(10)

3. Interfacial Adhesion

The Accelerotor test method was used to mesure the

interfacial adhesion of the S/C fibers. Preliminary

experiments demonstrated that the uncoated PP and nylon

fibers did not have any weight loss under the test

conditions of up to 3000 rpm for 4 minutes. Therefore, at

the same test condition, any weight loss in the coated

fibers is assumed to be due to coating loss. Speeds higher

than 3000 rpm were not feasible as the fiber samples

became entangled. It was possible in the preliminary test

to distinguish coating abrasion (inherent weight loss)

from coating debonding (coherent weight loss). Inherent

48

abrasion was identified by a powdery residue from the

coating after abrasion and a skin layer that was still

continuous and fairly even. This indicates that

interfacial adhesion between skin and core is sufficient

to hold the two components together, but the abrasion

resistance of the skin material is insufficient to prevent

gradual reduction in the skin thickness. In the case of

coherent adhesion , however the lost coating fibrillated and came away from the core in strips. After the test the

remaining coating was not even. Under the same conditions,

the weight loss for these samples was generally of the

latter tape. The coherent adhesion between the skin and

the core materials was weaker than the inherent adhesion

of the skin and the skin was sloughed off rather than

being gradually abraded. Consequently, the Accelerator

method was considered to be an indirect measure of the

interfacial adhesion properties of the composite fibers.

a. Sample Preparation

Two meters of fiber were used to make a skein which

was first used for determination of linear density. For

each test, five skeins were prepared. The skeins were

conditioned for 72 hours at 70°F and 65% relative humility

before testing.

b. Test Procedure

First, the five skeins are weighed together to

49

+0.0001 g on an analytical balance. Then the five skeins -

were placed in the Accelerotor and the door locked. The

Accelerotor and timer were started and the speed held to

+lo0 rpm for the desired time. The test speed (2000-3000 -

rpm) and time (2-4 min) depended on the samples. The

Accelerotor was stopped at the end of test period and the

samples removed. The skeins were then reweighed on the

analytical balance to +0.0001 g.

c. Calculation

The coating loss per cent is given by:

E % = (B-C)/(B-A) *%

Where: A is the weight of five uncoated fiber skeins (g).

B is the weight of five coated fiber skeins before

the Accelerotor test (g).

C is the weight of five coated fiber skeins after

the Accelerotor test (g).

Lower values of E indicate less coating loss, and

better adhesion.

4. Surface Properties

a. Dyeability

Nylon, PP, and rayon have different dyeabilities and

the color differences can be noted by the eye, and also by

the colorimeter. The coating on the fiber sometimes is so

thin that it is difficult to see. In order to confirm the

50

presence of the coating, the coated and uncoated fibers

were dyed and the color differences observed.

The formulation of the dye solution is shown in the

table 8. The dyeing procedure was:

1). 150 ml dye solution was placed in a 250 ml beaker

and the samples were added.

2). The solution was heated to 100°C and kept at this

temperature for 15 to 20 minutes.

3). The samples are removed from the solution and

dried on paper towels.

Table 8. Formation of the dye solution

Composition Amount

Dye

NaCl

Distilled Water

b. Microscopic Observation

The surface of the fibers was observed using a Wild

M5A stereomicroscope with attached Wild MPS15 semiphotomat

and interchangeable 35 mm magazine loaded with Kodak Tri-X

Pan 400 speed film.

Samples were prepared for microscopic evaluation by

placing them on a precleaned microscope slide with double

51

ystick tape. A disposable cover slip was used to cover the

samples and was held in place by the tape.

52 CHAPTER IV RESULTS AND DISCUSSION

The purpose of this project was to promote the

interfacial adhesion properties of coated fibers in order

to improve the durability of the coating. The

investigation includes spin finish removal and coupling

agent pretreatment. Water as a solvent was used to remove

the spin finish on the uncoated fibers. Two different

coupling agents recommended by Dow Corning Corporation

were used: 41-6106 for rayon/nylon fibers and 2-6032 for

rayon/polypropylene fibers.

A. Rayon / Polypropylene Bicomponent Fiber

For rayon/polypropylene sheath/core bicomponent

fibers, rayon is the coating material and polypropylene is

the core material. The pretreatment was applied to the

polypropylene core fiber. The effects of both the spin

finish removal and the coupling agent solution

pretreatment on the interfacial adhesion, tensile, and

surface properties of the S/C fibers were investigated.

1. ~nterfacial Adhesion

The interfacial adhesion property was measured by the

Accelerotor test (39). It was assumed that higher

interfacial adhesion would result in lower coating weight

loss in this test.

53

a. Effect of spin finish removal

Water and methylene chloride as solvents were used to

remove the spin finish from the polypropylene fibers for a

pretreatment time of 24 hours. The pretreated fibers, as

well as untreated fibers, were coated under the same

process conditions. Results of the Accelerotor test on the

coated fibers are shown in the Fig.23. There was much less

coating lost for the fibers pretreated for removal of the

spin finish than for untreated fibers. This indicates that

the spin finish did indeed reduce the interfacial adhesion

of the S/C fibers and its removal promoted adhesion

between the core and the coating. The results also show

that the two solvents have different effects on removal of

the spin finish. Although use of methylene chloride shows

better adhesion results than use of water does, water was

still considered to be the preferred solvent because of

its much lower cost and much higher degree of safety. As

is shown below, water pretreatment gave superior results

at selected pretreatment times.

b. Effect of pH of the Coupling Solutions

The pH of the coupling solutions has been shown to

affect the properties of the pretreated materials (30,40).

This effect was determined for the bicomponent fiber in

this work. Polypropylene fibers were pretreated with water

for 24 hours to remove the spin finish. Aqueous solutions

Coating weight l o s s (2 )

None H2° C H 2 C 1 2

Spin f i n i s h removal s o l v e n t

F ig . 23 E f f e c t of s p i n f i n i s h removal on c o a t i n g

weight l o s s of rayon/PP f i b e r s .

of coupling agent 2-6032 (0.5%) were prepared and adjusted

to pH levels 3.5, 4.0, 4.5, and 5.0. Core fibers were

pretreated with these solutions for 22 seconds. The fibers

were coated at 25.6 m/min with a viscose feed pressure of

1.17 atm. Fig.24 and Table 9 show the Accelerotor test

results for the pH effect. The pH of the pretreatment

solution did have an effect on the interfacial adhesion

for the S/C fibers. At a solution concentration of 0.5%, a

minimum loss of fiber coating was obtained at a pH of 4.0.

Table 9. Effect of pH of 2-6032/water solution on the adhesion of rayon/PP fibers *

PH Coating Coating weight weight (g) loss (%)

* Pretreated with water for 24 hours and with 0.5% 2-6032 for 22 seconds.

c. Effect of the concentration of the coupling solutions

Polypropylene fibers were pretreated with water for

24 hours to remove the spin finish and then pretreated

pH o f 2-6032 s o l u t i o n

Coa t ing weight l o s s (%)

1C)O

86

60

40

2 0

0 .

Fig.24 E f f e c t of pH o f 2-6032 s o l u t i o n on c o a t i n g

weight l o s s of rayonIPP f i b e r s .

-

-

-

-

- . I I I I

3.0 3 . 5 4.0 4 . 5 5 .0

57

with 0.25%, 0.5%, and 0.75% 2-6032/water solutions at a

constant pH of 4.0 for 22 seconds. The fibers were coated

at 1.17 atm feed pressure and 25.6 m/min take up speed.

Fig.25 shows the Accelerotor test results for the

concentration effect. The 0.5% 2-6032/water solution

pretreated sample exhibited better results than the other

concentrations. Table 10 shows that at the same

pretreatment and coating conditions, the sample treated

with the 0.25% 2-6032 solution had a lower coating weight.

Perhaps the coating for these fibers was so unstable that

much of it was lost during the coating process, when the

freshly coated fiber passed the guides or during the take

up step. This type of behavior also occurred in samples

with no pretreatment. Evidently the 0.25% concentration

of the 2-6032 solution was too low to improve the

interfacial adhesion for the S/C fibers over untreated

fibers. However, the higher 0.75% concentration gave poor

results as well. The reason may be that pH 4.0 may not be

a suitable condition for the 0.75% solution since pH has a

significant effect on adhesion. Although it is possible to

find a suitable pH for 0.75% solution, the 0.5%

concentration is recommended because the concentration

should be as low as possible for economic reasons.

The results of this series of experiments indicate

that the spin finish should be removed before fiber

coating and the concentration and pH of the coupling agent

0.25 0.5 0.75

Concentration of 2-6032 solution (%)

Coating weight loss (%)

60

Fig.25 Effect of concentration of 2-6032 solution on

coating weight loss of rayon/PP fibers.

I

-

20 -

0. I I

59

solutions do have apparent effects on the interfacial

adhesion of the S/C fibers. Under these experimental

conditions 0.5% concentration of the coupling agent Z-

6032 at pH 4.0 is recommended for PP fiber pretreatment.

Table 10. Effect of Z-6032/water solution concentration on the adhesion of rayon/PP fiber *

Concentration Coating Coating weight of the solution weight (g) loss (%)

* Pretreated with water for 24 hours and Z-6032/water solution (pH 4.0) for 22 seconds.

d. Effect of water pretreatment time

Polypropylene fibers were pretreated with distilled

water for 1, 6, or 24 hours and were then treated with a

0.5% Z-6032/water solution at pH 4.0. The fibers were

coated under the coating conditions described above. The

effect of water pretreatment time on the interfacial

adhesion of the coated fibers is shown in Fig.26. The

samples pretreated in water for one hour exhibited better

interfacial adhesion than those treated for longer time.

2-6032 solution pretreatment time isec)

Coating weight loss (%)

100

Fig.26 Effect of water and coupling agent pretreatment

time on coating weight loss of rayon/PP.

-

water(24hr)

80 -

60 -

40 -

I

44. 22. 0.

61

Therefore increasing the water treating time was not

helpful in improving the interfacial adhesion. However,

the interfacial adhesion for all the water pretreated

samples was better than those with no pretreatment.

Therefore, removal of the spin finish does promote

interfacial adhesion in the S/C fibers.

e. Effect of Coupling Agent Pretreatment Time

The effect of the coupling solution pretreatment time

is shown in Fig.27. The interfacial adhesion of the

coupling solution pretreated samples is better than that

of unpretreated samples; further the longer the

pretreatment in the coupling solution, the less coating is

lost from the fibers. Samples pretreated with both water

and the coupling solution exhibited better interfacial

adhesion than those treated only with the coupling

solution (Table 11) . Therefore the short water washing

time and the longer coupling solution pretreatment time

are recommended.

Table 11. Effect of pretreatment on rayon/PP fibers *

Water treat 2-6032 solution Coating weight time (hr) treat time (s) loss (%)

* 0.5% 2-6032 solution at pH 4.0.

Water pretreatment time (hr)

Coating weight loss (%)

100

80

6 0

40

2o

0.

Fig. 27

-

-

2-6032 (0. SCC) -

-

/ 2-6032 (22 set) -- 2-6032 (44 sec)

I I I I I

Effect of 2-6032 solution and water pretreatment

time on coating weight lose of rayon/PP fibers.

0. 5 10 15 2 0 2 5

63 2. Tensile Properties

The tensile properties, such as breaking tenacity,

initial modulus and elongation at the breaking load, were

measured for both coated and uncoated fibers.

a. Effect of the Coupling Solution Concentration

The concentration of Z-6032/water solutions had the

same effect on both coated and uncoated fibers. The linear

density of the samples was slight increased with higher

concentrations. Although the breaking tenacity was not

affected, the initial modulus decreased with increasing

concentration of coupling agent. The breaking elongation

had a maximum value at 0.5%. (App.Bl).

b. Effect of pH of the Coupling Agent Solutions

For both the coated and the uncoated samples, there

was not much difference in the linear density, the

breaking tenacity, the initial modulus, and breaking

elongation over a coupling agent solution pH range of 3.5

to 5.0 (App.B2).

c. Effect of the Pretreatment Time

There was no apparent effect on the tensile

properties of the coated fibers with the different water

pretreatment times. However, increasing the coupling

agent pretreatment time from 22 sec to 4 4 sec increased

the linear density, without apparently affecting the

breaking tenacity and the elongation (App. B 3 ) .

d. Summary of Pretreatment Effects on Tensile

Properties

The S/C fiber samples with water washing for one hour

and treatment with a 0 . 5 % solution of coupling agent at pH

4.0 for 52 seconds exhibited the best interfacial

adhesion, while maintaining tensile properties similar to

the original rayon/pp fibers (App. B4) .

3. Qualitative Observation

a. Microscopical observation

The surface of -both coated and uncoated fibers was

observed under a Wild stereomicroscope and

photomicrographs obtained. Each photograph contains three

samples for comparison. At the top is an uncoated fiber

which has undergone the same pretreatment conditions as

the others. In the middle is the coated fiber before

Accelerotor abrasion, At the bottom is the coated fiber

and after the Accelerotor test. The uncoated samples have

a very smooth surface and are thinner than the coated

ones, and are therefore distinguishable.

Figures 28 and 29 show the photomicrograph of the

rayon/PP fiber pretreated in water for one hour (Fig.28)

and 24 hours (Fig.29). There was a little coating

Fig.28 Rayon/PP fibers with water pretreatment for

one hour. (a) uncoated; (b) coated but

not abraded; ( c ) coated and abraded in

Accelerotor . ( 7 0 X )

F i g . 2 9 ~ a ~ o n / P P fibers with water pretreatment for

24 hours. (a) uncoated; (b) coated but

not abraded; (c) coated and abraded in

Accelerotor. (70x1

67

remaining on the fibers after the Accelerotor test for

both pretreatment times. This demonstrates that only

removal of the spin finish was not sufficient to promote

the durability of the coating of rayon/PP fibers. ~igures

30 and 31 show the photomicrographs from duplicate

experiments of rayon/PP fibers pretreated in water for one

hour and in 2-6032 solution for 52 seconds. The fibers

maintained their even coating on the surface even after

abrasion in the Accelerotor. Calculation of per cent

weight loss during Accelerotor abrasion confirms these

results of the integrity of the skin. Fig.32 shows the

rayon/PP fibers pretreated with only the 2-6032 solution

pretreated for 52 seconds. More coating was retained on

the fiber than in the case of the water pretreated samples

but less coating remained than for those pretreated with

both water and coupling agent 2-6032. Therefore. for

rayon/PP fibers, it is necessary to pretreat the PP fibers

with both water and the coupling solution.

b. Dyeability

Both the PP core fibers and the rayon/PP fibers with

water pretreatment for 1 hour and 2-6032 solution

pretreatment for 52 sac were dyed in 100 OC red dye

solution for 20 min. The PP fiber exhibited no color

change. However the rayon/PP fibers was colored red color,

Fig.30 Rayon/PP fibers with water pretreatment for

one hour and Z-6032/water solution pretreatment

for 52 seconds. (a) uncoated; (b) coated but

not abraded; (c) coated and abraded in

Accelerotor. (70x1

Fig.31 Rayon/PP fibers with water pretreatment for one

hour and Z-6032lwater solution pretreatment

for 52 seconds. (Duplicate experiment)

(a) uncoated; (b) coated but not abraded;

(c) coated and abraded in Accelerotor. (70X)

Fig.32 Rayon/PP fibers with Z-6032/water solution

pretreatment for 52 seconds. (a) uncoated;

(b) coated but not abraded; (c) coated and

abraded in Accelerotor. (70x1

7 1

which means t h a t t h e r e is an even rayon coa t ing on t h e

rayon/PP f i b e r , even though t h e coat ing is very t h i n .

7 2

B. Rayon / Nylon 6,6 ~icomponent Fibers

Like other synthetic fibers, nylon is usually

produced with a surface spin finish, which reduces

interfacial adhesion in the rayon/nylon S/C fibers

(1,2,3, ) . Efforts had been made to remove the spin finish by passing the nylon fiber through a acid bath and

subsequent bleach bath (3,28) . Although this improved the durability of the coating, the adhesion was still not

sufficient. There are two possible explanations for those

results. Firstly, the spin finish removal method was not

sufficient leaving some spin finish on the fiber. In this

case, it is necessary to find an improved method to remove

the spin finish. Another reason is that the thermodynamic

adhesion between rayon and nylon is not strong enough to

hold these two materials together, even with removal of

the spin finish. In this case, a third material, such as a

coupling agent, is required to improve the interfacial

adhesion. Therefore, the present investigation was based

on both spin finish removal and coupling agent

pretreatment.

1. Interfacial Adhesion properties

Water was used as a solvent to remove the spin finish

rather than the acid and bleach bath treatment previously

used.

73

a. Effect of water pretreatment time

The nylon 6,6 fibers were washed with distilled water

for 1, 2, 6, 10, or 24 hours and then were coated under

the coating conditions described above in order to find a

suitable water pretreatment time. Fig.33 shows the effect

of water treatment times on weight loss during Accelerator

abrasion. There was more than 50% coating lost for the

samples with no spin finish removal; however there was

only 10% coating loss for the samples washed in water for

two hours. Results indicate that there was a minimum

weight loss for the fiber pretreated in water for 2 hours;

there was more coating loss for both increasing and

decreasing water pretreatment times. Apparently when the

water pretreatment time was less than two hours, the spin

finish was not as completely removed so that the

interfacial adhesion properties were reduced by the spin

finish. At pretreatment time longer than two hours, there

may have been unexpected damage to the fibers, which also

decreased the interfacial adhesion of the fibers. For

instance, at longer times the water soluble spin finish

may have diffused into the fiber, further inhibiting

interfacial adhesion between skin and core.

Nylon 6 , 6 fibers water treated for different time

periods were treated with aqueous solutions of the

coupling agent 41-6106, and then were coated at the

coating conditions described above. Fig.34 shows the

Coating weight loss (%)

Water pretreatment time (hr)

Fig.33 Effect of water pretreatment time on coating

weight loss of rayon/nylon 6,6 fibers.

Water pretreatment time (hr)

Coating weight loss ( 2 )

8 0

6 0

4 0

Fig.34 Effect of water pretreatment time on coating

weight loss of rayon/nylon6,6 fibers treated

with coupling agent Q t - 6 iOd for 22 sec.

-

-

2 0

0. I I I I I

0. 5 10 15 2 0 2 5

76

Accelerotor test result for those samples. There was only

a 10% coating weight loss for the samples washed in water

for one hours and pretreated with the coupling solution

for 22 seconds. When the water pretreatmental time was

longer than one hours, the coating weight loss increased

with water pretreatment time.

Consequently, these experiment results show that

water does remove the spin finish on the nylon 6,6 fiber

with subsequent promotion of the interfacial adhesion of

the S/C fiber. The 41-6106 coupling agent pretreatment

also improved the interfacial adhesion of the S/C fibers

even without complete removal of the spin finish, as will

be shown later.

b. Effect of Concentration of Coupling Agent

Solution

Nylon 6,6 fibers were washed with water for ten hours

and pretreated with 0.25%, 0.5%, and 0.75% solutions of

41-6106 for 22 seconds. The fibers were then coated using

the conditions described above. The Accelerotor test

results shown in Fig.35 indicate that the coating weight

loss decreased with increasing concentration from 0.25% to

0.5%, but there was no difference in coating weight loss

when the concentration changed from 0.5% to 0.75%.

Therefore 0.5% is the recommended concentration for this

coupling agent.

Coating 1 weight loss (%) I

Concentration of Ql-6106 solution (%I

Fig. 35 Effect of concentration of 41-6106 solution

on coating weight loss of rayonlnylon 6 , 6

fibers.

78

Acetic acid treated as described in Appendix A-2 was

used to prepare the Q1-6106/water solutions because Q1-

6106 was difficult to dissolve in water. The pH of the

prepared solutions was about 3.2. The effect of pH was

omitted in this series of experiments because of the

difficulty in obtaining a series of solutions with

different pH.

c. Effect of pretreatment

Table.12 shows the combined effects of spin finish

removal and coupling solution pretreatment. A water

pretreatment time of two hours and a coupling solution

pretreatment time of 52 seconds gave the best results.

Therefore, for nylon 6,6 fibers, there are two ways to

promote interfacial adhesion between skin and coating. One

is two hours water pretreatment to remove the spin finish

from the fibers. Another is sufficient coupling solution

pretreatment time. These two methods give similar results

of minimum coating weight loss. Considering economic

factors, the water prewashing method is recommended;

however, considering continuity of processing, the

coupling solution pretreatment method is recommended.

Table 12. Effect of pretreatment on the adhesion of rayon/nylon 6,6 fibers *

Water treatment 41-6106 solution Coating time (hr) treatment time (s) weight loss

0.5% concentration at pH 3.2.

2. Tensile properties

Neither water nor 41-6106 solution pretreatment nor

both water and the coupling solution pretreatment produced

any determined effect on the linear density and the

tensile properties of the rayon/nylon 6,6 fibers. The

tensile properties of samples exhibiting the best

interfacial adhesion were very close to those of untreated

samples (App. B5 to B8) .

3. Qualitative Observation

a. Microscopical Observation

For both the coated fibers pretreated in water for

two hours (Fig.36) and those pretreated for 52 seconds in

the coupling solution (Fig.37), there was still an even

coating on the fibers after the Accelerotor test. However

fibers undergoing no pretreatment showed much coating loss

with little coating remaining on the core fiber (Fig.38).

b. Dyeability

Nylon 6,6 core fibers, rayon/nylon 6,6 fibers with

water pretreatment for two hours, and rayon/nylon 6,6

fiber with 41-6106 solution pretreatment for 52 sec were

dyed with a direct red dye for 20 min at 100 C. Both S/C

fibers showed more bright and dark red color than the

nylon fiber. It means that there was an even rayon coating

on the rayon/nylon fibers because rayon has better

affinity for this dye than nylon does.

Fig.36 Rayon/nylon fibers with water pretreatment

for two hours. (a) uncoated; (b) coated

but not abraded; (c) coated and abraded

in Accelerotor. (70x1

Fig.37 Rayon/nylon fibers with ~1-61061water solution

pretreatment for 52 seconds. (a) uncoated;

(b) coated but not abraded; (c) coated and

abraded in Accelerotor . (70x1

Fig. 38 Rayon/nylon 6,6 fibers with no pretreatment

(a) uncoated; (b) coated but not abraded;

(c) coated and abraded in Accelerotor.

(70x1

CHAPTER V. CONCLUSIONS AND RECOMMENDATIONS

A. Conclusions

1. ~ i s t i l led water pretreatment can promote

interfacial adhesion of rayon/PP and rayon/nylon 6,6

fibers. The water pretreatment time had an effect on the

interfacial adhesion of the S/C fibers. Water pretreatment

for one to two hours is recommended for PP and nylon 6,6

fibers.

2. A suitable coupling agent solution pretreatment

promotes interfacial adhesion of the S/C fibers.

Increasing the pretreatment time increased the interfacial

adhesion of the fibers. Concentration and pH of coupling

agent solution also affects the interfacial adhesion of

the fibers.

3. The results of this indicate improved adhesion for

rayon/PP fibers, with a water pretreatment for one hour

and pretreatment with a 0.5% 2-6032 coupling agent-water

solution at pH 4.0 for 52 seconds or longer.

4. For rayon/nylon 6,6 fibers, either a water

pretreatment for two hours or a 0.5% Q1-6106 coupling

agent-water solution with pH 3.2 pretreatment for 52

second or longer is effective enhancing adhesion.

5. Neither a water pretreatment nor a coupling agent

(either 2-6032 or 41-6106) solutions pretreatment causes a

significant change in the tensile properties of rayon/PP

and rayon/nylon 6,6 fibers.

85

B. ~ecommendations

The durability of the rayon coating of rayon/PP and

rayon/nylon 6,6 fibers was promoted in this investigation.

If subsequent fabric studies suggest the interfacial

adhesion of the fibers is not sufficient. A more intensive

study for coupling agents and treatment times should be

considered. This should include finding other coupling

agents which have greater influence on promoting

interfacial adhesion. Furthermore a combining of the

corona discharge pretreatment technique with a coupling

agent solution pretreatment and/or with spin finish

removal pretreatment should also be considered.

To further develop the fiber coating technique for

industrial production, a more intensive study should be

considered to extend the fiber coating technique from

single fiber to multiple filaments. Improvement of the

water pretreatment technique to reduce the pretreatment

time and make the pretreatment process continuous should

be considered. utility of the techniques could also be

enhanced by combining the coupling agent solution

pretreatment method with the water pretreatment and the

coating processes.

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Rayon Fibers by Means of a Fiber Coating Processf1,

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the Production and Properties of-a Rayon/nylon Skin-

Core Type Bicomponent Fiberf1, M.S. Thesis, Ohio

University, March 1987.

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Scientific Publishing Com., N.Y., (1983).

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APPENDICES

A. Coupling Agent solution Preparation

A-1. Preparation of 2-6032 Solution

A measured amount of 2-6032 was added to distilled

water in a flask to reach the desired concentration. The

pH of the solution was then adjusted with acetic acid and

alkacid test ribbons with a pH range of 3.0 to 5 . 0 were

used to measure the solution.

A-2. Preparation of 41-6106 Solution

Since 41-6106 is difficult to dissolve in water,there

were two steps to prepare a 41-6106 solution. A mixture of

100 part 41-6106 and 5 part water was prepared and kept at

room temperature for 24 hours. After that acetic acid was

used to adjust the pH of water to about 3.5. Then the

previously water treated and aged Q1-6106 was added to the

pH adjusted water, then the mixture must be stirred

strongly. After that the pH of this mixture was adjusted

again to the desired value with acetic acid. The amount of

water and the diluted 01-6106 depended on the desired

concentration of the solution. Alkacid test ribbons with a

pH range of 3 . 0 to 5 . 0 were used to measure the solution.

B. Experiment Data

B-1. Effect of concentration of 2-6030 solution

on tensile properties of PP and rayon/PP

fibers

Concen. Linear Tenacity Initial Breaking ( % density (gf/tex) modulus elongation

(tex (sf/tex) ($1

uncoated

0.0 8.795 36.64 251.8 124.5

0.25 8.775 37.17 247.9 128.9

0.50 8.935 37.72 243.8 140.2

0.75 9.001 35.03 227.2 119.8

coated

* water pretreatment for 24 hours and pH 4.0 2-6032 solution pretreatment for 22 sec.

B-2 Effect of pH of 2-6032 solution on tensile

properties of PP and rayon/PP fibers

PH Linear Tenacity Initial Breaking density (gf/tex) modulus elongation (tex) (gf/tex) ( % I

uncoated

-- 8.965 36-64 251.8 124.5 3.5 8.842 39.19 277.7 144.1 4.0 8.935 37.72 243.8 140.3 4.5 8.925 36.19 246.6 125.8 5.0 8.975 35-59 246.1 126.6 .........................................................

coated

* water pretreatment for 24 hr and 0.5% 2-6032 solution pretreatment for 22 sec.

B-3 Effect of water and 2-6032 solution

pretreatment on tensile properties

of rayon/PP fibers

2-6032 Linear Tenacity Initial Breaking pretreat. density (gf/tex) modulus elongation time (sec) (tex) (gf/tex) (%

0. 9.692 31.84 249.9 122.9 -------------------------------.---------------------- water (lhr)

0. 9.574 33.71 261.7 136.5 22. 9.519 33.91 267.3 127.9 44. 9.529 34.77 241.5 129.4 --.----------------------------.----.-----------------

water (6hr)

0. 9.490 34.88 257.6 133.3 22. 9.552 35.60 240.3 130.8 44. 9.703 32.77 273.6 118.8 -------------------------------.----------------------

water (24hr)

* 0.5% 2-6032 solution with pH4.0.

B-4 tensile properties of rayon/PP fibers

2-6032 Linear Tenacity Initial Breaking pretr . density (gf/tex) modulus elongation time (sec) (tex 1 (gf/tex) ( % I

water (lhr)

B-5 Effect of water pretreatment time on tensile

properties of nylon and rayon/nylon fiber

Water Linear Tenacity Initial Breaking pretr. density (gf/tex) modulus elongation time (hr) (tea (gf/tex) ( 8 )

uncoated

0. 10.56 58.53 166.3 46.1 1. 10.39 57.06 161.3 40.3 2. 10.48 58.56 153.6 47.6 6. 10.42 58.94 157.3 45.9 10. 10.35 59.21 162.5 46.8 24. 10.35 60.20 163.7 45.7 ---.-------------------------------.-------.-----------

coated

B-6 Effect of water and 41-6106 pretreatment time on

tensile properties of nylon and rayon/nylon 6,6

fibers

Water Linear Tenacity Initial Breaking pretr. density (gf/tex) modulus elongation time (hr) (tex) (gf/tex) ($1

uncoated 0. 10.5647 58.535 166.281 46.10

coated 0. 11.0108 44.393 148.859 30.95 .........................................................

Q1-6106 (22sec) uncoated

coated

-

* 0.5% 41-6106 solution with pH 3.2.

B-7 Effect of water and 41-6106 solution

pretreatment time on tensile properties

of rayon/nylon 6,6 fibers

Pretreatment Linear Tenacity Initial Breaking time density (gf/tex) modulus elongation

(tex) (gf/tex) ( % I

water (hr) 2. 11.93 38.59 128.8 30.50

Q1-6106 (sec) 44. 12.06 38.48 129.0 38.48

* 0.5% 41-6106 solution with pH 3.2.