Effect of Palmyra palm fiber on properties of natural rubber vulcanizate

Effect of palmyra palm fiber filler on propertiesof natural rubber vulcanizate

by

J.T. Nwabanne, P.K. Igbokwe and E.J.A. Ezeonyebuchi

reprinted from

WORLD JOURNALOF ENGINEERING

VOLUME 11 NUMBER 6 2014

MULTI-SCIENCE PUBLISHING COMPANY LTD.

World Journal of

EngineeringWorld Journal of Engineering 11(6) (2014) 565-574

World Journal of

Engineering

1. IntroductionFillers are compounding ingredients added to

rubber compounds for the purpose of reinforcing

Effect of palmyra palm fiber filler onproperties of natural rubber vulcanizate

J.T. Nwabanne*, P.K. Igbokwe and E.J.A. EzeonyebuchiDepartment of Chemical Engineering, Nnamdi Azikiwe University, Awka, Nigeria.

Email address: [email protected]

(Received 25 April 2014; Accepted 30 August 2014)Abstract

The effect of partial replacement of carbon black by Palmyra palm fiber on the curecharacteristics, physico-mechanical and swelling properties of natural rubber vulcanizateswas studied. The Palmyra palm fibers were extracted, treated and characterized so as todetermine pH, moisture content, and ash content, loss on ignition, conductivity, cellulose,lignin, Hemicellulose, cellulose/lignin ratio and Acid soluble lignin. The functional groupsin the Palmyra palm fiber was also determined using FTIR. The Palmyra palm powder withan average particle size of 75 µm was used in this study. The natural rubber/carbonblack/Palmyra palm fiber (NR/CB/PPF) composites having eight different loadings, 0/70,10/60, 20/50, 30/40, 40/30, 50/20, 60/10, 70/0, were prepared using a laboratory size tworoll mill. The maximum Torque of NR/CB/PPF composites increased with increasingcommercial filler loading ratio. The scorch time and cure time of NR/CB/PPF compositesdecreased as the ratio of CB loading increased. The tensile strength, modulus of elongation,tear strength and abrasion resistance of all the composites increased as the commercial fillerloading ratio increased. This is due to the presence of the commercial filler which gave abetter filler interaction. Also this behavior can be attributed to the particle size and surfacearea of the fillers used as the fillers with small particle size usually have a larger surfacearea which supports better filler-rubber interaction. The hardness increased as the palmyrapalm fiber loading increased. The elongation at break decreases as carbon black fillerloading increases except for the composite with CB/PPF ratio of 10/60. The effect of fillerloading on the swelling behavior of NR/CB/PPF composites was also investigated inaromatic and aliphatic compounds. Result showed that the composites with more carbonblack has less absorption than those with more palmyra palm fiber showing that thecompounds with more carbon black has better interaction than those with palmyra palmfiber.

Key words: Natural rubber, Vulcanizate, Palmyra palm fiber, Carbon black, Physico-mechanical

World Journal of

Engineering

them and/or cheapening their cost. Traditional fillersinclude carbon black, silica, calcium carbonate,calcium silicate and clay. Carbon black is the most

ISSN:1708-5284

566 J.T. Nwabanne et al./World Journal of Engineering 11(6) (2014) 565-574

popular filler added to the rubber compounds due toits ability to enhance certain properties, especiallymechanical properties (Moonchai et al., 2012).Carbon black is derived from petro-chemicalsources but the unstable price of crude oil has led tothe search for filler that are derived from othersources. (Satyanarayana et al., 1986). Agriculturalby-products, maize cobs, cocoa pod husk, sugarcanechaff, rice husk, plantain peel, Palmyra palm fiberetc., are low cost materials, readily available and canbe used in place of carbon black in natural rubbervulcanization. The growing environmentalawareness is another driving force that leads to thisresearch since fibers from agricultural byproductsare biodegradable and does not cause anyenvironmental hazards. They can be easily recycled.The regulations on using synthetic materials are alsoa serious factor to consider which make the use ofbio fibers an advantage over other types of fillers(Lundaquist et al., 2003).

Palmyra palms are economically useful andwidely cultivated in tropical regions. The Palmyrapalm has long been one of the most important treesof Cambodia and India, where it has over 800 uses.The leaves are used for thatching, mats, baskets,fans, hats, umbrellas, and as writing materials.Palmyra palm trees are in great abundance in Awka,Anambra state of Nigeria as well as the Northernpart of Nigeria. Palmyra palm fruits are not used forany purpose and hence they constitute solid waste.This research work is aimed at harnessing thepotential of Palmyra palm fiber as a filler additivewhich can be used as an alternative or in partialreplacement to the commonly used commercialcarbon black filler in natural rubber vulcanizate witha consequent reduction in cost of product.

2. Materials and methods2.1. Materials

The Palmyra palm fruits were collected fromNnamdi Azikwe University, Awka, Nigeria andprocessed to get Palmyra palm fiber. The naturalrubber (NR) crumb of grade standard Nigerianrubber (SNR10) which also conforms to TechnicallySpecified Rubber (TSR-10), used for this work wasobtained from Rubber Research Institute of Nigeria,Iyanomo, Benin city, Nigeria. The othercompounding ingredients and additives used werezinc oxide, processing oil, Trimethyl quinoline(TMQ), Mercaptobenzoylthiazole (MBT), stearicacid, carbon black (N330) and sulphur. These

compounding agents are of commercial grade andso were obtained from Jonaz Industrial Chemicals,Stinpex Chemicals and Ally Industrial Chemicals inBenin, Edo State, Nigeria.

2.2. Fiber collection and preparationThe crude fibers were obtained from the ripe

Palmyra palm fruit collected from Nnamdi AzikiweUniversity Awka Anambra state Nigeria. ThePalmyra palm fruits were retted and the fibersextracted, washed and sun dried.

2.3. Fiber surface treatmentA combined treatment of saline and alkali

treatment was adopted. The rationale behind theselection of these treatments was that thesetreatments have been found to enhance interfacialand mechanical strength with the epoxy matrices.

2.3.1. Alkaline treatmentPre-dried Palmyra palm fibers were soaked in 1M

sodium hydroxide (NaOH) solution at ambienttemperature maintaining a liquor ratio of 20:1 (by weight). The fibers were immersed in thesolution for 30 minutes. The fibers were copiouslywashed with water to remove any trace of alkali onthe fiber surface and subsequently neutralized with1% acetic acid solution. The treated fibers were thenair dried for 12 hours and later dried in an oven at 60 ºC for 8 hours (Chimekwene et al., 2012).

2.3.2. Silane treatmentFor the treatment, a solution of 0.5wt% saline

coupling agent [3-(2-aminoethyl amino) propyltrimethoxy silane] was prepared in acetone asacetone promotes hydrolysis. The pH of the solutionwas adjusted to 5.5 with acetic acid and stirredcontinuously for 5 minutes. The already treatedfibers from the alkali solution were then immersedin the saline solution for 45 minutes. Fibers werethereafter washed with acetone and then in water toremove chemical residues until a pH of 7 wasobtained and then dried in an oven at 70 ºC for 24hours. This procedure of silane was employed for allfibers previously alkali treated. After the treatmentoperations the fibers were then blended(Chimekwene et al., 2012).

2.4. Fiber characterizationCharacterization was done in two phases (i)

physic-chemical analysis of the fiber and (ii)instrumental analysis using Fourier TransformInfrared Spectrophotometer (FTIR) to determine theconstituents of Palmyra palm fiber used. The

J.K. Nwabanne et al./World Journal of Engineering 11(6) (2014) 565-574 567

untreated, treated and CB (N330) werecharacterized in terms of pH, loss on ignition,conductivity, bulk density, acid soluble lignin, ashcontent, moisture content, cellulose, hemicelluloseand lignin. These parameters were determined usingthe appropriate standard methods (Hyman et al.,2008, Kurschner and Hoffer, 1933) and resultspresented in table 2.

2.5. Fiber blending/sievingThe treated fibers were blended in an electric

blender immediately after drying. The blendedfibers were sieved into different mesh sizes withU.S.A standard testing sieve (A.S.T.M E.11specification) comprising of 600, 250 and 75 µm.The essence of the sieving is to get the requiredparticle size comparable to the size of conventionalcarbon black used in rubber compounding. Aftersieving, the samples were stored in desiccators toavoid moisture absorption. Afterward the fiberswere then weighed into the required volume ratiosfor the compounding operation.

2.6. CompoundingThe formulation used in the compounding of the

natural rubber is provided in the table 1. Mixing ofthe ingredients was done on a (160 × 320 mm) tworoll mill maintaining a temperature below 80 ºCthrough an attached water cooling system to avoidany cross-linking during mixing. The curecharacteristics were measured using the MonsantoRheometer, (ALPHA ODR 2000 Model, made inGermany) in accordance with ASTM 3814 method.The curing of the test pieces was done bycompression molding in a steam heatedhydraulically operated press with a pressure of 150kg/cm at a temperature of 160 ºC. The cure timespredicted by the Mosanto rheographs were used asguide to obtain vulcanization for the test specimens.

2.7. Determination of physical properties of thevulcanizates

2.7.1. Tensile strengthThe tensile strength of the vulcanizates was

measured with a Zwick Roell tensile testingmachine made in U.K., 1992 with cross head speedof 250 mm/min using a dumbbell test specimen typeas contained in DIN53504, 05/994. Five sampleswere tested and the average values were taken.Tensile properties such as tensile strength, tensilemodulus and elongation at break were obtainedfrom tensile testing. Hardness of the vulcanizateswas determined using a Rockwell machine ascontained in ASTM E-18 method. Wallace Akrontester was used in accordance with B.S (1958)method of testing vulcanized rubber. The swellingbehavior of the vulcanizates determined studiedaccording to ASTM D471.

3. Results and discussion3.1. Physico-chemical properties of UPPF and

TPPFThe Physico-chemical properties of UPPF and

TPPF are shown in table 2. The cellulose content ofuntreated and treated fibers is 58.68 ± 0.66 and61.20 ± 0.211 respectively. The moderate cellulosecontents and relatively high lignin contents areindications of high mechanical strength of the fiber.The cellulose with high lignin content is anindication of stiffness and low pulp yield. Thus, thisfiber would be suitable for composite reinforcementbut not for pulp or paper making.

Ash contains silica that has many undesirableeffects. Silica blunts cutting machinery, reduces thedigestibility of straw, interferes with the pulpingprocess by forming scales on the surface of thereactors and makes combustion more difficult. Theash content is untreated fiber 1.67 ± 0.021 andtreated fiber 1.28 ± 0.87 which are comparable tothe best fibers of flax and hemp (1-2%) but lowerthan jute (8%), ramie (5%) and cotton (10%)(Mwaikambo, 2006). The reduction in the ashcontent of the alkali treated sample may be as aresult of reaction between NaOH and any of theinorganic components, for silicon to give sodiumsilicate.

The Hemicellulose content of untreated fiber is13.94 ± 0.56 and treated fiber is 11.48 ± 2.11. Thelow hemicellulose content of the plant fiber impliesthat its water absorbing capacity will be low since

Table 1.The formulation for carbon black/Palmyra palm fiber as fillersin natural rubber compounding

Ingredients PhrNatural rubber 100Stearic Acid 2Zinc oxide 5Trimethyl quinoline, 1Mercaptobenzoyl thiazole 1Sulphur 2Processing oil 2Carbon black 0 10 20 30 40 50 60 70Palmyra palm filler 70 60 50 40 30 20 10 0


hemicellulose is the cell wall polymer with thehighest water sorption capacity. This is responsiblefor the high moisture absorption of natural fiberleading to swelling and presence of voids, whichresults in poor mechanical properties and reducesdimensional stability of composites. This property ofthe fiber reaffirms the potentials of the Palmyra palmfiber used in this study for biocomposite technology.

Since lignin provides fibers with compressivestrength, stiffens the fiber and protects the celluloseand hemicellulose from chemical and physicaldamage, the biofibres used in this study will besuitable for composite reinforcement because itcontains 29.22 ± 0.002 for untreated fiber and 30.33± 0.44 for treated fiber. The acid-soluble lignin ofthe biofibre is within the range obtained for othercharacterized biofibres. The lignin content of thefibers influences the structure, properties,morphology, flexibility and rate of hydrolysis.Fibers with higher lignin content appear finer andwill be more flexible thus, can be used forcomposite manufacture.

The moisture content of the untreated fiber was9.64 ± 0.001 while that of treated fiber was 10.23 ±0.026. The determination of the moisture content offibers is very important because fiber dimensionsand properties vary with the moisture content(Mohanty et al., 2000). Such properties affected bythe moisture content include the degree ofcrystallinity, crystallite orientation, tensile strength,swelling behavior and porosity (Sukumaran et al.,2001). Also, increased moisture content decreaseselectrical resistance and this affects the dimensional

stability (Mohanty et al., 2000; Sukumaran et al.,2001). The strong hydrophilic nature of plant fibersmeans that precautions must be taken to improve thewater-related dimensional stability of the fibers, andto enhance the low compatibility between the fibersand the hydrophobic polymeric matrix. The highmoisture content after alkalization process is due tothe removal of non-cellulose compounds such aswaxes; the fibers have tendency to absorb moisture.However, the use of the alkali and saline treatedsample in composite material decreases its ability toabsorb moisture because the fibers gets masked withthe polyester resin in the laminate with a strongeradhesion, resulting in greater hydrophobicity andlesser water absorption.

3.2. Phytochemical analysisThe phytochemical analysis of the fiber is shown

in table 3. It revealed that alkaline and Silanetreatment is necessary due to presence of thesephytochemicals, to remove the lipohilic extractives(gums and waxes) and to remove the polar

UPPF-Untreated Palmyra palm fiber, TPPF-Treated Palmyra palm fiber.

Table 2.Physico-chemical properties of UPPF and TPPF

S/N Test parameter UPPF TPPF1 Percentage n-hexane/methanol extractives (%w/w) 5.44 –2 Cellulose (% w/w) 58.68 ± 0.66 61.20 ± 0.2113 Lignin (Klason or acid insoluble) (% w/w) 29.22 ± 0.002 30.33 ± 0.444 Hemicellulose (%w/w) 13.94 ± 0.56 11.48 ± 2.115 Moisture content (%) 9.64 ± 0.001 10.23 ± 0.0266 Ash content (%w/w) 1.67 ± 0.021 1.28 ± 0.877 Cellulose/Lignin ratio > 2.0 >2

ASL- and its derived products (%w/v)8i Ferulic acid (322 nm) 0.012 N.D8ii p- coumaric acid (308 nm) 0.26 ± 0.05 N.D8iii Vanillin (230 nm) 0.0331 ± 0.42 N.D8iv Total Acid Soluble Lignin (ASL %w/v) 205 nm 0.321 0.245 ± 0.0139 Loss on ignition (%) at 800 ºC – 7510 Conductivity (µs) – 33111 pH of slurry – 5.412 Bulk density (g/ml) – 0.213 Particle size (µm) – 75

Table 3.Phytochemical analysis palmyra palm fiber

S/N Phytochemical Quantitative

1 Alkaloids ++2 Flavonoids –3 Proteins –4 Carbohydrates ++5 Tannins +++6 Oils –7 Resins +


extractives (proteins, tannins etc). Extractives affectthe performance of plant fibers in composites.

The sign +++ shows relatively high abundance ofcompound; ++ shows Moderate presence and +shows low presence. Palmyra fiber has highabundance of Tannins, moderate Carbohydrates andAlkaloids with low presence of Resins. It has noFlavonoids, proteins and oils.

3.3. Fourier transform infrared analysisThe result of the FTIR analysis is presented in

table 4 (treated palmyra palm fiber) and table 5 (foruntreated palmyra palm fiber) and also given infigures 1 and 2. The FTIR analysis of the samples(treated and untreated palmyra palm fiber) showedthat the fibers contain certain amines, phosphine,alkanes, alkenes, carboxylic acids, ethers andalcohol compounds. The presence of amine andphosphine shows that the fiber is good becauseamine and phosphine are potential antioxidants. Themost abundant types of bond on the treated fiber are N-H, P-H, C-H and C-O. The modes of bondsare stretch and bending.

1000 500 350.01500cm−1

20003000

___ c:\pel_datal\spectra\untreated palmora fibres.sp.-UNTREATED PALMORA FIBRES

4000

0.000.10.20.30.40.50.60.70.80.9

%T

3440.00

2931.42 2348.57

1746.37

1640.93

1467.09

1022.53

1116.58

1.01.11.21.31.41.51.61.71.81.9

2.00

1000 500 350.01500cm−120003000

___ c:\pel_datal\spectra\untreated palmora fibres.sp.-TREATED PALMORA FIBRES

40000.000.10.20.30.40.50.60.70.80.9

%T

3445.712920.00

2348.57

1649.48

1461.39

1031.08

1002.33925.64

1.01.11.21.31.41.51.61.71.81.9

2.00

Fig. 1. FTIR result of untreated Palmyra palm fiber.

Fig. 2. FTIR result of treated Palmyra Palm fiber.

Table 4.FTIR of untreated Palmyra palm fiber

Peaks (cm1) Bond Compound Type Mode Transmittance % Concentration

1. 3440.00 N-H Amines Stretch 0.13 Medium2. 2931.42 C-H Alkanes Stretch 0.24 Strong3. 2348.57 P-H Phosphine Stretch 0.42 Medium and

sharp4. 1746.37 C=O Aldehydes, Ketones, Stretch 0.74 Strong

Carboxylic acids Esters5. 1640.93 N-H Amines Bend 0.81 Medium6. 1467.09 C-H Alkanes Scissoring 1.12 Variable

and bending7. 1116.58 C-O Alcohols, Ethers, carboxylic Stretch 1.64 Strong

acids, esters8. 1022,53 C-O Alcohols, Ethers, stretch 1.84 Strong

carboxylic acids, esters

Table 5.FTIR of treated Palmyra palm fiber

Peaks (cm1) Bond Compound Type Mode Transmittance % Concentration

1. 3445.71 N-H Amines Stretch 0.01 Medium2. 2920.00 C-H Alkanes Stretch 0.14 Strong3. 2348.57 P-H Phosphine Stretch 0.31 Medium and sharp4. 1649.48 N-H Amines bending 0.52 Broad5. 1461.39 C-H Alkanes Stretch 0.73 Variable6. 1102.33 C-O Alcohols, Ethers, carboxylic

acids, esters Stretch 0.76 Strong7. 1031.08 C-O Alcohols, Ethers,

carboxylicacids, esters Stretch 0.81 Strong8. 925.64 C-H C-H bend 1.71 Strong


3.4. Cure characteristics of carbon black/ palmyrapalm fiber

The minimum torque (ML) in a rheographmeasures the viscosity of the vulcanizates, and themaximum torque (MH) is generally correlated withthe stiffness and crosslink density. The differencebetween maximum (MH) and minimum (ML) torqueis a rough measure of the crosslink density of thesamples and designated as ∆M. From table 5 it isnoticed that the highest value of ∆M is obtained fromsample CB/PPF (70/0). Hence the crosslink density ismaximum for CB/PPF (70/0) sample in comparismwith the other seven samples. This is also confirmedby the results obtained by the equilibrium swelling(Figs 13 and 14) and the physic-mechanical testresults. The scorch time (Ts2) is the time required forthe minimum torque value to increase by two unitsand measures the premature vulcanization of thematerial.

3.4.1. TorqueIt was found that the torque (MH) increased as

carbon black (CB) to Palmyra palm fiber (PPF)ratio increased and decreased as PPF to CB ratioincreased. This indicates that as more carbonblack gets into the rubber matrix, the mobility ofthe macromolecular chains of the rubber reducesresulting in more rigid vulcanizates (Hussain etal., 2010). Generally, the variation in torquedepends on the nature and concentration of filler,its shape, size and interaction of the filler with thematrix. The increase in maximum Torque (MH)from the 30/40 filler loading ratio resulted fromthe good reinforcement or better interactionsbetween the rubber matrix and palmyra palm fiberfiller. The rubber filler interaction will imposehigher restriction in the mobility of the rubber’smacromolecular chains, consequently increasingthe value of MH. It can be seen that the incrementin MH is more pronounced in carbon black ratio toPPF composites. This observation is associatedwith the difference in the two different types offillers, which vary in particle size. Carbon blackhas a smaller particle size when compared to thatof Palmyra palm fiber used. Smaller particle sizedfillers tend to form stronger rubber-fillerinteractions in the composites due to their highsurface area per unit mass. Thus, the addition ofCB causes an appreciable increase in MH withincreasing ratio of CB loading as this can be seenin the graph of torque against volume fillerloading (Fig. 3).

3.4.2. Scorch time and cure timeFigures 4 and 5 show the effects of partial

replacement of carbon black with Palmyra palmfiber on scorch time (ts2) and cure time (t90) ofnatural rubber composites. The scorch time and theoptimum cure time of NR/CB/PPF compositesincreased as PPF loading was increased anddecreased with increasing CB filler loading. This

MLMH

70605040

Volume filler loading (phr)

Tor

que

(kg-

cm)

302010005

101520253035404550

Fig. 3. Effect of CB/PPF on Torque of natural rubber compounds.

ts 1ts 2

70605040Volume filler loading (phr)

Sco

rch

time

(sec

s)

30201000

0.5

1

1.5

2

2.5

3

3.5

4

Fig. 4. Effect of CB/PPF loading on Scorch time of naturalrubber compounds.

Min. cureMax. cure


Cur

e tim

e (m

in)

30201000

1

2

3

4

5

6

Fig. 5. Effect of CB/PPF loading on Cure time of naturalrubber compounds.


may be attributed to the differences in pH, carbonand moisture contents. Also the increase in scorchtime and cure time may be due to the presence of thephytochemicals in the PPF used as this can causeretardation of the accelerator activity, which in turncan slow down the sulphur reaction leading toincreased scorch and cure times.

Muniandy et al. (2012) reported similar findings intheir research work. Osabohien et al. (2007) in theirresearch on cure characteristics and physic-mechanicalproperties of natural rubber filled with the seed shells ofCherry, obtained similar results. The rheometriccharacteristics of the samples are given in table 6.

3.4.3. Cure rateFigure 6 shows the effect of CB/PPF filler

loading on cure rate of the vulcanizates. It can beseen that vulcanizates with higher CB content has ahigher cure rate when compared to vulcanizateswith fiber loading. The trend observed in curecharacteristics is attributed to differences in fillerproperties. The cure enhancement of thevulcanizates can be associated with the filler relatedparameters such as surface area, surface reactivity,particle size and moisture content. In general, afaster cure rate is obtained with filler having a highsurface area, smaller particle size and low moisture

content. The cure rate is directly related to thehumidity and water content of the rubber compound(Ekebafe et al., 2010).

3.5. Physic-mechanical properties of natural rubbercompounds with CB/PPF blends

Physico-Mechanical properties of Palmyra palmfiber/carbon black-filled natural rubber vulcanizatesare presented in figures 7–12 and table 7. There wasincrease in tensile strength, modulus, tear strength,abrasion resistant and hardness with fiber loadingscontaining higher ratio of carbon black than Palmyrapalm fiber. The elongation at break generallydecreased with increasing fiber loading. The Palmyra

Series 1


Cur

e ra

te (

min

−1)

30201000

1020

4030

50607080

Cure rate

Fig. 6. Effect of CB/PPF on cure rate of natural rubber compounds.

Table 6.Rheometric characteristics of the CB/PPF compounds

FIBER(CB/PF)

Characteristics 0/70 10/60 20/50 30/40 40/30 50/20 60/10 70/0

Scorch time (ts2) 3.50 3.31 3.25 2.45 2.50 2.43 2.51 2.20Minimum torque(ML) 2.31 2.97 3.09 2.93 3.26 3.20 3.19 3.25Maximum torque (MH) 37.82 37.79 38.54 41.91 41.62 42.30 44.33 44.31∆M = (MH – ML) 35.51 34.82 35.45 38.98 38.36 39.10 41.14 41.06Optimum cure time (t90) 5.38 5.21 5.01 4.24 4.37 4.24 4.23 3.54Cure rate (100/(tc90-ts1)) 50.76 49.75 51.55 54.35 50.76 52.63 55.25 70.42


Ten

sile

str

engt

h M

Pa

302010002

64

108

12

1614

1820

Fig. 7. Effect of filler loading on Tensile strenght of naturalrubber composites.

7060504030Volume filler loading (phr)20100

0

50

100

150

Tea

r st

reng

th (

N/s

)

200

250

Fig. 8. Effect of filler loading of Tear strenght of naturalrubber composites.


filled vulcanizates showed higher percentageelongation compared to the carbon black vulcanizates.This indicates better resilience for the palmyra palmfiller filled vulcanizates and consequently lowers heatbuildup and hysteresis for rubber articles going to bemade with filler having palmyra palm fiber. Thedecrease in elongation at break with filler loading canbe due to the adherence of the filler particles of rubbermatrix causing stiffening effects on the polymer chainand decreasing stretching.

3.6. Swelling propertiesTable 8 shows solvent swelling characteristics of

Palmyra palm fiber to carbon black ratio fillednatural rubber vulcanizates. These composites wereinvestigated in aromatic and aliphatic solvents. Thediffusion experiments were conducted by thesorption gravimetric method. The factors that affectthis include level of cross-link, filler dispersion,nature of solvent and fillers (Egwaikhide et al.,2007). The uptake of aromatic solvent is higher than

Table 7.Physic-Mechanical properties of natural rubber compounds filled with CB/PPF blend

CB/PF(phr) 70/0 60/10 50/20 40/30 30/40 20/50 10/60 0/70Modulus 50, Mpa 0.9 1.0 0.95 0.7 0.8 0.6 1.1 0.7Modulus 100, Mpa 1.45 1.5 1.4 1.0 1.1 0.85 1.5 0.85Modulus 200, Mpa 2.8 2.4 2.45 1.5 1.55 1.05 2.1 1.05Modulus 300, Mpa 4.65 3.7 3.85 2.15 2.15 1.4 3.05 1.35Modulus, 500, Mpa 9.75 7.3 7.8 4.1 3.85 2.4 2.8 2.2Tensile strength, Mpa 19 17 16.7 11.15 11.4 9 8.4 7.85Elongation at break % 756.5 828.5 790 841 926 1005.5 597 1009.5Tear strength, (MNm-1) 228 204 200 133 136 108 101 94Abrasion resistance 40 41 42 43 43 43 44 45HARDNESS(IRHD) 68 65 64 63 60 56 55 53

70

M.50


201000

2

4

6

8

Mod

ulus

% (

MP

a)

10

12

M.100

M.200M.300M.500


0

200

400

Elo

ngat

ion

at b

reak

%

600

1200

Series 1

1000

800

Fig. 9. Effect of filler loading on Modulus of natural rubber composites.

Fig. 10. Effect of Elongation at break on natural rubber composites.


0

2010

30

5040

60

Har

dnes

s (I

RH

D) 70

80

Fig. 12. Effect of filler loading on Hardness of natural rubber composites.


39

40

41

42

Abr

asio

n re

sist

ance

inde

x

43

46

45

44

Fig. 11. Effect of filler loading on Abrasion resistance indexof rubber.


that of aliphatic solvent for the composite. This iscomparable to the swelling behavior of Isora/naturalrubber composites in oils used in automobiles(Mathew et al., 2006). The effect of fiber loading onthe swelling behavior of the composites was alsoinvestigated in oils like petrol, diesel and lubricatingoil. When a cross-linked polymer is brought incontact with a solvent, the network absorbs a certainamount of liquid to an extent determined by themolecular weight of the liquid. The investigationrevealed that petrol having a lower molecularweight than diesel and lubricating oil diffuses faster

than diesel and lubricating oil and is accommodatedin the rubber matrix with less hindrance. This isfollowed by diesel and then lubricating oil. Thedecrease in sorption with increasing carbon blackfiller loading may be that each filler particle behavesas an obstacle to the diffusing molecule and it showsbetter filler-rubber interaction.

4. ConclusionThis work was an investigation of the effect of

Palmyra palm fiber on natural rubber vulcanizates.Different compositions of PPF was used to replacethe commercial carbon black in natural rubbercompound. The work has shown that Palmyra palmfiber can replace carbon black up to 57% and stillhave a good effect on the compound formed. Thisstudy showed that Palmyra palm fiber can beemployed in natural rubber vulcanization as wellas in other engineering works. Further research canbe exploited by controlling particle size andparticle distribution, improving filler dispersion,its surface functionality and also other methods ofvulcanization can be employed using Palmyrapalm fiber.

ReferencesBritish Standard Institution. 1958. Methods of testing

Vulcanized rubber, BS 903–A19.

Chimekwene C.P., Fagbemi E.A., Ayeke P.O., 2012.

Mechanical properties of plantain empty fruit bunch

fiber reinforced epoxy composite. International Journal

of Research in Engineering, IT and Social Sciences

2(6), 86-94.

Egwaikhide P.A., Akporhonor E.E., Okieimen F.E., 2007.

Effect of fiber filler on the cure characteristics physico-

mechanical and swelling properties of natural rubber

vulcanisates. International Journal of Physical Sciences

2(2), 39–46.

Table 8.Equilibrium sorption in organic solvents of natural rubber compounds filled with CB/PPF in percentage absorption

PPF/CB ratio Toluene Hexane Lubricating oil Dissel Petrol

70/0 258.68 106.85 15.87 124.36 166.1360/10 243.59 102.90 14.13 123.88 162.6350/20 219.27 100.71 11.26 123.81 159.1540/30 194.59 97.87 9.86 118.42 154.3530/40 193.66 95.74 9.35 113.11 152.3320/50 169.70 90.24 9.34 112.22 152.2110/60 145.95 85.48 9.13 110.48 149.550/70 111.61 83.72 9.09 107.02 146.67


0

50

100

150

Sw

ellin

g in

dex

%

300

Toluene250

200 N-hexane

Fig. 13. Effect of filler loading on equalibrium sorption ofaromatic solvents on natural rubber composites.


0

40

20

60

80

100

Sw

ellin

g in

dex

%

180

160

140

120

PetrolDiesselLub. oil

Fig. 14. Effect of filler loading on equalibrium sorption ofaliphatic solvents on natural rubber composites.


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Effect of Palmyra palm fiber on properties of natural rubber vulcanizate

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