Morphological Structure and Surface Propertiesof Maleated Ethylene Propylene DieneMonomer/Organoclay Nanocomposites

Mihaela Homocianu,1 Anton Airinei,1 Daniela Maria Stelescu,2 Daniel Timpu,1 Aurelia Ioanid1

1‘‘Petru Poni’’ Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda, Iasi 700487, Romania

2National Research and Development Institute for Textile, Leather, and Footwear Research,93, Ion Minulescu Str., Bucharest 031215, Romania

The phase morphology and surface properties of somemaleated ethylene propylene-diene/organoclay nano-composites (EPDM-g-MA/OC) were characterized byscanning electron microscopy (SEM), atomic force mi-croscopy (AFM) and contact angle measurements.The effect of organoclay and/or compatibilizing agent[maleic anhydride-grafted polypropylene (PP-g-MA)] onthe properties of the EPDM-g-MA nanocompositeswas investigated. The quality and uniformity of nano-clay dispersion were analyzed by SEM and AFMimages. The experimental results showed an interca-late structure and biphasic morphology for the binaryblends based on EPDM and clay. The surface proper-ties of the studied composites are significantly influ-enced by the presence of a compatibilizing agent—PP-g-MA. POLYM. COMPOS., 33:379–387, 2012. ª 2012 Societyof Plastics Engineers

INTRODUCTION

Ethylene propylene diene rubber (EPDM) is obtained

by copolymerization of ethylene and propylene in the

presence of an unsaturated diene and is one of the most

widely used and fastest growing synthetic rubbers. The

saturated polymer backbone results in excellent resistance

to heat, oxidation, ageing, ozone, polar solvents, or micro-

bial attack. Such characteristics assure a broad range of

applications for EPDM, as for automotive profiles, electri-

cal insulation parts, footwear, wires, cables, hoses, roofing

barriers, sealing rings, sporting goods [1–6]. The most fre-

quently used diene termonomers are mainly ethylidene

norbornene and dicyclopentadiene.

Layered clays are inexpensive, naturally occurring

products and their incorporation in polymer matrices,

even at a much lower content (\5% by weight) deter-

mines a high reinforcing effect compared with traditional

fillers. In addition, significant improvements in a range of

properties were obtained in comparison with the proper-

ties of bulk polymers or conventional composites. These

characteristics include strength and storage modulus, heat

and solvent resistance, thermal stability, excellent gas bar-

rier properties etc. [7–10]. To achieve a nanoscale disper-

sion of clay in a polymer matrix, the clay is modified

with quaternary ammonium salts to produce an organo-

clay, which permits to obtain thus a modification of clay

surface polarity and an increase of intergallery distance.

In this way, organoclays can be easily dispersed into the

polymer matrix and nanocomposites with an intercalated

or exfoliated structure are formed [9, 11–13]. The method

presenting the highest commercial interest for preparing

rubber-based nanocomposites is direct melt intercalation.

Another widely utilized method is in situ polymerization

[14].

The compatibilizing effect of organoclay and the prop-

erties of materials are dependent on clay localization and

degree of its dispersion, which is related to the clay–poly-

mer affinity [15, 16]. Since EPDM does not contain polar

groups in the backbone, the homogeneous dispersion of

silicate layers in the polymer matrix will be achieved

with difficulty. A higher interaction between EPDM

chains and silicate layers can be realized by using an

adequate compatibilizer. Maleic anhydride-grafted poly-

propylene (PP-g-MA) has been utilized as an efficient

interfacial compatibilizer to assure the diffusion of poly-

mer chains of EPDM into the galleries of organoclay [17,

18]. However, EPDM elastomers exhibit low surface

tension, low water compatibility, and hydrophilicity.

The introduction of maleic anhydride units in EPDM

can determine the modification of surface properties due

to the interaction between polar groups of maleic anhy-

dride and organoclay by the formation of hydrogen bonds

in the system. The surface properties become very

Correspondence to: Anton Airinei; e-mail: airineia@icmpp.ro

DOI 10.1002/pc.22159

Published online in Wiley Online Library (wileyonlinelibrary.com).

VVC 2012 Society of Plastics Engineers

POLYMER COMPOSITES—-2012

important in improving adhesion between EPDM and

other polymers.

A previous article reported the preparation of some

EPDM-g-MA/organoclay nanocomposites by melt inter-

calation method and their evaluation in terms of thermal,

mechanical, and X-ray characteristics [19]. In this

work, the characterization of EPDM-g-MA/organoclay

nanocomposites has been made by scanning electron

microscopy (SEM), atomic force microscopy (AFM), and

contact angle measurements and the EPDM nanocompo-

sites containing compatibilizer and/or clay were compared

with a conventional composite, prepared for this study.

EXPERIMENTAL

Materials

EPDM grafted with maleic anhydride was Royaltuf 498

(maleic anhydride content 1 wt%, Mooney viscosity at

1258C:30), PP-g-MA (Polybond 3002) with 1 wt% MA and a

melting flow index of 7 g/10 min at 2308C/2.16 kg was

used as a compatibilizing agent between EPDM-g-MA and

organoclay. The organoclay was montmorillonite modified by

octadecyltrimethyl amine with the commercial name Nano-

mer 128E. Other chemicals including zinc oxide (neutralizing

agent), stearic acid (processing aid), zinc stearate (ionic plasti-

cizer), Irganox 1010 (antioxidant) were used as received.

Preparation

EPDM/organoclay composites were prepared by the

melt blending method in a Branbender Plasti-Corder

PLV330 having a mixing chamber volume of about 70

cm3. The composition and specimen designations of the

resulting blends are given in Table 1. The mEPDM and

mEPDM/OC composites were obtained, at an operating

temperature of 1708C and a 100 rpm rotor speed for a total

mixing time of 12 min, while the mEPDM/OC/PP compos-

ite was prepared at 1908C for 12 min as mixing time. The

processing procedure for the EPDM/OC mixture included:

mixing of EPDM-g-MA with organoclay for 2 min,

followed by the addition of zinc oxide, as crosslinking

agent, stearic acid, Irganox 1010 and zinc stearate, and the

mixing lasted for another 5 min. The resultant mixtures

were sheeted on an electrically operated laboratory roller

heated at 155–1658C. Then, the test specimens were

obtained as 2-mm thick plates by compression molding at

1708C for 5 min and at a pressure of 150 MPa using an

electrical press. The plates were then cooled down at room

temperature under pressure. The ionic crosslinking degree

was determined using a Monsanto rheometer.

Measurements

X-ray diffractograms were carried out with a Bruker

A8 Advance diffractometer using nickel-filtered CuKaradiation (k ¼ 0.1541 nm) at a generator voltage of

40 kV and a generator current of 35 mA. The diffracto-

grams were obtained with a scanning rate of 28/min in the

low range of 2h (1–208) at room temperature. The basal

spacing of silicate was estimated using Bragg’s equation:

k ¼ 2d sinh, where d is the spacing between clay layers, his the diffraction angle and k is the X-ray wavelength.

The phase morphology of the EPDM-based composites

was examined using an environmental scanning electron

microscope (ESEM) Quanta 200, operating at an acceler-

ating voltage of 25 kV with secondary electrons. SEM

analysis was performed on samples fractured in liquid

nitrogen; the surface of samples was covered with a thin

layer of gold by sputtering in a sputter coater model EMI-

TECH K550X, to prevent electrostatic charging build-up

during observation. The composition and elemental map-

ping of the surfaces of these specimens were determined

using an energy dispersive X-ray (EDX) system attached

to the ESEM instrument.

The AFM images were obtained in air, at room tem-

perature, on an ‘‘SPM SOLVER Pro-M’’ instrument (NT-

MDT, Russia). An NSG10/Au silicon tip with a 6-nm

radius of curvature, 95-lm cantilever length, a force con-

stant of 11.8 N/m and an oscillation mean frequency of

256 kHz were used. The apparatus was operated in the

semi-contact mode, with a 256 3 256 scan point size,

scan velocity of 10-65 lm s21, depending on roughness

on different scan areas.

The surface tensions, polar and dispersive components

of the samples were determined by static contact angle

measurements using the sessile drop method. The equilib-

rium contact angles of the solid were determined using

CAM101 contact angle meter (KSV Instruments) at room

temperature, equipped with software for drop shape analy-

sis. Contact angles were measured on 1 lL of wetting sol-

vent and the results reported represent the average values

of 10 determinations carried out for five droplets from

separate locations. Water (W), ethylene glycol (EG), and

formamide (FA) were utilized as probe liquids.

RESULTS AND DISCUSSION

Morphological Properties

X-ray diffraction is a useful method to detect the

changes in the interlayer distance of silicate layers and to

TABLE 1. Formulation for the EPDM-based composites.

Components

Sample code

mEPDM mEPDM/OC mEPDM/OC/PP

EPDM-g-MA 100 100 100

Zinc oxide 10 10 10

Stearic acid 1 1 1

Zinc stearate 20 20 20

Irganox 1010 2 2 2

organoclay 0 7.5 7.5

PP-g-MA 0 0 22.5

Total, g 133 140.5 163

380 POLYMER COMPOSITES—-2012 DOI 10.1002/pc

monitor the intercalation behavior of organoclay and

polymer chains. If the clay diffraction pattern of the com-

posite is located at equal or higher angles compared with

that evidenced in pure clay an ordinary composite is

obtained. A shift of the diffraction peak of the composite

to smaller angles determines an increase in the interlayer

spacing of the clay, which means that an intercalation

occurs, while a broadening of the diffraction peak is con-

sidered as the result of partial exfoliation [20]. The XRD

patterns of organoclay and EPDM-based composites are

depicted in Figure 1. It can be seen that the characteristic

diffraction peaks of organoclay are located at 3.81 and

5.658, corresponding to a basal spacing of 2.32 and

1.56 nm, respectively. mEPDM does not show any peak

in this region.

The XRD patterns of mEPDM/OC and mEPDM/OC/

PP nanocomposites show that the (001) plane reflections

are shifted to smaller angles than that of organoclay (2h¼ 2.248), leading to an increase in the gallery height to

1.62 nm. The shift of the characteristic diffraction peak of

organoclay to smaller angles and the expanding of the

gallery indicate that the polymer does intercalate into the

clay interlayers and suggest the intercalate structure of

the mEPDM/OC nanocomposites. The greater polarity of

EPDM-g-MA leads to an increase in the system compati-

bility with organoclay and to a better dispersion.

In general, the phase morphology of some heterogene-

ous blends based on elastomer and nanoclay, obtained in

melt state, depends firstly on the composition, and then,

on the component viscosity blends ratio, interfacial ten-

sion, and processing conditions. The quality and uniform-

ity of nanoclay dispersion were analyzed by ESEM. SEM

images were taken from the fractured surface of the initial

sample (mEPDM) and mEPDM/OC nanocomposites. The

fractured surfaces of the EPDM-g-MA composite are pre-

sented in Figure 2. The micrographs reveal differences in

roughness on the fracture surface as well as their hetero-

geneous aspect (Fig. 2a–c). On this large enough fracture

FIG. 1. XRD patterns of EPDM-based composites.

FIG. 2. SEM micrographs of mEPDM composite.

DOI 10.1002/pc POLYMER COMPOSITES—-2012 381

surface, many irregular domains may be remarked simi-

larly to some layered configurations located within large

folding (Fig. 2b). Backscattered SEM images of the same

zone reveal granular domains containing strongly segre-

gated particles, the surface being rougher (Fig. 2c). Grey

dots were observed on the fractured surface containing

zinc. The EDX spectra taken of the mEPDM composite

(Fig. 3) confirm the presence of Zn. The elements identi-

fied on the fracture surface are given in Table 2. These

observations are in agreement with other results from the

literature, by which ionic crosslinks are formed by the

ionic interactions of maleic anhydride-grafted EPDM with

zinc cations [21, 22], these carboxylic salts tending to as-

sociate as multiplets and clusters [23, 24]. These clusters

behave as an ionic microphase immersed into a non-polar

matrix and can act as a reinforcement site, leading to the

improvement of elastomer characteristics.

The morphology of binary blends based on EPDM and

clay was biphasic. The continuous elastomer phase under-

goes a complex process of microstructuration due to

crosslinking (Figs. 4 and 5). If in the initial stage of a

binary blend, layers are formed, these layers undergo a

coalescence process presenting a fibrilar or co-continuous

structure. Depending on the blend composition and com-

ponent characteristics, this structure can rapidly turns into

a disperse structure, which is determined by the crosslink-

ing process. In this case, on the micrographs of the frac-

ture surface, a granular phase morphology was observed,

having different dimensional particles of crosslinked

EPDM arranged as round layers. At higher magnifica-

tions, a variation in the granular structure of the round

layers was observed, making evident some hollows and

FIG. 3. EDX spectrum taken from mEPDM composite. [Color figure can

be viewed in the online issue, which is available at wileyonlinelibrary.

com.]

TABLE 2. EDX quantitative analysis of EPDM composites.

Samples

Elements (wt%)

C O Zn Na Mg Al Si Ca

mEPDM 90.29 6.40 3.31 – – – – –

mEPDM/OC 82.93 7.51 5.05 2.41 0.20 0.55 1.25 0.09

mEPDM/OC/PP 87.04 7.57 2.62 1.72 0.04 0.25 0.71 0.05FIG. 4. SEM micrographs taken from fracture surface of mEPDM/OC

nanocomposite.

382 POLYMER COMPOSITES—-2012 DOI 10.1002/pc

prominences. In the same time, a coalescence process

may occur among particles, so that the size of the cross-

linked elastomer particles depends on the competition

between the fracture and the coalescence processes occur-

ring during blending. A similar observation was also

reported in the literature [25, 26]. A good adhesion does

not exist between phases in all cases during the fracture

process, since many domains were taken out of their

initial location, thus remaining cavities, and the most

particles leaving the phase in which some hollows are

observed.

The particle sizes depend on different factors such as

the rheological properties of each phase, blending power,

reactive group content, and the technological conditions

of crosslinking. The microstructure of mEPDM/OC nano-

composites is biphasic, clay aggregates were observed in

the EPDM matrix due to the formation of the hydrogen

bonds between hydroxyl groups of the clay surface and

the carboxyl groups of maleated EPDM. By adding

maleated polypropylene (mPP) as compatibilizer, a better

dispersion of nanoclay particles was not observed

(Fig. 5). However, the nanoclay dispersion in the two

samples of mEPDM/OC and mEPDM/OC/PP was practi-

cally similar, but not complete.

On the backscattered images of fracture surface of

mEPDM/OC and mEPDM/OC/PP specimens, both nano-

clay aggregates of micronic sizes and some Zn agglomer-

ated domains were observed (Figs. 4c and 5c). Figures 6

and 7 show the EDX spectra of mEPDM/OC composites,

where Si, Na, Ca, O, Al elements represent the compo-

nents of organoclay (Table 2). SEM elemental mapping

technique was used to evidence the elemental distribution

on the fracture surface. Some agglomerations were

observed mainly for the Zn element. The results presented

in Figure 8 confirm the X-ray data regarding the good dis-

persion of nanoclay within the polymer matrix. EDX

microanalysis was carried out in different locations on the

composite samples giving nearly constant values of the

relative silicon amount, which suggests a quite uniform

dispersion of clay nanoparticles in the polymer.

AFM shows a strong potential in investigating the sur-

face and cross section morphology of nanocomposites,

FIG. 5. SEM micrographs taken from fracture surface of mEPDM/OC/

PP composite.

FIG. 6. Elemental composition of mEPDM/OC. [Color figure can be

viewed in the online issue, which is available at wileyonlinelibrary.com.]

DOI 10.1002/pc POLYMER COMPOSITES—-2012 383

permitting to obtain two dimensional (2D; plane) and

three dimensional (3D; relief) images. Also, the ‘‘phase

contrast’’ (pc) technique is an additional procedure that

affords the visualization of areas with different physical

properties (mechanical, density), providing data about

phase separations, presence of different particles or struc-

tures at nano or micro levels. To analyze the internal

morphology of EPDM composites, the samples were frac-

tured in liquid nitrogen and the cross section surface was

studied by AFM. Figure 9 shows the cross section images

of the mEPDM composite, with a root mean square

roughness of 5.44 nm. The phase contrast image reveals a

homogeneous material, as the phase shift is only of 38(Fig. 9c). Typical cross section images of the mEPDM/

OC/PP nanocomposite are presented in Figure 10. Here,

the root mean square roughness is of 6.29 nm, which is

very close to the value for the mEPDM sample. In this

case, the phase shift is much higher, of about 908 (Fig.

10c), which means that there are two very different com-

ponents in system, one is the polymer matrix and the sec-

ond the organoclay particles of 50–150 nm thickness, uni-

formly dispersed in the EPDM matrix with a planar orien-

tation. The phase separation of the two components in the

fractured area is revealed very clearly (Fig. 10b). The 2D,

3D, and pc images (Fig. 10) show that the organoclay

particles are parallelepipedic and do not present a sheet

architecture, which implies that the polymer was interca-

lated into the clay galleries, but exfoliation did not occur,

as evidenced by the X-ray investigations.

Surface Properties

The incorporation of organoclay in composite would

be expected to have an important influence on the surface

properties of the composites based on EPDM-g-MA. The

contact angles of the EPDM composites with water, EG,

and FA are listed in Table 3. EPDM is basically a hydro-

phobic material [18] and thus high values of contact angle

are expected. From Table 3, it appears that the contact

angles for the composite with nanoclay (mEPDM/OC) are

considerably higher than those of the unfilled sample

(mEPDM) and of the compatibilized nanocomposite

(mEPDM/OC/PP). This increase may be due to the

increase of surface polarity. Considering the contact angle

with water as a measure of hydrophobicity of a solid sur-

face, the data listed in Table 3 reveal that the addition of

organoclay in the composition increased substantially the

hydrophobicity (h ¼ 1238 for mEPDM/OC). PP-g-MA

incorporation into the matrix diminished the contact

angle. The composite surface can contain some mPP

added and thus the hydrophobicity of the material

decreases.

Then, the surface tension, dispersion and polar compo-

nents of the materials can be evaluated from the contact

FIG. 8. SEM image and the corresponding maps of elements for

mEPDM/OC/PP. [Color figure can be viewed in the online issue, which

is available at wileyonlinelibrary.com.]

FIG. 7. EDX spectrum of mEPDM/OC/PP composite. [Color figure can

be viewed in the online issue, which is available at wileyonlinelibrary.

com.]

384 POLYMER COMPOSITES—-2012 DOI 10.1002/pc

angle data, according to the geometric mean model [27–

29], using the following equations:

1þ cosh2

:clvffiffiffiffifficdlv

q ¼ffiffiffiffiffifficpsv

p:

ffiffiffiffifficplvcdlv

sþ

ffiffiffiffiffifficdsv

q(1)

csv ¼ cdsv þ cpsv (2)

where h is the contact angle of the test liquid with polymer,

subscripts lv and sv refer to the interfacial tensions between

liquid–vapor and surface–vapor, respectively, and super-

scripts p and d refer to the polar and dispersive or non-polar

component, respectively, of total surface tension, csv.To obtain information regarding the interaction

between the test liquid and the composite surfaces, the

work of adhesion, the interfacial energy, the spreading

coefficient and the Girifalco-Good’s interaction parameter

were calculated.

The work of adhesion, WA, the work required to sepa-

rate two surfaces in contact, is given by the expression

[30, 31]:

WA ¼ clvð1þ coshÞ (3)

FIG. 10. AFM images of the cryogenic fracture surface of mEPDM/

OC/PP composite: (a) 2D view, (b) 3D view, and (c) phase contrast

view. [Color figure can be viewed in the online issue, which is available

at wileyonlinelibrary.com.]

TABLE 3. Contact angle (8) results for composites.

Samples hW hEG hFA

mEPDM 107.05 67.81 83.24

mEPDM/OC 123.78 87.49 92.93

mEPDM/OC/PP 96.01 73.09 76.31

FIG. 9. AFM images of the cryogenic fracture surface of mEPDM

composite: (a) 2D view, (b) 3D view, and (c) phase contrast view.

[Color figure can be viewed in the online issue, which is available at

wileyonlinelibrary.com.]

DOI 10.1002/pc POLYMER COMPOSITES—-2012 385

The spreading coefficient, Sc, and Girifalco and

Good’s interaction parameter, F, between the solid sur-

face and the test liquid were determined using Eqs. 4 and

6 [30, 31]:

Sc ¼ csv � csl � clv (4)

where csl is interfacial energy, between the studied sur-

faces and test liquid, determined by Dupre’s Eq. 5 [30]:

csl ¼ csv þ clv �WA (5)

U ¼ clvð1þ coshÞ2ðclvcsvÞ1=2

(6)

The properties of the three probe liquids: water, EG,

and FA are given in Table 4 [32–34].

The solid surface tension, csv, dispersion and polar com-

ponents, cdsv and cpsv, of the composites can be calculated

from the contact angle by using Eqs. 1 and 2, knowingthe surface tension components of different liquids from

Table 4 and the contact angles from Table 3. A linear

plot of ð1þ cosh=2Þðclv=ðcdlvÞ0:5 versus ðcplv=cdlvÞ0:5 (due to

Eq. 1, [35]) produced a straight line, where ðcplvÞ0:5 is

given by the slope and ðcdlvÞ0:5 is the intercept. The total

surface tension, csv is the sum of cdsv and cpsv (Eq. 2).The resulting values of surface tension, csv, and its dis-

persive, cdsv, and polar, cpsv components, for all samples

are listed in Table 5. The csv values showed a slightly

increasing trend upon the addition of organoclay. Both

the dispersive as well as the polar components increased

for the mEPDM/OC composite containing organoclay

only, whereas no significant variation in csv occurred

when mPP was incorporated into the composition (Table

5). The results indicate that csv is mainly due to dispersive

forces, cdsv, and to a lesser degree, to polar forces, cpsv.The increase in the contribution of polar component, cpsv,to the surface energy can be due to the enrichment in po-

lar groups on the surface and to the enhanced total solid

surface free energy. For the simple mEPDM composite,

the csv value was 24.3, this value increasing to 28.2 for

the mEPDM/OC composite, suggesting that the nature of

the forces acting on the surface is different.

The work of adhesion, WA depends only on the contact

angle and the surface tension of the liquid [30]. The work

of adhesion, WA, for the composites under study, for the

three test liquids was calculated from Eq. 3, using the val-

ues h and clv from Tables 3 and 4, and its values are

given in Table 5. Generally, the values of WA are higher

for EG and FA compared with water. The adhesion work

can be correlated with the degree of interaction between

the polymer matrix and organoclay and/or compatibilizer.

High values of WA indicate a strong interaction between

components. For the mEPDM/OC composite, the values

of adhesion work are lower in the three test liquids, these

values increasing again when mPP was added. This indi-

cates that the absence of compatibilizing agent from the

mEPDM composite determined a good dispersion of the

components in the system, thus none of the selected

liquids can penetrate into the sample, which is more evi-

dent from the contact angle values (Table 3). Also, for all

test liquids, the values of interfacial energy csl are much

lower for the mEPDM/OC sample (Table 5).

The spreading coefficients of the test liquids used for

contact angle measurements, calculated according to Eq.4 are listed in Table 6. If their values are positive (Sc [0), the liquid will spontaneously wet and spread on a

solid surface, whereas if it is negative (Sc \ 0), the (par-

tial) absence of wetting and spreading can be evidenced

[30]. The spreading coefficient values are less negative

for EG and FA than those for water. The spreading coeffi-

cient for water becomes more negative and the wetting

will be difficult on the surface. This observation is in

good agreement with the highest contact angle values for

water (Table 3). From Table 6, it can be concluded that

EG (less negative values of Sc) is the better wetting agent

for these composites.

Girifalco-Good’s interaction parameter F was calcu-

lated using the Eq. 6 and the values for all studied com-

posites are presented in Table 6. This parameter allows us

to evaluate the degree of interaction between the test

liquids and the composite surface, higher values of Fpoints out a greater interaction. FW, FEG, and FFA are

the Girifalco-Good’s interaction parameters due to water,

EG and FA, respectively. The greatest values of Giri-

falco-Good’s interaction parameter were obtained for EG

and FA. Thus, the interaction between EG and FA and

the composite surface is more relating to water and the

TABLE 4. Surface energy parameters for test liquids (in mN/m) [32–

34].

Test liquid clv cdlv cplv

Water 72.8 21.8 51.0

Ethylene glycol 48.0 29.0 19.0

Formamide 58.0 39.0 19.0

TABLE 5. Dispersive, cdsv, and polar, cpsv, components and surface tension, csv (in mN/m), work of adhesion, WA, and interfacial energy, cs1, for allstudied samples.

Samples cdsv cpsv csv WA(w) WA(EG) WA(FA) cs1W cs1EG cs1FA

mEPDM 24.14 0.16 24.29 51.46 66.13 64.83 45.63 6.17 17.47

mEPDM/OC 26.94 1.27 28.20 32.32 50.10 55.04 31.92 10.34 10.57

mEPDM/OC/PP 22.05 2.25 24.30 65.17 61.96 71.73 68.68 26.10 31.16

386 POLYMER COMPOSITES—-2012 DOI 10.1002/pc

composite surface. The incorporation of organoclay in the

composite without maleated PP (mEPDM/OC) leads to

the decrease of interaction between composite surface and

probe liquid.

The changes in the surface properties such as WA, Sc,and F with the composition of samples can be due to var-

iations in the surface roughness. The presence of a com-

patibilizing agent—maleated polypropylene (PP-g-MA),

generally, further improved the wettability and slightly

hydrophilicity in organoclay nanocomposites.

CONCLUSIONS

EPDM-g-MA nanocomposites were prepared by melt

blending method in a Branbender Plasti-Corder. XRD pat-

terns, SEM, and AFM results revealed the intercalate

structure of studied EPDM-based nanocomposites, the

good dispersion of nanoclay within the polymer matrix

and that the PP-g-MA was an efficient compatibilizing

agent for studied composites. Also, by EDX elemental

mapping technique was evidenced the distribution of ele-

ments of organoclay on the fracture surface of nanocom-

posites. These results confirm the dispersion of nanoclay

within the polymer matrix excepting some agglomeration

observed mainly for Zn element. The surface properties

such as wettability and slightly hydrophilicity of the stud-

ied organoclay nanocomposites are clearly improved by

the addition of compatibilizing agent, maleated polypro-

pylene (PP-g-MA) in polymer matrix.

NOMENCLATURE

AFM Atomic force microscopy

EG Ethylene glycol

EPDM Ethylene propylene diene rubber

ESEM Environmental scanning electron microscope

FA Formamide

MA Maleic anhydride

OC Organoclay

PP Polypropylene

SEM Scanning electron microscopy

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TABLE 6. Spreading coefficient, Sc and Girifalco-Good’s interaction

parameters, F, between water, ethylene glycol or formamide, and surface

composites.

Samples Scw ScEG ScFA FW FEG FFA

mEPDM 294.14 229.87 251.17 0.61 0.97 0.86

mEPDM/OC 2113.28 245.90 260.96 0.36 0.68 0.68

mEPDM/OC/PP 280.42 234.04 244.27 0.77 0.91 0.95

DOI 10.1002/pc POLYMER COMPOSITES—-2012 387