Effect of maleic anhydride-grafted ethylene–propylene rubber on the mechanical, rheological and morphological properties of organoclay reinforced polyamide 6/polypropylene nanocomposites

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European Polymer Journal 4l (2005) 687_696

EUROPEAN

POLYMER

JOURNAL

www.elsevier. com,/loca teleuropolj

frecr or materc anhydflde-grafted ethylene_propylenerubber on the mechan ical, rheological and

morphological properties of organoclay reinforcedpolyamide 6/polypropylene nanocomposites

W.S. Chow u, A. Abu Bakar u, Z.A. Mohd Ishak u,*.

J. Karger-Kocsis o, U.S. Ishiaku c

u School of Materials and Minerql Resources Engineering, Engineering campus, (Jniuersiti Sains Mataysia,b rnstituteror.composite Materiats

',I:';#::;ff::'J;;I!,:;:rT!;i;!,:!i,ir; X'!:::'!ooo, o.uru,, Kaiserstautern, Germanyc Aduanced Fibro-science, Kyoto Institute of Technology, Matsu{isakt, sakyo-ku, Kyoto 606-g5g5, Japan

Received 7 February 2004; aooepted 27 October 2004Available online 7 Januarv 2005

Effect of maleic anhydride-grafted

Abstract

Polyamide 6/polypropylene (PA6/PP = 70130 parts) blends containing 4 phr (parts per hundred resin) of organophilicmodified montmorillonite (organoclay) were compatibilized with male[ anhydride-grafted ethylene-propylene rubber(EPRgMA)' The blends were melt compounded in twin screw extruder followed by injection molding. The mechanicalproperties of PA6/PP nanocomposites were studied by tensile and flexural tests. The miirostructure of the nanocompos-ite were assessed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffrac-tion (xRD)' The d1'namic mechanical properties of the PA6/PP blend-based nanocomposites were analyzed,by using adynamic mechanical thermal analyzet (DMTA). The rheological properties were conducted from plate/platerheometryvia dynamic frequency sweep scans' The melt viscosity in aligl strear rate region was performei uy using a capillaryrheometer' The strength and stiffness of the PA6/PP-based nan-ocomposites were improved significanly with the incor-poration of EPRgMA. Adding EPRgMA to the PA6/PP blends resulied in a finer dispersion of the pp phase. TEM andXRD results revealed that the organoclay was dispersed more homogeneously in the presence of EpRgMA, however,mostly in the PA6 phase of the blends. DMTA results showea tnatllRgtvtA worked as an effective compatibilizer.The storage (G') and loss moduli (G") assessed by plate/plate rheometry of pA6/pp blends increased with the incorpo-ration of EPRgMA and organoclay. Furthermore, the apparent shear viscosity of the pA6/pp blend increased signifi-cantly for the EPRgMA compatibilized PA6/PP/orgunoiiuy nanocomposite. This was traced to the formation of aninterphase between PA6 and PP (via PA6-g-EPR) and effective intercalation/exfbliation of the organoclay.

@ 2004 Elsevier Ltd. All rights reserved.

Keywords" Polyamide 6/polypropylene blends; organoclay; Nanocomposires; Compatibilization, maleic anhydride-graftedethylene-propylene rubber

-Err.rponding author. Tel.: +60 4 593 l7gg;fax: +60 4 5g4 l0ll.E-mail address.. [email protected] (2.A. Mohd Ishak).

0014-3057/$ - see front matter o 2004 Ersevier Lrd. Alr rights reserved.doi: 10. 1016/j.eurpolymj.2004. | 0.041

688 W.S. Chow et al. I European polymer Journal 4l (2005) 6g7496

2.16kg lo^ad) and density of pA6 were 35 g/10 min and| .14 glcm3, respectively. pp (pro-Fax SM-t40) was sup-plied by Titan Himont Polymer (M) Sdn. Bhd. MFI anddensity of PP is 25 gll0 min. (at 230"Cand2.16 kg load)and 0.9 g/cm3, respectively. EpRgMA (Exxelor VAl80l) containing lwtY, MA was supplied by ExxonMobil Chemical. The ethylene/propylene ratio of thismaterial was 70130 wt%. MFI of EpRgMA is 125 gl10 min (at 190'C and 1.2 kg load). Organoclay (Nano_mer l.30TC) was a commercial product from NanocorInc, USA. This organoclay is a white powder containingmontmorillonite (-70 wt%) intercalated by octadecyl-amine (-30 wto/o). Mean dry particle size of the organo_clay was between 16-22 microns. The designation, andcomposition of the blends tested are given in Table l.

2.2. Specimen preparation

Melt compounding of the pA6/pp (70130) blends andnanocomposites were carried out on counter-rotatingtwin screw extruder (Berstoff). The extrusion zone tem-perature ranged from 220-230 oC. prior to extrusion,PA6 pellets and organoclay were dehumidified by usinga vacuum oven at 80 "C for 8 h. The extrudates were pel_letized with the Haake pelletizer. The pellets were injec-tion molded into standard tensile bar using a NiigataAN 50 injection molding machine. Injection moldingtemperature ranged from 225-240 oC. prior to injectionmolding, all pellets were dehumidified in vacuum oven(80 "C for 8 h). The tensile test specimen was moldedin Type I according to ASTM D 638.

2.3. Mechanical properties

Tensile tests were carried out on a Instron-5582 ma-chine at 23 "C, ac*,ording to ASTM D638, at a crossheadspeed of 50 mm/min and the E-modulus, tensile strengthand elongation at break value were determined. Flexuralmeasurements were performed according to ASTMD790 using 3-point bending configuration at 3 mm/mindeformation rate.

2.4. Melt fow index ( MFI), density and rheologicalmeasurements

Melt flow index and density of various materials wasmeasured by using Melt Flow Indexer (at 230 oC, load

Table I

Materials designation and compositions

Designation Composition Parts

PA6/PP PA6/PPPA6/PP/5E PA6/PP/EPRgMAPA6IPPI4TC PA6/PP/organoctayP A6|PPl sEl4TC PA6/PP/EPRgMA./organoclay

1. Introduction

Incorporation of nanofillers/nano_reinforcementsinto polymer matrices (e.g., thermoplastics, thermosets,elastomers) has attracted considerable interest indicatedby the increasing number of publications up to now[-26]. The degree of dispersion (e.g., exfoliation, inter_calation) and the compatibility of the nano_reinforce_ments (e.g., layered silicates, nanotubes, nano_fibers,nano-fillers) with the polymer matrix are important fac_tors which result in remarkable changes in properties(mechanical, rheological, barrier, etc.) of a poiy-er.Numerous reports described polymer/clay nanocompo_sites produced, via incorporation of either pristine(unmodified) clays or organophilic tayered silicates(organoclay) in a single polymer matrix [l-26]. How_ever, thermoplastic nanocomposites based on polymerblends seem to be a new approach in the nanocompositestudies. A similar approach has been well accepted in thearea of fibre reinforced composites [27]. The work pre-sented in the present paper focuses on the study ofthermoplastic nanocomposites based on blends of poly_amide 6 (PA6) and polypropylene (pp). pA6 and pp hasbeen chosen to achieve a good balance of properties inthe final product. While PA6 has good overall mechani_cal properties, PP will help to provide a good resistanceagainst moisture and ensures good processability [2g]. Ina previous study on the PA6/pp nanocomposites [29],4 phr organophilic modified montmorillonite (organo_clay) has been observed to be the optimum loading forthe blends. A significant improvement in the strengthand stiffness of the composites was reported whenmaleated polypropylene (PpgMA) was used as compat-ibilizer for the PA6/PP blend [30]. The ppgMA compar-ibilized blend-based nanocomposites which showed amore homogeneous morphology and a better claydispersion than the uncompatibilized counterparts. Inorder to get a better understanding on the compatibiliza-tion for PA6/PP/organoclay system, in the present studymaleic anhydride-grafted ethylene-propylene rubber(EPRgMA) was chosen as a compatibilizer. Note thatEPRgMA has a markedly higher melt viscosity thanPPgMA which should affect the properties of the relatedblends. Thus, the present work was devoted to thestudy of the effect of EPRgMA on the morphology,mechanical, and rheological behaviour of pA6/pp-basednanocomposites.

2. Experimental

2.1. Materials

The PA6 (Amilan CM 1017) used in this study was acommercial product from Toray Nylon Resin AMI-LAN, Japan. The melt flow index (MFI at 230 oC and

70t3070t30ts70130t4

70t30tst4

W.S. Chow et al. I European polymer Journal 4l (2005) 657496 689

2.l6kg) and density balance (model precisa XT 220 A),respectively. Rheological measurements were made indynamic mode on a rheometer (ARES rheometer, Rheo_metric Scientific) equipped with parallel plate geometry(plate diameter: 25 mm) at230 "C. Sheets were compres_sion molded to about I mm thickness and punched intodisc of 25 mm diameter. Dynamic frequency scan testswere conducted for all samples at a strain of l%o at230 "C. The strain amplitude (l%) was within the linearviscoelastic region as deduced from dynamic strain scantests performed for all pA6/pp blends and p/l6tpplorganoclay nanocomposites. The melt viscosity in a highshear rate region at T = 230 oC was assessed by a capil_lary rheometer (Rheo-Tester 1500, Gdttfert) u.irrg u

"up_illary of 20 mm length and I mm diameter.

2.5. Microscopic examination (SEM and TEM)

The fracture surface of selected pA6/pp_basednanocomposites was inspected in a scanning electronmicroscope (SEM; Leica Cambrige Ltd. model S 360)after gold coating. Transmission electron microscopy(TEM) measurements were carried out with a LEO912 Omega transmission electron microscope applyingan acceleration voltage of 120 keV. The specimens wereprepared using an Ultracut E (Reichert & Juns) ultra_microtome. Thin sections of about 100 nm tiicknesswere sliced with a Diatome diamond knife at roomtemperature.

2.6. X-ray difraction (XRD)

Wide-angle X-ray spectra were recorded with a D 500diffractometer (Siemens) in step scan mode using Ni_fiI_tered CuK, radiation (0.1542nm wavelength). powdersamples were scanned in reflection, whereas the injec-tion-molded compounds were scanned in transmis_sion mode in the interval of 29 = 2-10o. The interlaver

Table 2

spacing ofthe organoclay was derived from the peak po_sition (des1-reflection) of the XRD diffractogramsaccording to the Bragg equation.

2. 7. Dynamic-mechanical thermal analysis ( D MTA )

The complex modulus (E+), its storage (E ) and lossparts (t') and the mechanical loss factor (tan6=E,lE') as a function of temperature (Z), were assessed bydynamic mechanical thermal analysis (DMTA) usingan Eplexor 25N device of Gabo eualimeter, Germany.DMTA spectra were taken in tension mode at l0 Hzfrequency in a broad temperature range (?"= _ll0to 230'C). The DMTA device operated under loadcontrol by setting 50 N as static and +25 N as dynamicload.

3. Results and discussion

3. L Rheological properties

The MFI value of PA6/pp blend decreased in thepresence of EPRgMA (cf. Table 2). This may be due tothe formation of a graft copolymer, e.g., pA6gEpR inthe blend (cf. Fig. 1) as well as due to the high viscosityof the EPRgMA itself. The incorporation of EpRgMAin the PA6/PP/organoclay nanocomposite slightly de_creased the MFI of the blend. This may be attributedto the interaction between the octadecylamine group(intercalant of organoclay) and the anhydride g.oup o1the EPRgMA.

The storage (G') and loss moduli (G,) resulting fromthe dynamic frequency scans are shown in Fig. 2(a) and(b). Both parameters increased monotonicallv in the en_tire frequency range with the addition of organoclay intothe PA6/PP blend. This likely reflects the interfacialinteraction between the intercalated and exfoliated

Densities, MFI and mechanical properties of the compositions

Properties Compositions

PA6/PP and also PA6/pp/5E PA6IPPI4TC PA6/PP/5E PA6IPPISEI4TCDensity (RT) d" t

MFI (230'C,2.16kg) g/10 min

Tensile (RT, 50 mm/min)E-modulus GpaUltimate strength MpaElongation at break %

Flexural (RT, 3 mm/min)

0.95

50.4

1.87

32.1

22.8

t-t576.2

1.03

38.9

2.tl38n1

|.9978.7

1.04

lt.7

1.99

29.449.7

t.680.2

1.05

10.7

2.2s47

6.7

2.0295.9

.E-modulusStrength

GPaMPa

690 W.S. Chow et al. I European Polymer Journal 4l (2005) 6g7496

c-o H

l' l''ffircH,-r-- f;--+-lllHO

- Hro

4TC) markedly enhanced in the presence of EpRgMAcompatibilizer (PA6|PP|5E|4TC). This may be attri-buted to the compatibilization effect of EPRgMA forthe system containing PA6, PP and organoclay. Anotherpossible reason is that the EPRgMA may interact withthe intercalated and exfoliated silicate layers of theorganoclay 129,301. Fig. 2(c) shows the complex viscosityof the PA6/PP blends and nanocomposites taken from

EPRgMA ?t-?t.tl_c c./\,/\ooo

I

I

IY

o-cI

OH

{"r,-"xffiH.-T ,, + ".*4,"*,*[-i+P46

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I

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PAGgEPR

Fig. l. Possible chemical reactions between pA6, pp and EpRgMA.

silicate layers and the polymer matrix. According to Liet al. [31], the interfacial adhesion between the clay tac-toids and the matrix is dramatically improved due to theformation of partially intercalated structures. Note thatthe change of G' in the low frequency range reflects sen-sitively the efrect of silicate dispersion on the viscoelasticproperties of nanocomposites [32]. At the low frequency,the G' of PA6/PP/organoclay nanocomposite (pA6/pp/

T=230'C

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ll.S. Chow et al. I Europeen Polymer Journal 41 (2005) 687496

0l

691

I 000

.-

l

E

@

J100

-q

=oE@oga

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Frequency (radls)

the dynamic frequency sweep tests. The complex visco-sity of PA6/PP increased in the presence of organoclay.This is in agreement with the MFI data reported earlier(Table 1) and likely due to the partly exfoliated andintercalated silicate layers which restrict the melt flowof the blend matrix. According to Boucard et al. [33],at low shear rates, the silicate platelets of high aspectratio are well separated and this strongly increases theviscosity of the melt. On the contrary, at higher shearrates the platelets are oriented in the flow directionwhich consequently leads to a reduction in the viscosity.The incorporation of the EPRgMA into PA6/PP nano-composite increased the complex melt viscosity signifi-cantly. This again corroborates the potential interfacialinteraction and thus compatibilization effect of theEPRgMA between PA6, PP and organoclay. Accordingto Li et al. [31], the intensive interaction between theexfoliated silicate layers and polymer chains increases

the complex viscosity and causes a marked shear thin-ning at low frequency values.

The effect of organoclay and EPRgMA on theapparent melt shear viscosity of the PA6/PP blend is

T=230"C

E:

l*PA6rPP--l| -.- PA6/PP/4TC I| +PA6/PPI5E I

| * peslpplss+rc I

110Frequency (racUs)

100

(b)(a)

51=oaq'=xoEo

(c) Frequency (radls)

Fig. 2. (a) Storage modulus (G') vs frequency plot for the PA6/PP blend and PA6/PP/organoclay nanocomposite. (b) Loss modulus(d') vs frequency plot for the PA6/PP blend and PA6/PP/organoclay nanocomposite- (c) Complex viscosity (4*) vs frequency plot forthe PA6/PP blend and PA6/PP/organoclay nanocomposite.

6

.=oo.9

co

q

1000 1200 1400 1600 1800 2000

Apparent shear rate (1/s)

Fig. 3. Apparent viscosity vs apparent shear rate for the PA6/PP blend and PA6/PP/organoclay nanocomposite.

shown in Fig. 3. The apparent viscosity of the PA6/PPblend increased significantly for the EPRgMA com-patibilized PA6/PP/organoclay nanocomposite. The

shear thinning behaviour of the nanocomposite is

aaa!

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692 W.S. Chow et al. I European polymer Journal 4l (2005) 6SZ496

similar to that of the blend and its organoclay contain_ing version.

3.2. Mechanical properties

The effect of EPRgMA on the tensile and flexuralproperties is presented in Table 2. The incorporationofthe organoclay increase the stiffness ofthe uncompat_ibilized PA6IPP blend significantly. Further enhance_ment of the ,E-modulus of the pA6/pp nanocompositeis observed with the incorporation of EpRgMA. Thismay be attributed to the improvement in the interlacialinteraction of the organoclay with the pA6/pp in thepresence of EPRgMA.

Incorporation of the organoclay into pA6/pp mildlyincreased the ultimate strength. However, a remarkableimprovement in the ultimate strength was observed byadding EPRgMA. This is believed to be associatedwith two factors: first, the degree of dispersion (i.e.,degree of exfoliation/intercalation) of the silicate layersof organoclay in the PA6/pp matrix; second. the interfa_cial interaction of the organoclay and the pA6/pp matrix.EPRgMA may favour the degree of dispersion of theorganoclay via intercalation into the silicate lavers ofthe organoclay and subsequent exfoliation durin! shearand elongational flows in extrusion and iniection moldineoperations. Some maleic anhydride group of the EpRglMA may react and form H-bonds with the octadecl_amine groups of the initial intercalant of the orsanoclav.

Note that the elongation at break of tnJ peOlp-pblends increased with the incorporation of EpRgMA.

This may be related to the formation of pA6gEpRcopolymer (cf. Fig. l), which improved the interfa_cial bonding between pA6 and pp. The addition ofthe organoclay caused a tremendous drop in the elon_gation at break of the pA6/pp blends. This is likelvdue to the co-existence of agglomerated layered sili-cates (un-exfoliated organoclay), and exfoliated/interca_lated organoclay layers and particles in the matrix.However, a slight increase in the ductility of pA6/pp/or_ganoclay nanocomposite was observed with the incor_poration of EPRgMA. This may again be traced tothe compatibilZing eflect of EpRgMA (e.g., the func_tionality of maleic anhydride group) and/or the toughen-ing effect of the EPRgMA. Nore that EpRgMA is theusual toughening agent of "supertough" polyamides[34].

Table 2 indicates that the flexural modulus andstrength of the PA6/PP/organoclay increased signifi_cantly in the presence of EPRgMA. This trend resemblesto that of the tensile properties. However, the flexuralstrength is almost double of the tensile strength. Thismay be due to the differ-ence in the deformation modeand the alignment of the silicate layers in the matrixowing to injection molding. The exfoliated silicate layerof organoclay may align predominantly parallel to themelt flow direction during injection molding l7l. Fig. ashows a proposed interaction between organoclay andPA6gEPR copolymer. It is believed that hydrogenbonding could form between the amide group of thePA6gEPR and the amine group of the organoclay inter-calant (octadecylamine).

CH

I

c

cH^l'I

o:: <--:HII

I

H

- ry-6"

AII

Hydrogenbonding

,(c", ),ucn,

Octadecylamine groupintercalated in the organoclay

Fig. 4. Possibte interaction between pA6gEpR and organoclay.

CH"

J"",-"nfrcH,-f+

o-c c-o H

\,/, LPA6gEPR copolymer 'rrr-l-tCH^+-

C

- {j-l-L .r ll Jn

il

IV.S. Chow et al. I European Polyner Journal 4l (2005) 6g7496 693

3. 3. Dynamic-mechanical thermal proper ties

Fig. 5(a) show the dynamic storage vs temperaturetraces for the PA6/PP blends and related nanocompos_ite. Note that, in the range of room temperature (23_28'C), the storage modulus (E,) of pA6/pp increasedsignificantly with the addition of organoclay and EpRg-MA. This is in agreement with the E-moduli from thestatic mechanical tests as discussed earlier. The effectof EPRgMA on the loss factor (tan d) for the pA6/ppblend and nanocomposite is presented in Fig. 5(b).Two relaxation peaks were observed at around 50 oC

and -55 oC, which referred to as q and B relaxationpeaks of PA6, respectively. According to Mohd Ishakand Berry [35] the e relaxation peak is assigned to thebreakage of hydrogen bonds between the polymerchains which induces long range segmental motion inthe amorphous area. So, the c-relaxation transition rep-resents the glass transition temperature (?"") of pA6. TheB-relaxation peak is traced to those segmental amidegroups in the amorphous area which do not participatein hydrogen bonding. The a relaxation peak for thePA6/PP/organoclay nanocomposite is lower than thePA6/PP blend. It is believed that the organoclay becameintercalated/exfoliated and a polymer layer formedaround the layers. Here the polymer molecules shouldhave reduced chain mobility as the reinforcing effect ofthe clay platelets dominates. However, in the presenceof EPRgMA the intensity of the a-relaxation peak ofPA6/PP/organoclay nanocomposite increased. Thisobservation is similar to our previous work on maleatedpolypropylene (PPgMA) compatibilized pA6/pp nano-composites [30]. This finding may be attributed to the"elastomeric" contribution of the compatiblizer. Notethat EPRgMA should be located in the amorphousphase and in addition, it reacts with pA6 by formingan interphase of amorphous nature. This increases the

intensity of the Z, peak. A similar explanation holdsalso for the p-relaxation.

3.4. X-ray dffiaction (XRD)

Fig. 6 shows the XRD patterns (in the range of20 = 2-10o) for organoclay and uncompatibilized andEPRgMA compatibilized PA6/pp nanocomposites.The organoclay patterns reveals a broad intense peakat around 20 = 3.25', corresponding to a basal spacingof 2.72 nm. The XRD pattern of uncompatibitized andEPRgMA compatibilized PA6/PP/organoclay compo-sites do not show the characteristic basal reflection ofthe pristine organoclay. However, the XRD traces showa shoulder at 20 = 2.85o superimposed to the decliningpart of the XRD spectrum. This is a clear indication that

F

oo

Fig. 6. XRD spectrananocomposites.

567820 (degree)

for the organoclay and

10

PA6/PP

(b)

orE!uoE5tto

=o.DGoo

(a)0 50 100

Temperature (oG)

.50 0

Temperature (oG)

Fig. 5. (a) E' vs I traces for the PA6/PP and PA6/PP/organoclay nanocomposite. (b) ran d vs Z rraces for the pA6/pp and pA6/pp/organoclay nanocomposite.

694 WS. Chow et al. I European polyrner Journal 4l (2005) 657496

a portion of the organoclay is intercalated. XRD spectraof the organoclay filled pA6/pp nanocomposites displaya prominent increase in the intensity at lower 29 valueswhen compared with those of the unfilled blends. Thislikely reflects that the organoclay used was partly exfo_liated and partly inrercalated (and the related XRb peaklays 20 < 2'). This XRD behaviour is similar to that ofreported by other researchers [8,15,17,30].

3.5. Morphology (SEM and TEM)

Fig. 7(a) display a SEM picture taken from of thefractured surface of the uncompatibilized pA6lpplorganoclay nanocomposite. On fracture surface irresu_

larly shaped and large pp particles, dispersed in thePA6 matrix, can be resolved. These particles easily de_bond and detach from the PA6 matrix due to the poorinterfacial adhesion between them. Incorporation ofthe organoclay alone does not produce a finer morpho_logy in the PA6/PP blends. The lack of plastic deforma_tion on the fracture plane explains the sharp drop in theductility of the PA6/PP blend in the presence of organo_clay B9l.

Fig. 7(b)-rompared to Fig. 7(a)-shows the trans_formation from brittle to ductile failure mode due tothe compatibilization effect of EpRgMA. A more homo_geneous, fibrillated morphology characterizes the frac-ture surface of PA6/PP/58/4TC. The compatibilizer,

Fig' 7' (a) SEM micrograph showing the tensile fractured surface of an uncompatibilized PA6/pp/organoclay nanocomposite (pA6/pp/4Tc)' (b) sEM micrograph showing the tensile fractured surface of an EPRjMA compatibilized pRdrp/organoclay nanocomposite(PA6/PP/5E/4TC).

Fig' 8' (a) TEM micrograph taken from an uncompatibilized PA6/PP/organoclay nanocomposite (pA6/pp/4TC). Note: picturerepresents the PA6 phase. (b) TEM micrograph taken from a compatibilized PA6/PP/organoclay nanocomposite containing 5 phr ofEPRgMA (PA6/PP/5E/4TC).

WS. Chow et al. I European Polymer Journal 4l (2005) 687496 69s

located in the interphase, may act as a "bridge" betweenthe PA6 and PP phases and thus enhances the loadabilityofthe blend. It is believed that there are also interfacialinteractions between the compatibilizer (MA groups)and the organoclay (octadecylamine groups) in accor-dance to the mechanism proposed earlier (cf. Fig. a).

Fig. 8(a) and (b) show characteristic TEM micro-graphs taken from the uncompatibilized and EPRgMAcompatibilized PA6/PP/organoclay nanocomposites,respectively. The dark lines represent the thickness ofindividual clay layers or clay agglomerates. Thick darkerlines display stacked silicate layers (tactoids). In uncom-patibilized PA6/PP nanocomposites the orlanoclay waspartly intercalated and partly exfoliated, as shown byTEM (cf. Fie. 8(a)). This indicates that a mixture of de-laminated, intercalated silicate layers and aggregatedtactoids may co-exist in the PA6/PP matrix. However,a more pronounced exfoliation can be noticed with theincorporation of EPRgMA (cf. Fig. 8(b)). The TEMinvestigations also showed that the clay layers and par-ticles are preferentially located in the PA6 phase. Thisresult is also in harmony with our previous work per-formed on PPgMA compatibilized PA6/PP/organoclaynanocomposites.

4. Conclusions

Based on this work devoted to study the effect ofEPRgMA compatibilizer on the properties of PA6/PP(70130 wt%") blends containing 4 phr octadecylamineintercalated organoclay, the following conclusions canbe drawn:

l. Incorporation of organoclay improved the stiffnessand reduced the ductility as expected owing to itsexfoliation/intercalation. The addition of EPRgMAcompatibilizer to the blend decreased the MFI valueand increased the strength and ductility parameters.This was attributed to the generation of a graftedpolymer (PA6gEPR) which formed an interphasebetween PA6 and PP.

2. The storage and loss shear moduli of the PA6/PPblend increased with incorporation of the organo-clay. This effect was even more pronounced whenEPRgMA was added, as demonstrated by plate/platerheometry. The melt viscosity increased significantlyas a result of the common use of EPRgMA andorganoclay. This was attributed to the formation ofPA6gEPR, and high viscosity of the EPRgMA, andthe interaction of PA6gEPR and organoclay.

3. The coarse dispersion of PP became markedly finerowing to the compatibilizer EPRgMA. The organo-clay was present in delaminated/exfoliated and inter-calated forms simultaneously as evidenced by TEMand XRD studies. The incorporation of EPRgMA

facilitated the dispersion of the organoclay in thePA6/PP matrix, and more exactly in the PA6 richphase.

Acknowledgments

The authors would like to thank the Ministry of Sci-ence, Technology and Environment (MOSTE), Malaysiafor the IRPA grant (Grant No: 06317l/IRPA). Specialscholarship granted by Universiti Sains Malaysia andGerman Academic Exchange Service (DAAD) scholar-ship to one of us (W.S. Chow) is gratefully acknowledged.We also thank Dr. Thomann (University of Freiburg,Germany) and A.A. Apostolov (Sofia University, Bul-garia) for performing the TEM and XRD measurements,respectively. JKK thanks the Fonds der ChemischenIndustrie for the support of his research work.

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