Composites: Part B 43 (2012) 1164–1170

Contents lists available at SciVerse ScienceDirect

Composites: Part B

journal homepage: www.elsevier .com/locate /composi tesb

Thermal and impact study of PP/PET fibre composites compatibilizedwith Glycidyl Methacrylate and Maleic Anhydride

Mohammad Asgari, Mahmood Masoomi ⇑Department of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran

a r t i c l e i n f o a b s t r a c t

Article history:Received 15 June 2011Accepted 2 November 2011Available online 11 November 2011

Keywords:A. Polymer (textile) fibreB. Impact behaviourD. Electron microscopyE. Compression mouldingGlycidyl Methacrylate

1359-8368/$ - see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.compositesb.2011.11.035

⇑ Corresponding author. Tel.: +98 311 3915646; faxE-mail address: mmasoomi@cc.iut.ac.ir (M. Masoo

In this paper, two grafted copolymers, Glycidyl Methacrylate grafted polypropylene (PP) (PP-g-GMA) andMaleic Anhydride grafted PP (PP-g-MA) were used in PP reinforced with short poly(ethylene terephthal-ate) (PET) fibre composites. Transcrystallization (TC) of PP on PET fibres was investigated using a polar-ized optical microscope, which revealed no TC for either of the modified composites at the fibre–matrixinterface. Heat deflection temperature (HDT) results of GMA modified composites revealed moreenhancement than HDT of MA modified samples. The composite strength results showed enhancementfor both modified composites up to 10 wt.%, and this growth was bigger for GMA modified composites.The morphological analysis of GMA modified PP/PET composites pointed out a marked improvementof fibre dispersion and interfacial adhesion as compared to non-compatibilized PP/PET composites. Theresults of impact strength showed about 43% enhancement for 15 wt.% PET fibre composites. It was foundthat at low fibre percentages, using either of the modifiers reduces the impact strength a little in compar-ison to impact strength of the unmodified samples. According to linear elastic fracture mechanics LEFM,impact fracture toughness (Gc) and critical stress intensity factor (Kc) were evaluated for these compositesbased on the fracture energy obtained from impact tests.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Fibre-reinforced composite plastics offer a combination ofstrength, durability, stiffness, low weight, thermal stability andcorrosion resistance that has led to their adoption in a variety ofapplications. Thermoplastic-based composites are becoming morepopular in many application fields due to the possibility of combin-ing the toughness of thermoplastic polymers with the stiffness andstrength of reinforcing fibres [1]. Among the thermoplastic matri-ces, PP is one of the most used ones for short fibre compositesdue to economic reasons, ease of processing, environmental andworking security, and recyclability [1,2]. Glass and carbon fibrereinforced thermoplastic matrices are the most popular ones usedto produce short fibre reinforced PP; nonetheless, the tendency toregard these materials as non-recyclable and the common practiceto discard them in landfills has caused increasing environmentalconcerns. Besides, even if they are recycled, they show a degrada-tion of their mechanical performance [3]. It is well known that or-ganic textile fibres can be used to prepare polymer composites andit is possible to obtain good composites using PP with short organicfibres [1,4]. Poly(ethylene terephthalate) (PET) fibre could be a

ll rights reserved.

: +98 311 3912677.mi).

good option to reinforce PP. Since its introduction in 1953, PET fi-bres have progressively found new and interesting applications inplastics. Owing to its low density, PET fibre is lighter than cotton,wool and silk, and can mimic their properties. Besides, its low cost,high impact strength, high tenacity, high thermal stability, andmore importantly, recyclability make it effective to use in PP com-posites [1,2,5,6]. Therefore, PP/PET composites provide some spe-cific features, such as recyclability, ease of production, and lowcost. One major problem of PP/PET composites is that they arenot compatible, causing reduction in the final composite strengthdue to having weak fibre/matrix interaction [3,7]. To resolve thisproblem, chemical modification of matrix is usually applied in or-der to enhance the interaction at the fibre–matrix interface. Of allthe modifiers used in PP/PET composites, Maleic Anhydride (MA) isthe most common [2,5,7]. Glycidyl Methacrylate (GMA) is anotherinteresting modifier owing to its epoxy group, which is capable ofreacting with various other groups like hydroxyl, carboxyl, amine,and anhydride. GMA which can react with both hydroxyl and car-boxyl end groups of the PET fibre has not been used before in PP/PET composites. Furthermore, unlike MA, GMA does not produceside product of water through its chemical reactions by the PETchain end groups [8–12]. GMA reaction with PET end groups is de-picted in Fig. 1.

For composites based on semi crystalline polymers, their crys-tallinity is an important factor, which determines the stiffness of

Fig. 1. Schematic representation of reaction between PET end-groups and GMA moieties grafted onto PP backbone.

M. Asgari, M. Masoomi / Composites: Part B 43 (2012) 1164–1170 1165

the composite. Under appropriate conditions, a highly orientedlayer is developed at the fibre–matrix interface. This distinct mor-phology is called transcrystalline (TC) layer. PP matrix TC layer onthe PET fibre has been studied by many researchers [13–15].Embedding PET fibres into PP matrix can also increase thermal sta-bility of the matrix due to higher heat deflection temperature(HDT) of PET fibres, causing enhancement in the HDT of the resul-tant composite. Moreover, properly designed PP/PET compositescan also have a noticeable increase in impact strength. Workersin this area have managed to show satisfactory results in their im-pact tests [2,4–6].

In this paper, PP/PET fibre composites were prepared in pres-ence and absence of PP-g-GMA and PP-g-MA by melt impregnationtechnique. Morphological properties were investigated usingpolarized optical microscopy and scanning electron microscopy(SEM) techniques. Thermal studies such as DSC and HDT measure-ments were conducted and mechanical behaviours like tensile andimpact tests were also investigated. According to linear elasticfracture mechanics (LEFM) concept, Gc and Kc were measuredbased on the information obtained from impact results and drawnon the basis of fibre content.

2. Experimental

2.1. Materials

A commercial grade of PP under the trade name of C30S in powderform from Iran Petrochemical Co. was used. PP had the Melt Flow In-dex of 3–5 g/10 min (190 �C, 2.16 kg) and density of 0.9 g/cm3. PETfibre was a commercial grade of textile polyester (FOY1, tensilestrength 550 Mpa, tensile modulus 12,000 MPa, and 11.2 lm in diam-eter) provided by Polyacryle Company, Iran, chopped to the averagelength of 4 mm. PP-g-GMA was prepared in our laboratory by meltgrafting method in an internal mixer according to Parcella and Chion-na [8]. Mixing time, rotor speed, temperature, styrene/GMA molar ra-tio, Dicumyl Peroxide (DCP) and GMA amounts were 5 min, 60 RPM,190 �C, 1, 0.5, and 9 Phr2, respectively.

PP-g-MA (MFI = 150–200 g/10 min at 230 �C and 2.16 Kg) wasused as the second compatibilizer which was provided by OREVACcorporation under the trade name of CA100.

2.2. Composite preparation

PET fibres were dried in an oven at 100 �C for 4 h. Three types ofpre-pegs of PP/PET, WO (without compatibilizer), WG (with PP-g-GMA), and WMA (with PP-g-MA) with fibre loads of 5, 10, 15, 20,and 30 wt.% were mixed in an internal mixer at 180 �C and60 RPM for about 10 min to ensure the proper wetting of PET fibresby PP melt. The amount of campatibilizers in each run was 10 Phr.

1 FOY, fully oriented yarn.2 Phr, parts per hundred resin.

Then, pre-pegs were moulded by hot press technique at 180 �C and100 bar.

2.3. Composite characterization

2.3.1. Morphological studyIn order to study crystallinity of composites, a Leica polarized

optical microscope (DMRX model) was used. SEM technique(AIS2100 model microscope from Seron Technology company)was applied to study the sample fracture surfaces and fibre–matrixinterface.

2.3.2. Thermal testsDSC tests were performed at the heating rate of 10 �C/min using

DSC 200F3, NETZSCH. Heat deflection temperature (HDT) test is thetemperature at which the material deflects by 0.25 mm at an ap-plied force, where the specimen is placed in a three-point bendingmode. HDT of PP/PET composites was measured according to ASTMD648 by a Ray–Ran testing machine, and bars with dimensions of127 � 12 � 3 mm3 were prepared. The test was conducted on threesamples of each specimen with the load applied at its centre to givemaximum fibre stresses of 1.82 MPa.

2.3.3. Mechanical behaviourTensile properties of the samples were determined using a Uni-

versal testing machine (Testometric) at the cross head speed of5 mm/min (ASTM D638). Impact properties were measuredaccording to ASTM D256 using a ZWICK/Roel impact testing ma-chine (L-HIT, HIT5.5P model). Bars used in the impact tests hadthe dimensions of 55 � 10 � 10 mm3.

2.4. Gc and Kc measurement

Short PET fibres are usually added to PP to improve the impactstrength of the composite as a result of enhancement of its impactfracture toughness [2,5,7]. The impact fracture toughness of amaterial is usually evaluated by means of impact test: the simplestbeing the notched Charpy and Izod impact tests. They provide thetotal energy (Uc) consumed during the whole impact fracture pro-cess. Even though polymeric materials display viscoelasticity whentested in a tensile mode, they tend to fail in a brittle manner underimpact due to the high loading rate exerted on the test pieces. Theeffect is further exaggerated by introducing a razor-sharp crack inthe sample, minimizing the plastic zone ahead of the crack tip andextending the application of linear elastic fracture mechanics(LEFM) to this group of materials. Thus, toughness parameters likethe stress intensity factor and the critical strain energy release rate(Kc and Gc respectively) can be determined [16]. In recent years,impact testing of plastics has been rationalized to a certain extentby the use of fracture mechanics and the most successful resultshave been achieved by assuming that LEFM assumptions (bulk lin-ear elastic behaviour and presence of sharp notch) apply during the

Fig. 2. Specimen geometry for the Charpy impact fracture test.

1166 M. Asgari, M. Masoomi / Composites: Part B 43 (2012) 1164–1170

Izod and Charpy testing of a plastic [17–20]. The toughness, Gc, ofthe material is expressed as follows:

Gc ¼F2

c

2B@C@a

ð1Þ

As it was implied, Gc is a material property which is referred toas the toughness or critical strain energy release rate. It is the en-ergy required to effectively increase the crack length by unit lengthin a piece of material of unit width. Fc, a, B, and C are applied force,crack length, specimen thickness, and compliance of the material,respectively. This is a very important relationship as it permitsthe fundamental material property, Gc, to be calculated from thefracture force, Fc, and the variation of compliance with cracklength. So, using Eq. (1) and introducing the material width, D

Gc ¼Uc

BDhð2Þ

where h = ((l/C)(@C/@a))�1. This is a geometrical function which canbe evaluated for any geometry. The dimensions used in this re-search were 55 � 10 � 10 mm3 (L � B � D) according to Fig. 2 withthe support span (S) of 40 mm. The notch depth and notch anglemade on these samples were 1 mm and 45�, respectively. For thisspecimen dimension, h value was calculated beforehand based onthe finite element analysis and its value was 0.781 [19].

Irwin developed the technique for engineering materials andexamined the equations that had been developed for the stressesin the vicinity of an elliptical crack in a large plate. The stress inten-sity factor is a means of characterizing the elastic stress distribu-tion near the crack tip but in itself has no physical reality. Thecritical stress intensity factor is sometimes referred to as the frac-ture toughness and will be designated by Kc and it is related to Gc

by the following equation:

Kc ¼ ðEGcÞ1=2 ð3Þ

In Eq. (3), E is the tensile modulus of the specimen.

3. Results and discussion

The presence of interface interactions in the modified compos-ites is supported by the variation of mixing torque. As shown inFig. 3, there is a melting peak and afterward, mixing torque getsto a stabilized value. It is clear from Fig. 3 that WG samples havehigher final torque value in comparison with WO samples at thesame fibre loads, which is attributed to formation of chemicalbonds at the fibre–matrix interface and, therefore, larger interac-tions of PP/PET and higher viscosity. Small torque variations aftermelting peak in Fig. 3b are attributed to the chemical interactionsformed between epoxy groups of GMA modified PP matrix and PETfibre chain end groups at the interface which is common in reactivesystems [21,22].

As implied earlier, when a fibre is embedded into a thermoplasticmelt it may act as a nucleating site for the growth of TC at the fibre ma-trix interface. TC is a distinctive morphology which is mainly due tocolumnar growth of PP crystallites on the PET fibre surface [2]. In or-der to study TC at PP/PET fibre interface, polarized optical micro-graphs of PP with 5 wt.% of PET fibres were prepared, as shown inFig. 4. Microscopic analysis of the PP/PET composites revealed notranscrystallinity of the matrix around the fibres for WG and WMAsamples; however, as shown in Fig. 4a, around some parts of PETfibres TC can be seen which raises the amount of crystallinity and stiff-ness of the WO samples. Application of a compatibilizer like PP-g-GMA or PP-g-MA causes physical–chemical changes at the fibre/matrix interface which deters formation of transcrystalline layer atthe interface and sparks changes in the crystallinity of the composite.

DSC thermograms of samples were investigated in order tostudy the crystallinity of the system and the difference betweenthe crystallinity and transcrystalline layer of PP/PET and those ofPP/PP-g-MA/PET, and PP/PP-g-GMA/PET, which are shown inFig. 5a–c. The presence of transcrystallinity can be clearly observedin the endothermic peak of unmodified PP/PET, which shows abroad peak having a total DH value of 120.1 J/g. This broad peakis divided into two peaks; the smaller peak corresponds to trans-crystalline zone (fast crystallization process) giving rise to smallspherulites along the fibre surface while the bigger peak corre-sponds to big spherulites away from fibres surface. Thus a totalof 120.1 J/g raises the crystallinity in PP. On the other hand, a singleendothermic peak is observed for WMA and WG samples having aDH of 114.9 J/g and 119.1 J/g, respectively. This clearly indicatesthat the presence of MA and GMA prevents the formation of trans-crystalline growth of PP spherulites on the surface of PET fibre [2].It can also be inferred that the GMA modified sample has highercrystallinity than WMA composite, which implies the better roleof MA in reducing the amount of crystallinity than GMA.

HDT results showed continuous increment versus fibre load forall types of composites. HDT of neat PP and its composites areshown in Table 1. The HDT value of PP was 119 �C and was in-creased about 16 �C by the incorporation of 30 wt.% of PET fibres.By adding fibres, it can be seen that HDT values of WO samplesare a little greater than HDT of the modified ones. This is explainedby the crystallinity differences of samples which were bigger forWO composites. Furthermore, WG samples’ HDTs were bigger thanthose of WMA composites, which indicates having higher stiffnessand crystallinity of GMA modified composites. It can also be no-ticed that HDT growth is slower at higher fibre weight percentages.

The results of tensile strength as a function of fibre concentra-tion are shown in Fig. 6. It is clear that strength of WO samplescontinuously decreases by adding PET fibres.

Nevertheless, modified composites strengths show a smallenhancement up to 10 wt.% of fibres and then start to decrease.The strength growth was bigger for WG samples (about 3 MPa).The results also shows that by adding compatibilizers, reductionrate of PP/PET composite strength changes, which is less for WGones. Some researchers in this area believe that voids and stressconcentrations enhancement at higher fibre percentages are themain reasons for the composite strength reduction [5,15]. SEM val-ues of tensile fracture surfaces of 15 wt.% of fibre composite areshown in Fig. 7, which presents a good dispersion of fibre intothe PP matrix. As seen from the picture, PET fibres are flexibleand have random-in-plane orientations. So, there is a good possi-bility for formation of fibre entanglements at higher fibre loadsand reduction of fibre wetting by the melt matrix at the impregnat-ing stage, which decreases the amount of composite strength [23].Moreover, it can be inferred from Fig. 7a that there are lots of neatfibres pulled out of the matrix and scattered on the surface, repre-senting weak interface in WO composite. On the other hand, mod-ified samples have stronger interfaces due to having traces of

Fig. 3. Amount of mixing torque variation versus time as a function of fibre loads for (a) WO samples; (b) WG samples.

Fig. 4. Optical microscopy showing morphology about fibres in 5 wt.% PET fibre (a) WO; (b) WMA; and (c) WG composites: 500�.

M. Asgari, M. Masoomi / Composites: Part B 43 (2012) 1164–1170 1167

matrix on the PET fibres which is more conspicuous for WG ones,as presented in Fig. 7b and c. According to tensile SEM pictures,it is deduced that at low fibre fractions, fibres play the role of rein-forcement to a critical fibre load [6,15,24] while at higher fibre per-centages, there will be more entanglements between the fibresduring the moulding process, which lead to voids and poor bond-ing between the fibres and the matrix and decrement of compositestrengths.

Fig. 8 shows the results of the strain at break measurements. It isnoted that the incorporation of PET fibres dramatically decreasesthis parameter for all compositions with PET fibres in relation to purePP. This behaviour is typical for fibre reinforced composites [6].There is a significant difference in strain at break for composites withand without compatibilizer up to 15 fibre wt.%. The immediate steep

decline in strain at break with fibre addition is obvious, because PETfibres have low strain at break and restrict the polymer moleculesflowing past one another. Thus, it is evident that by adding PP-g-GMA and PP-g-MA to the matrix, strains at break show more dec-rement because of strengthening of the fibre/matrix adhesion. It canbe seen from Fig. 8 that strains at break of WG samples are reducedmore than strains at break of WMA ones, which is due to strongerinterface caused by PP-g-GMA. For 20 and 30 wt.% of fibre compos-ites, this parameter is less for WOs than those of modified onesdue to the drastic increase of defects in the bulk of composite.

The results of Charpy impact strength measurements are shownin Fig. 9. It can be observed from the figure that all of the WO,WMA, and WG composites show an increase of impact strengthas compared to pure PP (741 kJ/m2). In case of WO samples, the

Fig. 5. DSC curves for: (a) PP with 5 wt.% PET (WO); (b) PP with 5 wt.% PET (WMA);(c) PP with 5 wt.% PET (WG).

Table 1HDT values of WO, WMA, and WG PP/PET composites.

Fibre (wt.%) HDT (�C)

WO WMA WG

0 119 ± 0.6 – –5 126.5 ± 0.4 124.2 ± 0.5 126 ± 0.4

10 133.8 ± 0.9 128.3 ± 0.8 133.5 ± 0.715 134.8 ± 0.9 129.7 ± 0.8 135.1 ± 0.320 135 ± 0.5 130.5 ± 0.7 135.7 ± 0.730 135.1 ± 0.5 132 ± 0.4 135.8 ± 0.5

Fig. 6. Tensile strengths vs. fibre weight percent for WO, WMA, and WG PP/PETcomposites.

Fig. 7. SEM micrographs of tensile fracture surfaces of (a) WO, (b)

Fig. 8. Strain at break in function of composite % of PET fibre for WO, WMA, and WGsamples.

Fig. 9. Charpy impact strength of WO, WMA, and WG samples in function ofcomposite wt.% of PET fibre.

1168 M. Asgari, M. Masoomi / Composites: Part B 43 (2012) 1164–1170

impact strength increases up to 15 fibre wt.% (43% increase of im-pact strength) and their values are greater than impact strengths ofthe modified samples due to having weaker interface and produc-ing greater amount of wasting energy mechanisms like fibre pull-out and fibre de-bonding during the impact test, as illustrated inFig. 10. The impact strengths of WMA composites are a little great-er than WG samples due to having weaker interface. In the case ofWO composites, void concentration increases at high fibre concen-trations as a result of incompatibility of fibre and the matrix andtherefore, modified composites show greater impact strength val-ues. According to Saujanya and Radharkrishnan [2], an increasein the impact strength of PP/PET composites can also be explained

WMA, and (c) WG samples containing 15 wt.% of fibre: 300�.

Fig. 10. SEM micrographs of impact fracture surfaces of (a) WO, (b) WMA, and (c) WG samples containing 10 wt.% of fibre.

Table 2Values of Gc and Kc for WO, WMA, and WG composites determined using LEFM.

Fibre (wt.%) Young modulus (MPa) Gc (kJ/m2) Kc (MN m�3/2)

WO WMA WG WO WMA WG WO WMA WG

0 520 520 520 20.45 20.45 20.45 3.26 3.26 3.265 570 567 574 23.30 23.18 22.41 3.64 3.63 3.59

10 605 570 600 26.89 25.61 25.48 4.03 3.82 3.9115 680 660 675 29.45 29.19 29.07 4.48 4.39 4.4320 762 746 800 28.81 28.43 28.43 4.69 4.61 4.7730 820 820 860 21.77 26.89 27.53 4.23 4.70 4.87

M. Asgari, M. Masoomi / Composites: Part B 43 (2012) 1164–1170 1169

based on spherulite size and defects or stress points in the thermo-plastic material containing excess fibre. They claim that for allthese samples, the size of spherulites is considerably small as com-pared to that in pure PP. Owing to smaller size of spherulite, theflexibility is higher and hence the impact strength is also high.

Scanning electron micrographs of impact fractured surfaces ofPP/PET composites are presented in Fig. 10. The WO fractured sur-face (Fig. 10a) shows that there is hardly any adhesion at the fibre/matrix interface since the fibres are pulled out from the polymermatrix without leaving any sign and the fibres themselves showa very clean surface, showing the fibre pull-out energy wastingmechanism while fracturing. However, as deduced from Fig. 10c,in the case of the GMA modified PP matrix, a considerableimprovement of the adhesion at the interface is observed and thereare hardly any voids on the fractured surface, which indicates thatthe fibres are so well trapped by the polymer that fibre pull-outconsiderably decreases. By comparing Fig. 10b and c, it is shownthat pulled out fibres happen to be more in WMA composite thanin WG sample fractured surface, explaining the difference of im-pact strength between these two composite types.

Table 2 shows Gc and Kc values for diversity of fibre weight per-centages for different types of composites using Eqs. (2) and (3). Gc

values follow the same trend as observed in impact test results. Tocalculate impact fracture toughness and stress intensity factor,Young modulus values of the samples obtained from stress–straincurve are also listed in Table 2.

It is obvious that by increasing the amount of fibre, there is agradual increase in the Gc values (�40%), thereafter, they start todecrease, indicating that PET fibres play an important role intoughening of PP/PET composites up to a fibre load (15 fibrewt.%). The amounts of Gc at lower fibre percentages (up to15 wt.% of fibres) are greater than Gc of modified ones due to themore fibre pull-out and fibre de-bonding energy wasting mecha-nisms which raises toughness of the WO composites. Because ofincreasing void concentrations at higher fibre loads such as 20 or30 wt.%, Gc and Kc values of WO samples drop below those of mod-ified ones and show a noticeable reduction. Greater amount of Gc

and Kc of compatibilized composites at higher fibre loads can beexplained by stronger interaction of fibre–matrix which sparks lessamount of voids and weakness in the modified composites.

Owning to the fact of dissipating a major amount of exerted energythrough fibre de-bonding and fibre pull-out energy wasting mech-anisms at the PP/PET interface (revealed by SEM pictures atFig. 10), there is a constant increase in Kc values of modified sam-ples. This parameter was greater for those of WG ones due to stron-ger interaction between fibre and the matrix caused by PP-g-GMA,which also cause less amount of voids at higher fibre contents.

4. Conclusion

Based on the results obtained, it is concluded that by adding10 Phr of compatibilizer to PP/PET composites, not only can wemaintain or increase the PP/PET composite strength, which wasmore for WG ones, but also it is possible to get improved impactproperties. There were no TCs in the modified samples; however,it was observed that TC layers were formed around some fibreswhich helped raise the amount of crystallinity. DSC thermogramsshowed bigger melting area of WO sample with a small peak thatbelongs to TC layers. It was also revealed that melting peak area ofGMA modified composite was bigger than that of WMA. HDT re-sults of GMA modified composites showed a satisfactory growthby adding PET fibres. Toughness and stress intensity factorsshowed enhancements due to the emergence of energy wastingmechanisms such as fibre pull-out mechanisms.

Acknowledgement

The authors thank the Polyacryle Company for providing thePET fibres for this work. We also grateful to Noavaran Baspar Com-pany for supporting us using their laboratory equipments.

References

[1] Lopez MA, Manchado MA. Thermal and dynamic mechanical properties ofpolypropylene and short organic fibre composites. Polymer 2000;4:7761–7.

[2] Saujanya C, Radharkrishnan S. Structure development and properties of PETfibre filled PP composites. Polymer 2001;42:4537–48.

[3] Papanicolaou GC, Karagiannis D, Bofilios DA, Van Lochem JH, Henriksen C, LundHH. Impact strength of recycled thermoplastic composites subjected tocorrosive environment. Polym Compos 2008;29:1026–35.

[4] Abraham TN, George KE. Studies on recyclable nylon-reinforced PP composites:effect of fibre diameter. J Thermoplast Compos Mater 2009;22:5–20.

1170 M. Asgari, M. Masoomi / Composites: Part B 43 (2012) 1164–1170

[5] Satapathy S, Nando GB. Mechanical properties and fracture behavior of shortPET fibre-waste polyethylene composite. J Reinf Plast Compos2008;27:967–84.

[6] Santos P, Pezzin SH. Mechanical properties of polypropylene reinforced withrecycled-PET fibres. J Mater Process Technol 2003;143(144):517–20.

[7] Hahm M, Kim CH, Ryu J. A study on polypropylene and surface modified PETfibre composites. Polym Korea 2008;32:7–12.

[8] Parcella M, Chionna D. Reactive compatibilization of blends of PET and PPmodified by GMA grafting. Macromol Symp 2003;198:161–71.

[9] Cartier H, Hu G. Styrene-assisted melt free radical grafting of GMA onto pp. JAppl Polym Sci 1999;71:125–33.

[10] Huang H, Liu NC. Nondegradative melt functionalization of polypropylenewith glycidyl methacrylate. J Appl Polym Sci 1998;67:1957–63.

[11] Cartier H, Hu G. Styrene-assisted free radical grafting of glycidyl methacrylateonto polyethylene in the melt. J Appl Polym Sci 1998;36:2763–74.

[12] Chandranupap P, Bhattacharya S. Reactive processing of polyolefins with MAHand GMA in the presence of various additives. J Appl Polym Sci2000;78:2405–15.

[13] Wang C, Liu CR. Transcrystallization of polypropylene composites: nucleatingability of fibres. Polymer 1999;40:289–98.

[14] Mukhopadhyay S, Deopura BL, Alagiruswamy R. Interface behavior inpolypropylene composites. J Thermoplast Compos Mater 2003;16:479–94.

[15] Houshyar S, Shanks RA, Hodzic A. The effect of fibre concentration onmechanical and thermal properties of fibre-reinforced polypropylenecomposites. J Appl Polym Sci 2005;96:2260–72.

[16] Tam WY, Cheung T, Li RKY. An investigation on the impact fracturecharacteristics of EPR toughened polypropylene. Polym Test 1996;15:363–79.

[17] Tam WY, Cheung T, Li RKY. Impact properties of glass fibre/impact modifier/polypropylene hybrid composites. J Mater Sci 2000;35:1525–33.

[18] Coppola F, Greco R, Ragosta G. Isotactic polypropylene/EPDM blends: effect oftesting temperature and rubber content on fracture. J Mater Sci1986;21:1775–85.

[19] Crawford RJ. Plastics engineering. Oxford: Butterworth-Heinemann; 1998.[20] Anderson TL. Fracture mechanics: fundamentals and applications. New

York: CRC; 1995.[21] Saleem M, Baker WE. In situ reactive compatibilization in polymer blends:

effects of functional group concentrations. J Appl Polym Sci 1990;39:655–78.[22] Pracella M, Chionna D, Pawlak A, Galeski A. Reactive mixing of PET and PET/PP

blends with glycidyl methacrylate-modified styrene-b-(ethylene-co-olefin)block copolymers. J Appl Polym Sci 2005;98:2201–11.

[23] Miller A, Gibson AG. Impregnation techniques for thermoplastic matrixcomposites. Polym Polym Compos 1996;4(7):459–81.

[24] Agarwal BD, Broutman LJ, Chandrashekhara K. Analysis and performance offibre composites. New Jersey: John Wiley & Sons; 2006.