Peroxide‐catalyzed swell grafting of maleic anhydride onto polypropylene

A new grafting method was developed to incorporate maleic anhydride directly onto solid‐state polypropylene powders. Maleic anhydride grafts altered the nonpolar characteristics of polypropylene so that much better mixing was achieved in blends and composites of polypropylene with many other polymers and fillers. Maleic anhydride was grafted onto polypropylene by the peroxide‐catalyzed swell grafting method, with a maximum extent of grafting of 4.60%. Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, tensile testing, and impact testing were used to characterize the isotactic polypropylene (iPP), maleic anhydride grafted polypropylene (MAH‐g‐iPP), and (isotactic polypropylene)/(calcium carbonate) composites (iPP/CaCO₃). The crystallinity and heat of fusion of the MAH‐g‐iPP decreased as the extent of grafting increased. The mechanical properties of the CaCO₃ filled polypropylene were improved by adding MAH‐g‐iPP as a compatibilizing agent. The dispersion of the fillers in the polymer matrix and the adhesion between the CaCO₃ particles and the polymer matrix were improved by adding the compatibilizer.     

Effect of maleic anhydride grafted polypropylene on the mechanical and morphological properties of chemically modified short‐pineapple‐leaf‐fiber‐reinforced polypropylene composites

With the rising cost of petroleum‐based fibers, the utilization of plant fibers in the manufacture of polymer–matrix composites is gaining importance worldwide. The scope of this study was to examine the perspective of the use of pineapple leaf fibers (PALFs) as reinforcements for polypropylene (PP). These fibers are environmentally friendly, low‐cost byproducts of pineapple cultivation and are readily available in the northeastern region of India. Here, both untreated and treated pineapple fibers were used. Maleic anhydride grafted polypropylene (MA‐g‐PP) was used as a compatibilizing agent. The polymer matrix of PP was used to prepare composite specimens with different volume fractions (5–20%) of fibers by the addition of 5% of MA‐g‐PP. These specimens were tested for their mechanical properties, and additional assessments were made via observations by scanning electron microscopy, thermogravimetric analysis, and IR spectroscopy. Increase in the impact behavior, flexural properties, and tensile moduli of the composites were noticed, and these were more appreciable in the treated fibers mixed with MA‐g‐PP. PALF in 10 vol % in PP mixed with MA‐g‐PP was the optimum and recommended composition, where the flexural properties were the maximum. The impact strength and the tensile modulus were also considerably high. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of silane‐grafted polypropylene on the mechanical properties and crystallization behavior of talc/polypropylene composites

Talc‐filled polypropylene (PP) composites coupled with silane‐grafted polypropylene (PP‐g‐Si) were prepared. Effect of PP‐g‐Si on the mechanical properties, crystallization, and melting behavior of PP composites was investigated. Compared with the uncoupled composites, the mechanical properties of Talc/PP composites coupled with a small amount of PP‐g‐Si were increased to some extent. Meanwhile, PP‐g‐Si can promote crystallization rate and increase crystallization temperature of PP in the composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2974–2977, 2000     

Effect of maleic‐anhydride‐grafted polypropylene as a compatibilizer on the properties of polypropylene/(modified carbon black) composites

Maleic‐anhydride‐grafted polypropylene (PP‐g‐MAH) was added, as a compatibilizer, to polypropylene (PP) composites filled with a hindered phenol and modified carbon black (CB). The interaction between the modified CB and PP‐g‐MAH, as proved by Fourier transform infrared spectroscopy, had a beneficial effect on the mechanical properties of the PP/(modified CB) composites and prevented the sharp decrease of the mechanical properties of these composites at higher filler concentration. The storage modulus of PP/(modified CB) was increased significantly by the incorporation of PP‐g‐MAH, especially when the temperature was lower than 0°C. When the content of PP‐g‐MAH was 5 wt% and the loading of the modified CB was 2 wt%, the best tensile strength was obtained. The system showed the best flexural strength and impact strength when the loading of the modified CB was 1 wt%. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Mechanical,thermal, and morphological properties of maleic anhydride‐g‐polypropylene compatibilized and chemically modified banana‐fiber‐reinforced polypropylene composites

Composites were prepared with chemically modified banana fibers in polypropylene (PP). The effects of 40‐mm fiber loading and resin modification on the physical, mechanical, thermal, and morphological properties of the composites were evaluated with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Infrared (IR) spectroscopy, and so on. Maleic anhydride grafted polypropylene (MA‐g‐PP) compatibilizer was used to improve the fiber‐matrix adhesion. SEM studies carried out on fractured specimens indicated poor dispersion in the unmodified fiber composites and improved adhesion and uniform dispersion in the treated composites. A fiber loading of 15 vol % in the treated composites was optimum, with maximum mechanical properties and thermal stability evident. The composite with 5% MA‐g‐PP concentration at a 15% fiber volume showed an 80% increase in impact strength, a 48% increase in flexural strength, a 125% increase in flexural modulus, a 33% increase in tensile strength, and an 82% increase in tensile modulus, whereas the heat deflection temperature increased by 18°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of m‐isopropenyl‐α,α‐dimethylbenzyl isocyanate grafted polypropylene on the interfacial interaction of wood‐flour/polypropylene composites

In this article, the effects of m‐isopropenyl‐α,α‐dimethylbenzyl isocyanate grafted polypropylene (m‐TMI‐PP) on the interfacial interaction of wood‐flour/polypropylene (WF/PP) were investigated by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry, dynamic rheological analysis, and mechanical properties tests. The experimental results demonstrated that m‐TMI‐PP greatly improved the interfacial interaction between WF and PP. According to the DSC results, m‐TMI‐PP made the crystallization temperature and the crystallization degree of PP in WF/m‐TMI‐PP/PP decrease when compared with WF/PP composite without m‐TMI‐PP, but it was still higher than pure PP. These results demonstrated that WF presented the nucleate effect for the crystallization of PP and m‐TMI‐PP improved the interfacial adhesive, which restrained the mobility of PP chain. The rheological analysis indicated that the complex viscosity, storage, and loss modular of WF/PP composite increased, and the tan δ decreased with the addition of m‐TMI‐PP. This was attributed to the strong improvement effects of m‐TMI‐PP on the interfacial interaction of the composites, and was further confirmed by the mechanical properties tests and SEM analysis of the composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Silica‐filled polypropylene composites: The effect of ethylene diamine dilaurate and maleic anhydride grafted polypropylene on mechanical properties,water absorption,morphology, and thermal properties

The effect of two compatibilizers, i.e. ethylene diamine dilaurate (EDD) and maleic anhydride grafted polypropylene (MAPP) on the mechanical properties, water absorption, morphology, and thermal properties of silica‐filled polypropylene (PP/Sil) composites were studied. The results show that the tensile, impact and flexural strengths (up to 2 php), Young's modulus, and elongation at break (Eb) increased with increasing EDD content. However, increasing MAPP content increases the tensile strength, Young's modulus, impact and flexural strengths, and water absorption resistance. At a similar compatibilizer content, EDD exhibits higher Eb, impact and flexural strengths but lowers tensile strength, Young's modulus, and water absorption resistance compared with MAPP. Scanning electron microscopy study of tensile fractured surfaces exhibits the evidence of better silica‐PP adhesion with MAPP and EDD compared with the similar composites but without compatibilizer. Fourier transform infra red spectra provide an evidence of interaction between EDD or MAPP with PP/Sil composites. Termogravimetry analysis results indicate that the addition of EDD or MAPP slightly increases the thermal stability of PP/Sil composites. Differential scanning calorimetry also indicates that PP/Sil composites with EDD or MAPP have higher heat fusion (ΔH_f(com)) and crystallinity (X_com) than similar composites but without compatibilizer. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Preparation of toughened polypropylene‐g‐poly(butyl acrylate‐co‐acrylated castor oil) by suspension grafting polymerization

Butyl acrylate (BA) with acrylated castor oil (ACO) was grafted onto porous polypropylene (PP) granules by grafting polymerization. Crosslinked copolymer microdomains which functioned as rubber phase to improve the toughness of PP were filled into the pores of PP granules. The sizes of crosslinked copolymer microdomains were controlled in the range of 0.1–1 μm in PP matrix. The results of fourier transform infrared spectroscopy and scanning electron microscope of PP‐g‐(BA‐co‐ACO) after extracted by acetone confirmed that BA and ACO were grafted onto PP successfully. The effects of comonomer ratio, initiator content and comonomer content on grafting percentage (GP) and grafting efficiency (GE) were investigated. The GP of PP‐g‐(BA‐co‐ACO) could be up to 21.3% with the comonomer content increasing to 25%. The crosslinked copolymer decreased the melting flow index and the relative crystallinity of PP. Dynamic mechanical thermal analysis showed that the glass transition temperature of PP decreased slightly from 22°C to 15°C. The addition of 5% comonomer content led to an increase of notched impact strength from 1.96 to 3.81 kJ/m² (nearly doubled) and a marginal decrease in the tensile strength of PP. Then with further addition of comonomer, the notched impact strength increased to 8.98 kJ/m² while the tensile strength was 29.37 MPa. POLYM. ENG. SCI., 58:86–93, 2018. © 2017 Society of Plastics Engineers     

Interfacial modification of single‐walled carbon nanotubes for high‐loading‐reinforced polypropylene composites

In this article, we present a strategy for fabricating polypropylene (PP)/polypropylene‐regrafted single‐walled carbon nanotube (PP‐re‐g‐SWNT) composites with a high loading of single‐walled carbon nanotubes (SWNTs; 20 wt %). The PP‐re‐g‐SWNTs were characterized by X‐ray photoelectron, Fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis (TGA). The PP‐re‐g‐SWNTs showed excellent interfacial adhesion and dispersion. Furthermore, PP molecules, about 72 wt % by mass, were homogeneously bonded onto the surface of the SWNTs according to TGA. In this hybrid nanocomposite system, the PP‐re‐g‐SWNTs were covalently integrated into the PP matrix and became part of the conjugated network structure (as evidenced by differential scanning calorimetry and dynamic mechanical analysis) rather than just a separate component. Accordingly, the PP/PP‐re‐g‐SWNT composites presented obvious improvements in mechanical properties and conductivity (from 10^?10 to 10^?2). Most importantly, the tensile and flexural strength of the PP/PP‐re‐g‐SWNT composites did not exhibit an obvious downturn with the addition of 20 wt % SWNTs; this was contrary to documented results. We believe that these new observations were due to the novel structure of the PP‐re‐g‐SWNTs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39817.     

Effects of clay contents on the dynamic mechanical and rheological properties of polypropylene/MAH‐g‐POE/clay composites

A series of polypropylene/maleic anhydride grafted polypropylene octane elastomer (MAH‐g‐POE)/clay (PPMC) nanocomposites were prepared with a novel compatilizer MAH‐g‐POE and different contents of octadecyl amine modified montmorillonite, and the effects of clay contents on the dynamic mechanical and rheological properties of these PPMC composites were investigated. With clay content increasing, the characteristic X‐ray diffraction peak changed from one to two with intensity decreasing, indicating the decreasing concentration of the intercalated clay layers. The gradual decrease of crystallization temperature of PPMC composites with the increase of clay loading should be attributed to the preferred intercalation of MAH‐g‐POE molecules into clay interlayer during blending, which is also reflected by scanning electron microscopy observations. By evaluating the activation energy for the glass transition process of MAH‐g‐POE and polypropylene (PP) in the PPMC composites, it is found that clay intercalation could cause the restriction effect on the glass transition of both MAH‐g‐POE and PP, and this restriction effect appears stronger for PP and attained the highest degree at 5 wt % clay loading. The melt elasticity of PP could be improved apparently by the addition of MAH‐g‐POE, and 5 wt % clay loading is enough for further enhancing the elastic proportion of PP. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Study of multi‐monomer melt‐grafting onto polypropylene in an extruder

Free‐radical melt‐grafting of the dual‐monomer systems glycidyl methacrylate–styrene (GMA‐St) and hydroxyethyl methacrylate–styrene (HEMA‐St) onto polypropylene (PP) has been studied using a single‐screw extruder. For single monomer grafting systems, degradation of PP was unavoidable and deterioration of the mechanical properties of the grafted PP subsequently occurred because of β‐scission of PP chains during the free‐radical melt‐grafting process. However, for the dual‐monomer systems, it is shown that the addition of styrene as a comonomer can significantly enhance the GMA or HEMA grafting levels on PP and reduce the extent of β‐scission of PP backbone. It has been found that the grafting degree of dual‐monomer melt‐grafted PP, such as PP‐g‐(GMA‐co‐St) or PP‐g‐(HEMA‐co‐St), is about quadruple that of single‐monomer grafted PP for the same monomer and dicumyl peroxide concentrations. Moreover, the melt flow rate of the dual‐monomer grafted PP is smaller than that of the unmodified PP. Hence, PP not only was endowed with higher polarity, but also kept its good mechanical properties. © 2000 Society of Chemical Industry     

Crystallization behavior of PP/PP‐g‐MAH/GFR PA66 blends: Establishment of their continuous‐cooling‐transformation of relative crystallinity diagrams

Polypropylene/polypropylene‐grafted‐maleic anhydride/glass fiber reinforced polyamide 66 (PP/PP‐g‐MAH/GFR PA 66) blends‐composites with and without the addition of polypropylene‐grafted‐maleic anhydride (PP‐g‐MAH) were prepared in a twin screw extruder. The effect of the compatibilizer on the thermal properties and crystallization behavior was determined using differential scanning calorimetry analysis. The hold time was set to be equal to 5 min at 290°C. These conditions are necessary to eliminate the thermomechanical history in the molten state. The crystallization under nonisothermal conditions and the plot of Continuous‐Cooling‐Transformation of relative crystallinity diagrams of both PP and PA 66 components proves that PP is significantly affected by the presence of PP‐g‐MAH. From the results it is found that an abrupt change is observed at 2.5 wt % of PP‐g‐MAH as a compatibilizer and then levels off. In these blends, concurrent crystallization behavior was not observed for GFR PA66. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1620–1626, 2007     

Surface functionalization of polypropylene‐bearing isocyanate groups in solid state and their cyclotrimerization with diisocyanates

Solid‐state graft polymerization of 3‐isopropenyl‐α,α′‐dimethylbenzene isocyanate (TMI) onto the surface of polypropylene beads was carried out in a triethylborane/oxygen redox system. Chemical structures were characterized using attenuated total reflectance–Fourier transform infrared spectroscopy. Results showed that TMI was successfully grafted because of the appearance of an ? NCO absorption peak at 2255 cm^?1. The emergence of oxygen and nitrogen elements detected by EDS and XPS also demonstrated the existence of isocyanate group on PP‐grafted. The grafting ratio of TMI to polypropylene was examined using 9‐(methylamino‐methyl)anthracene (MAMA) as an intermediate substance. The fluorescent property of MAMA before and after reaction was characterized to guarantee interaction between MAMA and isocyanate. Thermal properties were examined using differential scanning calorimetry–thermogravimetric analysis. Results indicated that melting temperature (T_m) of pure PP was 168^oC, while the PP‐grafted decreased to 164^oC. Meanwhile, decomposition temperature (T_d) decreased with increased grafting ratio for about 8 to 15^oC; however, when styrene was introduced, T_m increased probably because of the stabilizing effect on macromolecular radicals and the suppression effect on chain degradation. Besides, the cyclotrimerization of isocyanates on the grafted polymer chain was further conducted to prepare thermally stable isocyanurate composite materials, remedying the T_d loss of PP‐g‐TMI by improving for 10^oC appropriately. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42186.     

Mechanical performance and flame retardancy of polypropylene composites containing zeolite and multiwalled carbon nanotubes

Intumescent‐flame‐retarded polypropylene (PP‐IFR) composites were prepared by the incorporation of methyl hydrogen siloxane treated ammonium polyphosphate and dipentaerythritol in a twin‐screw extruder. The effects of zeolite (Z), multiwalled carbon nanotubes (CNTs), and maleic anhydride grafted polypropylene on the flame retardancy, mechanical properties, and thermal stability of PP‐IFR were investigated. The addition of Z and CNT promoted the flame retardancy of PP‐IFR, and the highest limited oxygen index was 35.6%, obtained on PP‐M‐IFR‐2–Z, for which the heat‐release rate, total heat release, and smoke production rate based on cone calorimetry analyses decreased by 45.0, 51.0, and 66.3%, respectively, in comparison with those values of the PP‐IFR composites. Additionally, scanning electron microscopy analyses showed that there was a good interface interaction between the polypropylene matrix and additives. The flexural, tensile, and impact strengths of the PP‐IFR composites were improved significantly with the incorporation of CNT. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42875.     

Synthesis of a new compatibilisant agent PVC‐g‐MA and its use in the PVC/alfa composites

The main objective of this research was to synthesize a new compatibilisant agent (PVC‐g‐MA), which was grafted from the maleic anhydride on the PVC chains. The presence of maleic anhydride grafting on PVC was made evident by infrared analysis. PVC‐g‐MA was used like compatibilisant to solve the problem of the incompatibility between the hydrophobic polymeric matrix (PVC) and hydrophilic fiber (alfa). Composites samples were prepared with different alfa fiber loading (10, 20, and 30 wt %) and incorporating PVC‐g‐MA (1, 3, and 5 wt %) or PP‐g‐MA (3 wt %). The tensile properties, the thermal stability and the morphology of the composites were investigated. The result indicated that the PVC‐g‐MA increased the interfacial adhesion between the fibers and the polymer matrix and this effect was better than that obtained for the maleated‐polypropylene‐coupled composites. Microstructure analysis of the fractured surfaces of MAPP modified composites confirmed improved interfacial bonding. The addition of alfa and PVC‐g‐MA increased the thermal stability of the composites. The temperature of degradation of the polymer matrix increased about 16°C in comparison to the noncoupled composite, indicating that PVC‐g‐MA improved the thermal stability of the polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Compatibilization of polypropylene/Poly(acrylonitrile‐butadiene‐styrene) blends by polypropylene‐graft‐cardanol

The polypropylene‐graft‐cardanol (PP‐g‐cardanol) was prepared by reactive extrusion with polypropylene (PP) and natural renewable cardanol which could increase the interfacial energy of PP and inhibit the degradation of PP during the process of reactive extrusion and usage. In this article, PP‐g‐cardanol and polypropylene‐graft‐maleic anhydride (PP‐g‐MAH) were used as compatibilizers of the polypropylene (PP)/poly(acrylonitrile‐butadiene‐styrene) (ABS) blends. PP/ABS (70/30, wt %) blends with PP‐g‐cardanol and PP‐g‐MAH were prepared by a corotating twin‐screw extruder. From the results of morphological studies, the droplet size of ABS was minimized to 1.93 and 2.01 μm when the content of PP‐g‐cardanol and PP‐g‐MAH up to 5 and 7 phr, respectively. The results of mechanical testing showed that the tensile strength, impact strength and flexural strength of PP/ABS (70/30) blends increase with the increasing of PP‐g‐cardanol content up to 5 phr. The complex viscosity of PP/ABS (70/30) blends with 5 phr PP‐g‐cardanol showed the highest value. Moreover, the change of impact strength and tensile strength of PP/ABS (70/30) blends were investigated by accelerated degradation testing. After 4 accelerated degradation cycles, the impact strength of the PP/ABS (70/30) blends with 5 phr PP‐g‐cardanol decrease less than 6%, but PP/ABS (70/30) blends with 5 phr PP‐g‐MAH and without compatibilizer decrease as much as 12% and 32%, respectively. The tensile strength of PP/ABS (70/30) blends has a similar tendency to that of impact strength. The above results indicated that PP‐g‐cardanol could be used as an impact modifier and a good compatibilizer, which also exhibited better stability performance during accelerated degradation testing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41315.     

Preparation and properties of dynamically cured PP/MAH‐g‐EVA/epoxy blends

A method concerning with the simultaneous reinforcing and toughening of polypropylene (PP) was reported. Dynamical cure of the epoxy resin with 2‐ethylene‐4‐methane‐imidazole (EMI‐2,4) was successfully applied in the PP/maleic anhydride‐grafted ethylene‐vinyl acetate copolymer (MAH‐g‐EVA), and the obtained blends named as dynamically cured PP/MAH‐g‐EVA/epoxy blends. The stiffness and toughness of the blends are in a good balance, and the smaller size of epoxy particle in the PP/MAH‐g‐EVA/epoxy blends shows that MAH‐g‐EVA was also used as a compatibilizer. The structure of the dynamically cured PP/MAH‐g‐EVA/epoxy blends is the embedding of the epoxy particles by the MAH‐g‐EVA. The cured epoxy particles as organic filler increases the stiffness of the PP/MAH‐g‐EVA blends, and the improvement in the toughness is attributed to the embedded structure. The tensile strength and flexural modulus of the blends increase with increasing the epoxy resin content, and the impact strength reaches a maximum of 258 J/m at the epoxy resin content of 10 wt %. DSC analysis shows that the epoxy particles in the dynamically cured PP/MAH‐g‐EVA/epoxy blends could have contained embedded MAH‐g‐EVA, decreasing the nucleating effect of the epoxy resin. Thermogravimetric results show the addition of epoxy resin could improve the thermal stability of PP, the dynamically cured PP/MAH‐g‐EVA/epoxy stability compared with the pure PP. Wide‐angle x‐ray diffraction analysis shows that the dynamical cure and compatibilization do not disturb the crystalline structure of PP in the blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dynamically cured polypropylene/Novolac blends compatibilized with maleic anhydride‐g‐polypropylene

In this article, the dynamic vulcanization process was applied to polypropylene (PP)/Novolac blends compatibilized with maleic anhydride‐grafted PP (MAH‐g‐PP). The influences of dynamic cure, content of MAH‐g‐PP, Novolac, and curing agent on mechanical properties of the PP/Novolac blends were investigated. The results showed that the dynamically cured PP/MAH‐g‐PP/Novolac blend had the best mechanical properties among all PP/Novolac blends. The dynamic cure of Novolac improved the modulus and stiffness of the PP/Novolac blends. The addition of MAH‐g‐PP into dynamically cured PP/Novolac blend further enhanced the mechanical properties. With increasing Novolac content, tensile strength, flexural modulus, and flexural strength increased significantly, while the elongation at break dramatically deceased. Those blends with hexamethylenetetramine (HMTA) as a curing agent had good mechanical properties at HMTA content of 10 wt %. Scanning electron microscopy (SEM) analysis showed that dynamically cured PP/MAH‐g‐PP/Novolac blends had finer domains than the PP/MAH‐g‐PP/Novolac blends. Thermogravimetric analysis (TGA) results indicated that the incorporation of Novolac into PP could improve the thermal stability of PP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Study of the morphology and mechanical properties of polypropylene composites with silica or rice‐husk

The mechanical, morphological behavior and water absorption characteristics of polypropylene (PP) and silica, or PP and rice‐husk, composites have been studied. The silica used in this study as filler was a commercial type produced from soluble glass or rice husks. The compatibilizing effect of PP grafted with monomethyl itaconate (PP‐g‐MMI) and/or with vinyltriethoxysilane (PP‐g‐VTES) as polar monomers on the mechanical properties and water absorption was also investigated. In general, a high loading of the studied fillers in the polymer matrix increases the stiffness and the water absorption capacity. This effect is more noticeable in the tensile modulus of the PP/silica composite with PP‐g‐VTES as compatibilizer. However, the increase of the rice‐husk charge as a natural filler in the PP matrix decreases the stiffness, and in the presence of PP‐g‐MMI as compatibilizer in PP/rice‐husk, the tensile modulus and water absorption of the composite were improved. The better adhesion and phase continuity in the PP/silica and PP/rice‐husk composites with different compatibilizers was confirmed by the morphological study. Copyright © 2004 Society of Chemical Industry     

Compatibilization of intumescent flame retardant/polypropylene composites based on α‐methacrylic acid grafted polypropylene

A phosphoric acid–pentaerythritol–melamine copolymer was selected as an intumescent flame retardant (IFR). The influence of α‐methacrylic acid grafted polypropylene (PP‐g‐MAA) on the properties and compatibility of IFR/PP composites was studied. The results obtained from mechanical tests and scanning electron microscopy showed that PP‐g‐MAA was a true coupling agent for IFR/PP blends, but it did not change the necessary flame retardancy. The cocrystallization between bulk PP and PP segments of PP‐g‐MAA was proved by wide‐angle X‐ray diffraction analysis. A flow test showed that the flow behaviors of composites in the melt were those of a pseudoplastic liquid and it was very small for PP‐g‐MAA and affected the rheological behavior of the PP/IFR composite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3128–3132, 2002; DOI 10.1002/app.10099