Dynamically cured polypropylene/epoxy blends

The dynamic vulcanization process, usually used for the preparation of thermoplastic elastomers, was used to prepare polypropylene (PP)/epoxy blends. The blends had crosslinked epoxy resin particles finely dispersed in the PP matrix, and they were called dynamically cured PP/epoxy blends. Maleic anhydride grafted polypropylene (MAH‐g‐PP) was used as a compatibilizer. The effects of the reactive compatibilization and dynamic cure were studied with rheometry, capillary rheometry, and scanning electron microscopy (SEM). The crystallization behavior and mechanical properties of PP/epoxy, PP/MAH‐g‐PP/epoxy, and dynamically cured PP/epoxy blends were also investigated. The increase in the torque at equilibrium for the PP/MAH‐g‐PP/epoxy blends indicated the reaction between maleic anhydride groups of MAH‐g‐PP and the epoxy resin. The torque at equilibrium of the dynamically cured PP/epoxy blends increased with increasing epoxy resin content. Capillary rheological measurements also showed that the addition of MAH‐g‐PP or an increasing epoxy resin content increased the viscosity of PP/epoxy blends. SEM micrographs indicated that the PP/epoxy blends compatibilized with PP/MAH‐g‐PP had finer domains and more obscure boundaries than the PP/epoxy blends. A shift of the crystallization peak to a higher temperature for all the PP/epoxy blends indicated that uncured and cured epoxy resin particles in the blends could act as effective nucleating agents. The spherulites of pure PP were larger than those of PP in the PP/epoxy, PP/MAH‐g‐PP/epoxy, and dynamically cured PP/epoxy blends, as measured by polarized optical microscopy. The dynamically cured PP/epoxy blends had better mechanical properties than the PP/epoxy and PP/MAH‐g‐PP/epoxy blends. With increasing epoxy resin content, the flexural modulus of all the blends increased significantly, and the impact strength and tensile strength increased slightly, whereas the elongation at break decreased dramatically. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1437–1448, 2004     

Study of dynamically cured PP/MAH‐g‐PP/talc/epoxy composites

In the present study, an epoxy resin was dynamically cured in a polypropylene (PP)/maleic anhydride–grafted PP (MAH‐g‐PP)/talc matrix to prepare dynamically cured PP/MAH‐g‐PP/talc/epoxy composites. An increase in the torque at equilibrium showed that epoxy resin in the PP/MAH‐g‐PP/talc composites had been cured by 2‐ethylene‐4‐methane‐imidazole. Scanning electron microscopy analysis showed that MAH‐g‐PP and an epoxy resin had effectively increased the interaction adhesion between PP and the talc in the PP/talc composites. Dynamic curing of the epoxy resin further increased the interaction adhesion. The dynamically cured PP/MAH‐g‐PP/talc/epoxy composites had higher crystallization peaks than did the PP/talc composites. Thermogravimetric analysis showed that the addition of MAH‐g‐PP and the epoxy resin into the PP/talc composites caused an obvious improvement in the thermal stability. The dynamically cured PP/MAH‐g‐PP/talc/epoxy composites had the best thermal stability of all the PP/talc composites. The PP/MAH‐g‐PP/talc/epoxy composites had better mechanical properties than did the PP/MAH‐g‐PP/talc composites, and the dynamically cured PP/MAH‐g‐PP/talc/epoxy composites had the best mechanical properties of all the PP/talc composites, which can be attributed to the better interaction adhesion between the PP and the talc. The suitable content of epoxy resin in the composites was about 5 wt %. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

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     

Crystallization kinetics of polypropylene composites filled with nano calcium carbonate modified with maleic anhydride

The subject of this study was the crystallization behavior and thermal properties of polypropylene (PP)/maleic anhydride (MAH) modified nano calcium carbonate (nano‐CaCO₃) composites. In this study, 5 wt % nano‐CaCO₃ modified with different contents of MAH was filled into a PP matrix. X‐ray diffraction and differential scanning calorimetry were used to characterize the crystal morphology and crystallization kinetics of a series of composites. The results demonstrate that the nano‐CaCO₃ modified with MAH had an important effect on the thermal and morphological properties of the nanocomposites. The Avrami exponent of the pure PP was an integer, but those of the composites were not integers, but the crystallization rate constant decreased as the content of MAH in the nano‐CaCO₃ filler increased in isothermal crystallization. In nonisothermal crystallization, the kinetic parameter F(T) and the degree of crystallinity of pure PP were compared with those of the PP composites filled with nano‐CaCO₃. We suggest that heterogeneous nucleation existed in the PP composites and that the transformation and retention of the β‐form crystal into the α‐form crystal took place in the composite system and the β‐form crystal had a higher nucleation rate and growth process than the α‐form crystal in the PP composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of maleic anhydride/vinyltrimethoxysilane‐co‐grafting polypropylene on the properties of wood‐flour/polypropylene composites by electron‐beam preirradiation

The electron‐beam preirradiation and reactive extrusion technologies were used to prepare maleic anhydride (MAH)/vinyltrimethoxysilane (VTMS)‐co‐grafting polypropylene (PP) as a high‐performance compatibilizer for wood‐flour/PP composites. The grafting content, chemical structure, and crystallization behavior of the compatibilizers were characterized through Fourier transform infrared spectroscopy, differential scanning calorimetry, and an extraction method. The effects of the compatibilizers on the mechanical properties, water absorption, morphological structure, and torque rheological behavior of the composites were investigated comparatively. The experimental results demonstrate that MAH/VTMS‐g‐PP markedly enhanced the mechanical properties of the composites. Compared with MAH‐g‐PP and VTMS‐g‐PP, MAH/VTMS‐g‐PP clearly showed synergistic effects on the increasing mechanical properties, water absorption, and compatibility of the composites. Scanning electron microscopy further confirmed that the adhesion and dispersion of wood flours in the composites were effectively improved by MAH/VTMS‐g‐PP. These results were also proven by the best water resistance of the wood‐flour/PP composites with MAH/VTMS‐g‐PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Extrusion foaming behavior of a polypropylene/nanoclay microcellular foam

With maleic anhydride grafted polypropylene (PP‐g‐MAH) as a compatibilizer, composites of block‐copolymerized polypropylene (B‐PP)/nanoclay were prepared. The effects of the PP‐g‐MAH and nanoclay content on the crystallization and rheological properties of B‐PP were investigated. The microcellular foaming behavior of the B‐PP/nanoclay composite material was studied with a single‐screw extruder foaming system with supercritical (SC) carbon dioxide (CO₂) as the foaming agent. The experimental results show that the addition of nanoclay and PP‐g‐MAH decreased the melt strength and complex viscosity of B‐PP. When 3 wt % SC CO₂ was injected as the foaming agent for the extrusion foaming process, the introduction of nanoclay and PP‐g‐MAH significantly increased the expansion ratio of the obtained foamed samples as compared with that of the pure B‐PP matrix, lowered the die pressure, and increased the cell population density of the foamed samples to some extent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44094.     

Investigation on β‐polypropylene/PP‐g‐MAH/ surface‐treated calcium carbonate composites

β‐Polypropylene composites containing calcium carbonate treated by titanate coupling agent (T‐CaCO₃) and maleic anhydride grafted PP (PP‐g‐MAH) were prepared by melt compounding. The crystallization, morphology and mechanical properties of the composites were investigated by means of differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized light microscopy, scanning electron microscopy and mechanical tests. It is found that both T‐CaCO₃ and NT‐C are able to induce the formation of β‐phase, and NT‐C greatly increases the β content and decreases the spherulitic size of PP. PP‐g‐MAH facilitates the formation of β‐form PP and improves the compatibility between T‐CaCO₃ and PP. Izod notched impact strength of β‐PP/T‐CaCO₃ composite is higher than that of PP/T‐CaCO₃ composite, indicating the synergistic toughening effect of T‐CaCO₃ and β‐PP. Incorporation of PP‐g‐MAH into β‐PP/T‐CaCO₃ composite further increases the content of β‐crystal PP and improves the impact strength and tensile strength when T‐CaCO₃ concentration is below 5 wt%. The nonisothermal crystallization kinetics of β‐PP composites is well described by Jeziorny's and Mo's methods. It is found that NT‐C and T‐CaCO₃ accelerate the crystallization rate of PP but the influence of PP‐g‐MAH on crystallization rate of β‐PP composite is marginal. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

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     

Effect of the compatibilizer on the morphology and properties of dynamically cured PP/POE/epoxy blends

Dynamic vulcanization was successfully applied to epoxy resin reinforced polypropylene (PP)/ethylene‐octene copolymer (POE) blends, and the effects of different compatibilizers on the morphology and properties of dynamically cured PP/POE/epoxy blends were studied. The results show that dynamically cured PP/POE/epoxy blends compatibilized with maleic anhydride‐grafted polypropylene (MAH‐g‐PP) have a three‐phase structure consisting of POE and epoxy particles dispersed in the PP continuous phase, and these blends had improved tensile strength and flexural modulus. While using maleic anhydride‐grafted POE (MAH‐g‐POE) as a compatibilizer, the structure of the core‐shell complex phase and the PP continuous phase showed that epoxy particles could be embedded in MAH‐g‐POE in the blends, and gave rise to an increase in impact strength, while retaining a certain strength and modulus. DSC analysis showed that the epoxy particles in the blends compatibilized with MAH‐g‐PP were more efficient nucleating agents for PP than they were in the blends compatibilized with MAH‐g‐POE. WAXD analysis shows that compatibilization do not disturb the crystalline structure of PP in the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polypropylene–intumescent flame‐retardant composites based on meleated polypropylene as a coupling agent

The phosphoric acid‐pentaerythritol‐melamine copolymer, which is composed of three main components of intumescent flame retardant (IFR) and has optimal intumescent degree, was selected as IFR. The influence of meleated polypropylene (PP‐g‐MAH) on the properties and compatibility of IFR polypropylene (PP) composites were studied. The results obtained from mechanical tests, rheological behavior of composites, and scanning electron microscope showed that PP‐g‐MAH was a true coupling agent for IFR/PP blends and did not change the necessary flame retardancy. The cocrystallization between bulk PP and PP segments of PP‐g‐MAH was also proven by WAXD analysis. Flow test showed that the flow behaviors of composites in the melt are those of a pseudoplastic and it is very small for PP‐g‐MAH affecting rheological behavior of the PP/IFR composite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 257–262, 2002     

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.     

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     

Nonisothermal crystallization kinetics of polypropylene/polypropylene‐g‐polystyrene/polystyrene blends

The nonisothermal crystallization kinetics of polypropylene (PP), PP/polystyrene (PS), and PP/PP‐g‐PS/PS blends were investigated with differential scanning calorimetry at different cooling rates. The Jeziorny modified Avrami equation, Ozawa method, and Mo method were used to describe the crystallization kinetics for all of the samples. The kinetics parameters, including the half‐time of crystallization, the peak crystallization temperature, the Avrami exponent, the kinetic crystallization rate constant, the crystallization activation energy, and the F(T) and a parameters were determined. All of the results clearly indicate that the PP‐g‐PS copolymer accelerated the crystallization rate of the PP component in the PP/PP‐g‐PS/PS blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Isotactic polypropylene toughened with poly(acrylonitrile–butadiene–styrene): Compatibilizing role of maleic anhydride grafted polypropylene

The β‐nucleating activity and toughening effect of acrylonitrile–butadiene–styrene (ABS) graft copolymer on isotactic polypropylene (iPP) and the compatibilizing role of maleic anhydride grafted polypropylene (PP‐g‐MAH) on the iPP/ABS blends were investigated. The results show that ABS can induce the formation of β‐crystal in iPP, and its β‐nucleating efficiency depends on its concentration and dispersibility. The relative content of β‐crystal form is up to 36.19% with the addition of 2% ABS. The tensile and impact properties of the iPP were dramatically enhanced by introducing ABS. The incorporation of PP‐g‐MAH into the iPP/ABS blends inhibits the formation of β‐crystal. The crystallization peaks of the blends shift toward higher temperature, due to the heterogeneous nucleation effect of PP‐g‐MAH on iPP. The toughness of iPP/ABS blends improved due to favorable interfacial interaction resulting from the compatibilization of PP‐g‐MAH is significantly better than the β‐crystal toughening effect induced by ABS. POLYM. ENG. SCI., 59:E317–E326, 2019. © 2019 Society of Plastics Engineers     

Crystallization and melting behavior of nano‐CaCO3/polypropylene composites modified by acrylic acid

Nano‐CaCO₃/polypropylene (PP) composites modified with polypropylene grafted with acrylic acid (PP‐g‐AA) or acrylic acid with and without dicumyl peroxide (DCP) were prepared by a twin‐screw extruder. The crystallization and melting behavior of PP in the composites were investigated by DSC. The experimental results showed that the crystallization temperature of PP in the composites increased with increasing nano‐CaCO₃ content. Addition of PP‐g‐AA further increased the crystallization temperatures of PP in the composites. It is suggested that PP‐g‐AA could improve the nucleation effect of nano‐CaCO₃. However, the improvement in the nucleation effect of nano‐CaCO₃ would be saturated when the PP‐g‐AA content of 5 phf (parts per hundred based on weight of filler) was used. The increase in the crystallization temperature of PP was observed by adding AA into the composites and the crystallization temperature of the composites increased with increasing AA content. It is suggested that the AA reacted with nano‐CaCO₃ and the formation of Ca(AA)₂ promoted the nucleation of PP. In the presence of DCP, the increment of the AA content had no significant influence on the crystallization temperature of PP in the composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2443–2453, 2004     

Melting and crystallization behaviors,morphology, and mechanical properties of β‐polypropylene/polypropylene‐graft‐maleic anhydride/calcium sulfate whisker composites

The melting and crystallization behaviors, morphology, and mechanical properties of polypropylene (PP)/surface‐treated calcium sulfate (CaSO₄) whisker (T‐CSW), β‐PP/T‐CSW, and β‐PP/polypropylene‐graft‐maleic anhydride (PP‐g‐MAH)/T‐CSW composites had been investigated via differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), polarized light microscopy (PLM), scanning electron microscopy (SEM), and mechanical tests. We found that T‐CSW was an α‐nucleating agent and increased the crystallization temperatures of PP, but PP‐g‐MAH and high loadings of T‐CSW had weakly negative effects on the crystallization rates of PP. The T‐CSW restrained the formation of β‐spherulites, and the spherulitic size decreased in the composites. PP‐g‐MAH improved the compatibility and adhesion between T‐CSW and the matrix. The notched impact strength was improved, and the tensile strength was enhanced at low levels of T‐CSW, while the flexural modulus was weakened for β‐PP/T‐CSW and β‐PP/PP‐g‐MAH/T‐CSW composites versus PP/T‐CSW composites. POLYM. COMPOS., 37:2121–2132, 2016. © 2015 Society of Plastics Engineers     

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     

Carbon black‐filled immiscible polypropylene/epoxy blends

Carbon black‐ (CB) filled immiscible thermoplastic/thermosetting polymer blends consisting of polypropylene (PP) and epoxy resin were reported in this paper. The PP/epoxy/CB blends with varied compositions and different processing sequences were prepared by melt‐mixing method. The CB distribution and the relationship between morphology and electrical properties of the PP/epoxy/CB blends were investigated. Scanning electron microscopy (SEM), optical microscopy, and extraction experimental results showed that in PP/epoxy blends CB particles preferentially localized in the epoxy phase, indicating that CB has a good affinity with epoxy resin. The incorporation of CB changed the spherical particles of the dispersed epoxy phase into elongated structure. With increasing epoxy content, the elongation deformation of epoxy phase became more obvious and eventually the blends developed into cocontinuous structure. When CB was initially blended with PP and followed by the addition of epoxy resin, the partial migration of CB from PP to the epoxy phase was observed. When the PP/epoxy ratio was 40/60, the percolation threshold was reduced to about 4 phr CB, which is half of the percolation threshold of the PP/CB composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 461–471, 2006