Mechanical properties and microstructure of acrylonitrile–butadiene rubber vulcanizates reinforced by in situ polymerized phenolic resin

The phenolic resin (PF) was incorporated into acrylonitrile–butadiene rubber (NBR) vulcanizates by in situ polymerization during the vulcanization process. It was found that the tensile strength, tearing strength, and tensile strength (300% elongation) could be considerably enhanced 59.4, 80.2, and 126.4%, respectively, at an optimum PF content of only 15 phr, but the elongation at break and shore A hardness were only slightly affected on the basis of silica‐reinforced NBR vulcanizates. A systematic study of the PF structure formed within the NBR matrix using various experimental schemes and procedures has revealed that the PF resin would form the localized discontinuous three‐dimensional interconnected network structures in the NBR matrix. The substantial reinforcement of PF on the mechanical properties of vulcanized NBR were attributed to the morphology, high flexibility, and moderate stiffness of the PF phases and their excellent bonding with rubbers through “rubber to rubber” and interface layer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis of nanosized ethylene–propylene rubber latex via polyisoprene hydrogenation

Nanosized ethylene–propylene rubber (EPM) latex with a particle size of 47 nm was synthesized via an alternative route consisting of isoprene (IP) polymerization followed by hydrogenation. First, the IP monomer was polymerized by differential microemulsion polymerization to obtain polyisoprene (PIP) rubber latex with a particle size of 42 nm. The structure of synthetic PIP was hydrogenated at the carbon–carbon double bonds to produce an ethylene–propylene copolymer by diimide reduction in the presence of hydrazine and hydrogen peroxide using boric acid as promotor. The degree of hydrogenation was determined by proton nuclear magnetic resonance (¹H‐NMR) spectroscopy and the structure of the ethylene–propylene copolymer was identified by ¹³C‐NMR spectroscopy. In nanosized PIP hydrogenation, the hydrogenation level was found to be increased by boric acid addition. An EPM yield of 94% was achieved using a hydrogen peroxide : hydrazine ratio of 1.5 : 1. The EPM produced from PIP has high thermal stability with the maximum decomposition temperature of 510°C and a glass transition temperature of ‐42.4°C close to commercial ethylene–propylene diene rubber. Dynamic mechanical analysis indicated that EPM had a maximum storage modulus due to the saturated carbons domains of the ethylene segments in the polymer chains. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Phase separation and crystallization behavior in extruded polypropylene/ethylene–propylene rubber blends

Liquid–liquid (L–L) phase separation and its effects on crystallization in polypropylene (PP)/ethylene–propylene rubber (EPR) blends obtained by melt extrusion were investigated by time‐resolved light scattering (TRLS) and optical microscopy. L–L phase separation via spinodal decomposition (SD) was confirmed by TRLS data. After L–L phase separation at 250°C for various durations, blend samples were subjected to a temperature drop to 130°C for isothermal crystallization, and the effects of L–L phase separation on crystallization were investigated. Memory of the L–L phase separation via SD remained for crystallization. The crystallization rate decreased with increasing L–L phase‐separated time at 250°C. Slow crystallization for the long L–L phase‐separated time could be ascribed to decreasing chain mobility of PP with a decrease in the EPR component in the PP‐rich region. The propylene‐rich EPR exhibited good affinity with PP, leading to a slow growth of a concentration fluctuation during annealing. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 695–700, 2001     

Polymerization conversion and structure of magnesium methacrylate in ethylene–vinyl acetate rubber vulcanizates

Ethylene–vinyl acetate rubber (EVM) filled with magnesium methacrylate (MDMA) was cured with dicumyl peroxide (DCP). The experimental results showed that the mechanical properties of MDMA/EVM vulcanizates were superior to those of high‐abrasion furnace carbon black/EVM vulcanizates. The tensile strength of the MDMA/EVM vulcanizate could reach 22.5 MPa and the tear strength was 83.5 kN/m, whereas its elongation at break remained over 300%, even when the MDMA content was 50 phr. FTIR analysis confirmed that polymerization of MDMA occurred under the initiation of DCP, and the polymerization conversion of MDMA decreased with the increase of MDMA content. When the MDMA content increased from 10 to 50 phr, the conversion of MDMA in EVM decreased from 68 to 20%. SEM and TEM observations indicated that 20 μm particles of MDMA powder changed into about 20 nm particles during the curing process, and the finer particles dispersed evenly in the EVM vulcanizates. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2379–2384, 2004     

Tensile elongation of high‐fluid polypropylene/ethylene–propylene rubber blends: Dependence on molecular weight of the components and propylene content of the rubber

We studied tensile behavior of low‐molecular‐weight (MW) polypropylene (PP)/ethylene–propylene rubber (EPR; 70/30) blends from the viewpoint of the MWs of PP and EPR and the compatibility between PP and EPR. The value of the melt flow rate of PP varied from 30 to 700 g/10 min at 230°C. We studied the compatibility between PP and EPR by varying the propylene content in EPR (27 and 68 wt %). At the initial elongation stage, crazes were observed in all blends. When blends included EPR with 27 wt % propylene, the elongation at break of the low‐MW PP improved little. The blends with EPR and 68 wt % propylene content were elongated further beyond their yielding points. The elongation to rupture was increased with increasing MW of EPR. Molecular orientation of the low‐MW PP was manifested by IR dichroism measurements and X‐ray diffraction patterns. The blends of low‐MW PP and EPR could be elongated by the partial dissolution of EPR of high‐MW in the PP amorphous phase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 46–56, 2002     

Modification of fast-cure ethylene–propylene diene terpolymer rubber by maleic anhydride and effect of electron donor

Grafting of maleic anhydride (MA) onto fast-cure ethylene–propylene diene terpolymer rubber was studied. The effect of the amount of the MA, initiator (dicumyl peroxide), and electron donor (stearamide) on graft content are described. The potentiometric method and Fourier transform infrared spectroscopy are used to obtained the graft content. The stearamide suppresses the side reactions, such as crosslinking and chain scission. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1–5, 1998     

Effect of metallic oxides on thermal stability of ethylene–propylene terpolymer

Thermal stability of ethylene–propylene terpolymer (EPDM) loaded with various metallic oxides (PbO, CuO, NiO, Fe₂O₃, Cr₂O₃, TiO₂, ZrO₂) was assessed by the oxygen uptake method. The effects of 5 phr oxide of thermal aging of elastomer were investigated under isothermal (180°C) and isobaric (air at normal pressure) conditions. The influence of this was pointed out. Some mechanistic considerations on the oxidative degradation of EPDM are presented. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2155–2158, 2001     

New synthesis methods for polypropylene‐co‐ethylene‐propylene rubber

In this research, the reinforcement of polypropylene (PP) was studied using a new method that is more practical for synthesizing polypropylene‐block‐poly(ethylene‐propylene) copolymer (PP‐co‐EP), which can be used as a rubber toughening agent. This copolymer (PP‐co‐EP) could be synthesized by varying the feed condition and changing the feed gas in the batch reactor system using Ziegler–Natta catalysts system at a copolymerization temperature of 10°C. The ¹³C‐NMR tested by a 21.61‐ppm resonance peak indicated the incorporation of ethylene to propylene chains that could build up the microstructure of the block copolymer chain. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA) results also confirmed these conclusions. Under these conditions, the morphology of copolymer trapped in PP matrix could be observed and the copolymer T_g would decrease when the amount of PP‐co‐EP was increased. DMA study also showed that PP‐co‐EP is good for the polypropylene reinforcement at low temperature. Moreover, the PP‐co‐EP content has an effect on the crystallinity and morphology of polymer blend, i.e., the crystallinity of polymer decreased when the PP‐co‐EP content increased, but tougher mechanical properties at low temperature were observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3609–3616, 2007     

Radiation processing of ethylene‐propylene rubber

The effects of ionizing radiation on ethylene‐propylene copolymer were evaluated over the range of total γ doses up to 500 kGy. The influence of the irradiation dose was investigated by oxygen uptake and thermal analysis. Four testing temperatures (170, 180, 190, and 200°C) and two heating rates between 2.9 and 5.9 K/min were selected for oxygen uptake measurements and thermal analysis, respectively. The competition between crosslinking and scission was examined on the basis of kinetic parameters of postirradiation oxidation. The influence of the momentary concentration of hydrocarbon free radicals is discussed in regard to the contribution of the antagonistic processes of crosslinking and oxidative degradation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 298–303, 2000     

Morphology of photodegraded heterophasic ethylene–propylene copolymers

The morphology of photooxidative degraded films of heterophasic ethylene–propylene copolymer (EPQ‐30R) was investigated and compared with isotactic polypropylene and linear low‐density polyethylene by scanning electron microscopy. Surface damage caused by polychromatic ultraviolet irradiation (λ ≥ 290 nm) at 55°C in air is presented in different micrographs. Changes occurring due to the formation of polar groups during photooxidative degradation are discussed. Morphological study of these photodegraded polymer samples show very good correlation with the photodegradation results. The rate of photooxidation is very fast in case of isotactic polypropylene, compared with polyethylene and ethylene–propylene copolymers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 215–225, 1999     

Kinetic effects of selenium on degradation of ethylene–propylene copolymer

The antioxidation protection of elementary selenium added to an ethylene–propylene copolymer (EPR) at different concentrations (0.1, 0.2, and 0.5 phr) was studied. Oxygen uptake measurements were isothermally performed at 180°C on polymer samples stabilized with increasing concentrations of Se. Experimental data have revealed the enhancement in induction periods and the decrease in oxidation rates for unaged elastomer samples. Stabilized polymer specimens exposed to γ‐radiation have presented the highest effects at 0.5 phr of selenium concentration for all irradiation doses (50, 100, 150, and 250 kGy). Influence of selenium on the competition between crosslinking and oxidation occurred in γ‐irradiated ethylene–propylene elastomers discussed on the basis of kinetic treatment on studied thermal degradation process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2053–2057, 2001     

A comparison of white rice husk ash and silica as fillers in ethylene–propylene–diene terpolymer vulcanizates

White rice husk ash (WRHA) and silica filled ethylene–propylene–diene terpolymer (EPDM) vulcanizates were prepared using a laboratory size two‐roll mill. Curing characteristics and physical properties of vulcanizates were studied with respect to the filler loading and filler type. Filler loading was varied from 0–50 parts per hundred resin (phr) at 10 phr intervals. Curing was carried out using a semi‐efficient vulcanization system in a Monsanto rheometer. Enhancement of the curing rate was observed with increasing WRHA loading, whereas the opposite trend was observed for silica‐filled vulcanizates. It was also indicated by the maximum torque and Mooney viscosity results that WRHA offers processing advantages over silica. Compared to the silica‐filled vulcanizates, the effect of filler loading on the physical properties of WRHA‐filled vulcanizates was not significant. According to these observations, WRHA could be used as a diluent filler for EPDM rubber, while silica can be used as a reinforcing filler. © 2001 Society of Chemical Industry     

DMA analysis of the damping of ethylene–vinyl acetate/acrylonitrile butadiene rubber blends

The mechanical and damping properties of blends of ethylene–vinyl acetate rubber (VA content > 40% wt) (EVM)/acrylonitrile butadiene rubber (NBR), with 1.4 phr BIPB [bis (tert‐butyl peroxy isopropyl) benzene] as curing agent, were investigated by DMA and DSC. The effect of chlorinated polyvinyl chloride (CPVC), silica, carbon black, and phenolic resin (PF) as a substitute curing agent, on the damping and mechanical properties of EVM/NBR blends were studied. The results showed that 10 phr CPVC did not contribute to the damping of EVM700/NBR blends; Silica could dramatically improve the damping of EVM700/NBR blends because of the formation of bound rubber between EVM700/NBR and silica, which appeared as a shoulder tan δ peak between 20 and 70°C proved by DMA and DSC. This shoulder tan δ peak increased as the increase of the content of EVM in EVM/NBR blends. The tensile strength, modulus at 100% and tear strength of the blend with SiO₂ increased while the elongation at break and hardness decreased comparing with the blend with CB. PF, partly replacing BIPB as the curing agent, could significantly improve the damping of EVM700/NBR to have an effective damping temperature range of over 100°C and reasonable mechanical properties. Among EVM600, EVM700, and EVM800/NBR/silica blend system, EVM800/NBR/silica blend had the best damping properties. The EVM700/NBR = 80/10 blend had a better damping property than EVM700/NBR = 70/20. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The combination of expandable graphite,organic montmorillonite,and magnesium hydrate as fire‐retardant additives for ethylene–propylene–diene monomer/chloroprene rubber foams

The fire retardancy and flame‐retardant mechanism of expandable graphite (EG), organic montmorillonite (OMMT), and magnesium hydrate (MH) in ethylene‐propylene‐diene monomer/chloroprene rubber (EPDM/CR) foams were investigated. The results indicated that the combination of EG and OMMT remarkably improved the fire‐retardant property compared to the control samples, and better fireproof performance was achieved when MH was used as the third coretardant unit. The structure of the obtained EPDM/CR/OMMT composites was characterized by X‐ray diffraction, and the results showed that the composites had an intercalated nanostructure. The limiting oxygen index, vertical burning test, and cone calorimeter test results showed that the LOI values and UL‐94 rating increased while the second peak of the heat release rates (HRR) decreased within the EG/OMMT system. In particular, the second pHRR disappeared when the EG/OMMT/MH system was used as a flame retardant. Moreover, the results of thermogravimetric analysis showed that the combination of EG and OMMT reduced the thermal‐degradation rates and mass‐loss percentages. Furthermore, observation by scanning electron microscopy revealed that EG and OMMT left over after combustion formed a complete, compact, and rigid charred layer with a mosaic structure of expanded graphite embedded in cortical‐honeycomb layers of OMMT. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44929.     

Influences of copolymerization conditions on the structure and properties of isotactic polypropylene/ethylene–propylene random copolymer in situ blends

A spherical TiCl₄/MgCl₂‐based catalyst was used in the synthesis of in situ isotactic polypropylene/ethylene–propylene random copolymer blends by propylene bulk polymerization and subsequent gas‐phase copolymerization of ethylene with propylene. Different copolymerization conditions, such as the reaction time, monomer pressure, and composition, were investigated, and their influences on the structure and properties of the products were studied. Raising the monomer pressure was the most effective way of speeding up the copolymerization, but it caused more increases in the random copolymer than the block copolymer fractions. Increasing the ethylene content of the monomer feed also resulted in higher reaction rates and copolymer contents, but the ethylene contents of both the random and block copolymer fractions were also raised. In situ blends that contain more than 50 wt % copolymer were prepared. The mechanical properties of the blends, including the impact strength and flexural modulus, were regulated in a rather broad range with changes in the copolymerization conditions. The properties were highly dependent on the amount, distribution, and chain structure of the copolymer fractions. The impact strength was influenced by both the random copolymer and block copolymer portions in a complicated way, whereas the flexural modulus was mainly determined by the amount of random copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 445–453, 2002; DOI 10.1002/app.10415     

Electrical and mechanical properties of ethylene propylene diene monomer–chloroprene rubber blend loaded with white and black fillers

The permittivity ε′ and dielectric loss ε" for different ratios of an ethylene propylene diene monomer (EPDM)–chloroprene rubber (CR) blend ranging from 0 to 100 phr were measured over a frequency range from 400 Hz to 60 kHz. The measurements were carried out at room temperature (25°C). The values of ε′ and ε" were found to decrease with increasing EPDM content in the EPDM–CR blend. The sample which possesses the best mechanical and electrical properties was a 50 EPDM–50 CR blend. This sample was chosen to be loaded with 40 phr of some white fillers, namely, calcium carbonate, silica, silitan z, and talc. From the electrical and mechanical investigations, it was found that the use of silica and calcium carbonate in these blends could improve these properties. The electrical and mechanical properties were also studied for the investigated blends loaded with both silica and calcium carbonate with different contents (10–40 phr). It was found that 20 phr is the most promising concentration which can possess better properties. The same trend was obtained by the addition of 20 phr SRF black in addition to the white fillers to the above blends. On the other hand, from the compatibility study between both investigated rubber, it is found that both types are incompatible, in which some improvement may occur by the addition of PVC. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2061–2068, 1998     

Characterization and properties of polypropylene‐block‐poly(ethylene‐co‐propylene) synthesized by short‐period polymerization

The morphology and mechanical properties of novel block copolymers consisting of isotactic polypropylene (PP) and ethylene–propylene rubber (EPR) synthesized by a short‐period polymerization method were examined using differential scanning calorimetry, atomic force microscopy, dynamic mechanical analysis, and a rheooptical technique. It was found that the novel block copolymers show a single glass transition and EPR segments are trapped into the amorphous region of PP. Furthermore, the rheooptical analysis demonstrates that a drawing process of the EPR‐rich block copolymer induces orientation of the PP lamellae in the EPR matrix. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 958–964, 1999     

The study of polystyrene blends: The relationship of phases and structure in blends of polystyrene with ethylene–propylene diene monomer rubber and its grafted copolymer

Pressed films of blends of polystyrene (PS) with ethylene–propylene diene monomer rubber (EPDM) or grafted copolymer of styrene (St) onto EPDM (EPDM-g-St) rubber were examined by small-angle X-ray scattering (SAXS), and scanning electron microscope (SEM). Small-angle X-ray scattering from the relation of phase was analyzed using Porod's Law and led to value of interface layer on blends. The thickness of interface layer (σ_b) had a maximum value at 50/50 (PS–EPDM-g-St) on blends. The radius of gyration of dispersed phase (domain) and correlation distances a_c in blends of PS–EPDM-g-St were calculated using the data of SAXS. The morphology and structure of blends were investigated by SEM. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 805–810, 1998     

Phase interactions and structure evolution of heterophasic ethylene–propylene copolymers as a function of system composition

Heterophasic copolymers comprised of polypropylene (PP) matrix and ethylene–propylene copolymer (EPC) dispersed phase were investigated with respect to the dispersed phase composition, i.e., ethylene/propylene ratio. The rheological properties, morphology, as well as thermal and mechanical relaxation behavior were studied to describe the structure evolution and phase interactions between the components of the PP copolymers. Decrease of the ethylene content of the EPC leads to a higher matrix‐dispersed phase compatibility, as evaluated by the shift of the glass transition temperatures of EPC and PP towards each other. At ethylene content of EPC of 17 wt %, the glass transition temperatures of the both phases merged into a joint relaxation. The effect of the EPC composition on the internal structure of the dispersed domains and on the morphology development of the heterophasic copolymers was demonstrated. Decreasing ethylene content was found to induce a refinement of the dispersed phase with several orders of magnitude down to 0.18 μm for propylene‐rich EPC. Optical microscopy observations showed that the dispersed propylene‐rich phase is preferably rejected at the interlamellar regions of the spherulites and/or at the interspherulitic regions, while the ethylene‐rich domains are engulfed within the PP spherulites. Both of these processes impose an additional energetic barrier and influence the spherulite growth rate of the heterophasic materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2825–2837, 2006     

Preparation and characterization of acrylonitrile–styrene–methylmethacrylate terpolymer as a compatibilizer for rubber blends

Acrylonitrile‐co‐styrene‐co‐methylmethacrylate (AN‐S‐MMA) terpolymer was prepared by bulk and emulsifier‐free emulsion polymerization techniques. The bulk and emulsion terpolymers were characterized by means of Fourierr transform infrared spectroscopy, ¹³C nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography, thermal gravimetric analysis, and elemental analysis. The kinetics of the terpolymerization were studied. The terpolymers were then incorporated into butadiene—acrylonitrile rubber (NBR)/ethylene propylene diene monomer rubber (EPDM) blends and into chloroprene rubber (CR)/EPDM blend. The terpolymers were then tested for potential as compatibilizers by using scanning electron microscopy and differential scanning calorimetry. The terpolymers improved the compatibility of CR/EPDM and NBR/EPDM blends. The physicomechanical properties of CR/EPDM and NBR/EPDM blend vulcanizates revealed that the incorporation of terpolymers was advantageous, since they resulted in blend vulcanizates with higher 100% moduli and with more thermally stable mechanical properties than the individual rubbers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3143–3153, 2003