In‐situ polymerized phenolic resin for reinforcement of chloroprene and ethylene–propylene rubber vulcanizates

Phenolic resin (PF) was incorporated into rubbers by in situ polymerization at the vulcanization conditions of rubbers. The PF with a localized three‐dimensional network structure was formed in chloroprene rubber (CR), whereas the fabric PF was formed in ethylene–propylene rubber (EPDM). The study results showed that the PF phase was effective on reinforcing these rubbers. Depending on the morphologies of the formed PF phases, various rubber properties could be significantly enhanced. In the case of CR rubber, the tensile strength, tear strength, and modulus could be considerably enhanced, but the elongation and resilience properties were limitedly affected by PF addition. For EPDM rubber, all mechanical properties were improved, particularly the elongation, about 26% increase. The substantial improvements of mechanical properties of CR and EPDM rubbers were attributed to their morphology, high flexibility, moderate stiffness, and excellent bonding with rubber matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

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     

Noncatalytic hydrogenation of natural rubber latex

Hydrogenation is an important method of chemical modification, which improves the physical, chemical, and thermal properties of diene‐based elastomers. Natural rubber latex (NRL) could be hydrogenated to a strictly alternating ethylene–propylene copolymer using diimide generated in an in situ system. The diimide generated using the in situ technique for hydrogenation of NRL was accomplished by thermolysis of p‐toluenesulfonyl hydrazide (TSH). A molar ratio of TSH to double bonds equal to 2 : 1 was found to be the optimum ratio to provide a high percentage of hydrogenation. 95% Degree of saturation of NRL was achieved in o‐xylene. Hydrogenated products are characterized by FTIR and NMR spectroscopy. The thermal stability of hydrogenated rubber was improved as shown from the results of thermogravimetric analysis. From the differential scanning calorimetry measurement, the glass transition temperature of the hydrogenated product did not appear to change. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2885–2895, 2007     

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     

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     

Diimide hydrogenation of natural rubber latex

Hydrogenation is one important method of chemical modification, which improves the physical, chemical and thermal properties of diene‐based elastomers. Natural rubber latex (NRL) could be hydrogenated to a strictly alternating ethylene‐propylene copolymer using a diimide reduction system. The diimide reduction technique of NRL was accomplished by using hydrazine hydrate/hydrogen peroxide and Cu²⁺ as catalyst. The hydrogenated products are characterized by FTIR and NMR spectroscopy. It has been found that cupric acetate is a highly active catalyst for the reaction and the addition of a controlled amount of gelatin demonstrated a beneficial effect on the degree of hydrogenation, whereas, sodium dodecyl sulfate (SDS) acted as a stabilizer of the latex particle in the reaction system and reduced the degree of hydrogenation. In the presence of SDS, a longer reaction time and a higher amount of hydrazine hydrate was required for hydrogenation of NRL. Gel formation during hydrogenation does not significantly affect the degree of hydrogenation. Gel inhibitors such as hydroquinone also decrease the degree of hydrogenation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

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     

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     

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     

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     

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     

影响偶氨法常压氢化丁苯胶乳氢化度及凝胶的因素

研究了采用水合肼（N2H2·H2O）/H2O2/CuSO4使冷法聚合丁苯胶乳在常压下氢化的各种条件,包括乳化剂种类及用量、催化剂CuSO4的用量、N2H4·H2O及H2O2的用量、反应温度及反应时间等对氢化丁苯橡胶氢化度及凝胶含量的影响。结果表明,当加入质量分数为0 8％的十二烷基苯磺酸钠乳化剂,CuSO4催化剂用量为0.0025 mmol/g,反应温度为55℃,反应时间为7h,N2H4/C=C之摩尔比为1.8,H2O2/N2H4之摩尔比为1.5时,可得到氢化度为98％。凝胶质量分数小于0.6％的氢化丁苯橡胶。     

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     

Influence of styrene content on the hydrogenation of styrene–butadiene copolymer

A hydrogenated styrene–butadiene copolymer (HSBR) was prepared by a diimide reduction of SBR in the latex stage. The influence of the styrene content on various reaction parameters, namely, time, temperature, and concentration of the reactants and the catalyst was studied. A comparatively lower temperature, longer time, lesser amount of hydrogen peroxide, and higher amount of the catalyst are required to optimize the hydrogenation reactions of SBR with a higher styrene content. The diimide reduction of SBR is first order with respect to the olefinic substrate and the apparent activation energy increases with increase in the styrene level. All the hydrogenated copolymers were characterized with the help of IR, NMR, and DSC. The TGA data indicate a higher thermal stability of HSBR as compared to SBR in nitrogen, although an anomalous behavior is observed in air due to crosslinking and oxidation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1581–1595, 1999     

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     

Blends of ethylene–methyl acrylate–acrylic acid terpolymers with ethylene–acrylic acid copolymers: Mechanical and thermomechanical properties

The effect of methyl acrylate content in ethylene–methyl acrylate–acrylic acid (E–MA–AA) terpolymers and acrylic acid content in ethylene–acrylic acid (E–AA) copolymers was investigated in blends of these two materials. The E–MA–AA terpolymer with 8 mol % methyl acrylate was not miscible with any E–AA material no matter what the AA content, whereas the terpolymer with only about 2 mol % methyl acrylate was miscible, at least to some extent, with the E–AA copolymer at high acrylic acid contents. Evidence supporting this conclusion derived from gloss, differential scanning calorimetry testing, and dynamic mechanical measurements. For the E–AA polymer material with the highest acid content, there was a synergistic effect for some properties at low added amounts of E–MA–AA copolymer; the tensile strength and hardness were 10% higher than values for the E–AA copolymer, even though the E–AA copolymer was much stiffer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2216–2222, 2004     

Radiation effects on poly(propylene) (PP)/ethylene–vinyl acetate copolymer (EVA) blends

Radiation effects on poly(propylene)/ethylene–vinyl acetate copolymer (PP/EVA) blends are discussed. Increasing the EVA content enhanced the crosslinking effect of radiation in PP/EVA blends. This effect was significant when the EVA content was ≥50% in PP/EVA blends that were exposed to γ‐ray irradiation in air. This phenomenon is discussed in relation to the compatibility, morphology, and thermal properties of PP/EVA blends. The results indicate that the effect is dependent on the compatibility, the increase in the amorphous region content, and the EVA content in PP/EVA blends. The possible mechanism of radiation crosslinking or degradation in irradiated PP/EVA blends was studied quantitatively by a novel method, a “step analysis” process, and thermal gravimetric analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3420–3424, 2002     

Effect of octene content on peroxide crosslinking of ethylene–octene copolymers

Various ethylene–octene copolymers were crosslinked by dicumyl peroxide. Octene content was 16, 20, 30, 35 and 38 wt% and melt flow index was 1 or 3 g/10 min. The concentration of dicumyl peroxide was 0.3, 0.5 and 0.7 wt%. Crosslinking was analyzed by a rubber process analyzer in the temperature range 150–200 °C. Cross‐linkability was evaluated from the real part modulus s'_max versus peroxide level plots as the slope of the line. With decreasing octene content and increasing melt flow index the crosslinkability increased. This was confirmed also by tan δ analysis. The network density was measured by the gel content. A higher gel content was found for melt flow index 3 and low octene content. The melting points T_m and the crystallinities were evaluated by DSC. © 2012 Society of Chemical Industry