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     

Surface photocrosslinking of ethylene–vinyl acetate copolymer films

Surface photocrosslinking of ethylene–vinyl acetate (EVAc) copolymer films containing benzophenone (BP) was investigated for the purpose of replacing a poly(vinyl chloride) floor. The photogelatin in the EVAc films was effectively observed after UV radiation in the presence of oxygen. The crosslinking reaction was initiated from the surface of the irradiated film, which was mainly due to the dehydrogenation and generation of macroradicals of polymer by the light absorption of BP. The experiments of polyethylene–VAc with BP showed that the VAc‐rich amorphous part in the EVAc copolymer works as a crosslinking site. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1741–1745, 2000     

Shape memory effect of ethylene–vinyl acetate copolymers

Crosslinked ethylene–vinyl acetate (EVA) copolymers with VA content of 28% by weight were prepared by a two‐step method by evenly dispersing the crosslinking agent (dicumyl peroxide) into the EVA matrix and then crosslinking at elevated temperatures. The crosslinking features of the samples were analyzed by Soxhlet extraction with xylene and dynamic mechanical measurements. All the samples were crystalline at room temperature, and the chemical crosslinks seemed to have little effect on the melting behavior of polyethylene segment crystals in the EVA copolymers. The shape recovery results indicated that only those specimens that had a sufficiently high crosslinking degree (gel content higher than about 30%) were able to show the typical shape memory effect, a large recoverable strain, and a high final recovery rate. The degree of crosslinking can be influenced by the amount of the peroxide and the time and temperature of the reaction. The response temperature of the recovery effect (about 61°C) was related to the melting point of the samples. The EVA shape memory polymer was characterized by its low recovery speed that resulted from the wide melting range of the polyethylene segment crystals. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1063–1070, 1999     

Hansen solubility parameter: from polyethylene and poly(vinyl acetate) homopolymers to ethylene–vinyl acetate copolymers

The Hansen solubility parameters (HSPs ) of two ethylene–vinyl acetate (EVA ) copolymers (with 18 and 33 wt% of vinyl acetate) and their corresponding homopolymers (polyethylene, PE , and poly(vinyl acetate), PVAc ) have been studied at various temperatures, employing the previously obtained Flory–Huggins parameters. From these latter values, a procedure based on the Hansen solubility spheres theory was employed to determine the HSPs , as well as the radius of interaction. The procedure was validated with literature data, with deviations of around 3%. The HSP values (dispersion, polar and association terms, respectively, all in MPa^{1 /2}) at 333.15 K are 14.84, ?3.88 and 1.78 for PE , 17.65, ?1.24 and 2.76 for EVA410 (with 18 wt% of vinyl acetate), 17.52, 0.15 and 3.61 for EVA460 (with 33 wt% of vinyl acetate) and 19.45, 10.59 and 5.76 for PVAc . The main characteristic of the obtained HSP values is that the high polar term of PVAc tends to increase the solubility character of the pure PE , and thus the EVA copolymers, allowing them to solubilize dispersion and polar compounds. Finally, it was also demonstrated that it is possible to predict the HSPs of EVA copolymers using the vinyl acetate content and the HSPs of pure PE and PVAc as input data. © 2017 Society of Chemical Industry     

Compatibilization of nitrile‐butadiene rubber/ethylene‐propylene‐diene monomer blends by mercapto‐modified ethylene‐vinyl acetate copolymers

Mercapto‐modified ethylene‐vinyl acetate (EVASH) has been employed as a reactive compatibilizing agent for nitrile‐butadiene rubber (NBR)/ethylene‐propylene‐diene monomer (EPDM) blends vulcanized with a sulfur/2,2′‐dithiobisbenzothiazole (MBTS) single accelerator system and a (sulfur/MBTS/tetramethylthiuram disulfide (TMTD) binary accelerator system. The addition of 5.0 phr EVASH resulted in a significant improvement in the tensile properties of blends vulcanized with the sulfur/MBTS system. In addition to better mechanical performance, these functionalized copolymers gave rise to a more homogeneous morphology and, in some cases, better aging resistance. The compatibilization was not efficient in blends vulcanized with the S/MBTS/TMTD binary system, probably because of the faster vulcanization process occurring in this system. The good performance of these EVASH samples as compatibilizing agents for NBR/EPDM blends is attributed to the higher polarity of these components that is associated with their lower viscosity. Dynamic mechanical analysis also suggested a good interaction between the phases in the presence of EVASH. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1404–1412, 2004     

Improvement of properties of silica‐filled styrene–butadiene rubber compounds using acrylonitrile–butadiene rubber

Since silica has strong filler–filler interactions and adsorbs polar materials, a silica‐filled rubber compound has a poor dispersion of the filler and poor cure characteristics. Improvement of the properties of silica‐filled styrene–butadiene rubber (SBR) compounds was studied using acrylonitrile–butadiene rubber (NBR). Viscosities and bound rubber contents of the compounds became lower by adding NBR to the compound. Cure characteristics of the compounds were improved by adding NBR. Physical properties such as modulus, tensile strength, heat buildup, abrasion, and crack resistance were also improved by adding NBR. Both wet traction and rolling resistance of the vulcanizates containing NBR were better than were those of the vulcanizate without NBR. The NBR effects in the silica‐filled SBR compounds were compared with the carbon black‐filled compounds. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1127–1133, 2001     

Radiation-induced Grafting of Acrylic Acid and Vinyl Acetate Monomers onto Heavy-duty Poly(ethylene–vinyl acetate) Films

The preparation of graft films was carried out by direct radiation-induced graft polymerization of acrylic acid and vinyl acetate comonomer onto heavy-duty poly(ethylene–vinyl acetate) films. The effect of various comonomer compositions on the degree of grafting was investigated. The characterization and some selected properties of the graft copolymers prepared were studied. Thermal stability, mechanical and electrical properties of the films showed great promise for some practical applications. © of SCI.     

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     

Crosslinking of polyvinyl chloride by electron beam irradiation in the presence of ethylene–vinyl acetate copolymer

Electron beam (EB) irradiation of polyvinyl chloride (PVC) was carried out in the presence of three different ethylene–vinyl acetate copolymers (EVA). The mechanical properties of the original and irradiated blends were tested. The gel content measurement, chlorine loss upon electron irradiation, and gel permeation chromatograph (GPC) were used to characterize the effect of EVA on the irradiation behavior of PVC/EVA blends. The content and the chemical structure of EVA in the blends had considerable effects on the mechanical properties and gel content of the blends. The incorporation of EVA into PVC blend can increase the gel content and reduce chlorine loss of the blends. The GPC analysis of the soluble part in the irradiated PVC samples showed that the addition of EVA into the PVC blend lowered the polydispersity of molecular weight of PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1571–1575, 2004     

Mechanical properties,flame retardancy,hot‐air ageing,and hot‐oil ageing resistance of ethylene‐vinyl acetate rubber/hydrogenated nitrile‐butadiene rubber/magnesium hydroxide composites

The mechanical properties, flame retardancy, hot‐air ageing, and hot‐oil ageing resistance of ethylene‐vinyl acetate rubber (EVM)/hydrogenated nitrile‐butadiene rubber (HNBR)/magnesium hydroxide (MH) composites were studied. With increasing HNBR fraction, elongation at break and tear strength of the EVM/HNBR/MH composites increased, whereas the limited oxygen index and Shore A hardness decreased slightly. Hot‐air ageing resistance and hot‐oil ageing resistance of the composites became better with increasing HNBR fraction. Thermal gravimetric analysis results demonstrated that the presence of MH and low HNBR fraction could improve the thermal stability of the composites. Differential scanning calorimeter revealed that the glass transition temperature (T_g) of the composites shifted toward low temperatures with increasing HNBR fraction, which was also confirmed by dynamic mechanical thermal analysis. Atomic force microscope images showed MH has a small particle size and good dispersion in the composites with high HNBR fraction. The flame retardancy, extremely good hot‐oil ageing, and hot‐air ageing resistance combined with good mechanical properties performance in a wide temperature range (?30°C to 150°C) make the EVM/HNBR/MH composites ideal for cables application. © 2009 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     

Development of new thermoplastic elastomers from blends of polyethylene and ethylene–vinyl acetate copolymer by electron‐beam technology

Electron beam‐initiated crosslinking of films prepared from a blend of low‐density polyethylene (LDPE) and ethylene–vinyl acetate (EVA) containing 45% vinyl acetate, with ditrimethylol propane tetraacrylate (DTMPTA), was carried out over a range of radiation doses (20–500 kGy), concentration of DTMPTA (1–5 parts by weight), and blend compositions. The gel fraction of the films increases with increase in the irradiation dose, DTMPTA level, and EVA content of the blends. The mechanical and dynamic mechanical properties of the films are also changed with the above variables. Reprocessibility studies revealed that the blends irradiated at 50 kGy and below are thermoplastic elastomers with a low permanent set. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1877–1889, 2001     

Effect of acrylic acid on the properties of recycled poly(vinyl chloride)/acrylonitrile–butadiene rubber blends

The effect of acrylic acid (AAc) on the torque, stabilization torque, mechanical energy, swelling behavior, mechanical properties, thermal stability, and morphological characteristics of recycled poly(vinyl chloride)/acrylonitrile–butadiene rubber (PVCr/NBR) blends was studied. The blends were melt mixed at a temperature of 150°C and rotor speed of 50 rpm. AAc was used to improve the compatibility of PVCr/NBR blends. Virgin PVCv/NBR blends were prepared to provide a comparison. It was found that PVCr/NBR + AAc blends exhibit higher stabilization torque, mechanical energy, stress at peak, and stress at 100% elongation, but lower elongation at break and swelling index than those of PVCr/NBR and PVCv/NBR blends. SEM study of the tensile fracture surfaces of the blends indicated that the presence of AAc increased the interfacial interaction between PVCr and NBR phases, thus improving the compatibility between PVCr and NBR phases. However, thermal gravimetry analysis of the blends showed that the presence of AAc decreased the thermal stability of PVCr/NBR blends. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2181–2191, 2005     

丁腈橡胶增容丁苯橡胶/聚氯乙烯共混体系

采用一系列结合丙烯腈质量分数不同的丁腈橡胶(NBR)作为丁苯橡胶(SBR)／聚氯乙烯(PVC)不相容共混物的增容剂,研究了SBR／PVC／NBR硫化胶的力学性能,并用扫描电子显微镜、傅里叶变换红外光谱仪和动态黏弹仪研究了该硫化胶的形态结构与相容性。结果表明,结合丙烯腈质量分数为20％～26％的NBR是SBR／PVC的优良增容剂,可提高共混物的力学性能,使SBR相和PVC相达到微细均匀化分散,并在两相之间形成了界面层,使得增容效果达到最佳。     

Natural rubber/nitrile butadiene rubber/hindered phenol composites with high-damping properties

New natural rubber (NR)/nitrile butadiene rubber (NBR)/hindered phenol (AO-80) composites with high-damping properties were prepared in this study. The morphological, structural, and mechanical properties were characterized by atomic force microscopy (AFM), polarized Fourier transform infrared spectrometer (FTIR), dynamic mechanical thermal analyzer (DMTA), and a tensile tester. Each composite consisted of two phases: the NR phase and the NBR/AO-80 phase. There was partial compatibility between the NR phase and the NBR/AO-80 phase, and the NR/NBR/AO-80 (50/50/20) composite exhibited a co-continuous morphology. Strain-induced crystallization occurred in the NR phase at strains higher than 200%, and strain-induced orientation appeared in the NBR/AO-80 phase with the increase of strain from 100% to 500%. The composites had a special stress–strain behavior and mechanical properties because of the simultaneous strain-induced orientation and strain-induced crystallization. In the working temperature range of a seismic isolation bearing, the composites (especially the NR/NBR/AO-80 (50/50/20) composite) presented a high loss factor, high area of loss peak (TA), and high hysteresis energy. Therefore, the NR/NBR/AO-80 rubber composites are expected to have important application as a high-performance damping material for rubber bearing.     

Hydrogenation of acrylonitrile–butadiene rubber latexes

The hydrogenation of acrylonitrile–butadiene rubber (NBR) latex was carried out by a system consisting of hydrazine hydrate and hydrogen peroxide, with boric acid as catalyst. Highly saturated hydrogenated NBR (HNBR) latex was obtained through the optimization of the reaction conditions. The dried HNBR was found to be heavily gelled. The cause for the crosslink of dried hydrogenated NBR products was investigated. With the improvement of the hydrogenation system, that is, by adding gel inhibitor to the system, the crosslinking was controlled to a large extent, and dried HNBR with gel content of about 3% was prepared by the improved system. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2072–2078, 2004     

Fracture behaviour of acrylonitrile–butadiene rubber/clay nanocomposite

A new fracture behaviour is described for acrylonitrile–butadiene rubber/clay nanocomposite. The nanocomposite is prepared by melt mixing the organo‐treated montmorillonite into the rubber matrix, together with a peroxide curative, and crosslinked by conventional compression moulding for typical rubbers. A considerable enhancement in stiffness is observed without serious sacrifice in ultimate strength. A totally different tear morphology of a series of regularly‐spaced tear ridges parallel to the direction of tearing was observed instead of the typical ‘cross‐hatched morphology’ of conventional rubber composites. © 2001 Society of Chemical Industry     

Effect of anhydride‐modified ethylene–propylene–diene rubber and ethylene–vinyl acetate copolymers on the compatibilization of nitrile rubber/ethylene–propylene–diene rubber blends

The effects of maleic anhydride modified ethylene–propylene–diene rubber (EPDMMA) and maleic anhydride modified ethylene–vinyl acetate (EVAMA) on the compatibilization of nitrile rubber (NBR)/ethylene–propylene–diene rubber (70:30 w/w) blends vulcanized with a sulfur system were investigated. The presence of EPDMMA and EVAMA resulted in improvements of the tensile properties, whereas no substantial change was detected in the degree of crosslinking. The blend systems were also analyzed with scanning electron microscopy and dynamic mechanical thermal analysis. The presence of EVAMA resulted in a blend with a more homogeneous morphology. The compatibilizing effect of this functional copolymer was also detected with dynamic mechanical analysis. A shift of the glass‐transition temperature of the NBR phase toward lower values was observed. The presence of EPDMMA and EVAMA also increased the thermal stability, as indicated by an improvement in the retention of the mechanical properties after aging in an air‐circulating oven. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2408–2414, 2003     

橡胶阻尼材料的研究进展

分析了橡胶材料的阻尼机理,重点讨论了丙烯酸酯橡胶、聚氨酯、丁基橡胶、丁腈橡胶和聚乙酸乙烯酯橡胶经过改性制备橡胶阻尼材料的研究进展,指出了橡胶阻尼材料的发展方向。     

国内丁腈橡胶生产情况及市场分析

综述了国内外丁腈橡胶的生产及市场情况，对国内丁腈橡胶的市场发展趋势进行了分析和预测。并针对入世后国内丁腈橡胶行业存在的不足提出了几点建议。