Ternary miscible blends based on various ratios of poly(vinyl alcohol) (PVA), poly(acrylamide) (PAM) and carboxymethyl cellulose (CMC) were prepared by solution casting in the form of thin films. The structure‐property behavior of the ternary PVA/PAM/CMC blends, before and after they had been exposed to various doses of electron beam irradiation, was investigated by FT‐IR spectroscopy, SEM, XRD and stress‐strain curves. The visual observation showed that the cast films of the individual polymers PVA, PAM, and CMC and their blends over a wide range of composition are clear and transparent indicating the miscibility of PVA/PAM/CMC ternary blends. The FT‐IR analysis of pure polymers or their ternary blends before or after electron beam irradiation proved the formation of hydrogen bonding. In addition, it was found that the intensity of the different absorption bands depends on the ratio of PAM and CMC in the ternary blend. The XRD patterns showed that the peak position for the ternary blends decreases with increasing the ratio of CMC in the blend. However, the peak position for the ternary blend based on equal ratios of pure polymers was not affected by blending and was found in the same position as in the XRD pattern of pure PVA. The SEM micrographs give support to the visual observation indicating the complete miscibility of PVA/PAM/CMC ternary blends. The improvement in morphology leads to improvement in the tensile mechanical properties of the ternary polymer blends. 相似文献
High styrene rubber (HSR)/styrene butadiene rubber (SBR) blends at different ratios were exposed to various doses of electron beam irradiation. The effect of irradiation dose and blend ratios on the mechanical properties and shape memory characteristics in terms of strain fixation) rate (Rf) and strain recovery rate (Rr) was investigated. The results revealed that rich styrene blends displayed higher tensile strength and hardness than low styrene content blends at all irradiation doses. However, elongation at break, and toughness were lower for rich styrene content. Also, it was observed that for most specimens, the tensile strength, elongation at break and hardness increases up to100 kGy. Increasing irradiation doses resulted in slight deterioration in some mechanical properties only for low styrene content at150 kGy. According to the normalized tensile stress at 25% elongation, it was found that the contribution of irradiation in enhancing the mechanical properties is higher for rich butadiene blends. On the other hand, it was observed that rich styrene content blends possess higher Rf and Rr at all the irradiation doses and stretching temperatures. However, the increase of irradiation dose decreases Rf values; the extent of this decrease depends on the blend ratios. Conversely, for all blends, Rr were increased by increasing irradiation dose and styrene content ratios. 相似文献
Abstract Some oxygen‐containing groups such as C?O and C–O were introduced onto high‐density polyethylene (HDPE) chains by an ultraviolet irradiation technique without the addition of any additives, and this method causes no chemical pollution to the environment. This groups content increases with irradiation time. Gelation took place in the HDPE irradiated for 16?hr, and the gel content also increases with irradiation time. After irradiation, the crystal shape and crystalline plane spacing of HDPE remained unchanged; the melting temperature decreased, whereas the crystallinity and hydrophilicity increased. Due to the introduction of polar groups, the interfacial interaction between sericite–tridymite–cristobalite (STC) particles and irradiated HDPE, and the mechanical properties of irradiated HDPE/STC (60/40) blend were improved. Compared with the yield and impact strength of HDPE/STC (60/40) blend, those of the corresponding blend irradiated for 16?hr were increased from 25.1?MPa and 56?J/m to 29.1?MPa and 283?J/m, respectively. 相似文献
The copolymerizations of a gaseous monomer (ethylene) and a liquid monomer (vinyl acetate) via emulsion and miniemulsion polymerizations are reported. Reactions in which the vinyl acetate was introduced in both batch and semibatch modes are carried out. (Ethylene introduction is always in a semibatch model since the polymerization is carried out under a constant pressure of ethylene in the reactor headspace.) The results are compared, drawing the conclusion that miniemulsion copolymerization has an advantage over conventional emulsion polymerization for monomers with very low water solubility (including gaseous monomers) due to their nucleation in monomer droplets without transport through the aqueous phase.
Summary: Processing and compatibilization effects of a commercially available styrene/ ethylene-butylene/ styrene (SEBS) compatibilizer on the morphological structure, rheological and mechanical properties of blends of polystyrene (PS) and high density polyethylene (HDPE) were investigated. The rheological behaviour of the blends melt during processing was followed by measuring torque; extrusion capacity output and melts back-pressure in a twin screw extruder. The processing parameters were decreased with the HDPE content. The results show that SEBS compatibilizer can yield compatibilization by substantially reducing torque and increasing the back-pressure. However, the Hurst indices of melt processing parameters are increased with compatibilization. Near-infrared spectra had been described by the Hurst index HNIR which is then related to HDPE content in the blends. The correlation between the blend compositions, morphological structure, mechanical and rheological properties and processing parameters was established and discussed on base of correlation with the fractal indices obtained from the SEM microphotographs of PS/HDPE/SEBS blends. 相似文献
Mechanical and dynamic mechanical properties of natural rubber/recycled ethylene-propylene-diene rubber (NR/R-EPDM) blends were simultanoeusly enhanced by electron beam (EB) irradiation. The cross-linking promoter, trimethylolpropane triacrylate (TMPTA), was also introduced into the blends to induce the cross-linking. By applying EB irradiation, the tensile modulus, hardness, swelling, cross-link density, and storage modulus increased with increase in the irradiation dose; an irradiation dose of 50 kGy was efficient to gain optimum tensile strength. The formation of irradiation-induced cross-links after EB irradiation is a major concern for the enhancement of mechanical, swelling resistance, and dynamic mechanical properties of the blends. 相似文献
Controlled radical polymerization of ethylene using different commercially available, cheap, and non-toxic iodo alkyls is performed by iodine transfer polymerization (ITP) under mild conditions (≤100 °C and ≤200 bar). The formed well-defined iodo end-capped polyethylene (PE−I) species is very stable upon storage. Narrow molar-mass distributions (dispersities around 1.6) were obtained up to number average molar masses of 7300 g mol−1. The ethylene copolymerization by ITP (ITcoP) with vinyl acetate allowed to form a broad range of poly(ethylene-co-vinyl acetate) (EVA) containing from 0 to 85 mol % of VAc unit. In addition, EVA-b-PE block copolymers or EVA-b-EVA gradient block copolymers with different content of VAc in the blocks were obtained for the first time using ITP. Finally, reactivity trends were explored by a theoretical mechanistic study. This highly versatile synthetic platform provides a straightforward access to a diverse range of well-defined PE based polymer materials. 相似文献
Summary: Aiming the development of high toughness polymer materials, blends of poly(styrene-co-acrylonitrile) (SAN) and poly(butadiene-co-acrylonitrile) (NBR) rubbers, with contents of acrylonitrile (AN) varying from 21 to 45%, were prepared by casting, coprecipitation and monoscrew extrusion followed by injection molding. SAN/NBR blends, prepared in the compositions (w/w) 90/10, 80/20, 70/30, 60/40, and 50/50, were characterized by differential scanning calorimetry (DSC) and Izod impact tests. DSC analyses showed that blends with 33% AN NBR prepared by casting, and with 39% AN NBR prepared by coprecipitation, are partially miscible at 60/40, 70/30 and 80/20 (SAN/NBR) compositions and immiscible for 50/50 compositions. On the other hand, 90/10 SAN/NBR systems were totally miscible. The blends with 45% AN NBR prepared by coprecipitation showed partial miscibility to 50/50, 60/40, 70/30 and 90/10 compositions and total miscibility to 80/20 composition. The NBR addition results in a significant increase in the impact resistance, strongly dependent on the blend composition and the NBR AN content. The best result of impact resistance — 75.2 ± 8.6 (kJ · m−2) — was obtained for SAN/NBR 50/50, using 45% AN NBR. This value is 15.7 times bigger than that for pure SAN -4.8 ± 0.7 (kJ · m−2). 相似文献
The gas barrier properties of ethylene vinyl alcohol copolymer (EVOH) against oxygen, carbon dioxide and water vapor have been widely investigated in relation to different material characteristics, environmental conditions and new processing technologies. Recently, EVOH is gaining more attention as a barrier material against other gases and organic substances such as aromas, flavors, fuels, chemicals (e.g., BTEX), and as a functional barrier, e.g., to avoid mineral oil migration. This review contains an update on permeability data of EVOH emphasizing its potential as a barrier material for new and versatile applications in food and pharmaceutical packaging, agriculture, construction, automotive, etc. 相似文献