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1.
A systematic dielectric and mechanical study was carried out on an ethylene propylene diene monomer (EPDM) and a nitrile rubber (NBR) blended with polyacrylamide (PAM). From the compatibility investigations, it was found that EPDM/PAM is incompatible while NBR/PAM is semicompatible. To overcome the problem of phase separation between rubber and PAM, PAM was grafted with two different monomers, acrylonitrile (AN) and acrylic acid (AA), and added with 10 phr to both EPDM and NBR. Poly(vinyl chloride) (PVC) was also added as a compatiblizing agent to both types of blend. It was concluded that the addition of either a grafted polymer or PVC to the rubber–plastic blend could improve to some extent the compatibility of such blends. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2053–2059, 1998 相似文献
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Isotactic polypropylene blends with 0–20 vol % thermoplastic elastomers were prepared to study the influence of elastomer particle size on mechanical properties. Polystyrene-block-poly(ethene-co-but-1-ene)-block-polystyrene (SEBS) was used as thermoplastic elastomer. SEBS particle size, determined by means of transmission electron and atomic force microscopy, was varied by using polypropylene and SEBS of different molecular weight. With increasing polypropylene molecular weight and, consequently, melt viscosity and decreasing SEBS molecular weight, SEBS particle size decreases. Impact strength of pure polypropylene is almost independent of molecular weight, whereas impact strength of polypropylene blends increases strongly with increasing polypropylene molecular weight. The observed sharp brittle–tough transition is caused by micromechanical processes, mostly shear yielding, especially occurring below a critical interparticle distance. The interparticle distance is decreasing with decreasing SEBS particle size and increasing volume fraction. If the polypropylene matrix ligament between the SEBS particles is thinner than 0.27 μm, the blends become ductile. Stiffness and yield stress of polypropylene and polypropylene blends increase with increasing polypropylene molecular weight in the same extent, and are consequently only dependent on matrix properties and not on SEBS particle size. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1891–1901, 1998 相似文献
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Binary polymer films containing different percentages of corn starch and low-density polyethylene (LDPE) were exposed to soils over a period of 8 months and monitored for starch removal and chemical changes of the matrix using FTIR spectroscopy. A standard curve using the area of the C? O stretch band and an empirical second-degree polynomial to fit the data made it possible to calculate starch concentration over a wide range (0–46% by mass). Starch removal was found to proceed rapidly during the first 40 days and to nearcompletion in very high starch blends (52% and 67% by weight). Starch removal was slower, consisting of mostly surface removal in 29% starch blends. Weight loss data supported spectroscopic data showing similar gross features. Weight loss and spectroscopic data were consistent with percolation theory and suggested that starch removal continues past 240 days. Degradation rates in different soils containing different amounts of organic matter were approximately the same after a period of a few weeks. IR analysis did not show significant chemical changes in the polyethylene matrix after 240 days. However, the matrix did show evidence of swelling, an increase in surface area, and removal of low molecular weight components. 相似文献
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The electrical and mechanical properties of new conductive rubber composites based on ethylene–propylene–diene rubber, acrylonitrile butadiene rubber (NBR), and their 50/50 (weight ratio) blend filled with conductive black were investigated. The threshold concentrations for achieving high conductivity are explained on the basis of the viscosity of the rubber. The electrical conductivity increases with the increase in temperature whereas the activation energy of conduction decreases with an increase in filler loading and NBR concentration in the composites. The electrical hysteresis and electrical set are observed during the heating–cooling cycle, which is mainly due to some kind of irreversible change occurring in the conductive networks during heating. The mechanisms of conduction in these systems are discussed in the light of different theories. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 887–895, 1999 相似文献
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Blends of styrene–butadiene rubber (SBR) and natural rubber (NR) were prepared and their morphology, transport behavior, and dynamic mechanical and mechanical properties were studied. The transport behavior of SBR/NR blends was examined in an atmosphere of n‐alkanes in the temperature range of 25–60°C. Transport parameters such as diffusivity, sorptivity, and permeability were estimated. Network characterization was done using phantom and affine models. The effect of the blend ratio on the dynamic mechanical properties of SBR/NR blends was investigated at different temperatures. The storage modulus of the blend decreased with increase of the temperature. Attempts were made to correlate the properties with the morphology of the blend. To understand the stability of the membranes, mechanical testing was carried out for unswollen, swollen, and deswollen samples. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1280–1303, 2000 相似文献
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The hypothetical fractionation of polyethylene–polypropylene blends was carried out by assuming adequate molecular weight distribution and partition of polymer between two liquid phases for each hompolymer, and also by using the previously reported data of the molecular weight dependence on solubility. The experimental fractionation of blends was also carried out by the solvent gradient method, and the results were compared with those obtained by the hypothetical fractionation. Both results agreed fairly well in various distribution forms. Therefore, these results may provide valuable information for component or compositional analysis of unknown samples or copolymerization products. 相似文献
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Four polystyrene–polyurethane mechanical blends were prepared with 5, 10, 20, and 40% thermoplastic polyurethane, respectively. Their impact properties were compared with pure polystyrene and commerical types of impact polystyrene. The rheological properties of the blends were studied with DSC and dynamic mechanical spectroscopy. It was found that addition of softer polyurethane conglomerates embedded inside the polystyrene matrix, although increasing the toughness of the blend as expected from addition of the softer particulate, also increased the glassy region of the blends by shifting their Tgs to higher temperatures. A theory based on the interaction of phases was propounded explaining this phenomenon. 相似文献
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The role of lead compounds in blends of polyethylene and silicone has been studied as a flame retardant. It has been established that these compounds work in the solid phase and that a gas-forming reaction is important to produce a foamed char which retards further combustion. 相似文献
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The dynamic mechanical response of several binary mixtures of a styrene–butadiene copolymer and high cis‐polybutadiene has been studied. The loss tangent and shear modulus were measured with a free damping torsion pendulum at temperatures between 143 and 343 K in argon atmosphere. From the loss tangent data the glass transition temperature of each sample was evaluated. The results can be represented by the Fox equation that relates the glass transition temperature of the blend with that of constituent polymers. The influence in the loss tangent data of the crystallization of the high cis BR used in the blend is discussed. A study of the separation of the crystalline and amorphous parts in the polybutadiene using the storage modulus data is presented. Finally, the loss of crystallinity at different contents of SBR in the blend is analysed using the dynamic mechanical data. © 2000 Society of Chemical Industry 相似文献
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J. W. Teh 《应用聚合物科学杂志》1983,28(2):605-618
The structure and mechanical properties of blends of low-density polyethylene and isotactic polypropylene were studied. The blends behaved like a simple composite obeying the rule of mixture for the modulus dependence on composition. Tensile strength of the LDPE was enhanced with the addition of PP but elongation at break was drastically reduced for all blend compositions. Studies with WAXD, hot-stage microscope, and DSC indicated lack of interaction between the LDPE and the PP. The crystallographic structure of LDPE and PP remained unchanged. However, the spherulite size of the PP was found to be reduced in the presence of LDPE, possibly due to an increase in nucleation density. 相似文献
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A mixture of high‐density polyethylene and its low‐molecular‐weight analogue heptadecane was studied. The mixture behaved as a compound, that is, differently from polyethylene. Heptadecane reduced the crystallinity of polyethylene, and it intricately changed the concentration of centers sorbing phenyl‐β‐naphthylamine, the antioxidant, and simultaneously changed the equilibrium constant of sorption. Heptadecane also prolonged the duration of the antioxidant action in polyethylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2597–2603, 2003 相似文献
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When extruding a blend of low density polyethylene (LDPE) and a technical grade of sodium lignosulfonate through a capillary it was observed that LDPE formed fibers in a matrix of the lignosulfonate. With short capillaries and low shear rates, short fibers of LDPE with lengths between 0.5 and 5 mm and with diameters in the range 2–20 μm can be produced. Since sodium lignosulphonate is water-soluble, the LDPE fibers can easily be isolated. Such fibers can be used for synthetic wood pulp or in nonwoven types of applications. 相似文献
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Permeability to water vapor and oxygen, elastic modulus, tensile strength, and impact strength of polystyrene–polypropylene and high-impact polystyrene–polypropylene blends were determined as functions of blend composition and morphology. Three types of styrene–butadiene block copolymers were tested as compatibilizers and found to improve mechanical properties of blends. The experimental data on permeability and modulus were compared with the predictions for the studied binary and ternary blends. The predictive scheme employs a two-parameter equivalent box model and the data on phase continuity of constituents calculated using general equations derived from percolation theory. Blends with decreased permeability and plausible mechanical properties were proposed with regard to intended applications in food packaging. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 2615–2623, 1998 相似文献
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A sulfonated polystyrene (SPS) and a polyurethane containing a tertiary amine group (NPU) were blended in solution. The effect of blend composition was studied in the blend of SPS with 9.83 mol % of sulfonation (SPS-9.83) and NPU with 33 mol % of MDEA (NPU-33). As the SPS concentration increases, a significant improvement of miscibility is observed. The tensile strength of the blends is greater than either pure NPU or SPS. A maximum strength and a maximum density occur at 50 wt % SPS. The stress–strain curve shows a well-defined yield when the SPS concentration in the blend is 30 or 50 wt %. The yield is more dramatic in the blend with 50 wt % SPS than that of 30 wt % SPS. At a lower SPS concentration, the blend behaves like a rubber, while a higher SPS concentration in the blend results in a brittle failure before yield. An increase in the sulfonation level of SPS in the SPS–NPU-33 (30/70) blends leads to an improved miscibility. A significant enhancement of tensile strength is observed as the sulfonation increases. A clear yield point on the stress–strain curves occurs when the sulfonation of SPS in the blend is 4.79 mol % or greater. Increasing the MDEA content of NPU up to 8.3 mol % can lead to an enhancement of tensile strength. A further increase in the MDEA content has little influence on the tensile strength, but a clear yield on the stress–strain curve occurs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2035–2045, 1998 相似文献
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A high-temperature gradient HPLC method has been developed for the analysis of polyethylene–polypropylene blends. For the first time it was possible to separate these polyolefin blends by a chromatographic technique which is operating at 140 °C. Blends of a commercial polypropylene and a medium molar mass linear polyethylene were separated using a mobile phase of ethylene glycol monobutylether (EGMBE) and 1,2,4-trichlorobenzene (TCB) and silica gel as the stationary phase. With the use of n-decanol as sample solvent, a precipitation–redissolution mechanism for polyethylene (PE) was established while polypropylene (PP) is eluted in size exclusion mode. 相似文献
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Thermodynamics of interaction, adhesive properties, and the structure of acrylonitrile-butadine rubber/low density polyethylene blends have been investigated. Enthalpy and entropy components of interaction parameters supporting an incompatibility of studied systems and a possibility of highly organized structure formation on the phase interface were determined by inversion gas chromatography. The formation of highly organized structures on the interface is made possible by a local diffusion of polybutadiene fragments into polyethylene phase. That is why acrylonitrile microblocks are oriented. By this manner adhesion between rubber and polyethylene phase is enforced and simultaneously a number of morphological changes take place. 相似文献
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The use of graft copolymers of styrene onto polyethylene as additives to improve the mechanical properties of polyethylene–polystyrene blends is described. Blends containing equal proportions of low-density polyethylene and polystyrene were selected for this study since this composition represents the poorest balance of properties in this system. Graft addition generally increased both the yield strength and the elongation at break of the blend. Of the grafts employed, those prepared at an irradiation dose near 0.5 megarad appear optimal for this purpose. These conditions apparently balance the beneficial effects of grafting extent and the detrimental effects of crosslinking, both of which increase with irradiation dose. 相似文献
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Lead compounds and silicone gum when blended into polyethylene act as synergistic fire retardant. The incorporation of lead into the polymer network via lead carboxylate formation through polyethylene grafted with maleic anhydride has been studied as a means of improving the metal dispersion and flammability behavior. Lead was also incorporated directly into a polymer backbone via the formation of lead polyesters. The use of other metal compounds as fire retardant additives has also been studied. No special behavior was seen for polymer-bound lead relative to non-polymer bound lead, and other metals were not found to be effective replacements for lead in polyethylene graft maleic anhydride. 相似文献
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《塑料、橡胶和复合材料》2013,42(10):441-448
AbstractThe influence of solvent uptake (%) on the electrical resistivity S of ethylene propylene diene monomer rubber (EPDM)/acrylonitrile butadiene rubber (NBR) blends filled with different concentrations of high abrasion furnace carbon black has been studied. The effects of the EPDM/NBR weight ratio and carbon black content on the room temperature resistivity of the composites were elucidated in detail. The performance of these sensors depends on a number of parameters, including the geometry and concentration of the conductive component dispersed in the polymer. Direct current current–voltage I–V characteristics of the filled rubber blends were studied at room temperature. The current–voltage relationship can be expressed as I?=?AVB, where A and B are constants that show capability and property of electrical conduction respectively. The I–V curve can be divided into ohmic and non-ohmic regions. A number of important parameters, namely, Schottky and Poole–Frenkel effects, have been determined. 相似文献