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Composites Decreases (composite + decrease)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Crystalline morphology and dynamical crystallization of antibacterial ,-polypropylene composite

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008
Xin Chen
Abstract The crystalline morphology and dynamical crystallization of antibacterial polypropylene composite and pure polypropylene were investigated via differential scanning calorimeter (DSC), wide angle X-ray diffraction (WAXD), and real-time hot-stage optical microscopy (OM). The results reveal that the crystalline morphology of antibacterial PP composites changes with variations of the crystallization conditions and compositions. The crystalline phase consists of both ,-PP and ,-PP crystals. The content of ,-PP decreases with the increase in antibacterial agent content and cooling rate. With the addition of ,-nucleating agent, the morphologies of all dynamically crystallized antibacterial PP composites show no obvious spherulitic morphology, and the decrease of crystal perfection and the increase of nucleation density of antibacterial PP composite system could be observed. With the increase of antibacterial agent content, the overall crystallization rates of the antibacterial PP composite increase dramatically, while the content of ,-PP in all antibacterial PP composite decrease distinctly under given cooling conditions. These results can be explained by the interruptive effect of antibacterial agent on interactions of ,-nucleating agent components and the obstructing effect of antibacterial agent on the mobility of PP chains in melts. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Effects of poly(ethylene- co -propylene) elastomer on mechanical properties and combustion behaviour of flame retarded polyethylene/magnesium hydroxide composites

POLYMER INTERNATIONAL, Issue 7 2002
Zhengzhou Wang
Abstract Magnesium hydroxide-based halogen-free flame retarded linear low density polyethylene composites containing poly(ethylene- co -propylene) elastomer were prepared in the melt process and subsequently vulcanized thermally. Influences of the elastomer on the mechanical properties, combustion characteristics and crystallization behaviour of polyethylene/magnesium hydroxide composites have been investigated. The results from the mechanical tests show that the incorporation of a suitable amount of elastomer into polyethylene/magnesium hydroxide composites after vulcanization can increase both the tensile strength and elongation greatly, compared with those of the composites without the elastomer. It has been found that the properties such as limiting oxygen index, UL-94 rating, the time to ignition and the rate of heat release of polyethylene/magnesium hydroxide/elastomer composites are all improved in comparison with polyethylene/magnesium hydroxide composites at the same retardant level. Scanning electron microscopy studies show that the incorporation of the elastomer into polyethylene/magnesium hydroxide composites improves the compatibility between the filler and the polymer substrate. The degrees of crystallinity of polyethylene/magnesium hydroxide/elastomer composites decrease with increasing the elastomer content. © 2002 Society of Chemical Industry [source]

Thermally Stimulated Currents of SiO2/Low-density Polyethylene Micro- and Nanocomposites

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2010
Yi Yin Non-member
Abstract Composite samples of low-density polyethylene (LDPE)/nano-SiO2 and LDPE/micro-SiO2 were prepared with the method of double-solution mixture. Depolarization currents of all samples were investigated with thermally stimulated depolarization current (TSDC). It was found that the currents of both composites increased with the loading level of nano-SiO2 and/or micro-SiO2, and that the peak width of each composite is greater than that of pure LDPE. In addition, the peak position of the nanocomposite shifts as the loading level increases, while that of the microcomposite does not shift significantly. In order to understand activation energy of both composites and pure LDPE, the initial-rise method was used to analyze the depolarization current. It was found that LDPE has the greatest activation energy among all samples and the activation energy of both composites decreases with increasing loading levels. Moreover, the activation energy of the nanocomposite is less than that of the microcomposite at each of the same loading level. As the nano-SiO2 loading level reaches 5.0%wt, the composite has the lowest activation energy of 0.25 eV. In addition, dielectric spectra of all samples were investigated in the range of 10,4 to 107 Hz, and it was found that the peak position of loss tangent varied consistently with the TSDC curves as the loading levels of nano-SiO2 and/or micro-SiO2 were increased. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Effect of different types of peroxides on properties of vulcanized EPDM + PP blends

POLYMER COMPOSITES, Issue 10 2010
Witold Brostow
Mechanical and tribological behavior of several dynamic vulcanizate blends of polypropylene (PP) with ethylene-propylene-diene rubber (EPDM) was examined and compared with those of uncrosslinked blends. Vulcanization was performed using two types of organic peroxides combined with (meth)acrylate coagent. The effect of different types and concentrations of peroxides as crosslinking agents on the properties of the resulting materials were investigated. Dicumyl peroxide (DCP) provides higher reactivity and exhibits nearly the same crosslinking efficiency for both 60/40 and 50/50 blends; almost fully crosslinked samples are obtained if the compound contains 1.0 or 2.0 wt% DCP. These results correlate to the gel content and mechanical properties of our materials. Variation of PP + elastomer ratio does not have a significant influence on friction. From 60/40 group of composites, lower friction values were obtained for samples cured with 0.5 wt% benzoyl peroxide (BP) and 1.0 wt% DCP. The tribological properties of the samples with higher amount of DCP show rubbery rather than a toughened thermoplastic behavior. Wear of the composites decreases with the increasing concentration of the curing agent. Compared to BP, the samples cured with DCP display lower wear. POLYM. COMPOS., 31:1678,1691, 2010. © 2010 Society of Plastics Engineers. [source]