ABSTRACT:The crosslinking of metallocene ethyleneoctene copolymer was investigated. The crosslinked polymers were prepared using two different techniques, i.e., peroxide crosslinking and silane-water crosslinking. In the former, the crosslinking reaction was conducted in a twinscrew extruder, in the presence of dicumylperoxide. In the latter, the polymer was first grafted with vinyl trimethoxysilane in the extruder and subsequently crosslinked with water. The paper aims at investigation of the differences between these two techniques, in terms of processing and product mechanical and thermal properties. The results showed that the silane-crosslinked polymers could be prepared with much higher gel contents than the peroxidecrosslinked samples. The silane-crosslinked polymers also retained the elastomeric characteristics of the pure polymer and showed remarkably higher extensibility, better thermal stability, and energy storage capacity. An explanation for the property differences between peroxide-crosslinked and silane-crosslinked polymers was proposed.

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Blown films from poly(butylene adipate-coterephthalate) and poly(lactide) (PLA) blends were investigated. The blends were prepared in a twin-screw extruder, in the presence of small amounts of dicumyl peroxide (DCP). The influence of DCP concentration on film blowing, rheological, mechanical, and thermal properties of the blends is reported in this article. Rheological results showed a marked increase in polymer melt strength and elasticity with the addition of DCP. As a consequence, the film homogeneity and the stability of the bubble were improved. The modified blend films, compared with the unmodified blend, showed an improvement in tensile strength and modulus with a slight loss in elongation.Fourier transform infrared and gel results revealed that chain scission and branching were more significant than crosslinking when the DCP loadings in the blends were not higher than 0.7%. A reduction in melt temperatures of PLA was observed due to difficulty in chain crystallization. The concentrations of DCP strongly affected the melting temperatures but had an insignificant effect on the decomposition behavior of the blends. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 124: [4986][4987][4988][4989][4990][4991][4992] 2012

In this article, we present an efficient method for isolating cellulose nanofibers from para rubberwood sawdust with a combination of chemical, mechanical, and ultrasonic treatments. The effects of the alkali concentration and treatment pathway on the cellulose structure and properties are discussed. The reinforcing efficiency of the resulting fibers on poly(vinyl alcohol) (PVA) composites was characterized. Field emission scanning electron microscopy and atomic force microscopy results revealed a well-organized network of the nanofibers with diameters in the range 20-80 nm and lengths of micrometer-scale dimensions. Fibers with a high crystallinity of 83% having a cellulose I structure were prepared by an isolation process involving a mild alkali solution and delignification before acid hydrolysis. Clear composite films with significant improvements in their modulus (by 100%) and strength (by 80%) were obtained by the addition of 7 wt % fiber. Strong interaction between the fibers and PVA was evident from dynamic mechanical analysis and differential scanning calorimetry.

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