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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The development of structure and viscoelastic properties during silane crosslink reaction in metallocene ethylene-octene copolymer has been investigated. Using attenuated and transmission infrared spectroscopy, the concentrations of certain functional groups and change in sample thickness were monitored, giving the information on the progress of crosslink reaction. The evolution of crosslink content and viscoelastic properties was analyzed using a parallel-plate rheometer. The results showed that crosslinking process started with the hydrolyzation of methoxy groups in the near-surface layer, proceeding in a diffusion manner. At this stage no silanol groups could be detected, revealing that the condensation occurred promptly after hydrolyzation. The internal crosslink could not begin until there are sufficient water molecules in the surrounding. A water by-product from the condensation reaction played an essential part in the center region. The rheological data showed a reduction in magnitude of creep compliance. As the reaction proceeded, more networks took place within an existing gel. The materials, then, acted more like elastic and exhibited an improvement in ability for recovery process. The immobilization of chain segments, due to the presence of tight network, disallowed conformations necessary for crosslink reaction and a certain amount of hydrolyzable groups and silanol groups remained after a long crosslinking process.

This article relates to the melt-processing and properties of polylactic acid (PLA) reinforced with cellulose microfibrils (CMFs). The CMFs with diameters of 20-80 nm and lengths in the order of microns were isolated from wood sawdust. The purpose of the present study was to find a simple method to overcome the problems associated with feeding and aggregation of the nanoscale fibers in PLA melt. Two fiber carriers were compared, that is, natural rubber (NR) latex and polyethylene glycol (PEG) with a molecular weight of 4000 g mol À1. The results showed that with the aid of carrier, CMFs were successfully dispersed in the composites, enabling the strong reinforcing action of the fibrils to be realized. The type of carriers used had significant effects on the final properties of the PLA composites. Dynamic mechanical analysis results showed an eightfold improvement in modulus at elevated temperature (90 C) for the composite with 3 wt% CMFs using PEG as carrier. This enhancement was attributed to the combined effects of fiber reinforcement and cold crystallization induced in the PLA. With NR latex as carrier, the composite of high tensile strength was achieved by introducing the epoxidized rubber (ENR) in a ratio of 2:3 (ENR:NR) as a compatibilizer to improve adhesion between phases in the composites.

In many applications, e.g., wire and cable insulation, hot water pipe, high-temperature properties of polymer are essential. This article presents the use of silane crosslinking together with the addition of particular filler in improving the thermal and mechanical properties of ethylene-octene copolymer (EOC). The effects of filler surface characteristics on siloxane network structure developed and final properties of the crosslinked products are discussed. The results show an increase in the decomposition temperature of EOC more than 50 C after modification. Only crosslinked composites are able to withstand the hightemperature environment of aging test which is beyond the melting temperature of the matrix polymer. The crosslinked composites filled with calcium carbonate show superior properties to those with silica, due to a higher crosslink density and tighter network structure formed. The silane coupling mechanism and the presence of bound polymer on silica surfaces cause difficulties for the crosslink formation in the silica filled systems. However, an advantageous influence of both silane coupling and crosslink reaction in the silica filled composites is seen on the enhanced tensile strength and modulus of the materials.