Effect of Short Glass Fiber on Structure and Mechanical Behavior of an Ethylene-1-Octene Copolymer

Abstract

Several composites with short glass fiber of a copolymer of ethylene and 1-octene, synthesized with a metallocene catalyst, have been prepared, up to a fiber content of 60 wt.-%. The effect of the fiber on the structure and mechanical behavior has been analyzed. Though the peak melting and crystallization temperatures are not altered, the incorporation of the fibers leads to a slightly higher crystallinity in the composites, and the mechanical behavior is modified. Since fibers introduce rigidity, both Young's modulus and the microhardness increase and either elongation or stress-at-break decrease as the glass fiber content rises in the composite. However, the dependence of Young's modulus on the fiber content is very different from that of the microhardness. Moreover, an essentially homogeneous deformation takes place along the different materials analyzed, but, depending upon reinforcement composition, one or two yield stresses are observed. Finally, all specimens show three viscoelastic mechanisms. Due to the rigidity introduced by fibers and their influence on the crystallinity, the distinct relaxations in the composites are shifted to higher temperatures and the apparent activation energies associated with them are higher. The effect of fiber is more significant in either the β or α processes than in that of the γ. The increase of the temperature of the α relaxation is particularly important and thus the incorporation of the fibers considerably enlarges the useful temperature range, which can expand the application fields of the plain copolymer.