Composites made from acetylated lignocellulosic fibers of different origin

Abstract

Conventional technology for manufacturing nonwoven fiber mats for the production of complex shaped fiber composite products involves a needling step in which textile fibers are entangled with lignocellulosic fibers coated with a thermosetting resin. The technique used in this project for the production of nonwoven fiber mats involves bicomponent thermoplastic fibers that, upon heating and subsequent cooling, form an elastic network together with the lignocellulosic fibers. Powdered phenolic resin of the novolak type was added to the mat forming step. The main objectives of this study were : to investigate how the composition of the fiber mat affects molding ability, and to ensure that the benefits of acetylation, i.e., the dimensional stability of the molded product, remain. An experimental design was used to evaluate the effects resulting from the following factors : the type of lignocellulosic fiber, with or without the acetylation of lignocellulosic fiber, the type and concentration of thermoplastic fiber. The lignocellulosic fibers examined were softwood, aspen, wheat straw, beech, waste wood and recycled paper fiber. The presence of thermoplastic fibers has no negative effect upon the improvement of dimensional stability obtained by acetylation. Both the concentration level and type of thermoplastic fiber had a great impact on the tensile strength of the fiber mat and its molding ability. Aspen and softwood fiber mats showed good results, even at a low thermoplastic content. It was shown that provided the proper type and concentration of thermoplastic fiber are chosen, a wide variety of lignocellulosic fibers can be used to produce fiber mats with good molding ability.