Plastics go on a natural-fiber diet

Natural-fiber feedstock is an attractive alternative to glass fiber for reinforcing thermoplastic composites. Using natural fibers to reinforce thermoplastics produces composites that are low cost, lightweight, and easy to recycle. Physical properties of reinforced thermoplastics can vary with the size and type of fiber, processing methods, and many other factors. This table is intended to provide only a general comparison of glass versus natural-fiber reinforcement. In-line compounding preheats fibers and mixes composite feedstock immediately before molding, without a cooling interval. This helps retain virgin material properties and maintain uniform fiber distribution in the finished part. Fibers and fillers are commonly used to boost the strength of virgin plastic. Most engineers are familiar with glass-fiber-reinforced thermoplastic composites, which in many applications have replaced die-cast aluminum, stamped steel, and thermoset composites by virtue of lower material and processing costs, improved functionality, and lighter weight. Now a new material, natural fiber, has emerged to compete with glass as the reinforcement for a composite matrix. Natural reinforcing fibers come from several plant species including flax, kenaf, hemp, and jute. The plants have a fibrous "bast" outer layer surrounding a lightweight, porous "shive" or core. The bast fibers, when isolated, have been traditionally used to make ropes or cordage. This new option for long-fiber-thermoplastic (LFT) reinforced composites offers designers an attractive alternative when weighing cost versus performance. Naturalfiber-reinforced composites are not as strong as those with glass fibers, but they cost less. In a multitude of applications they can economically improve performance when conventional unreinforced thermoplastics have reached their limits. In a crude sense, bricks made of mud and straw are natural-fiber composites that can be traced to the dawn of civilization. In a polymer or plastic matrix, natural-fiber composites date to the early 1900s when cotton phenolics were widely used as insulating materials. The most