Properties and modification methods for vegetable fibers for natural fiber composites

TLDR

Natural vegetable fibers provide good mechanical strength but suffer from high moisture absorption, poor wettability, and weak adhesion to polymer matrices, causing debonding over time. The study aims to develop composites with high mechanical properties by surface‑modifying the fibers. The authors discuss physical and chemical modification techniques such as plasma treatment and graft copolymerization to improve NVF–polymer composite properties. Coupling agents such as silanes or stearic acid raise Young's modulus and tensile strength by up to 50% and reduce moisture absorption by about 60%, with other surface treatments producing comparable gains, though the interaction mechanisms vary by system. © 1996 John Wiley & Sons, Inc.

Abstract

Studies on structure and properties of natural vegetable fibers (NVF) show that composites made of NVF combine good mechanical properties with a low specific mass. The high level of moisture absorption by the fiber, its poor wettability, as well as the insufficient adhesion between untreated fibers and the polymer matrix lead to debonding with age. To build composites with high mechanical properties, therefore, a surface modification of the fibers is necessary. The existing physical and chemical NVF modification methods—e.g., plasma treatment or graft copolymerization—which are used for the development of NVF–polymer composite properties is discussed. It is shown that modified cellulose fiber–polymer interaction mechanisms are complex and specific to every definite system. By using an coupling agent, like silanes or stearin acid, the Young's modulus and the tensile strength increases, dependent on the resin, until 50%. Simultaneously, the moisture absorption of the composites decreases for about 60%. With other surface modifications, similar results are obtained. © 1996 John Wiley & Sons, Inc.