Coir ( Cocos nucifera ), a ligno-cellulosic fiber, is cheap and abundant in the coastal regions of tropical countries. In this paper the effect of physical and chemical treatments on the mechanical properties of coir fibers is reported. Changes in moisture regain, crystallite orientation, and percentage crystallinity were observed when fibers were treated with hydrochloric acid (10%), sodium hydroxide (10%), and acetic acid (10%). Scanning electron micrographs of the fractured surfaces of the fibers showed extensive fibrillation. Tenacity and elongation-at-break decreased with chemical treatment and UV irradiation. An increase in initial modulus and crystallinity was observed with alkali treatment.

SynopsisCrosslinking of 4,4'(bismaleimido)diphenyl ether (BM) was investigated in presence of bis(maminophenyl) methylphosphine oxide (BAP), tris(m-aminopheny1)phosphine oxide (TAP), diaminodiphenyl ether (E) and 3,3-bis(p-aminophenyl)phthalide (AP). These crosslinked resins were examined for thermal stability by thermogravimetric analysis. A slight decrease in initial decomposition temperature, the temperature of maximum rate of weight loss, was observed, though the char yield in nitrogen atmosphere a t 8OOOC did not change appreciably. Glass-cloth-reinforced laminates were fabricated from BM and amine mixtures. An improvement in mechanical properties was observed in the presence of phosphorus-containing di-and triamines.

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This article describes the synthesis of N,N′‐bis(3,3′‐maleimidophenyl) sulfone (S) and its Michael addition products with (4,4′‐diaminodiphenyl) methane (S‐M), 4,4′‐diaminodiphenyl ether (S‐E), (3,3′‐diaminodiphenyl) sulfone (S‐DDSm), (4,4′‐diaminodiphenyl) sulfone (S‐DDSp), (3,3′,3″‐tris aminophenyl) phosphine oxide (S‐TAP), and 9,9‐bis(p‐aminophenyl) fluorene (S‐B). Curing behavior of these bisimides was investigated by differential scanning calorimetry. Activation energy of curing reaction was determined by using isothermal and multiple heating rate method. Thermal stability of bisimides was evaluated by thermogravimetric analysis. Better char yields were obtained in S‐TAP resins.

Hybrid laminates consisting of glass fiber mat, chopped bristle coir fibers and un saturated polyester resin matrix were fabricated. Effect of treatment of coir fibers with alkali and dichloro methyl vinyl silane on the mechanical properties of the laminates was investigated. The hybrid composites having 66% resin (w/w) and 19.7% chopped coir fiber (1cm long) showed 35% improvement in flexural strength and 70% in flexural modulus over the neat polyester resin sheets. Mechanical properties of laminates increased on increasing the coir fiber length up to 1 cm beyond which a decrease in strength was observed. Hybrid laminates fabricated from NaOH treated coir fibers had better mechanical properties than those fabricated from untreated coir fibers. A decrease in thermal conductivity was observed with increasing weight fraction of coir fibers.