Effect of a two step fiber treatment on the flexural mechanical properties of sisal-polyester composites

Sisal fibers were chemically treated with a two-step treatment (first sodium sulfide aqueous solution and then acetic anhydride/acetic acid mixture) to promote better adhesion to a polyester resin matrix. The flexural behaviour of the composites was analyzed as a function of the time of immersion in distilled water, and there was an improvement for short times of immersion. The long term behaviour of the treated composites was, however, no better than that of the untreated ones. This could be because of the controlling role of plasticization of both the fibers and the resin matrix for the longer times of immersion.