Modifications of kenaf fibers with <i>N</i>‐methylol acrylamide for production of kenaf‐unsaturated polyester composites

Abstract

Abstract Kenaf fiber mats were modified with N ‐methylol acrylamide (NMA) solution with either sulfuric acid or p ‐toluenesulfonic acid (TsOH) as a catalyst. The (unmodified‐kenaf)‐UPE composites and (NMA‐modified‐kenaf)‐UPE composites were obtained by a compression molding process. Orthogonal experiments were used for determination of optimum modification variables for maximizing the flexural strength of the resulting (NMA‐modified‐kenaf)‐UPE composites. Three variables with three levels (NMA usage: 1, 3, and 5 wt %; usage of acid catalyst: 0.1, 0.2, and 0.3 wt %; and oven‐dry temperature for NMA‐treated kenaf fiber mats: 80, 103, and 125°C) for each variable were used in the orthogonal experiments. Modifications of kenaf fibers with TsOH as a catalyst significantly increased the flexural strength. Modifications of kenaf fibers with either sulfuric acid or TsOH as a catalyst significantly enhanced the flexural modulus and significantly reduced the water‐uptake rate of the resulting kenaf‐UPE composites. The improved interfacial adhesion between kenaf fibers and UPE resin was confirmed by characterization of NMA‐modified fibers with Fourier transform infrared spectroscopy, as well as scanning electron microscopy images. The mechanisms for the improved strengths and water‐resistance by the NMA modifications of the kenaf fibers were discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012