Evaluation of Physico-Chemical Properties

5 Evaluation of Physico-Chemical Properties 13.3.5.1 Water Absorption 

A water absorption study was carried out by immersing neat UPE and composite specimens of dimensions 10 mm x 10 mm x 2 mm in distilled water for two months at 35°G. The samples were dried completely in a hot air oven before performing the water absorbance study and then initial weight was recorded. For water absorption measurements. 

Where W, W. and are percentage weight gain, initial weight and final weight, 

Water absorption results of neat UPE and its composites reinforced with raw, mercerized and benzoylated fibers have been shown in Table 13.1. It can be seen from the table that water absorption characteristics of polymer composites depend upon the content of fiber loadings, water immersion time and surface modification techniques. The water absorption of raw and surface-modified fiber-reinforced UPE composites has been found to increase with the increase in percent loading. Similar results were also reported by Rashdi et ah during their studies on the water absorption behavior of kenaf fibers-reinforced polyester composites [27]. This may be due to greater affinity of water for OH groups present on the fiber backbone, whose number increases with the increase in fiber contents. In comparison to raw filler, composites reinforced with surface-modified filler exhibited low water absorption, which may be due to the reduction in the hydrophilic character of cellulosic biofibers after surface modification. 

Between mercerized and benzoylated fibers-reinforced UPE composites, benzoyl chloride grafted fibers-reinforced UPE matrix has been found to have better water resistant behavior, which may be due to better compatibility of benzoylated fibers and hydrophobic matrix. 

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