Characteristics and Water Absorption Behavior of

Curing Characteristics and Water Absorption Behavior of Glucose Based... 

Curing Characteristics and Water Absorption Behavior of Glucose Based Polymers 9 3.1.2 FTIR Spectra of Epoxy Resin and GMAEVC Cnring... 

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. 

Dielectric Behavior of Adsorbed Water. Determination of the dielectric absorption of adsorbed water can yield conclusions similar to those from proton NMR studies and there is a considerable, although older literature on the subject. Figure XVI-7 illustrates how the dielectric constant for adsorbed water varies with the frequency used as well as with the degree of surface coverage. A characteristic relaxation time r can be estimated... 

In case (a), an equilibrium is reached. It can be considered here that there are only reversible physical interactions between the polymer and water. Drying leads to a curve that is practically a mirror image of the absorption curve. The behavior of the material can be characterized by two quantities the equilibrium water concentration W, which characterizes the polymer affinity for water (hydrophilicity), and the duration Id of the transient, which is sharply linked to the sample thickness L and to a parameter characteristic of the rate of transport of water molecules in the polymer - the diffusion coefficient D. 

This crystalline aromatic nylon, combines the high strength and stiffness of nylon with the thermal stability of polyphenylene sulfide. Molding characteristics are similar to nylon 6/6, with similar or better chemical resistance, but its 24 h water absorption is only 0.2 versus 0.7% for nylon 6/6. A key behavior is high heat resistance. 

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