Authors
Abstract
The influence of sorption temperatures and rice hull content on diffusion, permeability and solubility of water into PLA has been investigated by theoretical models with the support of experimental data. As expected and experimentally demonstrated water transport rates was higher at higher temperatures. This agrees with the increase in diffusion (D = 0.67 to 3.45?10 -11 m2/s) and permeability (P = 0.33 to 0.55?10 -13 m2/s) obtained by Equation (1). In contrast, the decrease in solubility from S = 5.0?10-3 to S = 0.54?10-3 as temperature was increased from 23?C ?70?C confirms the reduction of PLA’s permeable domains during hydrolysis. Change in molecular weight confirms that hydrolysis was reaction controlled. Furthermore, S, D and P decreased with the increase of rice hull in PLA from 0 to 40 %, contrary to experimental results of Figs. 2 and 3. Rice hull was expected to enhance diffusion and permeability of water into PLA on the fact that being hydrophilic, rice hull do not bond perfectly with PLA leading to more permeable products. This leads to the conclusion that the mathematical relations applied need to be modified to account for other factors such as interface properties, type and form of fillers and chemical reaction of the polymer in order to predict reliably water transport behaviour in filled PLA or similar polymers.
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