Effect of processing conditions on dimensions of sisal fibers in thermoplastic biodegradable composites

Biodegradable composites based on treated and untreated sisal fiber and mat er Bi-Z were processed using an internal batch mixer. The effect of process ing conditions (temperature, speed of rotation, and time of mixing) and alk aline treatment on the dimensions of sisal fiber was studied. The length an d diameter of the initial fibers were reduced during mixing and this effect was correlated to the magnitude of the shear stress developed in the mixer . An increase of the speed of rotation and/or a reduction of temperature pr oduced fibers of smaller dimensions but with a higher aspect ratio l/d. Alk aline treatment increased the kinetics associated to the reduction of the f iber's dimensions. A semiempirical model was employed to predict the size o f the fibers versus the time of mixing. (C) 2000 John Wiley & Sons, Inc.