THE EFFECT OF OCTAMETHYL CYCLOTETRASILOXA NE ON THE STRESS-STRAIN BEHAVIOR OF PARTICULATE-FILLED POLYOLEFINS

The effect of introduction of octamethylcyclotetrasiloxane on the stre ss-strain behavior, strength, and the mechanism of plastic flow of par ticulate-filled polyolefins (HDPE, polypropylene) was studied. The add itive increases the ultimate plastic strain of the material. The addit ive shows a dual effect because, first. it modifies the properties of the polymer matrix and, second, reduces the adhesion at the polymer-fi ller interface. When the filler content is below 15 vol %, the increas e in ultimate strain of the modified material may be associated with t he improved stress-strain properties of the polymer matrix. At filler content above 15 vol %, the easier debonding of the filler particles f rom the matrix in modified composites results in that the mechanism of plastic flow changes from the spatially nonuniform pattern, distingui shed by necking, to the macroscopically uniform flow localized in diff use narrow crazelike zones distributed over the sample. This enhances the plastic properties of heavily filled composites.