DUCTILE-BRITTLE TRANSITION BEHAVIOR OF SHORT-CHAIN BRANCHED POLYETHYLENES AT 80-DEGREES-C

A systematic study on the ductile-brittle transition of short-chain br anched polyethylenes (SBPEs) is reported. The values of threshold stre ss intensity, the time corresponding to the point of ductile-brittle t ransition and the failure time (t(f) of samples which failed in ductil e and brittle regions were found to increase significantly with increa sing branch length of the SBPEs. The fracture kinetics and the morphol ogy at the notched root were distinguished for SBPE samples that faile d in ductile and brittle regions. The values of (CC(notch opening disp lacement at the root of notch) - BB(the thickness of the craze))/(AA(n otch opening displacement at the surface of the specimen) - CC) are le ss than or equal to about 0.3 for all samples which failed in the brit tle region, and these values are only about 20-30% of those of the sam ples which failed in the ductile region. Finally, an equation was deve loped to predict t(f) of SBPEs which failed in the ductile and brittle region in terms of stress intensity, branch length and other material and experimental parameters.