Effect of Initial Crystallinity on the Response of High-Density Polyethylene to High-Energy Radiation

MARCELO D. FAILLA; ENRIQUE M. VALLÉS; B.J. LYONS

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 1999 vol. 71 p. 1375 - 1384

0021-8995

Samples of each of two high-density polyethylenes with various initialdegrees of crystallinity, but otherwise identical, were exposed under a vacuum tomoderate doses of gamma irradiation. The results indicate that, for otherwise initiallyidentical polymer samples, the dose required to reach the gel point increases withincrease of the initial degree of crystallinity. Above the critical dose for gelation, the gelcontent decreases with higher degrees of crystallinity at equal radiation doses. Themechanical behavior of the polymers changed progressively from ductile to brittle asthe crystallinity was increased. The extensibility of originally ductile samples decreaseswith increasing radiation dose. The irradiation of samples having intermediate behaviorproduces a change to ductile behavior. Mechanical behavior is not modified substantiallywhen brittle samples are irradiated. The initial modulus is little altered byirradiation, while the yield stress shows a slight increase with irradiation. The mechanicalproperties, such as draw ratio at break and ultimate tensile stress, decreasewith dose in ductile samples