Fracture Characterization of Low-Density Polyethylenes by the Essential Work of Fracture: Changes Induced by Thermal Treatments and Testing Temperature

J. J. CASELLAS; P. M. FRONTINI,; J. M. CARELLA

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 1999 p. 781 - 796

0021-8995

The tensile deformation and fracture behavior of commercially availablelow-density polyethylene (LDPE) films, having different molecular characteristics, wasstudied. Submitting samples to specific thermal histories controlled the morphologicalstructure of these semicrystalline polymers. Phase-structure analysis of the resultingmaterials was performed by DMA and DSC analyses. The plane-stress essential workof fracture methodology was chosen because the materials used had failed after completenecking of the remaining ligament. Significant differences in behavior, induced bythermal treatments, were found for the tensile yield stress and the specific nonessentialwork of fracture, but not in the specific essential work of fracture. The results show thatthe mechanical properties and fracture behavior depend not only on the crystallinitylevels and molecular weight characteristics of the samples, but also upon the degree ofstructural continuity. The b-relaxation process, associated with the crystal-amorphousinterphase, strongly influences the fracture behavior at testing temperatures chosenbelow the b-relaxation temperature