Tensile Properties of Mixtures of Linear Polyethylene and Random Ethylene Copolymers Having Similar Molecular Weights

MARCELO D. FAILLA; LEO MANDELKERN

MACROMOLECULES

AMER CHEMICAL SOC

Lugar: Washington; Año: 1993 vol. 26 p. 7167 - 7175

0024-9297

The stress-strain curves of mixtures of linear polyethylene and random ethylene-1-alkanecopolymers have been studied. The molecular weights in each series were closely matched so that complicationsdue to polydispersity and chain length differences were avoided. The pertinent variables were the composition,counit content, and crystallization mode. Comparison would be made of mixtures of the same molecularweight, depending on whether on whether or not cocrystallization took place. The characters of the stressstraincurves were found to be different for these two different situations. The small-deformation properties,such as the initial modulus and yield stress, were found to depend only on the total core crystallinity irrespectiveof crystallization mode and composition. On the other hand, ultimate properties such as the draw ratio breakare very dependent on the phase structure of the system. In an important observation, which has otherimplications, it was found that crystallinity levels and ultimate properties were the same in the mixture andpure copolymers when comparison was made at the same nominal branch content.