Effect of the comonomer content on the mechanical parameters and microhardness values in poly(ethylene-co-1-octadecene) synthesized by a metallocene catalyst

Stress-strain and microhardness measurements were carried out on a series o f copolymers of ethylene and 1-octadecene with different comonomer contents in the corresponding homopolymer of ethylene, synthesized with a metalloce ne catalyst. The different mechanical properties, deduced from the stress-s train curves (Young's modulus, yield stress, deformation at break, and ener gy to break) are interpreted in terms of the crystallinity and molecular we ight of the samples because these two characteristics show considerable var iations with the comonomer content. The microhardness values are explained in terms of these properties, and they are also correlated with Young's mod uli and yield stresses deduced from the stress-strain curves. Linear relati ons are found between microhardness and yield stress and between the logari thm of the microhardness and the logarithm of the elastic modulus. The prop erties deduced from these lines are compared with literature values. (C) 20 00 John Wiley & Sons, Inc.