Morphology maps of blends of a linear polyethylene with ethylene-co-4-methyl pentene-1 copolymers

A Linear polyethylene (LPE) has been blended with each of three ethylene-co -4-methyl pentene-1 (E-4MP1) copolymer fractions of differing branch conten t (2.0, 4.3, and 6.1 mol% 4-methyl pentene-1). These copolymers have Y-shap ed branches, each containing four carbon atoms. The blends were studied usi ng transmission electron microscopy (TEM) and differential scanning calorim etry (DSC) following experimental procedures that have been extensively use d to investigate blends of LPEs with copolymers with alkane (linear) branch es. When the copolymer is lightly branched, LPE/E-4MP1 copolymer blend syst ems give, to a first approximation, morphology maps similar to those found for linear/branched polyethylene systems in which the branched polyethylene has linear alkane branches. Single morphologies are found for high LPE con tents, but there are double morphologies (regions of thick crystals well se parated in a matrix of thin crystals) at low LPE contents after quenching f rom within a restricted temperature range. As the branch density of the cop olymer increases, the same changes in morphology map are seen for the LPE/E -4MP1 copolymer blend systems as for linear/alkane branched copolymer syste ms. The final morphology map, characteristic of a reasonably heavily branch ed copolymer, is reached at a lower branch density (near 6.1 mol%) for the LPE/E-4MP1 copolymer blend systems than for LPE/linear alkane branched copo lymer systems. For LPE/E-4MP1 copolymer blend systems, as for linear/branch ed polyethylene systems in which there are alkane branches, TEM is more sen sitive than DSC detecting changes from single to double morphology.