Fabrication of oriented UHMWPE films using low solvent concentration

Abstract

The method of oriented films fabrication from the ultrahigh molecular weight polyethylene (UHMWPE) and small amount of solvent (1.6ml of solvent per 1g of UHMWPE) is described. This method excludes UHMWPE solution because the solvent acts as a plasticity agent. The UHMWPE structure formed due to plasticization favoured to drawability increase. Multi-stage hot orientation method with a draw ratio up to 35 was used to fabricate UHMWPE films. The reactor powders and fabricated films were tested by SEM, DSC and XRD. The degree of crystallinity was increased up to 94% determined by DSC and 93% determined by XRD for films with draw ratio 26 and 35. The achieved tensile strength and modulus was 0.9GPa and 35GPa respectively for films with draw ratio 35. Orientation of the films proceeded via two different mechanisms: (i) macromolecules deployment and their crystallization below draw ratio 26 and (ii) slipping of the fibrils above draw ratio 26. Slipping of the fibrils results in a taut tie molecules amount increase and consequently favour the tensile strength and especially modulus increase.