Pecularities of the thermomechanical behaviour of ultra-high molecular weight linear polyethylene and its blends with linear polyethylene of normal molecular weight

Abstract

Ultra-high molecular weight polyethylene UHMWPE (Mw = 4.106, I s = 0 g~ 10 min), high density polyethylene of normal molecular weight NMWPE (Is = 4.8 g/10 min) and their blends have been investigated by means of thermomechanical loading in constant and impulse regime. It has been established that after melting, NMWPE passes to a viscous-liquid state. After melting at 138 ~ UHMWPE passes to a high-elastic state. The transition of UHMWPE to a viscous-liquid state takes place at temperatures higher than 180 ~ and is accompanied by a high-elastic reversible deformation. The blends of UHMWPE with 10 and 20 mass % of NMWPE show a plateau on the thermomechanical curves, corresponding to a high-elastic state, in a shorter temperature range where the deformation is greater. The blends containing the higher percent of NMWPE show thermomechanical curves lacking such a plateau. MI blends are characterized by a singular thermomechanically defined temperature of melting, which increases with increase of UHMWPE content. The existence of the high-elastic state in the curves of UHMWPE and its blends containing NMWPE less than 30 mass % above their melting temperatures is explained by the high degree of physical crosslinking of UHMWPE.

Blends of normal high density and ultra-high molecular weight polyethylene, ? irradiated at a low dose

“…The enchanced nonisothermal crystallization of the irradiated NMWPE and UHMWPE can be explained by the existence of destructed molecules. This is similar to the case of non-irradiated blends [15], which increase linearly with the increase in concentration of UHMWPE (Fig. Kinetic investigations of melting processes and nonisothermal crystallization of the components in the irradiated blends show that these processes take place at a lower rate compared with those in the non-irradiated blends.…”

“…Kinetic investigations of melting processes and nonisothermal crystallization of the components in the irradiated blends show that these processes take place at a lower rate compared with those in the non-irradiated blends. For the non-irradiated UHMWPE and the blend containing 20 wt % NMWPE there exists a plateau between Tm TM and the temperature of UHMWPE flowing T1TM, which is due to the existence of a physical net of entangled molecules [15] between Tm Tra and T~ TM, which, however, comprises a narrower temperature interval and exhibits a higher value of deformation, compared with the initial crystalline state, than the plateau of the corresponding non-irradiated samples. Within the same interval of concentrations, the enthalpies of melting for the irradiated blends are lower than those of the non-irradiated blends, and the enthalpies of crystallization are almost equal to those of the non-irradiated blends.…”

Efficient synthesis of thermoplastic elastomeric amorphous ultra-high molecular weight atactic polypropylene (UHMWaPP)

“…The elastomeric mechanical properties of UHMWaPP are postulated to be, at least in part, due to physical crosslinking made possible by the ultra-high molecular weights, which limits irreversible deformation by reducing chain mobility. [73][74][75] These data compare favourably with commercial thermoplastic elastomers, such as the olefin block copolymers from Dow (e.g. INFUSE™ 9817), with a density of 877 kg m −3 , a Youngs modulus of 2.31 MPa, an ultimate tensile strength of 7.00 MPa, an elongation at break of 1700%, and a compression set of 15%, 76 or the olefinic thermoplastic elastomers from DuPont (e.g.…”

“…The elastomeric mechanical properties of UHMWaPP are postulated to be, at least in part, due to physical crosslinking made possible by the ultra-high molecular weights, which limits irreversible deformation by reducing chain mobility. 73–75…”

Ultra-drawing of gel films of ultra high molecular weight polyethylene/low molecular weight polymer blends containing BaTiO3 nanoparticles

“…Lowering the degree of chain entanglement and viscosity, a low molecular weight polyethylene (LMWPE) has been used to prepare UHMWPE/LMWPE blends to produce high modulus fibers. 5,[27][28][29][30] The drawability of the UHMWPE gel films may be improved by the incorporation of LMWPE. 28,29,[31][32][33][34] Such fibers and ultradrawn gel films of UHMWPE/LMWPE blends are important in a commercial point of view because the production rate and the drawability of the gel films are not in the level of commercialization.…”