Thermodynamic properties of extended chain polymethylene single crystals.

摘要: Density, morphology, and melting data on linear polyethylene high molecular weight polymethylene crystallized from the melt under elevated pressure are presented. For approximately constant supercooling a sharp density increase is noted above 2300 atm. crystallization pressure. Above 4000 densities 0.99 achieved. The has larger lamellar thickness than polyethylene, but does not reach full chain extension. of extremely with no evidence premelting up to at least 136°C. Equilibrium maximum points 138.7 141.4°C. have been measured for 105 weight-average 107 weight.