Synthesis and properties of polyurethane elastomer graded spherulite size

Poly(oxytetramethylene)glycol (PTMG)-4,4'-diphenylmethane diisocyanate (MDI)-based polyurethane elastomer (PUE) was prepared by a mold with a temperature gradient. Effect of the temperature gradient on morphologies and mechanical properties were studied by DSC, polarizing microscopy, tensile test, micro-hardness test, friction test, and DIN abrasion test. The prepared PUE had graded super-structures. Spherulite sizes of the PUE depended significantly on the temperature gradient. Spherulite of PUE in contact with the mold at low temperature was significantly smaller and more dense than that contacting the mold at high temperature. Micro-hardness of the PUE linearly increased from low temperature mold side to the high temperature mold side. Friction coefficient of the surface contact with the low temperature mold prate became more lowered compared to the surface in contact with the high temperature mold plate. Abrasion resistance of the surface in contact with the low temperature mold plate evaluated by DIN abrasion test were better than that at the high temperature mold plate.