PHYSICAL-PROPERTIES AND ELASTICITY BEHAVIOR OF AMORPHOUS POLYURETHANENETWORKS

A series of amorphous polyurethane networks have been prepared by reac ting MDI (4,4'-diphenylmethane diisocyanate) with mixtures of a poly(o xyethylene) end -capped poly(oxypropylene) triol and a poly(oxyethylen e) end-capped poly(oxypropylene) diol. The effects of crosslinking den sity on the physical properties and elasticity behavior of the polyure thane networks have been investigated by differential scanning calorim etry, DSC, tensile properties, single-edge notch, SEN, tear strength. The DSC results show that the glass transition temperature of the poly urethane networks increases slightly with increasing polyether diol co ntent indicating that effect of urethane bond concentration outweighs that of crosslinking density. Composition affects the physical propert ies significantly. As the polyether diol content increases (the crossl inking density decreases), the tensile strength, elongation at break, tensile toughness and tear strength increase, but the initial modulus decreases. The tensile stress-strain data have been analyzed by the Mo oney-Rivlin equation. As the polyether diol content increases, the cro sslinking density decreases, and 2C(1), the modulus at very large defo rmation, and (2C(1) + 2C(2)), the modulus at very small deformation, d ecreases, as expected. As the polyether diol content increases, the po lyurethane networks approach more to the phantom behavior.