Polyurethane-polystyrene sequential interpenetrating polymer networKs have been synthesized from castor oil, diphenylmethane diisocyanate, styrene, ethylene glycol dimethacrylate as a crosslinker and benzoyl peroxide as an activator. The interpenetrating polymer networks were obtained as tough and transparent films by a transfer moulding technique. These IPNs were characterized by mechanical properties, viz. tensile strength, Young's modulus, elongation at break and Shore A hardness, and crosslink density. The morphological behaviour was studied by dynamic mechanical analysis and scanning electron microscopy. 65 85 75 65 85 75 65 100 a Content of polyurethane > 35 w t K does not afford film formation as the islands of PU and polystyrene are formed during IPN synthesis. POLYMER INTERNATIONALVOL. 26, NO. 3,1991
A series of two-component polyurethane/poly(methyl acrylate) sequential, interpenetrating polymer networks (IPNs) containing different amounts of polyurethane were prepared. The NCO-to-OH ratio used in the preparation of the first-formed polyurethane network' was varied in order to change the cross-link density in the matrix of these IPNs. The morphology of these IPNs was investigated using electron microscopy, dynamic mechanical analysis and equilibrium compression studies. It was concluded that as the NCO-to-OH ratio increased, the cross-link density increased and thereby the extent of mixing increased.
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