Development and characterization of a PU-PMMA transparent interpenetrating polymer networks (t-IPNs)

Abstract

This paper presents our on-going efforts on development and characterization of transparent Interpenetrating Polymer Networks (t-IPNs) with polyurethane (PU) and poly(methyl methacrylate) (PMMA) as constituents. The resulting molecular composite is a fully cross-linked IPN with PU as the tough phase and PMMA as the stiff phase. By varying the volume fraction of the stiff and tough phases, t-IPNs with PMMA/PU content in the range of 90%/10% to 70%/30% have been prepared. Reaction kinetics and process parameters are carefully controlled to avoid phase separation to achieve optical transparency in the resulting IPN. Tensile tests show that a significant failure strain enhancement can be achieved but with a loss of stiffness relative to PMMA. Preliminary fracture tests show that an optimum PMMA/PU ratio in the IPN can produce enhancement in fracture toughness relative to PMMA.