Interpenetrating polymer networks, the state of the art

Abstract

AbstractInterpenetrating polymer networks are combinations of two crosslinked polymers. Often, they exhibit dual phase continuity, meaning that both phases extend continuously throughout the sample. Recent research on IPNs has shown that both nucleation and spinodal decomposition mechanisms are important in the kinetics of phase separation.If the polymers are almost miscible, a microheterogeneous morphology will develop. Under these conditions, the glass transition of the IPN may be very broad, extending the range between the glass transition of the two homopolymers. Such materials are useful for sound and vibration damping. The loss and storage modulus, and tan δ behavior of polymers and IPNs in the glass transition region were evaluated on a quantitative basis, in order to characterize their damping behavior better. Corrections for background in dynamic mechanical spectroscopy studies will be discussed. The storage modulus of polystyrene at 25°C was selected as a standard. The development of a group contribution analysis of the integral area under the linear loss modulus‐temperature curves, the loss area, LA, is reviewed, and applied to a number of acrylic, styrenic, and vinyl statistical copolymers and IPNs. Each moiety in a polymer is shown to contribute to LA on a simple, additive basis.New research emphasizes the role of morphology and phase continuity in determining LA. The system cross‐poly(vinyl methyl ether)‐inter‐cross‐polystyrene was selected, because its phase diagram in the blend state is well known, and it has become both a model and interesting system to investigate. Midrange IPN compositions exist as two phases at room temperature, as illustrated by dynamic mechanical spectroscopy.