Damping Characteristics of Polyurethane-Based Simultaneous Interpenetrating Polymer Networks

Abstract

A brief overview of damping with polymers is given. The highest energy absorbing potential of polymers is centred around their glass transition temperature ( T g). In order to broaden the transition, partially miscible polymer pairs with fairly widely separated T gs can be used to give broad and high transition regions. This can be obtained by the use of interpenetrating polymer network (IPN) technology. The damping ability of the IPNs was assessed from the tan δ and loss modulus versus temperature curves. The area under the linear tan δ curve (TA) and the loss modulus equivalent (LA) were calculated and correlated with the IPN composition. An incompatible polyurethane/polystyrene IPN was chemically modified by internetwork grafting and the use of compatibilizers, resulting in a high and broad transition with tan δ values > 0.3 over 80°C and 135°C respectively. Conducting a stirred polymerization of a 60:40 PUR/PS IPN resulted in a very complicated morphology with phases within phases within phases, Values for tan δ were greater than 0.3 from −19°C to 145°C combined with a high TA area of 85.4 K. The influence of the composition on the damping ability was studied in a semicompatible polyurethane/polyethyl methacrylate IPN. At the 70:30 composition, a broad temperature range (> 130°C) of tan δ values greater than 0.3 and a high TA area of 62.1 K resulted. LA was found to increase with increasing PEMA content, but with values well below those expected from applying the linear rule of mixing to LA of the homonetworks. TEM micrographs further elucidated the multiphase morphologies.