Micro- and nano-structured IPNs based on thermosetting resins

Abstract

Different components of interpenetrating polymer networks (IPNs) have different influence on their properties and their behavior in various applications, such as automotive dual curing applications. Dual curing systems, upon hardening, can give interpenetrating polymer networks (IPNs). UV–thermal dual‐cure process that was used to obtain IPNs consisted of an UV curable acrylic component and a classic 2‐pack urethane component. Novel acrylate‐terminated hyperbranched polyester with high functionality HBP(A) was used as part of the acrylic component, which was cured by UV radiation. The urethane part of the IPNs was classical 2‐pack polyurethane and it was crosslinked by heating.The aim was to explore the influence of thermosetting resin HBP(A) on IPN properties. First, the weight ratio of HBP(A) and a reactive diluent 2‐ethyl hexyl acrylate (EHA) in the IPNs was varied from 100/0 to 25/75, while the urethane component remained the same in all the IPN samples. Then, the IPN with 50/50 weight ratio in acrylic component was used to investigate the influence of the reactive diluent in IPNs on their behavior, but also to see more clearly the role of the HBP(A) component. All the IPNs were also compared to a classical 2‐pack polyurethane clear coat consisted of a hydroxyl functional acrylate copolymer (HA) and Desmodur®N3390.The IPNs were characterized by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The mechanical properties of the IPNs were also investigated.DMA showed that with increasing HBP(A) in the IPNs, the crosslink density increased, while the flexibility decreased. The data obtained by DMA and DSC showed a decrease of the Tg values with increasing amount of HBP(A). There were slight differences in the thermal stability of the IPNs.