Synthesis and mechanical properties of cardanol-formaldehyde (CF) resins and CF-poly(methylmethacrylate) semi-interpenetrating polymer networks

Abstract

Cardanol-formaldehyde (CF) resins (both novolac and resol) and CF-poly(methylmethacrylate) (PMMA) semi-interpenetrating polymer networks were synthesized and their mechanical properties and thermal transitions were evaluated. The lower tensile strength of CF resins compared to phenol-formaldehyde (PF) resins may be understood on the basis of the structure of the C15 side chain imparting steric hindrance and reduction in intermolecular interactions. Interpenetration of CF with PMMA increased the mechanical properties only marginally. Scanning electron micrographs of the semi-IPNs showed two distinct phases. Thermomechanical analysis gave two glass transition temperatures,Tg, for the IPNs, the lowerTg corresponding to the PMMA phase and the higherTg to the CF phase. However, the unusual increase inTg of the CF from 128°C to 144°C suggests restrictions in the segmental motion of the CF phase brought about by mixing with another rigid polymer such as PMMA.