Preparation Of Phenolic Foam And Reinforcement Of Phenolic Foam With Fibers

Phenolic foam performs not only outstanding insulation like polyurethane foams but also unique flame resistance, heat-resistant quality, low smoke and low toxic compared with other organic thermal insulation materials. Therefore, phenolic foam receives widespread attention. However, phenolic foam has flaws:different preparation, low compress property, low bending property, and brittleness, which extremely limited its application.In this study, the influences of formulation and process on the properties of phenolic foam were researched and concluded the optimal formula and process. Moreover, the properties of phenolic foam were reinforced by stiff fibers-glass fibers (GF) or/and flexible fibers-aramid fibers (AF) innovatively, and analyzed the influences of type, content, and length of fibers on the mechanical properties of phenolic foam. The mechanisms of reinforcement were also discussed. The main conclusions are below:(1) The types of curing agents, the amount of curing agents and foaming agents, and the foaming temperature are the main influences on the properties of phenolic foams in the process of preparation of phenolic foams. Only the mixed curing but single curing agent can prepare good phenolic foams.(2) The addition of stiff GF can make phenolic foam stiffer without sacrificing the flame retardation, but do little to the brittleness. The optimal content of GF is6wt.%, the optimal length of GF is3mm.(3) The addition of flexible AF can make phenolic foam tougher without sacrificing the flame retardation, but do little to the strength. The optimal content of AF is6wt.%.(4) Hybrid fibers can impart phenolic foam significant integrated mechanical properties without lowering the flame retardation. The addition of hybrid fibers can make phenolic foam stiffer and tougher. The optimal hybrid ratio is1:1of GF toAF.(5) The mechanism of fibers reinforcing phenolic foams is that stiff fibers perform pillaring effect, deviating the crack, pulling out effect in phenolic foam, which can improve the compress strength and bending strength of phenolic foam; flexible fibers perform bridging effect, pulling out and rupturing effect, which can increase the bending strength and impact strength of phenolic foam; and hybrid fibers act net structure in phenolic foam, which can reduce the brittleness of phenolic foam.