Tough,void-free,flame retardant phenolic matrix materials

Polymer matrix composites may be effective alternatives to steel and concrete in many civil structures due to their anticipated superior environmental stability. However, one major obstacle limiting the use of organic materials in construction is their high combustibility. Phenolic resins are high volume materials widely utilized for many purposes, including structural adhesives, composites, coatings, etc. They are also well known to provide fire resistance in many applications. Normally, their curing process involves reagents which produce volatile by-products such as water, formaldehyde, or ammonia. This feature has severely limited processability and their utilization in void-free structural applications. This paper is focused on a catalyzed epoxy-phenolic reaction utilizing commercially available phenolic resins and liquid epoxies to promote a predominately (50–90% w/w) phenolic network which produces little or no volatiles. Both ductility and flame resistance are enhanced in compositions containing these high phenolic concentrations. The materials appear to have significant potential for adhesives and structural composites, wherein the absence of voids could permit significant new products to be prepared for infrastructure and other applications. Relationships between the chemical and network structures of these materials and their properties are described.