Polymerization of styrene‐isoprene on glass cloth for use in composite manufacture

The evaluation of a new process for promoting the adhesion of thermosetting resins to a reinforcing fiber is described. In this process, termed admicellar polymerization, monomers are polymerized inside a surfactant bilayer adsorbed on a surface. Admicellar polymerization is essentially a surface analogue of emulsion polymerization. This technique can place a variety of polymers at the surface of the reinforcing agent, so that the interfacial layer can be tailored at will. In this study, a styrene‐isoprene copolymer was polymerized on the surface of glass mats. Epoxy‐matrix composites made with untreated cloth, silane‐treated cloth, and admicellar‐treated cloth were evaluated via three‐point bend tests and single filament pull‐out tests. The epoxy‐matrix composites made from admicellar‐treated and silane‐treated cloth gave significantly higher strengths in three‐point bend tests than composites made from untreated cloth. Single filament pull‐out tests, which measure fiber‐matrix adhesion directly, and scanning electron micrographs of the failure interface gave results consistent with three‐point bend tests. This paper indicates that admicellar polymerization deserves further study as an alternative to silane coupling agents in structural composites.