Study of the interaction of carbon fibre surfaces with a monofunctional epoxy resin

Abstract

X-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectrometry (SIMS) have been used to determine the chemical changes observed as a result of interactions between carbon fibre surfaces and epoxy resins. A comparison has been made between untreated, commercially treated and air plasma treated carbon fibres. Both positive and negative static SIMS results indicated the presence of nitrogen and oxygen containing fragments as a result of air plasma treatment, the spectra from commercially treated fibres were dominated by contaminants. Fibres were then sized in the monofunctional epoxy resin, 1,2-epoxy-3-phenoxypropane, and further analysis carried out to determine the chemical nature of the fibre-resin interface. Angle resolved XPS was used to confirm the presence of a layer of resin. Positive ion fragments from static SIMS data have been identified as species which have been formed as a result of the epoxy molecule chemically reacting with species on the fibre surface. Surface energy measurements have also been recorded and it is shown that the polar component of surface energy is greatly increased as a result of surface treatment. This increase is much greater for air plasma treated fibres than for commercially treated fibres. It is proposed that air plasma treatment of carbon fibres increases the interfacial adhesion in carbon fibre/epoxy composites, by the introduction of functional groups which form chemical bonds with the epoxy resin.