Improving the adhesion between carbon fibres and an elastomer matrix using an acrylonitrile containing atmospheric plasma treatment

A continuous atmospheric plasma (AP) polymerisation method was developed, using an acrylonitrile precursor, to enhance the adhesion of carbon fibres to an elastomeric resorcinol formaldehyde latex (RFL) matrix. Different processing speeds, corresponding to different residence times in the afterglow zone of the plasma jet, and precursor dosing rates were explored to optimise the treatment. X-ray photoelectron spectroscopy showed that carbon fibres were successfully functionalised in this process. The higher hydrophilicity and better adhesion to RFL was mainly attributed to the introduction of polar amide and hydroxyl groups introduced onto carbon fibre surfaces. Single fibre tensile tests confirmed that AP treatment did not affect the bulk mechanical properties of carbon fibres. The adhesion behaviour between carbon fibres and RFL was characterised by single fibre fragmentation tests. The interfacial shear strength, as measure of practical adhesion, increased by 30% for the fibres exposed longest to the plasma. The plasma-treated carbon fibres were aged in ambient atmosphere for up to three months to determine the effect of storage on the adhesion between the fibres and RFL. After ageing, an 11% reduction of interfacial shear strength was observed.