Flexible ceramic-reinforced polyurethane composite coatings on synthetic fibres: Process of continuous liquid film coating and its influence on the coating thickness

A concept for the realisation of composite layers on the surface of synthetic fibres by continuous liquid film coating of spread roving or monofilaments with a slurry containing ceramic particles and a polymeric binder is successfully demonstrated. Polyamide 6 monofilaments were coated with alumina particles and a polyurethane elastomer based binder system to achieve higher abrasion resistance. Under frictional load, the coating is abraded in small units consisting of some particles and the surrounding polyurethane matrix, which predetermines it to be used as sacrificial layer. The slurries showed shear thinning behaviour. Increasing the content of the rheological agent (carboxymethylcellulose [CMC]) led to an exponential increase of the viscosity, which therefore can be tailored by varying the CMC content. An increase of fibre radius, slurry viscosity or withdrawal speed led to an increase of the coating thickness, which is in accordance to published results of Newtonian or non-Newtonian coating fluids.