Background
Varnish is used in many domains to enhance wear resistance, mechanical behaviour or chemical resistance. To characterize varnish cohesion or adhesion on plane surface, a scratch-test is predominantly used. In order to investigate coating properties on fibres, the common method uses tensile tests.
Objective
The aim of this paper was to investigate the adhesion of varnish on a monofibre of polyamide using an out of the box procedure based on scratch tests. To do so, a specific device was conceived to enable a scratch test on a single fibre.
Methods
Adhesion between varnish and a monofibre of nylon was investigated using several series of scratch tests on fibres coated by two types of varnish. Coating toughness and adhesion were investigated according to the coating composition and thermal treatment. A comparison between the different prints was discussed to characterize the effect of varnish type on the scratch resistance and to determine the parameters that influence this adhesion using scratch-test.
Results
The obtained results highlighted the influence of the thermal treatment imposed to the fibres on the mechanical behaviour. Tensile tests were conducted on the three types of samples in order to establish a link in terms of classification between a well-known characterization experiment and the presented scratch test.
Conclusion
Beyond the investigation of varnish/nylon fibre adhesion, this paper mostly aims at validating an innovative process for the characterization of coatings deposited on curved surfaces like fibres.