Quantitative evaluation of scratch visibility resistance of polymers

Susceptibility of polymer surfaces to acute visibility upon scratching has presented a serious challenge to the polymer industry for quite some time. The ability to design polymers with good scratch visibility resistance requires extensive knowledge about scratch deformation mechanisms and their propensity for light scattering. After examining the physical nature of human vision and surface optical characteristics, a new methodology is developed to quantitatively determine the onset of scratch visibility of polymers via an inexpensive desktop scanner. Taking into account the sample background color, texture, gloss and feature size, the proposed methodology can consistently and reliably determine polymer scratch visibility resistance regardless of the sample surface characteristics. Good correlation is found between this method and actual human perception. Quantitative analysis of the scratched surface is carried out with scanning laser profiling confocal microscopy and strong correlations among scratch visibility, observation angle and various scratch damage features such as roughness and scratch grooves are established. The proposed approach will greatly assist the development of scratch-resistant polymeric materials where surface aesthetics is of primary concern.