Scratch resistance on automotive clearcoats

As original equipment manufacturers (OEMs) strive to deliver improved coating performance with a sustainable footprint, opportunities for innovation are emerging, particularly on improving mechanical properties, appearance, and solids content. Resistance to scratch and mar damage is one of the key performance attributes that has been emphasised by both OEMs and consumers to maintain a vehicle’s appearance and corrosion resistance over its service lifetime. Fundamental methodologies including instrumented scratch measurements at multiple size scales are used in a new work as part of a product development strategy to better understand the scratch and mar behavior of automotive topcoats.

Analysing the coating performance of automotive clearcoats

The study compares physical properties of several melamin-formaldehyde and isocyanate cured clearcoats over the appropriate basecoats. Micro- and nano-scratch techniques were employed in combination with industry standard method, Amtec-Kistler carwash to identify performance differences under different scratch conditions. Mechanical and viscoelastic properties of the coatings were studied using tensile tests and dynamic mechanical thermal analysis (DMTA) to better understand the failure mechanisms associated with plastic deformation and fracture at different scratch scales. The information gathered from the above testing protocols is used to analyse coating performance in terms of the contact strain, transitions between elastic – plastic behavior, coefficient of friction and stress localisation.

The study is published in: Progress in Organic Coatings Volume 125, December 2018, Pages 339-347.