Fundamentals and characterizations of scratch resistance on automotive clearcoats

• Published in: Progress in organic coatings Vol. 125; pp. 339 - 347
• Main Authors: Feng, Linqian, Benhamida, Beatrice (Nadia), Lu, Chen-Yuan, Sung, Li Piin, Morel, Pierre, Detwiler, Andrew T., Skelly, Jon M., Baker, Leslie T., Bhattacharya, Deepanjan
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 01-12-2018; Elsevier BV
• Subjects: Automobile industry; Automotive clearcoats; Automotive engineering; Balances (scales); Coefficient of friction; Contact stresses; Corrosion resistance; Deformation mechanisms; Elasto-plastic behavior; Failure analysis; Failure mechanisms; Industry standards; Innovations; Isocyanates; Mechanical properties; Nano-scratch; Physical properties; Plastic deformation; Product development; Protective coatings; Scaling behavior; Scratch resistance; Service life; Strain; Tensile tests; Test procedures; Thermal analysis; Viscoelasticity; Viscoelasticity; Automotive clearcoats; Nano-scratch; Elasto-plastic behavior; Scaling behavior; Scratch resistance
• DOI: 10.1016/j.porgcoat.2018.09.011
• EISSN: 1873-331X
• ISSN: 0300-9440

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•Disclosed the advances in the method development on multi-scale instrumented scratch tests from light to severe scratches.•Delivered understanding on scaling behaviors of scratch responses and root-causes.•Connected mechanical/viscoelastic properties with scratch behaviors.•Established correlation between the industrial test method (Amtec-Kistler carwash) vs. nano-scratch test.
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 emphasized 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 this work as part of a product development strategy to better understand the scratch and mar behavior of automotive topcoats. This 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 analyze coating performance in terms of the contact strain, transitions between elastic – plastic behavior, coefficient of friction and stress localization.