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The scratch resistance of automotive plastic coatings has been studied extensively over the past few years. Most testing methodology to correlate damage of the coating to field conditions has been in the form of small particulate wearing, e.g., alumina oxide abrasive, or indentation resistance of the coating to an external probe, e.g., a nanoindentation device. The subsequent damage imparted to the coating has generally been analyzed by the amount of coating mass lost in the wear event or through a ratio of optical reflectance of the damaged area to the undamaged surface. In this paper, we attempt to delineate surface damage resistance of several automotive clearcoats through an optical interferometry methodology developed to measure volume and depth of damage incurred with small particle alumina oxide erodents in a simulated wear environment.

The advent of the increased plastic usage in automotive applications has initiated a concurrent upsurge of plastic types. With the estimated usage of 4.2 billion pounds of plastic per automobile by 1999 in the United States and 12 billion pounds of plastic in automotive use worldwide by 2005, the coatings specialist has seen increased demands on coating selection. This paper covers the use of low surface free energy plastics, in particular thermoplastic olefins (TPO) which will account for 20 percent of the plastics utilized in the transportation industry, and discusses the variety of pretreatments used to gain adhesion to TPO. New coatings methods for adhesion “direct” to thermoplastic olefins are briefly described.

Erosion damage to automotive car bodies caused by stones and small sand particles and road debris significantly affects the appearance of paint. Painted engineering plastics as well as precoated sheet steel are affected by erosion phenomenon. Erosion of painted plastic substrates results in cosmetic concerns while that on metal substrates results in cosmetic to perforation corrosion. This work describes a laboratory simulation of erosion of painted plastic substrates by small particles on various paint and substrate types. Gloss loss was used to quantitatively evaluate erosion of painted surfaces. Wear behavior of painted plastic substrates to slag sand impact was evaluated as a function of several variables including paint type (one-component melamine crosslinked (1K) vs. two-component isocyanate crosslinked (2K)), thermal history, and coating modulus. The effect of slag sand type (particle size and chemical composition) was studied.

The recent inclusion of painted plastic fascias/bumpers into automotive applications has necessitated the evaluation of potential in-service damagability. One failure mode that has been identified, that of friction-induced paint/substrate damage, has been simulated in a laboratory environment. Our goal was to evaluate the effects of coating attributes, both thermal and mechanical, on subsequent performance of painted thermoplastic olefin (TPO) materials. It was determined that the most significant parameters in the paint which contributed to damage were the glass transition temperature, the secant modulus at break, and the static coefficient of friction. This paper will discuss techniques and results used to reach these findings.

Within the past several years, the automotive industry has depended more upon plastics in the design of automobiles than ever before. With the introduction of plastics, both flexible and rigid, has come a new demand on paint. Current technology employs a “flexible” coating for use on flexible plastics, and a “rigid” coating for use on rigid plastics and steel. However, employing two types of paint, “rigid” and “flexible”, increases the potential for problems associated with color match, weatherability, etc. This paper will discuss recent developments in automotive coatings, with emphasis on the requirements and uses of “universal” coatings - those that can be applied over both rigid and flexible substrates.

Damage to painted automotive plastics induced by Hertzian contact stresses continues to plague the material engineer involved in the design and selection of fascias, bumpers, body-side moldings, and the like. Studies conducted to determine the root cause of such failures have focused on the effects of paint and the role of friction in the compressive, tensile and shear failure of painted thermoplastic olefins (TPOs). The study described herein probes the effects of paint type on the compressive, tensile and shear damage resistance of painted TPO substrates. Coating variations, e.g., adhesion promoter and topcoat type, and their effect on damage type and damage sensitivity will be described. The apparatus utilized to impart the damage, SLIDO, and the variables studied affecting the damage, e.g., acceleration, velocity, temperature, and loading pressure, are also discussed.

This paper describes the applicability of optical imaging techniques to the analysis of the scratch resistance of automotive interior plastic materials. The evaluation of so-called “finger testing” has traditionally relied upon human vision for detection of the initial scratch position. Commonly performed under uniform and defined illumination conditions, the relative contrast difference signified by whitening on a surface as determined by unaided human vision is a highly variable subjective perception; thus individual inspectors may determine the “whitening” point differently. This paper compares test data obtained from both visual and instrumental evaluation methods and discusses the advantages of optical imaging techniques for surface defect analysis.