Abstract
Automotive coatings, which comprise multiple layers, i.e., primer, base coating, and clear coat layers, are exposed to various environmental conditions that pose various types of damages to them. In particular, the outer layer of the automotive coating, i.e., the clear coat, is affected significantly by such damages. Therefore, a reliable and durable clear coat must be developed to improve the appearance of automobiles. In this study, a new clear coat based on an acrylic-based clear coat modified using polyrotaxane crosslinkers, which are necklace-shaped supramolecules composed of ring-shaped host molecules, is developed and characterized. The effects of polyrotaxane and silane on the scratch properties and mechanisms of the clear coating are analyzed. It is observed that the critical loads of the clear coat from scratch tests can be improved by adding optimal molecular necklace crosslinkers comprising silane functional groups. The improvement in the scratch properties of the modified acrylic-based clear coat may be attributed to the crosslinking characteristics and dynamic molecular movements of the polyrotaxane. In addition, the effects of environmental factors on the scratch characteristics of the modified acrylic-based clear coat are investigated by addressing the scratch durability of the clear coat.
Highlights
Automotive coatings can be regarded as key in preventing various damages, e.g., scuffing, scratching, and chipping, in order to maintain the initial esthetics and afford stable functionality
Threaded onto a linear guest molecule, and a durable and reliable automotive coating composed of silane functional groups, were developed and characterized
The conclusions of this study are as follows: (1) A total of five scratch mechanisms were identified by evaluating the constant load scratch characteristics of commercial automotive multilayer coatings, and a scratch damage mechanism map was constructed by changing the scratch tip size and scratch speed
Summary
Automotive coatings can be regarded as key in preventing various damages, e.g., scuffing, scratching, and chipping, in order to maintain the initial esthetics and afford stable functionality. The coating is a multilayer coating on electrodeposited zinc-plated steel that has undergone phosphoric acid treatment, whose function is to increase adhesion and improve corrosion protection It comprises a primer surface (35–40 mm), a base coating layer (10–15 mm, which is the colored layer), and a clear coat (35–40 mm) [1,2,3]. The polyrotaxane-based hard coating material is expected to exhibit high scratch resistance owing to the formation of a crosslink network and the flexible properties derived from the movable crosslink point. In this study, acrylic-based clear coats modified using a molecular necklace crosslinker were developed; this can simultaneously increase scratch resistance and flexibility owing to the crosslinking characteristics and dynamic molecular motion. Scratch experiments were conducted under high-temperatures and ultraviolet (UV) irradiation conditions, and the scratch characteristics of the developed clear coat were evaluated comparatively
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