Scratch Properties of Clear Coat for Automotive Coating Comprising Molecular Necklace Crosslinkers with Silane Functional Groups for Various Environmental Factors

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.

Environmental release from automotive coatings are similar for different (nano)forms of pigments

(Nano)form release analysis of artificial aged automotive coating supports to group the environmental release lifecycle of nanomaterials by intended use and product matrix.

Preparation and properties of self-healing polyether amines based on Diels–Alder reversible covalent bonds

Over time, automotive coating is bound to be damaged; therefore, it is necessary to give the coating a self-healing ability to make its performance even better. First, furfuryl glycidyl ether (FGE) was synthesized by epichlorohydrin and furfuryl alcohol. Then, furanyl-terminated resin FGE-T5000 was synthesized by polyether amine T5000 and FGE. Finally, 4,4′-diphenylmethane bismaleimide (BDM) was added to FGE-T5000 as a cross-linking agent to form a resin named FGE-T5000-BDM which has Diels–Alder (DA) bonds. The products were characterized by Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, differential scanning calorimeter, dynamic mechanical analysis, thermogravimetric analysis, optical microscope, tensile tests, and other tests. The results showed that FGE-T5000-BDM demonstrated thermally reversible self-healing property from 50°C to 150°C, and that the best temperature of the DA reaction was 80°C. The gel content of FGE-T5000-BDM was 98%. Also, the glass transition temperature and the initial temperature of the Retro-DA (r-DA) reaction were −58°C and 88°C, respectively. Moreover, the self-healing efficiency of FGE-T5000-BDM was up to 88% after staying at 80°C for 12 h. The innovation shown in this article was that the reversible covalent bonds (DA) were combined with the polyether amines, which produced the characteristics of self-healing. Its unique self-healing properties are useful in some areas, such as automobile coatings and other materials.

Effects of nano-layered silicates on mechanical and chemical properties of acrylic-melamine automotive clear coat

Purpose Mechanical and chemical properties of acrylic-melamine automotive clear coat in the presence of different percentages of well dispersed nano-layered sodium montmorillonite (Na-MMT) silicate particles were investigated. For this purpose, prepared dry clear coat film samples were subjected to the entire standard test series, usually carried out in automotive coating industry. Design/methodology/approach Effects of adding different percentages of nano-layered silicate on mechanical and chemical properties of acrylic-melamine automotive clear coat were investigated. To increase the compatibility of nanoclays with polymer matrix of clear coat, the surface of nanoclays was modified by benzalkonium chloride as a cationic surfactant. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used for characterization and comparison between clays before and after modification, and also after dispersion in coating. Prepared dry clear coat film samples subjected to the test series are usually carried out in automotive coating industry. Findings The results indicated that incorporation of 1 and 2 Wt.% of nano-layered silicate caused desired improvement in chemical and physical properties of the acrylic-melamine clear coat. Increasing the percentage of nanoclay to over 2 Wt.% caused damage in some properties such as hardness, cupping and gloss. Research limitations/implications All materials and methods were used in this research are industrial grade. Therefore, the introduced modified clear coat sample has potential for commercial production as an automotive clear coat. Originality/value As far as it was searched in the literature, effects of adding nanoclay particles on mechanical and physical properties of different clear coats, such as epoxy clear coat, have been investigated in a few researches, but in this research, common and special tests which are necessary in automotive coating industry have been ignored. In the present study for the first time, acrylic-melamine clear coat was subjected to modification using nano-clay, and also, the most common industrial test methods were used for investigation of mechanical and chemical properties.