| Résumé : |
Flexible automotive coatings are susceptible to scratch and mar damage, especially during finishing and assembly operations. One-component (1K) flexible clearcoats exhibit very good scratch and mar resistance, but unfortunately suffer from poor durability and environmental etch resistance. Two-component clearcoats offer improvements in both etch and durability, but at the expense of scratch and mar. In this paper, the concept and properties of 1K flexibilized silane clearcoats for use on automotive plastics will be introduced and their structure/ property relationships examined as they apply to scratch and mar. The role of coating crosslink density, toughness, glass transition temperature (Tg), and surface profile on the scratch damage of coated plastic substrates will be described. In addition, a new scratch methodology, termed Scratcho, is utilized to determine relative scratch performance and is compared to conventional scratch resistance testing. Results to date indicate that hardness, as affected by the glass transition temperature, and crosslink density, as it contributes to higher essential work values, both affect resultant scratch propensityofthe flexible coatings. The relative ranking of different-coating systems employing alternate crosslinkers (e.g., isocyanate and melamine) is also presented and compared to the newly developed silane crosslinked coatings. |
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Structure/property relationships in flexible alkoxysilane automotive coatings in JOURNAL OF COATINGS TECHNOLOGY (JCT), Vol. 74, N° 933 (10/2002)
