Matt polyurethane coating was successfully prepared through the synergistic effect of castor oil and phenolic epoxy resin into polyurethane backbone. The formation mechanism may be ascribed to the modulus mismatch between the partially modified epoxy polyurethane and partially unmodified polyurethane. Scanning electron microscopy (SEM) was used to observe the micro-rough surface morphologies. Atomic force microscopy (AFM) and three-dimensional (3D) surface profilometer were applied to calculate a series of surface roughness parameters in different dimensions, such as Sa, Sq, Sp, Sv, Sz, Sku, Ssk, etc. The exciting results of this paper—the correlation of surface roughness on measurement length and gloss—are explored in detail. It reveals the extrinsic property of measured roughness with measurement length and provides guidance for what kind of incident angle gloss meters (20°, 60°, and 85°) best describe the gloss of matt polyurethane coating.
Bio-based antismudge coating, as
a substitute for the petroleum-based
one, has excellent liquid repellency and self-cleaning ability, which
is of great value to keep a coated surface free of contaminants. In
this study, we report a facile strategy to fabricate high-performance
biobased hyperbranched polyurethane antismudge coatings. More specifically,
a castor oil-based hyperbranched polyol was employed as a coating
precursor, a hexamethylene diisocyanate trimer was used as the curing
agent, and a mono-hydroxyl-terminated poly(dimethysiloxane) (PDMS-OH)
was introduced as a low-surface-tension lubricant through covalent
bonding. Consequently, a highly transparent smooth coating was obtained
after the coating solution was completely cured. The coating loaded
with 0.5 wt % PDMS-OH exhibited superb liquid repellency and self-cleaning
ability, as attested by liquids such as water, hexadecane, peanut
oil, pump oil, salt solution, strong acid, and strong alkali solutions
that could slide off the coated surfaces cleanly. In addition, even
after 1000 writing and erasing cycles, the coating still retained
its ability to contract ink traces and the contracted ink could be
easily removed with tissue paper. Apart from antigraffiti and antifingerprint
performance, the coating applied on tin plate surfaces showed an adhesion
grade of 5B and a pencil hardness of 3H and displayed superior corrosion
resistance. Furthermore, this mechanically robust coating could withstand
1000 abrasion cycles without sacrificing its ink contraction ability.
Therefore, this biobased antismudge coating should provide an alternative
avenue for developing green and sustainable functional coatings.
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