Novel high‐solids pigmented coatings prepared from a new‐synthesized isophthalate‐based oligoester, a melamine resin, and various fillers

Abstract

ABSTRACT:A new-synthesized hydroxyl-terminated isophthalate-based liquid oligoester (L-311), an hexakis(methoxymethylol)melamine resin, and various inert pigments (fillers) such as either kaolins (Al 2 O 3 ⅐ 2SiO 2 ⅐ 2H 2 O) of different particle sizes (1.50 and 4.80 m) or calcium metalsilicate (CaSiO 3 ) were used to prepare high-solids pigmented coatings (PA and PW series, respectively). The physical, chemical, and mechanical properties (pencil hardness, Knoop hardness, flexibility, impact resistance, adhesion, gloss, solvent, and mar resistance) of the new-formulated pigmented coatings were correlated to the chemical species of the filler, the filler's load and particle size, the quantity of the crosslinker, and the introduction of large particle size colloidal silica into the coating. For measuring the mar resistance of the pigmented coatings, the Taber abrasion method was applied and the inverse wear index, F [ϭI Ϫ1, cycles/cg (wear index l, weight loss (cg) per number of cycles)], was directly related to the mar resistance. Either when kaolins or calcium metalsilicates were used as fillers, the Knoop hardness, the impact, and mar resistance of the films were affected from the filler's load, whereas the quantity of melamine resin (crosslinker) affected the knoop hardness, the gloss, and the mar resistance. The fillers' particle size and the introduction of large particle colloidal silica affected mainly the mar resistance and the gloss, respectively. The pencil hardness of the PW-pigmented coatings series (F-2H) was higher than that of the PA-series (B-HB). The chemical composition of the inert pigment proved to be a very important parameter in the preparation of pigmented coatings with specific properties that aim to meet modern and particular demands for various end-up uses. All the new-formulated high-solids (nonvolatiles by weight ϳ 70%) pigmented coatings (PA and PW series) presented excellent adhesion (5B), flexibility (Ͼ 32%), methyl ethyl ketone (MEK) resistance (Ͼ200 rubs), high pencil hardness, good knoop hardness, and very good impact resistance (from 100 up to 160 in.-lb), independently of the species of the filler (kaolins or calcium metalsilicate).