Synthesis and properties of a high solids triethoxysilane-modified alkyd coatings

Abstract

Alkoxysilane modified linseed oil alkyds (TESLOA) were prepared using 3-(triethoxysilyl)propyl isocyanate (TESPIC). TESLOA was formulated as a high solids coating substituting up to 40% of an unmodified long oil linseed oil alkyd in increments of 10%. All the resulting high solids alkyds had a viscosity below 5000 cP. Toxicity and volatile organic compounds (VOCs) were reduced using an iron based primary drier and VOC-exempt acetone, respectively. An increase in adhesion was observed when TESLOA was used in formulations. The chemical resistance, appearance, and flexibility were examined using standard coating tests. An increase in chemical resistance and hardness was observed, while maintaining the flexibility and appearance. The surface energy was measured using contact angle. The TESLOA surface energy exhibited a hydrophobic shift in terms of surface wetting. The additional crosslinking sites of the TESLOA alkyds were evident in a higher glass transition temperature and crosslink density. Tensile properties also exhibited an increase in modulus. Fracture toughness testing showed up to a 50% increase in stress intensity factor at fracture, KIC, and the elastic energy release rate, GIC, when 20 wt.% of TESLOA in the formulation. Corrosion protection was studied using electrochemical impedance spectroscopy (EIS). The EIS data suggested that some self-healing properties could be obtained when using TESLOA as an additive.