基材润湿 化学品

Substrate wetting agents reduce the dynamic surface tension of the liquid coating to match or fall below the critical surface energy of the substrate, enabling complete wet-out. Dispersing wetting agents (like polymeric dispersants) wet the pigment surface during the dispersion process. Both mechanisms involve surface tension reduction, but they target different interfaces — substrate surface vs. pigment surface.

Low-energy substrates present the greatest challenge: polyolefins (PP, PE) at 29–31 mN/m, PTFE at 18 mN/m, and silicone-contaminated surfaces. Standard waterborne coatings have surface tensions of 45–60 mN/m — far above the substrate critical surface energy — without additives. Silicone wetting agents (polydimethylsiloxane derivatives) reduce coating surface tension to 20–25 mN/m; fluorinated wetting agents achieve 15–18 mN/m.

Standard tests include: contact angle measurement on the substrate (target < 10° for complete wetting), dynamic surface tension with bubble pressure tensiometer at coating application speed, and drawdown panels on the substrate checking for crawling, fisheyes, or pinholes. Water spotting on dried film indicates insufficient crosslink density, not wetting failure. Foam testing is also needed since many wetting agents also foam.