Introduction: High-solids — the most pragmatic path to VOC reduction: no compromise on performance, full regulatory compliance
Waterborne coatings are the “darling” for VOC reduction, but in C4 and above heavy-duty anti-corrosion scenarios—the salt spray resistance of waterborne epoxy is still lower than that of solvent-based (1500-2500h vs >3000h). Powder coatings have zero VOC—but curing temperature >160-200°C—unsuitable for heat-sensitive substrates and on-site construction. High-solids coatings solid content >65%-90%—VOC <300-420g/L—do not change the chemical nature of the coating—only reduce solvent usage "performance not compromised—regulatory compliant" are the “most pragmatic—VOC-reducing—solution” for heavy-duty anti-corrosion (C4/C5/CX), engineering machinery and ship coating “not—the—most—revolutionary—but—the—most—reliable”.
High-solid coatings are an eco-friendly coating system that meets the requirements of GB 30981-2020 and the EU Decopaint regulation, achieved through a triple strategy of reducing resin molecular weight (narrow distribution—less chain entanglement), using hyperbranched/dendritic resins (spherical structure/low intrinsic viscosity), and reactive diluents (viscosity reduction + participation in crosslinking/not counted as VOC)—while maintaining coating performance (salt spray resistance/adhesion/flexibility) without reduction—raising solid content from 40-55% to 65-90%—and lowering VOC from >500 to <300-420 g/L.
FAQ
Q1: Why does the “viscosity-solid content contradiction” of high-solid coatings show exponential viscosity increase as solid content rises? Resin molecules exist as random coils in solution—when solid content >50%—molecular coils begin to overlap with each other—chain entanglement—flow resistance surges—viscosity jumps from 2000-5000—”paint—won’t—pour—out—pump—won’t—run—nozzle—clogs”. Viscosity reduction strategies: (1) Reduce molecular weight—Mw from >10000 down to 10-50 times—but too low molecular weight → coating embrittlement—requires precise balance; (2) Narrow molecular weight distribution (PDI<1.5)—eliminate high molecular weight tail "the—longest—chain—=—the—largest—viscosity—contributor"; (3) Hyperbranched resin—spherical—molecules—minimal chain entanglement—intrinsic viscosity only 1/5-1/10 of linear molecules.
Q2: Reactive diluent—why the “viscosity reduction + crosslinking” dual-function—is the optimal solution?Traditional “inert diluent” (xylene/butanol)—viscosity reduction—but volatilizes completely during curing “diluent—=—V—O—C”. Reactive diluent (e.g., epoxy—reactive—diluent—AGE—/—C12-C14—glycidyl—ether)—contains epoxy groups—participates in—curing—reaction—becomes part of—crosslinked—network “no—volatilization—=—not—counted—as—V—O—C” “both—reduces—viscosity—and—provides—crosslinking—kill—two—birds—with—one—stone”. Optimal—addition—level—10-20%—too much—→—coating—brittleness.
Summary
High-solids coatings — three paths to viscosity reduction: low molecular weight narrow distribution / hyperbranched resin (spherical, low entanglement) / reactive diluents (viscosity reduction + crosslinking). “The most pragmatic VOC-reduction solution — heavy-duty anticorrosion — engineering — machinery — marine — first choice”. Kexin New Materials provides high-solids formulation and viscosity-reduction technical support. “Performance uncompromised — regulatory compliance — cost controllable”.