Proportion of GPO-3 (UPGM203) unsaturated polyester resin
The IEC 60893/NEMA GPO-3 standard does not require a fixed resin ratio, only controls the performance of the finished product, and different manufacturers' formulas may fluctuate.
-Unsaturated polyester resin: 30% to 40% wt
-Fiberglass felt: 55-65% wt
-Flame retardant fillers, colorants, and curing agents: 3-7% wt
Typical median values for mainstream high-quality boards: resin ≈ 35 wt%, fiberglass ≈ 60 wt%, additives ≈ 5 wt% * *, density 1.81-1.83 g/cm ³.
Attention: Poor quality GPO-3 will * * reduce the proportion of resin, increase cheap inorganic fillers * *, deviate from density, and significantly reduce arc resistance and CTI leakage marks.
