Isophthalic UPR (Marine Grade)

Isophthalic Unsaturated Polyester Resin (Marine Grade) is formulated using isophthalic acid as the primary diacid component, replacing the orthophthalic acid used in general-purpose grades. This structural modification produces a resin with significantly superior hydrolytic resistance, making it the preferred choice for marine hull construction, boat deck laminates, and any application involving prolonged water immersion.

The isophthalic backbone provides tighter polymer packing and reduced ester group density compared to orthophthalic resins, resulting in water absorption values typically 50% lower. Osmotic blistering, a common failure mode in marine FRP, is dramatically reduced when this resin is used in conjunction with an NPG isophthalic gelcoat barrier coat system.

Viscosity at 25°C is 250-500 mPa·s, compatible with hand lay-up, spray-up, and light RTM applications. The cured laminate delivers a flexural modulus of 3.8-4.2 GPa and HDT of approximately 65-75°C under standard cure conditions, rising to 80-90°C with post-cure at 80°C for 2 hours. Widely specified by Lloyd's Register, Bureau Veritas, and other classification societies for marine composite construction.