What is GPO-3 (UPGM203)

GPO-3 sheet (also known as UPGM203) is a high-performance rigid laminated flame-retardant insulating material widely used in electrical, electronic, and mechanical industries. Manufactured from alkali-free glass fiber mat reinforced with unsaturated polyester resin, GPO-3 offers excellent mechanical strength, electrical insulation, flame resistance, and long-term thermal stability.

1. Composition

Reinforcement：Alkali-free glass fiber mat.

Matrix Resin：Specialty unsaturated polyester resin paste, typically formulated with flame retardants and functional fillers.

2. Core Material Properties

Mechanical Strength：High flexural, compressive, and tensile strength with excellent dimensional stability and resistance to deformation.

Electrical Insulation：High dielectric strength with outstanding arc resistance and a Comparative Tracking Index (CTI) typically ≥ 600V.

Thermal Performance：Class F insulation material with a continuous operating temperature up to 155°C and UL 94 V-0 flame-retardant performance.

Environmental & Machining Performance：Halogen-free, low smoke, low toxicity, and suitable for precision machining processes including drilling, milling, routing, punching, and cutting.

3. Manufacturing Process

Step 1 – Resin Impregnation

Alkali-free glass fiber mats are fully impregnated with a specially formulated unsaturated polyester resin system.

Step 2 – Drying (B-Stage)

The impregnated material is heated to remove volatile components while bringing the resin into a semi-cured (B-stage) condition.

Step 3 – Layer Stacking

Multiple prepreg layers are stacked according to the required sheet thickness.

Step 4 – Hot Press Molding

The stacked material is molded under high pressure at approximately 145°C–165°C, allowing the resin to fully cure and form a rigid laminate.

Step 5 – Finishing

Finished sheets undergo post-curing, edge trimming, sanding, inspection, and packaging to ensure dimensional accuracy and consistent quality.

4. Typical Applications

Electrical Switchgear

• Phase barriers
• Safety partitions
• Arc chutes
• Insulating supports
• Ring Main Units (RMU)

Power Transformers

• Winding bobbins
• Insulating spacers
• Pressure plates
• Tap changer support structures

Electric Motors

• Stator slot wedges
• End winding supports
• Stator washers
• Brush holder brackets

Power Electronics

• High-voltage inverter insulation plates
• Renewable energy inverter components
• Busbar supports
• Electrical mounting structures

Key Advantages of GPO-3

• Excellent electrical insulation performance
• Superior arc and tracking resistance
• High mechanical strength and rigidity
• UL 94 V-0 flame-retardant rating
• Class F (155°C) thermal insulation
• Excellent dimensional stability
• Easy CNC machining and fabrication
• Halogen-free, low smoke, and environmentally friendly
• Ideal for switchgear, transformers, motors, and power electronics