General Purpose Orthophthalic UPR
Key Features
- Cost-effective general-purpose formulation
- Good glass fiber wet-out and processing latitude
- Compatible with MEKP/cobalt accelerator cure systems
- Balanced mechanical properties for structural FRP
- Wide availability and consistent batch quality
General Purpose Orthophthalic Unsaturated Polyester Resin (UPR) is a versatile thermosetting resin produced by the condensation of orthophthalic anhydride with propylene glycol and maleic anhydride, dissolved in styrene monomer at approximately 35-40% concentration. This workhorse resin delivers a balanced profile of mechanical strength, chemical resistance, and processing versatility suited to a wide range of FRP fabrication methods including hand lay-up, spray-up, and resin transfer molding.
With a viscosity of 300-600 mPa·s at 25°C, it wet-outs glass fibers efficiently and provides a gel time of 15-25 minutes when catalyzed with 1.5% MEKP at room temperature. Cured laminates exhibit a flexural strength of approximately 120 MPa and a tensile strength of 65 MPa, making it suitable for general structural panels, tanks, enclosures, and decorative FRP products.
The resin is compatible with all standard glass fiber reinforcements and can be accelerated with cobalt octoate for workshop-temperature curing. Its cost-effective formulation makes it the industry standard for non-critical structural applications where premium corrosion resistance is not required. Suitable for use with MEKP, benzoyl peroxide, or other peroxide cure systems.
Specifications
| Parameter | Value |
|---|---|
| Acid Value | 15-25 mg KOH/g |
| Appearance | Clear to pale yellow liquid |
| Solid Content | 60-65% |
| Density (25°C) | 1.12-1.14 g/cm³ |
| Styrene Content | 35-40% |
| Viscosity (25°C) | 300-600 mPa·s |
| Gel Time (25°C, 1.5% MEKP) | 15-25 min |
Applications
FAQ
For room temperature cure (20-25°C), use 1.0-2.0% MEKP by weight of resin, with 0.3-0.5% cobalt octoate (6% Co) as accelerator. Higher temperatures require lower catalyst levels. Always add catalyst and accelerator separately — never premix them directly as this creates a fire and explosion hazard.
Direct Contact
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