Unsaturated polyester resin (UPR) is one of the most versatile and widely used thermosetting polymers in the composites industry. It is formed by the condensation of unsaturated acids or anhydrides—such as maleic anhydride or phthalic anhydride—with polyols like ethylene glycol or propylene glycol.
At room temperature, UPR is a viscous liquid. When combined with a curing agent (commonly methyl ethyl ketone peroxide, or MEKP), it undergoes a crosslinking reaction that converts it into a solid, three-dimensional structure. This transformation gives the material excellent mechanical strength, dimensional stability, and chemical resistance, making it ideal for producing high-performance composites.
Because of its excellent mechanical and chemical performance, unsaturated polyester resin is one of the most widely used polymers in the composites industry. It serves as a key matrix material in the production of fiberglass-reinforced plastics (FRP), marine components, automotive parts, pipes, tanks, and construction materials.
Key Properties of Unsaturated Polyester Resin
| Property | Description |
| Mechanical Strength | Offers high tensile and flexural strength when reinforced with fiberglass. |
| Chemical Resistance | Resists corrosion and degradation from acids, alkalis, and solvents. |
| Dimensional Stability | Maintains shape and performance under thermal and mechanical stress. |
| Versatility | Compatible with fillers, pigments, and reinforcements for diverse applications. |
| Ease of Processing | Can be molded, laminated, or cast with simple equipment. |
Main Types of Unsaturated Polyester Resin
| Type | Characteristics | Common Applications |
| Ortho Resin | Cost-effective and general-purpose; moderate chemical resistance | Automotive parts, panels, consumer goods |
| Iso Resin | Enhanced heat and corrosion resistance | Pipes, tanks, and marine products |
| Bisphenol-A Resin | Excellent chemical and hydrolysis resistance | Chemical storage tanks, industrial components |
| DCPD Resin | Low shrinkage, low viscosity, and good toughness | Gelcoats, sheet molding compounds (SMC) |
Applications of Unsaturated Polyester Resin
Unsaturated polyester resin is the backbone of many modern composite products. Its adaptability allows it to be used across multiple industries, including:
- Marine: Boat hulls, decks, and reinforced structures
- Construction: FRP panels, sanitary ware, and building reinforcements
- Automotive: Lightweight body components and interior panels
- Industrial: Chemical tanks, pipes, and corrosion-resistant linings
- Electrical: Encapsulation materials and insulating parts
Curing System – The Role of MEKP
The curing of UPR typically relies on MEKP (methyl ethyl ketone peroxide) as the initiator. When MEKP is added, a free-radical polymerization reaction begins, linking resin molecules into a strong polymer network.
The result is a rigid, durable, and thermally stable composite capable of performing under demanding conditions.
Why Choose Unsaturated Polyester Resin
- Excellent balance of cost and performance
- Wide compatibility with fiberglass and fillers
- Reliable surface finish and gloss retention
- Broad formulation flexibility for different industries
Smarter Sourcing at Thousands Chemicals
At Thousands Chemicals, you can find a comprehensive range of unsaturated polyester resin products and related materials, including MEKP curing agents, fillers, and reinforcements, all from vetted and reputable suppliers.
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