Views: 0 Author: Site Editor Publish Time: 2025-11-03 Origin: Site
If you work with composite materials, coatings, or adhesives, you’ve likely come across Polyester Resins. These versatile polymers are mainly divided into Saturated Polyester Resin (SPR) and Unsaturated Polyester Resin (UPR).
Although they share a similar chemical foundation, they differ significantly in structure, curing mechanism, and application performance.
At JLON, we focus on producing high-performance Unsaturated Polyester Resins tailored for fiberglass reinforcement, marine structures, and industrial composites.
By understanding the difference between these two types, you’ll be able to choose the right resin system for your specific project.
You can produce saturated polyester resin through polycondensation under controlled temperature and vacuum, resulting in a viscous polymer.
This resin is usually dissolved in organic solvents to make coatings, films, or adhesives—no reactive monomer is required for curing.
To make unsaturated polyester resin, you include unsaturated acids during the reaction process.
The prepolymer is then blended with a reactive monomer (like styrene) to adjust viscosity and enable crosslinking.
When you add a catalyst such as MEKP (methyl ethyl ketone peroxide), it initiates free-radical polymerization, turning the liquid resin into a solid, durable thermoset.
At JLON, you can rely on our advanced production controls and strict temperature management to ensure consistent polymerization, acid values, and mechanical stability in every batch.
Property | Saturated Polyester Resin (SPR) | Unsaturated Polyester Resin (UPR) |
Molecular Structure | Fully saturated (no C=C bonds) | Contains C=C double bonds |
Curing Behavior | Thermoplastic, non-crosslinking | Thermoset, crosslinking with styrene |
Solubility | Solvent-based | Diluted with reactive monomers |
Flexibility | High | Moderate to high (formulation dependent) |
Thermal Resistance | Moderate | High (up to 180–200°C) |
Chemical Resistance | Excellent for coatings | Excellent after curing |
Processing | Solvent coating or extrusion | Hand lay-up, SMC/BMC, RTM, pultrusion |
Cost Efficiency | Moderate | Cost-effective for composites |
Major Applications | Paints, coatings, adhesives, films | FRP, marine, construction, automotive |
Saturated Polyester Resin (SPR) is a thermoplastic resin, primarily used for coatings, adhesives, and films. Its fully saturated molecular structure makes it flexible and solvent-compatible, which is ideal for protective and decorative applications.
SPR forms a uniform, flexible coating that adheres well to metal surfaces.
Provides excellent resistance to moisture, corrosion, and mild chemicals.
Example: Coating of steel coils used in building facades or appliance panels.
Ideal for UV-resistant powder coatings due to good thermal stability.
Maintains color, gloss, and surface integrity under prolonged outdoor exposure.
Example: Outdoor furniture, metal gates, and architectural panels.
Offers smooth film formation, excellent adhesion, and flexibility.
Resistant to cracking or peeling under mechanical stress.
Example: Laminates for furniture, flooring, or protective industrial surfaces.
Solvent-based SPR adhesives provide strong bonding on metals, plastics, and composites.
Can be used in electrical insulation coatings due to flexibility and chemical resistance.
Example: Coating wires, printed circuit boards (PCBs), and insulating components.
Unsaturated Polyester Resin (UPR) is the most widely used thermosetting resin in the composite industry. Its reactive C=C bonds allow crosslinking, resulting in strong, durable, and dimensionally stable materials.
UPR combined with fiberglass produces lightweight, corrosion-resistant FRP products.
Excellent dimensional stability and impact resistance under long-term mechanical load.
Example: Chemical storage tanks, water treatment piping, industrial panels.
UPR-based FRP structures are highly resistant to water, salt, and UV exposure.
Lightweight yet strong, ensuring fuel efficiency and structural integrity.
Example: Small to medium-sized boats, floating docks, marine storage tanks.
High mechanical strength and thermal resistance make UPR ideal for structural panels.
Compatible with reinforcement materials for load-bearing applications.
Example: Prefabricated wall panels, roof sheets, architectural profiles.
UPR enables molding of complex shapes with high surface quality.
Offers good impact resistance and durability in automotive parts.
Example: Exterior bumpers, SMC body panels, interior decorative trims.
High dielectric strength and dimensional stability ensure safety and performance.
Resistant to heat, moisture, and chemical exposure.
Example: Switchgear housings, insulators for transformers, junction boxes.
UPR provides smooth surface finish, excellent polishability, and color retention.
Chemically resistant and easy to mold into complex shapes.
Example: Countertops, sinks, bathtubs, and decorative panels.
JLON Unsaturated Polyester Resin (UPR) offers multiple advantages in mechanical performance, processability, and durability, making it ideal for composites, marine structures, construction, and industrial applications.
Forms a three-dimensional crosslinked network after curing, providing excellent tensile, flexural, and impact strength.
Superior dimensional stability ensures components maintain shape and accuracy under high temperature and humid conditions.
Applications: FRP tanks, boat panels, automotive SMC/BMC structural parts withstand long-term mechanical stress without deformation.
Surface treatment and silane coupling agents enhance adhesion to fiberglass, mineral fillers, and foam cores.
Excellent wet-out ensures uniform resin penetration and minimizes air bubbles or voids.
Applications: Multi-layer FRP laminates, boat decks, and composite sandwich panels achieve maximum structural integrity and durability.
High-purity UPR can withstand elevated temperatures, suitable for industrial equipment and high-temperature environments.
Resistant to acids, alkalis, and many organic solvents, ensuring long-term chemical durability.
Applications: Chemical storage tanks, piping systems, and industrial corrosion-resistant laminates remain stable in harsh environments.
Viscosity is precisely controlled to meet the requirements of hand lay-up, spray-up, RTM, and compression molding processes.
Optimized viscosity ensures easier resin application, full fiberglass wetting, and reduces air entrapment and material waste.
Applications: Hand-laminated FRP, boat hulls, and automotive BMC parts improve production efficiency and product consistency.
Batch-to-batch curing speed and gel time are consistent, preventing incomplete curing or performance variations.
Ensures final components meet mechanical, thermal, and chemical performance standards reliably.
Applications: Industrial tanks, marine structures, and construction panels achieve predictable, long-lasting results for every product.
Every batch of JLON UPR is manufactured and tested according to ISO and ASTM standards.
We test viscosity, gel time, acid value, and mechanical properties—so you can count on stable and repeatable results.
General-purpose UPR: for FRP panels, pipes, and tanks
Marine-grade UPR: improved hydrolysis and mechanical strength
Fire-retardant UPR: halogen-free and low smoke emission
High-strength UPR: ideal for SMC/BMC and structural applications
In short, the key difference between saturated and unsaturated polyester resin lies in their chemical structure and curing behavior:
Saturated Polyester Resin stays thermoplastic and is mostly used for coatings and adhesives.
Unsatrated Polyester Resin can crosslink and cure into a strong thermoset, making it ideal for fiberglass composites.
If you’re looking for high-performance, reliable Unsaturated Polyester Resin, JLON offers a full range of formulations for marine, automotive, construction, and industrial applications—helping you achieve the durability and performance your products need.
