Polyester resin is a widely used polymer material in industrial manufacturing, but many users are often confused by the difference between saturated polyester resin and unsaturated polyester resin in type selection. In this paper, the chemical structure, performance characteristics and application scenarios will be compared in depth to help you make accurate decisions.
Composition and Reactivity
Unsaturated polyester resins have carbon - carbon double bonds in their molecular structure. These double bonds are very reactive sites. Introducing a suitable catalyst under appropriate conditions (e.g., peroxide) leads to the cleavage of these double bonds. This allows the resin molecules to cross – connect with each other, developing a three – dimensional network. This process of cross - linking is key to the hardening and hardening of the resin. In contrast, saturated polyester resins do not have these double bonds. They are composed of fully saturated carbon - carbon single bonds with chemical structure, and therefore they do not show the same type of cross - linking reaction under normal conditions as unsaturated resins.
Curing and Processing
A key benefit of unsaturated polyester resins is that they can be cured in many ways. They cure at room temperature, which is very convenient for applications where heating equipment is unavailable or impracticable. Therefore, they are suitable for on - site or small - scale production, for example, the hand - layup process of creating small composite products, such as custom - made sculptures or small repair on a boat. Moreover, they are also able to cure more quickly upon exposure to heat, which enables faster production in industrial cases. Saturated polyester resins, however, have typically more complex curing requirements. They often depend on condensation reactions, which generally require higher temperatures and longer processing times. This can pose limitations in applications that require rapid turnaround times.
Comparison of performance advantages
Performance advantages of saturated polyester resin
Excellent chemical stability and weatherability
Molecular chain containing benzene ring structure (such as phthalic anhydride, terephthalic acid, etc.) , giving its rigid characteristics, acid, alkali and organic solvent corrosion resistance, suitable for long-term outdoor exposure environment.
Typical applications: coil coatings topcoats, alcohol resistant industrial coatings, cosmetic stabilizers.
Balanced mechanical properties
High molecular weight linear saturated polyester resin with high strength and toughness, moderate elongation at break, unsaturated polyester resin is suitable for complex molding process (such as molding, impregnation) .
Modification potential: through the introduction of epoxy, acrylic acid and other groups, can further improve the heat resistance (such as flame retardant grade) or electromagnetic properties.
Low shrinkage and machining accuracy
Small volume shrinkage during curing, suitable for precision products (such as printing iron ink, hot coated coil) production, to avoid warping deformation.
Environmental Protection and safety
No volatile toxic substances, in line with food packaging material safety standards, some modified resin can be recycled or biodegradable.
Performance advantages of unsaturated polyester resin
Flexible curing process
unsaturated polyester resin can be cured at room temperature, atmospheric molding, suitable for large-scale on-site manufacturing (such as fiberglass cooling towers, chemical storage tanks) , the process cycle is short.
Cross-linking mechanism: the main chain double bond copolymerizes with styrene to form a three-dimensional network structure, which improves the hydrolysis resistance.
Balance of overall performance
Mechanical properties: tensile bending strength close to epoxy, better than Phenol formaldehyde resin, suitable for bearing structural parts.
Electrical Properties: carbon-oxygen single bond structure gives high insulation, suitable for electronic packaging materials.
Weather Resistance: unsaturated double bond absorb UV, delay aging, suitable for outdoor decorative plate.
Cost-effectiveness and diversity
Variety (such as O-benzene, m-benzene, Vinyl ester) , lower prices, to meet different needs.
Advantages of a particular unsaturated polyester resin type:
M-benzene type: Ester Bond protected by steric hindrance, corrosion resistance is better than O-benzene type.
Vinyl Ester resin: low density of Ester Bond, outstanding acidalkali resistance, suitable for chemical anti-corrosion equipment.
Halogenated polyester: unsaturated polyester resin has excellent self-extinguishing performance, wet chlorine environment corrosion resistance is stronger than conventional resin.
Typical application scenarios
Saturated polyester resin:
Coil coatings (topcoat/primer) , iron printing ink, cosmetic thickeners, food packaging materials.
Unsaturated polyester resin:
Chemical storage tanks/pipes (corrosion resistance) , FRP cooling towers (weather resistance) , electronic insulators (electrical properties) , artificial stone (molding flexibility) .
To conclude, the influence of saturated and unsaturated polyester resins on the material performance under different conditions makes it crucial to choose the right one to base a formulation. Whether you look towards high - strength requirements fulfilled by unsaturated resins in the production of composites or smooth - finish needs catered to by saturated resins in powder coatings, in the world of polymers, every resin type has its own share of unique benefit
