The difference between saturated and unsaturated polyester resin
Saturated and polyester unsaturated resin differ significantly in their chemical structures and processing behaviors. These differences enable engineers and manufacturers to select the most suitable material for each specific application. Various industries rely heavily on polyester unsaturated resin due to its ability to produce strong, lightweight composites used in construction, automotive, and marine sectors.
Key Takeaways
Saturated polyester resins do not have double bonds. This makes them very stable and tough. They resist chemicals, UV light, and heat well. They are great for coatings and things that need to last a long time.
Unsaturated polyester resins have double bonds. These bonds help them cure fast and form strong links. They are good for making light but strong things like fiberglass.
Use saturated resins if you want better chemical and weather resistance. They also cure more slowly. Use unsaturated resins if you need faster curing and more flexibility. They work well for building or marine uses.
Think about where and how you will use the resin. Check if it will face UV light, chemicals, or need to be strong. This helps you pick the right resin.
You can add things like fiberglass or fillers to make the resin stronger. Good curing is important for the best results.
Key Difference
Structure
Saturated and unsaturated polyester resins are different at the smallest level. Saturated polyester resins have only single bonds in their backbone. This means there are no double or triple bonds in the main chain. To make these, manufacturers mix glycols with acids like isophthalic acid or phthalic anhydride. The result is a stable polymer chain that is fully saturated.
Unsaturated polyester resins have double bonds in their backbone. These double bonds come from using unsaturated dicarboxylic acids, like maleic anhydride or fumaric acid. The double bonds make the resin "unsaturated." Both types are made by condensation reactions. But the double bonds in unsaturated resins change how they act and what they are used for.
Note: Double bonds or no double bonds in the backbone change how each resin reacts and what products it can make.
Properties
Saturated and unsaturated polyester resins have different physical and chemical properties. These differences come from their special molecular structures.
Reactivity and Curing:
Unsaturated polyester resins have double bonds. These let them go through free-radical polymerization. They can cure fast at room temperature with initiators. The curing makes a strong, crosslinked network. This makes the material hard and tough.
Saturated polyester resins do not have these double bonds. They need outside curing agents and often need more heat and time to set. Their curing is slower and less flexible.
Mechanical Properties:
Unsaturated polyester resins become hard and stiff after curing. They can be strong and flexible, especially with additives or fibers. This makes them good for building and aerospace parts.
Saturated polyester resins are strong and tough but more stiff and less bendy. Their structure gives great shape stability and low shrinkage. This is important for products that need to keep their shape.
Chemical and Environmental Resistance:
Saturated polyester resins resist chemicals, UV light, and weather very well. Their stable backbone makes them good for coatings, adhesives, and insulation.
Unsaturated polyester resins also resist chemicals and corrosion, especially after crosslinking. They stick well to glass fibers. This makes them a top pick for fiberglass reinforced plastics (FRP).
Thermoplastic vs. Thermosetting:
Saturated polyesters can be thermoplastic or thermosetting, based on how they are made.
Unsaturated polyesters are usually thermosetting. They form a hard, permanent structure after curing.
Property/Feature | Saturated Polyester Resin | Unsaturated Polyester Resin |
|---|---|---|
Molecular Structure | No carbon-carbon double bonds | Contains carbon-carbon double bonds |
Chemical Reactivity | Non-reactive backbone, needs external curing | Reactive double bonds enable crosslinking |
Curing Process | Slower, needs heat or special agents | Rapid, cures at room temperature with initiators |
Mechanical Properties | High strength, rigid, tough | Hard, rigid, more flexible after curing |
Chemical & UV Resistance | Excellent | Good |
Typical Applications | Coatings, adhesives, films | FRP, marine, construction, pipelines |
Tip: Pick saturated or unsaturated polyester resin based on how fast you need it to cure, how strong or flexible you want it, and how much resistance to chemicals or weather you need.
Saturated Polyester Resin
Definition
Saturated polyester resin is a thermoset polymer. It is made by mixing a saturated polycarboxylic acid with a polyhydric alcohol. This makes a strong, cross-linked structure. The resin has a stable backbone with no double bonds. Because of this, it resists chemicals, heat, and harsh weather. Manufacturers like it for being tough, flexible, and hard. Its structure helps it last a long time in many industries.
Features
Saturated polyester resin is special because of its chemical and physical traits.
The resin’s structure is fully saturated, so there are no double bonds.
This makes it very resistant to chemicals and gives it strong electrical properties.
It keeps its shape and works well even when it gets hot.
The resin does not break down or rust easily, so it lasts a long time.
It does not crosslink as quickly as unsaturated polyester resin, so it is not the best for fiberglass-reinforced plastics.
Many companies pick saturated polyester resin because it is better for the environment, especially in green coatings.
The resin is also hard and flexible, which is good for things that need to be strong but also bend a little.
Note: Saturated polyester resin often works better than unsaturated types when it is very hot or when chemicals are strong.
Uses
Many industries use saturated polyester resin because it is useful and dependable.
In construction, it is used for roofing, wall panels, and coatings. These jobs need something that can handle bad weather and chemicals.
Car and transport companies use it in light parts and coatings to save fuel and make things last longer.
Boats and marine buildings use it because it does not let water in and can be shaped easily.
Makers of electrical and electronic items use the resin for insulation and coatings that stop fires.
Things like bathroom sinks and home appliances use it because it is tough and does not get damaged by chemicals.
Industry | Key Benefits | |
|---|---|---|
Construction | Coatings, roofing, wall panels | Weather and chemical resistance |
Automotive & Transport | Weight reduction, durability | |
Marine | Composites, coatings | Water resistance, easy molding |
Electrical & Electronics | Insulation, flame-retardant coatings | Electrical safety, insulation |
Consumer Goods | Household items, fixtures | Durability, chemical resistance |
Polyester Unsaturated Resin
What Is Polyester Unsaturated Resin
Polyester unsaturated resin is a man-made polymer. It is made by mixing polyhydric alcohols with unsaturated and sometimes saturated dibasic acids. Water is taken out during the process by heating and turning it into steam. This helps finish the reaction. Companies usually sell this resin mixed with a liquid called styrene. Styrene helps control how thick the resin is and helps it harden. Special chemicals called initiators and promoters make free radicals. These free radicals start a chain reaction at the unsaturated bonds. This reaction connects the polymer chains and makes a strong, crosslinked network. The table below shows the main facts about polyester unsaturated resin based on chemical industry rules:
Aspect | Description |
|---|---|
Polymer Type | Condensation polymer from polyols and unsaturated/saturated dibasic acids |
Typical Polyols | Glycols (ethylene glycol, propylene glycol) |
Typical Acids | Phthalic acid, maleic anhydride, etc. |
Curing Mechanism | Free radical cross-linking at unsaturated sites |
Resin Formulation | Sold in styrene solution for processability |
Key Properties
Polyester unsaturated resin is special because it can make strong and light composites. It reacts with vinyl monomers to make a solid network that cannot melt or dissolve. This network gives the resin high strength when pulled, bent, or squeezed. The resin does not get damaged by acids or many other chemicals. This makes it good for tough places. It can be used at low temperatures, so molds and other parts do not get too hot. The resin sticks well to glass fibers. This makes fiber-reinforced plastics (FRPs) that are very strong. It also works as good electrical insulation and lets designers make many shapes. RealLand’s polyester unsaturated resin reacts better, has a lighter color to spot problems, and is more stable. RealLand’s products meet CCS, RoHS, REACH, EMS, and QMS rules, so they follow world standards.
Main Applications
Polyester unsaturated resin is used in many fields. Builders use it for roofing, outside walls, and as glue in concrete mixes. Because it is light and does not rust, it is great for building parts and things like bridges and pipes. In boats, it is used for hulls and decks that can handle saltwater and bumps. Makers of electrical and electronic items use it to cover parts and make insulators. Car companies use it for body panels and inside parts to make cars lighter and better. Things like bathtubs and countertops use it because it is tough and looks nice. RealLand sells polyester unsaturated resin for FRP, boats, bathroom items, SMC/BMC, pultrusion, and casting. This helps many companies make different composite products.
The difference between saturated and unsaturated polyester resin
Curing
The way polyester resins harden is different. Unsaturated polyester resins harden by free radical crosslinking. This starts when radical initiators, like benzoyl peroxide, react with double bonds in the resin. Catalysts, promoters, light, or heat can help this reaction. The result is a strong, crosslinked network that forms fast at room temperature. Saturated polyester resins do not have double bonds. They harden by oxidation and aging, not by crosslinking. So, saturated resins do not make the same hard network as unsaturated ones.
Tip: Unsaturated polyester resins harden faster and make a tougher structure. This makes them great for fiberglass composites.
Strength & Flexibility
Unsaturated polyester resins are strong after they harden. They become stiff and can hold heavy things, especially with glass fibers. These resins also bend a little, which helps stop cracks. Saturated polyester resins are strong and tough but are more stiff. They keep their shape and do not bend much. This is good for coatings and films.
Resistance
Unsaturated polyester resins resist UV rays and water well.
They do not work as well against strong alkalis or organic solvents.
These resins can get brittle and may shrink or crack when hardening.
Their heat resistance is usually between 60–100 °C.
Saturated polyester resins, and vinyl esters, have better chemical and weather resistance.
Vinyl esters resist solvents and corrosion better than unsaturated polyesters.
Note: Adding things like graphene can make unsaturated polyester resins resist more damage.
Cost
Unsaturated polyester resins cost less than saturated ones. Their lower price and fast hardening make them good for big projects. Saturated polyester resins cost more because they resist more and last longer. Companies use them when they need things to last a long time.
Table
Feature | Unsaturated Polyester Resin | Saturated Polyester Resin |
|---|---|---|
Curing | Fast, crosslinked network | Slow, oxidation/aging |
Strength & Flexibility | High, flexible with reinforcement | High, more rigid |
Chemical Resistance | Moderate | High |
UV/Weather Resistance | Good | Excellent |
Cost | Lower | Higher |
Typical Use | FRP, marine, construction | Coatings, films, insulation |
Choosing the Right Resin
Factors
Picking the right polyester resin depends on many things. Every job needs something special. Knowing these things helps you get the best results and long-lasting products.
Saturated Polyester Resin | Unsaturated Polyester Resin | |
|---|---|---|
Chemical Resistance | Excellent, suitable for harsh environments | Limited resistance to certain chemicals and solvents |
UV Resistance | Superior, maintains integrity under prolonged UV exposure | Susceptible to UV degradation leading to color fading |
Mechanical Properties | Limited mechanical strength | High strength-to-weight ratio, excellent adhesion |
Curing Time | Longer curing time, especially for thicker coatings | Requires careful control due to shrinkage during curing |
Cost | Higher cost | Generally lower cost |
Flexibility in Formulation | Less flexible | Easily modified with additives (fillers, pigments, flame retardants) |
Application Suitability | Ideal for coatings, outdoor, and chemical-resistant uses | Ideal for structural, composite, and lightweight applications |
Heat Resistance | Better heat resistance | Lower heat resistance, not suitable for high-temperature uses |
Environmental Factors | Performs well under UV, chemical exposure, temperature fluctuations | Requires evaluation of UV exposure, temperature, humidity, and chemical exposure |
Reinforcement | N/A | Can be reinforced with fiberglass or carbon fiber for enhanced strength |
Tip: Always pick the resin that fits the place it will be used. If there is a lot of sun or strong chemicals, use a resin that can handle it.
Here are some other things to think about:
Check how much protection you need, like against chemicals, fire, or breaking.
Look at the weather, such as how hot, wet, or sunny it gets.
Think about using fiberglass to make the resin stronger.
Add fillers to make the resin harder and tougher.
Make sure you cure the resin the right way for the best results.
The weather and environment matter a lot when picking resin. Hot days, water, and sunlight can change how resins work. Water can make the resin swell and get weaker. Additives can help stop damage from sun and chemicals. Clean resins last longer and work better in hard places.
The biggest differences between saturated and unsaturated polyester resins affect how they are used. The table below shows these differences:
Feature | Saturated Polyester Resin | Unsaturated Polyester Resin |
|---|---|---|
Chemical Structure | No double bonds | Contains double bonds |
Curing Requirement | No catalyst needed | Needs catalyst for curing |
Chemical Resistance | High | Moderate |
Mechanical Strength | Good | Excellent |
Flexibility | High | Moderate |
Price | Higher | More economical |
Typical Applications | Coatings, films | Composites, molding, fiberglass |
Picking the right resin helps products last longer and work better. Companies should look at what their project needs. They should test the materials and talk to experts. RealLand can help companies pick the best polyester unsaturated resin for what they need.
FAQ
What is the main difference between saturated and unsaturated polyester resin?
Saturated polyester resin has only single bonds in its structure. Unsaturated polyester resin has double bonds in its structure. The double bonds let unsaturated resin cure and make strong, crosslinked materials.
Why do manufacturers use unsaturated polyester resin in composites?
Unsaturated polyester resin sticks well to glass fibers. This makes composites that are strong and light. Many companies use it for things like boats, pipes, and building panels.
Can saturated polyester resin be used for fiberglass products?
Saturated polyester resin is not good for making fiberglass products. It does not have double bonds for crosslinking. Most fiberglass items use unsaturated polyester resin for better strength and lasting power.
How does RealLand’s unsaturated polyester resin stand out?
RealLand’s unsaturated polyester resin reacts better, has a lighter color, and is very stable. The company follows world standards and gives custom solutions for industries that need strong FRP and composite materials.
