Thermoset and thermoplastic polymers are the most common classes of plastic materials for injection molding. These classes of plastics have varying properties making them suitable for different applications, which we’ll examine in this thermoset vs. thermoplastic comparison.
Product requirements often determine the best material for a project. Thus, understanding the differences between these classes will help determine the ideal material for your projects.
This comprehensive guide gives an overview of thermosets and thermoplastic polymers, their differences, and how to decide which is best for your project. Let’s get to it!
What Are Thermosets?
Thermosets or thermosetting polymers are plastics that can withstand high temperatures without melting. They are liquid resins at room temperature and harden when heat and certain chemicals are exposed. Generally, thermosetting plastics are created with reaction injection molding (RIM) or resin transfer molding (RTM).
In addition, crosslinking occurs between the polymers in the material while curing, causing an irreversible bond between the thermosetting elements. However, one of the cons of thermosetting plastics is the inability to remold them after the initial forming.
Thermosets become resistant to extremely high temperatures, corrosion, and mechanical creep after undergoing the heat-forming process. Hence, thermosets are ideal for parts requiring high heat exposure, tight tolerance, and high strength-to-weight properties.
You should note that overheating can result in thermosetting material deterioration while in a solid state, even though the materials can resist high temperatures. Common thermoset materials include the following:
- Epoxy
- Polyimide
- Phenolics
- Polyurethane
- Polytetrafluoroethylene (PTEE)
- Polyvinylidene Fluoride (PVDF)
- Silicone
Applications of Thermoset
Various industries use thermoset resin to create different components, such as:
- Automotive
- Energy
- Lighting
- Appliance
What Are Thermoplastic Materials?
Thermoplastic materials are resins that melt into a soft, flexible form when exposed to a specific temperature and eventually transform into fluid because of the crossing of the glass or crystal melting transition temperature. Thermoplastics are unlike thermosets; no chemical bonding occurs while processing thermoplastics.
Thermoplastics exist in pellet forms before molding such that once you melt the resin, pouring it into the mold to cool and shape it into preferred shapes is easy. Also, you can re-melt and re-shape the pellet thermoplastics as you desire.
Thermoplastic polymers are highly compatible with recycling, reheating, and remolding without compromising the material’s properties. Hence, thermoplastic materials are ideal for plastic molding, thermoforming, and extrusion. Generally, they exhibit good strength and elasticity and are resistant to shrinking.
Typical examples of thermoplastic materials include the following:
- Acetal Homopolymer Polyoxymethylene
- Acetal Copolymer Polyoxymethylene
- Acrylic
- Polyester
- Polypropylene (PP)
- Polystyrene (PS)
- Polycarbonate (PE)
- Teflon
- Nylon
Applications of Thermoplastic
- Pipes
- Electrical equipment
- Ropes
- Belts
- Insulating electrical cables
Thermoplastic vs. Thermoset: A Comparison Table
Here is a tabular comparison showing the thermosetting thermoplastic difference in terms of properties:
| Properties | Thermosets | Thermoplastics |
| Molecular Structure | Thermosetting resins are network polymers exhibiting excellent molecular bonds with good cross-linking | Thermoplastics are linear polymers. They maintain a straight chain with weak molecular bonds. |
| Microstructure | They consist of reinforcing fibers and resin while in a solid state. | Thermoplastics consist of hard crystalline regions and elastic amorphous in the solid state. |
| Melting Point | Excellent tensile strength and melting points. | Thermoplastic resins have low tensile strength as well as low melting points. |
| Molecular Weight | Thermosets have higher molecular weights. | Thermoplastics have a lower molecular weight. |
| Solubility | They have high resistance to organic solvents. | Organic solvents can dissolve thermoplastic materials. |
| Chemical Resistance | Thermosets have excellent resistance to chemicals and heat. | Thermoplastics exhibit high chemical resistance properties. |
| Mechanical | They have strength from cross-linking. These materials are usually strong and rigid. | Their crystalline nature is responsible for their strength. They are usually elastic and pliable with high impact resistance. |
| Processing MethodsThermosets are best processed using compression molding and reaction injection. | Thermoplastics can be processed using blow molding, injection molding, or extrusion process. |
Differences Between Thermoset and Thermoplastic Polymers
Thermosets and thermoplastics are different plastic resins with varying properties, although they share certain similarities. This section explores the difference between thermoplastic and thermosetting resins:
Melting Point
After heating, the behavior of thermosets and thermoplastics marks a significant difference between these plastic resins. Thermosets have a higher melting point than thermoplastics. Following the heating and cooling of thermoplastic to form the desired shape, you can subject it to heat again to create a new shape or product.
More importantly, the structure of a thermosetting plastic product remains intact even after the initial product is subject to heat. Thus, thermoplastic melts when subjected to heating after curing in contrast to thermosets. Thermosets do not sublime when exposed to heat and remain in their solid shape because thermoplastics have a lower melting point than thermosets.
Aesthetics
Product designers utilize thermoplastic resins due to their high-quality finish. However, the reaction injection molding (RIM) and resin transfer molding (RTM) processes involved in processing thermoset polymers offer a unique possibility of ensuring superior product aesthetics.
You have the opportunity of spraying directly into the mold before pouring the thermoset into the mold. Moreover, these processes permit in-mold coating and painting.
The plastic surface and the paint establish a solid bond with the help of the in-mold painting technique. Thus, it results in excellent adhesion and prevention of chipping, flaking, cracking, and other injection molding flaws.
In addition, thermosets are perfect for low- and high-gloss finishes. Painted thermosets have an appearance like finely detailed textures. Thermosets accommodate the slightest aesthetic touch since they offer excellent flowability.
Corrosion Resistance
The effect of corrosion on a material is one of the factors to consider before selecting a material for a particular product. So, before investing a massive amount into manufacturing a product and losing it to corrosion, ensure you use a material with excellent corrosion resistance.
Although thermoplastics and thermosets show excellent corrosion resistance, thermoplastics have higher chemical resistance than thermosets.
Durability
The durability and ability of polymers to resist heat are crucial factors manufacturers consider when choosing materials for making components for cars and electrical appliances.
As a result, variants of thermosets such as epoxies, rubbers, and polyurethanes are the most common resins product designers use to make plastic parts.
It is important to note that thermoset plastics are more durable than thermoplastics. This is due to the bond between the thermoset polymers, which are stronger than thermoplastics. Thermoplastics lose their shape when heated; meanwhile, thermosets do not lose shape when exposed to heat.
Furthermore, thermosets are traditionally lightweight and flexible materials with high strength, impact resistance, and toughness.
They offer further strengthening and reinforcing when used with materials like fiberglass and carbon. Hence, their excellent structural advantages and dimensional stability gives them an edge over thermoplastics in term of durability.
Thermoset vs. Thermoplastic Polymers Applications
Thermosets are more economical and have a wide range of compatibility. However, most manufacturers prefer thermoset polymers because they can achieve complex geometric shapes quickly and withstand high temperatures. Consequentially, these plastics are suitable for applications that involve heat:
- Medical Components
- Electronic components
- Panels, housing, and doors
- Components and parts for vehicles
- Chemical processing equipment such as cell covers, pipes, and fittings
On the other hand, several industries choose thermoplastic due to their high resistance to chemical attacks like corrosion. Likewise, they are ideal substitutes for metals; as a result, industries such as automotive, plumbing, chemical, construction, biomedical and medical use these polymers in making different components.
Typical applications of thermoplastics include:
- Gas tanks
- Laboratory equipment
- Electrical encapsulation and insulating materials
- Piping systems
- Non-stick cookware
- Industrial machine components
Cost
Thermosetting polymers have higher manufacturing costs than thermoplastics. Although thermoplastic resins are the cheaper option between the two classes, thermosets offer more benefits than thermoplastics.
However, factors such as material, tooling, production cycle time, labor cost, and finishing treatment options determine the overall cost of manufacturing plastic components using either of these polymers.
Nevertheless, it would help if you consider the performance, upfront tooling costs, and surface finish options before selecting a material if budget is a concern for your manufacturing process.
Pros and Cons of Thermoset vs. Thermoplastic Polymers
This section explores the advantages and drawbacks of thermosets and thermoplastics:
Pros of Thermosets
- High resistance to water
- Excellent dimensional stability
- Excellent resistance to corrosion
- High rigidity, strength, and toughness
- Permits flexible product designs
Cons of Thermosets
- They cannot be recycled or remolded
- Lower thermal conductivity than their counterparts
Pros of Thermoplastics
- Excellent resistance to impact
- High resistance to corrosion
- Excellent aesthetic finish
- Improved anti-slip properties
- It is recyclable and very eco-friendly
- Excellent electrical insulation properties
Cons of Thermoplastics
- High cost compared to thermosets
- Degrades when exposed to UV
- It is not compatible with all applications because it becomes soft when heated
Choosing the Best Material for Your Project Between Thermoset vs. Thermoplastic
Thermosets and thermoplastics have a wide range of capabilities and material options suitable for different applications. The purpose these materials can serve is limitless and under favorable conditions. As such, thermosets and thermoplastics are ideal materials with high compatibility for your products.
However, the required products usually determine the type of plastic material you’ll use for these products. So, thermosetting plastics are your go-to choice if your product needs materials capable of withstanding high temperatures.
Thermoplastics are your best chance at making a high-quality product if your project requires corrosion resistance properties.
These materials have outstanding properties that give them an edge over other materials compatible with injection molding. However, real-world applications will demand that you choose the best materials for your products, which is why you need the assistance of professionals.
Kemal Plastic Injection Molding Services
Kemal is your best chance to experience superior plastic injection molding services. We have a highly skilled team of professionals who can analyze your design and decide on the best material for your project. Trust us to offer you the best injection molding services from capable hands.
Our state-of-the-art facility houses next-gen machines integrated with CNC technology that help us to achieve seamless production and faster cycle times. We offer competitive prices for our injection molding services. Don’t hesitate to contact us at Kemal for high-quality injection molded parts.
Conclusion
Thermosets and thermoplastic polymers are available options for several applications, given that the material’s properties are compatible with the application. Nonetheless, thermosets and thermoplastics exhibit significant differences in recyclability, thermal and corrosion resistance, material properties, and more. So, real-world applications require you to scrutinize each material before choosing it for your project.
