Thermoset vs Thermoplastic, are two major plastic materials in the injection molding process. Even though thermoset plastic and thermoplastic are similar, they have key differences. Sometimes, thermoplastics are the better choice, and other times thermosets are better. So, it is important to know the differences between thermoset and thermoplastic and to make smart decisions.
This guide will introduce those two plastics and analyze their advantages and disadvantages. Join us to get a clear understanding of thermoset and thermoplastic materials, and help you choose the right one for your project.
What is Thermoset Plastic?
Thermoset plastics undergo a chemical reaction during molding that irreversibly sets the material into a fixed shape. Once cured, they cannot be melted or reshaped. Common examples include epoxy and phenolic resins. Thermosetting is one type of polymer plastic. Having a deeper understanding in polymer types, please read our blog: Understanding Polymer Types: Comparing Plastics and Elastomers
Thermoset Plastic Chemical Makeup
At the core of thermoset plastics is a network of polymer chains held together by strong cross-links. The key feature is the presence of reactive sites within the polymer molecules that allow for the formation of these cross-links.
Thermoset Plastic Molecular Structure
The molecular structure of thermoset plastics is characterized by a three-dimensional network. As the material undergoes the curing process, the polymer chains link together, creating a rigid and durable structure. The cross-linking structure contributes to the exceptional heat resistance and dimensional stability of thermoset plastics. Once set, they cannot be remolded or reshaped, making them ideal for applications where durability and high-temperature performance are paramount.
Common Thermoset Plastic Materials
Here are some common thermosetting plastics that are widely used by manufacturers:
- Phenolics
- Silicone
- Melamine
- Epoxy
- Polyvinylidene
- fluoride (PVDF)
- Polytetrafluoroethylene (PTFE)
- Polyurethane
- Polyimide
Advantages of Thermoset Plastic
High Durable and Rigid
Thermosets are known for their durability and rigid structure. Once cured, they become hard and retain their shape, making them suitable for applications where dimensional stability is crucial.
High Heat Resistance
Thermosets exhibit excellent heat resistance, making them ideal for applications that involve exposure to high temperatures. This property is valuable in industries such as automotive, aerospace, and electronics.
Good Chemical Resistance:
Many thermosetting plastics are resistant to a wide range of chemicals, including acids and solvents. This chemical resistance makes them suitable for use in corrosive environments and chemical processing industries.
Good Electrical Insulation
Thermosets are often used in electrical applications due to their excellent electrical insulation properties. This makes them suitable for manufacturing electrical components and insulators.
Great Strength and Stiffness
Thermosetting plastics generally have high strength and stiffness, making them suitable for applications where structural integrity is essential. This includes components in the automotive and construction industries.
Strong Dimensional Stability
Once cured, thermosets maintain their shape and do not soften or deform under heat. This dimensional stability is advantageous in applications where precise tolerances are required.
Excellent Moldability
Thermosetting plastics can be molded into complex shapes during the curing process. This feature allows for the production of intricate and detailed components, making them versatile in various manufacturing processes.
Adhesive Properties
Some thermosetting resins, such as epoxy, have excellent adhesive properties. They form strong bonds with various materials, making them suitable for use in adhesives, coatings, and composite materials.
Design Flexibility
Thermosets can be tailored to meet specific design requirements, allowing manufacturers to create custom formulations for various applications. This design flexibility enhances their versatility in different industries.
High Strenght to Weight Ratio
The thermoset components can offer significant strength and structural integrity while remaining relatively lightweight. This advantage is particularly crucial in industries such as aerospace and automotive.
Disadvantages of Thermoset Plastic
Non-recyclable (Cannot be remolded)
One significant drawback of thermoset materials is their non-recyclable nature. Once cured, the cross-linking process that gives thermosets their desirable properties also makes them difficult to remold. Compared to thermoplastics, this limits their sustainability and recyclability compared to certain thermoplastics.
Poor Thermal Conductivity
Thermoset materials generally have poor thermal conductivity, which can be a disadvantage in applications where efficient heat dissipation is important. For example, in electrical housing or electronic components, poor thermal conductivity may lead to heat retention and affect overall performance.
Brittleness
Some thermoset materials can be inherently brittle, especially when compared to certain thermoplastics. This brittleness may limit their use in applications where flexibility and impact resistance are important. Modifications such as reinforcement with fibers are often necessary to mitigate this drawback.
What is Thermoplastic?
Thermoplastics represent a class of polymers characterized by their unique chemical composition and structural properties. Thermoplastics can be melted and reshaped multiple times without undergoing a chemical change. Examples of thermoplastics include polyethylene and polypropylene. The molding process for thermoplastics involves heating the material to a molten state, shaping it, and then cooling it to solidify the desired form.
Thermoplastic Chemical Composition
At the core of thermoplastic materials is a long-chain polymer molecule. These polymer chains consist of repeating monomer units linked together through covalent bonds. The chemical composition varies based on the specific type of thermoplastic. Common types include polyethylene, polypropylene, polyvinyl chloride (PVC), polystyrene, and many others.
Thermoplastic Molecular Structure
The molecular structure of thermoplastics is characterized by linear or branched polymer chains. Unlike thermosets, these chains do not form a three-dimensional network with strong cross-links. In their natural state, thermoplastics are solid, but they soften when heated and return to a solid state upon cooling.
Common Thermoplastic Materials
Here are some common thermoplastic materials widely used in various industries:
- Acrylic
- Nylon
- Acetal Copolymer Polyoxymethylene
- Acetal Homopolymer Polyoxymethylene
- Polycarbonate (PC)
- Polyethylene (PE)
- Polystyrene (PS)
- Polypropylene (PP)
- Polyvinylchloride (PVC)
- Polyethylene terephthalate (PET)
- Teflon
Zhongde has produced injection molding plastic parts in thermoplastic, click to view our previous products.
Advantages of Thermoplastic
Corrosion Resistance
Thermoplastics, such as polypropylene and polyethylene, often exhibit excellent resistance to corrosion, making them suitable for applications in corrosive environments.
Recyclable and Reshapeable
One of the key advantages of thermoplastics is their ability to be melted and reshaped multiple times without undergoing a chemical change. This allows for flexibility in manufacturing and recycling.
Chipping Resistance
Thermoplastics can provide resistance against chipping, making them suitable for applications where durability and impact resistance are essential.
Good Electrical Insulation
Many thermoplastics, including PVC and certain polyesters, offer good electrical insulation properties. This makes them valuable in electrical and electronic applications.
Enhanced and Anti-Slip Properties
Certain thermoplastics can be formulated to exhibit enhanced anti-slip properties. This is advantageous in applications where slip resistance is critical, such as flooring or safety equipment.
Eo-friendly and Recyclable
Thermoplastics are known for their recyclability, contributing to environmentally friendly practices in material usage and waste reduction.
Excellent Impact Resistance
Thermoplastics, like polycarbonate and ABS, often demonstrate excellent impact resistance, making them suitable for applications where the material may be subjected to mechanical stress.
Better Aesthetic Finishing
Thermoplastics can be molded to achieve a wide range of aesthetic finishes. This is beneficial in applications where appearance and design play a significant role.
Good Adhesion to Metals
Some thermoplastics have good adhesion properties, allowing them to bond well with metals. This is advantageous in applications where a strong bond between the plastic and metal is required.
Disadvantages of Thermoplastic
Can Degrade When Exposed to UV
Continuous exposure to ultraviolet (UV) radiation from sunlight can lead to degradation, causing changes in color, loss of mechanical properties, and overall reduced performance. UV stabilizers or additives are often incorporated into formulations to mitigate this issue.
May Soften When Exposed to Heat
Many thermoplastics have a temperature range within which they maintain their structural integrity. Beyond this range, they may soften or even melt. This limitation makes them unsuitable for high-temperature applications where materials need to retain their strength and form. High-temperature thermoplastics or thermosetting plastics are often chosen for such scenarios.
Can Be More Expensive Than Thermoset
While the cost of materials can vary, in some cases, thermoplastics may be more expensive than their thermoset counterparts.
Major Difference Between Thermoset and Thermoplastic
Although thermoplastics and Thermosets are similar plastic polymers in some cases, there are some differences between thermosetting and thermoplastic. We will discuss these differences under the following aspects:
Different Curing Process:
Thermoset: Thermosets undergo a curing process, also known as polymerization or cross-linking. This process is irreversible. Thermosets do not melt and flow once cured, and their structure remains stable at elevated temperatures.
Thermoplastic: Thermoplastics do not undergo a curing process. Instead, they are formed by melting and cooling. This allows them to be melted and reshaped multiple times without undergoing a chemical change.
Different Physical Properties
Thermoset:
- Rigidity: Generally rigid and hard after curing.
- Strength: Often exhibits high strength and dimensional stability.
- Heat Resistance: Excellent heat resistance due to the stable cross-linked structure.
- Chemical Resistance: Good chemical resistance, particularly against solvents and corrosive substances.
Thermoplastic:
- Flexibility: Can vary from flexible to rigid depending on the specific type.
- Strength: Strength may vary, and some thermoplastics may have lower tensile strength compared to thermosets.
- Heat Resistance: Moderate heat resistance; softening and melting occur within a defined temperature range.
- Chemical Resistance: Varies among different thermoplastics, with some exhibiting good chemical resistance.
Different in Applications
Thermoset: Commonly used in applications requiring high heat resistance, dimensional stability, and durability. Examples include automotive parts, electrical insulators, aerospace components, and consumer goods.
Thermoplastic: Widely used in diverse applications due to their versatility and recyclability. Applications range from packaging, consumer products, and medical devices to automotive components and construction materials.
Different Aesthetics
Thermoset: Typically exhibits a smooth and polished surface finish after molding. Can be used for applications where aesthetic appearance is important.
Thermoplastic: Surface finish may vary depending on the molding process and specific type of thermoplastic. Can achieve a wide range of textures and finishes, offering flexibility in aesthetic design.
Different Cost Consideration
Generally, thermosets are more expensive than thermoplastics.
Thermoset: Due to the more complex curing process, tooling costs, equipment costs, and labor costs can be higher.
Thermoplastic: Generally lower cost due to the less complex molding process and faster production cycles.
Thermoset vs Thermoplastic: Which Material is the Best?
Selecting the right plastic material is important for ensuring the performance and durability of your products. Both thermoplastic and thermosetting plastic offer a wide range of options. The choice between thermoplastic and thermoset is based on the specific requirements of your desired product.
If your application demands resilience in the face of high temperatures, thermosetting plastics are the preferred choice. Thermoset plastics excel in environments where heat resistance, structural integrity, and chemical resistance. On the other hand, if your product is working in corrosive materials and requires ease of production at competitive pricing, thermoplastics would be better. Thermoplastics are ideal for crafting high-volume parts with complex shapes, making them metal alternatives. Moreover, their recyclability and reusability contribute to long-term cost savings.
The material selection process involves careful consideration of factors such as impact resistance, strength, and heat resistance. Choosing the wrong material can impact the functionality of even the best-designed product. Therefore, when you choose plastic materials, looking for professional assistance is important. Their expertise can guide you in making the informed choice for your specific application, ensuring the success and longevity of your products in the real world.
Related post: Plastic Material Selection Guide for Your Manufacturing Process
Zhongde is Your Best Injection Molding Partner
In conclusion, the choice between thermoplastic and thermosetting plastic materials is an important decision that influences the performance and functionality of your products. Both thermoplastic and thermoset offer a wide of options, each excelling in specific applications.
If you are in trouble with plastic material selection, Zhongde is ready to offer help. Zhongde has professional engineers who will analyze your product design and help you select the suitable plastic materials for your project. Zhongde provides custom plastic injection molding with advanced injection molding machines and injection mold tools. We will offer high-quality injection molding services and custom plastic products at competitive prices. Welcome contact Zhongde if any requirements.
FAQs about Thermosets and Thermoplastic
In general terms, thermoset plastics are often perceived as having high strength and dimensional stability compared to thermoplastics. Thermoset plastics, after undergoing the curing process, develop a strong network of crosslinks that contributes to their rigidity and dimensional stability. Thermoplastics can soften when heated and typically lack strong crosslinking.
Thermoplastics, in general, are not toxic. The toxicity of a thermoplastic material depends on the specific type of plastic, its composition, and any additives or processing agents used in its production. Most commonly used thermoplastics, such as polyethylene, polypropylene, polyvinyl chloride (PVC), and others, are considered safe for use in various applications.
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