What are high temperature thermoplastics?
What are high temperature thermoplastics?
High-heat plastics are materials that resist high temperatures well.
To classify a plastic as high heat, its
Heat Deflection Temperature (HDT) must surpass 200°C at 264 psi (1.8 MPa). It means the plastic part can withstand elevated temperatures without significant loss of mechanical properties.
This criteria ensures the material is suited for:
- Long-term service temperature greater than 150°C.
- Short-term exposure to temperatures surpassing 250°C.
This is the core difference with traditional thermoplastics. Under such high-temperature conditions, all other thermoplastics would soften or deform.
High-temperature thermoplastics vs. flame retardant plastics: What's the difference?
High-heat thermoplastics have a chemical backbone that is resistant to extreme temperatures. Flame-retardant plastics have no intrinsic resistance to high temperatures. Compounders use
additives to fight against fire ignition and propagation. High-heat plastics would generally be too expensive for FR applications.
If you are looking for fire resistance, rather
browse flame retarded plastics.
Typical performance profile
Besides their exceptional thermal stability, high-heat plastics exhibit:
- superior chemical and wear resistance,
- radiation resistance,
- resistance to burning,
- excellent mechanical properties
This is why they are apt to replace metals.
Like all plastics, they come with lighter weight and increased design flexibility. Hence, they are great options to support industry sustainability efforts to lower emissions. They are particularly popular in the
EV segment. High-temperature thermoplastics are expensive. Their cost is about ten times that of general-purpose plastics.
What makes high heat plastics thermally resistant?
High-temperature thermoplastics generally gain their temperature resistance from:
-
The introduction of rigid aromatic rings instead of aliphatic rings.
- These groups are added to their molecular structure. It restricts the movement of the backbone chain.
- The aromatic rings need two chemical links to be broken for a chain break. Whereas one chemical link breaks in the case of aliphatic structures.
Degradation of an aromatic and a straight-chain polymer due to thermal aging
Hence mechanical properties, high-temperature capability, and chemical resistance improve. These properties can be often equal to or even better than crosslinked thermosetting polymers.
Finding your way within the high-heat plastics offering
Finding your way within the high-heat plastics offering
Below you can find the list of high-temperature plastics, from the most used to the most niche:
Although polyamides are engineering plastics, you may find some high heat grades suited for metal replacement. Check the section on typical performance boosters to know why.
Already know which plastics you need? Browse for commercial grades and suppliers:
Key characteristics vs. the polymer structure
To help you progress with your identification of the right high temperature plastic, let’s review the chemistries and polymer structure.
Chemistries
High-temperature plastics belong to five chemical families. Here are the reasons to opt for one or the other:
- Polyamides (PAI):
- Strong and durable
- Suited for parts in humid or wet environment
- Easy to shape
- Polyphenylene-Based Plastics (PPS, PSU):
- Exceptional heat resistance
- Resistant to degradation in the presence of aggressive chemicals
- Keep their shape and performance even in extreme temperatures
- Polyketones (PAEK, PEEK):
- Resistant to tough chemicals and solvents, making them great for demanding industrial settings
- Remain stable in hot water and steam environments (hydrolysis resistance)
- Maintain their shape and integrity even under heavy stress and high temperatures (creep resistance)
- Long-lasting parts
- Liquid Crystal Polymers (LCP):
- Low coefficient of thermal expansion
- Can be molded rapidly, which saves time and money for making large quantities of products.
- Excellent electrical properties: LCP has low electrical conductivity and high insulation resistance, making it perfect for electrical and electronic applications
- Fluoropolymers (PTFE, FEP, PFA, ETFE, PVDF):
- Excellent chemical resistance: They offer excellent defense against harsh chemicals and tough environments
- Nonstick and low friction
- Weather and UV resistant
High-heat thermoplastic structures
High-temperature thermoplastics (as all polymers) comprise two molecular structures:
- Amorphous (random order)
- Crystalline (specific order)
| Amorphous |
Semi-crystalline |
- Strength, stiffness
- Isotropic dimensional stability
- Toughness and impact resistance
- Clarity
- Good surface appearance
|
- Chemical resistance
- Wear resistance
- Lower ductility and impact strength
- Opaque
- Low stiffness and creep resistance at high temperatures
- Poor dimensional stability
|
|
|
|
High heat compounds: Typical performance boosters
Why use high heat plastics over metals or thermosets?
Why use high heat plastics over metals or thermosets?
High temperature plastics vs metals
High temperature thermoplastics have continuous operating temperatures of more than 150°C.
Yet, its high temperature resistance provides other essential performance qualities. These include:
-
wear and chemical resistance.
- weight savings in many applications (e.g., automotive).
As a result, they are often considered for metal replacement. Table below summarizes the advantages and disadvantages of high temperature thermoplastics over metals.
|
Advantages Over Metals
|
Disadvantages Over Metals
|
- Low density
- Good noise and vibration damping
- Electrical and thermal insulation or adjustable conductivity
- Good chemical and corrosion resistance
- Increased design freedom
- Adaptable to high volume production processes
- Adaptable to property modification for specific applications
|
- Greater thermal expansion
- Poorer creep resistance
- Lower thermal resistance
- Susceptible to UV, moisture, and oxidation
- Not considered to be a vapor barrier
- Lower mechanical properties
- Plastic parts generally must be redesigned over metal parts
|
High heat thermoplastics vs thermosets
High heat thermoplastics are also often considered as replacements for thermoset polymers. This includes epoxy, phenolic, polyester, etc.
The table below compares the properties of thermosets with thermoplastic resins.
|
Property
|
Thermoset Resin
|
Thermoplastic Resin
|
|
Melt viscosity
|
Low
|
High
|
|
Processing cycle time
|
Long
|
Short
|
|
Processing temperature and pressure
|
Low to moderate
|
High
|
|
Mechanical properties
|
Fair to good
|
Fair to good
|
|
Toughness
|
Low
|
Moderately high
|
|
Moisture resistance
|
Relatively poor depending on the resin
|
Generally high depending on the resin
|
|
Creep
|
Good
|
Poor
|
Comparison Between Neat Thermoset and High Temperature Thermoplastic Resins
The main drawbacks of thermoplastics vs. thermosets are their high melt viscosity and processing temperature.
Currently industry focuses on developing flowable high temperature thermoplastics with enhanced properties. High temperature thermoplastics with excellent flowability offer many advantages:
- ease the processing,
- improve part quality,
- enhance production efficiency in many industries.
How to process high heat plastics?
How to process high heat plastics?
When processing high heat plastics, the primary approach is injection molding. It involves shaping the plastics into various parts and forms.
The three main things you should consider for a successful processing and at the same time environmentally friendly:
- Use of specialized equipment to handle high temperature conditions. Specialized equipment, such as strong molds capable of enduring high temperatures, is utilized for this purpose. These special mold materials need to own superior structural integrity and dimensional stability.
- Precise temperature control prevents polymer degradation and crosslinking at high temperatures.
- Saving Energy: Working with high heat plastics means finding the right mix of making strong materials and using less energy. This involves using efficient heating and cooling systems, along with methods to protect the plastic's strength. This saves money, is eco-friendly, and keeps the plastic useful.
These requirements can impact the polymer's properties and its suitability for the intended application.