Request a Quote
High Temperature Materials
Introduction
Selecting a plastic for a high-temperature application involves more than comparing heat-deflection temperatures on a datasheet.
A material that performs well during short-term heat exposure may not maintain stiffness, dimensions, mechanical strength, or chemical resistance during continuous service. Mechanical load, thermal cycling, moisture, chemical exposure, wall thickness, reinforcement, and molding conditions can all influence how an injection molded component performs at elevated temperatures.
For this reason, engineers should evaluate the complete operating environment rather than simply choosing the polymer with the highest temperature rating.
This guide explains the main factors that influence high-temperature material selection and reviews commonly used thermoplastics for demanding injection molded applications.
What Makes a Plastic Suitable for High Temperatures?
High-temperature performance can refer to several different material behaviors.
Depending on the application, engineers may need to evaluate:
- Continuous service temperature
- Short-term peak temperature
- Heat deflection
- Mechanical strength at temperature
- Creep resistance
- Dimensional stability
- Thermal expansion
- Thermal cycling
- Chemical resistance at elevated temperature
- Flame performance
These properties are related, but they are not identical.
For example, a plastic may resist short-term heat exposure but gradually deform under continuous mechanical load. Another material may remain dimensionally stable but require significantly more demanding injection molding conditions.
The correct material therefore depends on how the part is actually used.
1. Define Continuous and Peak Temperatures
The first step is to define the real thermal environment.
Ask:
- What is the normal operating temperature?
- What is the maximum continuous temperature?
- Are there short-term temperature spikes?
- How often do those spikes occur?
- How long does the component remain hot?
- Does the product return to room temperature between cycles?
A short exposure to elevated temperature is very different from continuous service over thousands of hours.
Designers should avoid selecting materials based only on maximum short-term temperature data if the application requires long-term performance.
2. Consider Mechanical Load at Temperature
Heat often reduces polymer stiffness and increases creep.
This becomes important for:
- Structural brackets
- Fasteners
- Connectors
- Sensor housings
- Valve components
- Load-bearing covers
- Electrical components
- Insert-molded parts
A plastic that performs well without load may slowly deform when subjected to continuous stress at elevated temperature.
For structural applications, engineers should therefore evaluate mechanical behavior at the actual operating temperature rather than relying only on room-temperature tensile or flexural data.
Glass- or carbon-fiber reinforcement may improve stiffness, creep resistance, and dimensional stability, but reinforced grades also change flow, shrinkage, warpage, and tooling requirements.
3. Evaluate Dimensional Stability
High-temperature components often contain precision features that must maintain alignment throughout thermal cycling.
Examples include:
- Connector interfaces
- Sensor locations
- Bearing seats
- Seal surfaces
- Precision holes
- Metal inserts
- Mounting features
Dimensional behavior depends on:
- Thermal expansion
- Mold shrinkage
- Material structure
- Reinforcement
- Fiber orientation
- Part geometry
- Cooling balance
- Residual stress
Materials such as PPS, PEI, PEEK, and certain reinforced engineering plastics are frequently considered where elevated temperature and dimensional stability must be combined.
However, even a dimensionally stable resin can warp if wall thickness, gate location, fiber orientation, or cooling design is poorly controlled.
4. Consider Chemical Exposure at Elevated Temperature
Chemical compatibility often becomes more demanding as temperature rises.
A polymer that performs adequately in a chemical at room temperature may degrade faster when the same fluid is heated.
Potential exposures include:
- Oils
- Fuels
- Coolants
- Cleaning agents
- Acids
- Bases
- Solvents
- Automotive fluids
- Process chemicals
This is particularly important in under-hood automotive systems, industrial fluid handling, semiconductor equipment, laboratory systems, and chemical-processing applications.
Materials such as PPS and PEEK are often considered when high temperature must be combined with aggressive chemical exposure. AccuMolds' existing PEI guidance also notes that chemical compatibility must be evaluated together with concentration, exposure time, molded-in stress, applied stress, and temperature.
Common High-Temperature Injection Molding Materials
The following materials are commonly considered as temperature requirements increase.
Polycarbonate (PC)
Polycarbonate offers a useful balance of:
- Heat resistance
- Impact strength
- Toughness
- Transparency
- Dimensional capability
PC can be suitable for applications where temperature requirements exceed those of general-purpose plastics but do not require ultra-high-performance polymers.
Typical applications include:
- Electrical housings
- Protective covers
- Lighting components
- Equipment enclosures
- Automotive components
Its main advantage is that it combines elevated-temperature capability with excellent impact resistance.
However, PC requires proper drying and careful process control, especially for transparent or stress-sensitive components.
Nylon (PA)
Nylon materials are widely used in mechanically demanding high-temperature applications.
Depending on the specific PA family and reinforcement, Nylon can provide:
- High strength
- Good fatigue resistance
- Wear resistance
- Heat capability
- Structural performance
Glass-filled Nylon is especially common in:
- Automotive under-hood parts
- Electrical connectors
- Structural brackets
- Mechanical components
- Industrial equipment
Moisture absorption remains an important consideration because it can influence dimensions and mechanical properties.
Different Nylon families and reinforcement levels should therefore be treated as distinct engineering materials rather than one single category.
PPS
PPS is frequently selected when engineers need a combination of:
- High heat resistance
- Chemical resistance
- Dimensional stability
- Low moisture absorption
- Electrical performance
Typical applications include:
- Pump components
- Valve parts
- Sensors
- Automotive fluid systems
- Electrical components
- Industrial equipment
PPS is particularly useful when components must maintain dimensions while exposed to heat and chemicals.
Its limitations include higher material cost and more demanding molding conditions compared with standard engineering plastics.
PEI
PEI is an amorphous high-performance thermoplastic used when engineers require:
- High heat resistance
- High stiffness
- Dimensional stability
- Electrical insulation
- Flame resistance
- Low smoke performance
AccuMolds' current PEI Guide highlights these properties for aerospace interiors, electrical components, automotive and EV systems, medical equipment, and industrial applications. It also notes that PEI requires higher processing temperatures, careful drying, mold-temperature control, gate design, and stress management.
PEI can be especially attractive when high-temperature performance must be combined with precision dimensions or electrical properties.
PEEK
PEEK is typically reserved for more demanding applications where high temperature must coexist with:
- Chemical exposure
- Wear
- High mechanical loads
- Long-term reliability
- Dimensional stability
Typical applications include:
- Aerospace components
- Semiconductor equipment
- High-temperature valves
- Bearings
- Medical components
- Oil and gas equipment
- Industrial processing systems
PEEK provides exceptional performance, but its resin cost and processing requirements are significantly higher than those of conventional engineering plastics.
For this reason, PEEK should generally be selected when the application genuinely requires its performance rather than simply as a safety margin.
High-Temperature Materials: General Comparison
| Material | Key Strength | Typical Limitation |
| PC | Impact + heat + transparency | Lower extreme-temperature capability |
| Nylon | Strength + fatigue + heat | Moisture absorption |
| PPS | Heat + chemicals + dimensional stability | More brittle in some applications |
| PEI | Heat + stiffness + flame/electrical performance | High processing demands |
| PEEK | Extreme thermal + chemical + mechanical performance | Very high cost |
This table should be used only as a screening tool.
The final choice must be based on a specific commercial resin grade and actual application conditions.
Reinforced Grades for High-Temperature Applications
Reinforcement can significantly change material behavior.
Common options include:
- Glass-filled Nylon
- Glass-filled PPS
- Glass-filled PEI
- Carbon-fiber-reinforced PEEK
Reinforcement may improve:
- Stiffness
- Strength
- Creep resistance
- Dimensional stability
- Thermal expansion control
However, it can also introduce:
- Higher tool wear
- Fiber orientation effects
- Anisotropic shrinkage
- Warpage
- Reduced surface quality
- More demanding gate design
For precision components, flow direction and fiber orientation should be considered during DFM.
Injection Molding Considerations
As material temperature capability increases, molding requirements generally become more demanding.
Important factors include:
Material Drying
Moisture-sensitive polymers such as Nylon, PC, PEI, and some high-performance grades require controlled drying before molding.
Melt Temperature
Higher-performance polymers typically require higher melt temperatures and suitable molding machines.
Mold Temperature
High mold temperatures may be necessary to achieve proper flow, surface replication, crystallinity, weld-line strength, and dimensional stability.
Residence Time
Excessive time at elevated melt temperature can cause degradation or discoloration.
Tooling
High-temperature and reinforced materials may require:
- Hardened steels
- Wear-resistant inserts
- High-temperature seals
- Suitable hot-runner systems
- Improved thermal control
AccuMolds' PEI guidance specifically notes that high processing temperatures and reinforced grades can impose additional requirements on mold steel, inserts, cooling, and tooling components.
Do Not Select Materials Based on Temperature Alone
The material with the highest heat resistance is not automatically the best option.
Engineers should also evaluate:
- Impact resistance
- Chemical resistance
- Wear
- Moisture
- Flame requirements
- Electrical performance
- Dimensional tolerances
- Production volume
- Material cost
- Processing cost
For example, selecting PEEK for a component that PEI or PPS can reliably support may unnecessarily increase manufacturing cost.
Conversely, selecting a lower-cost material too close to its thermal limit can create creep, warpage, premature failure, or assembly problems.
The goal is to select the material that provides sufficient engineering margin without unnecessary performance or cost.
A Practical High-Temperature Material Selection Process
A useful workflow is:
1. Define continuous and peak temperatures
Separate normal operating temperature from temporary spikes.
2. Define mechanical load
Determine whether the component is structural, loaded, or subject to creep.
3. Identify environmental exposure
Include chemicals, moisture, UV, cleaning, and thermal cycling.
4. Define dimensional requirements
Identify critical tolerances, datums, and mating features.
5. Screen material families
Compare PC, Nylon, PPS, PEI, PEEK, and relevant specialty grades.
6. Select the specific grade
Review reinforcement, additives, certifications, and supplier data.
7. Perform DFM and process review
Confirm wall thickness, flow length, gate design, cooling, tooling, and machine capability.
8. Prototype and validate
Test the molded part under representative temperature, load, and environmental conditions.
This process is more reliable than selecting a resin from one temperature value on a datasheet.
Need Engineering Support?
Selecting a high-temperature plastic requires balancing thermal performance with mechanical loads, chemical exposure, dimensional stability, molding requirements, and total manufacturing cost.
AccuMolds can help evaluate high-temperature material options together with your part geometry, wall thickness, tolerances, gate strategy, tooling requirements, expected operating environment, and production volume.
Our engineering support covers material selection, DFM analysis, mold development, injection molding, inspection, and scalable production.
Send us your 2D or 3D CAD files together with operating temperatures, material requirements, quantities, tolerances, chemical exposure, surface requirements, and application information for project evaluation.
