Plastic Properties Guide for Material Selection

Compare engineering plastics by thermal, mechanical, chemical, electrical and dimensional performance to identify materials that fit your application. Use this page as a properties navigation hub, then review the grade-specific data on each material page or datasheet.

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At a Glance

Thermal

Mechanical

Chemical

Electrical

Dimensional

By Application

Materials

Compare at a glance

Engineering Plastic Properties at a Glance

A side-by-side view of the five high-performance families Great Plastics supplies. Use these ranges for initial screening; confirm the specific grade before locking a specification.

Property PEEK PPS PEI PI PAI
Continuous service temperature ~250 °C ~220 °C ~170–180 °C ~260 °C ~250 °C
Density (g/cm³) 1.30–1.51 ~1.35–1.43 ~1.27 ~1.43 ~1.45
Tensile strength 90–100 MPa (unfilled; higher with fillers) ~75 MPa 90–105 MPa Grade dependent ~80 MPa (grades higher)
Moisture absorption Low Very low Low–moderate Low Moderate–high*
Chemical resistance Excellent Excellent Good–excellent Excellent Fair–good*
Wear resistance Excellent Good Good Excellent Excellent
Dimensional stability High High High High High at temperature*
Electrical insulation Excellent Excellent Excellent Excellent Excellent

*Values shown are typical reference ranges and may vary by grade.

Not sure which family fits? Use the material selection tool or review each material page below.

Thermal

Thermal Properties of Engineering Plastics

Temperature is often one of the first factors to consider when selecting an engineering plastic. Start with the required continuous service temperature, then consider short-term exposure, glass transition temperature, melting behaviour and thermal expansion based on the actual operating conditions.

Continuous Service Temperature

The continuous temperature a material can typically withstand during prolonged service. Actual limits depend on load, geometry, environment and grade. Sustained heat is usually the first gate in selection.

PEEK ~250 °C PPS ~220 °C PEI ~170–180 °C PI ~260 °C PAI ~250 °C

Glass Transition Temperature (Tg)

Tg indicates the temperature range where an amorphous polymer undergoes a major change in stiffness and molecular mobility. It is most relevant for amorphous grades such as PEI, PAI and PI, and for the amorphous phase of semi-crystalline PEEK.

PEEK PEI PI PAI

Above Tg, modulus drops and creep accelerates — keep design limits below Tg where possible.

Melting Temperature

Melting applies to semi-crystalline thermoplastics such as PEEK (Tm ~334–343 °C) and PPS (Tm ~280 °C). Amorphous materials such as PEI, PI and PAI have no sharp melting point.

PEEK PPS

Melting temperature should not be treated as the allowable operating temperature — continuous service limits are far lower and depend on load and environment.

Thermal Expansion (CTE)

Low coefficient of thermal expansion (CTE) means the part holds its dimensions as temperature changes. This matters wherever a machined part mates with metal or must hold a tolerance across temperature.

PEEK PPS low CTE PAI low CTE

Fillers (glass, carbon, graphite) reduce CTE and improve dimensional control in machined parts.

Mechanical

Mechanical Properties

Focus on the mechanical properties that engineers typically consider during material selection rather than a long list of isolated numbers. Each property below is linked to its practical importance and the materials worth reviewing for that requirement.

Property Why it matters Materials to review
Tensile strength Load-bearing capability and resistance to breakage under pull. PEEK, PEI, PPS, PAI
Tensile / flexural modulus Stiffness and resistance to deflection under load. PEEK, PEI, PAI
Flexural strength Bending and structural support for beams, housings and brackets. PEEK, PPS, PAI
Compressive strength Loaded supports, fixtures, seats and parts under compression. PEEK, PAI, PPS
Creep resistance Long-term dimensional stability under sustained load. PEEK, PAI, PI
Wear resistance Bushings, seals, sliding components and moving surfaces. PEEK, PAI, PI

Chemical

Chemical Resistance

Chemical resistance is not a single pass-or-fail rating. Performance depends on the specific chemical, concentration, temperature, exposure time, mechanical stress and material grade or filler system.

What Affects Chemical Resistance

  • Chemical type and concentration
  • Exposure temperature
  • Exposure time and cycling
  • Mechanical stress and stress cracking
  • Material grade and filler system
  • Part geometry and surface condition

Start Here

Identify the chemical and the worst-case operating conditions first, then shortlist materials for further evaluation. The table below provides a starting point by mapping common chemical environments to material families worth investigating.

Chemical compatibility should be confirmed for the actual chemical, concentration, temperature, exposure time and mechanical conditions before production.

Environment Materials to investigate
Acids PEEK, PPS, PTFE, PVDF
Alkalis PEEK, PPS, PTFE
Solvents PEEK, PPS, PTFE
High-purity process fluids PEEK, PPS, PTFE, PVDF
Aggressive chemical exposure PTFE, PVDF, PEEK
Hot water / steam PEEK (hydrolysis-resistant), PPS

Chemical compatibility is only one part of material selection. For machined components, also consider dimensional stability, creep, wear, thermal expansion and the effect of the chemical environment on the complete component.

Electrical

Electrical Properties

Electrical requirements generally fall into two areas: electrical insulation and static control. Identify whether the component needs to prevent current flow, control charge accumulation, or meet specific electrical performance requirements before selecting a material grade.

Parameter What it indicates Notable materials
Dielectric strength Ability to withstand voltage without breakdown. PEI, PEEK, PPS, PI
Volume / surface resistivity Resistance to electrical conduction and leakage through or across the material. PEI, PEEK, PPS, PI
Dielectric Constant Capacitance and signal behaviour. PEI, PEEK, PPS
Dissipation factor Energy loss, especially at high frequency. PEEK, PEI
ESD/conductive grades Static control for electronics and clean environments. PEEK, PEI, PPS conductive / ESD grades

Electrical Insulation

For components that must block current — insulators, bobbins, terminals and high-voltage parts — look for high dielectric strength and high resistivity that hold up at operating temperature.

PEEK PEI PI PPS

Above Tg, modulus drops and creep accelerates — keep design limits below Tg where possible.

Static Dissipation & ESD

For electronics, semiconductors and clean rooms, conductive or ESD grades of a material control charge accumulation. Match the surface resistivity class to your static-control requirement.

PEEK conductive PPS conductive PEI conductive

Filled grades (carbon, carbon-fibre) change electrical and mechanical behaviour together — review the full datasheet before selecting.

Dimensional

Dimensional Stability

For close-tolerance, CNC-machined components, dimensional stability can be more important than tensile strength alone. A material that changes size or shape with moisture, temperature or sustained load can make it difficult to maintain tight tolerances, even when its mechanical strength is high.

What drives movement

  • Water absorption and humidity
  • Thermal expansion (CTE)
  • Creep and stress relaxation under load
  • Machining-induced stress and movement

A material with high strength is not necessarily the best choice for a close-tolerance machined component.

Dimensional stability in practice

PEEK, PPS and PEI keep low moisture absorption and stable dimensions across temperature and humidity, making them dependable for precision machined parts.

PAI holds excellent dimensional stability at temperature, but is more hygroscopic: dry PAI parts before installation or high-temperature service to avoid thermal-shock distortion.

By application

Which Property Matters for Your Application?

Start with the operating requirements rather than the material name. Identify the condition that is most likely to limit your part, review the properties that affect it, and then compare the materials that fit those requirements.

High Temperature

Look at

Continuous service temperature → creep → stiffness retention → thermal expansion

PEEK PPS PEI PI PAI

Chemical Exposure

Look at

Chemical → concentration → temperature → exposure time

PEEK PPS

Wear & Friction

Look at

PV / load → speed → mating surface → lubrication

PEEK PI PAI

Electrical Insulation

Look at

Dielectric strength → resistivity → temperature → moisture

PEEK PPS PEI PI

Dimensional Stability

Look at

Moisture → CTE → creep → machining stress

PEEK PPS PEI PAI

Precision Machining

Look at

CTE → moisture → internal stress → geometry → tolerance

PEEK PPS PEI PAI

For design and machining guidance on these materials, see the design guide and CNC plastic machining pages.

materials

Engineering Plastic Materials

Each family has a dedicated material page with deeper properties, grades and applications. Open the page that matches your requirement.

PEEK

Heat resistance, wear resistance, chemical resistance and dimensional stability.

PPS

Chemical resistance, low moisture absorption and dimensional stability.

PEI

Heat resistance, stiffness, electrical insulation and flame performance.

PI

High-temperature stability, wear resistance and electrical insulation.

PAI

High strength, stiffness, wear resistance and high-temperature performance.

Datasheets

Need Grade-Specific Data?

Typical property ranges are useful for initial material screening. For purchasing and engineering decisions, review the specific grade, test method, filler system and processing condition on the datasheets page.

Ready to Select a Material?

Use the selection tool when you are still comparing materials.

When you are ready to source a part, send the drawing and operating conditions for review.

FAQ

Material Properties FAQ

Start with the operating constraints that matter most — continuous temperature, chemical exposure, load, wear, electrical need, and required tolerance. Use the at-a-glance table for an initial screen, then confirm the specific grade on the material page or datasheet.

Properties vary by grade, filler content, test method, processing condition and application environment. Ranges describe typical behaviour; the exact value for your part depends on the grade you select.

Continuous service temperature is the sustained operating limit for a loaded part; melting temperature is a physical transition of semi-crystalline polymers and is not an allowable operating temperature. Actual service limits are far lower and depend on load and environment.

PEEK, PPS, PTFE and PVDF offer the broadest chemical resistance across acid, alkali and solvent environments. Confirm compatibility against your specific chemical, concentration and temperature before production.

Send a drawing or CAD file, your material target, operating conditions, quantity, critical tolerances and inspection requirements. Great Plastics reviews material, product form, machining route and RFQ details before quoting.