What is engineering plastic?
Engineering plastics - also called construction plastics - are polymers developed to carry load, take heat, resist chemicals and hold their dimensions over time. Unlike packaging plastic, they are not made to be as cheap as possible, but to solve a specific technical job.
Common properties of engineering plastics are high stiffness, low friction, good chemical resistance, low weight compared with metal and the option to machine them with cutting tools. That makes them a cost effective alternative to steel, aluminum and brass in many mechanical applications.
If you want the longer reasoning, there is a separate guide on what engineering plastic is and when it beats metal, and one on the plastic families and what separates them.
The right engineering plastic can cut weight, noise and maintenance needs while it takes chemicals and moisture better than many metals.
Material guide
Our material guide goes through the most common engineering plastics. Each page explains what the material does, what it takes, which formats are in stock and how it is machined. Start here if you are choosing between POM and PA6, for example, or wondering what PEEK handles that other plastics do not.
Materials in the guide
Want to compare several materials? Use the material comparator or read Plastics guide for step by step guidance.
Technical data and datasheets
On each product page the technical data for that specific product is shown. There you can see properties, dimensions and machining recommendations, and generate the datasheet you need in the format that suits you. It is the same data that our material guides are built on, broken down to individual product level.
How to read a typical datasheet:
- Density - used to work out weight and price per volume.
- Yield strength and tensile modulus - tell you how much the material takes and how stiff it is.
- Maximum service temperature - go above it and the strength drops fast.
- Chemical resistance - always check it against your own environment; general tables are guidance only.
- ISO standard - states the conditions under which the value was measured.
Machining guide
Plastic is not machined like metal. Here is a short summary of the main points:
- Use sharp cutting edges and moderate feed to avoid melting and cracking.
- Cooling matters, but water cooling can stress some materials - check the recommendation.
- Keep an eye on thermal expansion when the fits are tight.
- On bonding: not all plastics glue equally well; some need special methods or surface treatment.
Read our full machining guide for sawing, milling, turning, drilling, tapping and bonding of different plastics.
Chemical resistance
Choosing a material that takes the liquid or gas the part will work in is critical. General resistance tables are a good start, but factors such as temperature, concentration, mechanical load and exposure time affect the result. When it is critical, ask for a specific test or contact us for advice.
A few rules of thumb:
- Fluoropolymers (PTFE, PVDF, FEP, PFA) take most chemicals and high temperatures.
- PE and PP have good resistance to acids, bases and solvents at low temperatures.
- PA is sensitive to strong acids and high pH, but takes many oils and solvents.
- PC and PMMA are sensitive to certain solvents and alkaline cleaning agents.
The rules of thumb rarely take you all the way. Our guide to chemical resistance goes through how to read a resistance table properly, and why stress cracking is the most common damage rather than dissolution.
Safety data sheets (MSDS/SDS)
Safety data sheets are available per product on each product page. There you find information on handling, storage, spill measures, fire risks and health hazards. If you need a specific data sheet for a product you are looking at, contact us and we will help you.
Tolerances
Plastic moves more than metal. A drawing that works in steel can give a press fit at 25 °C and play at 5 °C in plastic, because of thermal expansion, moisture pickup and relaxation under load. Our guide to tolerances in plastic goes through the main differences from the classic workshop handbooks.
Glossary and abbreviations
In our glossary we explain plastics terms in plain language, and in the material guides you find abbreviations such as PA, POM, PTFE, PEEK and many more explained.
Common questions
The answers to the most common questions about material choice, dimensions, delivery times, cutting and returns are on our FAQ page.