The ABC of plastic materials — from polyethylene to carbon fibre composite
Thermoplastic, thermoset, and common plastic types
Plastic is not one material but a large family of materials with very different properties. Knowing the plastic types is the prerequisite for choosing the right processing method, for getting a joint to hold, and for knowing how the material behaves under heat and load.
§Thermoplastic and thermoset
The most important distinction is between thermoplastic and thermoset. Thermoplastic softens when heated and becomes hard again when it cools — therefore it can be reshaped and welded. Thermoset hardens by chemical reaction and cannot be melted again; if heated strongly it breaks down instead of softening. This difference determines among other things whether the material can be welded.
§Common thermoplastics
- 01PE (polyethylene) — tough and chemical-resistant, used for pipes, tanks and foils
- 02PP (polypropylene) — stiff and heat-resistant, used for pipes, containers and equipment in chemical environments
- 03PVC — rigid or plasticized, used for pipes, profiles, and coatings
- 04PVDF and other technical plastics — used where special chemical or thermal resistance is required
§Properties that matter in the work.
Plastic companies range from small specialized factories to large international manufacturers. Depending on what the company does you could end up in very different corners of the industry.
§Identification of the material
Before you process or weld plastic, you must know what it is. The material may be marked on the piece or appear in packing slips and datasheets. If two types are confused, a weld can be weak, or the material can behave differently than expected. If the material is unknown, it must be clarified before work continues — you don't guess.
§Why material knowledge is linked to safety
Material knowledge is not just a question of quality. When plastic is heated by welding or processing smoke and fumes can develop and different plastic types behave differently. Therefore good ventilation and knowledge of the material go together — you must know what you are working with both for the result's and for your own health's sake.