TWI Frequently asked questions
by Felicity Chipperfield
Hot plate welding is suitable for almost any thermoplastic material, but is most often used for softer, semi-crystalline thermoplastics such as PP and PE. Weld strengths approaching that of the parent materials can usually be obtained if correct welding procedures are followed.
However, in general, nylon materials should not be hot plate welded, for a number of reasons:
- the heated surface solidifies very rapidly, and so very short dwell times are required
- there are problems with the molten material sticking to the PTFE coated heater plate
- due to the hygroscopic nature of nylon (and the presence of contained water) the heated surface tends to bubble, lowering weld strength.
Dissimilar material having similar melting points and melt viscosities can be hot plate welded provided they are chemically compatible. A typical example is the automotive rear light cluster, where the PMMA (polymethylmethacrylate) lens is hot plate welded to the ABS (acrylonitrile butadiene styrene) housing.
