WATER CONTENT OF PLASTICS

SUMMARY:

Depending on the group (elastomers and thermosets), plastics are exposed to moisture in different ways during production and processing. The difference is between free (surface) water and chemically or physically bound water. Mixing forms can also result.
Technical plastics such as polyamide, polyester or polycarbonate are hygroscopic and have to be dried before further processing. Bulk plastics, such as polyethylene and polypropylene, are normally not dried before processing, but they must meet defined limits, depending on the application, which are between 200 and 1500 ppm water.