3.4 Polymers for Enclosures

Whereas metal pressings are normally suitable for enclosures in category 4, with cast aluminium providing better protection, plastics will often perform better, with the preferred polymers in the categories 5 and 6 tending to be PC and PS. For the greatest protection lids should be glued or attached using a sealant. However, where access to the interior of the enclosure is needed, more often a click or press fit of the lid may suffice. If bolts are used then grommets should be employed to give a better seal. In the case of IP54 sealing or greater it is usually necessary to employ a compressible seal between the lid and the body of the enclosure. Furthermore it is said that machine applied polymer seals perform better than gasket types. To achieve IP65 and higher protection it is necessary for the lid fixing screws to be situated outside the area enclosed by the lid seal. Ineffective sealing may give rise to component short circuits, corrosion and affect operational reliability. If there are significant ambient temperature variations then condensation may become a problem.

Rolec offers an IP65 rated weather resistant polyTOP-Ex range which is manufactured from glass fibre reinforced polyester. This range is corrosion proof because the metal inserts are manufactured from stainless steel. The lid fixings can be specified as slot head or allen head screws. The polyKOM-Ex range features IP66 ingress protection and is also manufactured from glass fibre reinforced polyester with stainless steel metal inserts and...