Thermoforming cold forming

Conventional thermoforming of sheet and film is appHcable to the production of skylights, radomes, signs, curved wiadshields, prototype production of body parts for automobiles, skimohiles, boats, etc. Because BPA polycarbonate is malleable, it can be cold-formed like metal, and may be cold-roUed, stamped, or forged. 

Provided due care is taken with respect to predrying and to crazing tendencies, polycarbonates may also be thermoformed, used for fluidised bed coating and machined and cemented. Like metals, but unlike most thermoplastics, polycarbonates may be cold formed by punching and cold rolling. Cold rolling can in fact improve the impact resistance of the resin. 

Replacing PVC with PP allows compliance with environmental standards in some pharmaceutical markets. These materials are cold formed instead of being thermoformed. Such packages require more packaging materials than thermoplastic plastic films for the packaging of the same number and same size of tablets or capsules. 

This is an extension of the cold forming process. It uses thermoformed B-stage thermoset reinforced plastic (RP) skin to improve surface and other characteristics to a cold molded thermoplastic. The mold is closed and the fast, room temperature curing RP plastic system hardens. The finished product has the smooth TP-formed sheet. 

All the above processes can also be used in a form fill seal process with, for example, thermoforming and cold forming blister packs. Rommelag type bottle pack systems use an extrusion process where the container is formed by either blowing or vacuum (smaller sizes). Immediately after this, containers are filled, and the pack is sealed (welded) by using the residual heat in an extension to the main body of the container. 

Combined with polythene to give various thermoformed packs for cheese, bacon, etc. Also used as an outer ply for boil-inbag applications and as an outer ply in some cold formed blisters. 

In addition to catering for conventional thermoformed blisters using a plastic tray and a foil-based lid, most blister machine manufacturers now offer facilities to increase moisture protection, by use of either a tropicalised blister (by an additional foil over cover) or a cold formed, foil-based tray. Considerable competition is expected between these and similar options, where a high level of climatic protection is required. The other options include blisters in sachets and overwraps to cartons. Output speeds, climatic protections achieved, overall cost and patient/marketing preference, will influence the final pack choice. 

The expandable polystyrene beads may be used in a tabular blow-extrusion process (Figure 2.59) to produce polystyrene foam sheet, which can subsequently be formed into containers, such as egg cartons and cold-drink cups, by thermoforming techniques. 

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