Polycarbonate thermoforming

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. 

We routinely manufacture polycarbonate products by injection molding, blow molding, extrusion, and thermoforming. Injection molding is the most common processing technique. 

The following TPs are the main thermoforming materials processed high-impact and high-heat PS, HDPE, PP, PVC, ABS, CPET, PET, and PMMA. Other plastics of lesser usage are transparent styrene-butadiene block copolymers, acrylics, polycarbonates, cellulosics, thermoplastic elastomers (TPE), and ethylene-propylene thermoplastic vulcanizates. Coextruded structures of up to seven layers include barriers of EVAL, Saran, or nylon, with polyolefins, and/or styreneics for functional properties and decorative aesthetics at reasonable costs.239-241... 

Merlon [Bayer], TM for a polycarbonate resin. Rods, tubes, pipes, sheets, film extrusions, and special types may be produced by extrusion, thermoforming, injection, and blow moldings. 

Batch injection molding machine thermoplastics commodity resins, polyolefins (LDPE, HDPE, PP), styrenics (PS, PMMA. polycarbonates, ABS, PET), and engineered resins for higher impact strength. Continuous extruder thermoplastics. Casting PP fine film 10 to 50 pm cast film 100 to 400 pm thermoformable sheet 200 to 2500 pm. Film blow LDPE, HDPE, PP. Pug mill clay materials for bricks, tiles, and ceramics. 

Polycarbonate is being blended with ABS to lower the Vicat softening temperature and to make it more thermoformable (46). It is also blended with poly(butylene terephthalate) to increase stress-crack resistance. 

Polyetherimide (Ultem 1000, GEC) is a high performance engineering thermoplastic with high heat distortion temperature (> 200°C), high mechanical strength and inherent flame-retardancy characteristics. Recently blends of polyetherimide with polycarbonate have been commercially offered as thermoformable sheets and as molding compounds (Table 15.28). The primary reason for... 

An important factor with thermoforming is that the polymer should show a pronounced rubbery region on the temperature scale. For this reason, amorphous polymers such as PVC, PS, poly(methyl methacrylate) (PMMA), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), etc. are well suited for thermo forming. With semicrystalline polymers, the rubbery region is largely masked by the crystallinity (Fig. 23.19). With PE and polypropylene (PP), thermoforming is, therefore, a critical operation, in which the processing conditions should be very carefully controlled. 

One example of an innovative thermoformed product is the application of new semi-finished products to the thermoforming process, like an interior panel with ambient light for automotive or aviation applications (Fig. 2). The semi-finished product is made of polycarbonate with an electroluminescence layer on the back. In order to protect the electroluminescence layer, the panel is partly back injection molded with PC/ABS. 

The polymers used in thermoforming must be of fairly high relative molecular mass since the heated sheet must be form stable. The significant property is melt elasticity. The elastic effects are produced by entropy-elastic forces between physical cross-links (molecular entanglements). The polymers used include polystyrene, ABS, acrylics, polycarbonate, PVC, polypropylene, and linear potyethylene. 

Blends of PEI with polycarbonate (PC) form phase-separated morphologies (Chun et al. 1996). Nevertheless, some PEI/PC blends (Ultem LTX) exhibiting improved melt flow and toughness were commercialized in the 1990s, but now seemed to be discontinued. PEI blended with some PC is used as thermoformable sheets (Ultem 1668, Sabic) for aircraft interior applications, to meet the process-ability and the low flammability and low smoke generation requirements. 

Twin-sheet thermoforming. Twin-sheet thermoforming is generally used to produce large, flat, double-walled parts. Nearly all of the thermoplastics can, at least theoretically, be thermoformed. However, the bulk of parts made by this process are usually polystyrene or ABS. The high-est-temperature plastic thermoformed in any significant amount is polycarbonate. 

Thermoforming ABS, acrylic, cellulosics, polycarbonate, polyethylene, polypropylene, polystyrene, polysulfone, PVC, SAN... 

Low-volume production of hudding panels, automotive body panels, and hampers is thermoformed from engineering thermoplastics. ABS, polycarbonate, polycarhonate/ABS, polyamide, and polyesters are thermoformed into in-mold decorating films which are rohoticaUy placed into an injection molding mold. The substrate is back-molded onto the film. 

Polyarylates can be processed by most conventional melt processes, including injection molding, extrusion, blow molding, and thermoforming. Processing characteristics are similar to that of polycarbonate with the exception that higher melt temperatures are required. 

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