Thermoforming multilayer

Thermoformable multilayer laminates are known in the vehicular arts as providing acceptable surface preparation when applied to various automobile components without distorting the quality of the underlying surface or substrate. Multilayer laminates have traditionally been formed in a variety of methods, including (37) ... 

Thermoform able sheet may be mono- or multilayer with the latter produced by lamination or coextmsion. Multilayers are employed to incorporate high oxygen-barrier materials between stmctural or high water-vapor barrier plastics. Both ethylene vinyl alcohol copolymers and poly(vinyhdene chloride) (less often) are used as high oxygen-barrier interior layers with polystyrene or polypropylene as the stmctural layers, and polyolefin on the exterior for sealing. 

Thermoforming of extmded sheet is achieved by warming the sheet to its glass-transition poiat and coUapsiag it over a mold shape (21). The coUapse can be effected by vacuum suction or pressures appHed on the sheet above the mold. This technique is used to make trays and profiled advertisiag signs. Both single- and multilayer sheets can be used. 

Films, sheets and plates for packaging and thermoforming, barrier layers of multilayer films... 

Another route to protect polymers from oxygen, light and UV is to encapsulate the part with a continuous film of another, more-resistant polymer to provide a barrier to oxygen. This technology is also used for decoration of plastic parts (in mould decoration or IMD, painting, multilayer sheets for thermoforming. ..). There is no protection against heat. 

GMT can be preferred to SMC for small or medium runs in the automotive industry. For example, German fire-fighting equipment manufacturer Rosenbauer is using ther-moformed sheet (multilayer ABS/PMMA) instead of hand-laid GRP. The cost of a body panel can be cut by 30% if the number of parts - in Three-digit quantities - is sufficient to justify the investment in thermoforming tools. 

Chicago, II., 29th Aug-2nd Sept.l993,p.403-6. 6A MULTILAYER EXTRUSION DIE GEOMETRY FOR THERMOFORMED POLYPROPYLENE FOAM SHEETS AND BIAXIALLY ORIENTED FOAM FILMS Raukola J Savolainen A Tampere,University of Technology (TAPPI)... 

Multilayered materials can be readily formed using thermoforming including food packaging that may involve inclusion of layers of ethylene-vinyl alcohol copolymers, PS, polyolefins, and/or copolymers of vinylene dichloride and vinyl chloride. Microwavable food trays from (crystallized) PET are manufactured using thermoforming. 

Shaping of material variable Coextrusion/thermoforming of multilayers, blow molding... 

The article has 3 layers A-B-A. The layer B is so designed that it has heat distortion temperature higher by at least 3°C than layer A (in the example given in the table, heat distortion temperatures for A and B are 68 and 83°C, respectively). The multilayer laminate is produced by coextrusion and shaped by thermoforming. 

Film Applications Grilon CF 6S is particularly suitable for boil-in-bag applications. Grilon CR 9 is suitable for multilayer food packaging films for dry, nonfatty food packaging. Grilon CR 9 HV is a superior product for extreme-draw, thermoforming fiims.P i... 

Eurthermore, multilayer and fibre-reinforced composites as well as foamed semi-finished products (e.g. PVC slush skin for dashboards) are used in thermoforming. 

Thermoforming normally involves trimming of the final product, which leads to a significant amount of recyclable material. This material is reused for the extrusion of semi-finished products. Eor thick sheets it is common to extrude multilayer materials with a core from regrind, while the top layer is virgin in order to obtain a good surface quality. 

Multilayer materials specially developed for longer best before dates and better barrier properties can be processed by means of thermoforming in one... 

Unoriented multilayer films are useful in a number of end-uses, including thermoforming processes, forming shaped articles, such as hottles, or they can be stretched to form oriented flat films. For example, a film having a thickness of 10 mil is suitable for thermoforming into cups having a wall thickness of 1 mil. Trays having a thickness of 10 mil can he obtained from a 100 mil film. 

Most thermoforming operations produce a relatively large amount of scrap in each cycle. Scrap rates of 30% are not unusual. If the sheet is produced in one location and thermoformed in another, or if the material is multilayer, reuse of scrap is more difficult than in extrusion blow molding. 

Various types of multilayer dies, such as the TRD, have successfully produced coextruded LCP-thermoplastic film, sheet, and thermoformed articles. These products are expected to penetrate the high barrier plastics market valued at more than 700 million per year for a variety of food, beverage, medical, and industrial packaging applications. Because of their very low permeability to oxygen and water vapor combined with high temperature and chemical resistance, coextruded LCP films should find applications in this market. The process for coextruded LCP thermoplastic multilayers overcomes the key problems previously limiting LCP coextrusion ... 

Ashler, S A, Thermoforming of Single and Multilayer Laminates, Elsevier, 2014, pp. 193-209. 

The thermoforming process is the method for annealing a sheet of thermoplastic resin to manufacture the final product by vacuum or air pressure, as shown in Fig. 6.9. It has these advantages The cost of equipment is inexpensive, the processing of multilayer sheets can be readily achieved, and the production of thin products is possible. The disadvantages of this process are that the procedure for preparing sheets is necessary, the selection of available plastic material is limited, and manufacturing with accurate dimensions is difficult. 

Wang, P., HamUa, N., Boisse, P., 2013. Thermoforming simulation of multilayer composites with continuous fibres and thermoplastic matrix. Compos. Part B 52, 127-136. 

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