Thermoforming Applications

Blends of PC, ABS, and MMBS are useful to form articles with good impact and low gloss. The articles produced are useful as automotive components, bottles, and tool housings. A mixture of randomly branched carbonate polymers and linear carbonate polymers has been suggested (19). MMBS acts also as a melt strength enhancing agent. 

Chlorinated vinyl chloride-based compositions composed from chlorinated poly(ethylene) and MMBS are suitable for injection molding products with good heat resistance, impact strength, mold-ability, and surface properties (20). 

The addition of small amounts of methyl or phenyl poly(silox-ane)s to blends of styrene/MA copolymers and MMBS copolymers enhances greatly the impact strength without having adverse influence on the heat resistance and surface luster (21). 

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Polyethylene terephthalate) (PET) has become a major synthetic polymer during the past forty years. Significant commercial markets [1] have been developed for its application in textile and industrial fibers, films, and foamed articles, containers for carbonated beverages, water and other liquids, and thermoformed applications (e.g. dual ovenable containers). 

Finally, another equibiaxial deformation test is carried out by blowing a bubble and measuring the pressure required to blow the bubble and the size of the bubble during the test, as schematically depicted in Fig. 2.52. This test has been successfully used to measure extensional properties of polymer membranes for blow molding and thermoforming applications. Here, a sheet is clamped between two plates with circular holes and a pressure differential is introduced to deform it. The pressure applied and deformation of the sheet are monitored over time and related to extensional properties of the material. 

Clear extrusion sheet grades are designed for extrusion and thermoforming applications, and like other NatureWorks PLA polymers, use conventional processing techniques and equipment. Potential uses include dairy containers, food service ware, transparent food containers, blister packs, and cold drink cups. 

Thermoforming For thermoforming applications, Mater-Bi is being used to manufacture nontransparent, hard, thermoformed trays for packaging fresh food. 

In 2003, Ex-Tech became the first company in North America to introduce Nature Works PLA sheets for thermoforming applications. The material complies with FDA and European requirements for food packaging. 

Since PVC is known to be quite miscible with PMMA (miscibility with an LCST behavior) [Jager et al., 1983] and is also low in cost, some blends of PVC and PMMA have been used in sheet extrusion and thermoforming applications. However, the acrylic PVC compositions commercially used are invariably contain an acrylic coreshell rubber (PMMA-g-n-BuA or MBS type) to get high toughness), with some PMMA, to reduce the cost/impact performance balance. The role of PVC in these blends is to reduce cost and impart some degree of flame-retardancy. The acrylics definitely help in the processability of PVC. These blends have already been discussed under PVC heading. 

PET is a thermoplastic polymer resin of the polyester family. PET is used in synthetic fibers beverage, food and other liquid containers thermoforming applications and engineering resins often in combination with glass fiber. 

There are methods for estimating the pressures necessary for forming and the optimum temperatures. However, these techniques are based on constant strain rates and constant temperatures, neither of which exists in real thermoforming applications. For that reason, the final processing parameters are usually determined by experimentation. 

These types of films are mainly used as primary sheets for thermoforming applications. 

Film and sheet are the major forms in which PE is used, including shrink/stretch film, food packaging, pouches, and blown-film bags and liners. In North America, PE is by far the most-used film/sheet plastic material followed by PP. For shrink/stretch film in the United States, for example, over 75% is LDPE, rather than PVC. PE film and sheet also sees significant use in industrial thermoforming applications, as does PP for thermoformed packaging [2-19, 2-20]. 

Howery MF (1997) Material selection for thermoforming applications. Annual Technical Conference Proceedings (ANTEC)... 

The commercial PMMA-based acrylic resins are rigid, amorphous polymers (Tg s ranging from 85 °C to 105 °C) particularly noted for their exceptional clarity and UV resistance. They are therefore widely used for glazing, extruded sheet and thermoforming applications, as well as in several molding applications in which these properties are well utilized. 

Since PVC is known to be quite miscible with PMMA (miscibility with an LCST behavior) (Jager et al. 1983) and is also low in cost, some blends of PVC and PMMA have been used in sheet extrusion and thermoforming applications. 

There is continuing growth of nucleated PP, particularly in the blow molding and extrusion markets. CPET continues to expand in thermoforming applications, and PET molding compounds continue to pen-... 

Rotational molding or twin-sheet thermoforming (application dependent)... 

Polyallomer is used for blow-molded bottles, wire coating, film, sheet and pipe extrusion, and thermoforming applications. Applications also include automotive... 

Table 6.20 Commercial grades of polyethylene for thermoforming applications.

The analysed polyolefin is a general purpose i-PP called i-PP homopolymer Moplen HP450J which is produced by Lyondell-Basell. Moplen HP540J is a nucleated homopolymer for extrusion and thermoforming applications. The neat material exhibits good stiffness and optical transparency, and is thus adopted for fruit baskets, trays, transparent drinking cups and containers. The material properties for Moplen HP540J are reported in Table 6.1. 

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