Molding processes multilayered structures

In order to obtain a uniform wall thickness for complex shaped containers, it is necessary to be able to control the thickness of the parison as it extrudes. Wall thickness control is achieved by varying the die gap as the parison is extruded. There are a variety of different arrangements for the blowing step of the process. These include the use of single dies with multiple molds (e.g., vertical rotary wheel), and multiple dies with multiple wheels. For some examples, refer to the illustrations in Figures 2 through 4. For enhanced barrier properties of multilayer structures, combinations of polymer materials are used, such as ... 

Fig. 5.35B). Their continued growth inward can lead to a layer of columnar structure. The number and extent of the layers depend upon the speciflc processing conditions. For example Bowman [157] identified five layers in acetal copolymers, but where the mold is thin there may be no core, and in a hot mold there may be no skin. Multilayered structures are also observed in... 

Multilayer fabrication is the simultaneous processing of two to up to at least seven plastics melt streams meeting in a die/mold to produce laminated or multilayer plastic products. Product performances gained are a combination of what each individual plastic provides with a potential of obtaining synergistic gains. Each ply of the laminated structure imparts a desired property such as impermeability or barrier/... 

---