Stretch blow molding examples

Figure 6.1 Examples of extrusion, injection, and stretch blow molding techniques...

Technology to successfully produce multilayer injection blow molded bottles is much newer than that to produce multilayer extrusion blow molded bottles. Heinz Inc. s ketchup bottle was the first U.S. example (Fig. 12.22). The use of PET bottles made by coinjection blow molding has grown rapidly. As is the case for coextrusion blow molding, the key is production of the parison. Once the multilayer parison is produced, the remainder of the process is essentially the same as for single layer materials. Even stretch blow molding can be used. 

One development for coinjection equipment was the inclusion of separate hot-runner temperature control systems for the different resins, for example, in order to allow an EVOH core layer to be processed at a temperature 70 C lower than the PET skin layers. Another development was the use of computer simulation to design tooling that manipulates the barrier resin distribution to fortify critical areas such as wall sections. Both wide mouth and narrow neck coinjection stretch blow molded bottles are available. 

Injection vs. extrusion/blow-molding For clarity, processmg factors go hand-in-hand with the choice of a clarifier. Relatively thick-walled, injection-molded cPP homopolymer or random copolymer parts have hmits on the clarity they can achieve, perhaps down to 7%-10% haze. Only thin extruded or injection-stretch blow-molded (ISBM) cPP may achieve lower haze levels (l%-2%) that allow it to compete with PET. For one-stage ISBM of random copolymer PP, for example, newer clarifiers may work better than sorbitol-based agents... 

Plastic users have made a market for recycled plastic by naodifying machinery for two and three layer coextrusion heads. Coextrusion is a method applied primarily to HDPE and sandwiches a recycled plastic layer in between virgin resins. It is used because it produces a uniform appearance of bottle exteriors and a market safe container. Cotnjection stretch blow molding of PET is another febrication method being looked at. It is capable of producing multi-layer botdes with recycle PET sandwiched in between. Examples of... 

This integral carrying handle was issued in a French patent granted to an Italian company. This patent incorporates a traditional jug handle above the blown portion of an injection blow-molded container, as for example a pitcher. The handle is molded as part of the preform and is undisturbed when the container is blown. A direct extrapolation to stretch blow-molding technology would incorporate the jug handle immediately below the neck finish of an injection-molded preform. It would be necessary to mold such a preform in a split mold that suits itself to production on certain rotary-type injection stretch blow equipment. 

Milling is used when intensive cooling by drilling channels is not achievable, for example, in the shoulder portion of blown bottles, recessed bottom parts, neck rings, and in preform molds for stretch blow molding. 

In order to generate a better balance of mechanical properties it is necessary to create biaxial orientation in the part. Stretch blow molding is used to accomplish this. In essence the parison is stretched along the axial direction before being inflated. Biaxial orientation is specifically required in large containers for fluids. For example, bottles for carbonated beverages are typically processed by means of stretch blow molding. 

Hgure 8.11 Example of stretched injection blow molding using a rod (left) and example of stretched injection blow molding by gripping and stretching the preform... 

The injection molding with rotation (MWR) is an example of processing at lower temperatures, pressure, etc. It is also called injection spin molding or injection stretched molding. This BM process combines injection molding and IBM, as performed in IBM reviewed, except it has the additional step of with melt orientation (Dow patent). The equipment used is what is commercially available for IM except the mold is modified so that either the core pin or outside cavity rotates. The rotated melt on its preform pin is transferred to a blow mold. The end product can come directly from the I MM mold or be a result of two-stage fabrication malting a parison and BM the parison.164... 

Example of stretched injection blow molding using a... 

Biaxial extension is another example of a nonviscometric deformation. It can be achieved, for example, by simultaneously stretching a sheet of material in its length and width directions or by blowing up a balloon. It plays a prominent role in the blow-molding process (Section 19.4). Show the components of the deviatoric stress and the rate-of-strain tensors for the biaxial extension of an incompressible material. What material function(s) would be needed to describe e equilibrium biaxial extension of a homogeneous fluid ... 

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