Moulding processes injection blow

Due consideration of these principles has made it possible to process unplasticised PVC by all the standard melt processes, including injection moulding and bottle blowing, a state of affairs hardly conceivable in the 1950s. 

Polystyrene and closely related thermoplasties such as the ABS polymers may be proeessed by sueh techniques as injection moulding, extrusion and blow moulding. Of less importance is the processing in latex and solution form and the... 

In Section 4.2.7 we considered the process of extrusion blow moulding which is used to produce hollow articles such as bottles. At that time it was mentioned that if molecular orientation can be introduced to the moulding then the properties are significantly improved. In recent years the process of injection blow moulding has been developed to achieve this objective. It is now very widely used for the manufacture of bottles for soft drinks. 

All the molten-state processing methods are usable, mainly extrusion, injection, blow moulding, co-extrusion, welding. 

ECTFE can be processed by conventional molten-state methods such as extrusion, injection, compression, transfer, rotational and blow-moulding processes. 

Injection and blow moulding are by far the most used of the moulding processes but compression is sometimes used for specific cases. 

Injection blow moulding, in which the parison is injected into a first mould and then blown in a second mould having the shape of the final recipient. This process is more expensive and the cycle time is a longer. The aspect and dimensional quality are better compared to extrusion blow moulding. 

Blow moulding is the most common process for making hollow articles such as bottles. There are two main types of blow moulding, injection blow moulding and extrusion blow moulding. 

Injection blow moulding is used for the production of hollow objects in large quantities. The main applications are botdes, jars and other containers. The Injection blow moulding process produces bottles of superior visual and dimensional quality compared to extrusion blow moulding. The process is ideal for both narrow and wide-mouthed containers and produces them fully finished with no flash. 

Injection blow moulding A blow moulding process in which the parison to be blown is formed by injection molding. 

Fig. 20.4 The injection stretch blow moulding process (ISBM).

Although both processes can produce reasonably good quality large containers, injection stretch blow moulding is more widely used for pharmaceutical containers. The first stage of moulding is basically as injection blow moulding. In the second... 

Both employ a preprinted transfer (up to six colours). In the in-mould process the transfer is placed within the mould prior to bottle blowing or injection moulding. During the moulding cycle the printed transfer becomes fused to the container. The printing can be produced by either screen or gravure and can be line or half tone. 

In PVC technology, acrylic-processing aids made from high molecular weight PMMA are used to improve the siuface finish in extruded profiles, film, sheet, blow mouldings and injection mouldings. The dose is typically between one and two phr. 

Clarifying additives enable PP to compete for applications that were previously captive to PET or polycarbonate, both of which cost more. PP supplier Borealis and Milliken have developed a two-stage injection stretch blow moulding process, used for still water bottles and juice containers, that allows the rapid manufacture of clear PP bottles at up to 1500 bottles per hour from each mould cavity, using Milliken s clarifiers. 

Cavities of different sizes and geometries can be incorporated into one mould, sometimes referred to as gang moulds or family moulds. This is possible because the moulding pressure in the cavities is produced by the gas pressure of the blowing agent within the melt and each i cavity is therefore effectively an independent entity. Separate nozzles, each with their own flow control valves, are used for each cavity. Alternatively, several moulds may be used instead of a family mould. Family moulds have been unsatisfactory for the component injection moulding process because of the difficulty of ensuring even flow to all cavities. However, recently... 

Although we do not have a case study to feature the injection blow-moulding process it is described briefly below, for interest and completeness. 

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