Stretch-blow moulding

Fig. 4.25 Extrusion stretch blow moulding Injection Stretch Blow Moulding...

Injection stretch blow moulding in which all the operations are performed on the same line. The preform is stretched with a stretch rod . Stretching improves the mechanical performances and allows the production of thinner walled bottles. 

By far the most important plastic is polyethylene terephthalate (PET). Bottles of this material are formed in a two-stage process. So-called pre-forms are made by injection moulding and, in a second process, are then stretch-blow-moulded to produce a bottle. PET has properties surprisingly like those of glass, but it does not have the same disadvantages of weight and brittleness. 

Development of markets for PLA injection stretch blow moulding applications. 

The main markets for PLA are thermoformed trays and containers for food packaging and food service applications. Other developing areas include films and labels, injection stretch blow moulded bottles and jars, specialty cards and fibres. 

The main types of NatureWorks PLA that are available for packaging applications include general purpose film grades, extrusion coating, extrusion and thermoforming grades and injection stretch blow moulding. 

PLA is available in grades suitable for manufacture of injection stretch blow moulded bottles. It is claimed these offer comparable organoleptic properties to glass and PET making it suitable for a variety of short shelf-life food and beverage bottling applications. 

Injection stretch blow moulding (ISBM) is used for the production of high quality and high clarity containers. PET is the most widely used polymer for injection stretch blow moulding of botdes. During the last two years, there has been a growing interest from brand owners and retailers in the use of PLA for manufacture of stretch blow moulded botdes for short shelf-life products such as mineral water and milk. 

Injection stretch blow moulded bottles and jars for short shelf-life applications that use cold-filling techniques such as still water, fresh juices, dairy beverages and edible oil. 

As PLA prices move closer to those of PET there may be a tendency for brand owners to switch from PET in favour of biodegradable polymers such as PLA for injection stretch blow moulded bottles, not only on cost grounds, but also because renewable packaging materials have marketing advantages for the consumer. 

PLA permits manufacture of varied and complex bottle shapes and sizes. Monolayer bottles of NatureWorks PLA can be formed on the same injection moulding/stretch blow moulding equipment used for PET, with no sacrifice in production rate. PET has some properties that PLA does not have and so NatureWorks is targeting applications where it has a competitive edge such as fresh food packaging and products that don t require sophisticated barriers such as water, milk and juice products. 

Alpha Packaging manufactures botdes and jars made from polyethylene terephthalate (PET) and high-density polyethylene (HDPE) for the pharmaceutical, nutritional and personal care markets. Technologies used include injection blow moulding, injection stretch blow moulding, and extrusion blow moulding. Alpha manufactures stock and custom containers in a variety of styles and colours. 

Alpha Packaging manufactures NatureWorks PLA bottles on stretch blow-moulding machines. Alpha states that PLA is ideal for oil-based products, as well as products with flavour and aroma attributes. The PLA resin is FDA-approved and suitable for food contact. It is used for dairy, juice and water bottles, as well as trays for deli meats, salads and single-serve meals. 

In the stretch blow moulding process, which is the most common, the extruded parison is initially blown undersized, and then stretched and blown to its final shape in a second mould. This produces biaxial molecular orientation of the container walls, which improves impact resistance, rigidity and clarity. However, permeability is reduced. 

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... 

In extrusion stretch blow moulding the first stage is similar to the first stage of extrusion blown, but the parison formed is conditioned to a specific temperature prior to stretching initially by a descending rod and then by compressed air (Figure 7.9). 

Figure 7.9 Extrusion stretch blow moulding (1) extrusion (2) blowing and conditioning (3) stretching (4) blowing (5) ejection...

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