Blow Moulded Bottles

In 2005, Husky working alongside BIOTA Brands of America, blow moulding equipment supplier SIG Corpoplast and Cargill Dow, which supplied its NatureWorks PLA material, introduced the first biodegradable water bottle onto the US market. Husky supplied BIOTA with the 24-cavity HyPET 120 injection moulding system. 

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Flame treatment is predominantly used with articles of relatively thick section, such as blow moulded bottles, although it has been applied to polyolefin films as well. The most important variables in the process are the air-gas ratio and their rate of flow, the nature of the gas, the separation between burner and surface, and the exposure time. 

In-mould labelling (IML) used for injection-moulded products and blow-moulded bottles is an alternative to self-adhesive or heat-transfer decoration, eliminating a finishing step. 

Thermoplastics consist of long chains of molecules, in the case of PE these are unbranched. Many of these chains together form a tangle which is more difficult to unravel the more branched the chains are. The branches are like hooks which cause the molecules to catch. Under the influence of relatively small external forces chains and parts of chains can slide across each other. PE is for instance used to make containers, chemical tubing and blow-moulded bottles. Some other thermoplastics are polypropylene (crates), polyvinyl chloride PVC (pipes) and polystyrene (foam). 

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. 

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 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. 

If the product demands complete protection from metal contact, a polyethylene liner can be used. The liner can be applied in situ by a sintering process or formed as a separate blow-moulded bottle. The resultant container is more accurately described as a composite container rather than a steel drum, as it combines the virtues of plastic and metal in one container. 

A common way to increase the bending stiffness of products from melt-inflation processes is to use corrugations. It is not possible to create ribbed shapes, described in the next section, because there is no independent control of the shape of the inner surface of the melt. Corrugations are seen on thermoformed products, blow-moulded bottles and extruded pipes. 

Explain how the external water cooling of extruded pipes leads to tensile residual hoop stresses at the bore of the pipe. To see whether a similar effect exists in a blow-moulded bottle, cut off the base and top, then cut down one side with a razor blade. If it curls up to a smaller diameter there are residual compressive stresses on the outer surface. 

At present, PLA-based materials are mainly referenced on three different markets, namely, the biomedical (initial market), the textile (mainly in Japan) and the packaging (mainly food, i.e. short-term applications). For instance, reported types of manufactured products are blow-moulded bottles, injection-moulded cups, spoons and forks, ther-moformed cups and trays, paper coatings, fibres for textile industry or sutures, films and various moulded articles [8]. 

Flame treatment is mainly used for pre-treating plastic articles of fairly thick section, such as blow-moulded bottles and thermo-formed tubs. Its early application to polyolefin film treatment was not sustained because of process control difficulties and safety problems however, these have been overcome in recent times, and flame treatment competes with Corona discharge treatment in this area once again. 

Fig. 1. Schematic diagram of set-up for flame treatment of blow-moulded bottles...

Even with a good clarifier, most PP products still cannot quite match the high clarity and very low haze of PET, except in thin sections and stretch blow moulded bottles, although they can be made clear enough for most purposes. The amount of haze in clarified PP depends on whether the PP is a copolymer or homopolymer. 

Figure 8.4 Photographs of PHA resin supplied as pellets (a) and as blow moulded bottles (b) (images supplied by Mirel ).

Copolymers containing 3—10% ethylene or propylene have improved processing characteristics compared to the homopolymer and have been suggested for such applications as blow moulded bottles. 

High grade polymer is being rrsed for biomedical application including woven patches. Id s biodegradable plastics has found applications as a blow moulded bottle, injection moulded caps for hair care products, disposable razors with BIOPOL handle, rubbish bags, disposable nappies, paper plates, and cups coated with thin plastic films made up of BIOPOL, and so om fir 1990 s, Metabolix and Monsanto have been the driving forces for the commercial production of PHA polymers in United States. 

Figure 1.5 Blow moulded bottle, (a) complete bottle, (b) Inside view through neck...

Blow moulded bottles were pigmented by pre-blending natural polymer with a yellow masterbatch in steel drums using an end-over-end blender. By dedicating individual drums to a particular colour, potential cross-contamination of colours was minimised, and cleaning was unnecessary. Transfer was by a standard vacuum hopper loader to the blow moulder hopper. 

BiopoF polymers are currently the only commercially available bacterially derived polyhydroxyalkanoates. The polymers can be processed on most types of conventional thermoplastic melt-processing equipment. Examples of product forms include a wide range of injection-moulded products and extrusion blow-moulded bottles. Foamed products can also be produced [60]. 

Oriented fibres, stretch-blow-moulded bottles and biaxially oriented film have also been demonstrated. 

Unival HDPE resins have been developed for blow-moulded bottles, drums, and other industrial containers. These resins have excellent rigidity, superior stress crack resistance, high impact and melt strength, and moderate swell. Unival resins are used to produce bottles up to 20 gallons in size used to contain household industrial chemicals, toiletries and cosmetics, health and medicinal aids, food products, and milk, juice, and water. 

These materials have better resistance to stress cracking that PE or PP, superior low-temperature toughness compared with PP or PE, better fatigue resistance than PP, and are of low density. The disadvantages are that crystallisation continues for 50 hours after moulding, and the low surface hardness. Applications include wire covering, film, and blow-moulded bottles. 

Polyethylene terephthalate (PET) is a semicrystaUine thermoplastic polyester used in the preparation of variety of products such as fibres, filaments, sheets and soft drink bottles (Shukla et al. 2003, 2006). PET is one of the best-known consumer plastic for high softening-point blow-moulded bottles and the world demand for PET bottles have... 

As discussed in detail by Briggs [35], although flame treatment has been applied to polyolefin films, it is now mainly used to pretreat thicker section components such as blow-moulded bottles. The increased adhesion that results enables the bottles to be successfully ink-printed. The component to be treated is passed over one or more burners, each burner consisting of a large number of closely spaced jets the burners are fed with an air-gas mixture in controlled proportions and the gas can be from the mains (largely methane) or bottled (propane or butane). Typically the component spends about 1 s, or less, in the flame. The most important variables are the position of the component relative to the flame the airrgas ratio the air/gas flow rate the nature of the gas the burner-surface separation and the exposure time. 

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