Compared to other plastic packaging materials , PET is the best material for soft drinks packaging . This is because PET has a high melting temperature , strength and transparency , excellent gas barrier property , flavor barrier properties, low cost, easy processability and recyclability and the like.However, PET bottles can not meet the special requirements of some drinks , such as hot drinks and some soft drinks. PET used in beer , fruit juice beverage packaging , oxygen, carbon dioxide, water vapor barrier properties and flavor of the packaging can not meet the requirements , affecting the quality of these products . Oxygen in the air into the plastic bottle or bottle of carbonated drinks in the carbon dioxide released, will accelerate the deterioration of the beverage . Although other polymers ( such as PEN) can solve the problem of the barrier , but the cost is too high and difficult to recycle . Improve PET barrier properties to oxygen, carbon dioxide has caused everyone's attention plastic packaging , there are some technical and some of the PET barrier properties of composite materials has to improve its performance.Coating PET bottlesTo ensure the quality of soft drinks , it is necessary to prevent the occurrence of gas in the plastic bottle wall permeability , gas permeability which requires a small selection of the packaging material , these materials are generally referred to as high barrier packaging materials . Improved gas barrier properties of PET bottles mainly in the following four ways: by multilayer coextrusion processing technology , so that it has a multilayer composite structure ; surface coating ; adding some gas trapping agent ; and other materials blended with barrier properties . Multi-layer co-extrusion technology which is currently the method has been successfully used , however, to improve the barrier properties of the small , but difficult to recycle , the higher the cost . Finish is an emerging technology for improving the gas barrier properties of PET bottles , can be very thin gas barrier film , which can effectively prevent the passage of gas molecules PET bottle wall , but also can solve the problem of recycling .At present, some coating materials have been used in the test of practice , in which diamond carbon films (DLC) and silicon oxide material is very popular on industrial materials . The gas plastic box barrier coating for improving the performance of a silicon oxide film of PET film to be earlier than diamond carbon . In the early 80s of the last century , plastic trays they began to be silicon oxide coating by physical vapor deposition and chemical vapor deposition methods . However, a silicon oxide film having a brittle surface in order to obtain PET lasting mechanical strength , it requires a relatively complicated process . In recent years, diamond carbon film ( amorphous hydrocarbon ) PET coated on the surface of some of the products have appeared on the market , the gas barrier properties of PET bottles has been greatly improved.Diamond carbon film coating processUsually diamond carbon film coating technique using plasma chemical vapor deposition (PCVD), under vacuum , by a plasma vapor deposition techniques to obtain very thin DLC coating on the surface plastic package of PET bottles . Process for preparing the coating is as follows : First, the bottle placed in a vacuum chamber for vacuum processing, and then injected into the C2H2 gas to produce a hydrocarbon -conversion under the action of pressure in the plasma , the ions and radicals finally deposited on the surface of the PET bottle get DLC coating.Diamond carbon film coating is plastic case characterized byDLC film containing a large amount of hydrogen , and therefore has a very packaging design good adhesion and resistance to fission capacity, while the PET bottle has the following advantages : the gas barrier properties , oxygen barrier and carbon dioxide , to ensure quality of the beverage ; flavor barrier properties , and prevent the bottle transport and packaging between the adsorption process , so that soft drinks to keep the original flavor ; UV barrier properties , having the function of absorbing ultraviolet rays , ultraviolet avoid the influence of soft drinks ; chemically inert and does not react with other substances having a chemical stability ; benefit for recycling PET bottles while maintaining the existing advantages.DLC coating makes the barrier properties of PET bottles has been greatly improved, but the barrier properties of PET bottles and temperature changes have a greater relationship. At elevated temperatures , the coated and uncoated PET bottles barrier properties are reduced, which indicates that although the thermal stability of the coating material , the thermal motion of molecules , but will still affect the gas barrier properties of PET bottles .Development of the DLC coating PET bottlesDLC -coated PET bottles primarily from future market needs, focusing on technology development and improvement. Prospects are very optimistic about clamshell packaging the market potential estimated share PET10% market share, is widely used in soft drinks packaging, including tea, juices , carbonated drinks. Currently packaging for tea drinks in Japan , has appeared on the market in 2005, has 50 million into the market. With the gradual expansion of the soft drinks market , DLC coated PET bottles will be further popularized.

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