Application of PVC plastics in blow molding process

　　

Core Tip: the so-called blow molding blow molding process, a method for producing hollow plastic products, often referred to as blow molding. In this way, not only is possible to manufacture bottles, containers and toys, but also

　　Blow molding process

　　The so-called blow molding, plastic is a method for producing a hollow article, also commonly referred to blow molding. In this way, not only to manufacture bottles, containers and toys, and can be molded fuel tanks, storage tanks and mannequins, etc. Therefore, although its history is not long, but it has now become one of the processing methods familiar to the plastics industry.

　　Plastic blow molding is not a new concept, its origins can be traced back to ancient glass blowing. Hot melt made of suitable glass tube, sealed at its top, and then employing mouth blow, split into hollow glass articles. This approach, so far, still as "a hand-blown glass products used to manufacture advanced, however, with regard to organic polymer thermoplastic materials blow molding, first recorded in 1851 the United States Patent and Armtrong's 1880 US Chrpentar s patent. The latter is made of celluloid blow Portrait, two nitrocellulose sheets of plastic film clip in a pair of mold together with the steam through a nozzle into two pieces of the question, and the sheet is heated to soften the blow molding hole shape Since the steam pressure and temperature influence exerted by the mold, so that the edges of the two sheets are fused and bonded to the entire article. town together to maintain the pressure to the mold and the product is cooled, and the excess of the sheet from the cut product. The products produced by this method, mainly confined to small and cheap novelty products, such as children's toys. The obvious drawback of this method is the production of extremely slow, and requires a lot of manual operations.

　　In contrast when the glass and thermoplastic blow molding, note that the following is important real booth. In the manufacture of glass bottles, because of the high thermal conductivity of glass, the use of blow molding techniques beneficial, even without a specific mold and Zhenmo device, you can also get higher productivity. However, for complex material, its low thermal conductivity, such as glass that can not be fully blow molding, and must be sealed and cooled mold, so that not only ensure the consistency of product shape and size, to obtain the necessary letters and pattern, and by means of cooling the mold, the production rate can be greatly improved.

　　Development of plastic blow molding

　　In the early stages of development as the amount of plastic blow molding, and its progress is not fast, especially in 1939 a 1945 World War II period to ask, blow molding processing technology compared to other vine branch progress more slowly. This is mainly involving two reasons, first, as a blow-molded plastic varieties only - cellulose plastics, when the quota allocation, and supplied to the plastic bottle with poor quality, and the second, molded products and packaging, whereas in into contention period, it is considered a luxury. Since then, with the plastic industry in Sri Lanka Bureau of synthetic resin, especially large-scale industrial production of low-density polyethylene, which is a source of abundant, cheap, easy processing and packaging materials as adaptable to a huge blow-molded to facilitate role, it makes this technology a step on the stage of vigorous development. Therefore, despite the establishment of the modern plastic blow molding is around 1930, the industrial production of the United States began in 1940, Japan also started later than in the US column IO years, but on large-scale industrial development in the 1950s, it can be said with polyethylene plastic blow molding suspended while to develop. Mark a significant growth in the industry, by the number of companies engaged in plastic blow molding to illustrate, in the same decade from 1940 to 1950, the world's only a few plants for efficiency, but at the moment, has been increased to thousands only in Europe, blow molding plant on more than one thousand Pat.

　　In the beginning of the development of polyethylene blow molding technology, the difficulties encountered are unable to get bi-thick uniform products. This case, and then clinching shape design products have a great relationship. In addition, the products of the neck fixed burr diameter and finishing products after molding also technical problems.

　　Subsequently, in product design as well as two aspects of the parison thickness control access into the morning, so it is possible to produce a variety of shapes of complex products, the rapid expansion of product markets. First, a large number of low-density polyethylene bottles with a liquid detergent used in household packaging Such packaging containers than glass, metals and their packaging, the packaging container obvious advantages of glass, metal and other hard packaging container than is soft and can be extruded, but i need to have compelling packaging container Trademarks and appearance, Li inert polyethylene plastic surface, giving a variety of decorative techniques difficult. Until flame treatment, surface activation technique and screen printing, offset printing heir, stamping and printing Mino ornaments corona discharge treatment methods have been developed, the plastic container grate like other containers, from the forming, filling all the decorative lines together into integration. Therefore turn made by packaging a product, it is possible to install the blow molding equipment in the plant belongs to its own, and the product packaging container production organically combined, saving turnaround costs and production costs.

　　Following the low-density polyethylene, high density polyethylene start to come out. This material is now in the packaging blow molded bottles and containers unprecedented development, a large number of complex shapes and the use of durable products to develop the market. The main reason is that it has a greater rigidity, and can be made thinner bottles container, such as bi parapet to 0.13 mm thick may therefore be able to provide a lightweight and inexpensive package. In addition, it has a low water vapor permeability, coupled with the high temperature thermal stability during processing, the processing were more willing to choose. Since it entered the blow molding field since a large number of foreign Pat used to contain bleach and detergent and also successfully rejection to dress oil.

　　Important reason for the packaging industry began from glass, metal turning plastics, except plastic materials with light turn cheap, low shipping costs, not damaged, but also that the plastic can be poured into a variety of shapes and colors to adapt to a variety of containers and decorative printing technology. For example, can be used with a dominant packaging printing - Offset wears silk unmatched speed, delay can make the products have a very figurative decorative effect, which stimulates the growth of supermarket sales of products largely . Currently, many consumer goods from detergents, polishing agent to the ink, cosmetics have been extensive use of plastic blow molded packaging. However, it must be noted that both the low-density polyethylene or paste density polyethylene, oxygen, carbon dioxide, organic solvents and vegetable oils, have a permeability. Gang this, polyethylene containers are usually confined to the packaging of those substances for which it is not through, but the case is necessary, the choice of two double-layer composite material blown containers.

　　Incidentally, in the packaging industry, packaging and containers are often easy to confuse the two words, for which it is necessary to define. In general, the former refers to the package containing the product, used later on abandoned not show up, such as detergents Jing and columns cosmetic bottles. The latter refers to a device, which throughout its period, according to need, the container can be re-packaged products, such as feed spray bottle, a beer keg and reservoir and the like.

　　Plastic blow molding technology

　　Because of advances in the new blow molding equipment and rigid polyvinyl chloride (pvc) formulation technology, it is possible at very high production rates turn create extremely lightweight bottles and containers. The container has a rigid, toughness and compare low permeability characteristics, combined with its transparency can be comparable with the glass, only 8% of the weight of glass of the same capacity, and therefore, polyvinyl chloride (PVC) products rapidly blown into each other fruit juices, cooking oil, wine, shampoo, detergents and disinfectants and other products in the field of your disposable consumer packaging.

　　Plastic fruit juice bottles in 1962 came out, it was an early large-scale use of polyvinyl chloride (PVC) representatives, the success of these bottles will soon present except for the British retailer with external, almost at the same time or earlier some time, France uesilur food dumped oil factory decided to use rigid PVC bottles instead of glass, thus reducing transportation, cleaning, storage and other costs and save more labor.

　　In view of the polyvinyl chloride (PVC) bottle is designed to directly replace the existing glass as possible, their current and future applications in the food and beverage packaging, which creates a problem in that the polyvinyl chloride (PVC) plastic The toxicity problems. Food management systems of different countries, the situation is more complex. So in a way hampered PVC bottles application. For example, those that provide transparency stabilizer system for plastic bottles, some scholars believe are toxic, and Some scholars believe that the non-toxic alternative. In addition, polyvinyl chloride (PVC) of chlorine gas permeability is relatively high, it can cause fermentation and reduce packaging material vitamin content. In order to overcome this one point, we need a thicker bottles containing the results is the weight increase, to some extent, but also offset the economic advantages of thin-walled PVC bottle can provide.