In order to give the bottom of the bottle its proper concave shape-so that it can stand upright-a separate bottom piece is attached to the mold during the blowing process. The entire procedure must be done quickly, and the plastic must be pressed firmly against the wall, or the bottle will come out misshapen. The combination of high temperature and stretching in the desired direction causes the molecules to polarize, line up and essentially crystallize to produce a bottle of superior strength. The pressure of the air stretches the plastic both radially ("out") and axially ("down"). Highly pressurized air then shoots through the mandrel and fills the Preform, pressing it against the inside walls of the mold. A steel rod (a mandrel) is slid into the Preform. Next, the Preform tube is re-heated and placed into another mold, which is shaped like a soda bottle, complete with screw-top. The Preform is then cooled and shaped to the proper size/length. First, PET pellets are injection molded-heated and put into a mold-into a thin walled tube of plastic, called a Preform/Parison. PET beverage bottles are made using a process known as stretch blow molding (also called orientation blow molding). Later, it can be reheated for its various uses. After the PET mixture reaches the required viscosity (thickness), it is cooled to avoid degradation and discoloration. In this process, a polymer is formed while another molecule is released, or "falls out." The condensation polymerization of bis 2-hydroxyethyl terephthalate is carried out in a vacuum at 530 degrees Fahrenheit (275 degrees Celsius) and results in chains of PET and ethylene glycol (see step #1 above) the latter substance is continuously removed during polymerization and used to make more PET. The final step of polymerization involves the condensation polymerization of the bis 2-hydroxyethyl terephthalate. Next, the dimethyl terephthalat, is combined with an excess of ethylene glycol at 305 degrees Fahrenheit (150 degrees Celsius) to yield another substance, bis 2-hydroxyethyl terephthalate and methanol. This reaction yields dimethyl terephthalate and water. To make PET, terephthalic acid is first combined with methanol (CH 3 OH). In polymerization, smaller molecules are combined to form larger substances. Aluminum, a close second, is 34 percent, while glass, which used to be 100 percent of the bottles, is only a small percentage of those sold today.īefore the bottles can be made, the PET itself must be manufactured, or polymerized. Accounting for 43 percent of those sold, PET is the most widely used soft drink container. It makes up 6.4 percent of all packaging and 14 percent of all plastic containers, including the popular soft drink bottle. Pet preform bottles generator#PET is used to make many products, such as polyester fabric, cable wraps, films, transformer insulation, generator parts, and packaging. The soda bottle so common today is made of Polyethylene Terephthalate (PET), a strong yet lightweight plastic.
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