Pet Bottle/Containers from Pet Resin
Polyethylene terephthalate (sometimes written poly(ethylene terephthalate), commonly abbreviated PET, PETE, or the obsolete PETP or PET-P), is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fiber. It is one of the most important raw materials used in man-made fibers. Depending on its processing and thermal history, it may exist both as an amorphous (transparent) and as a semi-crystalline (opaque and white) material. Its monomer can be synthesized by the esterification reaction between terephthalic acid and ethylene glycol with water as a byproduct, or the transesterification reaction between ethylene glycol and dimethyl terephthalate with methanol as a byproduct. Polymerization is through a polycondensation reaction of the monomers (done immediately after esterification/transesterification) with ethylene glycol as the byproduct (the ethylene glycol is recycled in production). The majority of the world's PET production is for synthetic fibers (in excess of 60%) with bottle production accounting for around 30% of global demand. In discussing textile applications, PET is generally referred to as simply "polyester" while "PET" is used most often to refer to packaging applications. PET can be semi-rigid to rigid, depending on its thickness, and is very lightweight. It makes a good gas and fair moisture barrier, as well as a good barrier to alcohol (requires additional "Barrier" treatment) and solvents. It is strong and impact-resistant. It is naturally colorless with high transparency. PET bottles are excellent barrier materials and are widely used for soft drinks. For certain specialty bottles, PET sandwiches an additional polyvinyl alcohol to further reduce its oxygen permeability. There are two basic moulding methods for PET bottles, one-step and two-step. In two-step moulding, two separate machines are used. The first machine injection moulds the preform. The preform looks like a test tube. The bottle-cap threads are already moulded into place, and the body of the tube is significantly thicker, as it will be inflated into its final shape in the second step using stretch blow molding. In the second process, the preforms are heated rapidly and then inflated against a two-part mould to form them into the final shape of the bottle. Preforms (uninflated bottles) are now also used as containers for candy. In one-step machines, the entire process from raw material to finished container is conducted within one machine, making it especially suitable for moulding non-standard shapes (custom molding), including jars, flat oval, flask shapes etc. Its greatest merit is the reduction in space, product handling and energy, and far higher visual quality than can be achieved by the two-step system. All over the world, the big soft drink suppliers are diversifying their portfolios to include niche and prospective growth products, like fruit-juice-based beverages, reinvigorating their ranges with national and regional brands, and seeking out and using market-friendly packaging options. Over the last two years in India, Coca-Cola has for the first time been marketing the established maaza fruit-juice-based beverage brand in PET containers. Of the soft drinks market in India, 70% is covered by returnable glass bottles, while about 25% comes in PET, and approximately 5% of still beverages are carton packaged. The aluminium can is a negligible quantity, at just under 1%, simply by reason of cost; while Indians can buy a normal lunch for 15 rupees, they have to pay 30 rupees for a can of soft drink. Since PET packaging has been riding a continuous wave of popularity.