Terylene (a mark formed by inversion of (polyeth)ylenter (ephthalate)) is also spliced in bell rope plates to prevent wear of the strings when passing through the ceiling. Antimony (Sb) is a metalloid element used as a catalyst in the form of compounds such as antimony trioxide (Sb2O3) or antimony acetate in the production of PET. After preparation, a detectable amount of antimony can be found on the surface of the product. These residues can be removed by washing. Antimony also remains in the material itself and can therefore pass into food and beverages. When PET is exposed to cooking or microwave, antimony levels can be significantly increased, possibly above the maximum contamination levels of the U.S. EPA. [21] The drinking water limit set by the WHO is 20 parts per billion (WHO, 2003), and the drinking water limit in the United States is 6 parts per billion. [22] Although antimony trioxide is of low toxicity when taken orally[23], its presence remains of concern. The Federal Office of Public Health examined the amount of antimony migration and compared PET and glass bottled water: the antimony concentrations in the water in pet bottles were higher, but still well below the maximum permitted concentration.
The Federal Office of Public Health has concluded that small amounts of antimony from PET are transferred to bottled water, but that the health risk of the resulting low concentrations is negligible (1% of the “tolerable daily dose” set by the WHO). A later (2006) but more widespread study found similar amounts of antimony in water in PET bottles. [24] Who has published a risk assessment of antimony in drinking water. [23] The first is a transesterification reaction, while the second is an esterification reaction. Polyethylene terephthalate (PET) is a condensation polymer produced by esterification of ethylene glycol (EG) with terephthalic acid (TPA) or dimethyl terephthalate (DMT) and has the general formula (OOCC6H5COOCH2CH2CH2)n. Unlike the carbon-carbon compounds in the previously discussed polymers, polyesters are based on carbon-oxygen-carbon compounds, in which one of the carbons is part of a carbonyl group. The outstanding properties of PET films as a food packaging material are their high tensile strength, excellent chemical resistance, low weight, elasticity and stability over a wide temperature range (−60° to 220°C). PET films are most often used in the biaxially heat-stabilized form. There are two basic shaping methods for PET bottles, in one step and in two steps. Two separate machines are used in two-stage injection molding. The first injection machine molds the preform, which resembles a test tube, with the threads of the bottle cap already cast.
The body of the tube is significantly thicker, because in the second stage it is inflated in its final form with stretch-blow molding. PET can be mixed with other thermoplastics and thermosets to improve its performance and use it for various purposes. The purpose of the production of its mixtures is to improve the economy and its properties such as mechanical strength, flame retardant, transformability, etc. Treatment of polyester waste by total glycolysis to completely convert polyester to bis(2-hydroxyethyl)terephthalate (C6H4(CO2CH2CH2OH)2). This compound is purified by vacuum distillation and is one of the intermediates used in the production of polyester (see Production). The reaction is as follows: polyethylene terephthalate (or polyethylene terephthalate), PET, PETE or the obsolete PETP or PET-P) is the most common thermoplastic polymer resin of the polyester family and is used in fibers for clothing, containers for liquids and food, and thermoforming for manufacturing and in combination with glass fibers for engineered resins. [5] Acetaldehyde is a colourless and volatile substance with a fruity odour. Although it forms naturally in some fruits, it can cause a bad taste in bottled water. Acetaldehyde is produced by the degradation of PET due to improper handling of the material. High temperatures (PET decomposes above 300°C or 570°F), high pressures, extrusion rates (excessive shear flow rate increases temperature) and long container residence times contribute to acetaldehyde production. When acetaldehyde is produced, some of it remains dissolved in the walls of a container and then diffuses into the product stored there, changing the taste and aroma.
This is not such a problem for non-consumables (such as shampoo), for fruit juices (which already contain acetaldehyde) or for strong-tasting drinks such as soft drinks. However, for bottled water, a low acetaldehyde content is very important, because if nothing hides the aroma, even extremely low concentrations (10-20 parts per billion in water) of acetaldehyde can create a bad taste. .
