PET polyethylene terephthalate, a type of polymer, is mainly used in food packaging films, textile fibers, and other applications. Now, its usage as a packaging material is increasing, not only for soda bottles, but also for amorphous PET (APET), crystalline PET (CPET) cans and plates. In the past five years, engineering grade PET and copolyesters have been used as new polymer products for engineering and special packaging materials, respectively.

    The successful application of PET in packaging materials for soda drinks is due to its toughness and transparency, orientation ability, excellent economic value, and the development of high-speed bottle processing technology. PET beverage cans are lightweight, crush resistant, reusable, and have excellent airtightness. A fully filled 2-liter PET beverage bottle is 24% lighter than a similar glass bottle; The weight of an empty bottle is 1/10 of that of a glass bottle of the same model. Enable it to save labor, energy, and costs in all stages from producers to consumers

Chemistry and Performance

     PET for beverage bottles is produced from phthalic acid (TPA) obtained by the oxidation of p-xylene. Benzoic acid can be purified or reacted with methanol to produce dimethyl terephthalate (DMT), or further oxidized to produce pure terephthalic acid (PTA). Another basic raw material for PET is ethane, which is converted into ethylene glycol (EG) through a reaction. PET is a condensed polymer produced by the continuous polymerization reaction of DMT (or PTA) and EG in a molten state, which is then polymerized in a solid state to obtain large grains, final molecular weight, and intrinsic viscosity. This solid-state process also results in a sufficiently low ethanol content in the polymer.

   The melting point of general commodity PET resin is about 480F, but the melting point of high crystalline PET is about 520F.

   Directed crystalline PET has excellent strength. Resilience and transparency, as well as resistance to weak acids, bases, and many solvents.

Special level

     Stretch blown PET can provide solid, green, and light yellow PET. The colored polymer in the reactor does not require any adverse effects on its physical properties and improves the uniformity of color. Various pure resins with different intrinsic viscosities can be obtained. The slow crystallization rate of PET copolymers allows for the production of high-quality soda bottles under a wide range of processing conditions. A polymer that can be extruded and blow molded can also be provided. This material has the advantages of excellent melt strength and slow crystallization speed, and can be easily processed on suitable extrusion blow molding equipment. Various reinforced, flame-retardant, and other specialized polymers are constantly being introduced or improved to meet new applications.

    PETG copolyester is another example among many copolyesters. Unlike PCTA modified with acid, PETG is a diol modified polymer composed of CHDM diol combined with TPA (phthalic acid) and ethylene glycol. PETG copolymers can be molded or extruded and typically retain amorphous, transparent, and virtually colorless properties, even in large cross-sections.

It has high stiffness, hardness, and good toughness, even maintaining the required toughness at low temperatures. The combination of transparency, toughness, and melt strength makes it suitable for injection molding, blow molding, and extrusion of profiles, pipes, films, and sheets. PETG has unmodified or various additives, including release agents, color masterbatch, and impact modifiers, used for injection molding.

    PETG should be dried at 120-160F for about 4-6 hours before molding or extruding. The temperature range of the melt in both processes is from 420F to 510F. The holding time of processing equipment at higher temperatures should be minimized as much as possible to prevent excessive degradation. Injection molding should be carried out on an injection machine, with a required injection volume of 50% to 80% of its capacity per injection.

    PETG can be extruded and blow molded at a melt temperature between 400-450F to produce transparent bottles for shampoo, liquid detergent, hygiene products, mineral oil, and food packaging. This material meets FDA standards and can come into contact with food.

Extrusion can produce a wide range of profiles, as well as packaging pipes, films, and sheets, including pharmaceutical equipment packaging. PETG and PCTA can be disinfected with ethylene oxide and Y-radiation.

    When used for injection molding, PETG is usually processed within the melting temperature range of 450-510F, and the mold temperature is approximately between 70-130F. Current applications include instrument covers, machine shields, cosmetic containers, lever device pointers, display components, and toys.

    PET is mainly used in the packaging of soft drinks such as soda. PET has almost 100% occupied the market for non recyclable 2-liter packaging containers, and PET bottles of 1.5 liters, 1 liter, 0.5 liters, and even smaller have been widely recognized.

    PET is used in food, alcohol, and detergents. The demand for PET in carbonated beverages and industrial product packaging is expected to continue to grow. The packaged food includes mustard, gum products, peanut butter, seasonings, cooking oil, cocktails, and concentrated fruit juices. New colors, especially Weber color PET in pharmaceuticals. Vitamins and cleaning agents are very popular on packaging.

    One of the latest and fastest-growing applications of PET containers is food or beverage packaging, which requires filling at high temperatures. Many foods, especially fruits or high fruit content foods or beverages, must be packaged at a temperature of 180F or higher. This provides pasteurization (disinfection) for products and containers during filling. Typical oriented containers, such as those used for packaging soda and soft drinks, tend to shrink and deform when subjected to high temperatures above 160T, due to a certain degree of stress relaxation. Stress concentration occurs during stretching and blow molding of containers. The technology of improving heat resistance during processing has been developed, commonly referred to as "heat setting" technology. According to specific processing techniques, there are several processing technology details with high patent rights. Based on this, containers suitable for infusion at 190-195F can be produced. Products that require packaging with this characteristic include pure fruit juice. High juice beverages, tea, certain isotonic and sports drinks, seasonings, concentrated fruit juices, and certain mineral waters.

     The other end uses of PET are widely used in extrusion coatings and extruded films and sheets. PET is used as an extrusion coating material for baking cardboard packaging. In addition, crystalline PET (CPET) can also be used as the basic material to make plates in ovens.

     PET film is usually biaxially oriented and used for X-ray and other photographic films, meat and cheese packaging, magnetic tapes, electrical insulation, printing boards, and bottle packaging bags. PET is also used as an industrial tape material. Amorphous and non oriented PET films and sheets are beginning to expand for use in shaping containers, trays, foam products, and beverage cups.

     Summary: PETG is an upgraded version of PET, with higher transparency, greater toughness, better impact resistance, and of course, a higher price.