What are the differences between PETG and APET packaging materials?

PETG is a highly transparent copolyester plastic raw material. It features high transparency, good toughness and impact strength, excellent low-temperature toughness, high tear resistance, good processing performance, and excellent chemical resistance. It can be processed using traditional extrusion, injection molding, blow molding, and thermoforming methods. It is widely used in sheet and film, high-performance shrink film, bottle, and profile markets; it can be used to produce toys, household utensils, and medical supplies; it has passed the US FDA food contact standards and can be used in food, medicine, and cosmetic packaging.

APET is a thermoforming material, whose full chemical name is amorphous polyethylene terephthalate. APET thermoforming material: Polyester sheet (PET SHEET), also known as polyester rigid film, is a thermoplastic environmentally friendly plastic product. Its scraps and waste can be recycled, and its chemical elements are the same as paper, consisting of carbon, hydrogen, and oxygen, making it a biodegradable plastic. Packaging products made from this material, after being discarded, eventually become water and carbon dioxide. APET environmentally friendly film is widely used in packaging for cosmetics, food, electronics, toys, printing, and other industries, such as various high-end blister packaging, folding boxes, cylinders, and window films. A typical application is heat-shrinkable polyester film. APET has several advantages: First, good folding resistance; APET film does not show self-cracking creases like other materials, making it more suitable for surface decoration of documents, etc.; Second, low specific gravity; APET has a specific gravity 3.7% lower than general materials; Third, APET film has high transparency, especially good gloss; Fourth, very high strength; the strength of APET film is more than 20% higher than others; Fifth, low-temperature resistance, it can withstand temperatures of tens of degrees below zero without becoming brittle. Therefore, APET products are pollution-free, have no crystal points, high transparency, good smoothness, and strong impact resistance, and can be widely used in blister packaging, folding boxes, cylinders, and other exquisite packaging and various printed window films.

Polyester (PET) heat-shrinkable film is a new type of heat-shrinkable packaging material. Polyester (PET) film is a crystalline material, and ordinary polyester film can only achieve a heat shrinkage rate of less than 30% after special processing. To obtain polyester film with a higher heat shrinkage rate, it must be modified. That is, to prepare high-heat-shrinkage polyester film, ordinary polyester, or polyethylene terephthalate, needs to undergo copolymerization modification. The modified PET film can achieve a maximum heat shrinkage rate of over 70%. Due to its easy recyclability, non-toxicity, odorless nature, good mechanical properties, and especially its environmental friendliness, polyester (PET) has become an ideal substitute for polyvinyl chloride (PVC) heat-shrinkable film in developed countries.

In addition to being used as shrink labels, heat-shrinkable plastic films have also begun to be used in the outer packaging of daily necessities in recent years. This is because it protects packaged goods from impact, rain, moisture, and rust, while also allowing products to win over customers with beautifully printed outer packaging, and effectively showcasing the manufacturer’s positive image. Currently, more and more packaging manufacturers are using printed shrink film to replace traditional transparent film. This is because printed shrink film can improve the appearance of the product, facilitate product advertising, and create a lasting impression of the brand in the minds of consumers.

Heat-shrinkable plastic films are generally processed from amorphous plastics, such as polystyrene, polyvinyl chloride, and PVDC. Polystyrene (PS) shrink film has low strength and poor impact resistance, so it is rarely used; while polyvinyl chloride (PVC) is difficult to recycle and does not meet environmental protection requirements. In foreign countries, especially in Europe, polyvinyl chloride (PVC) plastic film has been banned from use in the packaging field, especially in food packaging.

Ordinary polyester is generally prepared from terephthalic acid (PTA) and ethylene glycol (EG) through esterification and polycondensation reactions, and belongs to crystalline polymers (strictly speaking, polymers with both crystalline and amorphous regions). Copolymer modification refers to the introduction of a third or even fourth component in addition to the two main components, terephthalic acid (PTA) and ethylene glycol (EG), to participate in copolymerization. The purpose is to create an asymmetrical molecular structure, forming an amorphous PET copolymer.

The third or fourth monomer introduced can be a dicarboxylic acid or a diol.  Dicarboxylic acids include isophthalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, etc.; diols include neopentyl glycol, propylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol, etc. When copolymer modification is carried out with a dicarboxylic acid, the resulting PET copolymer is called APET; when copolymer modification is carried with a diol, the resulting PET copolymer is called PETG.

Among the third monomers introduced, the most commonly used dicarboxylic acid is isophthalic acid (IPA). The addition of IPA can change the symmetrical and compact structure of the polyester, disrupting the regularity of the macromolecular chains, thereby reducing the intermolecular forces and making the polyester molecular structure more flexible. At the same time, the introduction of IPA makes it difficult for the polyester to nucleate and crystallize, and as the amount of IPA increases, the APET copolymer transitions from partially crystalline to amorphous. Because this modified polyester APET has reduced crystallization ability and a larger amorphous region, it can be used to manufacture high-shrinkage films. A recommended IPA content is around 20%.

The third monomer introduced can also be a diol. The most commonly used diol is 1,4-cyclohexanedimethanol (CHDM). In the polyester copolymerization process, the addition of CHDM has a significant impact on the Tg, Tm, and crystallization rate of the polyester. As the CHDM content increases, the melting point of the PETG copolymer decreases, the glass transition temperature increases, and the copolymer becomes an amorphous structure. However, the amount of 1,4-cyclohexanedimethanol (CHDM) added must be controlled within an appropriate range, usually 30-40%. This PETG modified with diols can be used not only to produce high-shrink films, but also for the production of heat-sealable films, highly transparent sheets, and many other applications.