Polyethylene Terephthalate (PET)
Polyethylene terephthalate is commonly known as polyester.
In 1946, the British Whiffield first published a patent for polyester, and conducted trial production in the British ICI company. In 1953, the company first conducted trial production of polyester film. In 1954, DuPont in the United States also produced this kind of film. France and Japan have successively produced polyester films, fibers and sheets.
Features of polyester resin:
Polyethylene terephthalate-based crystalline polymer, with a density of 1.30～1.38g/cm³ and a melting point of 255ºC～260ºC, has the greatest strength and toughness among thermoplastics, and its film tensile strength is comparable to that of aluminum foil , 9 times that of polyethylene and 3 times that of polycarbonate and nylon.
Polyethylene terephthalate maintains its excellent physical and mechanical properties in a wide temperature range. The temperature from -20ºC to 80ºC has little effect. The long-term use temperature can reach 120ºC, and it can be used for a period of time at 150ºC.
Although the air permeability of polyethylene terephthalate is larger than that of polyvinylidene chloride, it still has good gas barrier properties as a packaging material. For a film with a thickness of 25um, the oxygen permeability is 29cm³/m²·Mpa, and the carbon dioxide is 130cm³/m²·h·Mpa, and the hygroscopicity is low. The moisture absorption rate is less than 0.6% when immersed in water at 25ºC for 1 week, maintaining dimensional stability.
Polyethylene terephthalate is also resistant to hydrofluoric acid, phosphoric acid, acetic acid, and oxalic acid at higher temperatures, but hydrochloric acid, sulfuric acid, and nitric acid can damage it to varying degrees, such as a decrease in tensile strength. Strong alkali, especially alkali at high temperature, can hydrolyze its surface, and the effect of ammonia water is more severe. Ethyl acetate, butanone, xylene, naphtha, ethylene glycol methyl ester, methanol, acetic acid, etc., are not corroded at room temperature or near their boiling point, dissolved in o-chlorophenol, tetrachloroethane , a mixed solution of cresol or excess nitrobenzene.
Properties of polyester sheet series:
The polyester sheet series includes PETG, APET, PCT and other varieties, which are new sheet products developed and developed rapidly in recent years.
Polyester sheet has many advantages such as excellent comprehensive properties, high transparency, good strength, and easy post-processing. Due to its good strength, products of the same thickness have significantly better protection than PVC sheets. If the same strength is compared, a thinner polyester sheet can be used, so although the weight and price of the polyester sheet are higher, the actual cost increase is not large, and the most important thing is that the transparent and crystal clear polyester sheet increases the packaging effect. , so that the packaging on a higher level. In addition, it is non-toxic, odorless, tasteless, and meets the hygiene requirements of food packaging. It does not have the problem of secondary pollution of the environment when PVC sheets are incinerated. In the case that PVC sheets are prohibited from being used in disposable packaging, it can meet the requirements of food packaging. Packaging applications have higher strength sheets, undoubtedly polyester sheets. The processing of polyester sheet (blister or folding box) is convenient, and ordinary blister machines can process it normally, and the efficiency is the same as that of PVC sheet, so the original equipment for producing PVC sheet blister products does not need any modification.
Amorphous polyester sheet (APET)
APET sheet is obtained by extrusion molding of resin modified by polyester with isophthalic acid and diethylene glycol. Since the molten PET material extruded from the die is quenched and shaped into a sheet, the resin is in an amorphous state, so the PET sheet has high transparency; Good mechanical properties, barrier properties, printing properties; easy to emboss decoration; easy to metallize; can be sterilized by r-ray; economical disposal of waste, including recycling, combustion, etc., only carbon dioxide and water are produced when burning , does not produce harmful substances. But APET is not UV resistant, and APET has good electrical insulation properties.
APET also has many properties that far exceed PVC, such as good low temperature resistance, excellent friction resistance, etc. It is a promising new type of plastic packaging material, and its application field is being further discussed and expanded.
The available range of APET sheets is 0.1-5.0mm, which is quite wide, providing a large room for the design and utilization of APET products.
APET sheet has good strength, excellent expansion performance and high light transmittance. It is suitable for high-strength transparent packaging, such as the packaging of food or oily items, and the blister packaging of stationery and tools.
Composite sheet: PETG/APET/PETG (GAG) , APET/Barex , APET/PE, PET/PVDC/PE, PET/PVC/PE, PET/EVOH/PE, PET/PVC.
Amorphous polyester sheet (PETG)
GPET, also known as PETG, is a non-crystalline PET resin modified with cyclohexanedimethanol, and its melting point is low, only 180℃～200℃. When PETG sheet has the characteristics of APET sheet, its biggest feature is outstanding heat sealing performance, easy operation during sealing and reliable heat sealing quality. Compared with APET, PETG does not crystallize at very high molding temperature, For vacuum forming, even clear contours of complex geometries can be obtained, but because of its high price, its application is limited.
The chemical stability of PETG is the same as that of APET.
Composite sheet: PETG/APET/PETG, PETG/PS/PETG, PS/PETG, PETG/PP.
Crystalline Polyester (CPET)
CPET is nucleated PET that allows the material to crystallize rapidly during processing. Heat resistance is a function of the crystallinity formed during thermoforming (maximum crystallinity up to 30%). CPET has a high barrier to air and water vapor. Chemical stability similar to APET and PETG.