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Difference between PP material and PET material

- Dec 06, 2017 -

Difference between PP material and PET material

Polyethylene terephthalate, referred to as PET, is a high polymer derived from the dehydration condensation of ethylene terephthalate. Ethylene terephthalate is derived from the esterification of terephthalic acid with ethylene glycol. PET is milky white or light yellow, highly crystalline polymer, the surface is smooth and shiny. In a wide temperature range with excellent physical and mechanical properties, long-term use temperature up to 120 ℃, excellent electrical insulation, even at high temperature and high frequency, the electrical performance is still good, but less corona resistance, resistance Creep, fatigue resistance, abrasion resistance, dimensional stability are good.


① have good mechanical properties, impact strength is 3 to 5 times the other films, folding good. The company is located in:

② oil, fat-resistant, acid-resistant, dilute alkali, resistant to most solvents. The company is located in:

③ has excellent high and low temperature performance, long-term use in the temperature range of 120 ℃, short-term use can withstand 150 ℃ high temperature, resistant to -70 ℃ low temperature, and high and low temperature on the mechanical properties of small. The company is located in:

④ gas and water vapor permeability is low, both excellent gas barrier, water, oil and odor properties. The company is located in:

⑤ high transparency, can block UV light, good gloss. The company is located in:

⑥ non-toxic, tasteless, good health and safety, can be used directly for food packaging.

PP is short for Polypropylene, the Chinese name is polypropylene, commonly known as 100% plastic. PP (polypropylene) Ziegler - Natta catalyst propylene monomer polymerization and polymerization, the molecular chain is arranged in a very structured crystalline isotactic polymer. PP (polypropylene) according to its crystallinity can be divided into isotactic PP (PP) and random PP (PP), isotactic polypropylene is highly crystalline thermoplastic resin, the degree of crystallinity up to 95%, the molecular weight of 8- 150,000; atactic polypropylene atypical polypropylene is a non-crystalline, microstrip sticky white waxy, low molecular weight, in the 3000-10000, the structure of irregular lack of cohesion, less application. PP raw materials commonly used is isotactic polypropylene. Polypropylene is a polymer with propylene CH2 = CH-CH3 as monomer

Polymerization reaction to obtain polypropylene, the chemical formula can be expressed as (C3H6) n, the structure can be simply expressed as [-CH2-CH (CH3) -] n. English full name: Polypropylene PP molecular structure is a typical regular structure, Crystalline polymer.

Application range

Automotive industry (mainly using metal additives such as PP: fenders, ventilation ducts, fans, etc.), appliances (dishwasher door liners, dryer ducts, washer frames and covers, refrigerator door liners, etc.) Use consumer goods (lawn and garden equipment such as lawnmowers and sprinklers, etc.).

Chemical and physical properties

PP is a semi-crystalline material. It is harder and has a higher melting point than PE. As PP products

Homopolymer type PPs are very brittle above 0 ° C and therefore many commercial PP materials are block copolymers with random copolymers of 1 to 4% ethylene or higher ethylene contents. Copolymer type PP materials have lower heat distortion temperature (100 ° C), low transparency, low gloss, low stiffness, but have a stronger impact strength. The strength of PP increases with ethylene content. Vicat softening temperature of PP is 150 ℃. Due to the high degree of crystallinity, the material has very good surface stiffness and scratch resistance. PP does not exist environmental stress cracking problems. In general, PP is modified by adding glass fibers, metal additives or thermoplastic rubbers. PP flow rate MFR range of 1 to 40. Low MFR PP material better impact resistance but lower ductility. For the same MFR material, the copolymer type is stronger than the homopolymer type. Due to crystallization, PP shrinkage is quite high, generally 1.8 to 2.5%. And the direction of shrinkage uniformity than PE-HD and other materials is much better. Adding 30% glass additives can reduce shrinkage to 0.7%. Homopolymer type and copolymer type PP materials have excellent resistance to moisture absorption, acid and alkali corrosion resistance, anti-solubility. However, it is not resistant to aromatic hydrocarbons (such as benzene) solvents, chlorinated hydrocarbons (carbon tetrachloride) solvents and the like. Polypropylene (PP) is a lighter plastic common, its excellent electrical properties, can be used as high-frequency heat-resistant insulation materials. PP is a crystalline polymer, the melt condensation due to large volume changes, a high degree of molecular orientation showed a larger shrinkage (1.0% -1.5%). PP in the molten state, with the temperature to reduce the viscosity of little effect. Therefore, in the molding process, should be to increase the injection pressure and shear rate-based, in order to improve the quality of products forming.


    PET polyethylene terephthalate common in mineral water bottles, carbonated beverage bottles. When the temperature reached 70 ℃ easy to deform, and harmful substances on the human body melted. After using plastic product No. 1 for 10 months, carcinogen DEHP may be released. Such bottles can not be placed in the car in the sun, can not be installed wine, oil and other substances.


    PP polypropylene common in soy milk bottles, yogurt bottles, microwave meal boxes, melting point up to 167 ℃, is the only plastic products can be placed in the microwave oven, can be carefully cleaned and reused. It should be noted that some microwave meal boxes and boxes are made of PP No. 5 but the lid is made of PET No. 1. Since PET can not withstand high temperatures, it can not be placed in the microwave oven together with the box.

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