In fact, everyone is familiar with PET. PET plastic and PET film are widely used in daily life. Polyethylene terephthalate (PET) is a thermoplastic polyester material, usually light yellow or milky white in color. Due to the highly symmetrical molecular structure, PET materials have excellent optical properties, film-forming properties and weather resistance, and are widely used in many fields. At last year's Home Furnishings and Building Materials Show, a new surface material, PET flat film, has been introduced. Therefore, we need to have a basic understanding of PET materials.
1. Structure and characteristics of PET material
The structure of PET is shown in fig. 1-1.
Figure 1-1. Molecular structure of PET
PET is a typical semi-crystalline polymer with a glass transition temperature Tg of about 70 degrees Celsius and a melting point of about 240 degrees Celsius. Due to its excellent comprehensive performance, PET materials are mainly used in various bottle shells, polyester films, and mechanical and electronic industries, such as film, packaging, chemical fibers, electronic devices, etc.
PET has good heat resistance: Modified PET can be soaked in a solder bath at 250℃ for up to 10s without any change.
PET has good mechanical properties: PET material is fatigue resistant, deformation resistant, has high hardness, and bending strength is more than 200 MPa.
PET material is cost-effective: The price of ethylene glycol, raw material for synthetic PET, is cheap, only half price used in PBT material, so this material and its modified engineering plastics have lowest price among similar plastics, most economical.
Second, PET modification method
There are also many ways to modify PET, mainly by filling and mixing other substances to eliminate initial defects of PET materials and improve their physical and chemical properties, so that some of physical and chemical properties of PET can be improved.
Figure 2-1 PET modification method
3.1 Glass fiber modified PET
The use of glass fiber (GF) to modify PET materials can greatly improve mechanical properties of PET and increase heat distortion temperature of PET, so it is widely used in polymer materials.
3.2 PET filling modification
The PET modification filling method is a relatively common method. Blending one or two different inorganic powders with polymers can improve performance of PET. The commonly used nanoparticles are clay, and method is mainly intercalation polymerization, which can finally be modified into PET/clay nanocomposites.
3.3 PET modified with polyester
Because two plastics, PET and PBT, are relatively similar in chemical structure, they can be highly compatible. PET blend modified with polyester has good physical properties, good chemical properties and thermosetting properties. The gloss is also very good. During modification reaction, a small amount of nucleating agent can be added to mixture so that it has a better shrinkage rate, and impact resistance of material is also better.
3.4 ABSReinforced Modified PET
Since ABS has good toughness, it can be used as a reinforcing modifier for PET so that modified material has good strength and shrinkage.
3. Application of modified PET plastic
Table 3-1 Applications of Modified PET Plastics
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