What is PET?

What is PET? - 1

 

Polyethylene terephthalate or PET, PET is a polymer that is the most profitable raw material for the manufacture of packaging materials, including various containers. It is familiar to many consumers under different names - polyester, terylene, melinex, dacron, lavsan, mylar. As a rule, all these substances are almost indistinguishable from each other - the only difference is in the country of origin. In the countries of the USSR, polyethylene terephthalate was named lavsan - in honor of the Laboratory of High Molecular Compounds of the Academy of Sciences. It was here that the substance was successfully synthesized in the late 40s.

The abbreviation PET is most often used as an abbreviation for polyethylene terephthalate, and PET is used for products made from it.

Advantages of using PET for the production of containers

Polyethylene terephthalate began to be used on an industrial scale due to its characteristics:

  • High strength - the material can withstand numerous deformations and shock loads;
  • Plasticity - in the production of polyethylene terephthalate has a high value due to the ease of processing;
  • Inertness - polyethylene terephthalate is resistant to weak acids, alkalis, solutions, so the container is suitable for storing food, household chemicals, cosmetics;
  • Insolubility in water - polymer does not react with water;
  • Dielectric properties - the substance does not conduct current and is often used as an insulating material for various components;
  • Recyclable potential - polymer packaging and containers can be fully recycled;
  • Human safety - according to ILSI research, PET containers do not react with food, water or air and do not release toxic substances into the environment.

This material is externally an amorphous transparent substance. The substance is able to change its shape under the influence of temperature, during crystallization it acquires a stable solid form and a matte shade, lends itself to coloring and metallization. For the production of plastic containers, it is supplied in the form of granulate, which is a universal raw material. In this form, polyethylene terephthalate is suitable for various types of equipment. The listed properties of the material make it an irreplaceable raw material for the production of packaging materials, ropes, twines, preforms for bottles and cans, and other containers.

 

 

Viscosity

The intrinsic viscosity of PET is in the range of 0.795-0.815 dl / g, while the substance with the maximum values ​​of this parameter is used for casting preforms. An increase in this characteristic decreases the rate of polymer crystallization. This also provides the high strength and durability of PET along with its dielectric properties.

Mechanical strength

The material is resistant to shock loads, tensile and bending deformations. It retains all these properties at temperatures ranging from -40 to + 60 ℃.

Low coefficient of friction

This material is resistant to wear and tear. Due to its low coefficient of friction, minimal creep in combination with high elasticity, PET is suitable for the manufacture of almost any container. Moreover, products from it can be used in the temperature range from -60 to 170 ℃.

Impact strength

The appearance and ability to transmit light (up to 90%) make PET similar to polycarbonate and acrylic - transparent plexiglass. At the same time, PET has a much higher impact strength - 10 times more than that of acrylic.

Main features of pet:  
Thermal Conductivity: 0,14 W/(m·K).
Compressibility (melt): 99·106 MPa
Elongation at break: 12-55%
The glass transition Temperature of amorphous polyethylene terephthalate: 67°C
Is the glass transition Temperature of crystalline polyethylene terephthalate: 81°C
Melting point: 250-265°C
Decomposition Temperature: 350°C
Refractive Index (Na line) of amorphous polyethylene terephthalate: 1,576
Refractive Index (Na line) of crystalline polyethylene terephthalate: 1,640
The Limit of the tensile strength: 172 MPa
Modulus of elasticity in tension: of 1.41·104 MPa
Water Absorption: 0,3%
Permissible residual moisture: 0,02%
Frost:  to -60°C