page_title: PET bottle recycling
section_title: Drying polyester
hierarchical_section_title: PET bottle recycling / Drying polyester
caption_attribution_description: English: This technical drawing shows a cross section of an infrared drying drum used for the drying of Polyester pellets and polyester bottle flakes
context_page_description: Bottles made of polyethylene terephthalate can be recycled and used to manufacture new bottles and containers, thermoform packaging, strapping and are also used in fiber applications such as carpet and apparel. In many countries, PET plastics are coded with the resin identification code number "1" inside the universal recycling symbol, usually located on the bottom of the container. The National Association for PET Container Resources defines PET as: "Polyethylene terephthalate items referenced are derived from terephthalic acid and mono ethylene glycol, wherein the sum of terephthalic acid and mono ethylene glycol reacted constitutes at least 90 percent of the mass of monomer reacted to form the polymer, and must exhibit a melting peak temperature between 225°C and 255°C, as identified during the second thermal scan in procedure 10.1 in ASTM D3418, when heating the sample at a rate of 10°C/minute."
context_section_description: PET polymer is very sensitive to hydrolytic degradation, resulting in severe reduction in its molecular weight, thereby adversely affecting its subsequent melt processability. Therefore, it is essential to dry the PET flakes or granules to a very low moisture level prior to melt extrusion.
  PET must be dried to <100 parts per million (ppm) moisture and maintained at this moisture level to minimize hydrolysis during melt processing.
  Dehumidifying Drying - These types of dryers circulate hot and de-humidified dry air onto the resin, suck the air back, dry it and then pump again in a closed loop operation. This process reduces moisture level in the PET down to 50ppm or lower. The efficiency of moisture removal depends on the air dew point. If the air dew point is not good, then some moisture remains in the chips and cause IV loss during processing.
  Infrared Drying polyester pellets and flakes - A new type of dryer has been introduced in recent years, using Infrared drying (IRD). Due to the high rate of energy transfer with IR heating in combination with the specific wavelength used, the energy costs involved with these systems can be greatly reduced, along with the size. Polyester can be dried and amorphous flake crystallized and dried within only about 15 minutes down to a moisture level of approx. 300ppm in one step, and down to <50 ppm using a buffer hopper to complete the drying in typically under 1 hour
caption: IRD drying drum used for the drying of Polyester pellets and polyester bottle flakes
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