Extrusion International 2-2024

56 Extrusion International 2/2024 BLOWMOLDING PET Bottle Life Cycle and NIR Heating Technology The global PET containers market is expected to grow annually at 5.3% CAGR between 2022 and 2023. It will increase from USD 73,1Bn to USD 122, 4 Bn, according to the Future Marketing Insights report. More than 500 billion PET bottles are used globally to pack different products. Unlike other types of plastic, PET is 100% recyclable. N IR radiation is applied to various stages of PET bot- tle lifecycle: from pallets and preform injection to bottle blow molding and its recycling. The global trend to switch to rPET contributes to it. We will see why. IR radiation & thermoplastic polymers PET, or plastic #1 according to recycling symbol, is a thermoplastic polymer belonging to the polyester group. It is fully recyclable and widely used to produce bottles for beverages and jars for food, containers for vegetable oil and vinegar, household chemicals and cos- metics. Polyethylene terephthalate is often recycled into fi - bers, sheets, fabrics and definitely in new PET packag - ing. In natural state, the resin is colorless, semi-crystal- line, highly flexible. Once processed, it can be semi-rigid and rigid. Being thermoplastic polymer, heat impact leads to its softening and deformation. In bottle manufacturing, a PET preform once heated and passed to the mold, takes the shape of the latter. Thus, it is difficult to overesti - mate the importance of the heating systemof reheat PET stretch blowmolding machine and lamps in particular. Infrared lamps emit a wide range of frequencies. There are 3 types of infrared radiation: • Wave number near infrared with frequencies of 2500-714 nm (4000-14,000 cm -1 ) • Wave number mid infrared with frequencies of 25 000-2500 nm (400-4000 cm -1 ) • Wave number far infrared with frequencies of 2 500 000-25000 nm (4-400 cm -1 ) NIR lamps & bottle blow molding Different wavelengths interact with different com- pounds in different ways. Each type is defined either by the source of light to trigger an interaction between constituent wavelengths and compounds present in the sample, or the electromagnetic spectrum field analyzed. IR and NIR Spectroscopy both fall into the latter category. Both IR and NIR Spectroscopy use spectral data to characterize matter. The main difference is the field of the electromagnetic spectrum studied. NIR Spectrosco- py focuses on the 714 nm to 2500 nm range. This is just outside the range normally visible to the naked eye. Found in the 19th century, the near infrared energy found its industrial application only in the mid-20s cen- tury. It was used as add-on unit for other optical devic- es. In the 21st century its application expanded to PET stretch blow molding. PET Technologies is among the leaders in the field. Near infrared radiation perfectly penetrates PET and reheats PET preforms. In fact, the radiation in the NIR range can penetrate the PET samples completely to a depth. Beer-Lambert Law is the main principle and the basis for the different methods of spectrophotom- etry, including NIR spectroscopy. According to it, the amount of light absorbed by a sample (in this case, it is PET preform) is directly related to the volume of sample the light passes through and the concentration of the sample. The importance of NIR technology is difficult to over - estimate for manufacturing of such PET bottles as: • Asymmetric bottles;