PETpla.net Insider 07+08 / 2020

MATERIALS / RECYCLING PETplanet Insider Vol. 21 No. 07+08/20 www.petpla.net 27 out. However, the performance is still comparable against films made from UV masterbatch, checked by various param- eters such as tensile strength, transmit- tance and optical properties. The compe- tition between PET resin producers and masterbatch producers in processing will be interesting, states Chitec. Chiguard as a powder form used during PET processing is claimed not to affect IV or other mechanical prop- erties. Some liquid UV absorbers are considered quite difficult to handle when a biaxial extension is applied for the pro- duction of film. In a recent study, 200um PET films were produced aiming for a 400nm sharp cut-off. Transmittance at 390nm, 400nm and 410nm was moni- tored initially and then after 500hr Xenon Arc lamps exposure. Trans- mittance (%) PET without UV absorber With 1.5% Chiguard 0hr 500hrs 0hr 500hrs at 390nm 77.1 39.4 0.1 0.2 at 400nm 77.6 67.5 0.1 3.6 at 410nm 78.1 72.0 3.1 28.8 With a 1.5% dosage of Chiguard, a complete UV blocking effect is claimed to be easily achievable and perfor- mance is maintained after 500hrs QSUN keeping transmittance at less than 10% at 400nm. Optical properties with Chiguard addition are also main- tained as shown below: L a* b* Blank PET 92.82 0.05 0.56 With Chiguard 92.76 2.28 4.93 It is also possible to combine other UV absorbers to reach moderate UV coverage for various end usages. Synergy between two benzotriazole compounds was reported in US patent number US2006/0083940A1. The stud- ies demonstrated that UV coverage using a combination of benzotriazole (UV-234 and UV-326) was much better than using each separately either in the same layer or in a multiple film structure. It still allowed a 12% transmission at 390nm by combining two UV absorb- ers, for the thermoplastic films with 66um thickness and 1.2% total dosage. Chitec Technology would like to find more potential applications developed with this new Chiguard product which other UV absorbers are not always able to achieve. For instance, it is possible to make one thin PET film to greatly reduce the harmful blue light from LCD screens, thus improving the reading experience. Safety of use is the first considera- tion in considering the potential for food packaging and cyanoacrylate com- pounds are not new faces in PET indus- tries. A preliminary study of potential migration of Chiguard from PET film was conducted with a 1,400 ppm dosage. Chitec states that they were unsurprised to find no detectable (ND) results, and they did not see any trace of Chiguard in simulants applied for extraction under 60°C over a period of ten days. The results are given in the table below: Blank Chiguard in simulant 10% ethanol ND ND 3% acetic acid ND ND Vegetable oil ND ND More studies are to be undertaken after these promising results so as to comply with food packaging regulatory requirements in the near future, states the company. Another example is given in a 80um PET film with a 2% dosage of Chiguard, exposing the bottles of various colours to sun light for 48hrs. Yellow, orange, red and blue diluents are made by crocin dyes, natural colours easily degraded by UV. The glass bottles under the sun on the right show signifi- cant colour fade. The bottles on the left covered by the UV blocked PET, show great colour stability in comparison, especially for yellow and orange. Glass and PET bottles of different colour shades and their degradation by UV (glass on the right, PET on the left of each colour) The studies are supported by the Industrial Technology Research Insti- tute in Taiwan with a team experience in handling PET resins, twin screw extruder and film making equipment. www.chitec.com