MATERIALS / RECYCLING PETplanet Insider Vol. 24 No. 01+02/23 www.petpla.net 31 ∆E* (Delta E) through five melt heat histories which is the equivalent of two full recycle loops, focusing on the total colour shift of the L*, a*, b* values. This approach can be used to screen the heat stability of additives, such as PET toners. The below chart is an example of how ∆E* can be used to compare two toner products. ColorMatrix Optica toner was formulated with specific colourants that show improved stability through these multiple cycles and therefore contribute less to yellowing and colour variation in the rPET stream than a standard toner. Processability As the number of heat exposures to rPET increases due to rising use levels, the processability of rPET will decrease. Mechanical recycling of PET produces a PET product with a lower mechanical strength compared to virgin PET with an equivalent intrinsic viscosity. These materials process differently, particularly during the bottle-blowing process. They heat up differently, stretch differently, and, when used in combinations or blends, can lead to a number of bottle-blowing process issues. This significantly narrows the bottle-blowing parameters for achieving a good quality PET bottle, resulting in poor quality bottles, reduced line speeds, increased blowouts, increased downtime, and increased scrap rates. Bottle-blowing process aides, such as ColorMatrix Smartheat RHC, improve the preform heat up rate and heating uniformity, allowing for a wider bottle-blowing window. This enables optimisation of the bottle-blowing process and polymer weight distribution within the bottle sections. The resultant will deliver improved quality and mechanical strength, helping to reduce processing issues such as blowouts, downtime, and scrap rates even at higher usage of rPET. In contrast to other reheat agents, SmartHeat RHC has minimal impact on final product colour or aesthetics and is accredited by the American Plastic Recyclers (APR). Performance Maintaining the desired processability is one of many challenges that additives will have to face within a market contemplating the increased use of rPET. Additive performance with rPET will also have to be addressed. This is true for oxygen or acetaldehyde scavengers as well as toners or process aids. For example, oxygen scavenger technology is essential to the food packaging industry because it prevents or delays oxygen ingress into plastic packaging to extend shelf life and reduce food waste. Many commercial technologies are based on metal catalysis to function. This catalysis has been proven successful and offers full compatibility and performance when used with virgin resins. As the amount of rPET is set to increase, oxygen scavengers will face the challenge of maintaining performance regardless of the quantity or quality of rPET utilised. Impurities from different rPET grades can cause the deactivation of the metal catalysts currently used. Suppliers of oxygen scavenger technologies must help the market implement and achieve their sustainability targets by developing new technologies that can perform equally well with increasing amounts of rPET and with the prospect of utilising up to 100% recycled content in the future. For this purpose, Avient has developed ColorMatrix Amosorb 4020R, an oxygen scavenger designed to maintain consistent oxygen scavenging with the most commonly employed rPET grades, regardless of the quantity of rPET utilised in the bottle. Amosorb 4020R thus gives performance, raw material choice flexibility, and supports achieving multiple recyclability targets at once. The amount and quality of rPET that will be used could also affect specific market segments more than others. Acetaldehyde is intrinsically present in variable quantities in materials such as rPET. Its presence can profoundly affect the water bottle market because even a small migration of such substance from packaging can change the organoleptic properties of water. The use of ColorMatrix AAzure acetaldehyde control tech-
RkJQdWJsaXNoZXIy NTY0MjI=