How to Create a Better PET Sheet Recycling Program
Recycling of plastics — one of the best ways to reduce carbon footprint — offers two major benefits: recycling reduces the amount of oil required to produce more plastic, and also takes material out of landfills.
Recycling PET sheet, in particular, features many advantages compared with the recycling of other plastics materials and is one reason why more packaging manufacturers continue to convert to PET. The quality of PET does, however, impact the desirability of its collection and re-use — a fact that relates directly to product quality differentiations between PET manufacturers.
By way of further explanation: the molecular integrity of PET is altered when recycled. That is a characteristic similar to all other recycled resins. The higher quality a PET resin sheet is, the less the total degradation after reprocessing, which usually includes extrusion and either pelletization or calendering. Therefore, higher quality PET ensures a better “next life,” providing lower cost and improved package performance.
How is a quality PET sheet manufactured and why does it provide advantages compared to other processes? To answer that question we need first to examine conventional methods of producing PET.
The traditional manufacturing process for extrusion of APET sheet typically requires use of granulated resin from a third-party supplier. After delivery the resin needs to be dried in a four-to-six hour energy-intensive operation before being fed into the extruder. From there, the extruder compresses and heats the resin into a melt, which is then transferred to the die and onto the rollers to form the sheet.
By comparison, a direct-to-sheet process eliminates five energy-intensive stages of the conventional sheet production process (pelletizer, SSP, compactor, dryer and extruder). Through this methodology PET melt can arrive at the calendar stack heated to the proper temperature and therefore does not have to be dried and re-melted from the granular form. Users should note that this means there is no chance for contamination to enter the system. It ensures a finished polymer that is fully devoid of moisture and all moisture-related defects. Furthermore, there is absolute traceability as the resin is constrained to one source, providing origin of the resin and quality. In addition, the uniformity of the sheet allows a winder that constructs precision rolls with unnoticeable weave and near perfect formation. This minimizes side trim requirements at the thermoformer, providing a direct material savings. The direct-to-sheet process results in a material with superior clarity and gloss and should be considered when seeking a high quality PET sheet for recycling.
In conclusion, lower quality PET resin and sheet compromises on the overall PET recycling efforts. The best insurance for continued growth is for high quality PET to be used upfront.
Mohammed Razeem is project engineer, polymer development & sustainability, for OCTAL.
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