FROM THE
PUBLISHER Susan Gibson, JSJ Productions, Inc.
Recycling & the Circular Economy The use of recycled materials is an important goal in today’s plalstics manufacturing world. We are pleased to feature a study conducted by Sibele Cestari at Queen’s University Belfast on the rotational molding of polyethylene using Recyclate. Over many years, an industry colleague and great contributor to RotoWorld®, Einar Voldner, wrote extensively about Recycling and Rotomolding, and many developments have occurred since then. Voldner said recycling is not easy for rotomolders. He said, “unlike other processes that force polyethylene into shape through heat and pressure, and thus blends recycled resins with relative ease, the ‘no shear’ aspect of rotomolding compels us to consider many more precautions and limitations”. Voldner said there are four reasons why a rotomolder would want to use recycled resins: 1) one’s environmental beliefs, 2) meeting customer’s requirements, 3) to satisfy laws/regulations, and 4) to save money. Voldner’s goal was to teach rotomolders how to make great products using recycled materials. He laid a foundation for that process by defining, in his terms, the following aspects of the process: Recyclable: This describes your ability to re-use a resin. In most cases, it means re-melting it, i.e., taking full advantage of the thermoplastic property of polyethylene. Thermoplastic products like rubber and cross-linked polyethylene cannot be re-melted, but they can be re-used as fillers and in some cases modifiers. So, in that sense they too are recyclable. Recycled: A recycled resin comes from any molded product that has reached the end of its useful life, whether a quality reject or a worn out bottle crate. Recycled content describes the percent by weight used in blending with virgin resins. Regrind: These are recycled resins that have been recovered from parts not shipped by the molder, usually for quality reasons. The resin has never seen use or outdoor exposure, i.e., it has only been molded. Post-Consumer (PCR): The original definition of this phrase included only those resins recovered from the post-consumer, i.e., household garbage stream: blow molded bottles – water, soft drinks, and laundry products. More recently this phrase has come to include a broader range of recycled products: the post-industrial stream from industrial products, which Voldner referred to as “PIR”. Dry Blending (PIR): When you mix two or more resins in powder form together you are dry blending. For simplicity, we limit the definition to the use of rotomolding with virgin resin (with a full complement of stabilizers) as a powder, blended with pulverized regrind, which has been recovered directly from your operation, granulated, and then pulverized. Neither PCR nor PIR should be used in dry blending. It is our plan to delve into a lot more information on Recycling and the Circular Economy through RotoWorld® in 2022 so stay tuned. To read Einar’s summary article on Recycling & Rotomolding, go to https://rotoworldmag.com/recycling-rotational-molding/.
Susan Gibson Publisher & Editor
8 ROTOWORLD® DECEMBER 2021-JANUARY 2022
