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bioplasticsMAGAZINE_1303

PLA Recycling Linear

PLA Recycling Linear polymer Better-than-virgin recycled PLA Chain extended polymer (PLA + chain extender by reactive extrusion) Ex: CESA-Extend, Joncryl, other epoxides Hyperbranched PLA (PLA + IFS Proprietary Chemistry by Reactive Extrusion) Top: PLA extrudate from a cast film process at 180°C, bottom: hyperbranched PLA, Interfacial Solutions LLC (River Falls, Wisconsin, USA) has developed proprietary processing technology that converts scrap PLA, possessing inferior properties, into a recycled PLA resin with properties that exceed those of virgin PLA. To do so, Interfacial Solutions utilizes a novel reactive extrusion process and chemistry to hyperbranch PLA polymer within a continuous extrusion process. Interfacial Solutions has shown that hyperbranching dramatically increases the molecular weight of the polymer while simultaneously creating many random branching sites along the backbone of PLA, creating a unique rheology during melt processing. The result is an improved PLA resin with superior melt strength and mechanical properties to virgin PLA. The hyperbranched recycled PLA resins are particularly suited for profile extrusion applications in durables markets. PLA itself is a linear polymer with low melt viscosity, and as a consequence, does not exhibit substantial melt strength during processing. Branching of PLA through chain extension chemistries has been shown to improve melt strength, however, these chemistries work only on the chain ends of the polymer. Hyperbranching produces a unique molecular architecture from many random long and short chain branching events. This molecular architecture allows for improved melt processing compared to both linear and conventional chain extension by providing substantial melt strength enhancement, but at lower shear viscosity in the melt [1]. In other words, profile control of the extrudate can be dramatically enhanced without large increases in die pressure and torque on extrusion equipment. An additional benefit to hyperbranching is that the increased molecular weight of the polymer makes PLA less susceptible to processing variations caused by moisture. It is well known that moisture in PLA resin during processing creates process instabilities due to hydrolysis of the PLA polymer at elevated temperature. The significantly greater molecular weight and branched structure of hyperbranched PLA makes for a lesser impact of hydrolysis. From the perspective of recycling PLA through the reactive extrusion process, the incoming scrap PLA feedstocks do not require drying to the levels recommended by users of prime PLA grades. It is possible to counteract the hydrolysis caused by moisture with adjustments to the chemistry used in the reactive extrusion process, effectively allowing repeated melt processing without drying. Interfacial Solutions’ proprietary technology was originally developed to enhance the performance of compounds produced from virgin. Through a prestigious grant from the Na- 50 bioplastics MAGAZINE [03/13] Vol. 8

PLA Recycling by Adam R. Pawloski, Brandon J. Cernohous Gregg S. Bennett, Jeff J. Cernohous Interfacial Solutions / River Falls, Wisconsin, USA tional Science Foundations Small Business Innovation Research (SBIR) program (Grant No. IIP-1215292), Interfacial Solutions expanded the technology to make it amenable to recycling processes by converting low quality PLA scrap into hyperbranched, recycled PLA resins of greatly improved mechanical and rheological properties. As demonstrated by the data in Table 1, even very poor quality scrap can be effectively converted into hyperbranched resins with better-than-virgin properties. The technology works effectively on both post-industrial and post-consumer scrap, allowing for multiple options of source materials. Products based on hyperbracnehd, recycled PLA are available for purchase under the deTerra ® product line. www.interfacialsolutions.com [1] Pawloski, A. R. et al., “Recycled PLA Feedstocks by Hyperbranching,” Global Plastics Environmental Conference (GPEC), New Orleans, 2013. Examples of molded and extruded articles made from deTerra ® biobased polymer Resin MFI (g/10min, 190°C, 2.16 kg) Mw (kg/mol) Flexural Strength (kpsi) Virgin PLA (NatureWorks 2003D) 6.0 220 155 Hyperbranched, virgin PLA (XP759) 2.7 425 156 Prime Grade Post-industrial PLA 11.8 145 153 Low level hyperbranching 6.8 142 153 Intermediate level hyperbranching 3.2 464 155 High level hyperbranching 1.6 470 155 Low Grade Post-Industrial PLA 420.0 108 64 Low level hyperbranching 285.0 125 98 Intermediate level hyperbranching 290.0 145 122 High level hyperbranching 130.0 300 135 Post-Consumer PLA 5.0 187 145 Low level hyperbranching 0.8 398 141 Intermediate level hyperbranching 0.3 518 145 High level hyperbranching 0.0 --- 149 Table 1. MFI, Molecular Weight, and Flexural Strength of Hyperbranched, Recycled PLA Resins ‘Basics‘ book on bioplastics This book, created and published by Polymedia Publisher, maker of bioplastics MAGAZINE is available in English and German language. The book is intended to offer a rapid and uncomplicated introduction into the subject of bioplastics, and is aimed at all interested readers, in particular those who have not yet had the opportunity to dig deeply into the subject, such as students or those just joining this industry, and lay readers. It gives an introduction to plastics and bioplastics, explains which renewable resources can be used to produce bioplastics, what types of bioplastic exist, and which ones are already on the market. Further aspects, such as market development, the agricultural land required, and waste disposal, are also examined. An extensive index allows the reader to find specific aspects quickly, and is complemented by a comprehensive literature list and a guide to sources of additional information on the Internet. The author Michael Thielen is editor and publisher bioplastics MAGAZINE. He is a qualified machinery design engineer with a degree in plastics technology from the RWTH University in Aachen. He has written several books on the subject of blowmoulding technology and disseminated his knowledge of plastics in numerous presentations, seminars, guest lectures and teaching assignments. 110 pages full color, paperback ISBN 978-3-9814981-1-0: Bioplastics ISBN 978-3-9814981-0-3: Biokunststoffe Order now for € 18.65 or US-$ 25.00 (+ VAT where applicable, plus shipping and handling, ask for details) order at www.bioplasticsmagazine.de/books, by phone +49 2161 6884463 or by e-mail books@bioplasticsmagazine.com Or subscribe and get it as a free gift (see page 69 for details, outside German y only) bioplastics MAGAZINE [03/13] Vol. 8 51

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