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People Basics Impact

People Basics Impact Modifier for PLA By: Kevin Ireland Communications Manager Green Dot Holdings LLC Cottonwood Falls, Kansas, USA TGreen Dot (Cottonwood Falls, Kansas, USA) recently presented data on the use of the company’s Terratek ® Flex compostable bioplastic elastomer as an impact modifier for PLA. Terratek Flex is shown to provide a significant increase in impact strength and elongation without compromising the compostability of PLA. PLA was first introduced to consumers in food service ware and packaging because it was known to be biodegradable in an industrial composting facility. Unfortunately, the impact strength and heat tolerance of the material is quite low, making it inadequate for more demanding applications. Consumers seeking compostable products made with PLA had to settle for forks that were easily broken or spoons that would distort in hot liquid. Moreover, these products and packaging materials often remained as waste because industrial composting facilities were not available to consumers. Plastic manufacturers are seeking a solution that can increase the toughness and durability of products made with PLA while enhancing the environmental benefits of compostability. There are many commercially available materials used as impact modifiers for PLA. Rubber resin blends that contain polybutadiene and acrylic can be chemically grafted with rigid phase polymers to compatibilize the rubber in the PLA matrix. Thermoplastic urethane elastomers with both polyether and polyester soft segments are quite compatible with PLA. Olefin elastomers like polybutadiene, ethylenepropylene, and EPDM elastomers can also be functionalized and blended with PLA. Unfortunately, these materials enhance the physical properties of PLA at the cost of compostability. Using Green Dot’s Terratek Flex compostable elastomeric bioplastic as an impact modifier for PLA has been shown to increase impact strength and flexibility while enhancing compostability. Terratek Flex is a proprietary patent pending starch-based compostable elastomer. It has been verified by SGS Fresenius Laboratories to meet ASTM D6400 and EN 13432 standards for biodegradability in an industrial composting facility and has been found to biodegrade in a backyardcomposting environment as well. Terratek Flex has been tested by NSF Laboratories and found to be safe from phthalates, bisphenol A, lead and cadmium. Green Dot’s Product Development Manager, Mike Parker, studied the use of Terratek Flex as an impact modifier for PLA. PLA was compounded with Terratek Flex at 10%, 20% and 30%. These samples were sent to an independent laboratory where they were molded and tested using ASTM standards. Notched Izod Pendulum Impact tests showed an incremental increase in impact strength at the 10% and 20% levels with greater 26 bioplastics MAGAZINE [06/13] Vol. 8

Politics Basics Percent Increase in Izod Properties 600% 500% 400% Notched Izod UN-Notched 300% 200% 100% 30% levels. Impact strength increased from 0.549 ftlb/in in the 10% sample to 0.66 ftlb/in in the 20% sample. Impact strength jumped to 1.82 ftlb/in for the 30% loading level. Unnotched Izod tests showed similar results. Tensile tests showed that strength and modulus properties declined at a proportional rate to be expected with the incorporation of an elastomer with a rigid polymer. However, elongation properties showed a similar trend to the results of the impact tests. The 10% and 20% samples showed elongation increased by 4.2% and 9.01% respectively. A more dramatic increase of 18.7% in elongation was observed at the 30% sample. Mike Parker summarized the results. “From 0% to 20%, the increase is very linear. After 20%, however, we see a much more exponential increase in the impact strength of both the notched and un-notched test results. Elongation properties have a similar curve. This feature allows the engineer to customize the properties of the final resin to their specifications and provides a certain degree of control to their cost to performance ratio.” Further study is needed to provide data on the effect of Terratek Flex on biodegradation rate of PLA. Because Terratek Flex has been verified to meet U.S. and European standards for biodegradation in an industrial composting facility and has also been found to biodegrade in backyard composting environments, it is hypothesized that the addition of the material as an impact modifier for PLA may increase the biodegradation rate as well. Now plastics processors can enhance the physical properties of PLA without sacrificing environmental performance, expanding the range of product applications and opening new markets for bioplastics made with PLA. Green Dot’s product development lab can quickly and effectively provide customized formulations designed to exact customer specifications. Using a pilot scale extruder, sample quantities of material can be efficiently produced for processing and testing to assure desired results. Green Dot’s team of plastics professionals work with OEMs and plastics processors, from material selection to mold design and throughout the manufacturing process, to create products that help consumers contribute to a more sustainable world. 0% 0 5 10 15 20 25 30 35 Percent GDH-B1 Added Notched Izod pendulum impact test Tensile Strength peak psi 9855 PLA 00 525691 8368 Tensile Modulus peak psi PLA 00 PLA 10 Tensile Strength 3.5 468712 Percent Elongation 4.22 6905 PLA 10 PLA 20 411585 PLA 20 9.01 18.7 326792 5552 PLA 30 PLA 20 PLA 00 PLA 10 PLA 20 Elongation properties PLA 20 bioplastics MAGAZINE [06/13] Vol. 8 27

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