IMPACT MODIFICATION | TECHNOLOGY
Making an impact
Whether for demanding automotive components or lightweight packaging items, many polymer applications call for improved impact performance. Mark Holmes examines developments
Plastics are noted for their durability, which is why they are used so successfully in such a wide variety of markets and applications. However, in-service performance can be limited by many physical attributes and impact resistance is high among them. Impact modification provides one solution, compensating for inherent brittleness, embrittle- ment at sub-zero temperatures, notch sensitivity or poor crack propagation characteristics. Typically, this is achieved by introduction of a secondary component that bonds mechanically or chemically with the primary polymer matrix and that acts to absorb or dissipate the energy of an impact. Kraton supplies a variety of styrenic block copolymer modifiers that can deliver the improved toughness required to achieve lighter and more durable product solutions in polymers including PS and polyolefins. “Impact modification is an impor- tant pillar in plastics modification but two others are equally important: excellent processing and modulus retention. Kraton has developed a broad product portfolio that successfully responds to
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these challenges,” says Bob Hall, Kraton’s Senior Director Global Marketing. They also address cost challenges. “Our poly-
mers are more efficient modifiers than polyolefin elastomers so they require lower dosing, which helps maintain modulus,” Hall claims. “In composite structures, the lower dosing allows customers to increase the level of reinforcing ingredients. In addition, our high flow grades – such as Kraton MD1653 or Kraton MD1648 – enable savings by reducing cycle time or enabling higher compound- ing throughput.” MD1653 is a developmental high flow SEBS grade suitable for food contact and medical applications. Application of Kraton’s modifiers is not restricted to commodity plastics. Its functionalised FG1901 grade, which has a PS content of 30%, improves impact properties and processability of semi-crystal- line polyamide (PPA) and polyphenylsulphide (PPS). Kraton says its impact modifiers can play a part in the development of sustainable “circular” com- pounds. “In the plastic recycling industry, our
Main image: Ever more demanding end-use applications call for plastic compounds with better impact
performance
April 2020 | COMPOUNDING WORLD 51
IMAGE: SHUTTERSTOCK
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