ADDITIVES | IMPACT MODIFIERS


Table 1 and 2: Impact test results for Elastron D400 at -15°C and 23°C for recycled PP and recycled HIPS compounds


Source: Elastron


for compounds containing mineral fillers such as ATH and MDH halogen free flame retardants. Olebond 7404 and 7405 are ABS and EVA based


grades for used as compatibilisers and coupling agents for use with filled and fibre reinforced immiscible polymer systems based on PA or PC.


TPEs for impact Sustainability concerns are becoming increasingly evident in the area of impact modification. “The demand for products made from recycled materials is rising, meaning that recyclability of polymers is becoming increasingly important,” says Martin Bradbury, Dryflex TPE Impact Modifiers Expert at Hexpol TPE. “However, thermomechanical degra- dation from repeated melting during the recycling process, weathering and contamination can all have negative effects on properties and performance.” Bradbury says Dryflex TPEs have long been used as impact modifiers and, when added to recyclate, can “help transform” properties. Dryflex impact modifiers can be added to the recyclate, helping to transform the properties from stiff and brittle to flexible and tough and improve the impact resistance and aesthetics of the finished product. Hexpol TPE says the materials are being used as impact modifiers in both primary and secondary recyclate supply streams. Dryflex TPE impact modifiers can also function as a compatibiliser when used with commingled sources of polar and non-polar polymers such as PP, PE and PS. Added to an immiscible polymer blend, the TPE modifies interfacial properties and stabilises the morphology to create a polymer alloy and to improve the dispersion and processing characteristics. Depending on the purity of the recycled polymer feedstock, the company says addition of Dryflex TPE can also help to improve


30 COMPOUNDING WORLD | April 2021


melt viscosity, aid processing and reduce cycle times. In comparison to pure PS, the introduction of Dryflex TPE impact modifiers can also improve the ease of de-moulding injection moulded parts. “In the past we have seen a rather inconsistent


approach to impact modification, where any available compounds or polymers are thrown into the recyclate mix. This can lead to inconsistencies and unpredictable results. With our Dryflex TPE impact modifier grades we have adopted a more qualified approach,” says Bradbury. “We have tested many different formulations with both virgin and recycled polymer for impact strength and have also compared these results against data collated from common materials used in the industry such as pure SBS. The Dryflex TPE impact modifier grades help to increase the value, processability and potential applications for recovered PP and PS,” he adds. Hexpol recommends adding Dryflex TPE impact modifier grades at loadings by weight of between 5 and 25%. For example, in a grade of PS regrind, it reports that a 15% addition of Dryflex TPE results in a 160% increase in notched Charpy impact resistance. In a virgin crystal polystyrene, a 25% addition gave an increase of more than 430%. Turkish compounder Elastron also has TPE


grades for modifying impact performance of various thermoplastics, including virgin and recycled polyolefins and styrenics as well as PA and PC. “Elastron has developed a broad range of SEBS, SBS and TPO-based TPE modifiers that can improve impact resistance, elasticity, and mechani- cal properties across a broad temperature range,” says Jon Wise, who is responsible for the compa- ny’s marketing activity in the US. “Elastron tests show the potential for notable improvement in impact performance through


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