Wacker: Silicone-based additives for TPUs

The silicone specialist Wacker will be introducing at K 2019 a silicone-based additive for thermoplastic elastomers, especially thermoplastic polyurethanes. The additive is said to lower the hardness of TPUs, while boosting their elasticity and enhancing their properties. The surfaces of moulded parts modified with the additive are pleasantly soft to the touch and more resistant to scratches, abrasion and contamination.

Wacker, the Munich-based chemical company, will showcase a new silicone additive for thermoplastic polyurethanes at K 2019. Sold under the brand name Genioplast Pellet 345, the new additive is readily incorporated into thermoplastic polyurethanes and has fewer undesirable secondary effects than conventional silicone products.

The silicone additive Genioplast Pellet 345 lowers the hardness of articles made from
thermoplastic polyurethane elastomers while simultaneously boosting the surface properties. The articles can be given a silky-soft surface that additionally offers greater resistance to abrasion and contamination. (Source: Wacker)

Genioplast Pellet 345 complements Wacker’s portfolio of silicone-based additives for the compounding of thermoplastic polymers. The product has been specifically developed with thermoplastic polyurethanes in mind, but can be used for modifying other thermoplastic elastomers as well. For example, the product, which is supplied in pellet form, can markedly boost the properties of thermoplastic polyamide and copolyester elastomers.

Genioplast Pellet 345 is a silicone copolymer and is processed like a thermoplastic. Organic polymer segments contained within the product make it so compatible with thermoplastic polyurethanes that, unlike conventional silicones, it disperses very finely and homogeneously throughout the polyurethane matrix. The copolymer becomes physically bound to the matrix and is therefore unable to migrate. In Europe, Genioplast Pellet 345 is authorized for foodcontact applications.

Adding the silicone-based additive boosts the surface smoothness of thermoplastic polyurethanes, thereby enhancing their scratch and abrasion resistance. Moreover, surfaces become more resistant to contamination by foodstuffs and cosmetics. These effects are achieved at additions of just 3 to 5 %, said the company. Adding more than 10 % to a thermoplastic polyurethane elastomer affects its hardness and mechanical properties, rendering it softer and more elastic. For every 10 % rise in amount added, the hardness drops by roughly 5 points on the Shore A scale. As the polymer softens, it necessarily loses some of its mechanical strength. However, this undesirable secondary effect is less pronounced with Genioplast Pellet 345 than with other silicone-based technologies routinely used to soften TPU polymers.

Surface test of a TPU part modified with Genioplast Pellet 345. The new silicone additive boosts the surface smoothness of TPUs, thereby enhancing their scratch and abrasion resistance. Moreover, surfaces become more resistant to contamination by foodstuffs and cosmetics. (Source: Wacker)

A characteristic feature of articles made with blends of TPU and the new additive is a silky-soft surface with a dry feel. This is precisely the type of surface which end users expect of articles which they frequently touch or wear against the skin.

The additive pellets are easy to meter, and incorporating them into thermoplastic polyurethanes on conventional compounding extruders is straightforward. The resulting compounds can then be injection moulded and extruded to parts and film respectively. The compounds also lend themselves to two-component injection moulding because the additive does not interfere with the good adhesion properties of the polymer. This means it is possible to cost-effectively produce hard/soft combinations in which the soft component has a particularly pleasant feel.

By virtue of this property set, Genioplast Pellet 345 has extended the range of applications for thermoplastic polyurethanes. There is huge demand in the consumer, microelectronics and sports equipment sectors for moulded TPU parts that have a pleasant feel and retain their looks upon protracted use. Typical examples are wrist-straps for smart-watches and other wearables, smartphone covers that resist abrasion and discolouration, and soft grips for sports equipment and tools.

More new products at the 300 sqm stand of Wacker in hall 6 will be fire-resistant silicone elastomers, self-adhesive silicone rubber grades with extremely low-friction surfaces and ultrathin silicone laminates for electroactive applications. The company announced that another focus will be on liquid silicone rubber grades that, thanks to their reduced volatiles content, do not necessarily require postcuring. In the field of 3D printing Wacker will show the new 3D silicone printer Aceo Imagine Series K2.


Wacker at K 2019, hall 6, stand A10