Arnitel TPE enables soft touch finish on polar thermoplastics

Polar engineering plastics e.g. PC, PBT, PC blends, ABS, etc are hard materials, selected for high quality applications because they exhibit excellent durability combined with high visual aesthetics. For design or ergonomic reasons, there is often a requirement to give a softer feel to the end product. Some of the most common thermoplastic elastomers, like TPV’s, SEBS, TPO’s, have poor adhesion to these engineering materials due to their non-polar nature. In the 90° peel test used to assess adhesion between two materials, a level of 1000 J/m2 is considered as the minimum adhesive strength required for most applications.

Arnitel TPE has a high affinity to the above polar engineering plastics, because of its chemical structure. Using the right molding conditions leads to very high bonding between e.g. Arnitel and PC or PBT, values up to 10,000J/m2 are typical.

For a soft touch finish, the first critical factor is the hardness of the material. Studies have shown that a materials with hardness < 30 Shore D give a more consistent perception of soft touch. Materials that are below this hardness threshold, dramatically increase the design freedom of designers and application engineers when developing a product. Arnitel EL250, a material with a Shore 25D hardness, provides a soft touch feel under the widest range of design factors. Further optimization in the touch sensation can be obtained by choosing the right texture, surface appearance, and part design.

These last named factors, can also play an important role in tactile perception.

1 Surface texture effects
Studies have shown that parts with a very smooth or very rough surface can be less suited to giving a soft tactile feel. A fine grained uniform texture, e.g. Sandtex MT11030 often gives best results.

2  Additives in the material
Additives that migrate to the surface and give surface lubrication can lead to a “harder” feel. A material with more surface friction gives a greater perception of a softer touch.

3 The object shape and dimensions.
The size and shape of a part affect the hardness perception in complex ways – this is highly subjective. Generally rounded, 3-D shapes tend to feel softer.

Arnitel offers excellent chemical and mechanical performance

Arnitel TPE has excellent resistance to hydrocarbons, oils, and alcohols and moderate resistance to hot water. It outperforms TPU and many commodity elastomers particularly when used in domestic, office and industrial environments. Arnitel EL250 can also withstand moderate dishwasher cycles, enabling its use in non-electrical consumer and kitchen appliances.

Advantages of Arnitel over other elastomers for 2K molding