What is the casting molding process for ultra-soft TPE materials?

Did you know? Ultra-soft TPE (thermoplastic elastomer) materials typically refer to low-hardness elastomers with Shore A hardness ranging from 0 to 15A or even softer (such as 00 or 0000 grades). Due to their exceptional soft tactile feel, outstanding elasticity, and eco-friendly recyclability, they are widely used in adult products, medical devices, shock-absorbing pads, human body models, and other fields.

However, due to the extreme softness of these materials, traditional injection molding processes often encounter difficulties such as feeding issues, uneven plasticization, and sticking. Therefore, casting (pouring) molding has become the mainstream processing method for ultra-soft TPE materials. Next, the Zhongsu Wang editor will systematically introduce the casting molding process flow for ultra-soft TPE materials.

The casting molding process flow for ultra-soft TPE is here!

Material Preparation and Premixing

Formulation Design — Based on product requirements, mix SEBS powder/pellets with rubber oil and additives in specified proportions. Pellet materials mix uniformly and require no secondary stirring during melting; powder materials are lower cost but require stirring and are prone to bubbling.

Oil Pre-dispersion — Fully saturate SEBS with oil to form a pre-dispersed colloid. Oil saturation typically requires 2–7 days, depending on oil volume and SEBS characteristics.

Melting

Equipment — Electric kettles, dedicated melting machines, or screw-type heating devices are suitable, with precise temperature control being critical.

Temperature Control — Melting temperatures generally range from 130–200°C. Different molecular weight SEBS systems require distinct temperatures, necessitating gradual adjustment. Temperature fluctuations affect flow properties, product gloss, and transparency.

Bubble Elimination — Bubble formation is common during melting. Solutions include vacuum degassing, extended settling time, or optimized mixing techniques.

Casting (Injection)

Mold Preparation — Molds must be clean and smooth. Apply release agent as needed to prevent adhesion and ensure surface integrity.

Pouring Operation — Pour or spray molten TPE into the mold, taking care to avoid entrapping air. Design venting channels or incorporate auxiliary venting equipment.

Temperature Maintenance — Maintain stable melt temperature throughout pouring to ensure flowability and prevent cold-flow blockages or flow marks.

Cooling and Demolding

Natural Cooling — After pouring, allow the product to cool and cure naturally. Cooling time depends on product thickness and material properties.

Demolding — Remove the product from the mold only after it has cooled sufficiently to prevent deformation or surface damage caused by incomplete curing.

In summary, by scientifically controlling raw material ratios, temperatures, melt processing, and injection techniques, defects such as bubbles and flow lines in the injection molding of ultra-soft TPE materials can be effectively avoided. This process produces high-quality, safe ultra-soft products and is a crucial method for manufacturing ultra-soft elastomer items.