Extrusion Molding

Thermoplastic elastomer TPE, with its rubber-like elasticity and thermoplastic processing characteristics of plastics, is a commonly used soft rubber material for extrusion processes. It can continuously produce long-strip products such as cable sheaths, sealing strips, hoses, decorative profiles, and composite rubber-coated strips. Extrusion processing imposes strict requirements on the rheology, thermal stability, and melt strength of raw materials. Before production, drying pretreatment must be carried out according to the material type: SEBS, SBS, and TPV only need drying at 70°C for 2 hours in humid environments, while TPU, due to its strong hygroscopicity, must undergo dehumidifying drying at 85°C for 3 to 4 hours. Strict moisture control is necessary to avoid bubbles and silver streak defects in products.

The process uses a single-screw extruder with a length-to-diameter ratio of 20:1 to 25:1, with segmented temperature control based on TPE hardness and type. SEBS processing range is 150–195°C; SBS is overall reduced by 10–15°C to prevent high-temperature degradation; TPV and TPU processing temperatures are higher, at 190–210°C. The screw adopts a low-shear gradual structure, combined with reasonable back pressure to stabilize melt plasticization, maintaining head pressure at 5–15 MPa, and matching screw speeds of 30–150 rpm according to softness and hardness.

The molten material, after being extruded through a streamlined die, undergoes die swell and requires matching hauling with a draw ratio of 1.1–1.5, followed by cooling and shaping in a low-temperature water bath or vacuum calibration tank. For soft TPE, cooling water temperature is controlled at 15–25°C; for hard TPV and TPU, water temperature is raised to 30–40°C to ensure dimensional stability and prevent sticking.

Extruded TPE products offer high production efficiency, and offcuts can be recycled and reprocessed. They possess excellent resilience, abrasion resistance, and weather resistance. TPV products are often used for automotive sealing parts, SEBS products are suitable for daily-use soft rubber profiles, and TPU extruded parts focus on abrasion-resistant hydraulic hoses. During processing, issues such as shark skin, strip breakage, and dimensional fluctuations can be improved by adjusting temperature, screw speed, and hauling speed. Finished products require no vulcanization, the process flow is short, and overall costs are superior to traditional rubber extruded parts.