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Operating Procedure of Plastic Extrusion Equipment

Time：

2018-11-24

The principle of a plastic extruder is that solid plastic, under the combined action of heating and screw rotation, melts and becomes plasticized, while a continuous plastic product with a cross-section and shape identical to the die is formed by the die. The specific shape is determined by the die. Manufacturing materials mainly include carbon structural steel and alloy tool steels; some extrusion dies also incorporate wear-resistant materials, such as diamond, in parts requiring enhanced abrasion resistance. Extrusion processes are typically used for producing thermoplastic products and differ structurally from injection molds and compression molds. Foam extrusion: thermoplastic elastomers (TPVs) can be foamed using both chemical and mechanical methods. For chemical foaming, blowing agents such as sodium bicarbonate may be employed.

The principle of a plastic extruder is that solid plastic, under the combined action of heating and screw rotation, melts and becomes plasticized, and a continuous plastic product with a cross-section and shape identical to that of the die is formed by the die. The specific shape is determined by the die. Manufacturing materials primarily include carbon structural steel and alloy tool steels; some extrusion dies also incorporate wear‑resistant materials, such as diamond, in parts requiring enhanced abrasion resistance. Extrusion processes are typically used for producing thermoplastic products and differ structurally from injection molds and compression molds.

Foam extrusion: Thermoplastic vulcanizates (TPVs) can be foamed using both chemical and mechanical methods. For chemical foaming, blowing agents such as sodium bicarbonate are employed. Achievable foam densities range from 0.97 (typical for unfoamed TPV) down to 0.70 or lower. The blowing agent decomposes at temperatures between 180°C and 190°C, whereas most TPVs are processed in the range of 195°C to 215°C.

Multi-layer extrusion: Co-extrusion is a technique in which two materials are combined into a single component during a single extrusion process. Two extruders are connected in series to supply the base material and co-extrude the respective polymer materials through their corresponding channels, resulting in an extruded composite of the two materials. Homogeneous materials such as TPV and polypropylene can be fused together.

Multi-layer extrusion is an effective method for combining rigid and flexible materials. Typically, a high‑hardness component—such as a thermoplastic elastomer (TPV)—is used as the structural support, while a lower‑hardness material provides flexibility. This arrangement is common in sealing applications, where the sealing zone is soft and can deform to achieve a tight seal. When balancing the flow field, it is straightforward to employ a higher‑hardness TPV as the rigid material instead of polypropylene.

Welded Joints: Heat welding is a common method for joining extruded gels made from TPV. Heat is applied to the mating surfaces to melt them, after which the surfaces are bonded together under slight pressure to ensure no air enters the interface. Upon cooling, the joint’s strength is essentially equivalent to that of the component itself. Another approach for joining extruded parts is to use an adhesive system.