Advantages of TPE overmolding and key points of production process

  • Time of issue:2023-04-15
  • Views:0

Advantages of TPE overmolding and key points of production process

  • Categories:Elastomer knowledge
  • Author:SPP
  • Time of issue:2023-04-15
  • Views:0

  The elastomer industry commonly refers to TPEs as SEBS modified by a composite functional material. TPE elastomers have excellent overall properties and are soft materials used in molding and two-color injection molding processes.

  1. The main advantages of TPE for overmolding

  1.As TPE material has good anti-slip property and good elasticity, it can enhance the touch feeling of the product and is good for grip.

  2.TPE can be adjusted to suitable hardness (hardness range Shore 25-90A) and appropriate physical properties (such as abrasion resistance, adhesion, melt index, etc.). Depending on the product properties, various possible material applications are available for various products.

  3. TPE is overmolded and processed and is commonly used for handles, grips, electronics and other products. This material gives the product a comfortable touch, enhanced grip, enhanced product aesthetics and added value. Most of the products are exported to developed countries and regions, such as the United States, Japan and the European Union. TPE elastomer is soft and green material, the material does not contain phthalates, does not contain halogens, meets ROHS environmental testing standards, and can fully meet the environmental requirements of developed countries and regions, such as the United States, Japan, and the European Union.

  2.Common TPE molding material

  TPE can be used for overmolding and two-color injection molding. TPE is a soft material, usually matched with rigid materials, mainly plastic, metal and fabric. TPE + fabric is mainly used for luggage products. This process is the same as metal overmolding and is usually pseudo overmolding. True overmolding is more common in secondary and two-color injection molding. TPE can be firmly bonded to a number of commonly used plastics PP, GPPS, HIPS, ABS and engineering plastics PC, PC/ABS, PA and their modifications. In the current elastomer industry, adhesion of TPE and POM is still a problem. Since the solubility parameter SP of POM (22.6) is very different from SP of TPE (7.2-7.6), the two materials are incompatible with each other and no suitable bulking agent has been found to promote the adhesion of the two materials.

  3. Problems to be noted in TPE rubber injection molding

  ● Compatibility of TPE and hard plastic components, solubility is close to molecular compatibility.

  ● Avoid sharp corners in the design to ensure good contact between TPE and hard plastic to enhance the bonding effect.

  ●Correct setting of cavity exhaust port.

  ● Balance the thickness of TPE with the expected touch.

  ●Maintain the TPE melting temperature to ensure the bonding effect.

  ●The TPE should be dried to reduce surface water accumulation and obtain a uniform surface color.

  ●The carrier resin of masterbatch is compatible with TPE and structural material.

  ●Smooth surface with special treatment to increase the adhesion of soft and hard material bonding surface and enhance the bonding effect.

  ●TPE should have good flowability, TPE molding thickness and size ratio is very small, TPE usually need to flow through long path and thin wall area to fill the mold.

  ● TPE flow length/product thickness ratio is less than 150:1.

  ● Use good adhesives.

  4. Common adhesive defect handling

  Defective material: Increase injection temperature; Increase injection pressure and improve material flow.

  Splitting, overflowing edges: lower injection temperature; increase clamping pressure; lower injection pressure; lower flow from formulation point of view.

  Lusterless and unshiny surface: it increases the temperature of the injection process; it dries the material and reduces the moisture content of the raw material.

  Poor viscosity: bake completely before injection; increase the injection temperature; adjust the formulation.

  Product injection deformation: strengthen the mold cooling; extend the pressure holding time appropriately.

  Product adhesion: add mold release agent or lubricant (internal lubricant - mold release agent should pay attention to the amount added to prevent the mold release agent from settling and falling off).

  5. Experience sharing

  1. Proper injection temperature, encapsulated nylon, TPE injection temperature is preferably higher than 190℃, but not higher than 240℃. In particular, in order to obtain the true encapsulation molding effect, due to the softening temperature for nylon is 250-260 ℃, in TPE conditions will not degrade, the closer the softening temperature of TPE and nylon, the better the bonding effect.

  2. Product bonding structure design, as far as possible to achieve smooth size, no obvious edges, increase the TPE and nylon hard plastic close contact.

  3. Make some holes in some non-critical positions of nylon, or make some non-smooth surfaces to increase the contact area of TPE and nylon, and make TPE soft material embedded in the holes by embedding nylon material.

  4. For newly manufactured molds, pay attention to the gate and sprue design of the mold. The TPE coating is usually very thin, the thickness is usually 1-2mm, and the size of the mold part is usually tens or even hundreds of millimeters. It must be ensured that the TPE soft plastic can fill the cavity without missing material and ensure the adhesion of TPE and nylon.

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