TPE,TPR injection molded rubber material and vulcanized rubber covered metal process shallow analysis

  • Time of issue:2022-08-26
  • Views:378

TPE,TPR injection molded rubber material and vulcanized rubber covered metal process shallow analysis

  • Categories:Elastomer knowledge
  • Author:SPP
  • Time of issue:2022-08-26
  • Views:378

  Rubber covered metal, which is used in some hardware and tool parts is common. However, as conventional rubber are required to master refining - mixing - preforming - vulcanization, the processing process is too cumbersome and the cycle is long, if alternative materials can be used and different processing methods can be adopted, it will be beneficial to reduce cost and improve production efficiency and profit.

  At present, the industry intends to try to use injection moldable rubber characteristic materials to replace vulcanized rubber. Injection molded rubber material instead of vulcanized rubber, covered with metal, although it can improve processing efficiency, but need to consider two aspects, one is the package adhesive solidity, the second is the material properties.

  A. Adhesive bonding firmness

  Vulcanized rubber clad metal, rubber and metal does not exist between the chemical level of molecular bonding, there is no physical level of compatibility between the two different materials. Usually is coated with a suitable adhesive on the surface of the metal parts, the pre-formed rubber parts (Figure 1, the process differences between rubber injection molding and traditional vulcanization) and metal parts bonded together. Then it is put into the mold and vulcanized. Vulcanized rubber overmolded metal, due to the use of glue bonding, is able to achieve a solid covering of metal parts of various surface shapes.

  If injection is used to mold the rubber material, there may be two types of rubber materials, one is still the traditional rubber material (to be vulcanized), except that a special rubber injection machine (see Figure 2 below) is used to extrude the rubber directly into a strip, feed it into the rubber injection machine, and inject it into the mold to complete the vulcanization. The other type uses granular injection rubber material (usually TPE\TPR or TPU\TPV), which is molded with a conventional injection molding machine. Whether it is the first injection (vulcanized) rubber or the second injection molding rubber material TPE, compared with the conventional rubber preform and metal parts first bonded, and then placed into the mold static vulcanization, the use of metal parts coated with adhesive, to carry out the cladding bonding, for this dynamic injection molding, the operational feasibility is much smaller.

  For dynamic injection molding of rubber material, the rubber material is usually wrapped directly on the surface of the metal parts, but because the rubber material (whether it is vulcanized rubber or TPE, TPR, TPV, TPU and other thermoplastic rubber) and the metal parts do not have the above physical and chemical bonding feasibility. Therefore, the injection rubber material and metal parts are only based on the physical structure of the wrapping and adhesion of the parts.

  Second, the material performance

  Although injection rubber material (TPE, TPR) is easier to process than vulcanized rubber, but the physical and mechanical properties of the former, such as resilience, wear resistance, tear resistance, high temperature resistance, corrosion resistance, weather resistance, etc. are not as good as the latter. When doing the replacement of materials, an assessment should be made first. Then determine whether to replace the material, equipment and processing methods.

  As the microstructure of rubber material and metal is very different, there is no possibility of physical compatibility between the two materials. As for the chemical level, some R&D engineers believe that for metals with certain chemical activity (such as activity before hydrogen), it may be possible to do polar processing of the rubber compounding system, so that the metal and the rubber material can chemically react at the cladding interface, thus enhancing the solidity of the cladding adhesion. However, the maturity of the technology has yet to be verified in the market.


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