Detailed explanation of the reasons for the rupture of TPE covered PC

  • Time of issue:2023-05-19
  • Views:637

Detailed explanation of the reasons for the rupture of TPE covered PC

  • Categories:Elastomer knowledge
  • Author:SPP
  • Time of issue:2023-05-19
  • Views:637

  Overmolded PC, ABS series TPE, can be second injection bonded with ABS, PC and PC/ABS alloy and other base materials overmolded. Bonding series products can be substituted with PC, such as Tritan

  PCTG, PETG, cellulose acetate, etc. with good bonding effect, high peel strength, excellent temperature resistance, weathering and aging resistance.

  "TPE wrapped PC rupture" is a headache for manufacturers, but this problem is still very good solution if analyzed thoroughly, first we need to figure out whether the TPE wrapped part of the rupture or PC part of the rupture?

  1.TPE/TPR cladding layer cracking

  TPE wrapping PC, TPE wrapping layer rupture (crack), this situation, usually in the wrapping molding after a period of time, the reason for the TPE crack, mainly TPE aging resistance is poor, over time, the material aging cracking.

  Countermeasures: Use TPE product grades with excellent aging resistance to enhance the aging cracking resistance of the material.

  2. Cracking of PC parts (rupture)

  People who are familiar with engineering plastics must know that the problem of PC (polycarbonate) cracking is very common. PC parts are prone to the problem of cracking, mainly due to the internal stress of the parts.

  The forced molecular orientation of PC material occurs during molding, but after the molding is cooled, it is very difficult to unorient the molecules due to the existence of a poorly flexible benzene ring structure.

  Therefore, PC parts in molding, unorientation measures are not handled properly, such as mold temperature setting is low, cooling pressure time is not enough, etc., can not let the molecules to fully relax and unorientation, the molding products will exist after the internal stress, when the internal stress reaches a certain level (greater than when the cracking force), PC parts will occur cracks.

  When TPE secondary injection molding overmolded PC parts, due to the existence of large internal stresses inside the PC parts, the destructive effect of this internal stress is just revealed when overmolded TPE. Or in the TPE wrapping, TPE wrapping part of a larger area, in the wrapping molding TPE cladding layer will shrink, while the thickness of the PC parts and thin, the shrinkage of the TPE cladding layer will play a role in the role of internal stress, thus leading to the PC parts cracking.

  Countermeasures: Try to use high mold temperature when molding PC parts, and appropriately extend the pressure-holding and molding cooling time to minimize or eliminate the internal stress.

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