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Recent content by edine

  1. edine

    Rubber injection molding questions

    Welcome to the wonderful world of rubber.
  2. edine

    Material Properties

    Right now the rubber industry is being plagued by raw material discontinuations and processing location changes. It may be that your mixer or his supplier is having supply issues or has made changes. If this is a new job, consider that you may not have seen all the ups and downs of normal...
  3. edine

    State of cure - quick test

    If you think it is a problem with temperature fluctuations in the production equipment, you need to figure out how far out of operating parameters it was. If it isn't very far than you need to look for ways to make the process more robust (slow the line, bump up the temperature, get better...
  4. edine

    Mineral bonding rubber?

    You should pick you rubber based on the application that it will be used in, then figure out an adhesive. Chemlok is good, but Thixon and Megum are also tradenames to look for. You can either post bond after molding or bond during the molding process.
  5. edine

    Undercure Rubber - Molding Tool

    Unless this is a really large o-ring is it unlikely to be undercured in just one spot. Without a picture, I suspect what you have is air trap with a bubbly ugly lump that left gunk in the tool. Inject time and/or speed changes can help as can adding vacuum. On thing to be careful with molding NR...
  6. edine

    Clean out material for injection rubber press

    Purging with the new material usually works although it can be difficult when going from a hard to a soft compound. The problem is knowing for sure the unit is clean; it depend s on how critical it is. I have used uncured natural rubber cleanouts and EPDM cleanouts for critical jobs. No matter...
  7. edine

    Bloomed chemicals?

    Most NBR compounds are sulfur cured. The bloom is likely a combination of accelerator fragments, but may contain just free sulfur. You didn't give too much detail so it is a little hard to tell if you are a molder or an end user. Bloom is basically a solubility issue. This could be just normal...
  8. edine

    Epoxy Bond Failures to Matte Tin Plate

    This is a new supplier and I am unsure how different the process may be than the incumbant. Prior to this we have always been able to bond well with an alcohol wipe. Wiping with acetone did not help much. Caustic cleaning is out of the question for this plant, but I will check on what the plater...
  9. edine

    Accelerating blooming in EPDM material

    Hanging parts in a warm humid spot sometimes accelerates blooming. I am surprised you have a problem with peroxide cured material. Blooming in peroxide cures is seldom a curative by-product unless there is something leftover from a switch from sulfur to peroxide. Other materials like wax...
  10. edine

    Thick Section Rubber Molding

    Large thick sections often require lower temperature and slower cures. Lower temperature give you a longer time before reversion occurs. You need really good packing, but the rubber can't be moving out the overflows once it has started to crosslink. Make sure you are getting enough cure in the...
  11. edine

    Epoxy Bond Failures to Matte Tin Plate

    We are having matte tin plated over brass. There parts are subsequently bonded using an epoxy adhesive. This process has been working successfully for years. We are starting production at another location which means a change in plating suppliers. The last lot did not bond at all. Cleaning with...
  12. edine

    Paint-on Coating to Identify Stainless Steel

    That sure sounds like the test except I was told the liquid was clear, not blue. Hopefully tomorrow I will get more feedback. One can only hope they have not been using a bottle of 6 year old solution for this test. Thanks.
  13. edine

    Paint-on Coating to Identify Stainless Steel

    My lab has been approached by one of our vendors for a coating that when painted onto stainless remains clear and turns a coppery color for other steel grades. They had some, but lost the bottle. Anybody ever hear of something like this?
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