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Thread: Rubber Matt has Hazy Areas

  1. #1

    Rubber Matt has Hazy Areas

    Help,

    I have had a few of these rubber matts, and I always fight appearance issues... this one in no different.... Front of parts show ghosting or hazy areas in same spots every time. See picture of worst case.

    Matl is TPV.... (very similar to TPE in my opinion and I am not sure the difference to be honest.)

    This is an automotive rubber mat to be placed at the bottom of a console/ coin compartment, the longest dimension is about 5 inches.

    4 cavity family mold, all have same appearance issue
    Tunnel gated.
    Fast fill improves the appearance, but does not eliminate.

    Anybody know a way to make them look perfect, like our customer wants?

    thx,
    Joel
    Attached Thumbnails Attached Thumbnails mattbetter.jpg  

  2. #2
    Join Date
    Aug 2014
    Location
    Saint Paul, MN
    Posts
    135

    Re: Rubber Matt has Hazy Areas

    I'm not familiar with TPV but my first thought would be to treat it like any other filled material: raise the mold temp (& possibly melt temp) to try to get a resin-rich surface. Alternatively, if the parts start off looking good and get progressively worse during the run, you may have some additive plating out on the mold surface, which is a lot harder to deal with.

  3. #3

    Re: Rubber Matt has Hazy Areas

    Thanks JayDub,

    I actually had tried the other direction and it helped..... my thinking was the hazy areas were trapped gas on the surface, so I lowered all the barrel heats as low as possible to reduce material gas....... it helped somewhat.... also to note the start up parts look the exactly the same....... but after it ran an hour, the parts then actually looked slightly better.. also as stated filling fast makes them look better, and I like to think of it as "dispersing the gas", but this material is always so difficult to process and understand, I can't be sure.... so, now the parts look much improved from tool shop parts (I like them!), but still not perfect, so I am sure the customer will not like them

    Thanks again,
    Joel

  4. #4
    Join Date
    Oct 2018
    Posts
    5

    Re: Rubber Matt has Hazy Areas

    Can you stage clamp pressure during injection? Start out low and ramp it up?
    If not, maybe try reducing clamp pressure.
    You might also try slow inj speed at beginning and speed it up near end of fill.

  5. #5
    Join Date
    Aug 2011
    Location
    Upstate of South Carolina
    Posts
    597

    Re: Rubber Matt has Hazy Areas

    I see that your losing melt pressure on the resin and getting back filling in that area. Warm mold up, lower clamp and increase vents on the entire part; then shot as fast as possible ! TPV means there’s some cross linking or vulcanizing happening with the resin. A resin change to a resin made for such parts would make your life easier. I imagine it’s Santoprene resin. A Pibiflex or Kraiburg resin would run/look much better.
    Rick

  6. #6

    Re: Rubber Matt has Hazy Areas

    Thanks Rick and Doug!

    Will take these ideas into my next battle.

    Joel

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