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Thread: Ball Mill Problem

  1. #1
    freebird Guest

    Ball Mill Problem

    Dear All,

    I'm using a simple roll ball mill (Pascal Engineering Co. UK) to reduce the powder size and mix two types of powders at the same time. The following is my material and processing specifications:
    Material:
    (1) Ultrahigh Molecular Weight Polyethylene (UHMWPE) Powder
    Particle size: D50=300 micron
    (2) Hydroxyapatite (HA) Powder
    Particle size: D50=5 micron

    Processing:
    (1) Since the UHMWPE powder is very difficult to break, liquid nitrogen is used to help break the particle (the glass transition temperature of UHMWPE is around -120 Celsius degree).
    (2) Milling media is stainless steel ball of diameter 1/2 inch with high hardness.
    (3) Fractional ball filling is 25%, and fractional powder filling is 4% and hence the powder loading ratio is 0.5.
    (4) The powders are premixed and then milled at the critical rotation of speed in liquid nitrogen for about 1 hour.

    Problems:
    (1) Since HA is a polar (OH) matter, and the specific surface area is very large, the particle agglomeration effect is very signifaicant. To hinder it, I tried to add some dispersant and milling the slurry in an alkalescent environment. Unfortunately, the ball mill chamber is made up of steel, so it will corrupt. Is there any method to avoid this happen?
    (2) The size reduction of UHMWPE powder is very limited after ball milled for one hour in LN2, I wonder how long it will reduce to 50 microns, or does anyone has experience in reducing ductile polymer resin?
    (3) Is there any good method to mix powders homogenously excluding ball mill?

    Your suggestion or comment is highly appreciated.

  2. I can't understand from your description if you are milling wet or dry. Probably dry in reference to LN2.
    I believe that the size of the media is large for the particle size reduction you want. I think that even 1/4" media would be too large. However without details of the milling system is difficult to give good advice and you should get a few more opinions.
    Antonio Reis
    www.vitrom.com

  3. #3
    Dear freebird,
    did You find a solution to Your milling-problem with UHMW-PE?
    I´ve got an similar Problem of milling UHMW-PE to a very fine powder with a size smaller 1 micron.
    Do You see any possibility of reaching this aim?

    Your suggestion or comment is highly appreciated.

  4. #4
    disl_se_reeeeee Guest

    hydroxyapatite

    hi,
    i'm doing ballmilling of calcium hydroxide and tri calcium phosphate to produce HAP. but my problem is agglomeration of powder.is there anyone to give name of some dispersant which i can use to prevent agglomeration.

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