It depends on the hardness of the polmyer. Rigid polymers can be milled by ball milling or other devices if the system is cooled. Best practice is, however is to use cryogenic milling, although it require special apparatus. If the polymer is soluble, you may aoos prepare polmyer powder by dissolving and precipitaton - but it removes the additives (especially anitoixdiatnt, heat stabilizers etc.). You may alos try to buy polymer powder directly which are youed for powder coating. Some polymers are also produced in powder form if you have good contacts with a manufacturer you may get samples form the pre-compounded product. (It also usualy contains less than usual amounts of stabilizers).
hi Gyorgy,
Thanks for your suggestion and quick response,
Iam just wondering to get the contact for polymer powder supplier.
Pls. find below some links. Another, perhaps more tedious method is going through the technical literature of selective laser sintering. There the Experimental part contains information on the source of the polymer powder used.
http://www.alibaba.com/showroom/polymer-powder-coating.html
http://www.dow.com/amplify/fab/thermoplastic.htm
http://www.victrex.com/en/products/vicote-coatings/product-grades/product-grades.php
http://www.lehvoss.de/eng/1446.htm
http://web.iitd.ac.in/~pmpandey/RP_html_pdf/ADVANCES_IN_MATERIALS_FOR_POWDER_BASED_RAPID_PROTOTYPING_with_date.pdf
http://www.aschulman.com/Americas/Custom-Powders/Markets/84921/7/Additive-Manufacturing.aspx
If you can dissolve the pellet of the polymer and then freeze dry it, you should get a "kind" of powder.
Hi Gyorgy,
many thanks for your suggestions, I will try to buy a powder from the above mentioned company's
Hi Naveen and Gustavo, thanks for your suggestion, Iam trying to buy a powder , eventhough the mentioned method from your side is also interesting which helps me to prepare a powder which is unavailable in the market.
If you know the Tg of your polymer, then cool it below Tg (generally if you cool below the temperature of Liquid Nitrogen, most of the polymers become brittle)e and the use mortar and pestle to crush the pellets. Generally we are following this procedure for powdering natural fibers (cellulose)
In addition to question from Rajkumar,
Does the mortar and pestle method, after reaching below the Tg for polymers, lead to chain scission? Literature says it may or may not degrade the polymers but there are no exact points about this issue in the literature.
The coatings industry regularly provides powder coatings, mostly for metallic substrates. The common form of milling is cryogenic (liquid N2), since various forms of powder fusion or sintering are common side problems. I suggest you contact a company that provides powder coatings, and back track to discover who they're using for the cryogenic milling process, and talk to that supplier. That collective industry has history dating back to the 1970's and they presently have a variety of options for each step. I'm not offering specific names of companies here because of the large number of mergers over the past 20 years that have blurred a lot of the distinctions that I once knew.
Some after-thoughts:
I don't know what size range you hope to achieve, but the milling process will only provide you with relatively large particles, typically 25+ microns in size. An alternative answer is to dissolve the polymer in a strong solvent for the polymer, then very gradually titrate in some relative non-solvent (but not too far away), until one sees cloudiness occurring. As you proceed, the big problem is that you will need some kind of surfactant to stabilize the forming particles to prevent them from aggregating as the process proceeds. Cooling will assist in preserving the particles. While it is possible to achieve micron or even sub-micron sizes by this process, the level of surfactant needed will very likely interfere with the sintering process that you're trying to study.
At all stages, you should measure the Tg of your sample to determine the effect (if any) of the process you are using. For example, a variety of non-ionic surfactant will plasticize a wide range of polymers. If you're studying sintering, these side behaviors will strongly confuse the process you are trying to study. The same is true of pigmenting your polymers, because that process will also alter your Tg, and therefore sintering behavior of the particles.
You don't describe the reason for your interest, but it may be in line with ink-jet printing. I suggest you peruse that literature set, because it covers all the topics previously offered plus more.
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