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Sinterable semi-crystalline powder and near-fully dense article formed therewith

  • US 5,342,919 A
  • Filed: 11/23/1992
  • Issued: 08/30/1994
  • Est. Priority Date: 11/23/1992
  • Status: Expired due to Term
First Claim
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1. A laser-sinterable powder product, adapted to be sintered in a selective laser sintering machine to form a sintered part, said powder consisting essentially of an unblended .polymer which provides signs of crystalline order under X-ray examination, and shows a crystalline melting point Tm as well as a glass transition temperature Tg, said polymer having a two-tier particle size distribution said powder having the following properties:

  • (a) freely-flowable semi-crystalline powder having a crystallinity in the range from 10-90% measured by [DSC] differential scanning calorimetry;

    (b) a major portion by weight of the powder having a sphericity in the range from greater than 0.5 to 0.9, and a two-tier distribution in which substantially no primary particles has an average diameter greater than 180μ

    m, provided further that the number average ratio of particles smaller than 53μ

    m is greater than 80%, the remaining larger particles being in the size range from 53μ

    m to 180μ

    m;

    a layer of said powder no more than 250μ

    m deep absorbing essentially all infra-red energy beamed therethrough at a wavelength of 10.6μ

    m, and a layer of said powder no more than 180μ

    m thick absorbing more than 50% of said energy;

    (c) a number average molecular weight in the range from about 30,000 to 500,000, and a molecular weight distribution Mw /Mn in the range from 1 to 5; and

    , (d) a window of sinterability in the temperature range from near said powder'"'"'s softening temperature Ts to said powder'"'"'s caking temperature Tc ;

    whereby when said powder is sintered layer-wise in said window of sinterability to form a slice, it will not curl.

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