Amorphous thermoplastic additive manufactured articles and method to make them
A semi-crystalline blended polymer useful for additive manufacturing is comprised of an amorphous thermoplastic polymer and a thermoplastic semi-crystalline polymer, each of the polymers being essentially miscible in the other and being blended at a weight ratio of amorphous polymer/semi-crystalline polymer of greater that 1 to about 20. The semi-crystalline blended polymer displays a DSC melt peak enthalpy of at least about 3 joules/g. The semi-crystalline polymer may be made by blending the aforementioned polymers at the weight ratio and subject to heating between the melt temperature of the semi-crystalline polymer and the glass transition temperature of the amorphous polymer. The semi-crystalline blended polymer may revert to essentially an amorphous polymer when additive manufactured by fusing layers of said polymer powders together.
1. A method of forming a semi-crystalline blended polymer comprising:
a. melt blending an amorphous thermoplastic polymer and a thermoplastic semi-crystalline polymer, each of the polymers being essentially miscible in the other, at a weight ratio of the amorphous polymer/semi-crystalline polymer that is greater than 1 to about 20 to form a blended polymer that is essentially amorphous,
b. heat-treating the blended polymer at a crystallizing temperature above the glass transition temperature of the amorphous polymer but below the melt temperature of the semicrystalline polymer for a heat treating time to crystallize the blended polymer sufficiently to realize the semi-crystalline blended polymer, wherein at least portion of the heat treating is performed below, but within 20° C. of the melt temperature of the semi-crystalline polymer and the semicrystalline blended polymer displays a DSC melt peak enthalpy of at least about 3 joules/g, and
c. grinding the semi-crystalline blended polymer to form a powder at a temperature where the semi-crystalline polymer becomes embrittled.
2. The method of claim 1 , wherein the heat-treating is for a heat treating time of at least about 2 hours.
3. The method of claim 1 , wherein the semicrystalline blended polymer reverts to a substantially amorphous polymer blend upon heating above the semi-crystalline melt blended polymer's melt temperature.
4. The method of claim 1 , wherein the semi-crystalline blended polymer has a DSC melting peak enthalpy of at least about 5 Joules/g and melt temperature of at least about 140° C.
5. The method of claim 1 , wherein the heat treating temperature is from about 100° C. to about 180° C.
6. The method of claim 5 , wherein the heat treating temperature is at most about 175° C.
7. The method of claim 1 , wherein the grinding is performed at a temperature below −50° C.
8. A method of forming an additive manufactured article comprising,
a. spreading a layer of the powder of claim 1 ,
b. heating and fusing the particles of the layer in a controlled manner by directed electromagnetic radiation,
c. spreading subsequent layers of the semicrystalline blended powder and fusing each layer to its prior layer in a controlled manner by directed electromagnetic radiation to form the additive manufactured article.
9. The method of claim 8 , wherein the additive manufactured article's polymer is essentially amorphous.
10. The method of claim 9 , wherein the additive manufactured article upon exposure to heating above the glass transition temperature of the amorphous polymer for a time of at least 2 hours causes the additive manufactured article's polymer to crystallize.
11. The method of claim 1 , wherein the grinding is performed at a temperature below about 0° C.