Method of controlled conversion of thermosetting resins and additive manufacturing thereof by selective laser sintering
View Patent ↗The invention is directed to a method of controlled conversion of thermosetting resins and additive manufacturing thereof by selective laser sintering. Partial curing of a thermosetting formulation can be used to increase the T g of the resin and minimize the additional cure needed to cross-link a printed object. After printing, the partially cured material is finally cured via a slow temperature ramp maintained just below the material's evolving T g .
1. A method for printing a thermosetting polymer, comprising
providing a partially cured resin material, wherein the resin material comprises a thermosetting resin and a curing agent, and wherein the thermosetting resin comprises an epoxy, bismaleimide, cyanate ester, alkyne, alkene, acrylate, anhydride, carboxylic acid, isocyanate, or halide,
producing a resin powder from the partially cured resin material,
printing and sintering the resin powder on a print bed at a bed temperature near a glass transition temperature of the partially cured resin material to provide a printed part having a desired three-dimensional shape, and
curing the printed part according to a post-print cure schedule to provide a cured solid object.
2. The method of claim 1 , wherein the resin material comprises a stoichiometrically balanced formulation of the thermosetting resin and the curing agent.
3. The method of claim 1 , wherein the epoxy comprises difunctional bisphenol A/epichlorohydrine epoxy.
4. The method of claim 1 , wherein the curing agent comprises an amine.
5. The method of claim 4 , wherein the amine comprises 4,4′-diaminodiphenylsulphone.
6. The method of claim 1 , wherein the curing agent comprises a thiol, alkene, anhydride, azide, carboxylic acid, or hydroxyl.
7. The method of claim 1 , wherein the step of providing a partially cured resin material comprises mixing the thermosetting resin with the curing agent to provide a thermosetting resin formulation, and partially curing the thermosetting resin formulation to vitrification but before gelation is reached to provide the partially cured resin material.
8. The method of claim 1 , wherein the step of providing a partially cured resin material comprises
providing a resin-rich formulation wherein the curing agent is fully converted and the resin is not quite crosslinked, or a highly functional resin,
providing a curing-agent-rich formulation wherein the thermosetting resin is fully converted but not crosslinked, or a curative polymer, and
compounding the resin-rich formulation or highly functional resin with the curing-agent-rich formulation or curative polymer to provide the partially cured resin material.
9. The method of claim 1 , wherein the post-print cure schedule comprises heating the printed part at a temperature below the glass transition temperature until gelation is reached, followed by post-curing of the printed part at a temperature above the glass transition temperature.
10. The method of claim 1 , when selective laser sintering is used for the step of printing and sintering the resin powder.
11. The method of claim 1 , wherein a layer-by-layer additive manufacturing process is used to the step of printing and sintering the resin powder.
12. The method of claim 11 , wherein crosslinking between layers is not achieved during the print, but rather during the post-print cure.
13. The method of claim 1 , wherein the resin powder is unfilled.
14. The method of claim 1 , wherein the resin powder further comprises a filler.