Sacrificial high heat support materials for additive manufacturing processes
Disclosed herein are methods that includes using a water-degradable (e.g., autoclavable) support material together with a high-heat build material (e.g., polyetherimide or PEI). When the support material is autoclaved for a period of time, the support material becomes brittle and then disintegrates into powder and therefore can be removed from the model or build material, leaving behind a part formed from the model material that includes features (e.g., cavities, channels, etc.) formerly occupied by the support material.
1. A method, comprising:
with an additive manufacturing process, forming a workpiece that comprises
a build portion comprising polyetherimide, polyetherimide sulfone, polyimide, polysulfone, polyether sulfone, polyphenylene ether sulfone, polyphenylene ether, imidized polymethacrylate, blends thereof, or any combination thereof, and
a degradable support portion contacting the build portion,
the degradable support portion comprising a thermoplastic polycarbonate and a hindered amine light stabilizer; and
exposing the workpiece to water at a temperature of from 85 degrees Celsius (° C.) to a temperature that corresponds to a glass transition temperature (Tg) of the build portion for a time sufficient to selectively degrade at least a region of the degradable support portion.
2. The method of claim 1 , wherein the water further comprises a base.
3. The method of claim 1 , further comprising removing from the workpiece the selectively degraded region of the degradable support portion by mechanical agitation, brushing, washing, fluidized bed immersion, tumbling, fluid spray, ultrasonic agitation, heating, cooling, or any combination thereof.
4. The method of claim 1 , wherein the exposing effects a reduction in the molecular weight of the support portion of from 50% to 95%.
5. A workpiece, comprising:
a build portion comprising polyetherimide, polyetherimide sulfone, polyimide, polysulfone, polyether sulfone, polyphenylene ether sulfone, polyphenylene ether, imidized polymethacrylate, blends thereof, or any combination thereof; and
a degradable support portion contacting the build portion,
the degradable support portion comprising a polycarbonate having a Tg of from 130 to 280° C. and from 0.1 to 3.0 wt % hindered amine light stabilizer.
6. The workpiece of claim 5 , wherein the degradable support portion has a melt viscosity of from 1000 to 20,000 poise (P) as measured as per ASTM D4440-15 (15 radians/second) at a temperature that is from 130° C. to 240° C. above a temperature that corresponds to a Tg of the degradable support portion, and retains at least 60% of the initial melt viscosity after 10 minutes of exposure at that melt temperature.
7. The workpiece of claim 5 , wherein:
(a) the degradable support portion has a molecular weight and the degradable support portion loses at least 70% of its molecular weight after 6 hours of exposure to steam at 120° C.;
(b) the build portion has a molecular weight and the build portion retains at least 70% of its molecular weight after 6 hours of exposure to steam at 120° C.; or
(c) both (a) and (b).
8. The workpiece of claim 5 , wherein the polycarbonate comprises an isoindolinone bisphenol polycarbonate copolymer, a polyester carbonate copolymer, a trimethyl cyclohexyl bisphenol carbonate copolymer, a tetrabromo bisphenol A polycarbonate copolymer, blends thereof, or any combination thereof.
9. The workpiece of claim 5 , wherein the degradable support portion has a molecular weight of from 15,000 to 80,000 Daltons (polycarbonate standard).
10. The workpiece of claim 5 , wherein:
(a) the hindered amine light stabilizer has a formula molecular weight of 200 to 10,000 grams per mole (g/mol);
(b) the hindered amine light stabilizer has a pKa in water of from 7.0 to 10.0; or
(c) both (a) and (b).
11. A degradable support structure comprising a plurality of layers of additively manufactured material, the plurality of layers of additively manufactured material comprising a polycarbonate and a hindered amine light stabilizer.
12. The degradable support structure of claim 11 , wherein the plurality of layers of additively manufactured material comprise 0.1 to 3.0 wt % hindered amine stabilizer.
13. The degradable support structure of claim 11 , wherein:
a) the hindered amine light stabilizer has a formula molecular weight of 200 to 10,000 grams per mole (g/mol);
(b) the hindered amine light stabilizer has a pKa in water of from 7.0 to 10.0; or
(c) both (a) and (b).
14. The degradable support structure of claim 11 , wherein at least a region of the degradable support structure is selectively degradable when exposed to water at a temperature of from 85 to 280° C. for a time of from 1 to 3 hours.
15. The degradable support structure of claim 11 , wherein the degradable support structure is a sacrificial tooling article or trapped mold for use in composite tooling applications, and the sacrificial tooling article or trapped mold is used to make a hollow composite structure, duct, tube or hollow structural member.