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Described herein are thermoset compositions suitable for hybrid polymerization when processed via additive fabrication equipment utilizing sources of actinic radiation with peak spectral intensities in the UV and/or visible region containing a photoinitiating package, a cationically curable constitu

Described herein are thermoset compositions suitable for hybrid polymerization when processed via additive fabrication equipment utilizing sources of actinic radiation with peak spectral intensities in the UV and/or visible region containing a photoinitiating package, a cationically curable constituent, a free-radically curable component, and optionally, one or more additives. Such thermoset compositions preferably contain a Norrish Type I photoinitiator that is an alkyl-, aryl-, or acyl-substituted compound centered around a Group 14 atom, and further possesses specified ranges of ionization potential values with respect to its known triplet state. Also disclosed are methods of creating three-dimensional parts via additive fabrication processes utilizing sources of actinic radiation with peak spectral intensities in the UV and/or visible regions employing the claimed thermosetting compositions, along with the parts cured therefrom.

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1. A UV/vis radiation curable composition for additive fabrication comprising: a photoinitiating package comprising: from about 0.1 wt. % to about 15 wt. % of an iodonium salt cationic photoinitiator;from about 0.1 wt. % to about 8 wt. % of a Norrish Type I photoinitiator;from about 0.1 wt. % to abo

1. A UV/vis radiation curable composition for additive fabrication comprising: a photoinitiating package comprising: from about 0.1 wt. % to about 15 wt. % of an iodonium salt cationic photoinitiator;from about 0.1 wt. % to about 8 wt. % of a Norrish Type I photoinitiator;from about 0.1 wt. % to about 15 wt. % of an accelerator; andoptionally, a photosensitizer;a cationically curable constituent comprising from about 1 wt. % to about 20 wt. % of an oxetane component;from about 3 wt. % to about 40 wt. % of a cycloaliphatic epoxide component; andfrom about 2 wt. % to about 40 wt. % of a glycidyl ether component;from about 5 wt. % to about 40 wt. % of a free-radically curable component; andoptionally, up to about 50 wt. % of one or more additives;wherein the Norrish Type I photoinitiator is an alkyl-, aryl-, or acyl-substituted compound which possesses an atom selected from the group consisting of silicon, germanium, tin, and lead;wherein the accelerator comprises an electron-donating substituent attached to a vinyl group;and wherein all weight percentages are listed relative to the weight of the entire composition. 2. The UV/vis radiation curable composition for additive fabrication according to claim 1, wherein the molar ratio of the iodonium salt cationic photoinitiator to the accelerator is from 1:2 to 1:20, the molar ratio of the Norrish Type I photoinitiator to the accelerator is from 1:2 to 1:20, andthe molar ratio of the iodonium salt cationic photoinitiator to the Norrish Type I photoinitiator is from 1:2 to 2:1. 3. The UV/vis radiation curable composition for additive fabrication according to claim 2, wherein the electron-donating substituent attached to a vinyl group is selected from one or more of the group consisting of vinyl, ethers, vinyl esters, vinyl thioethers, n-vinyl carbazoles, n-vinyl pyrollidones, n-vinyl caprolactams, allyl ethers, and vinyl carbonates. 4. The UV/vis radiation curable composition for additive fabrication according to claim 2, wherein the accelerator is a multifunctional vinyl ether compound. 5. The UV/vis radiation curable composition for additive fabrication according to claim 4, wherein the iodonium salt is selected from the group consisting of (4-methylphenyl)[4-(2-methylpropyl)phenyl]-, hexafluorophosphate, [4-(1-methylethyl)phenyl](4-methylphenyl)-, tetrakis(pentafluorophenyl)borate(1-), (Bis(4-dodecylphenyl)iodonium hexaflurorantimonate), and (Bis(4-tert-butylphenyl)iodonium hexafluorophosphate). 6. The UV/vis radiation curable composition for additive fabrication according to claim 3, wherein the Norrish Type I photoinitiator comprises a compound meeting the following formula (I): in which Ar1 is an aromatic group, either unsubstituted or further substituted in any position by one or more alkyl radicals, ethers, sulfides, silyl groups, halogens, carboxyl groups, vinyl groups, additional aromatic or heterocyclic groups, alkyl radicals, or aromatic or heterocyclic groups interrupted by one or more ether, sulfide, silyl, carboxyl, or vinyl groups, and in which R1, R2, and R3 independently may be an acyl, aryl, alkyl, or carbonyl group, either unsubstituted or further substituted one or more alkyl radicals, ethers, sulfides, silyl groups, halogens, carboxyl groups, vinyl groups, additional aromatic or heterocyclic groups, alkyl radicals, or aromatic or heterocyclic groups interrupted by one or more ether, sulfide, silyl, carboxyl, or vinyl groups. 7. The UV/vis radiation curable composition for additive fabrication according to claim 6, wherein one of the following conditions is satisfied: (a) each of R1-R3 is an aryl-substituted or aromatic acyl group; orb) if exactly two of R1-R3 are an aryl-substituted or aromatic acyl group, the remaining substituted groups are a C1-C10 alkyl; or(c) if exactly one of R1-R3 is an aryl-substituted or aromatic acyl group, the remaining two substituted groups are a C1-C10 alkyl; or(d) each of R1-R3 is a C1-C10 alkyl. 8. The UV/vis radiation curable composition for additive fabrication according to claim 3, wherein the Norrish Type I photoinitiator comprises at least 80% by weight, relative to the entire weight of all Norrish Type I photoinitiators present in the composition, of one or both of the following compounds: 9. The UV/vis radiation curable composition for additive fabrication according to claim 1, wherein the accelerator is capable of forming a vinyl-based or ether radical, wherein said vinyl-based or ether radical possesses a calculated ionization potential from about 3.3 eV to about 4.89 eV when the ionization potential is calculated in accordance with molecular modeling under B3LYP/6-31G(d) in combination with Koopman's Theorem (IP=−εHOMO). 10. The UV/vis radiation curable composition for additive fabrication according to claim 9, wherein the calculated ionization potential of the vinyl-based or ether radical is from about 3.80 eV to about 4.20 eV when the ionization potential is calculated in accordance with molecular modeling under B3LYP/6-31G(d) in combination with Koopman's Theorem (IP=−εHOMO). 11. The UV/vis radiation curable composition for additive fabrication according to claim 3, wherein the Norrish Type I photoinitiator is capable of forming a radical that possesses a rate of addition to the vinyl ether greater than or equal to 3×106 M−1 s−1. 12. The UV/vis radiation curable composition for additive fabrication according to claim 10, wherein the composition comprises at least 80 wt. %, relative to the weight of all of the Norrish Type I photoinitiators present in the entire composition, of a Norrish Type I photoinitiator possessing a potential excited triplet state with an ionization potential of from about 3.0 eV to about 3.98 eV, wherein the ionization potential is calculated in accordance with molecular modeling B3LYP/6-31G(d) in combination with Koopman's Theorem (IP=−εHOMO). 13. The UV/vis radiation curable composition for additive fabrication according to claim 4, wherein the multifunctional vinyl ether compound is present in an amount by weight, relative to the entire composition, of from about 1.5 wt. % to about 8 wt. %. 14. A liquid UV/vis radiation curable composition for additive fabrication comprising: a photoinitiating package comprising an onium salt cationic photoinitiator;a reductant comprising an effective amount of a Norrish Type I photoinitiator dissolved in a vinyl ether compound that is a liquid at 25 degrees C.; andoptionally, a photosensitizer;a cationically polymerizable constituent;a free-radically polymerizable component; andoptionally, one or more additives;wherein the Norrish Type I photoinitiator is capable of entering a triplet state upon excitation by exposure to actinic radiation, wherein said excited triplet state possesses an ionization potential of from about 2.5 eV to about 4.15 eV, wherein the ionization potential is calculated in accordance with molecular modeling under B3LYP/6-31G(d) in combination with Koopman's Theorem (IP=−εHOMO). 15. The liquid UV/vis radiation curable composition for additive fabrication according to claim 14, wherein the excited triplet state of the Norrish Type I photoinitiator possesses an ionization potential of from about 3.0 eV to about 3.55 eV, wherein the ionization potential is calculated in accordance with molecular modeling under B3LYP/6-31G(d) in combination with Koopman's Theorem (IP=−εHOMO). 16. The liquid UV/vis radiation curable composition for additive fabrication according to claim 15, wherein the onium salt cationic photoinitiator is an iodonium salt cationic photoinitiator. 17. The liquid UV/vis radiation curable composition for additive fabrication according to claim 16, wherein the Norrish Type I photoinitiator is capable of forming a radical upon exposure to actinic radiation that possesses a calculated ionization potential of less than 5.00 eV, as calculated by molecular modeling under B3LYP/6-31G(d) in combination with Koopman's Theorem (IP=−εHOMO). 18. The liquid UV/vis radiation curable composition for additive fabrication according to claim 17, wherein the Norrish Type I photoinitiator is capable of forming a radical upon exposure to actinic radiation that possesses a calculated ionization potential of from about 4.05 eV to about 4.80 eV, as calculated by molecular modeling under B3LYP/6-31G(d) in combination with Koopman's Theorem (IP=−εHOMO). 19. The liquid UV/vis radiation curable composition for additive fabrication according to claim 18, wherein the Norrish Type I photoinitiator is capable of forming a radical that possesses a rate of addition to the vinyl ether compound of greater than about 105 M−1 s−1. 20. The liquid UV/vis radiation curable composition for additive fabrication according to claim 16, wherein the cationically polymerizable constituent comprises a cycloaliphatic epoxide, a glycidyl ether, and an oxetane. 21. The liquid UV/vis radiation curable composition for additive fabrication according to claim 20, wherein the vinyl ether is present in an amount from 0.5 wt. % to 20 wt. %, relative to the weight of the entire composition. 22. The liquid UV/vis radiation curable composition for additive fabrication according to claim 21, wherein the vinyl ether is present in an amount of from 2 wt. % to 8 wt. %, relative to the weight of the entire composition. 23. The liquid UV/vis radiation curable composition for additive fabrication according to claim 22, wherein the Norrish Type I photoinitiator is also a photosensitizer for photosensitizing the iodonium salt cationic photoinitiator. 24. The liquid UV/vis radiation curable composition for additive fabrication according to claim 22, wherein the Norrish Type I photoinitiator comprises a compound that is alkyl-, aryl-, or acyl-substituted, wherein the alkyl-, aryl-, or acyl-substituted compound also possesses an atom selected from the group consisting of silicon, germanium, tin, and lead. 25. The liquid UV/vis radiation curable composition for additive fabrication according to claim 24, wherein the Norrish Type I photoinitiator comprises an acylgermanium compound. 26. The liquid UV/vis radiation curable composition for additive fabrication according to claim 25, wherein the acylgermanium compound possesses a structure in accordance with the following formula (I): in which Ar1 is an aromatic group, either unsubstituted or further substituted in any position by one or more alkyl radicals, ethers, sulfides, silyl groups, halogens, carboxyl groups, vinyl groups, additional aromatic or heterocyclic groups, alkyl radicals, or aromatic or heterocyclic groups interrupted by one or more ether, sulfide, silyl, carboxyl, or vinyl groups, and in which R1, R2, and R3 independently may be an acyl, aryl, alkyl, or carbonyl group, either unsubstituted or further substituted one or more alkyl radicals, ethers, sulfides, silyl groups, halogens, carboxyl groups, vinyl groups, additional aromatic or heterocyclic groups, alkyl radicals, or aromatic or heterocyclic groups interrupted by one or more ether, sulfide, silyl, carboxyl, or vinyl groups. 27. The liquid UV/vis radiation curable composition for additive fabrication according to claim 22, wherein if the radiation curable composition is exposed to UV/vis optics emitting radiation with a peak spectral output at 400 nm and an irradiance at a surface of the radiation curable composition of 2 mW/cm2 for 10 seconds, said radiation curable composition achieves the following: a cycloaliphatic epoxide conversion at 200 seconds of at least about 65%,a least squares fit of the initial 12 seconds of the cycloaliphatic epoxide conversion rate of at least about 1.25 s−1, andan acrylate conversion at 200 seconds of at least about 95%. 28. A method of forming a three-dimensional article via an additive fabrication system utilizing UV/vis optics, the method comprising: (1) providing the liquid UV/vis radiation curable composition for additive fabrication according to claim 20;(2) establishing a first liquid layer of the liquid radiation curable resin;(3) exposing the first liquid layer imagewise to actinic radiation via a UV/vis optics configuration to form an imaged cross-section, thereby forming a first cured layer;(4) forming a new layer of said liquid UV/vis radiation curable composition in contact with the first cured layer;(5) exposing said new layer imagewise to actinic radiation to form an additional imaged cross-section; and(6) repeating steps (4) and (5) a sufficient number of times in order to build up a three-dimensional article; wherein the UV/vis optics emit radiation at a peak spectral intensity from about 375 nm to about 435 nm. 29. The method of claim 28, wherein the UV/vis optics configuration is selected from one or more of the group consisting of LED/DLP, laser/DLP, LED/LCD, and laser/LCD.