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Dual-Wavelength (UV and Blue) Controlled Photopolymerization Confinement for 3D-Printing: Modeling and Analysis of Measurements

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Dual-Wavelength (UV and Blue) Controlled Photopolymerization Confinement for 3D-Printing: Modeling and Analysis of Measurements

Jui-Teng Lin et al. Polymers (Basel).

Abstract

The kinetics and modeling of dual-wavelength (UV and blue) controlled photopolymerization confinement (PC) are presented and measured data are analyzed by analytic formulas and numerical data. The UV-light initiated inhibition effect is strongly monomer-dependent due to different C=C bond rate constants and conversion efficacies. Without the UV-light, for a given blue-light intensity, higher initiator concentration (C10) and rate constant (k') lead to higher conversion, as also predicted by analytic formulas, in which the total conversion rate (RT) is an increasing function of C1 and k'R, which is proportional to k'[gB1C1]0.5. However, the coupling factor B1 plays a different role that higher B1 leads to higher conversion only in the transient regime; whereas higher B1 leads to lower steady-state conversion. For a fixed initiator concentration C10, higher inhibitor concentration (C20) leads to lower conversion due to a stronger inhibition effect. However, same conversion reduction was found for the same H-factor defined by H0 = [b1C10 - b2C20]. Conversion of blue-only are much higher than that of UV-only and UV-blue combined, in which high C20 results a strong reduction of blue-only-conversion, such that the UV-light serves as the turn-off (trigger) mechanism for the purpose of spatial confirmation within the overlap area of UV and blue light. For example, UV-light controlled methacrylate conversion of a glycidyl dimethacrylate resin is formulated with a tertiary amine co-initiator, and butyl nitrite. The system is subject to a continuous exposure of a blue light, but an on-off exposure of a UV-light. Finally, we developed a theoretical new finding for the criterion of a good material/candidate governed by a double ratio of light-intensity and concentration, [I20C20]/[I10C10].

Keywords: 3D printing; additive manufacturing; dual-wavelength; kinetic model; photopolymerization; spatial confirmation.

Conflict of interest statement

Jui-Teng Lin is the CEO of New Vision, Inc. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Schematics of photochemical pathways of dual wavelength photopolymerization; in which crosslinkers are formed via two pathways, via the photoinitiator PA (under a blue light), and PB (under a UV light). The initiation radicals R and [X] crosslink with the monomer [M]; whereas the inhibition radicals [N] reduces the conversion efficacy by reducing the active radicals (R’ and R). Shown also is the co-initiator (PC), which reacts with the triplet state of PA (T*) forming an intermediate radical (R’). Bimolecular termination of R’ produces a propagating radical (R) which leads to crosslinks; terminations could be also resulted by the interaction of R and R’, and R and [N].
Figure 2
Figure 2
Conversion profiles of blue-light (without UV-light) for (left Figure) C10 = (0.05, 0.1, 0.2, 0.4) %, for curve (1,2,3,4), for fixed b1 = 0.1; and (right Figure) b1 = (0.015, 0.05,0.15,0.5), for fixed C10 = 0.2 %; for C30 = 0.5 %, [M]0 = 0.2 %, k’ = 1.0, kT = 0.5, k57 = (k5/k7) = k68 = (k6/k8) = k” = 35 (1/s).
Figure 3
Figure 3
The same as Figure 2 but for various k’ = (1.0, 0.3, 0.19), for curves (1,2,3), for fixed C10 = 0.2%, and adjusted b1 = (0.15, 0.05, 0.05) to fit the measured data of de Beer et al. [10].
Figure 4
Figure 4
Conversion profiles for blue-only (black curve—1), UV-only (blue curve—2) and both-light (red curve—3), for C10 = 0.2%, C30 = 3.0%, b1 = 0.1, b2 = 0.007, k” = 35; where solid color curves are calculated and bars are measured data of de Beer et al. [10].
Figure 5
Figure 5
Same as Figure 4, but for different monomers governed by various k” = 60 (left Figure) and k” = 150 (right Figure), for b1 = 0.05, b2 = 0.007, k’ = 1.0, where bars are measured data of de Beer et al. [10].
Figure 6
Figure 6
The initiation radical (R, left) and conversion (right) profiles in the presence of UV light; for various inhibitor concentration, C20 = (0, 1.0, 2.0, 3.0), for curves (1,2,3,4; red, green, blue, violet), for b1 = b3 = 0.1 (1/s/%), C10 = 0.2 (%), C30 = 0.5 (%), [M]0 = 0.2 (%); k’ = 1.0 (1/s), k48 = 1.0 (1/s), k37 = 1.0 (1/s), k57 = 0.01 (1/s).
Figure 7
Figure 7
The same as Figure 6, but for a fixed difference of [b1C10 − b2C20] = 0.003, for C20 = 0 (curve-1) and C20 > 0, for curves (2,3,4) showing the overlapping of these three curves.
Figure 8
Figure 8
The initiation radical (left) and conversion (right) profiles for C20 = (0, 0.5,1.0, 3.0), for curve (red, green, blue, violet), in the presence of both blue and UV light; for b1 = 0.04, b2 = 0.002, b3 = 0.1 (1/s/%), k’ = 2.0 (1/s), k48 =10 (1/s), k37 = 20(1/s) and k57 = 0.01 (1/s). In right figure, the background is measured data from van der Laan et al. [11].
Figure 9
Figure 9
Methacrylate conversion of a bisGMA/TEGDMA resin formulated with 0.2 wt% CQ/0.5 wt% EDAB/0/5 wt% BN and subject to a continuous exposure of a blue light, but an on-off exposure of a UV-light for 0.5 min, as indicated by the violet vertical areas; where black bars are measured data from van der Laan et al. [11] and red curve is our theoretical simulation.

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