Photopolymer formulation towards large scale additive manufacturing of autoclave capable tooling

Stiles, Alex; Kobler, Will; Yeole, Pritesh; Vaidya, Uday

doi:10.1016/j.addma.2021.102571

Cited by 8 publications

(10 citation statements)

References 33 publications

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“…DiPietro reported a full throughcure in 8-mm-thick fiberglass laminates after 15 s using a photobleaching PI and a high intensity 25 W/cm 2 spotlight [78]. For LFAM applications, an exposure time of 5 s under a 1.7 W/cm 2 incident-light intensity has been correlated with a linear deposition rate of 5 mm/s [24].…”

Section: Literature Reviewmentioning

confidence: 99%

“…Since machine speed is limited, LFAM printers maximize throughput by increasing layer height. In formulating photopolymers for LFAM, a critical limiting factor is the exposure time required for full through-cure at layer heights of 2-4 mm [24]. Therefore, deposition rates at these layer heights can be improved by decreasing the UV irradiation time required to achieve full through-cure.…”

Section: Literature Reviewmentioning

confidence: 99%

“…Stiles et al formulated vinyl ester photopolymers towards LFAM scale, focusing on monomer selection as an approach to minimize cure gradients. They reported that 3 mm layers could be fully cured with an irradiation time of 5 s under high-intensity UV LED lamps [24]. In photopolymers, a curing reaction generally commences with photoinitiation, when light is absorbed by a photoinitiating system that reacts to form initiating species such as free radicals, cations, acids, bases, etc.…”

Section: Introductionmentioning

confidence: 99%

“…The objective of the present study was to improve upon the Bis-EMA/PETIA photopolymer formulations previously developed by Stiles et al [24] by adjusting PI type and concentration to improve the through-thickness cure response under simulated LFAM conditions. Of the strategies discussed, upconversion particles, thermal initiators and RAFT were not utilized for the reasons previously mentioned.…”

Section: Introductionmentioning

confidence: 99%

“…Of the strategies discussed, upconversion particles, thermal initiators and RAFT were not utilized for the reasons previously mentioned. Likewise, hybrid cationic-curing chemistries would necessitate the addition of both a cationic initiator and epoxy, which could alter the cured polymer's properties to the point of preventing direct comparison against the previous BDMB formulations [24]. Therefore, the most straightforward options for potentially improving through-thickness cure response were to optimize the PI concentration for low optical density and employ a photoinitiating PI.…”

Section: Introductionmentioning

confidence: 99%

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Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

et al. 2022

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Photopolymers are an attractive option for large-format additive manufacturing (LFAM), because they can be formulated from structural thermosets and cure rapidly in ambient conditions under low-energy ultraviolet light-emitting diode (UV LED) lamps. Photopolymer cure is strongly influenced by the depth penetration of UV light, which can be limited in the 2–4 mm layer thicknesses typical of LFAM. Photoinitiator (PI) systems that exhibit photobleaching have proven useful in thick-section cure applications, because they generate a photoinitiation wavefront, but this effect is time-dependent. This study investigates the light transmission and through-thickness cure behavior in (meth)acrylate photopolymer formulations with the photobleaching initiator bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BAPO). Utilizing an optical model developed by Kenning et al., lower concentrations (0.1 wt% to 0.5 wt%) of BAPO were predicted to yield rapid onset of photoinitiation. In situ cure measurements under continuous UV LED irradiation of 380 mW/cm2 showed that a 0.1 wt% concentration of BAPO achieved peak polymerization rate within 2.5 s at a 3-mm depth. With only 1 s of irradiation at 1.7 W/cm2 intensity, the 0.1 wt% BAPO formulation also achieved the highest level of cure of the formulas tested. For an irradiation dose of 5.5 J/cm2 at a duration of 3.7 s, cured polymer specimens achieved a flexural strength of 108 MPa and a flexural modulus of 3.1 GPa. This study demonstrates the utility of optical modeling as a potential screening tool for new photopolymer formulations, primarily in identifying an upper limit to PI concentration for the desired cure depth. The results also show that photobleaching provides only a limited benefit for LFAM applications with short (1.0 s to 3.7 s) UV irradiation times and indicate that excess PI concentration can inhibit light transmission even under extended irradiation times up to 60 s.

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Section: Literature Reviewmentioning

confidence: 99%

Section: Literature Reviewmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

et al. 2022

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NIR Laser Integration of Photodetector on 3D Printed Chamber for Colorimetric Biosensing

Lin

Chang

Noel

et al. 2022

Adv Materials Technologies

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In this work, gold nanoparticles (Au NPs)/indium‐zinc‐oxide (IZO) nanocomposite visible photodetector (PD) is directly prepared by near‐infrared (NIR) laser‐annealing on a 3D‐printed substrate to form an integrated colorimetric sensor. After a surface planarization process, using a low power laser treatment without damaging the substrate, Au NPs are formed from the Au thin layer (6 nm) on 3D‐printed resin substrate by laser‐assisted dewetting process. Also, the UV–vis photoresponsivity is compared by tuning different NIR laser power intensity for sol‐gel IZO curing. By investigating the temperature profile of each laser annealing process and the surface morphology of Au NPs/IZO nanocomposite film, the optimized PD is then integrated with a 3D‐printed sensing chamber for successfully demonstrating urea detection varied from 1, 5, 10, 25 and 50 × 10−3 m, which refer to the salivary urea concentrations for healthy and chronic kidney disease groups.

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Large-scale reactive thermoset printing: Complex interactions between temperature evolution, viscosity, and cure shrinkage

Romberg

Hershey

Lindahl

et al. 2022

Int J Adv Manuf Technol

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Photopolymer formulation towards large scale additive manufacturing of autoclave capable tooling

Cited by 8 publications

References 33 publications

Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

Photoinitiator Selection and Concentration in Photopolymer Formulations towards Large-Format Additive Manufacturing

NIR Laser Integration of Photodetector on 3D Printed Chamber for Colorimetric Biosensing

Large-scale reactive thermoset printing: Complex interactions between temperature evolution, viscosity, and cure shrinkage

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