Method for determining resin cure kinetics with low-frequency Raman spectroscopy

Chimenti, Robert V.; Lehman-Chong, Alexandra M.; Sepcic, Alyssa M.; Engelhardt, Jamison D.; Carriere, James T.; Bensley, Kayla A.; Markashevsky, Adam; Tu, Jianwei; Stanzione, Joseph F.; Lofland, Samuel E.

doi:10.1039/d3an01099f

Cited by 2 publications

(1 citation statement)

References 57 publications

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“…It is worth noting however that this can also be done with Raman spectroscopy, should the need for a non-contact in situ measurement be needed. 8 Changes in the degree of conversion were observed by monitoring the decrease in the methacrylate peak area located at 1640 cm -1 and referencing it to the peak area located at 1610 cm -1 which does not shift during cure. For each intensity, the monomer conversion, 𝛼, was normalized and plotted using,…”

Section: Cure Kineticsmentioning

confidence: 99%

Polymeric graded-index lenses via digital light processing vat photopolymerization additive manufacturing

Engelhardt,

Tu,

Chimenti

et al. 2024

Emerging Digital Micromirror Device Based Systems and Applications XVI

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Traditional methods of manufacturing graded-index (GRIN) lenses, such as chemical vapor deposition, ion exchange processes, and neutron irradiation, are time consuming, labor intensive, and cannot yield custom refractive index profiles. Additive manufacturing (AM) methods provide a potential alternative route to produce polymeric GRIN lenses easier as well as reduce costs. To date, AM approaches for GRIN lens production include inkjet 3D printing and multiphoton direct laser writing, which suffer from difficulty in material formulation and extremely large print times for macro scale lenses. This work seeks to create GRIN lenses using digital light processing (DLP) vat photopolymerization (VPP) AM. The main challenge of DLP VPP AM is related to the uncontrolled light penetration that induces additional curing in previously printed layers, which makes the control of conversion difficult. We adapted a conversion prediction model that was previously developed to predict the conversion profiles in printed parts by DLP VPP based on accumulated light dosage. By studying the index of refraction as a function of polymerization for various resin formulations, in combination with the conversion prediction model, we were able to utilize the grayscale capability of DLP to generate GRIN profiles through partial polymerization. This model was used to generate the 3D printing parameters needed to maintain proper extent of cure throughout the entirety of the print. These prints were then characterized to determine both the accuracy of the print design and the optical performance of the lens.

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Section: Cure Kineticsmentioning

confidence: 99%

Polymeric graded-index lenses via digital light processing vat photopolymerization additive manufacturing

Engelhardt,

Tu,

Chimenti

et al. 2024

Emerging Digital Micromirror Device Based Systems and Applications XVI

Self Cite

View full text Add to dashboard Cite

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Influence of Rheological Modifications on Primary Network Chemical and Structural Cure Kinetics for an Interpenetrating Polymer Network Resin

Chimenti,

Bensley,

Lehman-Chong

et al. 2024

Appl Spectrosc

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The development of non-contact in situ techniques for monitoring of cure kinetics has the potential to greatly improve both resin formulation and processing. We have recently shown that low-frequency Raman spectroscopy is a viable method for assessing resin structural cure kinetics and complements the traditional chemical conversion determined from the fingerprint region of the spectrum. In this work we further evaluate the relationship between the structural and chemical conversion by investigating two chemically identical yet rheologically different interpenetrating polymer network resin formulations. Rheological analysis demonstrates a relationship between structural conversion and storage modulus, which is not observed in the chemical conversion data. We show that one can produce master cure kinetics curves with comparable kinetic constants using both the chemical and structural conversion methodologies. Parametric analysis of the structural conversion, chemical conversion, and photorheological conversion was combined with a semi-empirical model for the storage shear modulus as a function of extent of cure.

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Method for determining resin cure kinetics with low-frequency Raman spectroscopy

Abstract: A novel, non-contact, non-destructive, and chemically agnostic methodology for measuring polymerization extent of cure kinetics using low-frequency Raman spectroscopy.

Cited by 2 publications

References 57 publications

Polymeric graded-index lenses via digital light processing vat photopolymerization additive manufacturing

Polymeric graded-index lenses via digital light processing vat photopolymerization additive manufacturing

Influence of Rheological Modifications on Primary Network Chemical and Structural Cure Kinetics for an Interpenetrating Polymer Network Resin

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