<i>In situ</i>investigation of the kinetics and microstructure during photopolymerization by positron annihilation technique and NIR-photorheology

Švajdlenková, Helena; Šauša, O.; Peer, Gernot; Gorsche, Christian

doi:10.1039/c8ra07578f

Cited by 14 publications

(12 citation statements)

References 43 publications

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“…For thermoset products, the gel point can be seen either as the point at which occurs the heat dissipation corresponding to the viscous part of a polymer (glass transition temperature or maximum of G′′) or may be related to the drop in mechanical properties corresponding to the elastic part (maximum of tan δ). From these different approaches, it is possible to estimate the gel point from the conversion at the maximum rate of conversion R c [38] or from a mechanical value, such as the G′/G′′ intersection [39–40] or the beginning of the shrinkage of the resin [41] . These approaches have led to values ranging from 5 to 35 % for acrylate resins, the mechanical methods leading to 30–35 % of conversion for reaching the gel point [38–41] …”

Section: Resultsmentioning

confidence: 99%

“…From these different approaches, it is possible to estimate the gel point from the conversion at the maximum rate of conversion R c [38] or from a mechanical value, such as the G′/G′′ intersection [39–40] or the beginning of the shrinkage of the resin [41] . These approaches have led to values ranging from 5 to 35 % for acrylate resins, the mechanical methods leading to 30–35 % of conversion for reaching the gel point [38–41] …”

Section: Resultsmentioning

confidence: 99%

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A Simple and Efficient Model to Determine the Photonic Parameters of a Photopolymerizable Resin Usable in 3D Printing

et al. 2021

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This study provides insight into the relationship between the photochemical reactivity and the photonic parameters of an acrylate formulation usable in digital light processing (DLP) 3D printing. First the photoreactivity of riboflavin tetrabutyrate (RFT) used as a non‐toxic photoinitiator is assessed by laser flash photolysis in the absence and in the presence of an amine as co‐initiator. RFT alone is able to photopolymerize the acrylate formulation at a rate which is drastically increased when the co‐initiator is added. Then, the depth of light penetration (Dp) and the critical energy (Ec) to form a polymer film were measured and compared to those determined from the Bouguer‐Lambert‐Beer law for Dp and from the Stockmayer equation and photopolymerization experiments for Ec. A new proposed model is able to predict the in‐depth acrylate conversion within a printed part with a relatively low input of experimental parameters. Confocal Raman microscopy is used to discuss the effect of the photobleaching of RFT in the absence of co‐initiator on the photopolymerized films. Finally, it is shown that this formulation performs quite well for 3D printing with a resolution close to the best performance of the DLP printer.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

A Simple and Efficient Model to Determine the Photonic Parameters of a Photopolymerizable Resin Usable in 3D Printing

et al. 2021

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“…Each spectrum was collected with about 2.0 × 10 6 counts, and then analyzed using a three‐component (τ 1 , τ 2 and τ 3 ) fitting LT 9.0 program. The radius (R) of free volume holes can be calculated from the long‐lived component τ 3 based on the following Equation 24,25 :

\frac{1}{τ_{3}} = 2 ([], 1 - \frac{R}{R + 0.1656} + \frac{1}{2 π} Sin ((), \frac{2 πR}{R + 0.1656})) .

…”

Section: Methodsmentioning

confidence: 99%

Sulfonated and cross‐linked polystyrene ultrafine fibers for the esterification of palmitic acid for biodiesel production

Shao

2020

J of Applied Polymer Sci

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For the need of green and sustainable development, a fibrous solid acid catalyst was developed for the transformation of low cost oils to biodiesel in an efficient and green manner. Polystyrene was electrospun into ultrafine fibers with mean diameter of~1.34 μm, and then simultaneously cross-linked and sulfonated in sulfuric acid/acetic acid mixed solvent with paraformaldehyde as the external cross-linker. The cross-linking and sulfonation degrees were controllable by changing the ratio of sulfuric acid/acetic acid. After sulfonation and cross-linking, the solvent resistance, chemical structure, and composition of these fibers were separately characterized by scanning electron microscopy, infrared spectroscopy, and elemental analysis. At last, this novel fibrous solid acid catalyst was used to catalyze the esterification reaction of palmitic acid and methanol for biodiesel production. After optimizing the reaction conditions, this fibrous solid acid catalyst can catalyze the esterification of palmitic acid and methanol with the conversion up to 92% under mild reaction conditions. Moreover, due to the fibrous structure, this fibrous solid acid catalyst could be readily separated and reused.

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“…where ΔR = 0.1656 nm is derived from fitting the observed o-Ps lifetimes in molecular solids with known hole sizes. 25,26…”

Section: Determination Of Free Volume Holes Size and Concentration mentioning

confidence: 99%

“…PALS is a sensitive technique to measure the free volume hole size and concentration. 25,26,29 For comparison, polystyrene nanofibers (PS) and crosslinked polystyrene nanofibers (CPS) were also prepared and analyzed by PALS. As the crosslinking of polystyrene molecules would restrict the movement of polymer chain, both the size and concentration of free volume holes in these composite nanofibers were reduced after crosslinking.…”

Section: Characterizationmentioning

confidence: 99%

Palladium complex embedded crosslinked polystyrene nanofibers as a green and efficient heterogeneous catalyst for coupling reactions

Zhang

Qin

et al. 2020

J of Applied Polymer Sci

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A simple and green chemical modification coupled with electrospinning technique has been developed to incorporate tetrakis(triphenylphosphine)palladium [Pd(PPh3)4] inside crosslinked polystyrene nanofibers (Pd@CPS) as an efficient and stable heterogeneous palladium catalyst. The catalytic activities and recyclabilities of the prepared Pd@CPS catalyst have been evaluated by using Suzuki and Heck reactions of various aromatic halides separately with phenylboronic acid and alkenes. The Pd@CPS exhibited high‐catalytic activities for the Suzuki and Heck reactions of aromatic iodides to afford the products in excellent yields (coupling yields >88%). The catalytic activities and the nanofiber structure remained essentially unchanged even after recycling for five times. The high activities and stabilities of the prepared Pd@CPS catalyst can be attributed to the ultrafine fiber and embedment of palladium active species inside the nanofibers.

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In situinvestigation of the kinetics and microstructure during photopolymerization by positron annihilation technique and NIR-photorheology

Abstract: Positron annihilation lifetime spectroscopy is a sensitive tool for thein situstudy of the microstructural evolution during photopolymerization.

Cited by 14 publications

References 43 publications

A Simple and Efficient Model to Determine the Photonic Parameters of a Photopolymerizable Resin Usable in 3D Printing

A Simple and Efficient Model to Determine the Photonic Parameters of a Photopolymerizable Resin Usable in 3D Printing

Sulfonated and cross‐linked polystyrene ultrafine fibers for the esterification of palmitic acid for biodiesel production

Palladium complex embedded crosslinked polystyrene nanofibers as a green and efficient heterogeneous catalyst for coupling reactions

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