Photoinitiated polymerization of a dimethacrylate oligomer: 1. Influence of photoinitiator concentration, temperature and light intensity

Lecamp, Laurence; Youssef, B.; Bunel, Claude; Lebaudy, P.

doi:10.1016/s0032-3861(97)00184-5

Cited by 166 publications

(148 citation statements)

References 12 publications

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“…We do not have values for the critical extent of polymerization ( p c ) for gelation, the quantum yield () for the photoinitiator at 325 nm, and reaction rate constants (k i and k p ) which comprise ␣ 2 in Eq. (14). Therefore we use ␣ as a single fitting parameter to match experimental data.…”

Section: Comparison Between Experiments and Theorymentioning

confidence: 99%

“…12,13 Other techniques like photocalorimetry attempt similar evaluations, although the double bond conversion is obtained from enthalpy measurements rather than through FTIR. 14,15 When photoinitiator concentration is varied, photocalorimetry and FTIR give valuable insight into the bulk extent of reaction as a function of photoinitiator concentration. However, they only indirectly track the cure depth.…”

Section: Introductionmentioning

confidence: 99%

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Cure depth in photopolymerization: Experiments and theory

2001

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The depth of photocuring for a model resin system was investigated as a function of photoinitiator concentration. Direct measurements of gel thickness were made from thin films of cross-linked multifunctional methacrylate monomer. The monomer, 2,2-bis{4- [2-hydroxy-3-(methacryloxy)propoxy]phenyl}propane, was polymerized in a solution of trichloroethylene with an ultraviolet laser light source at 325 nm. The monomer solutions were photocured using varying levels of both photonic energy and photoinitiator concentration. An optimal photoinitiator concentration that maximized the gel cure depth was observed. Additionally, two regimes were shown to exist in which the shrinkage (upon solvent removal) was minimized or maximized. A model was developed to probe the physics of the system. Good agreement with experiment was obtained, and the model may be employed to predict both the existence and location of the optimal photoinitiator concentration and the corresponding cure depth. The study showed that photoinitiator plays a significant role in controlling the quality and performance of the formed gel network, with special regard to thickness of cured layers. This has potential application to fields as diverse as industrially cured coatings and dental fillings, and more generally, 3-dimensional rapid prototyping techniques.

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Section: Comparison Between Experiments and Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cure depth in photopolymerization: Experiments and theory

2001

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“…A high-temperature environment generates polymers with certain characteristics: A higher compressive strength; a diminished permeability to chemical agents due to an altered diffusion pattern, and a reduction of the diffusion rate of penetrants; a high Knoop hardness; 5 a better degree of conversion as seen in evaluations performed in a differential thermal analyzer; 18 and in FTIR spectroscopy: [19][20][21][22][23] a high resistance to folding; 20 a high initial reaction rate and consequently an initial free excess volume that improves the final conversion degree and decreases contraction stress generated; 21,24,25 an increase in the maximum conversion rate 22 as well as a higher conversion at the maximum rate and a delay in self-deceleration during the cure process; 26 an increase in 25 and greater structural heterogeneity. 27 Light-initiated polymerizations have a high initial reaction rate.…”

Section: Discussionmentioning

confidence: 99%

“…27 Light-initiated polymerizations have a high initial reaction rate. 24 However, with the continuity of the reaction, the mobility of the reactive species becomes even smaller and the propagation of the reaction becomes diffuse-limited, i.e., even if there are free radicals and monomers, they cannot react because they cannot move within the mass reactant. This phenomenon is called selfdeceleration and is responsible for the considerable drop in reaction rate.…”

Section: Discussionmentioning

confidence: 99%

Effect of the Curing Temperature of Dental Composites evaluated with a Fluorescent Dye

Silva-Jñnior

Lizarelli

Bagnato

et al. 2018

The Journal of Contemporary Dental Practice

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Aim: With the development of the light-emitting diode (LED) to photo-activate composite resin, greater intensities could be reached without greater elevation of temperature in the mass of the composite resin and in the dental structure arisen from the irradiance in comparison to halogen equipments. This new scenario created a necessity to investigate the influence of temperature over the composite polymerization. Materials and methods:Several curing temperatures 25, 50, 75, and 100°C) were used to polymerize a composite resin (Filtek Z250, 3M ESPE) for 40 and 60 s, using the halogen equipment Gnatus Optilight Digital (halogen) and two LEDs that use a new technology to assembly the diodes: LEC 1000 and bright LEC (MM Optics) (LED 1 and LED 2 respectively). The influence of curing temperature, added by the other variables studied, was evaluated using a methodology developed and improved at IFSC/USP, in which the penetration of a fluorescent dye in the body of the photopolymerized composite resin was quantified using fluorescence spectroscopy.Results: According to the final data submitted to an analysis of variance, the presence of two groups of results could be verified: Between 0 and 25°C, both had a great percentage of the dye penetration compared with other Tcure with a variation in penetration from 69.26 ± 8.19% to 90.99 ± 3.38%. In this analysis, the effects of time and temperature were highly notable (p < 0.05) and the lesser value of dye penetration took place at 60 s of photoactivation This penetration was, in average, smaller with the Tcure of 25°C. The results showed that there was an Araraquara, 14801903, São Paulo, Brazil, e-mail: macieljr@hotmail.com interaction between the equipment and time and between time and temperature; the other group is regarding the Tcure was from 50, 75, and 100°C, despite the p = 0.05, the effect of temperature was notable. The penetration of the dye ranged from 8.87 ± 3.55 to 39.47 ± 8.9%. The effects of equipment and time were highly notable. The penetration with the time of 60 s was in average smaller. Except with the equipment LED 1, the percentages of the dye penetration were greater with the Tcure of 100°C. The smallest average was the Tcure of 50°C and 60 s of photoactivation. Conclusion:Based on the available data regarding the influence of curing temperature on the polymerization process of composite resins, was possible to concluded that small increments of heat increased the degree of conversion. We can assume that the energy supply through the generation of heat by the photopolymerizing devices can function as a heating medium for the reagent system by reducing its viscosity and increasing the mobility and agitation of its components. Clinical significance:The dentist must be aware of the effects that exist between the activation devices on the light output and their heat transmission to the composite and the tooth itself. This heat transmission might create a polymer with better characteristics.

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“…In the short-term, resin composite does not undergo spontaneous thermal polymerisation until temperatures of 140°C to 200°C, 34 and reactant evaporation and photoinitiator degradation does not occur until nearly 90°C. 35,36 However, concern exists that, under prolonged heating, certain low molecular weight components of the photoinitiator system could be volatilised, potentially compromising subsequent light polymerisation. Trujillo 34 reported that after eight hours storage, at 54.5°C, hybrid composite exhibited reduced immediate conversion when light polymerised when compared with control samples that had been stored at room temperature, whereas storage at the same temperature for four hours had no adverse effect.…”

Section: Discussionmentioning

confidence: 99%