Dielectric relaxation and crosslinking in unsaturated polyester resins

Learmonth, G. S.; Pritchard, Geoffrey

doi:10.1002/app.1969.070131009

Cited by 19 publications

(2 citation statements)

References 10 publications

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“…Figure also reveals that the wavelength of the plasmon resonance absorption peak is blue-shifted as the peak grows. This is unexpected because plasmon resonance is usually slightly red-shifted as the particle size increases. ,, In addition, during polymerization of vinyl monomers, the refractive index of the medium increases − and an increase in the refractive index of the medium suspending the silver particles also normally causes a red-shift. , However, if the particles become more spherical, then a blue shift is expected . In addition, the breadth of the absorption appears to narrow, and this is particularly noticeable after 30 s of irradiation.…”

Section: Resultsmentioning

confidence: 99%

Simultaneous Photoinduced Silver Nanoparticles Formation and Cationic Polymerization of Divinyl Ethers

et al. 2011

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The cationic photopolymerization of triethylene glycol divinyl ether and concomitant formation of silver particles by the use of radical photoinitiators (BAPO and BEE) and an organosoluble silver salt (AgSbF6) are reported for the first time. The rate of photopolymerization is increased with higher concentrations of BEE, but the effect of AgSbF6 concentration is more complex. A localized surface plasmon resonance due to the formation of silver particles was observed very shortly after the commencement of irradiation, and the maximum absorption was found to increase with irradiation time as the particle concentration and size grew. The simultaneous formation of the polymer also stabilizes the particles and prevents their agglomeration. After a certain irradiation period, the maximum absorption reaches a plateau, prior to depletion of either silver ion or photoinitiator, suggesting that the formation of the polymer matrix may restrict silver particle growth. TEM studies reveal the presence of ∼10 nm diameter, crystalline silver nanoparticles, and SAXS also confirms the presence of these nanoparticles.

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Section: Resultsmentioning

confidence: 99%

Simultaneous Photoinduced Silver Nanoparticles Formation and Cationic Polymerization of Divinyl Ethers

et al. 2011

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“…The kinetics of thermosetting reactions ha\re been studied with the help of swelling measurements ( 18,19), spectroscopic analysis (20,21), rheological measurenieiits (22)(23)(24) , torsional and flexural braid analysis (25)(26)(27), electrical conductivity measurements (20,28), and a variety of other techniques.…”

Section: Kinetic and Thermal Characteristics Of Thermoset Systemsmentioning

confidence: 99%

Thermoset characterization for moldability analysis

Kamal

1974

Polymer Engineering & Sci

599

310

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The injection molding of thermosetting compounds involves complex interactions between material parameters and molding conditions, on one hand, and moldability and the ultimate properties of molded parts, on the other hand. The main role of the molding variables may be related to their effects on the cure time and temperature and on the flow and thermal phenomena that affect orientation and residual stresses. These effects are manifested in the ultimate mechanical properties and shrinkage of the molded articles. Only scattered empirical data are available on the effects of material parameters, like the basic kinetic, thermal, rheological, and pressure‐volume‐temperature properties of thermosetting compounds. The lack of useful information in this area may be related to the unavailability of sufficient, satisfactory data on the above properties. This situation has also resulted in limitations on meaningful work towards the mathematical modelling of the molding process, which would be useful for the optimization of production rates and product quality. The paper summarizes the status of work in this area with emphasis on recent results relating to kinetic, thermal, and rheological characterization of thermosetting molding compounds.

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Dielectric spectroscopic study of wood plastic combinations

Hedvig¹,

Czvikovszky²

1972

Angew. Makromol. Chem.

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Curing of wood-polyester combinations was studied by recording dielectric spectra as a function of temperature at fixed frequency at different stages of cure and as function of cure-time at fixed temperature. The measurements were performed by a specially constructed continuously recording spectrometer equipped with linear temperature program. By measuring the shifts of the dielectric transition temperatures it was possible to follow changes of the molecular mobilities in the resin as crosslinking proceeded. By measuring the relative intensities of the dielectric absorption the change of the concentration of the polar groups as a function of cure time could be followed. The existence of a stepwiso aftercuring was revealed. ZUSAMMENFASSUNG :Aushartungsprozesse von Holz-Polyester-Kombinationen wurden untersucht mit Hilfe von dielektrischen Spektren in Abhangigkeit von der Temperatur bei konstanter Frequenz in verschiedenen Stufen der Konversion einerseits und in Abhiingigkeit von der Aushiirtungsdauer bei konstanter Temperatur andererseits. Die Untersuchungen wurden mit einem selbstkonstruierten, kontinuierlich schreibenden Spektrometer ausgefiihrt, das mit einem Linear-Temperatur-Programmgeriit ausgeriistet war. Mit der Messung der Verschiebung der dielektrischen tfbergangstemperaturen war es moglich, die Veranderungen des Molekularbeweglichkeitsvermogens in Harzen wiihrend des Vernetzungsprozesses zu verfolgen.Mit der Untersuchung der relativen Intensitlit der dielektrischen Absorption ist die Konzentration der polaren Gruppen in Abhangigkeit von der Aushartungsdauer mel3bar. Eine stufenweise auftretende Nachhiirtung wurde aufgezeigt.Wood-plastic combinations are prepared by conducting polymerization or polycondensation in the framework of wood. The polymerization reaction within wood can be initiated either chemically by using peroxides or by high energy irradiationl. As the reaction proceeds in the solid wood matrix the optical and thermomechanical methods of monitoring it are obviously useless.

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Dielectric relaxation and crosslinking in unsaturated polyester resins

Cited by 19 publications

References 10 publications

Simultaneous Photoinduced Silver Nanoparticles Formation and Cationic Polymerization of Divinyl Ethers

Simultaneous Photoinduced Silver Nanoparticles Formation and Cationic Polymerization of Divinyl Ethers

Thermoset characterization for moldability analysis

Dielectric spectroscopic study of wood plastic combinations

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