Oligomer formation in the radiation-induced polymerization of styrene

Harayma, Hiroshi; Al-Sheikhly, Mohamad; Silverman, Joseph H.

doi:10.1016/j.radphyschem.2003.06.001

Cited by 5 publications

(3 citation statements)

References 16 publications

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“…The main spectral feature observed is an absorption band with a maximum of approximately 315 nm to 320 nm. This observation generally agrees with results reported elsewhere (47, 48). The capture of the solvated electrons by styrene to produce styrene anion and cation radicals is extremely fast (49).…”

Section: Resultssupporting

confidence: 94%

Mechanisms and Characterization of the Pulsed Electron-Induced Grafting of Styrene onto Poly(tetrafluoroethylene-co-hexafluoropropylene) to Prepare a Polymer Electrolyte Membrane

et al. 2018

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During the pulsed-electron beam direct grafting of neat styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) substrate, the radiolytically-produced styryl and carbon-centered FEP radicals undergo various desired and undesired competing reactions. In this study, a high-dose rate is used to impede the undesired free radical homopolymerization of styrene and ensure uniform covalent grafting through 125-μm FEP films. This outweighs the enhancement of the undesired crosslinking reactions of carbon-centered FEP radicals and the dimerization of the styryl radicals. The degree of uniform grafting through 125-μm FEP films increases from ≈8%, immediately after pulsed electron irradiation to 33% with the subsequent thermal treatment exceeding the glass transition temperature of FEP of 39°C. On the contrary, steady-state radiolysis using Co gamma radiolysis, shows that the undesired homopolymerization of the styrene has become the predominant reaction with a negligible degree of grafting. Time-resolved fast kinetic measurements on pulsed neat styrene show that the styryl radicals undergo fast decays via propagation homopolymerization and termination reactions at an observed reaction rate constant of 5 × 10 l · mol · s. The proton conductivity of 25-μm film at 80°C is 0.29 ± 0.01 s cm and 0.007 s cm at relative humidity of 92% and 28%, respectively. The aims of this work are: 1. electrolyte membranes are prepared via grafting initiated by a pulsed electron beam; 2. postirradiation heat-treated membranes are uniformly grafted, ideal for industry; 3. High dose rate is the primary parameter to promote the desired reactions; 4. measurement of kinetics of undesired radiation-induced styrene homopolymerization; and 5. The conductivity of prepared membranes is on par or higher than industry standards.

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Section: Resultssupporting

confidence: 94%

Mechanisms and Characterization of the Pulsed Electron-Induced Grafting of Styrene onto Poly(tetrafluoroethylene-co-hexafluoropropylene) to Prepare a Polymer Electrolyte Membrane

et al. 2018

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“…The generally accepted mechanism of this thermally initiated free‐radical polymerization comprising the formation of the main dimers and trimers can be described as shown in Scheme 1–5. Recently, the formation of oligomers has been of special interest in radiation‐induced styrene polymerization and gas‐phase thermal polymerization of styrene and in theoretical calculations of the mechanism of the self‐initiated thermal polymerization of styrene 6–8…”

Section: Introductionmentioning

confidence: 99%

Effects of styrene oligomers and polymers on the suspension polymerization behavior and properties of expandable polystyrene

Schellenberg

2008

J of Applied Polymer Sci

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Styrene oligomers are formed by a free-radical mechanism during the thermal polymerization of styrene in storage. The effects of these compounds on the preparation of expandable polystyrene (EPS) were investigated with respect to suspension polymerization behavior and the properties of the impregnated polystyrene beads produced. Styrene dimers and trimers up to concentrations of 0.2 wt % did not affect the stability of the suspension during the polymerization and impregnation stages. Besides differentiated effects on the particle size distributions of the polymers and on the polymerization rate, no chain-transfer activity of the oligomers was observed, and this confirmed the assignment of chain transfer to the Diels-Alder dimer in the literature. The investigation of the foaming behavior of the pentane-impregnated EPS beads indicated a significant reduction of the prefoaming density caused by styrene dimers and trimers. This behavior resulted from a decrease in the glass-transition temperatures of these polymers. The effects of high-molecularweight polystyrene, formed in addition to oligomers during storage by the thermal polymerization of styrene, on the polymerization behavior and polymer properties of EPS were also investigated. The results showed a significant impact on the suspension stability that was dependent on the concentration of the high-molecular-weight polystyrene.

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“…IDT show minimum values for the samples exposed to maximum dose (10.5 MGy) of high intensity irradiation. This may be due to formation of more oligomers (molecular complex that consists of few monomers) [17] due to high intensity of irradiation. These oligomers exhibit early thermal decomposition.…”

Section: Tga Analysismentioning

confidence: 99%

Gamma-Irradiation of E-Glass/Epoxy Composite: A Study of its Mechanical and Thermal Sustainability

Chakraverty

Beura

Mohanty

et al. 2020

MSF

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Glass fibre reinforced epoxy (GRE) composites, used as mechanical support and thermal insulators for superconducting magnets of fusion reactors, have been exposed to gamma irradiations at both higher and lower order ranges of doses. Hand layed E-glass fibre/epoxy composite samples, exposed to gamma-irradiations of cumulative doses of both low strength (10, 20, 30, 40, 50 and 60 kGy) and high strength (0.5, 2.5, 6.5, 8.5 and 10.5 MGy) reveal a huge lowering of the ILSS (inter laminar shear strength) for its exposure to low strength dose irradiation. However, improved ILSS values are recorded for high dose exposures. At both high and low doses of exposure to irradiation the Tg (glass transition temperature) got improved initially with a decreasing trend towards the later stages of exposures. Thermo-gravimetric analysis (TGA) test reveals lowest initial decomposition temperature (IDT) for the composite sample irradiated to maximum dose (10.5 MGy). Activation energy () values of gamma-irradiated composite samples for thermal decomposition were found less compared to that for as-cured composite. FTIR spectra of irradiated samples reveal formation of oligomers confirming the trend of activation energy of irradiated composite. FESEM fractographs of the irradiated composite fracture samples reveal several modes of failure.

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Oligomer formation in the radiation-induced polymerization of styrene

Cited by 5 publications

References 16 publications

Mechanisms and Characterization of the Pulsed Electron-Induced Grafting of Styrene onto Poly(tetrafluoroethylene-co-hexafluoropropylene) to Prepare a Polymer Electrolyte Membrane

Mechanisms and Characterization of the Pulsed Electron-Induced Grafting of Styrene onto Poly(tetrafluoroethylene-co-hexafluoropropylene) to Prepare a Polymer Electrolyte Membrane

Effects of styrene oligomers and polymers on the suspension polymerization behavior and properties of expandable polystyrene

Gamma-Irradiation of E-Glass/Epoxy Composite: A Study of its Mechanical and Thermal Sustainability

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