Free volume change of elongated polyethylene films studied using a positron probe microanalyzer

Oka, Toshitaka; Oshima, Nobuyuki; Suzuki, Ryoichi; Uedono, Akira; Fujinami, Masanori; Kobayashi, Yoshinori

doi:10.1063/1.4766457

Cited by 11 publications

(13 citation statements)

References 32 publications

(29 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Diffusion and reactivity of low-MW molecules/radicals in polymers is of considerable importance. − It is related to the properties of polymeric membranes, (photo)degradation of polymers, permeability, and reactivity of free radicals in polymers. − Obviously, polymers are complex media and their molecular structure and molecular mobility in polymers require a special study. Stable nitroxyl radicals have been used for decades as molecular probes of polymers. , ESR spectra of nitroxyls in polymers usually give info on a rotational diffusion of a low MW compound in a polymer.…”

Section: Introductionmentioning

confidence: 99%

Reactivity of Benzophenone Ketyl Free Radicals in an Elongated Elastomer Film

et al. 2016

View full text Add to dashboard Cite

The effect of polymer film elongation leading to the thinning of the film up to three times on the decay of transients was studied. Kinetics of benzophenone (B) triplet state (3)B* and ketyl free radical BH• in soft rubber poly(ethylene-co-butylene) (abbreviated as E) was investigated by nanosecond laser flash photolysis. We monitored decay kinetics of the triplet state of (3)B* and of BH• decay in the polymer cage and decay of BH• in the polymer bulk. The fast exponential decay of (3)B*(lifetime τT ≈ 200 ns) is accompanied by hydrogen atom abstraction from E with the formation of BH• and a polymer free radical R•. The decay of BH• in the polymer cage occurs during τc ≈ 1 μs. Cage recombination, in turn, was followed by a cross-termination of BH• in the polymer bulk (τb ≈ 100 μs under our conditions) and is characterized by a rate constant kb ≈ 10(8) M(-1) s(-1). We studied changes of rates of transients decay upon elongation (thinning) of E. Decay of (3)B* is practically independent of elongation of the film. Recombination of BH• in the solvent bulk occurs with a two times lower kb than in a nonelongated E. The decrease in kb is ascribed mainly to a lower fractional polymer free volume Vf in elongated E compared with that in nonelongated E. Dependencies of log10 kb versus [Formula: see text], where [Formula: see text] is the thickness of the film, turned out to be linear with a negative slope. At the same [Formula: see text] recombination proceeds slower in the elongated elastomer compared with the nonelongated elastomer. Cage effect increases twice as well due to a lower rate of radicals escape from the polymer cage in the elongated film. We observed relatively large effects of external magnetic field (B = 0.2T) on the kinetics of cage recombination and recombination in the polymer bulk. Magnetic field effect on recombination rates in the cage and in the solvent bulk does not depend on elongation.

show abstract

Section: Introductionmentioning

confidence: 99%

Reactivity of Benzophenone Ketyl Free Radicals in an Elongated Elastomer Film

et al. 2016

View full text Add to dashboard Cite

show abstract

“…29 The key parameters of free volume include free cavity volume (V h ) and free volume fraction (f app ). The former directly relates to the average size of free volume, and the latter reflects the number of free volume sites.…”

Section: Free Volumementioning

confidence: 99%

“…Free volume is an important aspect of aggregate state structure, reecting the packing of the molecule of a matter. 29 The key parameters of free volume include free cavity volume (V h ) and free volume fraction (f app ). The former directly relates to the average size of free volume, and the latter reects the number of free volume sites.…”

Section: Curing Behaviors and Chemical Structures Of Cpes/ce Resinsmentioning

confidence: 99%

Novel tough and thermally stable cyanate ester resins with high flame retardancy, low dielectric loss and constant based on a phenolphthalein type polyarylether sulfone

et al. 2015

View full text Add to dashboard Cite

It still remains a big challenge to improve the toughness and flame retardancy of cyanate ester (CE) resin through a simple and effective method without sacrificing its excellent dielectric properties and thermal stability. New modified CE resins were facilely developed through melt-blending with phenolphthalein type polyarylether sulfone (cPES), and the integrated performances including the reactivity, mechanical, dielectric, thermal and flame retarding properties were systematically investigated. Results show that compared with CE resin, cPES/CE resins have 1.2-3.2 times higher impact strengths according to the concentration of cPES on the base of maintaining good thermal stability, high modulus, low dielectric constant and loss. Through analyzing thermogravimetric kinetics, cone calorimeter tests, structures of chars and pyrolysis gases, it proves that the addition of cPES into CE resin brings greatly increased difficulty of catching fire, reflected by the time to ignition (TTI), fire performance index (FPI) and fire growth index (FGI); while once ignited, cPES/CE resin exhibits a bigger heat release rate and total heat release. These attractive results demonstrate that cPES is a multi-functional modifier of CE resin. The origin behind was systematically revealed through discussing the influence of cPES on the structure of crosslinked network.

show abstract

“…Mono-energetic positron beams are uniquely used for a wide variety of experiments in solid state physics and material science, such as obtaining spatially resolved maps of plastically deformed or irradiated metals [1][2][3][4], non-destructive investigation of thin layers [5], and observing the annealing behavior of defects or free volumes in polymers [6]. In addition, they can be used for studying the Fermi surface and the topmost atomic layers of materials [7].…”

Section: Introductionmentioning

confidence: 99%