Positron Annihilation Studies of Physical Ageing in Polycarbonate

Davis, William J.; Pethrick, Richard A.

doi:10.1016/s0014-3057(98)00046-9

Cited by 22 publications

(14 citation statements)

References 19 publications

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“…It is clear from this figure that the relaxation function also represents two exponentially decaying curves similar to I 3 behaviour. However, recent studies13, 14 argue that the decrease in o ‐Ps intensity I 3 in isothermal annealing experiments may be due to the charging effects of the continuous irradiation of the polymer if the polymer is non‐polar in character and suggests that τ 3 would be a better candidate for ageing studies. Keeping this argument in mind, we have constructed the relaxation function ϕ( t ) by making use of the ratio ( S / V f3 ) where S is the surface area given by the relationship30 I 3 = 3.0 + 0.0333 S and V f3 , the free volume size calculated from eq 1.…”

Section: Resultsmentioning

confidence: 99%

“…Structural relaxation studies using volumetric, dynamic mechanical spectroscopy, creep and positron data (Reference 13 and references therein) on a quenched solid polymer can be described in terms of a linear function of logarithmic ageing time. However, more complicated forms in time dependence are usually required for data collected over an extended time and if the temperature is around T g .…”

Section: Resultsmentioning

confidence: 99%

“…Several techniques like impact testing,9 differential scanning calorimetry (DSC),3 tensile testing10 and dynamic mechanical spectroscopy3, 10 have been used to study the physical ageing processes in polymers. In recent times, positron annihilation lifetime spectroscopy (PALS) has also been used for this kind of study by monitoring the free volume during physical ageing 11–16. The following is a brief outline of PALS.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Structural relaxation in poly(ethylene terephthalate) studied by positron annihilation lifetime spectroscopy

Paladugu

Shariff

Thimmegowda

et al. 2002

Polymer International

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Positron lifetime technique was used to study the physical ageing process in poly(ethylene terephthalate) (PET). Positron lifetime results show that the structural relaxation processes in PET encompass two different time regimes, one short and the other long. The relaxation function constructed from the measured o‐Ps intensity I3 exhibits non‐exponential character, which can be best fitted with two additive exponentials. The Narayanaswamy model (Kohlraush‐William Watt (KWW) function) is invoked to extract the stretching parameter β indicating the extent of deviation from exponential relaxation. Based on the relaxation times, the activation energies calculated seem to label the different kinetic units of PET structure participating in the relaxation process. © 2002 Society of Chemical Industry

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Structural relaxation in poly(ethylene terephthalate) studied by positron annihilation lifetime spectroscopy

Paladugu

Shariff

Thimmegowda

et al. 2002

Polymer International

View full text Add to dashboard Cite

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“…The positron annihilation experiments on glassy polycarbonate were used to estimate the values for K

_{12}^{italicg}

/γ. Taking the average value of data found in ten publications, 43–52 a value of 2.5 ×10 −4 cm 3 g −1 K −1 was obtained for K

_{12}^{italicg}

/γ.…”

Section: Resultsmentioning

confidence: 99%

Mobility and solubility of antioxidants and oxygen in glassy polymers. I. Concentration and temperature dependence of antioxidant sorption

Boersma

2003

J of Applied Polymer Sci

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Sorption experiments have been conducted at temperatures between 65 and 135°C using five phenolic antioxidants in polycarbonate at different antioxidant concentrations. A model based on the free volume was used to predict the mobility of the additives. In this model, the ratio of the specific volume of a jumping unit to the free volume available in the polymer determines the diffusion behavior of the additives. It was found that the mobility of the antioxidant was predicted accurately using literature and experimental data on the free volume in polycarbonate. Furthermore, the solubility of the antioxidants was predicted very well, based on thermodynamic considerations.

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“…Concerning o-Ps intensity, it has been argued that the decrease in o-Ps intensity I 3 may be due to the charging effect of the accumulation positron irradiation of the polymer [24,39,46]. In this work, the purpose of recording each positron spectra with 1.2×10 6 counts was to eliminate the charging effect, so the effect from positron source would not be considered.…”

Section: The Variation Of Free Volume During Natural Weatheringmentioning

confidence: 99%

Microstructure studies of isotactic polypropylene under natural weathering by positron annihilation lifetime spectroscopy

Zhu

Liao

et al. 2015

J Polym Res

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The microstructure evolution of isotactic polypropylene (PP) exposed to subtropical humid climate of Guangzhou of China, were investigated by gel permeation chromatography, Fourier transform infrared spectroscopy, differential scanning calorimeter, dynamic mechanical analysis and positron annihilation lifetime spectroscopy. Positron data showed that the free volume of PP matrix decreased with involving a shrinking of the free volume hole sizes as the extent of weathering degradation of PP aggravated. The shrinkage of free volume hole sizes may be traced to the loss of mobility of molecules of PP matrix. The increase of the glass transition temperature substantiated undoubtedly the decrease of molecular mobility of PP chains. The increase in crystallinity might increase the amount of rigid amorphous fraction of PP matrix, which induced the loss of molecular mobility. Furthermore, the decrease of orthopositronium formation ought to be correlated to the increase in crystallinity and the increasing amount of scavenchers which were in this work represented by the carbonyl groups.

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Positron Annihilation Studies of Physical Ageing in Polycarbonate

Cited by 22 publications

References 19 publications

Structural relaxation in poly(ethylene terephthalate) studied by positron annihilation lifetime spectroscopy

Structural relaxation in poly(ethylene terephthalate) studied by positron annihilation lifetime spectroscopy

Mobility and solubility of antioxidants and oxygen in glassy polymers. I. Concentration and temperature dependence of antioxidant sorption

Microstructure studies of isotactic polypropylene under natural weathering by positron annihilation lifetime spectroscopy

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