Structure dependence of gamma ray irradiation effects on polyurethane and epoxy resin studied by PAL technique

Positron annihilation lifetime (PAL) technique has been employed tostudy the microstructural changes of polyurethane (PU), EUXIT 101and epoxy risen (EP), EUXIT 60 by Gamma-ray irradiation with thedose range (95.76 - 957.6) kGy. The size of the free volume hole andtheir fraction in PU and EP were determined from ortho-positroniumlifetime component and its intensity in the measured lifetime spectra.The results show that the irradiation causes significant changes in thefree volume hole size (Vh) and the fractional free volume (Fh), andthereby the microstructure of PU and EP. The results indicate thatthe γ-dose increases the crystallinity in the amorphous regions of PUand increase the cross-linking of EP.

Correlation between the ion permeation and free volume property in ethyl cellulose film during the acid treatment

A correlation between the ion permeation and free-volume hole size was found by theoretical deduction and confirmed by the corresponding experiment.

Positron Annihilation Characterization of TiO2 Doped Polystyrene

TiO2 doped polystyrene thin films fabricated by solution cast method. The effect of dopant concentrations has been studied for the structural, morphological, optical and defects properties. The XRD results revealed that the degree of crystallinity remains largely invariant due to the presence of the polymer. Interesting results have been obtained from optical measurement which depicted that there is increase in UV-shielding efficiency with the increase in the dopant concentration as the absorbance was found to be maximum in case of UV region. Surface morphology of the films shows a rod like structure for 0.25 wt% of TiO2, while for higher concentrations the TiO2 clusters were obtained. The positron lifetime results reveal that the free volume hole concentration decreased with the increase in TiO2 concentration as intensity of o-positronium decreases with the increase in concentration of TiO2 doping.

Studying the Effect of Low α-Radiation Doses on CR-39 Polymers Using Positron Annihilation Lifetime and Mechanical Properties

Positron annihilation lifetime spectroscopy (PALS) is one of the unique tools for studying free-volume defects in solid media. The microhardness test offers a simple and nondestructive tool for investigating the mechanical behavior of polymer materials. Polyallyl diglycol carbonate (CR-39) track detectors have a variety of applications in science and technology. PALS measurements and microhardness tests were verified for CR-39 irradiated with different doses of alpha particles (0 - 69.20 mGy). The variations in free volume hole size and fractional free volume were obtained by using the PALS method. The small free volume hole sizes were found at doses 27.68 and 44.98 mGy. The microhardness test for the two doses yielded medium values.

Positronium Lifetime Study on Subnanoscopic Structure of Polyrotaxane

The subnanoscopic structures of polyrotaxanes, prepared from α-cyclodextrins, poly(ethylene glycol), and bulky adamantane end groups, were examined by means of the positron annihilation lifetime technique, in consideration of the free-volume hole, quantified from the long-lived ortho-positronium (o-Ps) lifetimes. The influence of the chemical structure on the temperature dependence of the o-Ps lifetimes are discussed.