D. P. Gupta
|PUBLISHED DATE||September 05, 2016|
|PUBLISHER||The Author(s) 2016. This article is published with open access at www.chitkara.edu.in/ publications|
The UV-Visible absorption spectra of CR-39 polymer, unirradiated and irradiated to gamma radiation up to 500 kGy dose were studied. The development of new peaks, shifting of absorption bands and their broadening as a result of gamma irradiation were observed and analyzed. The values of optical constant like direct and indirect band gaps have been determined. The values of indirect band gap have been found to have lower values then the corresponding values of direct band gap. The increase in carbon conjugation length and size of carbon clusters has also been pointed out from the results of UV-Visible spectroscopy.
CR-39 is a polymer formed from diallyl monomer made by polymerization of diethyleneglycol bis allylcarbonate (ADC) in presence of diisopropyl peroxydicarbonate (IPP) initiater. The presence of the allyl groups allows the polymer to form cross- links; therefore, it is a thermoset resin. CR-39 is transparent in the visible spectrum and is almost completely opaque in the UV range. It has high abrasion /scratch resistance and has weight about half of the glass. It is an advantageous material for making eyeglasses and sunglasses. CR-39 is also resistant to most solvents and other chemicals, and to material fatigue. It is also used in a number of industrial and medical applications. The most recent studies with CR-39 involve neutron gamma and high energy ion irradiation induced changes in its structure and properties.
The ion irradiation of polymers with X-rays/ γ-rays or swift heavy ions deposit high amount of energy in the polymers along the track of their passage creating the formation of free radicals, ion tracks, cross linking, evolution of volatile species (1–3). Chong et al. (4) has been made a study on the UV-VIS and FTIR spectra of CR-39 plastics irradiated with 50 kVp tube X-rays in the dose range 0 and 45 MR. The optical transmittance over the wavelength region of 200–1000 nm was found to decrease with the X-ray exposure, much greater decrease being observed in the UV region. The IR absorption spectra of the irradiated samples show the presence of two new strong absorption bands at the frequencies 655 and 2340 cm−1 i.e. an indicative of the gas CO2 produced inside the plastic. The absorbance of these bands increases linearly with the X-ray dose. Fink et al. made an attempt of FTIR studies on low energy Ar ion irradiated Polycarbonate  using nuclear magnetic resonance spectroscopy. Malek et al. studied the X-ray and γ- ray induced degradation of Cr-39. They studied the diffusion of CO2 with time. Navarro et al (7) showed that PC irradiation is accompanied with the preferential release of carbon monoxide followed by minor production of hydrogen, carbon dioxide and methane.
The effects of 320 keV Ar and 130 keV He ions at fluences ranging from 1 × 1013 to 2 × 1016 ions/cm2 ion-beam bombardment on the physical and chemical properties of poly CR-39 have been investigated by Abdul-Kader et al. (8). UV–VIS spectra of bombarded samples reveal that the optical band gap decreases with increasing ion fluence for both Ar and He ions. In the FTIR spectra, changes in the intensity of the bands on irradiation relative to pristine samples occurred with the appearance of new bands. XRD analyses showed that the degree of ordering of the CR-39 polymer is dependent on the ion fluence. Changes of surface layer composition and an increase in the number of carbonaceous clusters produced important change in the energy gap and the surface wettability. The surface hardness increased from 10.54 MPa for pristine samples to 28.98 and 23.35 MPa for samples bombarded with Ar and He ions at the highest fluence, respectively. The physical and chemical properties of polymer electrolyte (PEO-CdCl2) films irradiated with γ- rays were investigated by Raghu et al. (9). The degradation of the irradiated films was observed mainly due to chain scission/cross linking. The thermal stability and crystallinity were also found to decrease significantly. As a result of γ- ray irradiation a destruction of the polymer polypropylene lead to the formation of ketonic and alcoholic groups(10). In the polymer polyacetate, elimination of carbon dioxide was observed due to damage of the ester group. In polycarbonate, at the dose 106Gy, formation of phenolic group was observed due to cleavage of ester bonds. In PVC, The FTIR spectral studies indicated the formation of C=C bond with the simultaneous reduction in the concentration of C-Cl bond when irradiated to γ- radiation (10).
In the present work we investigated physical and chemical response of γ-radiation on CR-39 polymer, specially the modification in the optical, chemical and structural properties through UV/Vis spectrometry.
|ISSN||Print : 2349-7564, Online : 2349-7769|
The present study reveals the presence of many secondary metabolites in the root extracts of Dalbergia Sisso (Roxb.). It has also confirmed that the root extracts of Dalbergia Sisso (Roxb.) could be used for the treatment of various infections. The root extracts of Dalbergia Sisso (Roxb.) have potent antibacterial activity when compared with conventionally used drugs and is almost equipotent to the standard (gentamycin) antibacterial drug. The results lend credence to the folkloric use of the root of Dalbergia Sisso (Roxb.) in treating bacterial infection and show that Dalbergia Sisso (Roxb.) may be explored for its further phytochemical profile to identify the active constituents responsible for their use as potent antibacterial agents.