Polymeric materials are macromolecules, essentially a combination of numerous repeated subunits. Polymers are innovative and advanced materials that currently have a strong impact on our daily lives. In recent years, polymer use has been prominent due to the materials’ distinctive properties; thus, they entered different fields of science, technology and industrial-biomedical applications.The improvement of photoluminescence, optical and electrical characteristics of non-conducting Poly(methyl methacrylate) (PMMA) films was studied. Upon gamma irradiation of various doses, the photophysical and electrical properties of PMMA films were investigated using photoluminescence spectroscopy, ultraviolet–visible (UV–vis) spectroscopy and the LCR Meter Bridge Circuit technique. The fluorescent response improved the photoluminescence (PL) spectral emission peaks according to gamma values. Strong fluorescence peaks appeared with the highest gamma dose. The UV–Vis results revealed a significant red-shift in the absorption edge as gamma doses increased. This shift exhibits a continuous decrease in the energy band gap values (from 3.50 to 2.60 eV for direct transition and from 3.05 to 1.55 eV for indirect transition). This was due to the formation of carbon clusters, which led to an increase in the electrical conductivity and improved the dielectric parameters of the irradiated PMMA films. Among a variety of measurements presented and discussed in the present study, the electrical measurements showed improved electrical characteristics of gamma-irradiated PMMA films.

In this study, blend of polycarbonate (PC)/polybutylene terephthalate thin films was used. This blend belongs to the class of polymeric solid-state nuclear track detectors. Blend samples were exposed to gamma-rays with different doses (55–355 kGy). The compositional changes, the changes of optical properties, the electrical parameters changes and surface morphology in the gamma irradiated samples were studied. Different techniques were used to study improving the physicochemical properties of the irradiated samples, such as Fourier transform infrared spectroscopy, UV–Visible spectroscopy, LCR Meter Bridge and scanning electron microscope, as well as, the roughness testing. Fourier transform infrared measurements exhibit that the degradation in the polymer chain occurs after irradiation with gamma-rays. This means that some functional groups are the most sensible groups to gamma-rays. UV–Visible spectra of the gamma exposed samples exhibited a shift in the absorbance edge toward the region of higher wavelength. This trend reflects a decrease in the band gap energy, which leads to an increase in the electrical conductivity of the samples. The outcomes of dielectric loss and dielectric constant are sensible parameters for whole frequency range to the changes in the structural and optical behaviors as a result to gamma irradiation. Additionally, the surface changes were discussed.

Physical and chemical alterations induced in Makrofol LT 6-4 Nuclear Track Detector (MK-NTD) films after gamma irradiation with different doses (150-950 kGy) were studied. The induced modifications in irradiated samples were analyzed by various procedures namely: X-ray diffraction (XRD), Fourier-Transform-Infrared (FT-IR) spectroscopy, Photoluminescence (PL) spectroscopy, UV-Visible spectroscopy and electrical measurements, as well. XRD results show a broadening of the XRD peak after gamma irradiation, indicating a change in crystallite size of the irradiated polymeric samples. The spectra of FT-IR show overall changes in the band intensities after gamma irradiation, which indicates degradation and cross-linking of polymer chains at specified doses. The PL emission spectra reveal that the intensities of PL peaks descend with increasing gamma irradiation dose and concern the increase in the number of defects, acceptors and donors. Our UV-Vis results show a shift in the spectra of MK-NTD samples towards longer wavelengths with the increase in the gamma-dose. This shift indicates a reduction in the band gap energy, which, in turn, could be attributed to the formation of defects in the gamma irradiated samples. Additionally, the electrical results show some changes in dielectric constant according to the values of frequencies. Upon irradiation, a considerable increase in the dielectric constant and loss was observed, which could be attributed to the creation of dipoles like (CO)-O-infinity and C-O inside the irradiated polymer.

The influence of low-energy Ar ion beam irradiation on both electrical and optical properties of low-density polyethylene (LDPE) films is presented. The polymer films were bombarded with 320 keV Ar ions with fuences up to 1×1015 cm−2. Electrical properties of LDPE films were measured and the effect of ion bombardment on the DC conductivity, dielectric constant and loss was studied. Optically, the energy gap, the Urbach’s energy and the number of carbon atoms in a cluster were estimated for all polymer samples using the UV–Vis spectrophotometry technique. The obtained results showed slight enhancement in the conductivity and dielectric parameters due to the increase in ion fluence. Meanwhile, the energy gap and the Urbach’s energy values showed significant decrease by increasing the Ar ion fluence. It was found that the ion bombardment induced chain scission in the polymer chain causing some carbonization. An increase in the number of carbon atoms per cluster was also observed.

In the present work, ultra-high-molecular-weight polyethylene (UHMWPE) films were irradiated with 130keV He ions. The fluence of the ion beam was ranged from 1x10(12) to 1x10(16)cm(-2). The chemical, morphological, and crystallite structure changes resulted from the ion bombardment were obtained using different spectroscopic techniques. These techniques were Fourier transform infrared spectrometer, scanning electron microscope, X-ray diffraction, and UV-vis spectrophotometry. The surface free energy for untreated and ion-beam-treated samples was determined by means of contact angle measurements of three different liquids. Our results showed a decrease in the crystallinity of UHMWPE and formation of C=O groups on the polymer surface for modified samples as well. A remarkable shifting in the UV-vis spectra toward lower energy and increase in the optical absorption were observed as the ion fluence increases. Measurements of the contact angle indicate remarkable increase in the surface free energy as a function of ion fluence.

The electrical and thermal properties of gamma-irradiated rubberclay composites based on acrylonitrilebutadiene rubber (NBR) and styrenebutadiene rubber (SBR) have been performed. The rubberclay composites were prepared with different ratios of clay up to 50 phr using melt-mixing and hot-pressing methods. The produced sheets were exposed to gamma rays at dose levels in the range from 25 to 250 kGy. The chemical structure was studied by using FTIR technique, whereas thermal stability was tested using thermogravimetric analysis. Variations in the direct current (DC) conductivity (sigma DC) with both the clay ratio and irradiation dose were studied. The effect of the clay ratio and gamma irradiation on the dielectric constant (epsilon epsilon) and loss (epsilon) has also been investigated. The obtained results show that the thermal stability has been improved as a result of clay loading and gamma irradiation of the rubber samples. Moreover, a significant increase in the values of epsilon and epsilon with increasing both the clay ratio and the irradiation dose has been noticed. The values of epsilon epsilon for NBR samples were found to be greater than that for SBR samples. The study shows that clays could be better than ceramics for the preparation of advanced dielectric polymer composites. (c) 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E198E211, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21263

Different samples of acrylic acid/ acrylonitrile copolymer (AAc -co-AN) were prepared using gamma -radiation. The effect of preparation conditions such as comonomer composition, type of solvent, plasticizer and irradiation dose on copolymer thermal stability, optical properties and electrical measurements of the prepared copolymer were studied. The chemical structure of the (AAc -co-AN) copolymer films was confirmed via FTIR spectroscopy. The difference in comonomer composition showed a slight increase in the electrical parameters in favor of the higher AN content while the higher AAc content showed better thermal stability. MeOH as a solvent lowered the values of optical band gap, band tail width, DC conductivity and dielectric parameters of the copolymer compared with using acetone as a solvent. Poly ethylene glycol (PEG) as a plasticizer had insignificant effect on the properties of the produced copolymer except for the AC measurements where it lowers the dielectric constant and loss. Finally the higher preparation dose the higher the polymer molecular weight and degree of branching which led to higher thermal stability, lower optical and electrical parameters.

Copolymer films of Acrylic acid/ Methyl methacrylate AAc/MMA with comonomer composition of 60/40 was prepared and then irradiated by gamma irradiation.The effect of irradiation on some of the physical properties of the copolymer films was investigated.The dose level ranged from 5 to 200 kGy.The thermo gravimetric analysis (TGA) showed that the thermal stability of the films increased with irradiation dose up to 100 kGy then it started to decrease.The results of the UV-Visible spectroscopy of the films showed a decrease in the values of optical band gap and band tail width with doses starting from 100 kGy.The DC conductivity ( DC ) of the films was found to decrease to about three orders of magnitude from its original value with irradiation dose up to 100 kGy then it started to increase with higher doses.Moreover, the dielectric constant and dielectric loss values were found to increase with dose up to 100 kGy which may be attributed to the increase in the number of dipoles in the films due to the irradiation of the copolymer films in air.The results indicated that crosslinking dominated over chain scission in the copolymer films with irradiation dose up to 100 kGy then at higher doses, chain scission dominated.

Surface free energy of biocompatible polymers is important factor which affects the surface properties such as wetting, adhesion and biocompatibility. In the present work, the change in the surface free energy of ultra-high molecular weight polyethylene (UHMWPE) samples, which is produced by electron beam and gamma ray irradiation were, investigated. Mechanism of the changes in surface free energy induced by irradiations of doses ranging from 25 to 500kGy was studied. FTIR technique was applied for sample analysis. Contact angle measurements showed that wettability and surface free energy of samples have increased with increasing the irradiation dose, where the values of droplet contact angle of the samples decrease gradually with increasing the radiation dose. The increase in the wettability and surface free energy of the irradiated samples are attributed to formation of hydrophilic groups on the polymer surface by the oxidation, which apparently occurs by exposure of irradiated samples to the air.

Preparation of barium titanate (BaTiO3) ceramic powder/ polyvinylidene fluoride (PVDF) composite films has been performed. The obtained BaTiO3/PVDF films were irradiated with 1.5 MeV electron beam (EB) at doses in the range (50-675 kGy). The structure of the unirradiated and irradiated films has been characterized using X-Ray Diffraction (XRD) and Fourier Transformer Infrared (FTIR) techniques. The effect of EB irradiation on the dielectric properties and the conductivity of the prepared films have been studied. The obtained results indicated that the irradiation with EB resulted in a decrease in both the crystallinity and the dielectric constant of the proposed ceramic/polymer composite. Meanwhile, the dielectric loss and the ac conductivity increase with the increasing of the irradiation dose. The present study is a trial to find a simple and suitable method to prepare good dielectric material films for different electronic applications.

The changes in the optical and electrical properties of polycarbonate (PC) films, bombarded with He and Ar ion beams, have been studied. The PC films were divided into two groups where the first group was bombarded with 130keV He ions of fluences ranged from 1×1014cm−2 to 2×1016cm−2, while the second one was bombarded with 320keV Ar of fluences (1×1013cm−2 and 1×1015cm−2). The surface morphology of the unirradiated and irradiated PC films was studied using scanning electron microscopy (SEM) technique. The optical properties of the two groups have been carried out using UV–Vis spectrophotometer and the direct current (DC) electrical conductivity was also performed. The obtained results showed a decrease in the optical energy gap, the optical activation energy and the electrical activation energy with increasing the fluence of both He and Ar ions. Meanwhile, an increase in the DC conductivity was obtained with increasing the fluence of the ions. The bombardment of the PC films with He and Ar ion beams induced formation of carbon clusters near the polymer surface and, also, resulted in scission in the polymer chains.

The effect of gamma irradiation on the optical properties of high-density polyethylene (HDPE) films has been studied. The samples were irradiated with gamma rays to dose levels up to 700 kGy. UV-Vis spectrophotometry measurements were carried out for the unirradiated and gamma irradiated HDPE films. The optical parameters, namely maximum molar absorption coefficient (epsilon(max)), dipole strength (M), transition dipole moment (mu), dipole length (L), oscillator strength (F), energy gap (E(g)) and activation energy (E(a)), were determined as a function of the gamma dose. The obtained results show an increase in the values of epsilon(max), M, mu, L and F with increasing irradiation dose. On the other hand, E(g) and E(a) were found to decrease as the dose increases. The oscillator strength and the energy gap show linear relations, with correlation coefficients more than 99%, as a function of the irradiated dose up to 600 kGy. Therefore, it is possible to use HDPE films as gamma dosimeters in the dose range from 0 to 600 kGy by means of the UV-Vis spectrophotometry technique.

The electrical properties of poly(vinyl) alcohol (PVA) have been improved pronouncedly by doping with chlorophyll (Chl) and gamma irradiation. PVA/Chl films have been prepared and irradiated with γ-rays at dose levels of 10, 20, 30, 50, 70, 100, 150, 200 and 250kGy. The crystalline and chemical structures of the samples have been studied using XRD and FTIR techniques. Also, the direct current electrical conductivity and the dielectric constant and loss have been determined for the proposed samples before and after gamma exposure. It is clearly shown that the electrical conductivity of PVA films was increased two orders of magnitude due to chlorophyll doping and about fifteen times due to gamma irradiation. Considering the dielectric constant and loss, their values were shown to increase significantly due to PVA doping with chlorophyll. The obtained results can be attributed to the existence of the conducting Mg atom, as well as, the conjugated double bonds in the chlorophyll. Moreover, the gamma irradiation of PVA/Chl, over 50kGy, improves also this electrical performance. Therefore, the study suggests the possibility of the utilization of the gamma irradiated PVA/Chl films in different electronic applications.

Electrical conductivity and dielectric parameters of the (BuA/MMA) copolymer films irradiated with 1.5MeV electron beam (EB) have been studied. The samples were irradiated with different doses of the electron beam: 5, 10, 50, 125 and 200kGy. The electrical conductivity of the samples was found to decrease as the irradiation dose increases. The temperature dependence of the direct current (dc) conductivity for unirradiated and irradiated samples has been obtained over a temperature range from 293 to 373K. The activation energy values were calculated for all samples. Moreover, measurements of the dielectric constant, dielectric loss and alternating current (ac) conductivity were performed at a frequency range from 100Hz to 5MHz at room temperature. The results indicated that the EB irradiation has formed some traps in the energy gap, which reduce the movement of the charge carriers. Furthermore, a direct proportional relationship between the activation energy and the irradiation dose was estimated in two regions: below and above the glass transition temperature of the polymer. Dipole relaxation was observed in the samples, and the dose effect was found to shift this relaxation towards higher frequencies.

The preparation process of zinc aluminate (ZnAl(2)O(4)) ceramic powder, as well as the sintering temperature have been consequently governed using scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. A broad exothermic peak in the range 223-310. C is observed due to the crystallization of ZnAl2O4 powder. Then the final resultant powder was irradiated with gamma rays at different doses from 30 to 150 kGy. The effect of gamma irradiation on the structure and the electrical behaviour of ZnAl2O4 ceramics has been obtained. The induced changes in the structure have been studied via SEM, XRD and FTIR spectrometers. The obtained results reveal no changes in the spinel phase of ZnAl2O4, while some displacements of the constituent individual atoms for the irradiated samples are observed. The I-V characteristic curves and the dielectric properties of the prepared ceramic powder have been measured for unirradiated and irradiated samples. These curves exhibit nonlinearity of this type of ceramics, where the dc current gradually increases with the increase in the dose. The irradiation of ZnAl2O4 with gamma radiation was found to increase the nonlinearity of the I-V curves. The dielectric constant and loss were found to decrease as the dose increases. Therefore, the irradiation of ZnAl2O4 with gamma rays can improve its utility as an electronic protector in electrical circuits against sudden overvoltage.

In this work, the effect of electron beam (EB) irradiation on polypropylene (PP) films has been studied via different techniques, namely: x-ray diffraction and UV-Vis absorption spectroscopy. The PP films were irradiated with a 1.5 MeV electron beam at doses of 5, 10, 20, 50, 70, 100 and 120 kGy. The crystallinity of the PP films was found to increase, slightly, by EB irradiation. The changes in the dipole strength, transition dipole moment, oscillator strength, optical band energy gap and activation energy have been investigated as a function of the irradiation dose. The results exhibited an increase in both the dipole moment and the oscillator strength; meanwhile, a decrease was found in both the energy gap and the activation energy with increasing dose. The obtained results explored a linear relation plotted between each of the dipole moment, the oscillator strength and the activation energy and the irradiation dose that showed good correlation coefficients. The results suggest the possible use of this polymer as a dosimeter for electron beams in the dose range of interest (0-120 kGy) by means of UV-Vis spectrophotometry.

Electrical properties of polyethylene terephthalate (PET), irradiated with gamma rays, have been investigated. The PET films were irradiated with high gamma dose levels in the range from 100 to 2000kGy. The changes in the DC (σDC) and the ac (σac) conductivities, with the dose, have been performed. The effect of gamma irradiation on the dielectric constant (ε′) and loss (ε″) has been determined. Also, the dose dependence of the frequency exponent index (S), the resonance frequency (Fc) and the hopping frequency (ωP) have been obtained. The obtained results show that increasing gamma dose leads to slight increase in σDC, σac and ε′, while no change was observed in ε″ value. Meanwhile, S, Fc and ωP are inversely proportional to the dose. Accordingly, the study suggests the possibility of using PET films in electronic components (capacitors, resistors, etc.), especially that operate at high gamma dose environments for the frequency independent applications.

In the present work, the conduction mechanism in the electron-irradiated unplasticized poly(vinyl chloride) (UPVC)/poly(vinyl alcohol) (PVA) films has been investigated by measuring their I−V characteristic curves. The I−V measurements have been carried out at applied electric fields up to 20kV/cm. Specimens of UPVC/PVA of 230μm thickness were irradiated with a 1.5MeV electron beam in air to different doses of 30, 135, 540 and 1080kGy, respectively. The I−V characteristics for the films show a direct proportionality between the current values and the irradiation dose. The temperature dependence of the I−V characteristics (in the temperature range of 293–353K) has also been studied. It has been found that the density of the localized state values is inversely proportional to the irradiation dose. The results reveal a non-ohmic behavior in this regime of temperature range providing the existence of space-charge-limited conduction in UPVC/PVA films.

Post-irradiation studies have been carried out to elucidate the effects of electron beams on the electrical conduction mechanism in high-density polyethylene (HDPE) thin films. The irradiation process was performed in air at room temperature by use of a 1.5 MeV electron accelerator at different doses: 30, 295, 540 and 1080 kGy, respectively. The I–V characteristics for the un-irradiated and irradiated HDPE thin films in the temperature range of 303–373 K and at applied electric fields up to 6×104 V/cm were measured. The results exhibit non-ohmic behavior in this regime and the analysis of data shows the existence of space charge limited conduction in the HDPE thin films. Also, the density of the localized state near the Fermi level was calculated for the samples. In addition, the temperature dependence of the current as a function of dose was studied which implies an increase in the electrical activation energy. In turn, this explains the result that the higher the dose, the higher the mobility obtained.