Investigation of the effects of thermal, oxidative and irradiation treatments on the behavior of poly(ethylene glycol) as a phase change material in thermal energy storage systems

Poly-ethylene glycol (PEG) with an average molecular weight of 2000 g/mol has been investigated as a phase change material for thermal energy storage applications. PEG ests were maintained at 80C for 861 hours in air, nitrogen, and vacuum environment; the samples maintained in vacuum were further treated with air for a period of several weeks. furthermore, another set of PEG samples was exposed to electron radiation in order to modify some of their polymer properties, such as their melting point Tm, their heat of fusion H, their crystallisation temperature T, the experiments showed that the presence of oxygen led to the degradation of the polymer and to a slight decrease of its melting temperature, while the treatment with electron radiation reduced polymer's heat of fusion. FTIR spectrum analysis showed bands assigned to carbony/carboxylate functional groups, indicating the degradation of PEG in the presence of air/oxygen

Synthesis of pH-responsive hydrogel based on PVP grafted with crotonic acid for controlled drug delivery

In the present study polyvinylpyrrolidone (PVP) was grafted with crotonic acid (CrA) in order to obtain novel hydrogels which are pH – responsive. The grafting was performed by mixing the polymer solution with various concentrations of CrA and applying gamma radiation at different doses. The effects of the preparation conditions such as the irradiation dose and CrA concentration on the gelation process and swelling of the synthesized copolymer were investigated. The hydrogel system was used as carrier for a model drug, ketoprofen, the release behaviour of the drug from the hydrogel was monitored in two different release media (pH 1 and pH 7.2), and released amounts of ketoprofen were followed up spectrophotometrically. The release was low in the acidic medium compared to a better and extended release in the neutral medium suggesting the possibility of using this hydrogel as potential drug carrier to allow targeted release in the intestinal medium

Role of molecular architecture in interfacial self-adhesion of polyethylene films

The influence of molecular architecture on interfacial self-adhesion above polyethylene film melt temperature was examined in this study. The investigated molecular structures include molecular weight (Mw), molecular weight distribution, long chain branch amount and distribution and short chain branch among and along polyethylene chains. The long chain branches concentration was quantified using gel permeation chromatography and short branches concentration using nuclear magnetic resonance techniques. The adhesion strength was measured immediately after melt bonding using a T-Peel test. The results showed that increasing Mw resulted in higher adhesion strength in linear metallocene ethylene α-olefins. Low long chain branch concentrations hinder reptation motion and diffusion, and result in lower adhesion strength. Low density polyethylene with highly branched chains yielded very low self-adhesion. A drastic difference in adhesion strength between metallocene and conventional linear low density polyethylene is attributed to homogeneity versus heterogeneity of composition distribution. The low interfacial self-adhesion in conventional polyethylene was concluded to be due to enrichment of highly branched low molecular weight chains at the film surface. These segregated chains at the interface diffuse before the high molecular weight chains located in the bulk. </jats:p

Migration of strontium, cesium, europium and uranium from poly(methyl styrene)- and polystyrene - phosphate composites prepared using gamma radiation

Composites consisting of natural phosphate powder and two monomers (styrene or methyl styrene) have been prepared by means of gamma irradiation. The polymerization reaction was followed up using a thermogravimetric analyzer (TGA) to determine the conversion of the polymerization. Differential scanning calorimeter (DSC) was used to locate and determine the glass transition temperature (Tg) of the prepared samples. The distribution of 137Cs, 152Eu, 85Sr and 238U in a solid-aqueous system, composites of phosphate-poly(methyl styrene) and of phosphate-polystyrene in contact with groundwater, was investigated using alfa-spectrometry and fluorometry. The effects of contact time, pH, and the concentration of concurrent element (Ca) were studied. The results were compared with earlier results with phosphate alone in the solid phase. The ability of the produced composites to keep the studied radioisotopes in the solid phase is much higher than in the mineral phosphate. This improvement is more remarkable for strontium and cesium than for europium and uranium, due to their high element ratio in the solid phase in phosphate experiments

Sorption and migration of Cs, Sr, and Eu in gypsum - groundwater system

The distribution of 137Cs, 152Eu, and 85Sr in a solid/aqueous system, gypsum in contact with groundwater, was investigated using gamma-spectrometry. The sorption and migration of the radionuclides were investigated. The aqueous phase was characterized using instrumental neutron activation analysis (INAA) and high performance liquid chromatography (HPLC). The solid phases were characterized using X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The investigations included three kinds of gypsum: mineral, commercial, and own prepared gypsum. The influence of some parameters on sorption/migration of the radionuclides were studied, such as contact time, pH, and concentrations of concurrent elements. The effect of element concentration was also investigated. The results show the ability of gypsum to keep Sr and Eu in the solid phase in all three cases. The incorporation of Cs in the solid phase depends on the conditions and used materials, and varies between 93 and 97%

Optical Limiting Behavior of Acid Blue 29 under a Low Power CW He-Ne Laser Irradiation

Optical limiting performances of acid blue 29 are investigated under irradiation by a 35 mW continuous wave He-Ne laser. The optical limiting behavior is investigated by using transmission measurement through samples with different concentrations. Our results show that the optical limiting efficiency is concentrations dependence. Induced self-diffraction patterns are observed at relatively high intensities starting from 15 mW