Biomedical silicone elastomers have been studied for their potential application as carriers for controlled release of drugs, since these materials display a unique combination of properties, which might be favorable to the above use. A two component silicone gel system was used and various cross-linker ratio was applied, in order to produce networks with varying crosslink density. Swelling experiments in toluene were run in order to evaluate the network characteristics. The silicone elastomer was loaded with salicylic acid and propranolol hydrochloride and their delivery in distilled water was followed. The results showed that release is almost of zero order for high loading of salicylic acid, while delivery seems to be diffusion controlled up to a certain limit. The administered drug concentrations are relatively low if silicone discs are used, due to the hydrophobic nature of this material. On the other hand, when membranes are used with a thickness of 0.1-0.2 mm, then the delivery rate is much higher depending of course on the hydrophilic character of the drug.
Hydrogels were prepared from 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate as cross-linking agent. Two different polymerization techniques were followed, namely bulk polymerization initiated by dibenzoyl peroxide and solution polymerization, in water, using a redox initiator system. Differences in the water desorption from swollen samples between the two types of the above products were recorded and attributed to the fact that those hydrogels were obtained in glassy or rubbery state, according to the polymerization technique. Also, the delivery of salicylic acid from samples of the above types was studied, and a faster release with higher ultimate delivery was displayed by the solution polymerization hydrogels.
Energy consumption in the building sector is responsible for a very large amount of electricity consumption worldwide. The reduction of this consumption is a crucial issue in order to achieve sustainability. The objective of this work is to investigate the use of phase change materials (PCMs) in the building walls in order to reduce the heating and the cooling loads. The novelty of this work is based on the investigation of different scenarios about the position of the PCM layer in the south and the north walls. PCMs can improve the thermal performance and the thermal comfort of a building due to their ability to store large amounts of thermal energy in latent form and so to reduce the temperature fluctuations of the structural components, keeping them within the desired temperature levels. More specifically, this work presents and compares the heating loads, the cooling loads and the temperature distribution of a building in Athens (Greece), with and without PCMs in different positions in the south wall and in the north walls. The simulation is performed with the commercial software TRNSYS 17, using the TRNSYS component: type 1270 (PCM Wall). The results proved that the maximum energy savings per year were achieved by the combination of the insulation and the PCM layer in the north and south walls. More specifically, the reductions in the heating and the cooling loads were found to be 1.54% and 5.90%, respectively. Furthermore, the temperature distribution with the use of a PCM layer is the most acceptable, especially during the summer period.
In this work, two underfloor solar assisted heating systems without and with phase change materials (PCMs) are investigated energetically for a building of 100 m 2 floor area, which is situated in Athens, (Greece). The simulations are conducted with the commercial software TRNSYS 17. More analytically, flat plate collectors coupled to a storage tank are used while there is, in the first system, an auxiliary heater and in the second system, a heat pump, for supplying the extra heating demand when the solar potential is not sufficient. The PCM layer (BioPCM Q29/M91) is situated below the underfloor heating system, which operates with water, in order to increase the storage capacity. Moreover, this study compares the indoor temperature profiles of the building with and without a PCM layer on the floor and specifically in different cases by changing the area of the collectors and the thickness of the insulation layer. The results showed that the electrical energy consumption decreases on average 70% and 41% for the system with an auxiliary heater and for the system with heat pump respectively. Moreover, the application of the PCM layer on the floor in both systems gives an increase of the indoor temperature about 2 o C into the limits of thermal comfort.
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