Thermal-insulation performance of low density polyethylene (LDPE) foams: Comparison between two radiation thermal conductivity models

The loss of energy especially in industrial and residential buildings is one of the main reasons of increased energy consumption. Improving the thermal insulation properties of materials is a fundamental method for reducing the energy losses. Polymeric foams are introduced as materials with excellent thermal insulation properties for this purpose. In the present study, a deep theoretical investigation is performed on the overall thermal conductivity of low-density polyethylene (LDPE) foams. The thermal conductivity by radiation is predicted using two different methods. The most appropriate model is selected in comparison with experimental results. The results show that the theoretical model has an appropriate agreement with the experimental results. The effects of foam characteristics including foam density, cell size, and cell wall thickness on the overall thermal conductivity are investigated. The results indicate that by decreasing the cell size and increasing the cell wall thickness, the overall thermal conductivity is decreased significantly. Also, there is an optimum foam density in order to achieve the smallest thermal conductivity. The lowest overall thermal conductivity achieved in the studied ranges is 30 mW/mK at foam density of 37.5 kg.m-3, cell size of 100 μm, and cell wall thickness of 6 μm

Innovative Applications of Polymeric Foams

The new open Special Issue of Materials, entitled “Innovative Applications of Polymeric Foams”, aims to highlight original and review papers on new scientific and applied research and provide outstanding contributions to inform the community’s understanding of innovative applications of polymeric foams [...

Experimental Study on Oriented Mechanical, Rheological and Optical of a Multi-Walled Carbon Nanotube/Polymethyl Methacrylate Anisotropic Nanocomposite

In order to achieve better mechanical properties of the nanocomposites containing carbon nanotubes, the carbon nanotubes should be oriented in a specific direction in the polymer matrix. This produces nanocomposites with anisotropic properties. Experimental study on the effect of injection direction and carbon nanotubes orientation on the mechanical properties of a multi-walled carbon nanotube (MWCNT)/polymethyl methacrylate (PMMA) anisotropic nanocomposite is the main aim of this article. Therefore, variable input factors including MWCNT concentration (0, 0.5, 1 and 1.5 wt%) and its in-flow and perpendicular directions were studied. First, nanocomposites were produced by co-rotating twin-screw extrusion. After that the nanocomposite sheets were fabricated by injection molding and test samples were cut into standard dimensions by laser cutting. The parameters including elastic module, yield strength, elongation, impact strength and hardness were studied. In addition, the effect of MWCNT on the melt flow index and optical properties was studied. Morphology of nanocomposites was carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Increasing the elastic modulus by about 51%, tensile strength by 19% and elongation by 27% with addition of 1.5 %wt MWCNTs were also found. The results also illustrated that the elastic modulus improved by 10% and tensile strength by 13 % in the direction perpendicular to the flow direction. Yet more elongation was observed in in-flow direction. A little drop in hardness, a slight increase in impact strength and a decrease in luster and transparency by increases in MWCNTs loading were other noticeable results. A reduction in melt flow impact from 11 to 6.3 g/10min was another remarkable finding

Polyurethane Foam Waste Upcycling into an Efficient and Low Pollutant Gasification Syngas

Waste treatment has attracted much attention and, in this regard, gasification processes offer an efficient thermochemical technique that can produce a syngas rich in hydrogen. This technique has been well developed for solid waste and biomass while investigations on gasification of polymeric foam are rare. Therefore, this study explores the treatment of polyurethane foam waste with different gasifying agents, based on thermodynamic modeling. The polymeric foam gasification was developed using the best model for estimating higher heating value (gross calorific value). As the results indicated, models based on both ultimate and proximate analyses had better performance in predicting higher heating value. As one of the main objectives and novelties, the steam and air gasification performance of flexible and rigid polyurethane foam wastes was investigated and compared from efficiency and CO2 emission viewpoints. Polyurethane foam gasification by steam resulted in higher hydrogen efficiency, led to lower energy efficiency and produced lower CO2 emissions compared to gasification by air. A hydrogen efficiency of 41.4% was obtained for gasification of waste flexible polyurethane foam by steam. An energy efficiency of 76.6% and CO2 emission of 7.43 g per mole of feedstock were attained for waste flexible polyurethane foam gasified by air