Abstract
An artificial aging study of novel heat absorbers based on phase change materials (PCMs) prepared from recycled high-density polyethylene (HDPE), paraffin wax (PW), and expanded graphite (EG) was investigated. The optimal composition of PCMs contained 40 wt% HDPE, whereas the paraffin wax content ranged from 40 to 60 wt% and the expanded graphite content ranged from 5 to 15 wt%. PCMs were artificially aged through exposure to UV irradiation, enhanced temperature, and humidity. It was clearly demonstrated that the addition of EG to PCMs led to the suppression of PW leakage and improved the photooxidation stability of the PCMs during the aging process. The best performance was achieved by adding 15 wt% of EG to the PCMs. The sample shows a leakage of paraffin wax below 10%, retaining a melting enthalpy of PW within PCMs of 54.8 J/g, a thermal conductivity of 1.64 W/mK and the lowest photooxidation, characterized by an increase in the concentration of carbonyl groups from all investigated materials after artificial aging. Furthermore, PCMs mixed with EG exhibited good mechanical properties, even after 100 days of exposure to artificial aging. Finally, this work demonstrates a justification for the use of recycled plastics in the formation of PCMs.
Highlights
According to the World Business Council for Sustainable Development, the energy consumption of buildings accounts for approximately 40% of the entire global energy consumed [1]
Waste high-density polyethylene (HDPE) with a melting point of approximately 130 ◦ C was supplied in granular form from the Doha Plastic Products & Recycling Co. (Mesaieed Industrial, Doha, Qatar)
Expanded graphite (EG) with an average particle size of 200 μm was obtained from SGL
Summary
According to the World Business Council for Sustainable Development, the energy consumption of buildings accounts for approximately 40% of the entire global energy consumed [1]. The Sun is the most common source of energy that can be utilized to cover the energetic requirements of buildings. To utilize this energy, various components and materials have been designed and applied in the bioclimatic building concept. Various components and materials have been designed and applied in the bioclimatic building concept These new elements, which can be used for effective absorption and release of thermal energy, contribute to the consumption of electrical energy for heating or cooling. One category of materials suitable for this purpose is phase change materials (PCMs). They can be characterized as materials that undergo phase transition (from a solid to a liquid and vice versa) at Molecules 2019, 24, 1217; doi:10.3390/molecules24071217 www.mdpi.com/journal/molecules
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