Plastic composite of bamboo charcoal stabilized polyethylene glycol with thermal energy storage and temperature regulation for building energy efficiency

Phase change materials (PCMs) are often used as building materials to reduce the energy consumption. However, conventional PCMs are susceptible to leakage and have a short service life. To solve this problem, thermal energy storage (TES) composites were fabricated by using bamboo charcoal (BC) encapsulating polyethylene glycol (PEG) as the PCM and low density polyethylene (LDPE) as the matrix. The shape and structure of BC and BC-plastic composites were examined using scanning electron microscopy, X-ray diffractometry, and mercury intrusion porosimetry. Differential scanning calorimetry, thermogravimetry (TG), and infrared thermography were used to characterize the manufactured TES composites. Physical and mechanical strength assessments were also conducted. The results demonstrated that: (1) BC possessed a rich void structure with a porosity of 61.4%, which could be used to adsorb PEG and the composites was a combination of PEG, BC, and LDPE with no chemical reaction; (2) thermal tests demonstrated that the composites exhibited favorable temperature regulation properties, featuring a maximum latent heat capacity of 29.1 J/g along with suitable phase change temperatures, yet thermal durability needs to be improved much further, addition of PEG reduced thermal conductivity of the composite from 0.38 to 0.34 W/mK; (3) the addition of PEG was beneficial for the impact strength but had a negative impact on the flexural and tensile properties; and (4) due to their satisfactory thermal performance and acceptable mechanical properties, these TES composites can be effectively utilized as building materials for temperature control purposes.Highlights Bamboo charcoal (BC) had a large number of pores that can encapsulate polyethylene glycol (PEG). PEG/BC performed satisfactory latent heat. Low density polyethylene was used as the matrix to realize the second encapsulation of phase change material. Thermal energy storage composites had excellent stability and good heat storage capacity. PEG incorporation negatively affected flexural and tensile properties.