RESUMEN
Phase change material (PCM) has been widely studied for efficient thermal management. This work is the first holistic experimental research on the temperature control performance of PCM-integrated firefighters' gloves. The results showed that the thermal protection time could be extended by 2-5 times in the direct contact to hot object tests and around 1.5 times under the radiant/convective heat source tests when embedding a 1-mm-thick PCM layer in gloves. The PCM of melting point 68°C showed the best thermal protection performance in all test conditions since it had the most efficient phase change function during the heating process. Considering the PCM location effect, the PCM with lower melting point (68°C) showed better performance when located close to external environment (heat source) and the PCM with higher melting point (108°C and 151°C) showed better performance when located close to hand. The optimum PCM thickness would be in the range of 0.5-1.0 mm for both thermal protection improvement and hand dexterity purposes. In addition, the time for continuous temperature rises on the hand surface at post-heat exposure was longer when embedding PCM in firefighters' gloves due to the stored latent heat in PCM.
RESUMEN
Firefighter injures caused by burns and thermal stress occupies around 5%-10% of the total injuries annually. Glove is the thinnest/weakest components among the firefighter turnout gear, which can put firefighters, are at risk of severe wrist and hand burns during fire calls. Burns can occur quickly and enhancing the thermal protective performance of firefighters' gloves will prevent these burns. One-dimensional (1D) heat transfer modeling and simulations were performed through the COMSOL Multiphysics software to investigate the improvement of thermal protective performance when integrating a Phase Change Material (PCM) layer into a conventional structural firefighting glove. Parametric studies were conducted to explore the effects of PCM thermal properties, layer thickness, and location in glove structure on hand protection. It was found that a PCM with a higher density, specific heat, and latent heat of fusion had a larger heat capacity and thermal inertia, resulting in better thermal protective performance. The optimum melting point of PCM was found to be in the range of 80°C-140°C. A PCM layer with a thickness of 0.5 mm-1.0 mm showed sufficient thermal protection. The location of the PCM layer should be close to the inner glove surface for high-heat situations. Overall, modeling suggests that the addition of a PCM layer could significantly enhance the thermal protective performance of firefighters' gloves, with results showing increased time (2-4 times as long) for skin to reach second-degree burn temperature when compared to the conventional glove without PCM.
RESUMEN
Biopolymer foams manufactured using CO2 enables a novel intersection for economic, environmental, and ecological impact but limited CO2 solubility remains a challenge. PHBV has low solubility in CO2 while PCL has high CO2 solubility. In this paper, PCL is used to blend into PBHV. Both unfoamed and foamed blends are examined. Foaming the binary blends at two depressurization stages with subcritical CO2 as the blowing agent, produced open-cell and closed-cell foams with varying cellular architecture at different PHBV concentrations. Differential Scanning Calorimetry results showed that PHBV had some solubility in PCL and foams developed a PCL rich, PHBV rich and mixed phase. Scanning Electron Microscopy and pcynometry established cell size and density which reflected benefits of PCL presence. Acoustic performance showed limited benefits from foaming but mechanical performance of foams showed a significant impact from PHBV presence in PCL. Thermal performance reflected that foams were affected by the blend thermal conductivity, but the impact was significantly higher in the foams than in the unfoamed blends. The results provide a pathway to multifunctional performance in foams of high performance biopolymers such as PBHV through harnessing the CO2 miscibility of PCL.
RESUMEN
Ecological, health and environmental concerns are driving the need for bio-resourced foams for the building industry. In this paper, we examine foams made from polylactic acid (PLA) and micro cellulose fibrils (MCF). To ensure no volatile organic compounds in the foam, supercritical CO2 (sc-CO2) physical foaming of melt mixed systems was conducted. Mechanical and thermal conductivity properties were determined and applied to a net zero energy model house. The results showed that MCF had a concentration dependent impact on the foams. First structurally, the presence of MCF led to an initial increase followed by a decrease of open porosity, higher bulk density, lower expansion ratios and cell size. Differential Scanning Calorimetry and Scanning Electron Microscopy revealed that MCF decreased the glass transition of PLA allowing for a decrease in cell wall thickness when MCF was added. The mechanical performance initially increased with MCF and then decreased. This trend was mimicked by thermal insulation which initially improved. Biodegradation tests showed that the presence of cellulose in PLA improved the compostability of the foams. A maximum comparative mineralization of 95% was obtained for the PLA foam with 3 wt.% MCF when expressed as a fractional percentage of the pure cellulose reference. Energy simulations run on a model house showed that relative to an insulation of polyurethane, the bio-resourced foams led to no more than a 12% increase in heating and cooling. The energy efficiency of the foams was best at low MCF fractions.