In this article, a flame retardant microcapsule ammonium polyphosphate microencapsulated by polyurea (POAPP) was successfully synthesized by interfacial polymerization method using ammonium polyphosphate (APP) as core and polyurea as shell. The microencapsulation is observed by scanning electron microscopy and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and hydroscopicity test, which prove the success in synthesizing microencapsulation. When the POAPP is added into rigid polyurethane foam (RPUF), the flame retardant and mechanical properties are investigated using cone calorimeter, limited oxygen index test, and compressive strength test. The PHRR of RPUF‐POAPP20 decreased from 336.52 kW/m2 (Ref. RPUF) to 203.84 kW/m2 and the THR of RPUF‐POAPP20 was only 7.6 MJ/m2, which is 33.9% lower than that of Ref. RPUF. Furthermore, the limiting oxygen index of RPUF‐POAPP20 reaches 24.8%, which increased by 36.3% compared to Ref. RPUF. Whereas the maximum compressive strength of RPUF‐POAPP5 was 7.46 MPa, which is higher than that of RPUF‐APP5.
Triboelectric
nanogenerator (TENG) has the great potential to harvest
the electrostatic energy and mechanical energy of raindrops. However,
raindrops are small and scattered, and it is difficult to harvest
their mechanical energy effectively. In this paper, a gridding triboelectric
nanogenerator (G-TENG) with an area of 81 cm2 is designed
and developed to effectively harvest the mechanical energy of raindrops
on a large scale. Its peak output power density is 8.56 mW/m2, which is 245 times the value of 35 μW/m2 of a
general TENG without gridding. Each unit of the G-TENG can work independently,
which can effectively decrease the mutual counteraction of elastic
deformation among the adjacent positions of the raindrop impacting
layer and avoid the accumulation of raindrops. Under the impact of
simulated raindrops from a shower at a flow rate of 0.137 mL/(cm2·s), the open-circuit voltage (V
oc) and the short-circuit current density (J
sc) of the G-TENG reach 400 V and 2.5 mA/m2, respectively. The peak output power density reaches 110 mW/m2, which is 42 times the reported maximum value of 2.6 mW/m2 of raindrop energy harvesting TENGs with the size larger
than 10 cm2. Moreover, the G-TENG can harvest the mechanical
energy of raindrops at a wide range of raindrop flow rates from 0.055
to 0.219 mL/(cm2·s). This work contributes to the
raindrop mechanical energy harvesting on a large scale.
Due to the energy crisis and environmental pollution, the research on energy‐efficient building has increasingly attracted attention. The phase change materials (PCMs) play a vital role in increasing the energy utilization efficiency. In order to protect the PCMs from leakage during phase change process, the melamine sponge (MS) and modified melamine sponge (MMS) are considered as the frameworks. The leakage rate of MS and MMS sample were compared. The thermal and fire behavior was investigated by small room model, infrared thermal imager and cone calorimeter. The results show that the leakage rate of MS is much higher than that of MMS. On the condition of the same percentage of PCMs, MMS sample has better temperature control performance. The MS sample releases heat much faster and more than MMS sample. While MMS plays a role in inhibiting ignition.
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