This article studied the dripping behavior of eight polymers under UL94 vertical test conditions. The results suggested two different dripping behaviors: Type I, dripping with uniform- and small-sized drops with the short first dripping time, and Type II, dripping with irregular- and large-sized drops with the long first dripping time. Polymers of Type I dripping had dominant decomposition mechanism of random-chain scission, low activation energy of viscous flow, and high ratio of effective heat of combustion to heat of gasification. Otherwise, Type II dripping dominates. The surface tension at ambient temperature and the melt flow index at processing temperatures were not as important to dripping as expected. It was found that talc could convert the dripping of low-density polyethylene from Type I to Type II at a critical talc loading level of 20 wt%, which was ascribed to the reduction in the burning rate and the formation of an integral residue. Finally, a generalized model was presented, and a derived correlation showed that the drop mass was a power law function of the dripping time.

No abstract

Phase change material (PCM) is able to melt and crystalize with a high heat of phase change at constant temperature, which provides new and green cooling and heating strategies for buildings. In this work, PCMs for buildings composed of acrylonitrile‐styrene‐acrylate copolymer (ASA), polystyrene‐b‐poly(ethylene/butylene)‐b‐polystyrene triblock copolymer (SEBS) and paraffin were fabricated by melt blending. The results of the accelerated leakage test indicated an excellent ability of PCMs to keep paraffin from leakage. Thermal properties suggested that the phase change enthalpy of PCMs increased with the increasing content of paraffin and their phase change temperature was close to the comfortable sensible temperature of human body, which made it quite suitable for building cooling and heating. Besides, PCMs presented excellent stability and reusability after several thermal cycling tests. The temperature test conducted with self‐designed cylindrical devices gave a more sufficient and direct demonstration of the cooling and heating effect. Remarkably, excellent cooling and heating performance (both as high as 15°C) of the composites could be obtained with the addition of paraffin. And the time span of the cooling and heating process was as long as 5 and 7.5 hours, respectively. Owing to its excellent cooling and heating capabilities, the ASA/SEBS/paraffin composites are of great potential to be applied in building temperature control.

Mine road dust is an important source of dust in mine operations. The dust produced on the road surface is a great hazard to the workers. Aiming at the road dust of an open-pit mine, this paper conducts physical and chemical analysis of a dust suppressant prepared by using sodium polyacrylate as a binder, sodium carbonate as a moisture absorbent, polyethylene glycol as a water-retaining agent, and alkyl glycoside as a surfactant. Characterization of characteristics and dust suppression performance. The results show that the dust suppressant has a pH of 11.03, a viscosity of 18.5 mPa•s, and a surface tension of 28.1 mN/m. The content of heavy metal ions contained is less than the maximum concentration de ned by the national standard. Under the same temperature condition, the greater the humidity, the stronger the hygroscopicity, especially when the humidity is 30%, where the better hygroscopic effect than water is obvious. The dust suppressant also has good anti-evaporation properties and it keeps at 4-5% moisture content after 10 days at a normal temperature. Compared with water, the dust suppressant has better resistance to wind erosion and compression. Under the same conditions, the loss rate of water is 2 times that of the dust suppressant and the pressure of the dust suppressant sample is about 3 times that of water. The dust suppressant has a much higher dust removal e ciency for all dust and respirable dust than water under the same conditions. Finally, the test results and mechanism of the dust suppression effect of the dust suppressant are described and analyzed, which shows that the dust suppressant studied in this paper has good performance and is suitable for road dust prevention.