Paraffin/polyacrylonitrile hybrid nanofibers for thermal hysteresis enhancement of paraffin actuators

Abstract

Fast and facile one-step preparation of paraffin/polyacrylonitrile hybrid nanofibers via single needle (uniaxial) electrospinning system was studied. As-spun paraffin/polyacrylonitrile nanofibers were used for thermal hysteresis enhancement of paraffin actuators. Solid paraffin with the melting point of 32, 58, 89 and 114°C were employed for the preparation of the paraffin/polyacrylonitrile nanofibers. Differential scanning calorimetry measurements revealed that the melting point of the paraffin in paraffin/polyacrylonitrile hybrid nanofiber was clearly detectable and the melting entalpy coming from the paraffin part gradually increased from 9.6 to 101.5 J/g with the increase in the melting points of the added same amount of paraffins in paraffin/polyacrylonitrile nanofibers. When both calorimetric and weight loss measurements were considered, the paraffin which has the melting point of 32°C was found to be suitable to produce hybrid nanofibers paraffin actuator. Therefore, this hybrid nanofiber was selected for the application in paraffin actuators for e-vehicle battery cooling systems where the battery temperature must be kept between 15 and 35°C. Paraffin compound of the paraffin actuators was prepared with a mixture of pure paraffin and paraffin/polyacrylonitrile nanofiber with the wt.% of 2.5, 5, 7.5 and 10. In the hysteresis measurements, the hysteresis value at 3 mm stroke was successfully enhanced as 1.7, 3.4, 11.9 and 15.3% sequentially for the samples produced with the above ratios. Beyond hysteresis enhancement, the phenomena of thermal percolation threshold effect and thermal conductivity contrast ratio effect in nano scale were emprically exposed on opening and closing behavior of the paraffin actuator.