Heat Storage Performance Of Polyethylene Glycol Composite Phase Change Materials Based On Polyaniline Nanofibers

The development of new energy storage technologies can effectively deal with environmental pollution and global warming problems caused by the massive use of fossil fuels.The rapid development of thermal energy storage technology provides a novel approach for improving energy efficiency and solving energy crisis and pollution problems.As latent heat storage materials,phase change materials have a very high heat storage density and can absorb and release considerable latent heats in a narrow temperature range,which endows them with great application potential.But the poor thermal conductivity and leakage during a phase transition limit its application.At present,most phase change materials have been applied to the fields of latent heat storage in the form of composite phase change materials based on encapsulation technology to stabilize shape.The commercialized composite phase change materials have a low content of phase change material,poor heat storage capacity and inferior thermal conductivity.As a result,the heat storage capacity and heat storage/release rate of these composites are not satisfactory.Therefore,the exploitation of new composites towards thermal energy storage is a great significance to the development of latent heat storage.In this paper,polyethylene glycol(PEG),used as a phase change material,was supported by three types of carriers,respectively.This research mainly includes the following three aspects.Firstly,polyaniline(PANI)was selected as a carrier,and the microscopic morphology of PANI nanofibers could be controlled by changing the reaction mode(low-speed stirring or standing).And the effect of two PANI nanofibers on the PEG loading content was also studied.For the low-speed stirring reaction mode,the obtained PANI nanofibers had uniform sizes and good dispersion properties while for the static reaction mode the short rod-like PANI nanofibers were obtained and the agglomeration of PANI nanofibers was observed.Based on the short rod-like PANI nanofibers as the carriers of PEG,the phase transition enthalpy of the prepared PEG/PANI composite can reach 132.8 J/g,and the mass percentage of PEG loaded in composite was 77.43wt%,showing its excellent phase change heat storage capacity.Secondly,by combining PANI and carbon nanotubes(CNTs),PANI-CNTs composite fibers were prepared and used as carriers to prepared PEG/PANI-CNTs composite.In this paper,the nanobrush-like PANI layer was grown on the surface of CNTs through chemical oxidation of aniline polymerization.As the amount of CNTs added(CNTs: ANI = 6.7 ~ 33.5wt%)increased,the thickness of the nanobrush-like PANI layer gradually decreased.Meanwhile,with the increase of CNTs amount,the phase transition enthalpy decreased first and then increased,while the thermal conductivity increased first and then decreased.When the content of CNTs was 6.7wt%,the maximum phase change enthalpy was 123.96 J/g.And when 26.8wt% of CNTs were added,the thermal conductivity of the composite can reach up to 0.468 W/Mk,74.0% higher than that of PEG.Finally,we carbonized PANI nanofibers and PANI-CNTs composite fibers at high temperature under the argon atmosphere to study the effect of carbonation conditions on the morphology of the obtained samples.Carbon-based composite phase change materials were prepared using the carbonized samples as carriers.Compared with the PANI nanofiber carbon-based composites,the PANI-CNTs carbon-based composites have higher heat storage capacity and higher thermal conductivity,with the phase transition enthalpy of up to 124.74 J/g,the loading rate of 72.73wt% and the thermal conductivity of 0.407 W/mK.The thermal conductivity of PANI-CNTs carbon-based phase change material was increased by 28.4% compared with that before carbonization.