Preparation Of Polypyrrole Decorated Phase Change Microcapsules And Its Application In Flexible Fabrics

Energy shortage and environmental pollution have become a daunting issue as the demands and overuse of fossil fuels keeps growing.Solar energy,as renewable and clean heating source,has been widely used in various fields,such as solar water heaters and photovoltaic cells.Phase change microcapsules（micro PCMs）is considered as ideal energy storage materials with no leakage,low price,small volume and high energy storage density,which plays an important role in photothermal conversion and energy storage fields.Furthermore,micro PCMs that enables active storage of the clean and sustainable solar energy have drawn broad attention.The combination of the photothermal materials and micro PCMs can effectively convert solar energy into heat for the storage and release of micro PCMs.Owing to the special conjugated structure,polypyrrole（PPy）is a kind of efficient photothermal conversion materials with excellent UV-Vis-IR absorption covering the whole range of solar irradiation.Moreover,PPy can be controllably deposited on the surface of micro PCMs via simple surface modification which has broad application prospects in solar energy related fields and thermal energy management.In the first part of the experiment,PPy-coated micro PCMs with good dispersibility and uniformity were facilely prepared via in-situ polymerization of commercial micro PCMs（M₀）with photothermal converter PPy.When 1 wt%,2 wt%and 3 wt%pyrrole（Py）was used,the final amounts of PPy loaded on M₀ were 0.85 wt%,1.91 wt%and 2.84 wt%,respectively.The corresponding samples were specified as M₁,M₂ and M₃,respectively.The surface of micro PCMs became increasingly rugged as more granular PPy were deposited.Moreover,due to the excellent photothermal property of PPy,micro PCMs containing merely 1.91 wt%PPy exhibited high melting enthalpy（231.6 J/g）and high photothermal storage efficiency（up to 94.02%）under 1 solar irradiation.Showing that the decoration of PPy had minimum effect on the thermal stability and phase change properties of the M₀.In the second part of the experiment,M₂ was chosen for further exploration of the photothermal performance.Flexible photothermal phase change textiles were fabricated together with high-elastic polyurethane（PU）,and braided into photothermal textiles.M₂ was composited with PU at varied wt%to prepare composite PCM fibers（m%M₂/PU,m=60,70,80,90）with photothermal conversion and storage effects.All fibers displayed smooth surface and circular porous cross-sections;PU acted as the connective tissue of the composites that binds the embedded micro PCMs.With increasing M₂ content,the fiber cross-section appeared more densely packed with micro PCMs,while the surface became increasingly coarse with small voids.The composite photothermal textile containing 80 wt%micro PCMs showed good elasticity（365%elongation）for fiber,high melting enthalpy（182.7 J/g）and excellent photothermal storage efficiency（up to 93.14%under 1 solar irradiation）,and excellent cycling stability.Furthermore,the composite textile was fixed on the chest of the doll and heated from ambient temperature（25.9°C）to 74.0°C by 1 k W/m² light irradiation for 15 min,which can maintain 40.1°C and 32.3°C after removing the light for 5 min and 25 min,respectively,indicating the promising applications of using it in thermotherapy to effectively relieve pain.The procedure described herein is simple and easily scalable,thus showing great promise for fabricating photothermal storage composites for solar energy related applications.