Paraffin/polyvinyl alcohol/MXene flexible phase change composite films for thermal management applications

• Paraffin/polyvinyl alcohol/MXene flexible phase change composite films with cross-linking structure were prepared. • Mechanical strength, light-to-heat conversion and heat transfer were simultaneously enhanced while available latent heat. • Temperature-controlled effect was obvious based on simulated thermal management test. How to construct light absorption−photothermal conversion−heat storage−heat utilization integrated flexible phase change composite films (FPCCFs) with synergistically enhanced properties toward thermal management applications remains a challenge. In this work, the paraffin/polyvinyl alcohol/MXene (PPM) FPCCFs with cross-linking structure were prepared by a simple physical blending method, and the MXene played a key and important role in simultaneously enhancing their mechanical strength, light-to-heat conversion efficiency and thermal conductivity while maintaining available latent heat. The increasing paraffin loadings increased latent heat (∼ 117.02 J/g) but decreased tensile strength (∼ 1.01 MPa) of PPM FPCCFs. However, the MXene slightly reduced latent heat (> 92.72 J/g) while enhancing tensile strength (∼ 2.51 MPa) of PPM FPCCFs. The improved flexibility was mainly attributed to the MXene nanosheets with abundant surface functional groups providing additional hydrogen bond binding sites so that the cross-linking was promoted. Meanwhile, the light-to-heat conversion ability and heat transfer rate of PPM FPCCFs were effectively improved by the MXene, which was further confirmed by the surface temperature distribution results. Furtherly, the PPM FPCCFs showed repeatable light-to-heat conversion stability, excellent light-driven shape recoverability (nearly 100%), good chemical compatibility, crystallization property and acceptable thermal stability as well as thermal reliability that required further improvement. Based on the simulated thermal management test, the PPM FPCCFs showed obvious temperature-controlled effect, showing potential application prospect.