Study On Structure Regulation And Electrocaloric Effect Of Polyamide Composites

Due to environmental pollution and human development needs,the disadvantages of the existing refrigeration technology are gradually emerging,and the green and sustainable refrigeration technology has become more important.The complexation of polyamide and metal salt is utilized to induce the crystallization-amorphous state transition through the change of complexation-decomplexation under an applied electric field.In this process,the great entropy change of the material is stimulated,and the electrocaloric effect can be realized by effectively utilizing the energy change of the material.In this paper,on the basis of metal salt/polyamide complex,by adding two-dimensional materials into the system,the interfacial effect and barrier effect of nanosheet are used to shorten the migration distance of ions.After removing the electric field,ions can recover the complexation state with amide groups more quickly.At the same time,two-dimensional materials can also play the role of heterogeneous nucleation and accelerate the crystallization of polyamide,reduce the response time of electrocaloric effect and enhance the electrocaloric effect.OMMT/CaCl₂/PA6 composite was prepared by film-casting method and OMMT was successfully exfoliated by PA6.After applying an electric field,N-H,C=O and C-N characteristic peaks of OMMT/CaCl₂/PA6 film appeared different degree of redshift or blueshift,showing that the electric field can drive ion migration,change the complexation of Ca²⁺and amide groups.The XRD crystal diffraction peaks of the thin film changed under the applied electric field,indicating that the complexation-decomplexation of PA6 and CaCl₂ driven by the electric field made the crystallization-amorphous state transition of the material.The temperature change showed that the material can make electrocaloric effect of about 1.5 K,and the response time of electrocaloric effect was shortened to about 5 min due to the addition of OMMT nanosheet.The 5 wt.%OMMT/PA6 nanocomposites were prepared by ultrasound-assisted method,and the optimal ultrasonic time was 20 min.On this basis,5 wt.%OMMT?20?/CaCl₂/PA6 thin film was prepared.FTIR showed that the relevant characteristic peaks appeared greater shift,indicating better reversibility,circularity and complexation-decomplexation of transition.POM showed that film had obvious electrocrystallization.Due to the poor thermal conductivity of OMMT nanosheet,when the OMMT content increased,the heat conduction efficiency decreased in the system,and the accumulated heat inside the material made the electrocaloric effect become smaller.The test showed that temperature change of the film was about 1.0 K under an electric field,and the response time was about 2 min.Few layer MoS₂ nanosheet was separated by liquid-phase exfoliation method,and then MoS2/CaCl2/PA6 composites were prepared.FTIR showed the migration and recovery of characteristic peaks corresponding to complexation-decomplexation of PA6 and CaCl₂.The changes of crystallization peak and amorphous peak of PA6 were also revealed by FTIR.POM showed that the material exhibited obvious change of particle size,indicating that the material had crystallization-amorphous state transition under an applied electric field.The thermal imager test showed that thin film had a temperature change of electrocaloric effect of about 1.4 K,and the response time was about 2 min,indicating that the better thermal conductivity of MoS₂ nanosheet was conducive to improve the electrocaloric effect.