The Study On The Structural Evolution And Cooling Effect Of Long Carbon Chain Nylon Complexes Under Electric Field

The electrocaloric effect?ECE?is a physical phenomenon of reversible isothermal entropy change or adiabatic temperature change occurring in a polar material under the action of an electric field.A material having an electrocaloric effect is called an electrocaloric material.Due to its light weight,environmental protection and high efficiency,the electrocaloric effect refrigeration has excellent development prospects.In this paper,the mechanism of the structure change of the nylon/metal salt complex under the action of electric field can be studied.The complex mechanism of long carbon chain nylon?nylon 11 and nylon 12?with CaCl₂ is studied in detail.Aggregate structure transition of PA11/CaCl2 and PA12/CaCl2 complexes and temperature change caused by entropy change during structural transformation.The main research results are as follows:?1?A complex of PA11/CaCl₂ and PA12/CaCl₂ was produced by solution blending.When the content of CaCl₂ reaches 5 vol%and 6 vol%,respectively,PA11 and PA12can be converted into an amorphous state;the interaction between Ca²⁺and amide groups can destroy the intermolecular hydrogen bonding between PA11 and PA12;the polarizing microscope further visually demonstrates the effect of added CaCl₂ on the crystallization of PA11 and PA12.?2?The action of the electric field is used to promote the migration of ions,and the complex structure of PA11/CaCl₂ and PA12/CaCl₂ complexes is transformed.The XRD and FTIR tests show that the complex of PA11/CaCl2 and PA12/CaCl2 undergoes an amorphous-crystalline transition under the action of an electric field,and returns to the complex state after the electric field is removed.The polarizing microscope visually shows the change in the crystallization of the nylon complex before and after the electric field.Ca²⁺moves under the action of electric field?presenting a gradient distribution?,the complexation of Ca²⁺with the amide group is destroyed,the hydrogen bond is regenerated between the amide groups,the crystallinity of the complex is improved,and the Ca²⁺is removed after the electric field is removed.Hydrogen bonding between the amide groups,Ca²⁺and amide groups recombine,reducing the crystallinity of the complex.?3?The entropy change in the structural transformation of PA11/CaCl₂ and PA12/CaCl₂ complexes under electric field is theoretically calculated,and the temperature changes under the maximum adiabatic conditions are 109 K and 86.7 K,respectively.The entropy changes under the maximum isothermal conditions were734.5 J kg^-1 K^-1 and 597.9 J kg^-1 K^-1,respectively.The actual temperature change test of PA11/CaCl2 and PA12/CaCl2 complex films is carried out under the electric field of0.5 kV cm^-1,and the temperature changes of 1 K and 0.8 K are obtained respectively.The intensity of the electrocaloric effect is 2 K cm kV^-1 and 1.6 K cm kV^-1 respectively.The cyclic repeatability of the PA11/CaCl2 and PA12/CaCl2 complex films is tested and it is found that the cooling effect is attenuated.Adding a small amount of nucleating agent SiO2 to PA11/CaCl2 promotes the temperature change of nylon complex under electric field.Encapsulation of PA11/CaCl₂ using PDMS can effectively avoid the decomplexation of the nylon complex film by factors such as water vapor.