The Preparation Of Electrocrystalline Polyamide As Novel Electrocaloric Material And The Study Of Its Electrocaloric Effect

The reversible temperature change of electrocaloric materials was achieved by modulating dipole upon the application and removal of the electric field.Thereby,the electrocaloric materials can be used to develop solid-state cooling devices for miniaturized electronic components.This new refrigeration technology has the advantages of microminiature,high efficiency and environmentally friendly.Polymer-based electrocaloric materials have a relatively high electrocaloric effect upon the application of high electric field.However,the low electrocaloric strength and small cooling capacity of polymer-based electrocaloric materials still remains a practical disadvantage.In our paper,we exploit a novel electrocaloric materials based on the entropy change from the aggregation structure transition of polyamide.We discuss the complex-decomplexation of polyamide and electrocaloric effect upon the application and removal of the electric field in detail as follows.Amorphous polyamide 66（PA66）/calcium chloride（CaCl₂）complexed films were prepared via solvent-cast by using CaCl₂ as complexing agent,and crystallographic PA66 was changed into amorphous state.Besides,crystallized PA66 could be reformed through decomplexation in ethanol,deionized water and 2-chlorohydrin.Thus,the aggregation structure transition of PA66 can be artificially controlled.On the basis of this mechanism We design a novel electrocaloric effect refrigeration technology toobtain maximum theoretical isotherm entropy change and adiabatic temperature change of 653.4 J kg^-1 K^-1 and 162.3 K,respectively.Amorphous PA66/CaCl₂ complexed films were prepared by melt-hot pressing.When the CaCl₂ content reaches 5 vol%,PA66 were completely transformed into amorphous state.Ca²⁺can complex with both the N and O elements in the amide bond of PA66,and destroy the hydrogen bonding between the chains.Ca²⁺were migrated to the cathode and exhibited a gradient distribution upon the application of 0.4 kV cm^-1electric field.As the complexation structrue between Ca²⁺and amide groups was destroyed,the hydrogen bond structure was reformed between the amide groups.Ca²⁺were migrated back upon the removal of the electric field,and the complexation structrue between Ca²⁺and amide groups was reformed.In this process,the electrocaloric effect of PA66/CaCl₂ complexed film is about 1 K,and the electrocaloric strength is 2.5 K cm kV^-1.PA66/CaCl₂ gels were prepared by adjusting the ratio of PA66,CaCl₂ and 2-chlorohydrin.The electrocaloric effect of 5%PA66/CaCl₂ gel is about 1.3 K,and the electrocaloric strength is 3.25 K cm kV^-1 upon the application of 0.4 kV cm^-1 electric field.In the range of 0⁰.4 kV cm^-1,the electrocaloric effect of gel increases with the increase of the electric field.In the range of 3⁷ vol%Ca²⁺content,the electrocaloric effect of gel increases first and then decreases upon the application of 0.4 kV cm^-1electric field.The introduction of OMMT lamellar material into the gel can effectively shorten the response time of the electrocaloric effect.