| With the rapid popularization of smart electronic devices in various industries,high power and high integration have become an important direction for the development of electronic devices,and heat dissipation has become an obstacle that limits the rapid development of devices.Because of the unique advantages of light weight,easy processing,and low cost,polymer materials are widely used in electronic equipment,but the thermal conductivity of the polymer itself is as low as 0.2 W·m-1·K-1,therefore,a variety of high Nanomaterials with thermal conductivity,such as graphite,carbon nanotubes,boron nitride,graphene,etc.,have been incorporated into polymers in order to improve the thermal conductivity of composite materials.Among them,carbon fiber(CF)has also been increasingly popular due to its excellent axial thermal conductivity.The more researchers pay attention.This topic is based on the research of the composite of carbon fiber and polymer to prepare light-weight,high-strength,high thermal conductivity composite materials:an ionic liquid 1-aminopropyl-3-methylimidazolium bromide(IL)was synthesized and non-covalently modified by the ionic liquid Modified the surface of carbon fiber,and studied the double non-covalent cation-?and hydrogen bond of ionic liquid modified carbon fiber(IL@CF)in bio-based nylon 56(PA56)and epoxy resin(EP).And study its influence on the thermal conductivity and mechanical properties of IL@CF/PA56 and IL@CF/EP composites and the mechanism of action.The specific research content is as follows:(1)The ionic liquid[APMIm]Br modified carbon fiber(IL@CF)/PA56 composite was prepared by the melt blending/hot pressing method.After the non-covalent modification of carbon fiber,the dual role of cation-?and hydrogen bond is constructed in the composite material system.This non-contact chemical force close to the covalent bond strength significantly improves the dispersibility of CF,while effectively reducing the carbon fiber and The thermal resistance of the interface between the PA56 matrix helps to form a heat transfer channel between the polymer matrix and the thermally conductive filler,which not only significantly improves the thermal conductivity in the horizontal direction,but also greatly improves the thermal conductivity in the vertical direction.When filled with 25 wt%unmodified CF,the vertical and horizontal thermal conductivity of CF/PA56 are 0.747 and 1.974 W·m-1·K-1,respectively,1.5 times and3.96 times that of pure PA56.When filled with 25wt%IL@CF,the thermal conductivity of IL@CF/PA56 in the vertical and horizontal directions is increased to 1.287 W·m-1·K-1 and 2.474 W·m-1·K-1,which are pure The thermal conductivity of PA56 is 2.58times and 4.97 times.Polarization microscope and DSC analysis show that adding a certain amount of carbon fiber can act as a heterogeneous nucleating agent,the grain size decreases,the crystallization temperature increases significantly,and the crystallization and melting enthalpy increase.The addition of ionic liquid modified carbon fiber narrows the crystallization peak and melting peak of the composite material,and the crystallization becomes more perfect.The tensile test results show that the hydrogen bond and cation-?interaction formed between the modified carbon fiber and PA56 can effectively enhance the interfacial bonding force between the filler and the matrix.When the filling amount is 25 wt%,the tensile strength of IL@CF/PA56,Elongation at break and modulus of elasticity are greatly improved.(2)The ionic liquid[APMIm]Br modified carbon fiber is prepared by the ice template method to obtain an orderly oriented porous carbon fiber skeleton(O-CF),and the modified carbon fiber/epoxy resin composite material is prepared by casting epoxy resin(O-IL@CF/EP).The oriented carbon fiber skeleton constructs an ordered thermal conductivity network in the epoxy resin matrix,and the cation-?non-covalent interaction of the modified carbon fiber surface and the hydrogen bond between the carbon fiber and the epoxy resin can effectively reduce the interface thermal resistance and improve the interface bonding It brings excellent thermal conductivity and mechanical properties to epoxy composite materials.The density of the carbon fiber skeleton is adjusted by the volume fraction of carbon fiber.When the O-IL@CF filling amount is 22.3 vol%,the in-plane thermal conductivity of the O-IL@CF/EP composite material can reach up to 7.98 W·m-1·K-1.The tensile test results show that the O-IL@CF/EP composite material has excellent mechanical properties due to the dual non-covalent synergy,and its tensile strength reaches 40.62 MPa,which is higher than the O-CF/EP composite material in the same filler volume fraction 30.7%.The specific strength is 29.6 Nm/kg,which is 168%higher than pure epoxy resin.At the same time,the elongation at break and elastic modulus of O-IL@CF/EP composites are also significantly higher than that of O-CF/EP composites.Based on the high specific strength of carbon fiber,this subject builds a cationic-?non-covalent force on the surface of the carbon fiber and a hydrogen bond force with the matrix.Then,according to the processing characteristics of the matrix itself,light weight is prepared through different processing methods.High-strength carbon fiber thermally conductive composite material provides a new idea for surface modification of carbon fiber,and also provides a practical method for preparing high thermally conductive carbon fiber composite material. |
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