Preparation And Properties Of Shape Memory Benzoxazine/Epoxy

Epoxy resins have been widely studied and applied due to their low manufacturing cost,great insulating properties,and good thermal conductivity.However,the highly cross-linked structure after curing makes them exhibit certain brittleness,and due to the development of smart materials and the increasing awareness of environmental protection,higher requirements are placed on epoxy resins.Benzoxazine（BOZ）has remarkable properties such as good molecular structure design,almost zero volume shrinkage during curing,excellent mechanical properties and high thermal stability.Epoxy resin and BOZ can form a uniform three-dimensional cross-linked structure during the curing process,improving the mechanical properties of the system in the cured state.At the same time,materials containing imine bonds can exhibit excellent shape memory properties.For this purpose,in this paper,4,4’-dicyclooxy diphenylimine（DEI）containing imine bond was blended with benzoxazine resin to obtain DEI/BOZ copolymer with shape memory property.Secondly,DEI/BOZ/E-51（DBE）and DEI/BOZ/HER（DBH）systems were prepared by blending two different epoxy resins E-51 and Hydantoin epoxy resin（HER）,which can provide some practical significance for the development of electronic packaging materials with excellent mechanical properties and long-term use under high temperature conditions.The main studies are as follows.（1）A novel DEI/BOZ copolymer network was prepared without any curing agent and catalyst,and its curing behavior,thermal weight loss and shape memory properties were investigated.The residual carbon rate of DEI/BOZ copolymer at 700°C is 50%,indicating a good thermal stability.Also,the presence of imine bonds in DEI gives the material a potential shape memory capability.（2）The curing reactions of DBE and DBH systems were investigated by differential scanning calorimetry;calculations the activation energy required for the reaction of the DBE system was higher than that of the DBH system.The effect of DEI content on the gel time and viscosity properties of DBE and DBH systems was investigated,and it was found that the addition of DEI would accelerate the reaction process,shorten the gel time and increase the resin viscosity.（3）The temperature of DBE and DBH systems did not decrease and increased at T_5%,T_20%and T_p,indicating that the addition of DEI made the thermal decomposition performance of the materials improve,with DBE2.5 showing excellent thermal stability.The dynamic thermo-mechanical properties study showed that when the DEI content was 10 wt%,the T_g of DBE system reached the maximum value of 203°C;while the T_g of DBH system reached the maximum value of 171.5°C,indicating that the heat resistance of DBE system was better.（4）The mechanical properties showed that DBE7.5 and DBH7.5 had the best mechanical properties as the DEI content increased.The DBE7.5 bending strength（modulus）was 139.49MPa（3.05 GPa）,tensile strength（modulus）was 79.94 MPa（1.92 GPa）,and impact strength was 18.76 k J/m².The DBH7.5 had a bending strength（modulus）of 99.71 MPa（2.82 GPa）,a tensile strength（modulus）of 53.5 MPa（1.05 GPa）,and an impact strength of 18.69 k J/m².The results of shape memory test showed that the shape recovery time was accelerated with the increase of DEI content.In addition,the higher the temperature,the shorter the time taken for shape recovery.