| Epoxy resin (EP), for their outstanding advantages on strength, modulus, bonding and technique as advanced resin matrix have been widely used in high science and technique fields, such as aviation, spaceflight, etc. However, EP used as high performance flying instrument structural composite matrixes are confined because of the cured resins having not enough toughness. The modifying work about these thermoset resins has been very active. The methods of toughening EP are reviewed, and the toughening mechanism is summarized. On the basis of the previous work, it is point out liquid crystalline epoxy in-situ composite toughens EP to enhance their toughness.The route of toughening EP domestic and overseas at present is mainly rubber, thermoplastic, chain-extending and thermotropic crystalline polymer toughening. These methods have themselves disadvantages in varying degrees. For its structural distinguishing feature, liquid crystalline epoxy can in-situ self-reinforce to improve cured resin toughness during the cross-reaction of forming network with cure agent. At the same time, liquid crystalline epoxy is compatible with EP. Liquid crystalline epoxy links EP with strong chemical bond by ammoniac cure agent chain-extending. Moreover, the addition of liquid crystalline epoxy with low molecule weight can't lead to poor processability problem. Therefore, it is a new and worthy of studying route that liquid crystalline epoxy toughens and modifies EP.SCEP is synthesized by the reaction of 4-Hydroxydiphenyl with epoxy chloropropane and catalyzed by NaOH, and then a novel liquid crystalline epoxides. And then LCEP is synthesized by CYD-128, a modifier, and SCEP. The effect of synthesis technique and extraction way on yield has been discussed. The structure and phase behaviour of the synthesized LCEP have been characterized by Differentia Scanning Calorimetry (DSC), Polarized Optical Microscopy (POM), Flourier Transmit Infrared (FTIR), etc. The results indicate that LCEP shows nematic phase during cooling process between 200℃. The curing agents which are chosen in the experiment are 4, 4' — diaminodiphenylmethane (DDM) . The curing reaction characteristic, heat and mechanic properties of cured resin have been studied. The curing network of LCEP/DDM is comprised of oriental order mesogenic domain and isotropy domain observed by SEM, POM.The microstructure and curing properties of the LCEP toughening EP system are studied. The systems are LCEP/CYD—128/DDM, CYD—128/DDM. The toughness of CYD—128 resin system can be increased remarkably by adding LCEP. The impactstrength and glass transition temperature of cured LCEP/CYD—128/DDM system are 26.5KJ/m2 and 150"C, respectively when the content of LCEP is 50wt%. The system of LCEP/CYD-128/DDM is a partial compatible system while during curing the LCEP phase be separated. The ordered structure of LCEP can be kept up in the cured network in the copolymerization system of LCEP/CYD —128/DDM, that is the formed oriental ordered mesogenic domain in the cured network can initiate, branch, terminate the crack dispersed in the continuous epoxy matrix and hence make the toughened resin system have good dynamic property and outstanding heat resistance. The theory of combining silver-crack shearing-zone with bridge-link anchor is proposed by analyzing the broken section of LCEP toughening CYD—128 resin system. And used PEEK as a filling, studied for the useage of fillings' affection can bring to the forming of nematic phase in curing processing.
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