Study On Epoxy Resin Modifed With Silicone And Sblicone-containing Copolymers

Epoxy resins are the most important thermosetting polymers, which widely used as matrices in coatings, adhesives, electrical insulators, reinforced composites and astronautics industries due to their excellent properties, such as good adhesion to various substrates, high tensile strength and modulus, good chemical and corrosion resistance, high heat distortion temperature, good environmental stabilities, low shrinkage on curing and easy processibility.However, the cured epoxy resin is a product of high cross linking with three-dimensional structure, in which the movement of the segments is very difficult and results in brittle materials. It limits the application in high impact resistance and anti-fracture properties. Therefore toughening modification of epoxy resin becomes a research focus in high-performance resin material. In this paper, we introduced the silicone-containing copolymer into the epoxy resin. Compared with other polymer materials,the introduction of the relatively soft silicone segments (Si-O) into the epoxy resin will have a tendency to migrate to the surface of the epoxy resin, thereby the surface tension and the surface energy of the material will reduce, the hydrophobic in the surface of the material will be improved, the other properties such as flexibility, thermal stability, weather resistance, electrical insulating will be improved significantly as well.In this work, new blends were prepared by diglycidyl ether of bisphenol A (DGEBA) epoxy resins, DDM,DMS-E09, DMS-Elland PI-Siloxane.The phase diagram of the system without curing agent by thermally induced phase separation and the phase diagram of the system with curing agent(DDM) by reaction induced phase separation were obtained via testing the cloud point temperature using optical microscope, the phase diagram of the system all showed the upper critical solution temperature (UCST). The system with curing agent showed the highest temperature of phase separation at a ratio of15wt%polyimide what means bicontinuous or inversion phase structure would be obtained when the weight of PI was closed to15wt%.According to the final phase structure of the system observed by scanning electron microscopy, it was found that DMS-E09could increase the interfacial interaction between the silicone and epoxy resin effectively as well as to improve the compatibility. Energy spectrum showed that silicon content in surface was the highest, follow by the theoretical silicon content, the cross-section silicon content was the lowest. The reason is that PDMS in the E09migrated and enriched to the surface of the modified epoxy as the block copolymer content increases, thus the silicon content at the surface of the epoxy blends increase.Studies on curing kinetics of epoxy resin were carried out using differential scanning calorimeter (DSC). The calorimeter was operated in both isothermal and dynamic modes. Study on the relationship between curing kinetics of DGEBA/DMS-E09/DDM and DGEBA/DMS-E11/DDM systems. The results show that:(1) For the DGEBA/DMS-E09/DDM system, Ti, Tpå’ŒTf increased gradually with the increase of DMS-E09, the activation energy Ea changing trend is not obvious, the time to achieve the ultimate degree of curing and the reaction rate decreased with the increase of DMS-E09.(2) For the DGEBA/DMS-E11/DDM system, Ti, Tp and Tf increased gradually with the increase of DMS-E11, the reaction rate decreased while DMS-E11content of20%(wt%) but the extent was not obvious, and had little effect on the conversion. Compare the two systems, it was found that Tp in DGEBA/DMS-E11/DDM system was Significantly higher than which in DGEBA/DMS-E09/DDM system, the time to achieve the ultimate degree of curing of DGEBA/DMS-E11/DDM system was longer than which in DGEBA/DMS-E09/DDM system.The results of contact angle indicated that there existed a similar trend in DGEBA/DMS-E09/DDM system as well as in DGEBA/PI-Siloxane/DDM, Contact angle increased gradually with the increase of DMS-E09or Pl-Siloxane almost in a linear relationship and the surface energy decreased significantly.It is shown that a large number of non-polar silicone groups enriched in the surface of the epoxy resin, finally the surface energy was reduced and the hydrophobic of the epoxy resin was improved.