Synthesis Of A Novel Phosphorous-containing Cycloaliphatic Epoxide And Study Its Properties

Cycloaliphatic epoxides, which contain rigid cycloaliphatic rings and epoxide groups linked to the cycloaliphatic rings, exhibit different properties from BPA, such as low viscosity, good heat resistance, a low expansion coefficient and so on. They have been found to be useful in a wide variety of industrial applications, such as reactive diluents, encapsulating compounds, coatings. But, in generally, the synthesis process of cycloaliphatic epoxide is difficult with low yield and high cost. For these reason, the synthesis and application of novel cycloaliphatic epoxy resins are attracting more and more attention.In this paper, dicyclopentadiene and ethylene glycol in mole ratio 2:3 with BF3·(C2H5)O as the catalyst (quantity of catalyst is 5% of the mole number of dicyclopentadiene) reacted at 100℃for 5h to give ethylene glycol monodicyclopentenyl ether (I) in 75.6% yield. Phosphation of I with phosphorus oxychloride was carried out with triethyl amine as an additive colligating acid and the yield of phosphate-type cycloalkene (II) was 95%. Then a novel phosphorus-containing trifuntional cycloaliphatic epoxide (III) was produced in 75% yield by epoxidation of II with m-chloroperoxybenzoic acid at 0℃for 10h. The structures of the epoxide (III) and its intermediates were determined by several methologies such as FTIR spectroscopy, 1H-NMR spectroscopy, 31P-NMR spectroscopy, Mass spectroscopy and epoxide equivalent.The cure kinetics of phosphate-type cycloaliphatic epoxide/anhydride themosetting systems were studied under dynamic curing conditions by Differential Scanning Calorimetry (DSC) technique, which was helpful for determination of the curing process technology. The thermal properties and flame retardant properties of the cured epoxy systems were examined by Thermal Gravimetric Analysis (TGA), Dilatometer (DIL) and Limited Oxygen Index (LOI). The epoxide and hexahydrophthalic anhydride (or methyltetrahydrophthalic anhydride) as a hardener were mixed with a 1:0.8 equivalent ratio of epoxide to anhydride groups. The homogeneous mixture was cured first at 80℃for 6h, then at 150℃for 12h, and finally at 170℃for 6h. The cured epoxide showed a good thermal stability (the initial decomposition temperature was 285.8℃), a low coefficient of thermal expansion (7.31×10-5/℃), and a high flame retardance (the LOI value of 24.9 was achieved without any flame-retardant additive).The photosensitivity of cationic polymerization of phosphate-type cycloaliphatic epoxide initiated by photointitiator IHT-PI820 (ditolyl iodonium hexafluorophosphate) was studied. The promotion of benzyol peroxide on polymerization of the cycloaliphatic epoxide which initiated by IHT-PI820 was also studied. The results showed that BPO could promote the initiation of IHT-PI820 significantly. The photoinitiated cured system with 4% of BPO got a 90.6% gel yield after 3min UV exposure, which was faster than the case without BPO. The photo-cured polymer exhibited a good thermal stability with a higher thermal decomposition temperature over 300℃and a char yield about 29.92% at 700℃.The resultant novel phosphorous-containing cycloaliphatic epoxy resin was prospected to be used as flame-retardant reactive diluents, electronic encapsulating compounds or photoinitiated curing coatings.