二甲氨基乙氧基氧杂硼烷对环氧树脂的潜伏固化活性

摘要

2-( 2-Dimethylaminoethoxy )-4 , 4 , 5 , 5-tetramethyl-1 , 3 , 2-dioxaborolane ( PDB ) , 2-( 2-dimethyl-aminoethoxy)-5,5-dimethyl-1,3,2-dioxaborinan(NDB) and 2-(2-dimethylaminoethoxy)-1,3,2-benzodiox-aborole( CDB) with five-membered ring or six-membered ring contained intramolecular nitrogen boron coordi-nate bond(N→B), which hydrolytic stability was determined by exposure observation method. Differential scanning calorimetry, oven curing experiments, gelation time experiment and infrared spectroscopy ( FTIR ) were used to investigate their effect on the curing activity and latent property of E51 epoxy resins. The appar-ent activation energy associated with curing reaction(Ea) was calculated by Ozawa-Avrami method. The elec-tron density of boron atom and the degree of N→B complexation in dimethylaminoethoxy hetero-oxy borane were influenced by the conjugative effect of phenyl ring, the donor effect of alkoxy and the steric hindrance effect. The conjugative effect of phenyl ring decreased the electron density of boron atom and strengthened the complexation degree of N→B of CDB, which induced a lower hydrolytic stability and curing activity on E51 than NDB and PDB with the donor effect of alkoxy substitution. A higher shielding effect of six-membered ring on boron atom caused a higher hydrolytic stability and curing activity than five-membered ring while a lower curing activity exhibited good latent performance for E51 . The degree of conversion of one-pot E51-PDB epoxy resin[aE(t)] after depositing 3 months at room temperature was 0.22.%以3种含分子内N→B配位键的环状结构的二甲氨基乙氧基氧杂硼烷：β,β'-二甲氨基乙氧基-4,4,5,5-四甲基-1,3,2-二氧杂戊硼烷( PDB)、β,β'-二甲氨基乙氧基-5,5-二甲基-1,3,2-二氧杂己硼烷( NDB)和β,β'-二甲氨基乙氧基-1,3,2-苯并二氧硼烷(CDB)为研究对象,采用敞口观察法测定其水解稳定性,通过差示扫描量热法( DSC)、烘箱固化实验、恒温潜伏性实验及红外光谱( FTIR)分析,研究3种氧杂硼烷对环氧树脂的固化活性和潜伏性能,采用Ozawa-Avrami法估算固化反应的表观活化能( Ea ).结果表明,苯环仔电子共轭效应、烷氧基给电子效应以及氧杂硼烷空间结构差异等因素影响了3种二甲氨基乙氧基氧杂硼烷上硼原子电子云密度及N→B配位络合强度,导致其水解稳定性及对环氧树脂的固化活性顺序为NDB>PDB>CDB,潜伏性能则正好相反. E51与PDB组成的单组分环氧树脂在常温放置3个月后,环氧基的转化率为0.22.