氯化胆碱/尿素低共熔溶剂改性木质素的环氧固化体系

采用氯化胆碱(ChCl)和尿素(U)在温和的条件下制备低共熔溶剂(ChCl/U-DES),用该溶剂处理玉米芯酶解木质素(CEL)后用于双酚A型环氧树脂(E-51)的固化剂(ChCl/U-DES-CEL)。结合DSC、TG和DMA测试,对树脂的固化工艺及固化后树脂的拉伸性能、热稳定性和动态热机械性能等加以分析与表征,阐明其固化作用机理。结果表明:经ChCl/U-DES改性后的木质素体系可以不经分离直接用作环氧树脂的固化剂,在140℃预固化2 h后再在160℃固化2 h的条件下,ChCl/U-DES-CEL固化剂的用量仅为E-51质量的1/8,明显低于常规聚酰胺固化剂(PA650)的用量,且增加树脂热稳定性效果显著,所得到的固化树脂的拉伸强度、初始热分解温度和玻璃化转变温度分别比对照样增加了30.2%、30℃和54℃;储能模量在30℃时达1 874 MPa,比对照样PA650/E-51提高了77.5%。

Effect of Modified Lignin b y Cho line Chloride/Urea Deep-eutectic Solvent on Cur ing Properties of Epoxy Resin

Deep-eutectic solvent(ChCl/U-DES)was prepared under mild conditions using choline chlo-ride(ChCl)and urea (U),which was employed to modified cellulolytic enzyme lignin of corn cobs(CEL), and then, the system of ChCl/U-DES and the modified lignin was used directly as the curing agent(ChCl/U-DES-CEL)of epoxy resin(E-51)without fur-ther separating.The curing process of resin,especially for the temperature and time were optimized and the tensile strength was compared with that using PA 650 as curing agent,the thermal properties of the cured resin were compared by DSC, TG and DMA.The curing mechanism was elucidated.The system of lignin modified by ChCl/U-DES without further separa-tion can be used as a curing agent of E-51.The recommended curing process was the precuring at 140℃for 2 h,and then curing at 160℃for 2 h.The fraction of curing agent with the ChCl/U-DES-CEL was only 12.5%of E-51 resin(w/w), less than the control group PA650,but the cured resin thermal stability was remarkable in the tensile strength,and the ini-tial thermal decomposition temperature and the glass transition temperature of the cured resin were30.2%,30℃and 54℃higher than those of the control group,respectively.The storage modulus was 1 874 MPa at30 ℃,increased by 77.5%.