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为提高树脂砂的强度 ,分别在 p H=14、p H=8和p H =3下 ,合成 3种碱性酚醛树脂 ,采用氢核磁谱图 (1 HNMR)和红外谱图 (IR)分析了树脂分子结构 ,并将所合成的树脂应用于 CO2 气硬冷芯盒中。结果表明 ,在 p H=14下合成的树脂分子中具有大量活性羟甲基且部分苯环以甲醚桥相连 ,其树脂砂具有较高的即时强度与终强度 ,其中最大初强度为 0 .6 4 MPa,终强度为 0 .80 MPa。在 p H=8下合成的树脂分子中虽存在大量活性羟甲基但苯环间基本上以亚甲基桥相连 ,其树脂砂抗拉强度较低。而在 p H=3下合成的树脂中基本没有活性羟甲基 ,其树脂砂即时强度最低
In order to improve the strength of resin sand, three basic phenolic resins were synthesized at p H = 14, p H = 8 and p H = 3, respectively. Their structures were characterized by 1 HNMR and IR spectra The resin molecular structure, and the synthesized resin used in CO2 gas hard cold box. The results show that the resins synthesized at p H = 14 have a large number of active methylol groups and some benzene rings are connected by methyl ether bridge. The resin sand has high instantaneous and final strength, of which the maximum initial strength is zero. 6 4 MPa, final strength of 0 .80 MPa. Although there is a large number of active methylol groups in the resin molecules synthesized at p H = 8, the benzene rings are basically linked by methylene bridges, and the tensile strength of the resin sand is low. While the resin synthesized at p H = 3 has almost no active methylol, the lowest instant resin sand strength