【作者】 冀运东；

【导师】 罗吉荣；

【作者基本信息】 华中科技大学 ， 材料科学与工程， 2005， 博士

【摘要】 本文采用理论分析和实验研究相结合的方法,研究了热塑性酚醛树脂性能的控制规律,研究了EPA改性酚醛树脂的合成工艺及高强度易溃散覆膜砂的制备技术,探讨了酚醛树脂特性与覆膜砂性能之间的相互关系,取得了以下主要成果:系统研究了甲醛/苯酚(F/P)比例、缩合时间、催化剂种类等合成工艺对热塑性酚醛树脂的软化点、聚合速度、流动性和溶解粘度等性能的影响。甲醛/苯酚(F/P)摩尔比在0.5-0.9的范围内,随着F/P摩尔比的增加,合成树脂的平均分子量增加,分子量分布变窄,软化点逐渐增加,聚合速度变快,流动性下降,溶解粘度增加。在树脂合成的过程中,延长缩合时间,酚醛树脂的平均分子量增加,分子量的分布不变;树脂的软化点和聚合速度直线上升;流动性下降;溶解粘度上升。系统研究了不同的酸催化剂草酸、A酸、硫酸、盐酸对酚醛树脂性能的影响,发现酸催化剂类型对酚醛树脂的官能团结构没有明显影响、但影响树脂的平均分子量及分布等物理特性。采用硫酸催化剂合成树脂的软化点、平均分子量和分子量分布系数值最大,采用草酸作催化剂,对降低树脂的聚合速度和提高流动性有利。而A酸作催化剂时,显著提高合成树脂的聚合速度并降低流动性。实验结果表明,采用由多种酸混配的复合催化剂,可获得综合性能优良的酚醛树脂。研究了硬脂酸钙、邻苯二甲酸二丁酯和水杨酸等添加剂对合成树脂性能的影响。结果表明,随着硬脂酸钙量的增加,树脂的软化点和聚合速度也相应的增加,当硬脂酸钙加入量大于2%时,软化点和聚合速度又随加入量的增加而减少。在树脂合成过程中加入二丁酯,会降低树脂的软化点、减慢聚合速度。而水杨酸的加入则提高树脂的聚合速度。根据对轻合金铸造覆膜砂服役条件的分析,提出了改性酚醛树脂分子结构设计的原则:树脂主链上含有长的烷基链等柔性基团的嵌段共缩聚;酚醛主链上同时具有醚键连接和亚甲基键连接,提高树脂韧性,降低树脂分解温度,降低残留碳密度,控制树脂熔体粘度。成功开发了一种EPA改性酚醛树脂,采用长链脂肪二元酸EPA作为改性剂,草酸+A酸作为复合催化剂,改性酚醛树脂具有软化点低、聚合速度快、流动性好、平均分子量大,分子量分布系数大、存放性好、在350-400℃之间迅速分解的特点。系统研究了EPA加入量对改性酚醛树脂性能的影响,当EPA加入量小于10%时,随着EPA加入量的增加,软化温度降低,聚合速度加快,溶解粘度上升,流动性变小;当EPA加入量大于10%时,聚合速度变慢,流动性增加。采用回归分析法研究了树脂软化点和聚合速度与覆膜砂常温抗弯强度的相互关系。随着软化点的降低和聚合速度的提高,覆膜砂常温抗弯强度呈现上升趋势。测定了不同树脂的熔融粘度-温度变化曲线,发现不同软化点的树脂达到熔融粘度趋于恒定时(45-50泊)的温度差别很大。指出若按传统的覆膜温度等于软化点加上(40℃-50℃)制备覆膜砂,有可能导致覆膜温度过低或过高,损害树脂的粘接效率,导致覆膜砂强度降低。提出覆膜温度应等于熔融粘度50泊时温度加上40℃的控制原则。研究了EPA改性树脂覆膜砂的制备技术,确定了如下工艺参数:树脂加入量1-2%,覆膜温度130±5℃、固化剂加入量12±0.5%(wt%/R),冷却水0.5-1%(wt%/S)。覆膜砂(2%树脂加入量)常温抗弯强度6.8MPa,残留强度0.2MPa,溃散性96.5%,高温持久时间230秒,并成功的用于生产汽缸盖、进气歧管和蜗轮壳等铝合金铸件。开发出一套酚醛树脂合成工艺自动控制系统,该系统选用具有模拟量控制的可编程逻辑控制器PLC加上位机模式,利用梯形图和组态软件,具有造价低,操作简单,工艺参数控制准确的特点,为稳定树脂的质量创造了有利条件。更多还原

【Abstract】 The dissertation, using the method of theoretical analysis combining with experimental research, studies the controlling rules of novolac type phenolic resin, synthesis processes of EPA modified phenol resin, the manufacture technology of the shell sand with high strength and collapsibility and the relationship between phenolic resin and shell sand. The fundamental achievements are as follows :It studies systematically the effect of the synthesis processes such as formaldehyde to phenol molar ratio (F/P), condensation time and the type of catalyst on properties including soften point, gel time, fluidity and solvent viscosity of novolac type phenolic resin. When formaldehyde to phenol molar ratio (F/P) is between 0.5 to 0.9, with F/P increases, the average molecular weight of the resin increases, molecular-weight distribution narrows down, soften point increases, gel time reduces, fluidity decreases and solvent viscosity increases. With the prolongation of condensation time, average molecular weight of the resin increases, molecular-weight distribution is not changed, soften point and gel time increase linearly, fluidity decreases and solvent viscosity increases.It studies systematically the effect of different kinds of acid catalysts such as ethane diacid, A acid, sulfuric acid and hydrochloric acid on properties of phenol resin. It shows that the kind of acid catalysts has no clearly effect on the functional groups of phenolic resin, but it affects its physical properties like the average molecular weight and distribution. When sulfuric acid is used as catalyst, soften point, the average molecular weight and distribution coefficient of phenolic resin are maximum. Taking ethane diacid as catalyst, gel time decreases and fluidity increases. While when A acid is used, gel time increases clearly and the fluidity decreases. The experimental results show that the excellent properties of phenolic resin can be achieved with the condition of composite acid catalyst.It has studied the effect of the addition such as calcium stearate, diisobutyl phthalate(DIBP), salicylic acid on properties of phenolic resin. With the addition of calcium stearate, the soften point and gel time increase accordingly. When the addition is beyond 2%, the soften point and gel time decrease with the increase of the addition. With the addition of DIBP, the soften point decreases and the gel time reduces. While the addition of salicylic acid increases the gel time.Based on the analysis of the attend conditions of shell sand for light-alloy casting, the principles of designing the structure of molecular of modified phenolic resin are described as: periodic copolymer between flexible group with long alkyl chain and phenolic resin fundamental chain; ether link and methylene link mixed bridge on the phenolic resin fundamental chain. The object of modification is to improve the toughness of resin, to reduce the decomposition temperature and density of residual carbon, to control phenolic resin melting viscosity. A kind of modified phenolic resin has been developed successfully, which is modified by long chain aliphatic diacid EPA and uses ethane diacid and A acid as composite catalyst. It possesses many properties as follows: low soften point, short gel time, excellent fluidity, large average molecular weight and board distribution, good storability, rapid decomposition in the range of 350℃-400℃。The effect of the EPA addition on the properties of modified phenolic resin is study systematically. When the EPA addition is below 10%, with the increase of it, soften temperature decreases, gel time fastens, solvent viscosity increases and the fluidity drops. When the EPA addition is above 10%, gel time decreases and the fluidity increases.The regression analysis is used to analyze the relationship between soften point and gel time of resin and ambient strength of shell sand. The ambient flexural strength increases with decrease of soften point of resin and increase of gel time. The curve between the temperature and melting viscosity of different resin were measured, Results show that the temperature difference is great when melting viscosity of resin with different soften point reaches constant(40-50P). If shell sand is manufactured in traditional temperature that is soften point adding 40℃-50℃, it can damaged the adhensive effect of resin because of the too low or too high temperature, so the principles is that coating temperature should equal to the temperature of melting viscosity which is 50P adding 40℃.Experiments were performed to study the effect of coating process on the properties of EPA modified phenol resin coated sand. The coating process was established: the resin addition1-2%(wt%/S), coating temperature130±5℃, the cure agent addition 12±0.5%(wt%/R), cool water0.5-1%(wt%/S). The properties of the coated sand with resin addition 2%(wt%/S) were: ambient flexural strength 6.8MPa,residual flexural strength 0.24MPa, collapsibility96.5%, high temperature lasting time 230s. It has been applied to produce aluminum alloy parts, such as air in-take tube juncture and shell of worm wheel.A auto-control system for phenolic resin synthesis has been developed, which constitute PLC with analogue control and superior computer. The software of it is based on ladder diagram and configuration software. The system is in low price and excellent effect in stabilizing the synthesis process.更多还原