Study On EPA Modified Phenolic Resin And Application For Light-alloy Casting

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.