| With the rapid development of automobile industry and the continuous improvement of people’s awareness of security and environmental protection, there is an increasing performance demand for reinforced automobile oil filter paper. At present, reinforced oil filter paper impregnated with water-soluble phenolic resin has defects such as brittleness, lack of toughness and poor processing performance, which make it unable to achieve actual industrial application. In this paper, waterbased phenolic resin is modified by blending with alkali-soluble acrylic emulsion in order to improve the toughness and strength of impregnated filter paper, and the toughening mechanism is studied. The specific work is as follows:Firstly, effects of weight ratio of anionic and nonionic emulsifier and dosage of emulsifiers, copolymerized monomers, type and dosage of carboxyl monomer, dosage of chain transfer agent on the stability and alkali solubility of the emulsion were studied. The results show that acrylic emulsion with no coagulation is obtained when SDS and NP-10 was at a weight ratio of 1: 2 and at a dosage of 2wt% of the total amount of monomer; emulsion with excellent alkali solubility is obtained by copolymerized with MAA, MMA and BA, and the dosage of carboxyl monomer MAA was in the range of 15% to 30%, the dosage of chain transfer agent was 1.0wt%. The prepared emulsion has passed the mechanical stability, storage stability, Ca2+ stability, and high temperature stability tests.Secondly, effects of the blending ratio, the Tg of the acrylate emulsion, dosage of crosslink monomer N-MA, acid value of the emulsion, the alkali solubility of the emulsion on the mechanical property of filter paper impregnated with phenolic resin/alkali-soluble emulsion blends was investigated. The results show that filter paper with superior mechanical property such as bursting strength, tensile strength, stiffness, folding strength can be obtained when the blending ratio is 7:3(phenolic resin: emulsion), the Tg of the emulsion was 60℃, the dosage of N-MA was 3wt% and the acid number was 150; The study results of blending system with various alkali solubility acrylate emulsion shows that: the strength of filter paper impregnated with completely alkali soluble and partly alkali soluble blends are similarly and raise much more than pure phenolic resin, while the strength of filter paper impregnated with completely alkali insoluble blends raise little. DSC test result shows that the addition of alkali-soluble emulsion can accelerate the curing rate of phenolic resin and the appropriate curing temperature of blending system is 170℃, Oil resistance test suggest that oil resistance of phenolic resin did not decline when blended with alkali-soluble emulsion. Pore size, air permeability and SEM tests show that pore structure of filter paper impregnated with blending system substantially remain unchanged and maintain excellent filtration performance.Finally, the property of blending resin system and toughening mechanism of alkali-soluble acrylic emulsion modified phenolic resin was studied. Infrared analysis show that cross-linking reaction between emulsion and phenolic resin occurred; Heat resistance analysis show that blending resin system have better heat resistance than phenolic resin when the temperature is lower than 320℃ and the mass retention rate decrease faster than phenolic resin when the temperature is higher than 320℃; Solvent resistance analysis shows that blending system present excellent solvent resistant; Degree of alkali solubility of emulsion in blending system analysis show that latex particles completely neutralized and swelling when emulsion content is less than 10% and partly neutralized when emulsion content is 20% or more. SEM and DSC analysis show that phenolic resin/emulsion blends can form interpenetrating network structure; a micro-phase separation was observed in the phenolic resin/emulsion blends occurred with high emulsion content in the blending system. The results show that the fracture mode of resin changed from brittle fracture to ductile fracture and therefore improving the mechanical property of impregnated filter paper, however, obviously phase separation occurred in the phenolic resin/alkali-insoluble emulsion blends, so the strength properties of filter paper increased little. |
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