Synthesis And Modification Of Styrene Acrylate Microemulsion For Waterborne Heavy-duty Anticorrosive Coating

A series of styrene-acrylate microemulsions with preferable properties were prepared via semicontinuous dropwise manners, using ammonium persulfate (APS) as initiator, styrene (St) and butyl acrylate (BA) as main monomers, and acrylic acid (AA) as carboxyl functional monomer. The effects of emulsifier types and dosage, co-emulsifiers dosage, acrylate acid dosage, silane coupling agent dosage on the performance of styrene-acrylate latexes and films were discussed.This thesis consists three parts, Part One:the influence of emulsifier types and dosage on the performance of microemulsions. A series of styrene-acrylate microemulsions were prepared using three kinds of anionic emulsifiers:ammonium sulfate allyloxy nonylphenoxy poly (ethyleneoxy)(10) ether (DNS-86),1-allyl-a-hydroxy alkyl sulfonate and sodium dodecyl sulfate (SDS), and two kinds of nonionic emulsifiers:ammonium p-nonyl phenoxy polyoxyethylene (4) sulfate (CO-436), octylphenol polyoxyethylene (10) ether, to compound six different emulsified system respectively. Among these, the properties of microlatex prepared by the DNS-86/OP-10emulsified system show better. The results of conditions optimization show that:When the ratio of the monomer to emulsifier(M/S) was12.5:1, the amount of coemulsifier isopropanol was1/3of the total emulsifiers, the polymerization temperature was80±1℃, stable microemulsion was prepared with the solid content was39.37percent and the particle size was60-70nm.Part Two:the influence of functional monomers dosages and adding manners on the distribution of the carboxyl groups of styrene-acrylate microemulsions, and the effect of the distribution of carboxyl groups on the properties of microemulsions and its films were discussed systematically. Results showed that with the increase of the carboxylic monomers, the amount of carboxylic groups distributed on the surface of particle (Cs), embedded in particle (Cb) and in aqueous phase (Cf) increased. There has a big difference on the distribution of carboxyl groups while adding manners changed, when half of the acrylate acid poured in the seed, the other half mixed in the monomers and dropped to the polymerization system, the amount of carboxylic groups distributed on the surface of particle was maximum, when all the acrylate acid poured into the seed, the amount of carboxylic groups embedded in particle (Cb) was maximum. The more carboxylic groups distributed on the surface, the viscosity of the microemulsions was higner, the thermostability and the mechanical properties were better, but the water resistance and the acid (alkali) resistance were worse. The microemulsion has better overall performance when the amount of the acrylate acid was2%, and half of the acrylate acid poured in the seed, the other half mixed in the monmers and dropped to the polymerization system.Part Three:Two types of silane coupling agent:γ-methacryloxypropyltrimethox--ysilane (KH-570) and vinyltriisopropoxysilane (AC-76) has been used to modify the microemulsion. The effect of the silane coupling agent dosages on the microemulsion films has been investigated. The results indicated that with the amount of the silane coupling agent increased, the drape of the films increased, the surface energy decreased firstly and remained little changed later on, the degree of crosslinking increased firstly and remained little changed later on, the water resistance and the acid (alkali) resistance were better firstly and changed worse later on, while the thermostability improved; The tensile strength of the films contained KH570was enhanced but its flexibility was poor, while the tensile strength of the films contained AC-76was enhanced little but its flexibility kept good.