| Cationic Poly(vinyl acetate) emulsions(PVAc) own a broad market prospect andwidespread applications in many areas because of their unique properties. However,they are difficult to be successfully produced for there are a lot of elements that willaffect their synthsis process. In this thesis, the influence of the trace constituents invinyl acetate (VAc) monomer on the synthesis and properties of cationic PVAcemulsion was investigated for the first time. The main trace constituted, i.e. acetateacid(AcOH), of VAc monomer was designed into the formula of the emulsion, and itseffect on the monomers, emulsification and initiation systems of the trace constitutesin VAc monomer was studied carefully. Furthermore, the effect mechanism of AcOHon the cationic emulsion polymerization was probed and was contrasted with theanionic one. The obtained results can provide favorable conditions for production andextensive use of cationic PVAc emulsions.The main contents of this thesis are followd:1. Based on a careful consideration of the production process of VAc monomer,the VAc monomer produced by Nature Gas Process in Sichuan Vinyl Corporation waschosen in this study. The trace constituent in such vinyl acetate monomer was mainlyAcOH ensured by the analysis of Gas Chromatograph-Mass Spectrometer.2. A new type of hyper-branched cationic Gemini surfactant (Gemini)coordinated with OP-10was used as the emulsification system for the cationicemulsion polymerization. Potassium peroxydisulfate (KPS)-sodium metabisulfite wasacted as initiator and methacryloyloxy ethyl trimethylammonium chloride (DMC) asthe cationic co-monomer to synthesize cationic PVAc emulsion. Fourier-transforminfrared spectroscopy (FTIR) was used to characterize the structure of prepared polymer. The ζ potential, particle size and Tg of polymer were determined with the ζpotential analysis instrument, granulometer and differential scanning calorimetry(DSC). The experimental results demonstrated a slightly influence of AcOH on theemulsion stability, polymer structure and ζ potential, but a significantly one on theparticle size and Tg. The particle size was decreased with low AcOH loading amount,but when the loading amount of AcOH was higher, the particle size increased. And Tgof polymer owned a similar trend as the particle size.3. To investigate the reason that caused the effect on the properties of PVAcemulsion by AcOH, the adsorption spectrum of the monomer was detected via theultraviolet spectrophotometer before and after added AcOH, no obvious change in UVspectrum of VAc monomer was observed，inducing that there was little effect ofAcOH on the monomer structure. Then, the critical micelle concentration (CMC) andcritical surface tension (γCMC) of op-10and Germini surfactants were measured in thepresence of AcOH. The results demonstrated a slightly influence on the criticalsurface properties of OP-10, but significantly effect on the CMC of Gemini cationicsurfactant by AcOH, which could be one of the reasons for the properties changedwith or without AcOH. The polymerization kinetics method was subsequently used toanalyze the effect of AcOH on polymerization rate. The polymerization rate could beaccelerated with little AcOH existing, while decreased as the loading amountincreasing after a certain value, which might be another reason for the varying ofemulsion properties.4. The influence of AcOH on anionic PVAc emulsion properties andpolymerization process was detected for a further understanding the effect of AcOHon PVAc emulsion, and the obtained results indicated that, no effect could be found onthe structure of anionic PVAc emulsion. Meanwhile, there was no obvious change inparticle size, Tg and polymerization rate of nionic PVAc emulsion. However, thestability of the anionic PVAc emulsion was poor, which was different from that of thecationic PVAc emulsion. The chemical stability and secondary centrifugal stabilitydeclined also. The ζ potential varied significantly after introducing AcOH. The reasonis that, usually, the anionic polymerization system was conducted in weak alkalinecondition, and the surface of anion latex had negative ions, so the double electric layerof latex formed based on such a condition could provide the emulsion with theelectrostatic stability. When AcOH was introduced, the polymerization system becameslightly acid, which would change the electric double layer structure of the latexparticle, followed by a change in ζ potential, resulting in a declined emulsion stability. |
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