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Studies On The Morphological Development Of Latex Particles In Semi-continuous Emulsion Polymerization Process

Posted on:2003-08-14Degree:DoctorType:Dissertation
Country:ChinaCandidate:K ZhaoFull Text:PDF
GTID:1101360065956114Subject:Chemical processes
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The morphology of latex is a very important, complicated and interesting topic in emulsion polymerization. Different morphologies of latexes can perform different functions, and so the understanding and controlling of the mechanism and development of the morphology of composite latex are beneficial for the industry application. The semi-continuous emulsion polymerization is a very important procedure and, widely used in industry therefore the research on the morphology of composite latex is useful. This paper studies the mechanism and development of the morphology of composite latex in semi-continuous process, especially the morphological evolution in two stages seeded emulsion polymerization. The TEM of photos of latex in semi-continuous process provides us with the important proof of morphological evolution, and with the basic view of points to calculation and simulation about the thermodynamic equations and morphological evolution.This article studies the morphological evolution of composite latex in semi-continuous Uvo-stages seeded emulsion polymerization process, in the systems of PVAc(Vinyl acetate)/PBA(butyl acrylate), PVAc/PST(styrene), PST/PVAc ,P(ST-co-BA) (styrene-co-butyl acrylate)/PVAc,PSt/PMMA(methyl methacrylate) and PMMA/PS, and the conclusions are as follows, in which the same emulsifier(Sodium Dodecyl Sulfate and Octylphenoxy Polyethoxy Ester), initiator(Potassium Persulfate) are adopted for the seed and the second stage polymerization, in starved and overflowed semi-continuous process, and polymerization is in the same reaction vessel. PVAc/PBA: When the PVAc as seed, BA is injected in semi-continuous process in starved or overflowed conditions and polymerized, in the process the latex is taken out and investigated by the TEM. The conclusion is as follows: The core-shell composite latex is found in the process of starved condition, with the PVAc as core and the PBA as shell. The inverted core-shell composite latex, with the PVAc as shell and the PBA as core, is got in the process of overflowed condition. When the latex is taken out in different time and kept warm to the end of the reaction in the starved condition, the morphology of composite latex inverts and the inverted core-shell, with much of PBA as the core and PVAc as the shell, is found. The morphological evolution to the thermodynamic equilibrium in some degree can be got in the process of starved or overflowed condition, and kept warm to the end of reaction in the starved condition. The facts of the morphological evolution of latex in experiments help us to understand the paradoxical points of view about the morphology of latex in the system of PVAc/PBA, which is investigated by many people and the contrary views exists. Besides the investigation about the morphological evolution, the apparent dynamics of BA monomer polymerization, as well as its effect on the morphology of latex, is studied, in the process the amountof initiator and injection speed of BA. monomer varied and the others are kept unchangeable. The apparent kinetics of emulsion polymerization for PVAc/PBA core-shell in semi-continuous process is found in the experimental equation: Rpw=K*Ra, with K=l-0.02Ra,where Ra is the injection speed of BA monomer(mole/s), Rpw is the stable polymerization speed(mole/s) and K is the experimental coefficient(no unit).The relation between Rpw, Ra and initiator/monomer shows that the injection speed of BA exerts a main effect on the polymerization speed and the morphology of latex in the process,-and the action on them from the initiator/monomer is less.PVAc/PST: When the PVAc as seed, St is injected in semi-continuous process in low-speed or overflowed conditions and polymerized, in the process the latex is taken out and investigated by the TEM. Although the injection speed of St is very low, the polymerization speed is less than that and the residual ST monomer is accumulated in the process At the beginning of polymerization, the PST is found in the form of strawberry outside the seed of PVAc, however, at last the PST is get...
Keywords/Search Tags:Emulsion polymerization, Core-shell, Morphology, Thermodynamics, Semi-continuous, Simulation, Cluster, TEM, Butyl acrylate, Styrene, Methyl methacrylate, Vinyl acetate, degradable container
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