The kinetics of emulsion polymerization of vinyl acetate using the redox system potassium persulfate – acetone sodium bisulfite as initiator is studied. The effect of the reaction conditions on the rate of polymerization and on the number and size of the formed particles is established. The polymerization proceeded smoothly till high conversion and yielded stable emulsions. The apparent activation energy for the polymerization system has been calculated.
The emulsion polymerization of vinyl acetate using potassium persulfate and cyclohexanone sodium bisulfite as redox pair initiation system was studied. The rate of polymerization, maximum conversion, and the number of polymer particles produced were found to change with redox initiator, monomer and emulsifier concentrations, and temperature variation. The rate of polymerization was found to be dependent on the initiator, the monomer, and the emulsifier concentrations to the 0.88, 0.22, and 0.20 powers, respectively. The K2S2O8–NaHSO3 redox system was found to decrease maximum conversion and doesn't form a stable emulsion. The apparent arrhenius activation energy (Ea) estimated for the polymerization system was 65.6 kJ/mol. The viscosity average molecular weights for some obtained poly(vinyl acetate) were determined.
Emulsion homopolymerization of vinyl acetate (VAc) and emul sion copolymerization of VAc with butyl acrylate (BuA) using potassium persulfate-acetone sodium bisulfite as a developed redox pair initiation system were investigated. The rate of copolymerization decreased with increasing BuA content. The copolymer compositions were determined by H1 NMR analysis and the reactivity ratios for VAc and BuA were calculated using the Fine man-Ross equation and found to be r1 = 0.21 and r2 = 3.3 respectively. The prepared stable emulsions were incorporated into latex paint formulations. The physico-mechanical properties of the dried polymer and paint films im proved significantly with increasing BuA content.
l'lie experimental riiethods crnployt:tl wen: itlentical with ttiosc described previously [17, IS].The image analyzer (Biltlanalyse IBAS 1 arid 3) was used to measure t h e average diameters and average area of different polymer particles. Also, i t was used t o plot absolute frequency (ABS frequency) agninst area and rnaxinititii diameter (,!Imax). The number of polymer particles p i x unit volirmn of water (iV,) was calcdatetl from the monoitier vonvcrsion Slk Tlie volume average iliarnctcr OF tlic polymer particles d, was cletermiiiecl by a transmissioii crlec~ti~c~ri microscope using the following cqriations:hi,, is tltv initial inonomcr ronccittration iiii(l p,, is the (Lensity of the polynicr. The viscosity avcmge inolecular~ weights of the obtainetl poly(viny1 acetate) samples were tleterminetl b y incasurvmerits in benzene solution :it 30°C employing the equation [ 1' 31 : [ t , ! = 5.63. '10-4. Bv'J"''
Resrills nnd discussion
I . Dcpendeircc of i){il!jiii~,~i~iiliiitr ritte oil iiiilitt/or coiiceiilmlioiiA s tlic emulsion 1dyirtc:rization of vinyl :icc:t:ite lorrtls a Iictcrogcrieous systi:Iti, we are obligctl to take the initial r:i tc: or polyi1icriz:itioii into coiisicl(:r;itioiI to iivoitl coiiipli-(::itions t l i i e to polyrncr h i i i ; i t . i o t i in the tnctlitrtn. Tlie initial r:ite of I)olyiric:riziitiorl was tltrtt*rininc:tl h t l i tho slope of tlii: linwr portion of tlit: c:orivi:rsion vorsiis tirric: ciirvi's i i p to 'LOO/, convc:rsioii.
J~A D R A N ant1 S I~E X O Y :Kinetics ant1 mcclianisni of thc cmulsion polyniet*iration of vinyl ncctatc Acta ?olyrn*riu 42 (1991) Nr. 1
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