20 июля, 2015 
Malyar This example illustrates a graft polymerisation in which colloid stabilisation and both Redox and thermal initiation techniques are employed. The reaction in effect takes place in two stages, with the vinyl acetate polymerisation taking place before the acrylic monomers are polymerised.
Thus a random copolymer will not result and reaction conditions are such that grafting of the acrylates onto the vinyl acetate backbone occurs. The use of a colloid to emulsify the acrylic monomers discourages the formation of new particles and these monomers therefore polymerise within the vinyl acetate particles.
The acrylic polymerisation is carried out in the presence of a high free radical concentration to favour the generation of sites for the grafting mechanism.
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FORMULATION 2-3
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1. An aqueous phase is made by dissolving sodium octyl phenol +4EO sulphate in 60% of the water to which is added 20% of the ammonium persulphate and the sodium hydrosulphate followed by the tertiary butyl hydroperoxide.
2. An initiator solution is prepared by dissolving the remaining ammonium persulphate in 10% of the remaining water.
3. A monomer phase is prepared by dissolving polyvinyl alcohol and sodium ethoxylated octyl phenol sulphate in the remaining water. The ethyl acrylate and methyl methacrylate monomers are added together with the sodium metabisulphite and the mixture stirred to form an emulsified monomer phase.
4. Vinyl acetate is added to the aqueous phase in the reaction vessel and the temperature is raised to 80°C. It is in this stage that the polyvinyl acetate starts to be formed.
5. The reactants are held at 80°C for 30 minutes for the polymerisation of the vinyl acetate, then the initiator phase and monomer phase are fed separately to the reaction vessel over a two hour period, whilst maintaining the reaction temperature at 80°C.
6. The reactants are held a further hour after completion of the monomer and initiator addition then cooled and filtered.
pH
Non-volatile content
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