SOME ASPECTS OF EMULSION POLYMERISATION OF VINYL ACETATE.

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Date
1983-06
Authors
OKOLO, LAURETTA ACHUNA
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Abstract
The emulsion polymerisation of vinyl acetate was investigated using a wide range of sodium lauryl sulphate, (SLS), as emulsifying agent, potassium peroxydisulphate initiation and at two temperatures, 58°C and 6S°C. Vinyl acetate was found to polymerise appreciably even below the cmc of (SLS). The form of dependence of rate of polymerisation on the exponent of the emulsifier was studied. The rate of polymerisation Rp , was found to show a diminishing dependence on the exponent of the emulsifier concentration contrary to the Sinith-Ewart scheme of ideal emulsion polymerisation of water insoluble monomers. A greater dependence of R on the exponent of the emulsifier concentration was found below the cmc than above the cmc of (SLS). The form of dependence was also affected by temperature. The exponent of the emulsifier concentration increased with temperature below the cmc of (SLS) and decreased with temperature above the cmc of (SLS). This shows that R is less dependent on the [So] at increased temperatures. Viscosity studios were carried out and the intrinsic viscosity was found to be dependent on molecular weight and chain branching. The occurence of branching is favoured especially at high temperature. Higher intrinsic viscosity values were obtained for polyvinyl acetate vi samples produced below the cmc than above the cmc of (SLS), suggesting that the molecular weight of the polyvinyl acetate samples formed while polymerising vinyl acetate below the cmc of (SLS) as emulsifier are higher than when polymerising above the cmc. Temperature was found to enhance the occurence of branching hence polyvinyl acetate samples obtained above the crno are expected to have higher molecular weights at 58°C. The interaction between the polymer and the solvent molecules in the viscosity study were found to be less for polymers produced below the cmc of (SLS) due to the greater molecular weight. Tests on tensile mechanical properties were also carrie . out on the polyvinyl acetate samples obtained from emulsion polymerisation. These properties were found to be affected by the presence of branches and modification of the macromolecular structures of the polymer. The solvent used was also found to cause some modifications on the polymer structures. The values of the tensile mechanical properties were relatively high. TENSILE strength and initial modulus of the polymers obtained showed opposite trends of variation to that of (%) elongation for different (%) conversion. The observations from the variation of intrinsic viscosity and the tensile mechanical properties showed that these properties are affected by modifications in the polymer chain.
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thesis submitted to the Postgraduate School, Ahmadu Bello University, in partial fulfilment of the requirements for the degree of: MASTER OF SCIENCE of POLYMER SCIENCE AND TECHNOLOGY. Department of Chemistry, Faculty of Science, Ahmadu Bello University, Zaria - Nigeria .
Keywords
ASPECTS, EMULSION, POLYMERISATION, VINYL, ACETATE
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