SOME ASPECTS OF EMULSION POLYMERISATION OF VINYL ACETATE.
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.
Description
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