POLYMERISATION OF VINYL ACETATE IN AQUEOUS EMUL5IFIER WITHOUT MICELLES
POLYMERISATION OF VINYL ACETATE IN AQUEOUS EMUL5IFIER WITHOUT MICELLES
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Date
1983-06
Authors
YETUNDE, OLUREMI MOSURO,
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Abstract
The effect of four different monomer and emulsifier
concentrations and two different initiator concentrations
on the kinetics of polymerisation of vinyl acetate at 55 + 0.05 oC,
below the critical micelle concentration of sodium lauryl
sulphate as emulsifier, using potassium persulphate as the
initiator, and on some properties of the polymer samples produced
have been studied. The form of the dependence of the rate of
of polymerisation (R ), on the exponent of the emulsifier and
initiator concentrations was also studied. The forms of the
variation of limiting viscosity and Huggins• constant with (%)
conversion of monomer to polymer were also studied.
The rate of polymerisation of vinyl acetate under the
conditions studied was appreciable, increasing with increase
in the emulsifier concentration. The form of the dependence
of rate on the exponent of emulsifier concentration on the
rate of polymerisation was independent of monomer concentration
but dependent on the initiator concentration. The rate of
polymerisation decreased as the monomer concentration
increased. Generally, polymerisation of vinyl acetate in
the absence of micelles is explained as due to the combination
of factors including partial solubility of vinyl acetate in
water, agitation which allows for interaction of monomer
molecules with the free radicals, and diffusion of free
radicals from the aqueous to the monomer layer. Delay in the
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action of these factors have caused an induction period to
the polymerisation reaction.
Limiting viscosity values for the polyvinyl acetate -
methanol systems at 30 +/- 0,05 C were obtained and used to
qualitatively describe the pattern of the dependence of polymer
molecular characteristics mainly (molecular weight with
branching) on the conditions of the polymerisation. Conclusions
were drawn showing that molecular characteristics of the
polymers produced at lower conversions of the monomer are
significantly different from those at higher conversions. These
properties, are also affected by emulsifier, monomer and
initiator concentrations. Huggins constant was used as a
measure of polymer-solvent interactions and an estimate of
size of polymer backbone, degree of branching and length, as
described qualitatively.
Generally, the study shows that many of the results
can not be explained in terms of the classical theories of
emulsion polymerisation of vinyl monomers.
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Description
A thesis submitted to the Postgraduate School,
Ahmadu Bello University, in partial fulfilment
of the requirements for the degree of; MASTER
OF SCIENCE in POLYMER SCIENCE AND TECHNOLOGY.
Keywords
POLYMERISATION, VINYL ACETATE, EMUL5IFIER, MICELLES