Thesis-1998-Savage.pdf (21.99 MB)
Rheological studies of non-aqueous poly methyl methacrylate dispersions stabilised using graft copolymer steric stabilisers
thesis
posted on 2013-12-17, 11:09 authored by Matthew J. SavageSteric stabilisers were synthesised via the copolymerisation of styrene
with acrylic macromonomers. The macromonomers were prepared by
end capping reactions of poly 2-ethyl hexyl acrylate (PEHA) prepolymer
with vinyl containing species. Preliminary reaction routes
proceeded via the use of oxalyl chloride to create an acyl chloride
intermediate followed by end capping with hydroxy ethyl
methacrylate. This process was found to be inefficient due to the
moisture sensitivity of the acyl chloride. The second route involved the
direct end capping of the PEHA pre-polymer with glycidyl
methacrylate (GMA). Macromonomer conversion levels were
improved for the GMA route via the use of high temperatures and
tertiary amine catalysts. An optimum set of conditions was achieved
using 1.4 diazabicyclo [2.2.2.] octane as the catalyst and a reaction
temperature of 160 QC.
Non aqueous dispersion polymerisations of methyl methacrylate were
performed. The factors affecting particle size in both single stage and
twin stage polymerisation schemes were studied. Increases in the
particle sizes of these dispersions were observed with increases in the
total monomer concentration and also with decreases in the total
stabiliser concentration. Increases in the particle size could also be
achieved by increasing the proportion of the total monomer in the seed
stage of the twin stage reaction and also by decreasing the proportion
of the total stabiliser in the seed stage. The importance of the role of
the seed upon the final particle size was firmly established. The rheology of these non aqueous dispersions was studied over a
range of concentrations and under increasing shear stresses. At Iow
and intennediate volume fractions the dispersions were observed to be
predominantly Newtonian. Non-Newtonian behaviour was only
observed at the extremes of the shear stress ranges studied. At high
volume fractions of the dispersions non-Newtonian behaviour was
observed over the range of shear stresses studied.
Maximum volume fractions (~m) were calculated for these dispersions
using the Kreiger-Dougherty equation. When these dispersions were
blended in size ratios of 2: 1 it was observed that 4>m could be increased
due to improved particle packing efficiency.
History
School
- Science
Department
- Chemistry
Publisher
© Matthew John SavagePublication date
1998Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.Language
- en