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The slow increase in use of latex paints in the industrial
sector is due to problems related to improper film formation,
poor rheology and badly dispersed pigment compared to solvent
based coatings. The result is high permeability to water and
gasses as well as poor gloss leading to poor resistance to
atmospheric and chemical attack, and poor aesthetic properties.
This project aimed to determine the main factors causing poor
film formation, rheology and pigment distribution with the aim of
producing guidelines to aid the formulation of high performance
latex paints.
A mathematical model allowing the a priori calculation of the
lowering of glass transition temperature by added cosolvent has
been developed. A thermodynamically derived relationship to allow
the calculation of partition coefficients of coalescing agents
between the aqueous phase and the latex particles was produced.
It is based on the chemical potential theory and makes use of the
recent Mobile Order Theory developed by Huyskens. A model to
calculate the correct polymer viscoelastic properties to ensure
full sintering is also included. The model incorporates the
effect particle size, drying conditions (temperature, relative
humidity, air velocity etc) and the mechanical properties of the
polymer.
A computer program was developed to simulate the packing of
pigment and latex particles. Up to 3 different types of particles
can be used with different size distributions and surface
potentials. A version of the program is available to sponsors.
From the results and models produced, guidelines were
presented for formulation of high performance latex paints.
Further Information
If you are interested in this, or any other project, please contact Richard Holman.
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