Latexes film formation ability

It was observed that intermediate compositions dried slower than the unblended constituents. The mechanical properties of latex blends comprising low and high particles, the film formation ability, and the comparison of results to classical theory of polymer blends containing hard particles have been reported by Lepizzera et al. [1997], This is one of the few studies in the literature that has attempted to correlate emulsion blend properties with empirical/theoretical relationships previously available in the open literature. 

After polymerisation is completed, some additives may be required to enhance the performance or stabihty properties of the final latex product (62). It may be necessary to modify the viscosity of the latex, improve film formation ability, or protect the latex from biological or oxidative degradation. 

The copolymer composition of the latex is critical since it affects the physical and chemical properties of the end-use product, especially the glass transition temperature (Tg). By varying the copolymer composition (and as a result the glass transition temperature), the film formation ability, tackiness, and film strength of the copolymer may be controlled and tailored to meet certain specifications. The glass... 

The monomer composition must be chosen carefully as it will affect the properties of the final coating and the film-forming ability of the latex. The minimum film-forming temperature (MEET) is defined as the lowest temperature at which the latex particles will coalesce to give a clear film. It is related to the glass transition temperature (Tg) of the polymer but is also influenced by the presence of other materials such as coalescing solvents, plasticizers, and surfactants. In order that the latex particles can coalesce and form a continuous film on application, the MEET must be below the temperature at which film formation will occur. For domestic paints an MEET of below 10°C is required. 

The effect of the Tg of the latex on the film-formation behaviour of a series of 2-ethylhexyl acrylate/methyl methacrylate emulsion copolymers was studied. Stage 1 of fihn formation was examined using a combination of DMA and conductivity measurements. Stages 2 and 3 were investigated using calorimehic compensation, DSC, dielectric spectroscopy and atomic force microscopy. Comparison of the results from the different methods employed led to a detailed model of the film-formation process in which the temp, used relative to the minimum film-formation temp, determined the effectiveness of the processes. The relative usefulness of the techniques used in their ability to characterise the various stages in the film-formation process was assessed for these copolymer systans. 23 refs. 

In the same year, Fulda and Tieke [75] reported on Langmuir films of monodisperse, 0.5-pm spherical polymer particles with hydrophobic polystyrene cores and hydrophilic shells containing polyacrylic acid or polyacrylamide. Measurement of ir-A curves and scanning electron microscopy (SEM) were used to determine the structure of the monolayers. In subsequent work, Fulda et al. [76] studied a variety of particles with different hydrophilic shells for their ability to form Langmuir films. Fulda and Tieke [77] investigated the influence of subphase conditions (pH, ionic strength) on monolayer formation of cationic and anionic particles as well as the structure of films made from bidisperse mixtures of anionic latex particles. 

SWCNT/PMA composites were prepared using two processing techniques. For one series, the latex-based route was strictly followed. For the second series of composites, the two-component SWCNT - latex colloidal mixture was allowed to slowly dry at room temperature. The ability of the latex to flow once the aqueous phase is removed, allowed the formation of a homogenous film. Table 4.4 lists the preparation techniques utilized. 

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