The frequently used particle size methods established for the characterization of emulsion polymers are: Particle Size Consideration while Formulating Polymer Dispersion Some dispersions tend to form agglomerates, that can bias some methods, towards higher average particle sizes. The preparation of the dispersion before testing is often crucial. Often only a few characteristic numbers, such as theĪverage number or average weight are calculated, from the measured values to characterize the dispersion.Īs the polymer particles have a more or less extended interface layer, composed from adsorbed or grafted stabilizers, and electrolytes the “ dry” core diameter needs to be distinguished from a hydrodynamic diameter in the swollen, wet state. Also, the shape of the particles that are not necessarily ideal spheres and the particle morphology need to be considered. Most of the emulsion polymers exhibit broad or multi-disperse, often skewed distributions. A well-defined, narrow, mono-disperse particle size distribution is the exemption for the products to be discussed here. The results differ from the physical method used or even depending on the specific equipment provided. The real particle size of any given polymer dispersion is often difficult to attain. Commercial emulsion polymers contain between aboutĤ5 and 65% solids according to that method. The solid content is defined as the dry residue of all solid material after evaporation of water, containing polymer, stabilizer and organic or inorganic auxiliaries, divided by the total mass of the dispersion.
Some key factors for characterizing emulsion polymers are: These two properties, together with a pH, define the standard qualities of any commercial emulsion polymer. These milky-white liquids range from water-thin to thick paste-like in viscosity. They are commercially available as dispersion of polymer particles in water.
Therefore, emulsions polymers are amongst the fastest-growing categories of specialty chemicals in the world.Įmulsion Polymers are very versatile products. They found increasing interest over the past decades due to their favorable profile in terms of emission control. Waterborne systems are based on water – not organic solvent – as the main carrier. In other cases, the polymer emulsion is precipitated or spray-dried to form aįrom an application point of view, polymer emulsions are waterborne systems. This process results in a dispersion of about 50 – 60% solid polymer particles in the aqueous matrix.įor many applications, this dispersion is ready-to-use without further expensive separation and cleaning steps. With this mechanism, very high degrees of polymerization can be achieved at high-solids content, whilst the overall viscosity of the system stays within reasonable terms for processing. The monomer droplets just serve as a reservoir from which monomer molecules are delivered.