Mixing Polymers in Industrial Tote Mixers

Polymers come in a wide variety of forms and concentrations, from dry powders to liquid emulsions. Mixing Polymers with EvenMix can be a challenge and requires specialized equipment that can handle high energy mixing with a wide range of viscosities. From industrial totes mixing chemicals to chemical mixers for water treatment, Dynamix offers a full line of tote mixers that are specially sized to work with the unique features of these materials.

The most common use of polymer blends is to combine the good properties of two different polymers in a single formulation. These benefits include lower costs, improved processing performance and a better balance of mechanical properties. For example, ABS/SMA blends provide outstanding processability and low warpage with high heat deflection temperature and impact strength.

Mixing a polymer blend requires careful consideration of both the physical and thermodynamic properties of the components. The mixtures must be miscible and free of coalescence, a condition that can be achieved only with proper selection of both the component polymers and the blending conditions. In addition, the mixing entropy must be minimized to prevent resegregation of the polymer phases and ensure that the composition is stable in storage.

These factors can be modeled using a lattice model of the polymer molecular structure and a thermodynamic free energy curve for the blend. For example, the figure below shows a comparison of experimental and theoretical data for the LCST mixture PS/PVME and a very miscible blend of PS with poly(phenylene oxide)-poly(phenylene sulphide) (PPO). The lattice model accurately predicts both the exothermic nature of the mixing and the existence of the double minimum seen in the experimental curves.

A key to achieving an effective, long-lasting mix is to incorporate a surfactant at the interface. This is known as compatibilizing the polymer, and it significantly reduces interfacial tension between the components of a blend and improves their mechanical properties. This is because the large molecular size of the polymer molecules makes them less attractive to the smaller molecules in the solvent, so they tend to stay farther apart at the interface.

Compatibilizers also decrease the particle size of the minor phase in an immiscible blend, making it more stable. Small particles have more surface area than larger ones, so they will contact each other more readily and cause coalescence. This is why rheology is such an important tool to monitor the evolution of particle size in a polymer blend under defined flow conditions and mixing energy input. It is the information gained from this that can help to control the formation of phase-separated droplets and avoid premature coalescence in a polymer blend. It can also be used to optimize the formulation of a mximum particle size for optimum mechanical properties in the final product.