Dispersants

How are particle dispersions stabilised?

1. Prevent coagulation through inter-particle repulsion (colloidal stability)
2. Slow down sedimentation by increasing viscosity of continuous phase (kinetic stability)
3. Make it solid by creating a network structure (thermodynamic stability).

The main method by which our products work is through method a) – colloidal stability, but we also have products that work by adjusting kinetic and thermodynamic stability. If you need a dispersant for a particular application not listed here, please contact us.

Colloidal stability 

To maintain stability through Brownian motion, we must prevent particles sticking together when they collide.

• This can be achieved by increasing the charge associated with the particle (i.e. Zeta potential).
• Zeta potential is a physical property which is exhibited by any particle in suspension.
• It can be used to optimise the formulations of suspensions and emulsions.
• The understanding of the zeta potential of a system enables a chemist to produce better and more stable formulations.
• There is an energy barrier resulting from combination of the attractive and repulsive forces prevents particles approaching each other closely.
• So long as the kinetic energy of a particle does not exceed this barrier, coagulation should not occur.
  

Figure 1: The energy of a system must exceed the energy barrier for agglomeration to occur. The energy barrier can be greater if Zeta potential between particles is maximised. 

Polymeric surfactants

Polymeric surfactants offer many performance advantages over conventional monomerics. They are a unique class of high-performance products that have been specially designed for stabilisation or co-stabilisation of aqueous and non-aqueous emulsions and dispersions. They are molecules featuring repeating hydrophilic and hydrophobic units. A wide variety of dispersed phase polarities can be formulated across a full range of formulations.

 

Polymeric surfactants impart excellent particle stability via steric stabilisation. The repulsive barriers of the polymer chains are better able to prevent coalescence and agglomeration than monomerics. In both aqueous and non-aqueous suspensions, the multiple anchoring points of polymeric surfactants provide superior interaction between surfactant and substrate. Combined with steric stabilisation, this results in highly robust and stable formulations. Polymeric surfactants are therefore able to stabilise even highly loaded suspensions and still maintain viscosity at an acceptable level.

We have a wide range of polymeric surfactant technology. Our polymeric surfactant chemistries comprise of EO/PO block copolymers, acrylic/styrene copolymers, methacrylic copolymers, poly hydroxystearate derivatives and alkyd PEG resin derivatives.

The diverse range of particle types and sizes that need dispersing means that in order for us to make appropriate recommendations it is important to understand what is required in order to create a good dispersion.

The right solution will depend on many factors such as:

• Particle size / shape
• Particle density
• Surface charge of particle
• The solvent the particle is to be dispersed in
• Desired solids loading of dispersion
• The pH of the system (if aqueous)
• What kind of doping is present (often the case in certain applications).