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Dispersion

Polymer-Filler

Plastics are an irreplaceable part of our everyday lives and yet their proliferation has been enabled, to a large extent by additives. Additives for plastics provide better long term stability, anti-static properties, color and better mechanical properties. Fillers in particular are useful tools for tuning plastics so that their property profile fits the unique needs of a given application. Although fillers are very beneficial to the performance of plastics, they do bring some disadvantages and that is where dispersants and coupling agents come in. By judicious use of the appropriate dispersant or coupling agent, one can maximize properties and minimize drawbacks to create materials with an optimal balance of performance and cost.

Dispersants graph

A well-designed dispersant bonds strongly to the filler particles and forms a barrier that prevents adjacent particles from approaching closely and sticking together. The criteria for effective stabilizer are:

  • Must bond well to the filler and not be displaced at high temperatures or under high shear force
  • Must be of sufficiently high molecular weight to form a thick enough barrier to prevent close particle approach
  • Should be compatible with, i.e. soluble in, the polymer phase so that it expands to form a thick layer around each particle

Cray Valley’s experts have the technology available to tune each of these three factors in order to deliver optimized performance.

Optimization of interfaces is the key to good polymer composites and blends. Addition of just one or two percent modifier can dramatically improve processability, mechanical properties and aesthetics. Effective modifiers are additives that are able to compatibilize two different materials, for example a filler and a polymer or a blend of two polymers. Normally, different materials have poor compatibility, leading to problems with dispersion, void formation and adhesion. An effective modifier is able to act as a mediator which imparts compatibility and thereby boosts properties. In order to fulfill that role, the interfacial modifier has to first get to the interface and once there, to form a bridge between the two dissimilar materials.

  • The additive has to get to the interface which requires control of the molecular weight
  • The additive must have chemistry that allows it to interact with both surfaces present at the interface, thus the chemistry needs to be tunable to suit different fillers and polymers

Although there are effective modifiers available on the market, they have serious limitations. Firstly, the chemistries are limited, so they may not be effective in your formulation. Secondly, there is little to no control of molecular weight so the additives may not be able to reach the interface in time, for example during an extrusion process. Lastly, the products tend to be standard offerings that are designed to have acceptable performance in a wide range of formulations which means they do not show outstanding performance in any.

Dispersants chart

Cray Valley takes a very different approach. By offering a wide range of chemistries, it is possible to select additives that match the needs of your material. Close control over molecular weight means that the modifier can be tailored to ensure the additive can reach the interface to do its job. Lastly, Cray Valley has the expertise to create new products to meet your needs. This means you can get better performance but also that you can get an edge over your competitors who are likely to be using a standard, off-the-shelf solution.

Inks & Coatings

SMA resins and esters have been successfully used in aqueous pigment dispersions for coatings and inks for many years. These unique polymeric surfactants are capable of dispersing a wide range of both organic and inorganic pigments. SMA resins and esters yield maximum color strength, and provide dispersions with excellent viscosity stability. Plus, SMA based dispersions are very compatible with many types of emulsions and base paints to ensure a homogeneous color. In addition, SMA resins and esters promote high gloss, excellent water resistance and scrub resistant properties on the final paint film.

Colloidal Agents

Cray Valley HSC's additives, especially the Styrene-Maleic Anhydride (SMA®) copolymers, incorporate both hydrophobic and hydrophilic groups in close proximity. Hydrolyzed in water as the acid salt, SMA resins form micelle-like structures which can be utilized to impart higher heat resistance to emulsion polymers for graphic arts markets. Depending on the desired properties, the SMA salt can be formed by solubilizing with bases like Ammonia, Sodium Hydroxide or Potassium Hydroxide.