Why is silica dispersant Better?

Author: Harry

May. 13, 2024

Agriculture

Why is Silica Dispersant Better?

According to Google search snippets, silica dispersants can significantly improve the dispersion of silica in various matrices, leading to enhanced stability, reduced viscosity, and improved mechanical properties. This makes them particularly beneficial in industrial applications, such as paints, coatings, and polymer composites.

Dispersants 101 - Why Use a Dispersant in Paints & Coatings

Dispersants provide a number of benefits for many different types of applications. They are specialized additives designed to wet, disperse, and stabilize solid particles in various continuous phases like solvents, water, and plastics. Their primary function is to reduce viscosity and increase the stability of a dispersion while enhancing the aesthetic properties of the final coating.

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How Dispersants Work

Solid particles like pigments, silica matting agents, waxes, and conductive particles are typically dispersed in a continuous phase (liquid or solid). By reducing viscosity, dispersants improve the workability of the dispersion and the productivity economics by increasing pigment loading and the rate of dispersion. This results in shipping advantages: more pigment in the dispersion reduces the amount of water, making it easier to handle and transport. Formulation flexibility is also enhanced, allowing dispersions to be added to a wide range of base finishes.

Dispersant Structure

A typical dispersant features a two-component structure: an anchoring group that strongly adsorbs onto the particle surface and a polymeric chain that provides stabilization. The anchor groups surround the particle, while the chains sterically stabilize it to prevent flocculation or gelation of particles in the dispersion.

Dispersant structures vary to achieve stability across different particles' surface natures and mediums such as water, solvent, UV monomers, and resins. The combination of anchoring group and polymeric chain determines the effectiveness of dispersants.

The Dispersion Process

The dispersion process involves three stages:

  1. Wetting of particles (pre-mixing)
  2. Separation of particles (mechanical means)
  3. Stabilization of particles (to overcome Van der Waals forces)

The first and third stages can be improved using effective dispersing/stabilizing agents, with the third stage being the most critical for system performance. This stage controls the final quality and stability of the dispersion system. Dispersants achieve stability via steric stabilization by adsorbing polymeric materials to particle surfaces, overcoming Van der Waals forces. Required properties for effective stabilization include:

  • Strong adsorption of stabilizing polymer to the particle surface
  • Optimum chain length (neither too long nor too short)
  • Good solubility in the dispersion medium
  • Compatibility with the resin post-evaporation of the solvent

Addition of Dispersants

Dispersants are usually pourable liquids, but they can also be waxy or granular solids. Ideally, they should be added before the mechanical process that breaks everything down, ensuring they are dissolved before adding the pigment. The dispersant should ideally be added during the mill base phase, where the main ingredients are resin and solvent or water. This ensures the dispersant is on the particle surface as mechanical means expose the surface, reducing viscosity and preventing particle agglomeration.

In some cases, dispersants can be post-added to improve stabilization or color at the end of the process—though these won't go through the original mill.

Improving the stability and quality of the dispersion also enhances coating quality. Reducing the average pigment particle size increases color strength, gloss, transparency, and brightness. However, without proper particle stability, these final performance enhancements can be reversed.

Lubrizol Hyperdispersants

Lubrizol hyperdispersants come in variations such as single-anchor, single-chain dispersants with lower molecular weight, or multiple-anchor "comb" structures for better stabilization. Choosing the right dispersant depends on the manufacturer's experience and knowledge. The dispersant must perform without negatively impacting properties like chemical resistance, surface softness, adhesion, or durability.

Lubrizol dispersants serve a vast range of needs across applications in paints & coatings, printing, packaging, plastics & composites, and electronics. Formulators globally use these dispersants to achieve high-quality outcomes.

New Silica Dispersion Improver for Fuel-efficient Tires

A comprehensive mixture of polymers, natural and synthetic rubber, and filler, tire rubber has traditionally used carbon black. Recently, silica has been incorporated to enhance fuel efficiency and wet grip simultaneously, making it a common filler in fuel-efficient tires.

The hydrophilic nature of silica complicates its blending with primarily lipophilic rubber. Uneven blending can result in increased friction and heat, negating fuel efficiency benefits. To address this, Kao and Bridgestone developed a new silica dispersion improver to enhance the affinity between rubber and silica. This agent allows uniform micro-dispersion of larger silica amounts in tire rubber, resulting in tires with advanced fuel efficiency and superior wet-grip performance. Made from 100% plant-derived ingredients, it also supports sustainable sourcing of raw materials.

This technology, used in Bridgestone’s Ecopia EX20 tire, has resulted in a 12% improvement in wet-braking performance without losing fuel efficiency. As this technology spreads, it will further contribute to sustainable automotive development.

Further reading:
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