Thermoset composites are used in many different end markets and applications that need a strong, durable, lightweight material, increasingly replacing metal and traditional plastics as a result of their ability to resist corrosion and withstand aggressive elements, including certain chemicals, oils and harsh weather.

Thermoset composites are a mixture of a polymer matrix (thermoset resin) and a reinforcing fiber that, when combined, makes them stronger and leaves them in a permanent solid state after curing. Formulations can also contain pigments, fillers and flame retardants to introduce color, reduce weight and cost and provide fire retardancy.

Dispersing Particulate Matter

Dispersants are used in thermosets to help deliver some of the functional performance of composites while improving productivity and cost benefits. Effective dispersants do this by dispersing and stabilizing the solid particulate matter in the resin matrix in a homogenous distribution, which improves mechanical properties like tensile strength, hardness, material toughness, a better surface finish and more.

Dispersants lower the viscosity of compounds which allows an increase in filler and pigment loading and/or flame-retardant content. Processability of materials can be improved by enabling faster dispersion of particulates in the resin. Subsequent stabilization by the dispersant improves the stability of the thermoset by preventing particles from re-aggregating, which has benefits in, for example, color strength.

Additives for Additional Properties

Additional additives for composites can deliver other functions, such as styrene suppression, air release, rheological control and coupling.

In unsaturated polyester composites, styrene is used to improve mechanical properties. However, because styrene emissions are considered hazardous, it’s important to keep as much styrene locked into the formulation as possible. Styrene suppressants can help reduce styrene emissions that could occur from chemical reactions or during processing, which makes for safer handling by operators.

De-aeration or air release additives are designed for rapid air release and effective wetting in thermoset systems. When mixing high viscosity liquid resins and incorporating particulate solids, mechanical aggregation is used, which will incorporate air into the resins. If air is entrapped in the resin during curing, there will be voids in the formed article (bubbles in the composite or pinhole defects in the thermoset surface), which will lead to weakness in the final product. Air release agents are used to remove as much air from the formulation as possible which also reduces surface imperfections.

Solplus™ Hyperdispersant Technology

Thermosetting resin systems present unique challenges to dispersion producers and users of these materials. There exists a delicate balance between dispersion properties like color development and dispersion stability versus the need of the final formulated product to crosslink in the desired timeframe without significant impact from the dispersion. Solplus™ Hyperdispersants can help balance these properties. Whether the resin is an epoxy, unsaturated polyester, acrylic or polyaspartic, there is a Solplus™ Hyperdispersant designed to optimize performance.

The Solplus additives portfolio also includes Solplus™ F-Series air release agents, rheology control agents and styrene suppressants. Silicon-free, hazard label-free and low- or zero-VOC options are available, as well as FDA food contact grades.

Lubrizol can also customize our dispersant technology to meet exact customer needs, and we continue to develop new additives to expand our portfolio for thermoset composites, such as new styrene suppressants and coupling agents to bond the resin and the fiber or filler.

The Role of Dispersants and Additives in Thermoset Composites