Wanted: smart answers for the composites industry

Silicone resins have a low fire load, can interact with fillers and fibers and can form ceramic materials. Silicone resins protect material integrity during a fire. Fiber-reinforced silicone resins develop low thermal conductivity when heated by a flame (large temperature difference between the hot and cold side).

In composite materials for battery enclosures or heat shields, silicone resins play a major role in protecting batteries from thermal runaway, significantly improving the ability of fiber-reinforced composites to resist heat and flames.

The use of silicone resins as binders enables the production of heavy-duty composite materials for applications in electrical engineering and design. Thanks to their silicone-resin component, these materials can withstand ongoing extreme temperatures, yet retain their electrical and water-repellent properties, as well as their outstanding mechanical strength.

Treating fillers and additives with GENIOSIL^® silanes and with WACKER^® fluids and emulsions hydrophobizes their surfaces, thereby reducing interactions between powder particles.

HDK^® pyrogenic silica significantly improves powder flowability by reducing interactions between powder particles. HDK^® does not penetrate the surface of the powder particles, which keeps powders flowing freely, even over long storage periods.

Using GENIOSIL^® silanes or WACKER^® fluids and emulsions to hydrophobize mineral fillers or pigments can reduce the mixing time and energy involved in working these into a polymer matrix. One benefit of hydrophobization lies in making fillers easier to incorporate and distribute more evenly. It also reduces the increase in viscosity during the mixing process, which reduces the risk of thermal degradation and opens the door to higher filler content.

When fillers or pigments are incorporated into a polymer matrix, they remain separate at the microscopic level. The use of functional silanes can produce chemical bonds between the polymer and the filler, thereby improving their interactions and compatibility. GENIOSIL^® organofunctional silanes are available with various functional groups. Silanes with amino, epoxy, methacryloxy and vinyl groups are especially important when it comes to the reaction with different thermoset resins.

Fiber sizing – a critical step in the process of manufacturing glass fibers – involves coating freshly extruded fibers with an aqueous emulsion in order to give the fibers suitable processing properties and to optimize composite performance. GENIOSIL^® organofunctional silanes are key components in the sizing formulation. They act as coupling agents between the fiber and matrix in glass-fiber-reinforced composites.

In order to improve adhesion between the matrix and the glass fiber and/or fillers, organofunctional silanes are available with different functional groups allowing them to react with a variety of thermoset resins. Particularly important examples here are those having amino, epoxy, methacryloxy and vinyl groups.

Treating mineral-based fillers or pigments with alkylated GENIOSIL^® silanes or with WACKER^® fluids and emulsions hydrophobizes their surfaces, allowing them to repel water.

GENIOSIL^® organofunctional silanes can bind organic polymers to inorganic materials such as glass, metal, ceramic and countless fillers. These bifunctional molecules act as adhesion promoters, because they combine the functionality of a reactive organic group with the inorganic functionality of an alkoxysilane in a single molecule.

The use of reusable vacuum bags made from silicone rubber helps reduce the waste produced by disposable items such as films and adhesive tape.

Unlike the time-consuming process of sealing each composite part with vacuum film and adhesive tape, the use of a reusable vacuum bag results in process reliability, short production cycles and less work.

Room-temperature-vulcanizing silicone rubber is an ideal material for producing inflatable bellows and balloons, spacers and pressure pieces. The elasticity of the material and its favorable release properties make parts easy to demold following resin injection or composite production. Its outstanding mechanical properties make silicone rubber spacers and bellows reusable.

ELASTOSIL^® C 1200 can be either sprayed or brushed onto surfaces. The material is thixotropic, making it suitable for work on sloped and vertical surfaces. This property can be increased through the use of additives.

Using SILRES^® BS 7070 opens up the world of exterior applications to manufacturers of engineered stones. The UV resistance of products based on SILRES^® BS 7070 is outstanding. Its application changes none of the typical advantages of engineered stones, such as unlimited design freedom and mechanical durability.

Use of a GENIOSIL^® silane results in a chemical bond between an organic resin and the inorganic mineral. This significantly improves the mechanical strength of engineered stone slabs, making them much easier to process during manufacturing (e.g., for polishing and cutting).

Manufacturers can achieve 0% linear shrinkage by using VINNAPAS^® low-profile additives – especially carboxylated products such as VINNAPAS^® C 501. If desired, these products can even result in expansion in sheet molding compounds (SMCs) and bulk molding compounds (BMCs).

The surface quality is excellent, and the process is simple and economical. Class A quality – a requirement of the automotive industry – is achievable, depending on the overall formulation.

Efficient shrink control dissipates stress within the component, thereby preventing cracks, even for very fast processes and short cycle times.

Static mechanical properties such as the flexural modulus of elasticity remain high despite the use of thermoplastic VINNAPAS^® additives. This makes it quite easy to achieve values of 13,000 MPa for the modulus of elasticity in typical commercial Class A SMC formulations.

VINNAPAS^® low-profile additives (LPAs) effectively reduce the considerable shrinkage that occurs with the unsaturated polyester (UP) and vinyl ester (VE) resins most often used in the pultrusion process. Their use dissipates stress within the profiles and improves the ability of the matrix resin to bind to the fibers.

Production of fiber-reinforced profiles yields fewer cracks, lower rejection rates and improved fatigue resistance. In addition, the LPA effect also produces a homogeneous, intensely white color during curing. The result is better fiber coverage, allowing manufacturers to reduce or even eliminate the use of expensive white pigments in their formulations.

Our new VINNEX^® RT 50 and VINNEX^® RT 200 room-temperature LPAs achieve 0% volume shrinkage in suitable UP and VE resins. These LPA additives also retain their functionality in the event of only slight temperature spikes.

This makes it possible to manufacturer components in which fibers leave much less of an imprint on the component surface. In more reactive UP and VE resins, VINNAPAS^® B resins can at times yield excellent results as well. Nevertheless, detailed optimization work will need to be carried out in any given resin system. Our LPA laboratory in Burghausen will be glad to support you in these efforts.