Silicone resins are polymers with a three-dimensional branched-chain structure and a low molecular weight. Their various qualities, including great thermal stability, make them ideal for use as binders in paints, varnishes, and impregnating materials.
Molecular structure
The amount of tri-functional T groups or, in some cases, quadri-functional Q groups injected into the polymer during production determines the structure of the resin. The type of non-reactive and reactive groups attached to the silicon atoms is also important.
The characteristics of the resin are also influenced by two of the most common types of non-reactive groups found in the siloxane chain: methyl groups impart water repellency, release properties, and surface hardness, whereas phenyl groups impart temperature and weathering resistance, especially by UV-radiation, flexibility at high temperatures, and compatibility with organic products.
The resin can crosslink thanks to three different types of reactive groups.
The most prevalent type is hydroxy groups. They allow crosslinking to occur at ambient temperature via a condensation reaction in the presence of a catalyst or alkaline system. The cure rate is often accelerated by the use of a catalyst and higher temperatures, notably in the case of methyl phenyl resins.
At room temperature and in the presence of humidity, alkoxy groups hydrolyze to form hydroxy groups. Curing then takes place in the same manner as before. When kept, these resins are more stable.
Vinyl groups react by an addition reaction in the presence of platinum at moderate temperatures, as in RTV (Room Temperature Vulcanisation), or at high temperatures in the presence of peroxides, as in HCR (Heat-Cure Rust).
To lower viscosity, resins are usually diluted in aliphatic or aromatic solvents, emulsified in water, or diluted in silicone polymers.
Properties of silicone resin
Resins generate flexible or rigid, thermoset or thermoplastic films that bestow extraordinary qualities to the treated surfaces after drying and crosslinking. Their heat stability is exceptional: resins protect effectively at continuous temperatures of up to 250°C and can tolerate short-term exposure to peak temperatures of up to 500°C. They have outstanding dielectric qualities and resist oxidation at temperatures up to 250°C, making them ideal for use in high-performance electrical insulation products. They're also water-repellent and have good releasing properties.
What are the benefits of silicone resins?
Let's have a look at how resins are employed in the industry. The majority of silicone resins that leave a silicone production facility are first developed. Our customers use our methyl silicone resins (MQ type) to develop release agent products for a variety of thermoplastic, thermosetting, or elastomeric substances such as PU. Release agent formulators have a large choice of resins to choose from, giving them more options and flexibility in their formulation.
These methyl silicone resins (MQ) have several benefits:
- odorless
- Very simple to use
- Excellent adhesion to the mold's surface
- The molded product has a high-quality surface finish.
- Thermal stability is excellent.
- Mold fouling is reduced.
- Cleaning is simple.
Applications that are related
Silicone resins are widely used in the paint industry as binders to improve the heat resistance of paints and renderings. They're also mixed with organic resins to make polyester-silicone resin blends that are good for continuous pre-coating or "coil coating" procedures. Electrical impregnating and insulating applications also use silicone resins: They provide superior weather and high-temperature protection. The use of so-called MQ-type resins in industrial release and mold release applications, where silicone oils are frequently utilized, extends the mold-release agent's longevity. Permanent, non-stick coatings that survive high temperatures for culinary applications are made with methyl phenyl silicones. In the water-repellent treatment of construction materials, facades, and the consolidation of ancient monuments, special silicone resins are used. A very thin layer of "resin compound" is placed onto the substrate during the release coating of paper and films. In actuality, these complex chemicals contain reactive oils, crosslinkers, and a catalyst that cure to form a resin-like structure in the coating.