How to Choose the Right Silicone Emulsion for Your Production Process?

Core Properties of Silicones Emulsions

Silicone Emulsions’ Viscosity and Particle Size

Viscosity primarily determines the flow of the material. In a comparative study with low viscosity silicone emulsions, as prescribed by ISO 3219, they demonstrated good performance in operations such as spraying and pumping. The lower viscosity variants used approximately 15% less energy than the higher viscosity variants. Thestability of cement and coatings emulsions crashing particle size in the range of 0.1 to 5 micron is of significant interest. Small particles exhibit short shelf life, despite the increased difficulty of production. Long term stability does require a lab to investigate the emulsifier and the system’s response to the agitations of the stores temperature. The separation of the system during long term storage is the most undesirable. If a product is to be shelf stable for a twelve-month period, the system must remain homogeneous at a pH range of 3 to 11 and a temperature range of also 5 to 50 degrees Celsius. According to the ASTM D2196 standard, these conditions must also be met in order to qualify for testing.

Influence of Solid Content and Emulsifier Type on Compatibility with Substrates and Film Quality

Solid content (30–60%) influences both the thickness of the film and the rate of curing with the substrate: higher solid content leads to faster film formation but can reduce flexibility; lower solid content improves film formation on porous substrates including textiles. The chemistry of the emulsifier affects the bond at the interface:

- Non-ionic emulsifiers are compatible with both cotton and polyester, as well as their blends.
- Cationic emulsifiers improve bonding to metal and rubber substrates.
- Anionic emulsifiers are preferable in high-shear, low-foam conditions.

The presence of multiple emulsifiers can lead to water repellency loss of up to 40% due to coalescence. An optimal system is one in which the hydrolytic stability is balanced with low surface tension (≈22 mN/m) to encourage coating and uniform wetting.

Silicone Emulsion Selection by Industry Application

Textiles and Leather: Softness vs. Water/Oil Repellency vs. Process Compatibility

Textiles need silicone emulsions that help soften and make the fabric more pliable without compromising the fabric's strength or dye uptake. Technical outerwear and upholstery have more challenging requirements. Durable water repellency (DWR) and good oil resistance are crucial. Silicone emulsions operate in water dye baths and survive low temp curing under 100 °C to avoid yellowing and finishing issues. Leather processing involves ensuring treatment penetrates and maintains suppleness while the hide's surface resists abrasion and is water repellent to withstand the demands of leather good's use.

Rubber, Plastic, and Metal Molding: Heat Resistance, Release Efficiency, and Inertness Above 150 Degrees Celsius

To achieve optimal performance at 150°C and beyond, we need high thermal stability emulsions that will remain effective and versatile during the high temperature molding operations. Top-tier products reduce residue build up on the surfaces of the tooling, which translates to a reduction in the number of parts that will be rejected in the injection molding process. Some information suggests that this can result in a reduction of about 20 to 25 % in rejection rates. With regards to thermal resistance, we require that the materials endure a number of heating cycles without decomposition or the emission of toxic gases. One of the major concerns is the necessity to prevent an emulsion from exacerbating the oxidation of some plastics, such as polypropylene, or causing aluminum molds to corrode. This is the reason we look for materials that possess true stability in the presence of hot substances. It is well-known that emulsions with smaller particles provide not only easy release from the mold, but also a better surface finish on the molded components.

Handling and Integrating Silicone Emulsion

Dilution and Mixing: The Science Behind Coalescence

A few factors can affect colloidal integrity when diluting; the direction of water and emulsion introduction, the stirring speed (should be < 1500 rpm), and the mixing temperature (should be between 15 and 30 degrees Celsius). Mixing out of this temperature range can considerably increase the probability of emulsion separation and destabilization. Up to 40% of some laboratory studies indicated separation. Baffled tanks with slow rotating impellers are the best equipment. This minimizes excessive shear, resulting in a damages across structural emulsion layers. Note that the additional components (surfactants / additives) must be pre-diluted to avoid hotspots and localized breakdown.

Stable silicone emulsions should be compatible with the following systems, pumps, nozzles, and storage.

Pumps should minimize shear degradation and can include diaphragm or peristaltic options. Openings of the nozzles should also be large. A general guideline is to have the orifice diameter at least 1.5 times larger than the biggest particle in the mix. For particle sizes in most applications between 0.5 and 5 µm, options larger than 0.75 µm should be selected. Storage should be done at room temperature, ideally between 20 and 25 degrees Celsius. Above 35 °C storage can decrease effectiveness rapidly, with studies showing a 60% shelf life loss in just 8 weeks. For a better tank design, conical bottom tanks used with sweep arms will keep the sediment from settling unevenly and will help get the most out of the tank during a discharge effort. Construction materials also play a role, storage should employ 316L stainless steel or HDPE, and incorporate an inert gas cover to reduce oxidation. Carbon steel should be avoided as, systems using it, will have accelerated oxidation.

Assessing Performance Characteristics of Silicone Emulsions in Technical Data Sheets

Data sheets are usually reviewed so technical product specifications can be confirmed. In your review concentrate first on viscosity range and particle distribution. These parameters affect pumpability, sprayability, sedimentation and emulsion stability. Evaluate your application requirements against solid content. Incorrect selection often results to undesired adhesion and film coverage. For applications involving high temperatures, as in metal or rubber molding, check that the product can withstand temperatures high of 150 degrees Celsius. Evaluate against the requirements of recognized test results. Manufacturer claims are usually biased. Compare pH and chemical resistance with the production line chemicals to avoid leaks. Request batch consistency reports and safe handling guidelines. Lack of these details means the company has low quality control systems.

FAQ Section

What benefits do low viscosity silicone emulsions provide?

Low viscosity silicone emulsions are beneficial for spray and pumping applications, offering energy savings of about 15% compared to high viscosity emulsions.

I would like to know how different silicone types determine how silicone emulsions interact.

Why is there a variety of emulsifiers?
The type of emulsifier chosen will determine which substrate the emulsifier will work with, and how the emulsifier will form a film. Depending on the type of emulsifier (non-ionic, cationic, anionic), there are free-flowing properties that lend themselves to different uses.

What determines how long silicone emulsions will consist of a homogeneous formulation with a stable pH, and be kept at a temperature between 5°C to 50°C?

What silicone emulsions can be used at high temperatures without compromising the performance of the products? For high temperature molding processes, an emulsion that is heat resistant and chemically stable to 150°C is to be preferred. The amount of residue and rejection can also occur during the process, especially more so with non-heat resistant emulsions.