In the production of high-performance silicone rubber products, processing stability and batch-to-batch consistency are critical. As a key processing additive, hydroxyl-terminated phenyl methylsiloxane–dimethylsiloxane copolymers (IOTA Series structural control agents) have played an irreplaceable role for many years in silicone rubber compounding, extrusion, and molding processes, thanks to their well-controlled molecular structure and stable physicochemical properties.
This product is a colorless, transparent, oily liquid. Its main technical specifications include:
Viscosity at 25 °C: 500–20,000 mPa·s (customizable according to formulation requirements)
Density (25 °C): approximately 0.98 g/cm³
Appearance: clear and transparent, free of visible impurities
The polymer chains are terminated with reactive hydroxyl groups, while phenyl and methyl siloxane units are incorporated into the backbone, providing both chemical reactivity and a moderate steric hindrance effect. In high-temperature vulcanized (HTV) or liquid silicone rubber (LSR) systems, this copolymer effectively suppresses the “structuring” phenomenon caused by fillers such as fumed silica—namely, the hardening of rubber compounds and loss of plasticity during storage—thereby significantly improving processing flowability and storage stability.
In addition to its role as a structural control agent for silicone rubber, the product is also used for anti-blocking treatments of paper, films, and similar materials. By utilizing its low surface energy, it forms a temporary release layer and is suitable for applications with high cleanliness requirements, including food packaging, labels, and medical dressings.
Currently, the product is supplied in 200 kg plastic drums or steel–plastic composite drums and is transported as a non-hazardous material. It is recommended to store the product in a cool, dry, and well-ventilated area, kept tightly sealed and protected from contamination by acids, alkalis, or other impurities. The standard shelf life is 12 months.
According to feedback from multiple silicone rubber manufacturers, the use of this structural control agent results in a more gradual Mooney viscosity decay of compounded rubber, smoother extrusion surfaces, and minimal impact on the mechanical properties and transparency of the final products. “Especially in highly filled or high-transparency compounds, its performance is more stable than that of traditional low-molecular-weight hydroxyl silicone oils,” noted one technical manager.
With the rapid growth of high-end silicone rubber applications such as new-energy vehicle cables, medical catheters, and 5G communication seals, the demand for more refined and reliable processing additives continues to rise. As a mature and proven domestic solution, the IOTA Series structural control agents continue to provide solid support for quality improvement and efficiency enhancement across the silicone rubber industry chain.
Note: This product is a functional organosilicone intermediate that has been commercialized for many years. It is primarily used as a processing additive and anti-blocking agent for silicone rubber. It is not a consumer end product and should be used under professional guidance.
