What additives are added to liquid silicone rubber?
Liquid silicone rubber is based on medium-polymerized linear polyorganosiloxane as the fundamental polymer, combined with fillers, various additives, and adjuvants to form a base material with self-leveling or thixotropic properties. To enhance its performance or achieve specific functions, a variety of additives are typically included. Below is a summary of common additives in liquid silicone rubber:
1. Basic Additives
Crosslinking agents: Essential components of liquid silicone rubber that enable crosslinking reactions, leading to the formation of an elastomer.
Catalysts: Used to accelerate the curing reaction of liquid silicone rubber, improving production efficiency.
2. Performance Modifiers
Thickening agents: Such as hydroxypropyl methylcellulose (HPMC), Carbopol series (Carbomer), and xanthan gum, used to adjust the viscosity of liquid silicone rubber, making it easier to process and apply.
Surfactants: Examples include sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), and octylphenol ethoxylate (Triton X-100), which improve surface properties like wetting and dispersibility.
Stabilizers: Such as magnesium sulfate, emulsifiers, antioxidants, and desiccants, to enhance the stability of liquid silicone rubber, preventing degradation or spoilage during storage and use.
3. Functional Additives
Preservatives: Examples include parabens, methylisothiazolinone (MIT), and isothiazolinone (IPH), to protect liquid silicone rubber from microbial contamination and degradation.
Dispersants: Such as polyvinylpyrrolidone (PVP) and glycerol monostearate, which help disperse solid materials uniformly in the liquid silicone rubber, preventing aggregation and sedimentation.
Heat-resistant agents: To improve the heat resistance of liquid silicone rubber, ensuring stable performance in high-temperature environments.
Flame retardants: To enhance the flame resistance of liquid silicone rubber, reducing its flammability or the spread of fire.
4. Other Additives
Reinforcing fillers: Examples include nano-silica and nano-calcium carbonate, used to improve the mechanical properties of liquid silicone rubber, such as hardness and tensile strength.
Pigments: Added to provide specific colors, meeting various aesthetic requirements.
Inhibitors: Used to regulate the curing speed of liquid silicone rubber, preventing excessively fast or slow curing that could compromise performance.