The molding process of liquid silicone rubber is its core competitiveness that distinguishes it from all traditional rubber materials. It does not require tedious manual processes such as rubber mixing, cutting, and material placement. The entire production process is completely replaced by machines, and one worker only needs to take away the finished product - this is the efficiency revolution brought by liquid injection molding (LIM) technology.

It all starts with the precise mixing of two components. Liquid silicone rubber is usually composed of a base rubber (polymethyl vinyl siloxane raw rubber) and a crosslinking agent (polymethyl hydrogen siloxane), catalyzed by transition metal complexes such as platinum, nickel, rhodium, etc. A. The two components B are uniformly mixed in a 1:1 weight ratio through a static mixer, and then transported to the mold through a cold runner system. The role of the cold runner system is crucial - it controls the temperature of the mixed adhesive at a lower level to delay curing and avoid waste caused by premature cross-linking of the adhesive in the runner. At present, advanced cold runner systems are divided into two types: closed systems and open systems. The former uses switch pins or needle valves to control flow, while the latter uses contraction nozzles and valve channels to control flow, both of which can achieve efficient molding without burrs and waste.

In the injection stage, the rubber material is injected into the mold at a temperature of 120 ℃ to 180 ℃ and a pressure of 50 to 150MPa, and vulcanization and curing can be completed within a few seconds. Compared with traditional high temperature vulcanization (HCR) process, LIM process can save about 40% of comprehensive costs, save manpower, electricity, materials, and has extremely high product consistency. For liquid silicone rubber used in special power applications, the national standard specifies its technical requirements: the viscosity of component A and component B shall not exceed 1000Pa · s, the tensile strength shall not be less than 5MPa, the elongation at break shall not be less than 300%, the volume resistivity shall not be less than 1.0 × 10 ¹⁴Ω· cm, and the electrical strength shall not be less than 20kV/m. These stringent indicators ensure its reliability in composite insulation products.

If it is room temperature vulcanized liquid silicone rubber (RTV), the process is more flexible. The mixed adhesive material can be directly poured or coated, and gradually cured in the atmosphere or under heating conditions. When used for mold manufacturing, the injection or brushing process is usually adopted: first, release agent is applied to the prototype, then silicone is coated, and after 30 minutes, a layer of gauze fiber cloth is pasted to enhance strength and tension, followed by a layer of silicone and another layer of gauze. Repeat this process twice, and the service life and flipping times of the silicone mold can be greatly improved. The curing time can be flexibly controlled by adjusting the curing agent ratio between 10 minutes and several hours - when the curing agent dosage is 1%, it takes about 6 to 8 hours to demold, and when the dosage is 4%, it only takes 1 to 1.5 hours to demold.

It is worth noting that liquid silicone rubber has strict taboos in use. It must avoid contact with organic compounds such as amines, phosphorus, sulfur, nitriles, and organotin, otherwise it may cause abnormal curing or even complete non curing. Therefore, a resistance capacitance test must be conducted on the silicone rubber and substrate before use. When stored, it should be sealed and stored in an environment between 0 and 30 ℃. The shelf life is generally 12 months. Components A and B must not be mixed and stored in advance, otherwise they will be directly scrapped.

Regarding liquid silicone rubber, please refer to our website for details: IOTA Liquid Silicone Rubber