HTV high-temperature vulcanized silicone rubber is a type of organosilicon product known for its excellent properties such as high and low temperature resistance, UV resistance, radiation resistance, weather resistance, electrical insulation, high breathability, physiological inertness, low compression set, and fatigue resistance. As a result, HTV high-temperature vulcanized silicone rubber finds wide applications in aerospace, electronics, light industry, machinery, construction, chemical, medical, and daily-use industries. In this article, we will delve into the three common molding processes for high-temperature vulcanized silicone rubber.
1. Compression Molding:
Compression molding, also known as hot pressing, involves placing pre-mixed silicone rubber compound with additives (such as double five or double four silicone rubber vulcanizing agents) into a high-temperature mold. The mixture is then subjected to pressure using a hot press machine, resulting in high-temperature vulcanization and molding.
Compression molding is a production process used for solid silicone rubber. It involves combining upper and lower mold plates with a mold core in between, hence the name "compression molded silicone rubber." The main process involves heating and pressurizing the silicone rubber raw materials within the closed mold cavity to form the desired products. Typically, the raw materials are mixed uniformly in a kneader to create a compound, which is then transferred into a vulcanization molding machine. The mold is closed, pressure is applied, and the rubber is shaped and cured before demolding. This process is suitable for thermosetting materials.
2. Extrusion Molding:
Extrusion molding is akin to squeezing toothpaste from a tube. The extrusion head determines the cross-sectional shape of the product, which is continuously vulcanized and shaped as it exits the extrusion head due to the application of temperature and pressure. Extrusion molding primarily produces products with a bar-like shape, with various cross-sectional profiles such as rectangular bars or circular silicone tubes.
Extruded silicone rubber products are typically produced by extrusion machines. This continuous molding process utilizes the interaction between the rotating screw within the silicone rubber extruder and the silicone rubber to produce various semi-finished products of different shapes. It is suitable for processing solid-state silicone rubber with double-four or platinum-based vulcanizing agents. Extrusion molding is commonly used to produce silicone rubber tubes, insulating sleeves for wires and cables, and other silicone rubber products.
3. Injection Molding:
Injection molding requires specific equipment such as silicone rubber injection machines and feeders. The raw material is a two-component liquid mixture with a viscous consistency. The process involves using a feeder to evenly mix and feed components A and B in a 1:1 ratio into the injection machine's barrel. The mixture is then thoroughly blended using a static mixer, injected into the injection barrel, and molded. This molding process operates at relatively low temperatures, typically around 130 degrees Celsius. Injection molding is suitable for plastic encapsulation molding that does not require high-temperature resistance, providing an advantage over solid-state compression molding.
Liquid silicone rubber injection machines are widely used in various fields, including medicine, food, silicone nipples, baby products, diving equipment, electrical insulation components, and cable accessories.
The above three processes are commonly used for molding HTV high-temperature vulcanized silicone rubber.