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Production and performance of silicone rubber

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Solid silicone rubber is usually a single component adhesive, with crosslinking agents, catalysts, inhibitors mixed with the rubber material. Blended rubber is generally formed by high-temperature vulcanization after extrusion, unlike liquid rubber, which is mostly two-component and has three types: room temperature vulcanization, low-temperature vulcanization, and high-temperature vulcanization
1、 Production process:
After kneading with silicone rubber raw rubber, white carbon black, and other fillers in a kneading machine, cross-linking agents, catalysts, inhibitors, and various pigments are added to a two roll rubber mixer to obtain the mixture. The obtained rubber material is called silicone rubber compound.
2、 Physical properties/performance:
1. Before vulcanization (curing), it is "solid", and the color depends on the color added during mixing. If not added, it is white, with a plasticity value of around 200-300;
2. After vulcanization, the transparency without adding color is not as good as that of liquid adhesive, and the "transmittance" is not higher than 70%. The "rebound value" of mixed rubber with the same "hardness" is generally lower than that of liquid adhesive, but the "mechanical properties" are generally higher than that of liquid adhesive. The "tensile strength" reaches 10-20MPa, the "tear resistance" can reach 40-60KN/m, and the "elongation" is generally better than that of liquid adhesive with the same hardness. The "vulcanization temperature" is generally between 140 and 180 degrees.
3、 Chemical properties/properties:
Mixed rubber is a mixture of siloxanes, with molecules in a chain like spiral structure and an average molecular weight of approximately 400000-800000 mPa. s. Its viscosity is directly related to its molecular weight. The molecular weight can be measured using a Ubbelohde viscometer, which is roughly the so-called viscosity average molecular weight. The filler nanoscale SiO2 powder (precipitated SiO2 powder) is uniformly distributed in the raw rubber, forming a crystal like structure. The hydroxyl groups on the surface of SiO2 particles form hydrogen bonds with the Si-O bonds of the raw rubber. Each SiO2 particle serves as a core, extending hydrogen bonds in all directions to connect with the molecular chains of the raw rubber. Countless such structures, combined with other additives, form a high viscosity and high-performance mixed rubber.
Silicone rubber has excellent heat resistance, cold resistance, dielectric properties, ozone resistance, and atmospheric aging resistance. Its outstanding performance is that it can be used at a wide temperature range and can be used for a long time from -60 ℃ (or lower) to+250 ℃ (or higher). As for which property (quality) is superior, it is determined by the type of raw rubber, fillers, and additives used.


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