HTV silicone rubber (high temperature vulcanized silicone rubber) is a silicone elastomer cross-linked by high temperature vulcanization. It has excellent temperature resistance (-100℃ to 350℃), aging resistance and electrical insulation. It is widely used in electronics, automobiles, medical and other fields. Its production process mainly includes raw material preparation, mixing, molding, vulcanization and post-processing.


1. Raw materials and formula design
The basic raw material of HTV silicone rubber is methyl vinyl silicone rubber (MVQ), supplemented by reinforcing agents (such as fumed silica), vulcanizing agents (such as peroxides), structure control agents (such as hydroxy silicone oils) and other functional additives (such as flame retardants, conductive fillers, etc.).


2. Mixing process
Mixing is a key step to evenly disperse the raw materials. It is usually carried out at low temperature (≤40℃) using an open mixer or internal mixer. When mixing, the roller distance (1-5mm) and speed ratio (1.2:1~1.4:1) need to be controlled, and the raw rubber, reinforcing agent, structure control agent, etc. need to be added in sequence. After 5 thin passes, the vulcanizer is added. After mixing, the rubber needs to be parked for more than 24 hours to allow the additives to fully act, and then re-mixed until the surface is smooth 510. The mixing time of the internal mixer is shorter (6-16 minutes), but attention should be paid to the discharge temperature (about 70℃ for the gas phase silica system).


3. Molding and vulcanization
Compression molding: Put the mixed rubber into the mold and pressurize and heat it with a flat vulcanizer (160-180℃, 5-15 minutes) to complete a vulcanization. In this stage, a preliminary cross-linking network is formed to determine the shape of the product.


Extrusion molding: Use a single screw extruder (length-to-diameter ratio 10:1~12:1), extrude pipes or cables at low temperature (≤40℃), and then continuously vulcanize them with hot air or steam.


Second stage vulcanization: After the first stage vulcanization, the product needs to be treated in an oven at high temperature (200-250℃) for 4-24 hours to eliminate low molecular volatiles and increase crosslinking density, and finally stabilize performance.


4. Quality control and common problems
During the production process, it is necessary to focus on monitoring the purity of raw materials (to avoid impurities causing scorching), mixing uniformity and vulcanization conditions (temperature/time). Common defects include bubbles (raw materials contain water or insufficient vulcanization), mold sticking (insufficient release agent) and dimensional deviation (shrinkage is not compensated).