Introduce some common core parameters of silicone rubber:
A. Viscosity
Definition: The volume characteristic of a liquid, quasi liquid, or quasi solid substance that resists flow, which refers to the internal friction or flow resistance between molecules when flowing under external forces. Normally, viscosity and hardness are directly proportional.
B. Tensile strength
Tensile strength refers to the force required per range unit to cause a rubber material sample to tear. The tensile strength range of hot sulfurized solid silicone rubber is between 4.0-12.5MPa. The tensile strength range of fluorosilicone rubber is between 8.7-12.1 MPa. The tensile strength range of liquid silicone rubber is between 3.6-11.0MPa.
C. Hardness
The ability of a material to resist local pressure from hard objects on its surface is called hardness. Silicone rubber has a Shore hardness range of 10 to 80, giving designers ample freedom to choose the desired hardness to best achieve specific functions. Mixing polymer substrates, fillers, and additives in different proportions can achieve various intermediate hardness values. Similarly, the heating and curing time and temperature can also change the hardness without damaging other physical characteristics.
D. Tear strength
The resistance that impedes the expansion of incisions or marks when force is applied to samples with incisions. Even after being cut open and subjected to extremely high torsional stress, hot sulfurized solid silicone rubber can remain intact without tearing. The tear strength range of hot sulfurized solid silicone rubber is between 9-55 kN/m. The tear strength range of fluorosilicone rubber is between 17.5-46.4 kN/m. The tear strength range of liquid silicone rubber is between 11.5-52 kN/m.
E. Operation time
The operation time starts from the moment the colloid is added to the vulcanizing agent. There is no complete boundary between this operation time and the subsequent vulcanization time. The colloid undergoes vulcanization reaction from the moment the vulcanizing agent is added. This operation time means that the 30 minute vulcanization reaction of the product can not affect the quality of the finished product. So the more time is saved during the product operation process, the more advantageous it is for the finished product.
F. Proportion of vulcanizing agent
Silicone rubber is the most common two-component vulcanized silicone rubber. When not in use, silicone rubber is divided into two parts: colloid and vulcanizing agent. When in use, it can be mixed evenly according to a certain proportion before operation. In general, only the weight of the colloid needs to be considered, but in special cases, the weight of other additives in the silicone gel needs to be taken into account. For example, when using transfer printing silicone, the proportion of vulcanizing agent needs to be calculated based on the total weight of silicone and added silicone oil.
G. Elongation rate
It usually refers to the "ultimate elongation at break" or the percentage increase relative to the original length when the sample fractures. The elongation range of hot sulfurized solid silicone rubber is generally between 90 and 1120%. The elongation of fluorosilicone rubber is generally between 159 and 699%. The elongation of liquid silicone rubber is generally between 220 and 900%. Different processing methods and the selection of hardening agents can greatly alter its elongation. The elongation of silicone rubber is closely related to temperature.
H. Sulfurization time
Some places may say it's the curing time. That is to say, after such a long time, the vulcanization reaction of silicone gel has basically ended. This basically means that the product is ready for use, but in fact, there is still a small part of the curing reaction that has not ended. So products made of silicone rubber, such as silicone molds, usually need to be left for a period of time before being put into use.
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