Silicone Resin 2.0- When R/Si Ratio Becomes the Judge of "Thermosetting" and "Flexibility"
Introduction
Silicone resin is a highly cross-linked polysiloxane, and its curing behavior, film hardness, and high-temperature elasticity are directly determined by the R/Si ratio (molar ratio of organic substituents to silicon atoms). This article combines the latest cover paper of Jiangnan University to analyze how the material properties "drift all the way" from R/Si 1.0 to 1.6.
text
Stereoscopic splicing of four structural units: M, D, T, and Q
M (monofunctional)=chain termination, reducing crosslinking density;
T (trifunctional)+Q (tetrafunctional)=crosslinking core, contributing to hardness;
By adjusting the D/T/Q ratio, R/Si can be precisely locked at 1.2 ± 0.02, achieving low-temperature curing at 150 ℃.
The "thermoelastic magic" introduced by phenyl groups
When the phenyl/(methyl+phenyl) group is in the range of 20-60%, the paint film has a 180 ℃ elasticity retention rate of>85% and a pencil hardness of 2H. After fluorosilicon modification, the UV curing formula can dry within 3 seconds and is used for 5G base station antenna covers.
Engineering case
High voltage motor main insulation: R/Si=1.0, mica tape impregnated and cured at 200 ℃/4 h, breakdown strength ≥ 22 kV · mm ⁻¹;
High temperature resistant cookware coating: R/Si=1.4, added epoxy silane coupling agent, adhesion level 0 to aluminum substrate, continuous cooking for 500 hours without foaming.
conclusion
Silicone resin is not about "harder is better", but about finding a balance between "thermosetting" and "elastic" cross-linking networks. The R/Si ratio is the precise vernier caliper.