In humid tropical environments and high-humidity conditions, phenyl silicone rubber often experiences a sharp increase in dielectric loss tangent (tanδ) due to moisture absorption, leading to insulation heating, signal attenuation, and even thermal breakdown. This becomes a key bottleneck restricting its application in outdoor electrical equipment and high-frequency communications. Phenyl raw rubber, with its unique "non-polar densification" and "water molecule blocking" mechanism, transforms into a "polar shield" for high humidity dielectric loss, constructing a three-dimensional insulating barrier against moisture intrusion at the microscopic level.

The core of phenyl raw rubber's ability to reduce high humidity dielectric loss lies in its "hydrophobic shielding of phenyl groups" and "free volume shrinkage." In high-humidity environments, micropores exist between the methyl segments of ordinary silicone rubber, and trace amounts of polar groups easily adsorb water molecules, forming a "water-polymer" dipole relaxation, causing tanδ to soar to over 0.02 at 90% RH. In phenyl raw rubber, the nonpolar large π bond of the phenyl group acts as a "molecular waterproof layer," reducing the surface energy to 18 mN/m through electron cloud delocalization, thus repelling the adsorption of polar water molecules. Simultaneously, the rigid structure of the phenyl group fills the free volume between molecular chains, reducing the free volume fraction by 40% and blocking the diffusion path of water molecules. After aging at 85℃/85%RH for 168 hours, its tanδ remains stable below 0.001, two orders of magnitude lower than that of ordinary silicone rubber.

Furthermore, the excellent "crosslinking network inertness" of phenyl raw rubber inhibits hydrolysis and oxidation. The Si-C bond energy in its molecular chain is as high as 452 kJ/mol, and the phenyl group forms p-d conjugation with silicon atoms, giving the main chain extremely high resistance to nucleophilic attacks from water molecules, avoiding chain segment breakage and polar group formation caused by hydrolysis. Under a 1 MHz high-frequency electric field, its dielectric constant (ε) fluctuates by <5%, with no obvious dielectric relaxation peak.