In humanity's quest to explore the final frontiers of Earth, whether it be the Mariana Trench at depths exceeding 10,000 meters or the interior of Antarctica where temperatures can plummet to -80°C, equipment materials face unprecedented challenges including high pressure, extreme cold, salt corrosion, and long-term maintenance-free operation. In such extreme environments, metals can become brittle, plastics harden, and ordinary rubbers lose their elasticity or even crumble into powder. However, special silicone rubbers, thanks to their unique molecular structure and tunable properties, have emerged as the "flexible defense" for critical components like deep-sea submersible seals, polar research suit seams, and ice-robot joints, quietly safeguarding the boundaries of human safety as we venture into the unknown.

1. Deep Sea Pressure: High-Pressure Resistance and Low Compression Set

At a depth of 10,000 meters, hydrostatic pressure reaches an astounding 110 MPa (approximately 1100 atmospheres), sufficient to crush submarine hulls. Sealing materials must:

Resist being extruded from gaps under high pressure (extrusion resistance);

Quickly return to their original shape upon decompression (low compression set);

Not absorb water or swell after prolonged immersion.

Highly filled, high-strength silicone rubbers (such as those enhanced with fumed silica + PTFE micropowder) perform exceptionally well here:

With hardness ranging from 70A to 80A, they enhance extrusion resistance;

Under conditions of 150°C for 70 hours, their compression set is less than 20%, significantly outperforming nitrile or fluororubber;

Water absorption is less than 0.1%, preventing volume changes due to moisture that could compromise seal integrity.

For example, the manned submersible "Fendouzhe" uses custom silicone rubber O-rings for its observation window seals and hydraulic interfaces of robotic arms, ensuring zero leakage during missions at depths of over 10,000 meters.

2. Polar Cold: Maintaining Elasticity at Ultra-Low Temperatures

Winter temperatures in Antarctica can drop to -89.2°C. Ordinary rubbers have glass transition temperatures (Tg) above -50°C, making them hard and brittle. However, low-phenyl or vinyl-modified silicone rubbers can lower Tg below -115°C:

They retain over 300% elongation at break at -70°C;

Their elastic modulus changes smoothly without sudden stress variations;

After 500 cycles of thermal cycling between -70°C and +50°C, no cracks appear.

This makes them ideal for sealing strips on doors and windows of polar research stations, gaskets in snow vehicle fuel systems, and buffer layers in spacesuit joints. NASA also selects silicone rubber seals for Mars exploration missions to cope with nighttime lows of -125°C.

3. Dual Extreme Challenges: Combining Deep Sea and Low Temperature

Scenarios like Arctic seabed oil extraction and subglacial lake drilling present combined high-pressure and low-temperature challenges. Solutions must balance:

Flexibility at low temperatures;

Dimensional stability under high pressure;

Resistance to seawater corrosion and biofouling.

Strategies include:

Copolymer modification: Introducing small amounts of phenyl groups improves low-temperature performance while maintaining the flexibility of the main Si-O bond chain;

Surface coatings: Applying antifouling silane layers inhibits microbial film formation;

Structural optimization: Using X-shaped or D-shaped cross-section seals enhances high-pressure self-tightening effects.

4. Long-Term Reliability: Aging Resistance and Low Outgassing

Deep-sea and polar equipment often operates for years without maintenance, necessitating ultra-long lifespans:

Hydrolysis resistance: Addition-cure systems produce no acetic acid byproducts, avoiding internal corrosion;

Radiation resistance: Though UV light is absent in the deep sea, cosmic rays and natural radioactive elements still pose risks; adding stabilizers like CeO₂ helps;

Low outgassing: In vacuum or enclosed compartments, volatiles can condense on optical windows or sensors. High-purity silicone rubber has a total mass loss (TML) of less than 0.5%, meeting NASA’s ASTM E595 standard.

5. Frontier Exploration: Intelligent Responses and Self-Repair

To address more complex tasks, new generations of silicone rubbers are incorporating intelligent features:

Pressure sensing: Incorporating conductive carbon black allows remote monitoring of seal integrity through changes in electrical resistance when pressure is applied;

Self-healing networks: Introducing Diels-Alder reversible bonds enables autonomous healing of microcracks through heating;

Biomimetic surfaces: Mimicking shark skin microstructures reduces drag caused by marine organisms adhering to deep-sea equipment.

6. Domestic Breakthroughs and Future Requirements

Previously, high-end deep-sea silicone rubbers were largely imported from companies like Dow Corning in the U.S. and Wacker in Germany. Recently, Chinese research institutions have successfully developed:

Deep-sea sealing silicones capable of withstanding pressures up to 120 MPa;

Polar-grade silicones operable down to -90°C;

Products certified by international standards such as DNV GL and API 6A.

However, facing new scenarios like full-ocean-depth long-term habitation and autonomous underwater robots beneath ice, there remains a need to improve batch consistency and accumulate databases of extreme condition performances.

Conclusion

In the abyss where sunlight cannot reach and on icy plains swept by fierce winds, silicone rubber stands as a silent guardian. It does not emit light but ensures detectors can clearly observe hydrothermal vents on the seafloor; it does not generate heat but keeps scientific expedition members holding warm devices during polar nights. This flexible yet robust material, stable at the molecular level, responds to Earth's harshest tests. As humanity ventures into the unknown, this transparent silicon-based force always provides reliable protection in silence, forming the last arc of safety—because the courage to explore deserves the most dependable guardianship.



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