After being exposed to summer sunlight, prolonged contact with air for electronic component coatings, and repeated cycles of temperature changes in kitchen appliance seals, some materials begin to crack and harden within just a few months—yet silicone products retain their performance stability for years. At the heart of this remarkable difference lies silicones' unique resistance to aging, allowing them to effectively withstand the relentless attack of UV rays and oxygen over time. In this article, we’ll break down the core principles behind silicones’ exceptional anti-aging capabilities, presented in straightforward technical language.

First, understand: Why do materials "age"?

In daily life, plastics become brittle after prolonged exposure to sunlight, and rubber cracks after extended use—essentially, this is due to the external environment damaging the material's molecular structure, primarily manifesting in the following three ways:

1. Ultraviolet light (especially the UVC and UVB bands found in sunlight) carries high energy, which can break the chemical bonds between molecular chains in materials, leading to a loosening of the molecular structure and subsequently causing material degradation.

2. Oxygen can react with material molecules through oxidation, forming oxygen-containing groups that are prone to breakage, thereby causing the material to lose its original elasticity and mechanical strength.

3. Temperature fluctuations and humidity changes will accelerate the above process, further shortening the material's lifespan.

The key to why silicone can withstand these damages lies in the inherently stable protective properties of its molecular structure.

Secret 1: Si-O Bonds — A Molecular Backbone More Stable Than Carbon Bonds

The molecular structure core of silicone is a linear backbone formed by alternating silicon (Si) and oxygen (O) atoms. This Si-O bond-based backbone serves as silicone's primary defense against aging.

Compared to common plastic and rubber materials, its structural advantages are clearly evident:

1. The molecular backbones of plastics and rubbers are composed of carbon-carbon bonds (C-C bonds), with a bond energy of approximately 347 kJ/mol. Ultraviolet light can deliver enough energy to reach the threshold required for breaking C-C bonds, leading to chain scission.

2. The Si-O bond in silicone has a bond energy as high as 452 kJ/mol, significantly stronger than the C-C bond. Ultraviolet light does not provide enough energy to break the Si-O bond, and even under high-temperature conditions above 150°C, the Si-O bond remains structurally stable.

Additionally, the Si-O bond exhibits remarkable chemical inertness, with a high activation energy for reactions with oxygen. As a result, even when exposed to air over extended periods, the molecular backbone remains highly resistant to oxidative degradation, fundamentally slowing down the aging process.

Secret 2: Methyl groups on the molecular chain — the surface protective barrier

If the Si-O bond backbone is considered the molecular core of organosilicon, then the methyl groups (-CH₃) attached to the silicon atoms form a protective outer barrier that shields the core chain.

The methyl groups are evenly distributed along the outer side of the Si-O bond backbone, and their protective effect is primarily evident in three key aspects:

1. When exposed to ultraviolet light, the methyl group can absorb part of the UV energy, thereby reducing the direct intensity of UV radiation acting on the Si-O bond backbone.

2. The methyl group has chemically stable properties and does not easily react with oxygen, forming a dense isolation layer on the molecular surface that prevents oxygen from penetrating into the molecule, thus protecting the main chain from oxidation.

3. The methyl group is hydrophobic, which reduces the adhesion of water molecules to the material's surface, thereby lowering the likelihood of hydrolysis—a key factor contributing to the aging of various materials.

Take silicone sealants designed for outdoor use as an example—their surface methyl groups form a stable protective layer. Even after prolonged exposure to natural environments, the underlying Si-O bond backbone remains intact, allowing the material to retain its elasticity over time and preventing aging-related issues such as cracking or hardening.

Secret 3: Cross-Linking Structure – The Structural Foundation for Enhanced Anti-Aging Performance

In addition to the structural advantages inherent in the molecule itself, silicones undergo crosslinking during processing, forming a three-dimensional network structure that provides these materials with enhanced resistance to aging and long-lasting durability.

Specifically, the molecular chains of silicone do not exist independently but are connected via crosslinking agents to form a three-dimensional network structure. Its anti-aging mechanism includes:

1. When the molecular chains of ordinary materials break, it directly leads to overall structural damage and an irreversible decline in performance.

2. In the crosslinked network of silicone, even if some molecular chains break due to ultraviolet light or oxygen exposure, the surrounding crosslinking nodes can still maintain the overall structural integrity, preventing any structural collapse.

3. Certain types of silicone, such as room-temperature vulcanizing silicone rubber, can form new cross-links through intermolecular reactivity under specific conditions, enabling them to repair minor aging damage and further extend their service life.

This cross-linked structure significantly enhances the structural toughness of silicone, ensuring that even if localized molecular chain damage occurs, the overall performance remains stable.

These scenarios all conceal the exceptional aging-resistant capabilities of silicone.

Combining the principles mentioned above, we can more clearly understand the anti-aging application value of silicone in various fields:

In the field of architecture: The silicone-based water repellent used for exterior walls maintains its waterproof performance even after prolonged exposure to sunlight, thanks primarily to the stability of the Si-O bond backbone and the isolating effect of the methyl groups.

In the electronics field: The silicone-based organic coating on smartphone chips retains its insulating properties even under the influence of air and heat, thanks to its stable molecular structure and the supportive cross-linked network.

In the automotive sector: Silicone seals used around engines must withstand high temperatures, oil contamination, and UV exposure simultaneously. Ensuring their long-term sealing performance hinges on silicone's exceptional resistance to aging.

Everyday essentials: Silicone kitchenware can withstand repeated exposure to high temperatures, and silicone wristbands remain durable—resisting deformation or cracking even after prolonged exposure to sunlight—both clear demonstrations of silicone's exceptional resistance to aging.

Summary: The aging resistance of silicone stems from its "inherent structural advantages combined with optimized post-production processes."

In summary, silicone effectively resists erosion from ultraviolet light and oxygen, a capability rooted in three key characteristics:

The Si-O bond backbone features high bond energy and strong chemical inertness—it is resistant to cleavage by ultraviolet light and unlikely to undergo oxidative reactions with oxygen.

Methyl group: Forms a protective barrier on the molecular surface, reducing the impact of ultraviolet light, oxygen, and water molecules on the main chain.

Crosslinked network structure: Maintains overall structural stability, can repair minor aging damage, and prevents a sharp decline in performance.

It is precisely the synergistic effect of these properties that makes silicone the preferred material for anti-aging needs across various industries—ranging from industrial equipment to everyday products—providing reliable support for the long-term stability and performance of end-use items. This is also one of the key reasons why it’s often referred to as "the MSG of industry."