I. Similarities ：
Although they are two different materials, they share similarities in macroscopic form and certain basic properties:
Porous structure: Both are made through physical or chemical foaming processes and are filled with uniform or uneven cells inside, which makes them both lightweight, shock-absorbing and heat-insulating.
Elasticity: As elastic bodies, both can rebound to a certain extent and return to their original state after being compressed.
Processability: All can be formed by hot pressing through molds to produce various complex-shaped products, such as gaskets, shoe soles, floor MATS, etc.
Electrical insulation and water resistance: Both after foaming have excellent electrical insulation and water resistance properties.
II.Differences:
1. Material Nature and Cost: EVA is a derivative product of petrochemicals. Its raw materials are widely available and its manufacturing process (such as one-time foaming and secondary molding) is mature. Therefore, its cost is extremely low and it is suitable for mass consumer goods. Silica gel is a deep-processed product of silicon dioxide. Its raw materials and preparation processes (such as platinum catalytic foaming) are complex and the cost is extremely high.
2. Heat resistance and flame retardancy (the most crucial difference) EVA is a thermoplastic material. When exposed to high temperatures (such as over 70-80℃), it will soften, melt, and even burn and drip, thus lacking flame retardancy. This is the fundamental reason why it must never be used in high-temperature environments. Silicone is a thermosetting material with extremely excellent resistance to extreme high and low temperatures. It can work for a long time at 250℃ and can withstand temperatures above 300℃ for a short period. At the same time, it has a high flame retardant grade (up to UL94 V-0 level), extinguishes immediately when removed from the fire source, does not produce molten droplets, and has extremely high safety.
3. Environmental friendliness and safety: The quality of EVA varies greatly. High-quality EVA can be odorless, but low-quality EVA may use recycled materials and inferior foaming agents, resulting in residual pungent odors and harmful substances (such as formamide). Silicone is inherently non-toxic and odorless, with extremely stable chemical properties and will not exude harmful substances. It can pass the most stringent certifications such as the FDA (Food and Drug Administration of the United States) and LFGB (European Union Food Grade), and is widely used in medical and food contact fields.
4. Durability and Compression Set One major drawback of EVA is its relatively large compression set. Simply put, an EVA insole will be flattened after being worn for a long time, unable to return to its original thickness and losing its elasticity. The compression set value of silicone is extremely low, which means that it can almost completely return to its original state after being squeezed for a long time. Its durability and service life far exceed those of EVA.