What is the difference between gas-phase silica gel and precipitated silica gel

Similarly, for silicone rubber, the raw material system can be divided into two paths: those reinforced with gas-phase white carbon black are called gas-phase rubber, and those reinforced with precipitation white carbon black are called precipitation rubber. The appearance may be similar, but the price difference is significant. The performance gap is much larger than the price difference. Many buyers go to the sedimentation glue factory to compare prices based on the quote of gas-phase glue, and the "cheaper" compared is actually two types of materials.

Let's talk about reinforcement first

Pure silicone rubber has low strength and almost no practical value, and must be reinforced with white carbon black. The manufacturing method of white carbon black determines its upper limit of quality: the gas-phase method is the high-temperature hydrolysis of silicon tetrachloride in a hydrogen oxygen flame, with fine particle size, high purity, and uniform distribution of surface hydroxyl groups; The precipitation method is produced by the reaction of sodium silicate solution with acid, and its cost is only a fraction of that of the gas-phase method. However, it has a wide particle size distribution, many impurities, and is difficult to treat on the surface.

The difference in reinforcing agents is directly transmitted to the performance of the adhesive material.

What's the difference? Speak with numbers

Tear strength: Gas phase adhesive can generally achieve 25-40 kN/m, while precipitation adhesive mostly ranges from 12-25 kN/m. Tearing is almost complete, which means that thin-walled parts, parts with sharp corners, and parts that need to be repeatedly torn (such as sealing strip ports, button spring walls) have significantly shorter lifespan when using sedimentation adhesive.

Transparency: Gas phase adhesives can be made highly transparent or even optical grade, while precipitation adhesives always have a slightly cloudy and bluish appearance. There is no choice but to use vapor phase when making transparent parts.

Aging resistance: Impurity ions in the precipitation gel will catalyze the degradation of the siloxane main chain in a high-temperature sealed environment, resulting in the seal becoming brittle after one or two years of use in insulation equipment. The heat aging resistance of gas-phase adhesive is significantly better, and the long-term use temperature can be 20-30 ℃ higher than that of precipitation adhesive.

Rebound and compression permanent deformation: The molecular chains of gas-phase adhesives are more evenly combined with fillers, and low compression permanent deformation formulas are mostly based on gas-phase adhesives. The difference in long-term compression sealing will become apparent in the second or third year.

Volatile matter and odor: Gas phase adhesives have low volatile matter and ionic impurities, making them easier to pass regulatory tests in the food, medical, and maternal and child sectors. Precipitation gel needs to meet LFGB and baby product standards, and the cost of waste rate and high molecular weight is not small.

When can I use sedimentation gel

Sedimentation adhesive is not synonymous with low-end products, it has clear application locations: universal seals without extreme requirements for tearing and aging, static shock absorbers, ordinary foot pads, disposable products. In these scenarios, precipitation gel is 30% -50% cheaper than gas-phase gel, with superior performance. Using gas-phase gel is actually a waste of money.

There are actually three criteria for judgment: whether it is thin or not (with a wall thickness of less than 1mm and significant tearing weight), whether it is durable or not (based on annual sealing), and whether it can connect to the human body or food (regulatory threshold). If one of the three is chosen, it is worth moving towards gas-phase adhesive; Not sticking to any of the three, settling glue is a reasonable choice.

A reminder from the procurement side

Take a drawing and ask for quotes from several companies at the same time. If you receive a 30% price difference, don't rush to place an order. First, clarify whether gas-phase adhesive or precipitation adhesive is used, and ask for the raw material grade and testing report. Similarly, when it comes to "silicone", the material base is different, so comparing prices is meaningless. On the contrary, even though they are making thin-walled seals, the supplier's quotation is abnormally cheap, most likely due to a downgrade in material quality - this kind of cheapness is often doubled and returned when customers complain and return orders.