In procurement and quality control discussions around liquid silicone, price is often the first variable placed on the table. But what truly determines whether a liquid silicone can reliably serve in demanding scenarios such as medical, food-contact, and precision electronics is a set of hidden parameters spanning raw materials, formulation, and process. These parameters are not written on quotation sheets, yet they constitute the true code to high-quality liquid silicone.

The First Code: Selection of the Vulcanization System

The vulcanization method of liquid silicone fundamentally determines the material's purity boundary. The industry's two mainstream technical routes—peroxide vulcanization and platinum addition vulcanization—differ essentially in byproduct control.

Peroxide vulcanization relies on free radical reactions to initiate crosslinking. This process generates byproducts, and the byproducts do not fully dissipate but remain permanently in the final product. Technical documentation from Freudenberg Medical Group notes that peroxide-cured silicone "has a noticeable odor, and peroxide byproducts may leach from the material." For medical or pharmaceutical applications, this leaching risk warrants particular attention.

Platinum addition vulcanization follows a different path. Silane and silicone combine completely, with no decomposition or byproducts generated during the reaction—in short, "A+B=C." Addition-cure liquid silicone rubber produces no byproducts during vulcanization, making high-purity products readily achievable. This chemical-level difference is the first watershed of high-quality liquid silicone.

The Second Code: Control of Volatile Content

If the vulcanization system determines "whether byproducts exist," then volatile control determines "how much residue remains." For food-contact and medical applications, this indicator is shifting from a bonus point to an entry threshold.

Taking China's food-contact silicone rubber standard as an example, GB 4806.16-2025 added a volatile matter limit requirement compared with the previous version, with a limit of 0.5 g/100 g, along with a dedicated determination method. This change means that a general claim of "food grade" alone is no longer sufficient to prove compliance—suppliers need to be able to provide specific test data for volatile matter.

High-quality liquid silicone needs to consider this indicator at the formulation design stage. The choice of base polymer, the treatment method of fillers, and whether deep devolatilization processes are adopted all directly affect the volatile level of the final product. Addition-cure systems have a natural advantage in this dimension due to their byproduct-free chemical characteristics, but the premise is that no new volatile components are introduced at the raw material or process ends.

The Third Code: Thoroughness of Crosslinking

Even with the right vulcanization system selected, whether the crosslinking reaction is "completed" equally determines quality. After addition-cure liquid silicone rubber completes thermal vulcanization through platinum catalysis, unreacted vinyl or hydrogen groups may still remain in the system, resulting in incomplete crosslinking that further affects aging resistance and compression set.

A study on low-compression-set liquid silicone rubber showed that by introducing a compression set improver, vinyl groups not thoroughly reacted after platinum vulcanization can be further vulcanized, increasing crosslink density and thereby reducing compression set under 180°C×22h conditions to ≤10%. This data reveals an easily overlooked fact: with the same platinum system, differences in formulation details are sufficient to create significant gaps in key performance indicators.

For downstream product manufacturers, this means that when selecting liquid silicone suppliers, one cannot simply look at "whether it is platinum vulcanized" but must also ask: Has the formulation been optimized for crosslinking thoroughness? Is there specific test data for compression set?

The Fourth Code: Verifiability from Standards to Data

The ultimate test of high-quality liquid silicone lies not in suppliers' self-declarations but in traceable test data. Freudenberg's technical documentation provides a verification path worth referencing: quantification of peroxides and oligosiloxanes can be accomplished through thermal desorption followed by gas chromatography-mass spectrometry analysis, with analytical methods adjustable according to customers' specific specification requirements.

For buyers, a qualified liquid silicone supplier should be able to provide: written confirmation of the vulcanization system (platinum-catalyzed or peroxide), test reports for volatile matter or extractables, and key performance data for specific application scenarios (such as compression set, tear strength, etc.). If a technical data sheet can only provide conventional indicators such as hardness and tensile strength while unable to answer any of the above questions, then the word "high quality" lacks verifiable support.

The key code to high-quality liquid silicone is essentially the superposition of chemical choices and process control. The platinum system provides the chemical foundation of no byproducts; deep devolatilization and crosslinking optimization determine whether this foundation can be translated into measurable low volatiles and low compression set; and complete test data makes all of this verifiable and traceable. For liquid adhesive enterprises, explaining these codes clearly and solidly is more convincing than any marketing rhetoric.

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