The mandatory national standard GB 16776-2025 Silicone Structural Sealants for Building, issued in China in August 2025, stipulates that alkane plasticizers (mineral oil) shall not be detectable in silicone structural sealants. Behind this prohibition lies a long-standing systemic quality hazard caused by "mineral-oil-filled sealants" in construction projects: hardening, embrittlement, shrinkage, cracking of the sealant, oil migration in insulating glass units, rainbow film, condensation and water accumulation, and even external pane detachment from curtain wall glass – all of which are safety incidents.
The upgrade of regulations marks that the issue of "mineral-oil-filled sealants" has escalated from an industry unspoken rule to a public safety concern that must be confronted.
Industry Warning: Clustered Outbreaks of Industry Malpractices in Multiple Regions
As competition in the construction industry intensifies, in recent years many building projects have experienced similar quality problems, mainly manifested as premature seal failure in insulating glass units within just a few years, leading to condensation, water accumulation, and in some cases even oil migration and rainbow film (as shown in Figure 1).
▲ Figure 1 Oil migration (left) and rainbow film (right) in insulating glass units
▲ Figure 2 Condensation and water accumulation in insulating glass units
This type of failure is not only related to the durability of the sealant itself, but also to the long-term compatibility between the sealant and the contacting materials. The root cause of such problems is the addition of alkane plasticizers (mineral oil) to the sealant formulation in order to reduce costs!
Tracing the Truth: The Migration Nature of Volatile Plasticizing Components
Why do mineral-oil-filled sealants cause such serious quality issues? This must be understood from their chemical nature and migration characteristics. Although mineral-oil-filled sealants may initially appear elastic, because the molecular structure of mineral oil differs significantly from that of silicone polymers, it is incompatible with the silicone system [1]. Over time, the mineral oil migrates and volatilizes from the sealant, causing the sealant to shrink and harden, which subsequently leads to cracking, debonding, and other problems.
To study the progression of this problem, Baiyun Technology, within the framework of the "50-Year Durability Test", specifically designed comparative test protocols to conduct long-term continuous monitoring of sealant performance across different specimens and different environmental conditions, including mineral-oil-filled sealants. During this continuous monitoring, we found that the performance degradation curve of mineral-oil-filled sealants exhibits a unique and severe pattern.
▲ Figure 3 Comparative test curtain wall for mineral-oil-filled sealants (Turpan)
Empirical Data: Performance Degradation Between the Two Formulations Is Worlds Apart
Research data from the Guangzhou Baiyun 50-Year Durability Test for silicone structural sealants show that silicone structural sealant specimens without mineral oil and with excellent overall performance (e.g., Specimens A and B), exposed to different climatic conditions (G: Guangdong, O: Indoor, T: Turpan), exhibited some variation in tensile strength and elongation at maximum strength, but overall remained relatively stable [2], as shown in Figure 4.
▲ Figure 4 Tensile strength and elongation at maximum strength of Specimens A and B as a function of aging time
However, mineral-oil-filled sealants age very rapidly. They begin to harden within six months, reaching a hardness of 70 within two years, and are highly prone to cracking in the later stage. In contrast, mineral-oil-free sealants, even after ten years, maintain a hardness below 60 and remain relatively stable. The elongation of mineral-oil-filled sealants drops significantly within the first two years, and debonding appears in some areas, while mineral-oil-free sealants perform steadily, with elongation decreasing slowly but still remaining above 100% after 10 years, as shown in Figures 5 and 6.
▲ Figure 5 Hardness of sealants as a function of time after natural weathering exposure
▲ Figure 6 Elongation at maximum strength of sealants as a function of time after natural weathering exposure
As can be seen from the above charts, mineral-oil-filled sealant products exhibit a sharp increase in hardness over time and a cliff-like decline in elongation. This stands in stark contrast to the relatively gentle degradation curve of non-mineral-oil-filled sealants. In fact, in actual engineering projects, mineral-oil-filled sealant products can often be observed to exhibit hardening, cracking, and even adhesive failure within six months to two years, as shown in Figure 7.
▲ Figure 7 Cracking of mineral-oil-filled sealants in actual engineering projects within a short period
The root cause of this phenomenon is that after the mineral oil volatilizes, the mineral-oil-filled sealant shrinks and hardens, completely losing its elasticity, resulting in total failure of sealing and adhesive functions.
Chain Hazards: From Single Failure to Systemic Safety Risks
More seriously, mineral-oil-filled sealants also cause systemic risks. That is, the migration risk of the mineral oil in such sealants not only leads to failure of the sealant itself, but also triggers a "chain reaction" in adjacent materials.
The mineral oil migrating from mineral-oil-filled sealants can cause swelling and dissolution in adjacent materials, especially the butyl hot-melt sealant or thermoplastic spacer sealant in insulating glass systems, which is a primary reason for the overall failure of the insulating glass sealing system. The images at the beginning of this article are typical cases of this situation.
Quality problems caused by mineral-oil-filled sealants only emerge after the mineral oil migrates and volatilizes, which typically takes some time—often six months or even several years after project commissioning. By then, it is impossible to confirm whether the initial sealant contained mineral oil.
Since mineral oil can migrate between different materials, when the primary butyl hot-melt sealant in an insulating glass unit is dissolved, leading to seal failure and condensation/water accumulation, ordinary users lack the professional traceability capabilities to identify "mineral-oil-filled sealant" as the root cause. Even professionals find it difficult to determine whether the mineral oil detected in the sealant originated from the secondary sealant of the insulating glass unit or from the weatherproofing sealant, and thus cannot confirm the responsible party. Faced with huge losses and no recourse for claims, they can only bear significant economic losses and safety risks on their own, while their brand reputation also suffers severely. This elevates a single-material issue to an engineering safety problem of "material system compatibility."
It is precisely because of the long-term hazards of mineral-oil-filled sealants that Baiyun Technology has always adhered to the iron rule of excluding mineral oil from its formulations. This is not conservatism, but a commitment based on scientific understanding of long-term material performance and a strong sense of responsibility for the safety of building systems.
We have real weathering exposure data spanning 29 years since 1997 to prove:
Only by eliminating mineral oil at the source can we fundamentally avoid problems such as oil migration in insulating glass units, cracking and failure of curtain wall and door/window sealants, and safeguard the long-term safety of every building.
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