Yellowing of fabrics caused by silicone softeners is a common quality problem in textile finishing, especially noticeable on light-colored or white fabrics. Yellowing not only affects the appearance but may also be accompanied by problems such as a sticky feel.

I. Main Causes of Yellowing
To select non-yellowing varieties, it is first necessary to understand their causes:
1. Amino oxidation: The most common cause. In traditional amino-modified silicone oils, amino groups (especially primary amino groups) are easily oxidized by air during high-temperature baking or long-term storage, generating colored chromophores.
2. Structural instability: Some silicone molecular structures (such as certain epoxy modifications) undergo self-decomposition or rearrangement under high temperature or ultraviolet light, producing colored substances.
3. Catalyst residue: Residual metal catalysts (such as tin compounds) used in the synthesis process may catalyze oxidation reactions or cause discoloration themselves.
4. Reaction with fabrics or auxiliaries: Complex side reactions with chemicals remaining on the fibers (such as chlorine bleaching agents, certain fluorescent whitening agents).

II. Key Characteristics of Non-Yellowing Silicone Softeners
Based on the above mechanisms, silicone softeners with the following characteristics have a lower risk of yellowing:
1. Low amino or modified amino structures:
Low-amino modified silicone oil: By significantly reducing the amino content, the oxidation substrate is fundamentally reduced.
Cyclohexylamino modification: Replacing some primary amino groups with cyclohexylamino groups, which have greater steric hindrance, significantly improves oxidation stability.
Special substituted amino groups (such as acyloxyamino groups): Blocking the oxidation pathway of amino groups through chemical structure modification.
2. Non-amino modified systems:
This is the most effective way to fundamentally eliminate amino-induced yellowing, mainly including:
Epoxy-modified silicones: Providing excellent feel and elasticity, but high thermal stability varieties should be selected.
Polyether-modified silicones (hydrophilic silicone oils): Mainly imparting hydrophilic, moisture-wicking properties to fabrics, while providing a refreshing feel and virtually no yellowing problems.
Hydroxy silicone oil emulsion: Lower cost and low risk of yellowing, but the feel and durability are usually not as good as amino silicone oils. Specialty block polymers: such as polyether-polysiloxane block copolymers, etc.
3. High-quality synthesis and refining process:
Efficient catalysts and removal processes: Ensuring effective removal of metal catalyst residues after synthesis.
Highly pure raw materials and inert environment production: Reducing the risk of oxidation caused by impurity introduction.
Excellent emulsion stability: Microemulsions with small and uniformly distributed particle sizes, less prone to demulsification and oil separation, reducing yellowing caused by local aggregation.

III. Application Recommendations
1. Select as needed: For fabrics requiring extremely high whiteness (such as high-end white shirts and light-colored home textiles), non-amino modified or specially stabilized amino-modified products should be prioritized.
2. Process optimization: Even when using low-yellowing products, avoid excessively high setting temperatures (generally recommended not to exceed 150-160°C) and prolonged baking times.
3. Pre-testing: Before use, strict thermal yellowing tests (such as comparing whiteness after 180°C × 3 min dry heat treatment) and UV resistance tests must be conducted for batch confirmation.

Conclusion: Choosing a silicone softener that is less prone to yellowing hinges on examining its chemical structure (prioritizing non-amino or stabilized amino systems) and product purity. With technological advancements, numerous fourth-generation and fifth-generation silicone softeners that balance low yellowing, excellent hand feel, and durability have become mainstream in the market, providing reliable solutions for high-quality textile finishing.