In the performance of amino silicone oil, the relationship between amine value and hand feel stiffness is not a simple linear correlation, but follows the rule of an "optimal range": Within a certain range, an increase in amine value can improve the hand feel; however, when the amine value is too high, the hand feel does tend to become stiffer, and the silkiness may also decrease. The specific principles are as follows:

1. The nature of amine value: Reflecting amino group content

2. The law of how amine value affects hand feel

• Low amine value stage (e.g., amine value < 0.3 mmol/g):
  The content of amino groups is low, so the binding force between silicone oil and fibers is weak. The interactions between molecular chains (such as hydrogen bonds) are few, resulting in a softer and smoother film. However, there may be problems such as poor durability (easy to fall off), a "weakly soft" hand feel, and insufficient silkiness.
• Medium amine value stage (e.g., amine value 0.3~0.6 mmol/g):
  The amino group content is moderate, which can not only ensure firm binding with fibers but also avoid excessive cross-linking or increased rigidity of molecular chains due to too many amino groups. At this time, the flexibility and elasticity of the silicone oil film are well balanced, with a soft, plump hand feel and prominent silkiness, which is the ideal state pursued by most textiles (such as cotton and knitted fabrics).
• High amine value stage (e.g., amine value > 0.6 mmol/g):
  When the amino group content is too high, the interactions between polar groups (hydrogen bonds, electrostatic attraction) are significantly enhanced, leading to a decrease in the flexibility of silicone oil molecular chains and an increase in the rigidity of the formed film (similar to "molecular aggregation"). At this time, the hand feel changes from soft to stiff and rough, and may even be accompanied by a "dry feeling", with silkiness significantly reduced. In addition, an excessively high amine value may also increase the risk of yellowing of textiles.

Conclusion

The hand feel of amino silicone oil does not monotonically become softer as the amine value increases; instead, there is an "optimal amine value range". When the amine value exceeds this range, due to excessively strong intermolecular forces, the hand feel tends to become stiffer and the silkiness decreases. In practical applications, it is necessary to select amino silicone oil products with an appropriate amine value according to the fiber type and hand feel requirements.