Amino silicone oil has four important parameters: ammonia value, viscosity, reactivity, and particle size. These four parameters basically reflect the quality of amino silicone oil and greatly affect the style of the treated fabric, such as hand feel, whiteness, color, and the ease of emulsification of the silicone oil.

1 ammonia value
The various properties of amino silicone oil, such as softness, smoothness, and fullness, are mostly brought by the amino groups in the polymer. The amino content can be represented by the ammonia value, which refers to the number of milliliters of 1N hydrochloric acid required to neutralize 1g of amino silicone oil. Therefore, the ammonia value is directly proportional to the mole percentage of amino groups in the silicone oil. The higher the amino content, the higher the ammonia value, and the softer and smoother the finished fabric feels. This is because the increase in amino functional groups greatly increases its affinity for the fabric, forming a more regular molecular arrangement, thus giving the fabric a soft and smooth feel.
However, the active hydrogen in the amino group is prone to oxidation to form chromophores, causing the fabric to yellow or slightly yellowish. In the same case of amino groups, it is clear that as the content (or ammonia value) of amino groups increases, the probability of oxidation increases, and the yellowing becomes more severe. As the ammonia value increases, the polarity of the amino silicone oil molecules increases, providing a favorable prerequisite for the emulsification of amino silicone oil, which can be made into microemulsions. The choice of emulsifier and the size and distribution of particle size in the emulsion are also related to the ammonia value.

2 viscosity
Viscosity is related to the molecular weight and molecular weight distribution of polymers. Generally speaking, the higher the viscosity, the higher the molecular weight of amino silicone oil, the better the film forming property on the surface of fabrics, the softer the hand feel, and the better the smoothness, but the poorer the permeability, especially for strong-twisted tight fabrics and fine denier fabrics. Amino silicone oil is difficult to penetrate into the fiber interior, affecting the performance of fabrics. Too high viscosity will also deteriorate the stability of the emulsion or make it difficult to make microemulsions. Generally, it is not possible to adjust products only by viscosity, and often balance product performance through ammonia value and viscosity. Usually, low ammonia value requires high viscosity to balance the softness of fabrics.
Therefore, a smooth feel requires high-viscosity amino-modified silicone oil. However, during the softening treatment baking, some amino silicone oils crosslink to form a film, thereby increasing the molecular weight. Therefore, the initial molecular weight of amino silicone oil is different from the molecular weight of the final film formed on the fabric. Therefore, the same amino silicone oil processed under different process conditions can have significant differences in the smoothness of the final product. On the other hand, low-viscosity amino silicone oil can also improve the feel of the fabric by adding crosslinking agents or adjusting the baking temperature. Low-viscosity amino silicone oil increases permeability, and then through crosslinking agents and process optimization, it can combine the advantages of high and low viscosity amino silicone oils. The viscosity range of general amino silicone oil is 150-5000 centipoise.
However, it is worth noting that the distribution of molecular weight of amino silicone oil may have a greater impact on product performance. Low molecular weight penetrates into the interior of the fiber, while high molecular weight is distributed on the outer surface of the fiber, allowing both the interior and exterior of the fiber to be coated with amino silicone oil, giving the fabric a soft and smooth feel. However, the problem may be that the large difference in molecular weight can affect the stability of the microemulsion.

3 Reactivity
Reactive amino silicone oil can produce self-crosslinking during finishing, and the increase in crosslinking degree will increase the smoothness, softness, and fullness of the fabric, especially for improving elasticity. Of course, when using crosslinking agents or increasing baking conditions, general amino silicone oil can also increase the crosslinking degree, thus improving the resilience. For amino silicone oil with hydroxyl or methylamino end groups, the higher the ammonia value, the better the crosslinking degree, and the better the elasticity.

4. Particle size and charge of microemulsion
The particle size of amino silicone oil lotion is small, generally less than 0.15μ, so the lotion is completely in a thermodynamically stable dispersed state, with excellent storage stability, heat resistance stability, and shear stability, and generally does not break down. At the same time, the small particle size increases the surface area of the particles, greatly improving the contact probability between amino silicone oil and fabric, increasing the surface adsorption amount and improving its uniformity, and improving its permeability, so it is easy to form a continuous film, improving the softness, smoothness, and fullness of the fabric, especially for fine denier fabrics. However, if the particle size distribution of amino silicone oil is uneven, it will greatly affect the stability of the lotion.
The charge of amino silicone oil microemulsion depends on the emulsifier. Generally, anionic fibers adsorb cationic amino silicone oil easily, which improves the treatment effect. However, it is not easy to adsorb anionic emulsions, and the adsorption amount and uniformity of nonionic emulsions are better than anionic emulsions. If the negative charge of the fiber is small, the influence on the different charge properties of microemulsions is greatly reduced. Therefore, chemical fibers such as polyester adsorb various microemulsions with different charge properties and their uniformity are better than cotton fibers.