Water Based Silicone 2
An important property of silicone SAA is its excellent surface activity and ease of spreading. This property is derived from the low surface tension and weak intermolecular forces of polydimethylsiloxane. The silicon atom is in the center of the tetrahedron in the compound. According to the tetrahedral structure, the two methyl groups are perpendicular to the plane in which the silicon and two adjacent oxygen atoms are connected; since the SI-C bond has a large length, the three hydrogens on the two non-polar methyl groups are like an open umbrella, so that it has good hydrophobicity.
The three hydrogen atoms on the methyl group occupy a large space due to the rotation of the methyl group, thereby increasing the distance between adjacent siloxane molecules; the intermolecular force is inversely proportional to the sixth power of the intermolecular distance, so polydimethylsiloxane has much weaker intermolecular forces than hydrocarbons. Therefore, its surface tension is smaller than that of hydrocarbons of similar molar mass, so that the siloxane is easily spread at the interface. Another reason for polydimethylsiloxane chain distribution and polar surfaces (such as water, metals, fibers, etc.) is that oxygen in the silicon oxide chain forms hydrogen bonds with polar molecules or radicals. The force of the molecules between the silicon oxide chain and the polar surface is increased, causing it to spread into a monolayer; thus making the hydrophobic silicone lying on the polar surface in a unique "extension chain" configuration. The hydrophobic group of a common SAA is erected on a polar surface.
The above characteristics of silicone SAA determine that such materials have the characteristics of easy emulsification, excellent permeability, strong bonding with polar substrates, good surface spreadability, and thin film formation. If it is not modified by a hydrophilic group, it is still hydrophobic.
A typical type of silicone SAA is a polyether silicone oil. Since the polyether group is suspended or embedded in its molecular chain (side chain or main chain), it has a property of being oleophilic and hydrophilic. That is, the oil is not only miscible with the alkane oily substance, but also easily dispersed in water. This is a very useful feature.
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