Modified siloxanes used as raw materials for clothing waterproofing agents are a type of polymer material that is given hydrophobic properties through chemical modification and are widely used in waterproof, oil-proof and anti-fouling finishing of textiles.
Common modified siloxane types as below:
1. Alkyl-modified siloxanes
Structure: Siloxane backbone grafted with long-chain alkyl groups (e.g., C8-C18).
Features: Enhanced hydrophobicity, suitable for general waterproofing needs.
Example: Octadecyltrimethoxysiloxane.
2. Fluoroalkyl-modified siloxanes
Structure: Fluorinated groups (e.g., perfluoroalkyl) are introduced.
Features: Superhydrophobic (contact angle >150°) and oil-repellent, but relatively high cost.
Example: Perfluorooctylethyltrimethoxysilane.
3. Epoxy/amino-modified siloxanes
Structure: Contains epoxy or amino functional groups.
Features: Improved adhesion to fibers and improved wash resistance.
Applications: Used for durable water-repellent finishes.
4. Polyether-modified siloxanes
Structure: Copolymerization of siloxane and polyether (e.g., PEG/PPG).
Features: Balanced hydrophilicity and hydrophobicity, suitable for breathable and waterproof fabrics (e.g., outdoor clothing).
5. Reactive siloxanes (such as silane coupling agents)
Example: Vinyltriethoxysilane.
Function: Reacts with hydroxyl groups on the fiber surface to form a durable coating.
Today's article mainly talks about the fourth type, the analysis and application of modified siloxane(Asso known as Water-soluble Silicone Oil)in clothing waterproofing agents.
Water-soluble silicone oil is a type of siloxane that has been hydrophilically modified to make it soluble in water or uniformly dispersed in an aqueous phase. It combines hydrophobicity with ease of processing in waterproof clothing finishing. The following is an analysis of its key characteristics, modification methods, and applications:
1. Structure and Modification Principles of Water-Soluble Silicone Fluids
Basic Structure
Main Chain: Polydimethylsiloxane (PDMS) provides the basic hydrophobicity.
Hydrophilic Group: Polar groups (such as polyether, carboxyl, and sulfonic acid groups) are introduced through chemical modification to impart water solubility.
2. Application Characteristics in Clothing Waterproofing
Core Function
Hydrophobic Finish: The siloxane backbone forms a hydrophobic film on the fiber surface, with a contact angle of 130°-150°.
Processability: It dissolves directly in water, requiring no organic solvents, making it suitable for processes such as padding and spraying.
Combination Function: It can be combined with other additives (fluorocarbon resins, crosslinking agents) to enhance durability or stain resistance.
3. Key Points for Performance Optimization
3.1 Hydrophilic-Hydrophobic Balance
EO/PO Ratio: A higher EO (ethylene oxide) ratio results in greater water solubility, but may reduce water repellency (crosslinking and curing are required to restore hydrophobicity).
Molecular Weight Control: Low molecular weight (<10,000) allows for easier fiber penetration, while high molecular weight (>50,000) provides better film-forming properties.
3.2 Improving Washability
Crosslinking Technology: Use blocked isocyanates or epoxy crosslinkers, which form a network structure after high-temperature curing.
Fluorocarbon Resin Compounding: Enhance durability through fluorine-silicon synergy (e.g., copolymerization with perfluoroalkyl acrylates).
3.3 Environmental Improvement
PFOA/PFOS-Free: Avoid traditional fluorinated additives and utilize short-chain fluorinated modified silicone fluids or bio-based silicone fluids.
Low-Temperature Curing: Develop photocurable or enzyme-catalyzed crosslinking systems to reduce energy consumption.
Water-soluble silicone oils overcome the processing challenges of traditional silicone oils through hydrophilic modification, but their waterproofing properties require optimization through cross-linking or compounding. Future development will focus on environmental friendliness, durability, and multifunctional integration. If you require formulation recommendations for specific processes (such as spray finishing or impregnation), we welcome further discussions.
