Development of NCO/PFAS-free epoxy polysiloxane surface coating: A new green anti-corrosion direction

Phase 1 of the project covers 8 major finished products including phenyl type, alkyl type, and epoxy type, and upon completion, it will become one of the professional manufacturers with the most complete product line in the field of functional organic silicon prepolymers and silicone resins in China…
II. Research and Development Progress in This Phase
2.1 Synthesis of Organic Silicon Prepolymers
The catalytic ring-opening polymerization process of D4 (octamethylcyclotetrasiloxane) has been optimized, and the ratio of acid catalyst and end-capping agent has been determined.
The problem of wide molecular weight distribution of the prepolymers has been overcome, with the PDI (polydispersity index) reduced from 1.8 to 1.3, significantly improving batch reproducibility.
An online monitoring method for viscosity and conversion rate of the prepolymers has been established, and the error in determining the reaction endpoint has been controlled within ±3%.
2.2 Modification of Silicone Resins
Phenyl monomers have been introduced for copolymerization modification, effectively improving the thermal stability and toughness of the resin.
The temperature resistance grade of the coating has been increased from 180℃ to 250℃, meeting the requirements of customers for high-temperature working conditions.
The hardness-flexibility balance adjustment has been completed, with the pencil hardness reaching 2H while the bending does not crack.
III. Pilot-scale Expansion and Process Verification
3.1 Expansion of 50L Reactor
3 batches of continuous expansion tests have been completed, with the single batch feeding amount increased from 1kg to 8kg, and the yield stabilized at over 92%.
Local overheating occurred during the expansion process, which has been solved by optimizing heat exchange and dripping rhythm.
3.2 Solidification of Key Process Parameters
The temperature curve, stirring rate, and the timing of end-capping agent addition have been written into the SOP, forming a replicable operation card.
The second-party review of raw material suppliers has been completed, and the key monomers have achieved dual-source supply.
IV. Performance Testing and Third-Party Characterization
Thermal gravimetric analysis (TGA) shows that the 5% weight loss temperature reaches 420℃, superior to the industry benchmark of 380℃.
Gel permeation chromatography (GPC) confirms that the molecular weight distribution is within the designed range.
The contact angle test indicates that the water contact angle of the cured film is >105°, demonstrating good hydrophobic properties.
The RoHS and salt spray resistance tests have been completed by a third-party institution, and the report is expected to be returned next month.
V. Current Issues and Next-Step Plans
5.1 Issues to be Addressed
There is a slight fluctuation in batch color during large-scale continuous production, and further investigation into the influence of raw material impurities is needed.
The cost of phenyl monomers is relatively high, and the evaluation of alternative monomers and recycling processes is underway.
5.2 Next-Step Plans
In Q4, a 100-kilogram-scale pilot test will be completed, and the complete process package and cost calculation will be output.
Two key customers will be sent samples for testing and joint verification.
The application evaluation of MQ silicone resins in the field of electronic packaging will be laid out.