Preparation And Properties Of Acrylic Acid/Silicone Nanocomposite Modified Waterborne Polyurethane Low Surface Free Energy Coatings

Water-based polyurethane is a new type of environmentally friendly material with designable molecular chain,excellent mechanical properties and low VOC content.Due to the introduction of hydrophilic groups,the overall water resistance decreases,limiting its further promotion.The introduction of polydimethylsiloxane into the structure through copolymer modification combines the excellent mechanical properties of polyurethane with the excellent water resistance of silicone to prepare silicone composite modified polyurethane coatings,which has great research value and application potential.Therefore,this paper firstly optimized the important parameters in the synthetic formulation of the base emulsion,and based on this work,designed the silicone main chain block structure,side linking branching structure and composite modified structure,prepared a variety of distribution of aqueous polyurethane containing silicone emulsion,and discussed the influence of molecular weight,introduction amount and distribution mode on its structure and film-forming properties,the main work is as follows.1.Preparation and performance study of anionic aqueous polyurethane base emulsions.Moderately reactive and yellowing-resistant isophorone diisocyanate(IPDI)was selected as the hard segment,polytetrahydrofuran ether glycol(PTMG),a polyether type with better water resistance,was used as the soft segment,and 1,4-butanediol and dihydroxymethylbutyric acid(DMBA)were used as chain extenders.The effects of isocyanate index(R-value),DMBA and BDO contents on the emulsion and coating film properties were systematically investigated.The results showed that the comprehensive performance was better under the conditions of R value=2.0,DMBA=4% and BDO=3%.2.Preparation and performance study of silicone block modified waterborne polyurethane emulsions containing silicone.Under the optimized synthesis conditions of the base emulsion,a series of waterborne polyurethane emulsions modified with terminal hydroxyl polydimethylsiloxane blocks were prepared by replacing part of PTMG with terminal hydroxyl polydimethylsiloxane(PDMS)introduced into the polyurethane structure as soft segments,and the effects of PDMS molecules and the amount of introduction on the emulsion and coating properties were studied.The results show that PDMS-2000 has good overall performance,and the overall water resistance of the coating increases with the introduction of PDMS,and the modified polyurethane shows better emulsion stability,coating water resistance and mechanical properties when PDMS=5%.3.Preparation and performance study of compound modified waterborne polyurethane emulsion containing silicone.Based on the block modification,the composite modified coating of block/end group polysiloxane was designed and synthesized,and the effects of different silicone distribution methods on the performance of waterborne polyurethane were studied.The results show that the composite modification can make the silicone distribution more uniform,solve the problem of limited reaction sites of end group modification and low degree of freedom of block modification,and help to further improve the comprehensive performance of the composite coating with better water resistance and mechanical strength.