Synthesis And Modification Of Polyurethane-polyacrylate Composite Emulsions Containing Fluorine

Recently, with the rapid development of industry, people pay more attention toenvironmental pollution and the more stringent environmental legislations have beenworldwide made to reduce the emission of volatile organic compounds (VOC) into air.Environment-friendly materials have played an important role in many researches andapplications. On this occasion, waterborne coatings were born and have been the bestway to reduce VOC.Waterborne polyurethanes (WPUs) are an important class of materials widely usedin many applications. As a type of environment-friendly materials, WPUs exhibitsome performances at almost the same level as conventional solvent-bornepolyurethanes, such as excellent adhesion and high abrasion resistance. However, asfor hardness, water and weather resistance, WPUs are usually inferior tosolvent-based counterparts, which cannot fulfill the requirement of wood paint.One of the approaches to develop aqueous system with super performances is toproduce hybrid emulsion with multi-phase structure in each particle. In this actical,polyurethane prepolymer which possessed double bond was synthesized throughadding actone firstly, then polyurethane and fluorine-containing polyacrylatecomposite emulsions was prepared by means of balanced swelling andfluorine-containing acrylate dissolved and rised inside the polyurethane prepolymerparticle inside which polyurethane and fluorine-containing polyacrylate compositeemulsions were synthesized by the 'in situ' copolymerization of1H,1H,7H-Dodecafluoroheptyl methacrylate(FMA)and doble bond blockedpolyurethane prepolymer. The composite emulsions synthesized by this process wouldnot cause pollution to the environment.The effects of type and content of initiator, polymerization technique and contentof hydrophilic group on polymerization process and PUFA emulsion were studied,and content of fluorine-containing acrylate on mechanical properties; heat resistanceof PUFA films diameter of PUFA emulsion were also investigated. The copolymerwas characterized by Fourier transform infrared spectroscopy (FTIR), thermogramitryanalysis (TGA), differential scanning calomitry (DSC) and transmission electronmicroscope (TEM). The results indicated that PUFA emulsion was synthesized whichprepared by by means of balanced swelling polymerization technique. Compared with water-soluble initiator (APS), oil-soluble initiator (AIBN) resulted in lessagglomeration, higher conversion of monomers, and the agglomeration markedlydecreased by adding a little amount of emulsifier into polymerization system. Thestorage stability of PUA emulsion increased with the increase of hydrophilic group,while the water resistance of the resultant films decreased. The results also show thatthe water absorption and the surface free energies of copolymer films decreasedrastically with increasing the concentration of FMA. Through annealing treatment,the content of fluorine on the surface of copolymers was found to increase, whichresulted in further decrease of surface free energies.