Preparation And Performance Study Of Silicone Polyurethane Elastomers And Composite Silicone Waterborne Polyurethanes

Since the 1940s,polyurethane materials have been invented and grown rapidly,forming a complete industrial system from raw materials,synthesis processes to the development of polyurethane products.Polyurethane has been developed towards high performance,high efficiency,energy conservation,and environmental protection since the 1970s.As promising materials,polyurethane elastomers and water-based polyurethane coatings are attracting increasing attention for their relevant technological applications.With the virtues of good tensile strength,tear strength,impact resistance,abrasion resistance,and weather resistance,polyurethane elastomers can be used in a wide range,from hard rubbers to soft engineering thermoplastics as they are elastic and melt-processable.However,with the development of science and technology,the performance requirements of polyurethane elastomers continuously have been increased and the application range of polyurethane elastomers also have been broadened.Silicones have good resistance to high and low temperatures and are waterrepellent,non-flammable,and physiologically inert.Therefore,it is feasible to introduce silicone polymers into the polyurethane molecular chain by grafting or blocking.Water-based polyurethane,polyurethane dispersion with water as the solvent,has become one of the research hotspots in recent years with low organic content,low toxicity,and uninflammability.This thesis demonstrated the synthesis and performance of silicone polyurethane elastomers and composite silicone aqueous polyurethanes.1.Poly(siloxane-heterosulfide)diols were prepared by using vinyl disiloxane,poly(ethylene glycol)dithiol,and 2-mercaptoethanol as raw material via thiol-ene click reaction.The obtained poly(siloxane-heterosulfide)diols are heat resistant and have no decomposition or volatilization at 300℃.Moreover,thiol-ene click reaction conditions are simple,operated easily,highly directional,and high atomic utilization with very few by-products.In addition,the reaction process didn’t require heating and cooling with low operating and equipment costs.2.Composite silicone aqueous polyurethanes were synthesized by using poly(siloxane-heterosulfide)diol and α,ω-bis(hydroxyethoxypropyl)polydimethylsiloxane as soft segments.The effects of types of oligomeric diol,types of isocyanate,contents of siloxane and the hydrophilic group were investigated for water repellency,water resistance,mechanical and thermodynamic properties of the aqueous polyurethanes.The experimental results show that the composite silicone waterborne polyurethane has good water repellency,water resistance,low water absorption and temperature resistance as wall coating within the normal use range.In comparison with polyetherbased waterborne polyurethanes,composite silicone waterborne polyurethanes exhibit great water resistance,water absorption,temperature resistance,and alkali resistance.In addition,composite silicone waterborne polyurethanes have good hydrophilic properties compared with polysiloxane-based waterborne polyurethanes.3.Polyurethane elastomers were synthesized by using poly(siloxane-heterosulfide)diols as soft chain segments.Three series of polyurethane elastomers with different hard segment contents,PU-Ⅰ,PU-Ⅱ and PU-Ⅲ,were designed.The effects of the molecular weight and hard segment content of the oligomeric diols on the mechanical properties of the polyurethane elastomers were investigated.The experimental results show that the mechanical properties of the polyurethane elastomers are excellent in a specific range of hard segments.