Study On Synthesis And Properties Of Waterborne Polyurethanes

Polyurethane is a general terms of polymeric compound whose main chain contains repeating unit of the polymer urethane groups.By changing the type of raw materials and composition to improve the shape and properties of polyurethane products,thereby we can prepare a series of products with distinct chemical and physical properties that have been widely applied to various fields.In the early days,polyurethane is solvent-based,however,with the enhancement of people's environmental awareness,we the need a new polyurethane which is pollution-free,non-toxic and environmentally friendly.As a result,waterborne polyurethane emerged.Studying waterborne polyurethane becomes particularly important,because its unique advantage become an important development direction of the polyurethane industry.We synthesis polyether polyurethane using toluene diisocyanate(TDI-80),water-based polyether or oily polyether as raw materials,and the research is divided into two parts:(1)single component blocked waterborne polyurethane;(2)amphiphilic polyurethane.Firstly,prepolymer was prepared by prepolymer method based on toluene diisocyanate(TDI-80)and waterborne polyether(XJ-4800).Secondly,using different solvents,with sodium bisulfate as blocking agent to block the prepolymer,we can obtain blocked waterborne polyurethane.The effect of types and content of solvent and cosolvent,charging method of cosolven on blocked rate were further studied.The results show that:water as the main solvent,isopropanol or ethanol as the cosolvent,adding the aqueous solution of sodium bisulfite to the prepolymer,and then adding the cosolvent to the prepolymer and stiring,blocked waterborne polyurethane can be prepared.In order to facilitate the blocking reaction and to improve the blocking rate,the effect of blocking coefficient,reaction time and promoting dosage on the blocking reaction were also studied,and it further studied that the temperature has an effect on reopened temperature of blocked waterborne polyurethane with different cosolvent.The results show that:in the water as the main solvents and different cosolvent blocking system,in order to get optimum blocking rate,the requirements for blocking factor and the time of the reaction are different,when the solvent is only water,blocking factor is 1.1,the time of blocking reaction is 10min,the maximum of the blocking rate is 77%.The initial reopened temperature of blocked waterborne polyurethane is 40?,and completely reopened temperature is 82.5 ?.When the solvent is water,cosolvent is ethanol,blocking factor is 1.1,the time of blocking reaction is 20min,the maximum of the blocking rate is 85%.And the initial reopened temperature of blocked waterborne polyurethane is 45 ?,and completely reopened temperature is 80 ?.When the solvent is water,cosolvent is isopropanol,blocking factor is 1.2,the time of blocking reaction is 20min,the maximum of the blocking rate is 84%.And the initial reopened temperature of blocked waterborne polyurethane is 50 ?,and completely reopened temperature is 87.5?.In order to improve the strength of the waterborne polyurethane film and to improve the properties of the pro-oil,we synthesized amphiphilic polyurethane,that is to mix water-based polyether XJ4800 with oily-based polyether N210,and then add to toluene diisocyanate to prepare amphiphilic polyurethane.And it is further discussed the effect of the different mass ratio between the water-based polyether XJ4800 and oily-based polyether N210 on amphiphilic polyurethane,and the effect on the properties of the obtained film after reaction with water.The result shows that:compared with waterborne polyurethane,tensile strength of film which is made of amphiphilic polyurethane with water reaction is improved.But with the increasing of oily-based polyether N210,the curing time of the amphiphilic polyurethane is prolonged,properties package of water is reduced.In addition,the amphiphilic polyurethane has both properties of hydrophilic and lipophilic,and then it has a certain coating capabilities to mixture of water and gasoline etc,therefore it can be used to deal with water contaminated of environmental problems by gasoline,diesel and others.