Study On The Technological Properties Of Multi Isocyanate Terminated Prepolymer And Polyurethane

Polyurethane(PU)has excellent performance,high wear resistance,high strength,good elasticity,large load and good biological properties,which are widely used in oil fields,construction,military,transportation,medical treatment and other fields.The reaction time is too long,the local temperature is too high(apt to explosive polymerization),synthesis process is cumbersome in the process of preparation of polyurethane.Using the prepolymer method,some of the reactions were prepared in advance to prepare the polymer which could be further used.In order to understand the influence of various factors on the preparation process and product of the pre polymerization system,we tested the polymerization temperature,OH:–NCO molar ratio,water content and so on,provide guidance for the synthesis and use of the pre polymer.Major work includes:Testing the conversion of –NCO and the viscosity of PPU by controlling the temperature of the reaction of the prepolymer.With the increase of reaction temperature,the reaction rate was significantly increased.According to the dynamic simulation,Ea =34.5~36.4 kJ/mol.Prepolymer viscosity is low when the conditions for the preparation is low temperature,70 °C is suitable for the preparation of prepolymer.Measurement of free isocyanate content and viscosity of different R prepolymer.Investigation of prepolymer stability by IR and gel rate testing.The greater the value of R,the more time it takes to achieve theoretical response.In the early stage of the reaction,the viscosity increased rapidly,and gradually slowed down,with the increase of R value,the viscosity of the product is decreased,and the stability is improved.High temperature or longer time storage,crosslinking degree increased.Explore the effects of moisture on the structure,stability,Tg and final mechanical properties of the polymer by adding a certain concentration gradient to the prepolymer.With the increase of water content,the hydrogen bond interaction between hard segments was strengthened,the hydrogen bond interaction of the carbonyl group tends to be disordered.Less water mainly plays a role of chain extender,increase in water content,will also play the role of chain extension and cross linking.When the prepolymer is mixed with water,The polyurethane Tg and the degree of hard segment dissolved in the soft segment increased,it is not conducive to the control of the properties of polyurethane.Using these experimental analys,determine the appropriate reaction conditions(T=70?,R=3),and determine the basic formulation of polyurethane:(Component A(HTPB:MDI = 15:47),Component B(HTPB:HPA:N550:CNT = 53:4:30:1)?...