Preparation And Properties Of Solvent-free Polyurethane With Epoxy Terminated

Blocked solvent-free polyurethane(SFPU)has good storage stability,simple operation in application process,and can be used in many fields,such as electronic potting,plastic film bonding and synthetic leather manufacturing.Because of SFPU does not use organic solvents during the prepared and applied progress,it has good environmental protection and has gradually become a research and development hotspot of new polyurethanes(PU).However,a small molecule of blocking agent will escape when the blocked SFPU is unsealed,which will affect the product performance and the production environment.Based on the above reasons,the structure and properties of solvent-free polyurethane with epoxy terminated(ETSFPU)were studied on the basis of our previous research.Including research on blocked SFPU,research on R value of ETSFPU,diisocyanate,curing agent and curing method.The main research contents are as follows:For the research of blocked SFPU.The blocked SFPU was prepared by using hydrogenated phenylmethane diisocyanate(H12MDI)and polyester diol 4667 as main raw materials,methyl ethyl ketoxime(MEKO)and caprolactam as blocking agents,and dibutyltin dilaurate(DBTDL)as catalysts.The preparation condition and deblocking temperature of blocked SFPU were researched.The results showed that the deblocking temperature of SFPU(MEKO)prepared with MEKO as a blocking agent was 143 0C,and the deblocking temperature of SFPU(caprolactam)prepared with caprolactam as a blocking agent was 163℃;under the same deblocking temperature,the curing speed of SFPU(MEKO)was significantly higher than the curing speed of SFPU(caprolactam);the higher the SFPU’s blocking rate,the longer the SFPU’s initial film formation time and complete curing time,and the better the mechanical properties of the membrane.For the research of R value in ETSFPU.Using H12MDI and polyester diol 4667 as the main raw materials and epoxy propylene alcohol as the terminating agent,a series of ETSFPU resin with different R(molar ratio of isocyanate content to hydroxyl content)values were synthesized when the reaction temperature was 70℃,and the ETSFPU films was prepared with isophorone diamine as curing agent when the curing temperature was 120℃.The effect of R value on the curing time and film forming properties of ETSFPU was investigated.The results showed that the epoxy content increased with the R value increased from 2.5 to 4.5,thermodynamic stability and crystallinity of the ETSFPU film increased;the curing time decreased from 3.4 h to 2.1 h;the wear resistance of the film improved,the tensile strength increased from 4.27 MPa to 10.55 MPa,and the elongation at break decreased from 514.2%to 80.9%;and when the R value was 3.5,the comprehensive properties of the film were better.For the research of diisocyanate in ETSFPU.ETSFPU resin was synthesized by using polyester diol 4667 as the main raw material,epoxy propylene alcohol as the terminating agent,and using H12MDI,MDI,and IPDI as diisocyanates when the R value was 3.5 and reaction temperature was 70℃,ETSFPU film was prepared with isophorone diamine as the curing agent when the curing temperature was 120℃.The effect of diisocyanate on the curing time and film forming properties of ETSFPU was studied.The results showed that when the diisocyanates are IPDI,H12MDI and MDI,respectively,the thermodynamic stability of the ETSFPU film increased in turn;The abrasion resistance of the film is improved,the tensile strength increased from 4.82 MPa to 12.16 MPa,and the elongation at break decreased from 320.9%to 193.1%.For the research of curing agent in ETSFPU.Using the H12MDI and polyester diol 4667 as the main raw materials and epoxy propylene alcohol as the terminating agent,ETSFPU resin was synthesized when the R value was 3.5 and reaction temperature was 70℃.Under the conditions of curing temperature of 120℃,ETSFPU film was prepared by using m-xylylenediamine,isophorone diamine and diethylenetriamine as curing agents.The effect of curing agent on the curing time and film forming properties of ETSFPU was investigated.The results showed that the thermodynamic stability of the ETSFPU film decreased in turn when the curing agents were m-phenylenediamine,isophorone diamine and diethylenetriamine,respectively;the wear degree was unchanged,the tensile strength decreased from 9.38 MPa to 3.41 MPa,and the elongation at break increased from 173.5%to 214.7%.For the research of the curing method in ETSFPU.Using H12MDI and polyester diol 4667 as the main raw materials and epoxy propylene alcohol as the terminating agent,ETSFPU resin was synthesized when the reaction temperature was 70℃ and the ETSFPU films were prepared with isophorone diamine as curing agent when the curing temperature was 120℃.The effects of different R values and diisocyanates on the film-forming properties of ETSFPU at room temperature were studied.And compared with film-forming properties of ETSFPU film at high temperature(120℃).The results showed that when the R value was 3.5 and the diisocyanate is H12MDI,curing at room temperature would improve the crystallinity and mechanical properties of ETSFPU film,and curing at high temperature would improve the thermal stability and wear resistance of ETSFPU film.When the curing temperature increased from 80℃ to 140℃,the curing time reduced from 5.6 h to 2 h,and shrinkage and yellowing only occurred when the curing temperature was 140℃.ETSFPU can be cured with amine curing agent without escaping the blocking agent.It is an environmentally friendly polyurethane material.The research results of this paper provide theoretical support for the development and application of ETSFPU.