| Polyurethane(PU)is widely used as plastics,elastomer,adhesive,coating,fiber and other materials because of its wide range of performance adjustment.However,the heat resistance of general PU is poor so that its performance is weakened at higher than 100℃ in the case of long-term use.Therefore,to broaden the temperature range of PU application,the development of high heat resistance PU has become one of the hot issues in research of polyurethane industry.Some special heat-resistance groups,such as oxazolidone ring(OX ring),isocyanurate ring(IS ring),imide group and the like,can be introduced into the polyurethane chain to increase the heat resistance of polyurethane.Among these special groups,OX ring and IS ring are introduced more easily.At present,the research and application of PU with IS ring has been mainly focused on polyisocyanurate foam(PIR).The research of PU with OX ring has been focused on the formation condition and reaction kinetics of OX ring.Isocyanate and epoxy compounds have even been monofunctional,and the reaction has mainly been in the dilute solution.Therefore,the performance of PU with OX ring has been rarely reported.In this paper,the heat resistance of general polyurethane elastomer(PUE)was first investigated,and then the preparation technology and properties of PUE with OX ring were systematically studied.The general PUE samples were prepared by one-step method from polyether polyol 330 N,ethylene glycol,liquefied MDI and a complex catalyst.The effect of heat treatment temperature and time on the mechanical properties and apparent characteristics of general PUE was investigated,and thermogravimetric analysis was carried out on the general PUE sample.The results show that the short-term heat treatment could improve the overall performance of the general PUE at 120℃,but the mechanical properties of the general PUE decreased with increasing of heat treatment temperature and prolonging of heat treatment time;valus of the initial thermal decomposition temperature of the general PUE samples were 260℃,and the residual amount was almost zero.According to the literature,when the samples of PUE with OX ring were prepared with 330 N,liquefied MDI and epoxy 669(or E-44)as main raw material at selected reaction temperature(150℃,170℃),the effect of the preparation method and the kind and addition amount of catalyst on the mechanical properties and apparent characteristics of the samples of PUE with OX ring were investigated.The results showed that one-step method should be adopted in the preparation of the samples of PUE with OX ring,the appropriate addition amount of 2,4,6-tris(dimethylamino methyl)phenol(DMP-30)as a catalyst was 0.3% in the reaction material system,and the samples of PUE with OX ring can be prepared with the better apparent characteristics and the higher mechanical performance at 150℃or more.The samples of PUE with OX ring were prepared by one-step method with 330 N,liquefied MDI and epoxy 669(or E-44)as main raw material when R value was 1.05 and the addition amount of DMP-30 in the reaction material system was 0.3%.The effect of the kind and amount of epoxy resin and the reaction temperature on the structure and properties of the samples of PUE with OX ring were investigated.The results showed that:(1)at the same reaction temperature,with the amount increasing of 669(or E-44),density of the samples hardly had any change,hardness and tensile strength of the samples increased,and elongation at break of the samples decreased.When the amount of 669 was the same,density,hardness and tensile strength of the samples prepared at 170℃ were similar to those of the samples prepared at 150 ℃,but elongation at break of the samples prepared at 170℃ was higher.When the amount of E-44 was the same,density of the samples prepared at 170℃ was not much different from that of the samples prepared at 150℃,but hardness,tensile strength and elongation at break of the samples prepared at 170℃ were slightly better.(2)The results of FTIR analysis showed that,when the amount of 669(or E-44)was the same,intensity of C=O absorption peak in OX ring for the samples prepared at 170℃ was stronger than that for the samples prepared at 150℃.Among,with the amount increasing of 669 intensity of C=O absorption peak in OX ring for the 669-PUE samples prepared at 170℃ increased.(3)The results of XRD analysis showed that,there were microphase separation phenomena in the samples 669-PUE and E-44-PUE,and the 2θ diffraction angle of the samples shifted to small angle when the amount of 669(or E-44)was higher.(4)The results of DSC analysis showed that,Tg valus of the samples 669-PUE and E-44-PUE were about-58℃ and-56℃,respectively.When the preparation temperature of the samples was the same and the amount of 669(or E-44)was more,Tg valus of the samples were lower.(5)The results of TG analysis showed that,valus of the initial thermal decomposition temperature of the samples 669-PUE and E-44-PUE were 300 ℃ and 340 ℃,respectively,thermal decomposition temperature at the maximum heat loss rate was 400℃,and the residual amount was more.It was shown that the heat resistance of PUE with OX ring was obviously superior to that of general PUE. |
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