Synthesis And Properties Study Of Polyurethane Geadient-Modulus Materials

Polyurethane elastomer(PUE) possess excellent properties because of its special micro-phase separation structure and soft-hard segment structure; and functional gradient materials(FGMs) can prepare heterogeneous materials with more superior performance through the precise constructional design and appropriate preparation technology. By combining PUE with modulus gradient, we can prepare a new type of polyurethane gradient-modulus materials. And the elastic modulus of the materials can be continuously gradient change in a very wide range of temperatures.In this article, polyurethane gradient-modulus materials were prepared in the consecutive polycyclotrimerization method in the presence of a complex amine catalyst with oligodiols and aromatic diisocyanates as raw materials. The structures of the products were characterized by FTIR,1H-NMR, and GPC. The macro-performances of the products were characterized by static mechanics properties, DMTA, DSC, TG and XRD.1. Preparation of polyurethane gradient-modulus materials in two-step method.The structures of the Polyurethane prepolymer(PUP) and Poly(urethane-isocyanurate) (PUI) were characterized by FTIR,1H-NMR, and GPC, the results showed that the products were prepared successfully. And the DSC and DMA results showed that the Tg of PUI was near the 41?, and the energy storage modulus could change gradually and smoothly from 109MPa to 108MPa in the range of-50-200?, and with the increase of the content of cross-linked points, the intensity of relaxation peak, corresponding to tan8, decreased significantly from 1.1 to 0. TGA and mechanical property results showed that with the increase of cross-linked points in the polymer structure, the thermal stability, tensile strength, tensile modulus and hardness of PUI increased, its char yield increased from 3% to 16%, tensile strength could change from 0.5 MPa to 50 MPa, and tensile modulus increased from IMPa to2000MPa, while the elongation at break decreased significantly. Compression stress relaxation curves showed that with the increase of the cross-linked points, stress relaxation process turned out to be relaxed.The structure of cross-linked points could be altered by using different kinds of diisocyanate and the linear chain length could be controllable by changing the length of the oligodiols. In the polycycloterization process, the content of isocyanurate cycles was controlled by regulating the ratio between the added diisocyanate and PUP. In this way, the proportion of flexible structure and rigid structure could be changed, which helped to control the mechanical properties of PUI.2. Preparation of polyurethane gradient-modulus materials in one-step methodThe feasibility of preparation of PUI in one-step method was confirmed by the chemical titration of NCO% and IR tracking. The FTIR results showed PUIs were successfully prepared. And the optimal curing scheme determined by infrared track, was heating in multistep (80 ? /4h+100?/2h(+120?/2h+140?/2h+160?/2h). The results of static mechanics properties test, compression stress relaxation performance test, DMTA and TG revealed that with the increase of R, energy storage modulus of the PUI could gradually decline and tend to be smooth with the increase of temperature, and would only be changed within 1 order of magnitude (109-108MPa); tensile strength increased from 0.5MPa to 45MPa. Meanwhile, heat resistance, tensile modulus, hardness, and density increased, while the elongation at break and tensile strength reduced. In a word, PUI have almost identical chemical structure and basic properties regardless of preparation methods.