Polyurethane elastomers with graded structure were prepared in the graded temperature field. The samples were characterized by FTIR technology. The results show that the degree of microphase separation in the samples decreases with the decrease of the curing temperature. As far as the molar ratio of NH 2 and NCO is concerned, the sample exhibits better graded morphology when the ratio is 0.95. The transparence of the samples prepared also changes gradually, increasing along the direction, in which temperature decreases.FGM, polyurethane, graded, transparence, microphase separation, FTIR Researchers have shown great interesting and efforts to develop the functionally graded material (FGM), since its concept was proposed by Japanese material scientists in the 1980s [1] . FGM is a new class of material that exhibits property changing gradually with spatial position. The property gradient in the material is caused by a position-dependent chemical composition, microstructure, or atomic order [2] . In the last twenty years, great progressing of research about FGM has been made. However, as a new field, research focuses and hotspots are still basic problems, such as manufacturing methods, characterization and performance evaluation, and optimization design [2][3][4][5] .Polyurethane elastomers are an important type of polymer material with excellent physical and chemical properties. And, many applications have been found in different fields. It is promising to find new performances and applications if introducing the FGM concept into the preparation of polyurethane elastomers. It is a pity that there are few studies about polyurethane elastomers with graded structure. Generally, polyurethane appears as a composition of the FGM prepared by forming IPNs or blends. Furukawa et al. [6] prepared graded polyurethane elastomer, whose aggregation structure changed gradually, by controlling and keeping the temperature gradient of the curing mould. Differential scanning calorimetry, polarized optical microscopy and dynamic mechanical analysis were used to characterize the graded structure.Microphase separation is a major characteristic of polyurethane elastomers. It is responsible for many properties of polyurethane. Thus, the gradual change of degree of microphase separation will lead to gradual change of property. In this study, the system TDI-PPG-MOCA was selected to prepare the graded polyurethane by curing in the graded temperature field. FTIR technique was used to characterize its graded structure.

No abstract

Gradient surfaces of polyurethane (PU) membranes were created by UV grafting approach in a graded temperature field. Acrylic acid was selected as grafting monomer to improve the hydrophilicity of the surfaces. The Fourier transform infrared spectroscope (FTIR) spectra and scanning electronic microscope (SEM) were used to characterize the gradient. The results showed that the graft yield increased gradually from the lower temperature end to the higher temperature end. As a result, the hydrophilicity of the gradient surfaces displayed a gradual change along the same direction. Water contact angle measurements also proved this point. The graft reaction rate was investigated as a function of positions along the PU membrane. The average grafting yield of PU membrane increased with the extending of UV light irradiation and increase of photo initiator dosage.