Abstract
A series of PDMS based Poly (urea-urethane) (PUU) with various polar functional groups on their side chain have been prepared by using prepolymer process. FT-IR was used to characterize the structure of the PUU.Surface polarity properties of the PUU films have been studied by the surface contact angle with water. The hydrophilic and hydrophobic characters of PUU films have been investigated. It was found that the PUU film material possesses different surface properties on the aluminum contacting face and on the air contacting face. Results show that the differences of contact angles between two sides of the PUU film are very significant. The contact angles of the aluminum-contacting side decreased with the increasing of the hard segment content in the PUU film. However, the contact angles of air-contacting side keep almost constant.X-ray Photoelectron spectra (XPS) or Electronic Scanning chemical Analysis (ESCA) provides surface chemical information. It was found that silicon contents on the air contacting surface and aluminum contacting surface are different. Results indicate that the silicone/nitrogen ratio on the aluminum-contacting surface is higher than that on the air-contacting surface, and the ratio decreases as the hard segment content increased.Scanning Electron Microscopy (SEM) microphotographs are utilitized to study the surface morphology. Different types of accumulation of PUU between the air (i.e. soft segment) and aluminum (i.e. hard segment)-contacting surface of PUU with different chain extenders were observed.Atomic Force Microscopy (AFM) topographies are utilitized to study the surface roughness. The difference of roughness among the various chain extender of PUU on the aluminum-contacting surface can be studied by the average roughness (Ra). It was be found that the Ra value of the air-contacting surface is larger than that of the aluminum- contacting surface.Surface electrical resistance properties of the PUU films have been studied by measuring the surface electrical resistance at different relative humidities. Results show that when the sample was in dry condition, the surface electrical resistance is in the range of 1014 Ω. However, when the sample was conditioned at 70%, 80% and 100% R.H., the surface resistance decreases to 108 Ω. This electrical resistance value could be applied to antistatic and ESD materials for military applications at some middle or high relative humidity.The mechanical properties of the PUU films material depend on the hard/soft segment ratio in PUU film. The tensile strength of PUU film is ranging from 0.2 Mpa to 8 Mpa; and elongation is from 20% to 900%; tensile modulus is from 2 Mpa to 130 Mpa. The reason that causes this phenomenon is due to the different hard segment content. The more the hard segment content, the lower the tensile strength and tensile modulus. In addition, the more the hard segment content, the higher the elongation.It was also found that the thermal decomposition temperatures of the PUU films are ranging from 270oC to 290oC. The effect of chain extender content on thermal decomposition temperature (the differences are all within 10oC) is insignificant. However, the types of chain extender affect the thermal decomposition temperature significantly. Since different chain extenders will form the different types of structure of PUU.