Research On Preparation And Performance Of Polyurethane/polyaniline Composites

Polyurethane material is extensively applied in many fields due of its unique structureand favorably comprehensive properties,thus it becomes the hot spot of research since itsemergence.Comparing to traditional solvent-based polyurethane, waterborne polyurethane haswidely applied prospect not only because of its low cost,little pollution and good flexibility,but because of its tendency of replacing solvent-based polyurethane.However,its applicationfields are restricted in a large part if it was just used as a common material, the functionalmodification can improve its value-in-use. Polyaniline is the fine material to improveelectrical conductivity of waterborne polyurethane because of its high conductivity and highenvironmental stability, and low price.In order to prepare polyurethane/polyaniline composite which has the conductivefounction, the synthesis of high conductive polyaniline has been researched at first. TheFT-IR analysis indicates that using HCl,H2SO4,DBSA and CSA as dopants respectively cansuccessfully synthesize conductive PANI. The results show that at the same syntheticconditions, the yield and conductivity is higher when PANI dopes with inorganic acid thanorganic acid, the yield and conductivity are all highest when HCl dopes with PANI，with78.83%and0.2634S cm-1respectively,which illustrates that the lower the pH of the protonacid and the smaller the size are, the easier the protonic acid gets into molecular chain to dopewith PANI. The experiment shows that PANI has higher solubility in dimethyl sulfoxide, thesolubility of PANI is higher when dopes with organic acid than inorganic acid,which isbecause that the certain surface active effect of macromolecular organic doping acid canenhance the solubility of PANI. By researching the effect of HCl concentration on theconductivity and yield of polyaniline, it was found that when the concentration of HCl is1.2mol/L, the yield and conductivity of PANI reach the maximum of6.9756S cm-1and72%respectively, which illustrates that increasing the concentration of the doping acid avails theimprovement of doping level of PANI, thus improve the yield and conductivity. In addition,APS/An molar ratio has a significant impact on the conductivity of polyaniline, and whenAPS/An molar ratio is0.6, the conductivity of HCl doped PANI reaches the maximum of6.9826S cm-1,which is because that the rise of oxidative potential can promote theenhancement of oxidation degree of PANI, thus enhance its conductivity.For improving the compatibility between polyaniline and polyurethane, and forimproving the dispersible uniformity of polyaniline, so preparing polyurethane/polyanilinecomposite through in-situ polymerization and used PVP as stabilizer. Infrared spectroscopymanifests that polyurethane/polyaniline composite has been synthesized successfully. Toresearch the effect of stabilizer PVP content on the properties of composite, it was discovered that the resistance of composite decreased obviously when PVP was introduced to PU, andthe resistance of composite is tending towards constant as the PVP content is1.0%, and themechanical properties of composite reaches the optimal performance when the content ofPVP reached to1.5%. After analysising the particle size distribution, it was found that theparticle size of PU, PU/PVP, and PU/PANI increase in an order, and this showed that PUparticle was covered effectivity by PVP and PVP protected PU from being destroyed by APSand doping acid, and ensure the polymerization of aniline monomer was placed on the surfaceof PU which was coverd by PVP and formed the shell of polyaniline finaly. The SEManalysis shows that the whole distribution is much ideal expect there has some agglomerationat local area in the composite. TG characterization showed that the thermostability ofPU/PANI composite which prepared through in-situ polymerization is higher than PU，butlower than PANI. In addition, in order to improve the conductivity of composite, it isnecessary to research the effect of APS/An molar ratio on the integrated performance ofcomposite, it was obviously found that due to the different doping level, thepolyurethane/polyaniline composite which molar ratio of APS/An is0.5has much higermechanical properties and resistance than the one which molar ratio of APS/An is1.0.For simplifying the synthetic process, and improving the dispersible uniformity ofpolyaniline, polyurethane/polyanilin composite has been prepared through physical blendmethod and also used PVP as stabilizer, and studied the effect of PVP on the performance ofpolyurethane/polyaniline composite. The infrared spectroscopy showed that polyurethane andpolyaniline has been compounded successfully. The SEM analysis shows that the particle ofPANI is much bigger and the whole distribution of PANI is not perfect. By measuring theresistance of composites, it was found PVP almost has no influence on its resistance. The testof mechanical property indicated the tensile strength and elongation at break of compositewithout PVP could reach the maximum of19.56MPa and1076.33%respectively when PANIcontent is1.0%; the tensile strength and elongation at break of composite which containedPVP could reach the maximum of18.89MPa and1006.68%as PANI content is3.5%, this isdue to the formation of hydrogen bonding between the carbonyl in PU chain and–N-H inPANI. The TG characterization showed that the thermostability of PU/PANI is localedbetween PU and PANI.Contrast analysis the surface morphologies, thermostability, resistance and mechanicalproperty of composites through physical blend method and in-situ polymerization. The SEManalysis shows that the homogeneity of composite synthesized through in-situ polymerizationis much better than which prepared through physical blend method; the TGA analysis showsthat the thermostability of composite synthesized through physical blend method is much higher than which prepared through in-situ polymerization. All of these were caused by thepoor distribution of bigger polyaniline particle in polyurethane. It was known from thecomprehensive analysis of resistance and mechanical property that, the combination propertyof composite which prepared through in-situ polymerization is much better than thecomposite which synthesized through physical blend method when the content of PANI is2.0%.