The Research On Carbon Nanotubes/Waterborne Polyurethane Composites

Due to unique structure and excellent properties,polyurethane materials have beenapplied to many fields. The water-based PU has the advantages of low cost,no pollution andgood flexibility, which make broad application prospect and replace the solvent-basedpolyurethane. However the waterborne polyurethane material has many defects: lower tensilestrength, poor water resistance and less heat resistance, which limit its application. Carbonnanotubes have excellent mechanical strength, thermal stability, so carbon nanotubes is anexcellent material to improve the mechanical properties, thermodynamic properties and waterresistance of polymer.Firstly the carboxyl carbon nanotube/waterborne polyurethane as IPDI monomer wassynthesized. The infrared spectroscopy shows that the carboxyl group and hydroxyl wasgrafted onto the carbon nanotubes. It was shown by SEM that when the content of carboxylcarbon nanotubes was0.5%, the carbon nanotubes can well dispersed in polyurethane whilethe serious reunion was appeared when the content of carbon nanotubes is1%. DSC resultsinformed that the glass transition temperatures Tg of nanocomposites by both physicalblending and by in situ method increased with the content of nanotube, but the extent of Tgchange of the latter was obviously large. The water resistance of composite was improved.The water absorption of composite by physical blending method was from24.3%to7.2%while the water absorption of composite by in situ polymerization method was from24.3%to5.75%.The mechanical properties was also markedly improved. When the content of carbonnanotubes was0.5%the tensile strengh increased to40.26MPa. The elongation at break ofcomposites made by physical blending method decreased with the content of nanotube.Thetensile strength of the composites of0.5%nanotube made by in situ polymerization increasedto44.71MPa and the elongation at break fistly increased then decreased.Based the carboxyl carbon nanotube/waterborne polyurethane composites, the researchedof amino carbon nanotube/waterborne polyurethane was prepared. The composite were alsomade by two methods of physical blending and in situ polymerization. The infraredspectroscopy showed that the carbon nanotubes was grafted by the amino group.The SEMshows that when the contend of amino carbon nanotube was0.5%, the nanotubes can welldispersed in polyurethane while the serious reunion was appeared when the content of carbonnanotubes is1%. The results of DSC was similar with those of carboxyl carbonnanotube/waterborne polyurethane composites. The water resistance of composite wasimproved, the water absorption of composite maked by physical blending method was from24.3%to9.2%while the water absorption of composite maked in situ method was from24..3%to6.4%.The mechanical properties were also markedly enhanced and the content of carbon nanotubes was0.5%, the tensile strength increased to38.06MPa. The elongation atbreak of composites by physical blending method decreased with the content of nanotubes.However, the tensile strength of ones made by in situ polymerization increased to44.12MPawhen the content of nanotube was0.5%. The elongation at break of composites made by insitu method was fistly increased then decreased.Then a new kind of waterborne polyurethane emulsion was researched. HMDI ismonomer in this polyurethane. This new kind of waterborne polyurethane emulsion wassynthesized by two kinds of bimolecular chain extender BDO and EDA. In the paper, theeffects of three single factors R value, the DMPA content and hard segment content on theproperties of waterborne polyurethane was researched.The results showed that the best molarratio of BDO and EDA is20%. The comprehensive performance of waterborne polyurethaneemulsion was best when R revalue was1.0, DMPA content was6.5%and hard segment was40%The carboxyl carbon nanotubes/waterborne polyurethane composites HMDI as themonomer by in situ polymerization was researched.It has been shown that the water resistance,mechanical properties and thermodynamic properties were improved. The glass transitiontemperature Tg increased with the content of nanotubes. The water absorption of compositewas from11.6%to5.9%. The elongation at break fistly increased then decreased with theincrease of content of carbon nanotube. The tensile strength of composite filled by5%nanotube increased to31.06MPa compared to the pure one whose tensile strength was23.09MPa.