Modification Of Waterborne Polyurethane And The Preparation And Research Of Its Composite Materials

The mechanical properties and water resistance of waterborne polyurethane(WPU) are of great adjustability. The excellent properties of WPU can be obtained by choosing the different kinds of soft segment. The hydrolysis resistance of WPU films are relatively well by polyether as soft segment. Polyester as soft segment can improve its apparent properties, such as smoothness, brightness and etc. Firstly, based on polyether/polyester as mixed soft segments, hybrid polyurethane(HPU) emulsion was successfully synthesized by prepolymerization method in this paper. Due to the linear structure defects of HPU resulting in its poor performance such as mechanical strength, water resistance and thermal stability. In order to improve the performance of HPU, APTES as silane coupling agent and TOAM as crosslinking agent, crosslinked waterborne polyurethane emulsion modified with silicane(PUSi) was successfully synthesized. Finally, HPU/OMMT nanocomposites were successfully prepared by adopting polyethylene-1,4-buthylene adipateglycol(PBA) intercalating OMMT and then compounding with HPU. The nanocomposites exhibit good mechanical properties and thermal stability.The main research contents of this paper are as follows:(1) The influence of mass ratio of PBA and polytetramethylene glycol(PTMG) on the average particle size, viscosity, Zeta potential, contact angle, water absorption, mechanical property and thermal stability of WPU were studied. Then PTMG/PBA as mixed soft segments, effects of R value, DMPA content and chain extender content on performance of WPU emulsion and film were also discussed.(2) ?-aminopropyltriethoxysilane(APTES) as silane coupling agent and Trishydroxymethylaminomethane(TOAM) as crosslinking agent, PUSi emulsion was successfully synthesized. The effects of dosage of APTES on the particle size and morphology of PUSi emulsion, and water resistance, mechanical properties and thermal stability of the PUSi film were studied.The results show that APTES can reduce the hydrogen bonding degree of between N-H and C=O, and increase the compatibility of the hard and soft segment, leading to the disappearence of hard segment crystalline peak at 25.6° and the soft one at 43.3°, and the rise of the glass transition temperature(Tg) of PUSi film.(3) Organic montmorillonite(OMMT) can be obtained by adopting cetyl trimethyl ammonium bromide(CTAB) organic modification. Then, PBA/OMMT is formed by using PBA to intercalate OMMT. PBA/OMMT as basic material, HPU/OMMT nanocomposites were successfully synthesized.FTIR indicate that the peaks at 534 cm-1 and 467 cm-1 can be attributed to Al-O stretching vibration and Si-O stretching vibration, respectively. It implies that HPU/OMMT emulsion has been successfully synthesized. WXRD show that the chain segment of PU has been intercalateed into the OMMT layer and OMMT is exfoliated when OMMT content is 1%. When the OMMT content is more than 5%, the PBA/OMMT in the HPU emulsion is deposited. DSC curves indicate that the formed suspension chains bewteen PBA/OMMT and HPU improve the compatibility of chain segment, resulting in the decrease of melting temperature of soft segment and hard segment. The addition of OMMT can restrict the movement of molecular chains and lower main chain's flexibility, and the Tg of composites rise.