Preparation Of Tdi-polyurethane/polyacrylate Hybrid Emulsion By Solvent-free Method And The Modification Of Latex Film

The application of waterborne polyurethane based on isophorone diisocyanate (IPDI) is affected often due to high price and poor compatibility with a variety of powder filler caused by low polarity of IPDI. In the case of less demand to yellowing resistance, using toluene diisocyanate (TDI) of low price instead of IPDI to prepare waterborne polyurethane shows a clear market advantage. However, if we use TDI instead of IPDI to prepare waterborne polyurethane, the reaction must be carried out at low temperature to reduce the reaction activity when the prepolymer is dispersed into water due to high reactivity of TDI. On the other hand, acrylic monomer is not good solvent for synthesis of waterborne polyurethane and it can cause the failure of emulsification because of high viscosity at low temperature.In this work, we report a new solvent-free method of high temperature emulsification to prepare waterborne polyurethane based on TDI. Using the blend of methyl methacrylate (MMA) and butyl acrylate (BA) instead of acetone to dilute the reaction system, hydroxyethyl acrylate (HEA) to terminate the ends of prepolymer, and emulsified at 85°C, TDI-polyurethane/polyacrylate (TDI-PU/PA) hybrid emulsion was synthesized using toluene diisocyanate (TDI), polytetramethylene ether glycol (PTMG), 1,6-hexanediol (HDO) and dimethylol propionic acid (DMPA) based on the solvent-free method. The better emulsion could be prepared when the molar ratio of NCO group in TDI to total OH group in PTMG, DMPA and HDO was 1.18, triethylamine (TEA) and water were added simultaneously during the emulsification, and acrylic monomer was initiated by potassium persulfate at 80°C. It was found that tensile strength, pendulum hardness of the latex film cast from hybrid emulsion increased and water resistance became better with increasing the content of MMA. Compared to IPDI-PU/PA, TDI-PU/PA hybrid emulsion had a low price, and could be added into more 100% titanium pigment which introduced an increase of hardness and hiding power of the latex film. Based on initiation of ⁶⁰Coγ-ray, novel fluorinated polyurethane/polyacrylate hybrid emulsions, dodecafluoroheptyl methacrylate (DFMA) as fluorinated monomer, were successfully prepared. The chain structure and grafting reaction were confirmed by FTIR analysis. The grafting ratio of polymethyl methacrylate and polyurethane was obtained by calculating the ratio of N–H peak integral area and Ph(C=C) peak integral area and it was found that the grafting ratio doubled after initiated by ⁶⁰Coγ-ray. By measuring the pendulum hardness, it was found that the increase of MMA content or choosing ⁶⁰Coγ-ray radiation polymerization could both enhance the hardness of latex film. The DMFA content had a significant impact on mechanical property and thermal stability of WPUA latex film. The incorporation of DMFA had been proved to possess higher contact angle and better water resistance.