Abstract
Waterborne polyurethanes are an interesting alternative to current solvent based polyurethanes used in many industries because of their high performance. In this study, waterborne polyurethane dispersion were prepared by polyaddition reaction using Polyethylene glycol (PEG Mw 2000) and isophorone diisocyanate (IPDI) in presence of dibutyltin dilaurate (DBTL) as catalyst. The urea bridges were created between waterborne polyurethane chains to improve rheological, thermal and mechanical properties by the incorporation of hexamethylene diisocyanate (HDI) as crosslinking agent. Several properties of crosslinked waterborne polyurethane were measured by particle size distribution, viscosity measurement, IR spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and strength testing. This method improves the properties of waterborne polyurethane (WPD) in increasing the crosslinking density by forming strong network and hydrogen bonds between polyurethane chains.
Highlights
Waterborne polyurethane dispersion were prepared by polyaddition reaction using Polyethylene glycol (PEG Mw 2000) and isophorone diisocyanate (IPDI) in presence of dibutyltin dilaurate (DBTL) as catalyst
The attenuated total reflectance (ATR)-IR spectrum of the waterborne polyurethane dispersion shows a slight shift in the value of the characteristic peaks and this is probably due to the formation of hydrogen bonds [Elana O., 2009] between chains contributing to the strengthening of crosslinking of waterborne polyurethane dispersion
The crosslinking method by introduction of urea bridge between the chains has the advantage of not involving an external crosslinking agent that may increase the viscosity of the dispersion but it is through the use of a low molecular weight diisocyanate
Summary
The polyurethane dispersions were prepared by reaction of an isocyanate, a macroglycol, an internal emulsifier and a chain extender. Polyethylene glycol (PEG; Mw 2000) (supplied by Zhong Shan Mei Bang Nian Ji Co.,Ltd) was used as macroglycol, and it was dried at 110 oC under vacuum during 4 hours to remove residual water. The isophorone diisocyanate (IPDI; provided by Zhong Shan Mei Bang Nian Ji Co., Ltd) was used as diisocyanate. Dimethylolpropionic acid (DMPA; supplied by Guangzhou Guo Cai Pigment chemical industry) was dried at 100 oC during 2 hours in the oven before use as internal emulsifier agent. Isopropyl alcohol (Tian Jin Guang Cheng Chemical Reagent Co., Ltd) was used as chain extender. Hexamethylene diisocyanate (HDI, supplied by Zhong Shan Mei Bang Nian Ji Co., Ltd) used as internal crosslinking agent.
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