Research Of Preparation And Modification Of Bio-based Waterborne Polyurethane

Polyurethane(PU)generally refers to polymeric compounds containing repeated unit of carbamate bond in the main chain.Organic solvents are usually applied as the dispersing agent in traditional PU making techniques,however,along with the strengthening of people's environmental protection awareness,waterborne polyurethane(WPU)is gradually replacing solvent-based polyurethane because of its low toxicity,excellent mechanical properties and low volatility.Biomass is one of the renewable resources.Making adequate use of this resource will have a positive impact on the society.Thermochemical conversion is one of the most powerful methods in the biomass utilization,where biomass liquefaction by polyols has been deemed to be promising technology.The liquefaction process can significantly improve the value of biomass.The innovation of this research was using biomass liquefaction products as raw materials for the PU production.Bamboo shoot shell(BSS),a kind of typical wood biomass,hold many advantages,such as high yield and short growth cycle,was chosen as biomass material for liquefaction.BSS was liquefied in polyethylene glycol 400(PEG400)and ethylene glycol(EG)mixture catalyzed by 5wt%H2SO4 under atmospheric pressure at 150 ?.Then,using poly,isocyanate and biomass liquefaction products as fundamental monomers,2-bis(hydroxymethyl)propionic acid(DMPA)as hydrophilic chain-extender,and dibutyltin dilaurate(DBTD)as catalyst,bio-based WPU(BWPU)were prepared through the pre-polymer dispersion process.Firstly,the optimal preparation conditions of waterborne polyurethane were explored.Using the content of NCO%as the main criterion,the reaction condition of the first step of the pre-polymer dispersion process was reaction temperature,70?;reaction time,100 min,while that of the second step of the pre-polymer dispersion process was reaction temperature,80 ?;reaction time,100 min.Secondly,the biomass liquefaction product was added into the reaction system to prepare BWPU,and the optimal preparation conditions were studied.Solid content and stability of emulsion,and water resistance,heat resistance and mechanical properties of the film were tested respectively.Results showed that solid content of emulsion was proved to be between 28%and 35%,and the film's biggest contact angle reached 93.7°.Thirdly,modification research on WPU was conducted.KH550 were used as the modifier of WPU,and the optimal addition of KH550 was 2.5%.After the organosilicon modification,water-absorption of the film decreased from 40.0%to 22.28%,elongation at break reached 492%,and the temperature of 50%weight loss increased from 340.349 ? to 352.853 ?.Finally,in order to validate the universality of the preparation method of biological based waterborne polyurethane concluded in this study,bamboo sawdust,peanut shell,and sugarcane bagasse were liquefied and studied.The liquefaction yield was 99.69%,88.23%,and 96.58%,respectively.Each liquefaction product could be used as fundamental monomers to prepare biological based waterborne polyurethane with satisfactory performance.Four kinds of biomass liquefaction products were successfully made into BWPU respectively in this study,broadening the utilization way of biomass liquefaction product and indicating that the method of BWPU preparation in this study has potential application prospect.