Synthesis And Properties Of Aqueous Polysiloxane-block-polyurethane Copolymer

Both in academic and industrial area, it has been a worldwide target to use waterborne polymers for fabric treating. However, poor water resistance, washability and bonding capacity with the fabric of these polymers restricted their applications. In this dissertation, aqueous polysiloxane-block-polyurethane copolymer was synthesized. The good flexibility of the siloxane segments and the perfect water resistance of the polysiloxane would improve the hydrophilic surface and the poor washability of the polyurethane, which would widen the application in fabric finishing.Waterborne polyurethane dispersion was synthesized by self-emulsification process with importing polar groups, and then the aqueous polysiloxane-block-polyurethane copolymer was produced by adding the polysiloxane segments. Aqueous polysiloxane-block-polyurethane copolymer was synthesized by two steps: the first is the synthesis of isocyanate-ended prepolymer from polyol and isocyanate, and the second is the reaction with amine-ended siloxane.To obtain the block copolymer with good stability, hydrophobic surface and other good properties, the influence of the kinds of polyol, the structure and content of the hydrophilic groups, the molecular weight and content of the polysiloxane and the polymer concentration on the particle size, viscosity and stability of the dispersion and the swelling ratio, contact angle, thermal stability and mechanicai property of the film was studied.It was found that it would improve the water resistance and mechanical property of the film to mix castor oil into polyol. The influence of polyol with melecular weight 1000(N210) and 2000(N220) on the propertie of emulsion and film was also examined. Using N210 as the soft segments, there was lower swelling ratio and higher surface contact angle, which endowed the film good water resistance; while using N220 as the soft segments, there was higher elongation at break and lower hardness of the film, but large partice size and poor stability of the dispersion.As the component containing hydrophilic group, glycerine semi-ester was cheaper. There was good softness of the film but poor stability of the dispersion made by glycerine semi-ester. 2,2-Bis(hydroxymethyl)propionic acid(DMPA) was more espensive, but it costed less amount to obtain good stability of the dispersion. There existed two-sided influences of the carboxyl. As the content of the carboxyl increased, there were smaller particle size and better stability of the emulsion, and also better mechanical property for the film, while there was an increase in the swelling ratio and worse water resisitance.The molecular weight of the polysiloxane existed the similar influence on the properties of the dispersion with the increase of polysiloxane content. As the molecular weight or the content of polysiloxane increased, the viscosity of the dispersion increased, the water resisitance, the tensile strength and the hardness of the film enhanced, while the elongation at break decreased. As the polymer concentration increased, the particle size and the vicosity increased. Furthermore, as the polymer concentration of the block copolymer dispersion exceeded 30%, the dispersion exhibited the behavior of shear thinning which means perfect paintability.It is concluded that this work is to use castor oil instead of part of polyol as the soft segments and take the amine-ended polysiloxane instead of the siloxane coupling agent. The water resistance and the mechanical property of the dispersion was improved and the cost was also decreased.