Modified Waterborne Polyurethane With High Content Of Acrylate

Polyurethane materials are widely used in adhesives,coatings,rubbers,printing inks,and leather finishing agents because of their excellent overall properties,excellent adhesion on a wide range of substrates,and their ability to adapt to different needs through structural adjustment.In order to maintain good stability of waterborne polyurethane(WPU)in water,it is necessary to add sufficient hydrophilic monomer,but the introduction of hydrophilic groups in WPU film will result in poor water resistance and high cost,so it is limited in practical applications.Acrylate polymers have excellent aging resistance,water resistance,compatibility,and low cost,and are widely used in the field of modified polymers.In this paper,acrylate was used as the modified monomer,and the WPU was modified in multiple steps by block copolymerization,soap-free seed emulsion polymerization and interpenetrating polymer network.First,methyl methacrylate(MMA)and n-butyl acrylate(BA)were used as monomers to synthesize hydroxyl terminated polyacrylate(PA-OH)by mercaptoethanol chain transfer radical random copolymerization,and then block copolymerization was carried out.The PA-OH and WPU blocks were used to prepare polyacrylate block-modified waterborne polyurethane(WPUA)with different amounts of PA-OH.The WPUA dispersion particles were regular spheres from 40 nm to 45 nm and the particle size distribution index was small.The tensile strength.Young’s modulus and elongation at break of the WPUA film were 11.60 MPa,44.11 MPa,636.25%,respectively,and the water absorption rate was 4.60 wt%,which was 53.0%lower than the pure WPU film.The DMA test indicated that some PA-OH entered the soft phase microphase region of WPU and the compatibility was good,some PA-OH entered the hard phase microphase region of WPU and formed hydrogen bonding.The block copolymerization method could solve the compatibility problem between WPU and polyacrylate,and could improve the water resistance and heat stability under the premise of maintaining the mechanical properties of the film.Then,WPUA dispersion was used as the seed,MMA and BA were used as monomers,and the acrylate swelling-block modified waterborne polyurethane(WPUA-PA)with different acrylate dosages were prepared by soap-free seed emulsion polymerization.With the increase of the amount of acrylate in WPUA-PA,the water resistance and heat resistance of the hybrid film were increase.The amount of acrylate in WPUA-PA could reach 12/5 of WPUA,and the water absorption rate was 4.17 wt.%,and the hybrid dispersion still had a certain stability.When the ratio of acrylate to WPUA was 6/5,the WPUA-PA hybrid dispersion particles were regular spheres of 50 nm～80 nm,and the tensile strength,Young’s modulus and elongation at break of the hybrid film were 13.88 MPa,67.58 MPa,and 558.28%,respectively.This indicates that when the amount of acrylate was close to and WPUA,the compatibility between the two was good,and it had excellent stability,water resistance and mechanical properties,compatibility and heat stability.Finally,the WPUA dispersion was used as the seed,the crosslinker glycidyl methacrylate was mixed into acrylate monomer,and the interpenetrating polymer network acrylate modified waterborne polyurethane(WPUA-S-PA)was prepared by soap-free seed emulsion polymerization,studied the effect of crosslinker dosage and different hard monomers on the performance of WPUA-S-PA.With the increase of the amount of crosslinker,the PDI of WPUA-S-PA hybrid dispersion decreased,indicating that the crosslinker had agglomeration effect on the hybrid dispersion latex particles.The deep stained area inside the WPUA-S-PA latex particles was evenly distributed,indicating the formation of IPN structure.With the increase of the amount of crosslinker,the Tg peak of WPUA-S-PA was fused and the strength was increased,indicating that the two polymers formed a single latex particle with good synergy on the microstructure,which proved that successful preparation of IPN type WPUA-S-PA.When the amount of the crosslinker was 5.0 wt%of the total amount of the monomers,the tensile strength,Young’s modulus and elongation at break were 18.25 MPa,62.83 MPa,522.46%,respectively,and the water absorption rate was 4.64 wt%,The WPUA-S-PA hybrid film was excellent in mechanical properties,water resistance and heat resistance.In this paper,the acrylate modified waterborne polyurethane with excellent comprehensive performance was obtained,which not only had the excellent adhesion and flexibility of WPU,but also had the aging resistance and water resistance of polyacrylate,and could reduce the production cost,and broaden the scope of application,providing guiding value for industrial production.