| Compared with high glossiness coating,the low glossiness coating has the advantages of possessing elegant,soft and natural appearance,and reducing the damage to human’s eyes from reflect light.The requirements for low glossiness coating have gradually emerged.Waterborne polyurethane（WPU）has been widely applied in various fields due to its numerous merits,such as non-toxic,environment-friendly and easy to modify.In recent years,the WPU has attracted extensive attachment in leather finish.In this article,according to the extinction principle,three newly different series WPU extinction resin are designed to avoid the defects of adding extinction powder directly.Additionally,the structure and properties of WPU are also researched.Firstly,dihydroxypropyl terminated polydimethylsiloxane（PDMS）is embedded into the WPU molecule chain via copolymerization,and then organosilicon polymer with low surface energy and excellent hydrophobic properties is adopted to prepare WPU extinction resin（SWPU）.The influence of R value and the content of PDMS on the properties of SWPU emulsion and film are discussed respectively,yielding the optimal dosage.When R is 2.3 and n（PDMS/PTMG）is 2,the precipitation of SWPU emulsion is less and can be dispersed again.Meanwhile,the compact microspheres appear in SWPU film.As a consequence,the 60°glossiness reaches the minimum of10.9 GU,with water absorption of 23%,tensile strength of 3.0 MPa and elongation at break of 204.1%。Then,based on the results above,the sample prepared by the optimal ratio with good stability and integrated performance is chosen as the matrix.The Si O2 is introduced into the main chain by in situ via the crosslinking of the hydroxyl of Si O2and chain segment of WPU.And polymer electrolyte dispersant is added in the process of emulsification.The integrated effects of these two aspects improve the dispersion uniformity and stability of Si O2 with a simple operation and low cost.The introduction of Si O2can further reduce the glossiness.Naturally,the influence of the content of Si O2 on the properties of Si WPU emulsion and film are investigated.When the proportion of Si O2 is 5%,the 60°glossiness reaches the minimum 2.6 GU with the water absorption is 27.2%.Finally,in order to enhance the poor mechanical properties and water resistance of WPU caused by PDMS,hydroxyl-terminated polybutadiene（HTPB）is embedded into WPU chain to modify the resin.Because of the non-polar structure of HTPB,the phase separation of soft segments and hard segments are enhanced to implement extinction effect and improve the mechanical properties.The influence of HTPB content and R value on the properties of HWPU emulsion and film are discussed.When the percentage of HTPB is 20%and R is 1.9,the 60°glossiness reaches the minimum value of 4.1 GU.At the same time,the transparency,water absorption,tensile strength,and elongation at break are 80%,5.4%,25.8 MPa and 781.6%respectively. |
