Synergistic Modification Of Waterborne Polyurethane By Gelatin And β-cyclodextrin

Waterborne polyurethane（WPU）uses water as solvent,which has the advantages of non-pollution,safety and reliability,and easy modification,it can be widely used in coatings,automotive industry,adhesives and other fields.But its poor degradability is gradually gaining attention with the increasing number of related applications.The existing studies have improved the bio-degradability,but reduced the performance of WPU itself.For this reason,considering the application potential of WPU,the biodegradable aqueous polyurethane（β-CD/GV/WPU）was prepared by a prepolymerization method usingβ-cyclodextrin（β-CD）and natural polymeric biomaterial gelatin（GH）for the synergistic modification of WPU,and the research work is as follows:Preparation ofβ-CD/PEG/WPU complexes.WPU was synthesized using polycaprolactone glycol（PCL）and isophorone diisocyanate（IPDI）as soft and hard segment monomers and dihydroxymethylpropionic acid（DMPA）as hydrophilic chain extender.To improve the distribution ofβ-CD in WPU,three different molecular weights of polyethylene glycol（PEG）were used to modifyβ-CD,and the effect of PEG molecular weight on the performance ofβ-CD was investigated,while theβ-CD/PEG complex was later CD/PEG complexes were added to WPU to prepareβ-CD/PEG/WPU composites with hydrogen bonding system.The differences in the properties of pure WPU and each componentβ-CD/PEG/WPU were investigated.The results showed that the modifiedβ-CD/PEG/WPU had good overall performance compared with pure WPU.When the molecular weight of PEG was 1000,the modifiedβ-CD/PEG/WPU obtained had a water contact angle of 88.2°,a maximum thermal degradation rate temperature(T_max)of394.1℃,a maximum elongation at break of 734%,a tensile strength of 51.8 MPa,and degradation rates in 0.6%lipase PBS buffer solution and soil for 60 days of 30.4%and14.2%.Preparation ofβ-CD/GV/WPU complexes.Based on the most comprehensiveβ-CD/PEG1000 as the modified component,vinyl grafted gelatin（GV）was prepared by hydrolytic condensation reaction between vinyltrimethoxysilane（VTMS）and bio-based gelatin,and GV was introduced into the molecular backbone ofβ-CD/WPU by covalent bonding,and the vinyl in GV was cured by photoinitiator and ultraviolet（UV）light.The biodegradableβ-CD/GV/WPU composites with hydrogen bonding system and cross-linked network structure were prepared by linking the vinyl in GV and acrylate ends inβ-CD/WPU under the action of photoinitiator and UV curing.The test results showed that the comprehensive performance ofβ-CD/GV/WPU was optimal when the GV content was1 wt%.Its water absorption and leaching rate were the lowest,14.4%and 11.7%,respectively,and the water contact angle reached the maximum value of 99.1°and the hardness reached 95 HD.the tensile strength was 39.04 MPa and the elongation at break was 582.13%at this time.the T_maxreached 403.4℃from 363.1℃of pure WPU,and the thermal stability performance of the composite film was optimal at this time.The soft satin Tg of the composite was-53.2℃.The degradation rates in soil and 0.6%lipase PBS solution reached 32%and 45.8%in 60 days.