Preparation And Properties Of Photocurable Waterborne Polyurethane Dispersions Hybrided By Nanoparticles

Waterborne polyurethane resin is an important development field listed in Made in China 2025.It is an important film-forming material for water-based coatings and adhesives.In the curing process of waterborne polyurethane resins,chemical crosslinking between polymer molecules is an important way to improve the properties of waterborne polyurethane resin.Among various curing and crosslinking methods,photo-curing process is one of the most common and efficient technology.By means of light-curing,waterborne polyurethane resin can overcome the worse water-resistance and chemical solvent-resistance for single component waterborne polyurethane resin owing to its lower relative molecular weight.Therefore,light-curable waterborne polyurethane resin shows the better research value and application prospects.In the first part,the preparation and properties of a series light-curable water-borne polyurethane dispersions were studied.The effect of hydrophilic agent DMPA content on the appearance and particle size of emulsion was studied.With an increase of DMPA in content,the particle size of polyurethane emulsion was gradually decreased,and the appearance of emulsion showed the gradual change law from the white,to the milky white,the semi-translucent and the transparent.The effect of the relative content of PETA and HEMA on the alkali resistance,gel rate,hardness and mechanical properties of polyurethane film were studied respectively.The results showed that the cross-linking structure of polyurethane film is easier to constructed by the natural light-curing process due to the presence of multi-functionality double bond of end-capping agent,and the correlative properties of the film was improved much.When the molar ratio of PETA to HEMA is about 4:6,the tensile strength of polyurethane film reached the maximum.When the content of compound photo-initiator was 2 wt%,the resin showed the fastest curing rate.In the second part,the compound modification of waterborne polyurethane resin with organic montmorillonite was studied.Na~+-MMT was modified by cationic exchange with self-made cationic polyurethane resins capped by BDO,HEMA and PETA.The intercalation effects of B-OMMT,H-OMMT and P-OMMT were tested by XRD and contact angle tester.The results of XRD showed that the interlayer spacing of B-OMMT was expanded from 1.23 to 1.53 nm,the modification effect was general,the diffraction peaks due to 001 surfaces for H-OMMT and P-OMMT could not be observed,the modification effect is excellent,and the montmorillonite was almost completely exfoliated.The hydrophobic HTPB in the polyurethane used to modify H-OMMT had the best hydrophobicity and the highest contact angle,which were beneficial to the compatibility with polyurethane.The effect of content of H-OMMT on the properties of waterborne polyurethane were investigated.The results showed that when the content of H-OMMT was 1 wt%,the dispersion status of H-OMMT in polyurethane matrix was uniform.The tensile strength of the composite was increased by 12.1%,from 19.9 to 22.3 MPa.The water absorption rate was decreased from10.3%to 5.2%,after soaked in 5 wt%alkali solution for 24 hours.The alkali resistance also was improved significantly.In the third part,the covalent modification of waterborne polyurethane dispersions by MWCNTs was studied.In this thesis,based on the fact of addition reactions of isocyanate groups of toluene diisocyanate with the hydroxyl groups on carbon nanotubes,the surface covalent modification of carbon nanotubes by isocyanate were carried out.The structure and thermal stability of NCO@CNTs were determined by FTIR and TG.The results of FTIR and TG analysis confirmed the rationality of the above modification reaction.The effect of NCO@CNTs content on the properties of waterborne polyurethane film showed that when NCO@CNTs content was 0.3 wt%,the best dispersion of NCO@CNTs in polyurethane matrix was observed.The tensile strength of polyurethane increased by 19.7%from 21.8 to 26.1MPa.Compared with the modification effect of H-OMMT on polyurethane dispersion,the PU hybrid NCO@CNTs showed the better mechanical properties.When the film was soaked in 5 wt%alkali solution for 24 hours,the water absorption decreased from8.7%to 4.1%,and the alkali resistance of the film was also improved significantly.Compared with the polyurethane film modified by H-OMMT,WPU/NCO@CNTs composite film has the better alkali resistance.