Preparation And Film Properties Of Waterborne Polyurethane/Acrylate Silicone Modified With Chitosan

In recent years, as people’s awareness of environmental protection, non-VOC waterborne polyurethane became a hot topic of domestic and foreign research scholars. In this paper, in-situ surfactant-free polyurethane/acrylate(IPUA) disperaions were synthesized by isophorone diisocyanate(IPDI),polycaprolactone diol(PCL1000) and dimethylol butanoic acid(DMBA). IPDI as hard segment in polyurethane, PCL1000 as soft segment and DMBA as chain extender. At the same time, butyl acrylate(BA) and methyl methacrylate(MMA) as the main raw material for preparing polyacrylates, hydroxyethyl methacrylate(HEMA) as the coupling agent added in this system. Then, some crosslinking agent or chain extender with functional group –OH or –NH2 was added in the system. The series of dispersions taking advantage of the reaction between-NCO and –OH or –NH2, without any organic solvent and synthesised by in-situ surfactant-free emulsion polymerization. The main content of this paper was as follows:(1) γ-(methacryloyloxy) trimethoxysilane(KH570) was utilized as coupling agent, effects of hard and soft segments ratio in PA and KH570 content on the properties of films were investigated. It was found that when BA/MMA was 7:5(mass ratio), the average particle size of IPUASi dispersions ranged from 95.51 nm to 50.23 nm with KH570 content increased to 10%. Rheological properties of dispersions showed that the emulsion exhibits Newtonian fluid behavior when BA/MMA was 7:5. When KH570 content was less, the emulsion was pseudoplastic fluid behavior, but when more content, the emulsion was Newtonian fluid behavior. Atomic force microscopy(AFM) confirmed that the surface roughness of films was lower to 16.82 nm when BA/MMA was 7:5, and the surface roughness of films increased with increasing of KH570 content. X-ray photoelectron spectroscopy(XPS) confirmed that the Si element tends to film surface enrichment. In addition, with increasing KH570 content, the mechanical properties and thermal stability of films were improved. The water absorption of films discreased to lowest value when BA/MMA was 7:5 and KH570 content was 10%.(2)Used hydroxyl-terminated polysiloxane(HPMS) as chain extender, effects of HPMS content on the emulsion and properties of films were investigated. FT-IR and NMR indicated the presence of Si-O bond on the polymer chains. Dynamic light scattering showed that the average particle size of HPMS/IPUA dispersions range from 58.14 nm to 96.32 nm with the increase of HPMS content. Transmission electron microscope(TEM) showed too much HPMS content made the latex particles bonded. Rheological properties of dispersions showed that the polyurethane/acrylate emulsion modified by HPMS was non-Newtonian fluid and showed pseudoplastic behavior. The system of HPMS/IPUA was dominated by elastic behavior. AFM confirmed that the surface roughness of films was increased with increasing HPMS content because the poor compatibility between polyurethane segments and polysiloxane segments. XPS confirmed that the Si element tends to HPMS/IPUA film surface enrichment. Moreover, the mechanical properties of HPMS/IPUA films increased with the right amount of HPMS. The data of water absorption proved the minimum value was reached when the HPMS content was 1.2g.(3)Used chitosan(CS) as a cross-linking agent, effects of CS content and molecular weight on the emulsion and properties of films were investigated. Dynamic light scattering showed that the average particle size of CS/IPUASi dispersions increased with increasing CS content, as well as CS molecular weight. TEM showed that the core-shell structure was more blurred with the increase of CS content when the CS molecular weight was smaller. It was also found that too much CS content made the latex particles bonded when the CS molecular weight was larger. The results of rheological properties of the CS/IPUASi showed that the system was dominated by elastic behavior. The viscosity results of emulsion indicated that the viscosity of dispersions increased and showed pseudoplastic behavior with the same CS molecular weight and increased CS constant. When CS content was 0.5g, the molecular weight had little effect on the viscosity of emulsions. However, When CS content was 1.0g, the viscosity of emulsions increased with the increase of CS molecular weight. XPS results showed that N element content in hard segment had little change when the depth was lighter. The results of AFM showed that the surface roughness increased after polyurethane modified by CS. TGA results showed that CS improve the thermal stability of films. In addition, the mechanical properties of CS/IPUASi films increased with the right amount of CS. Water resistance test results showed that the right content and molecular weight of CS decrease the water absorption of films and the water resistance improved.