Preparation,Modification And Properties Of Silicon Containing Waterborne Hybrid Polyurethane

Polyurethane(PUs)is a widely used polymer material.It may display thermoplastic,elastomeric,and thermoset behavior and meet the needs of different occasions depending on their wide variety of raw materials coupled with adaptable synthetic techniques.The conventional PU products in the application of coating and other fields usually contain a large number of organic solvents and as a result large quantities of VOCs are emitted into the atmosphere.Waterborne systems based on PU taking the place of their solvent-borne counterparts has become the general trend.This development is driven by ecological motives or legislation,tangible economic reasons,and the awareness of self-protection.Most aqueous PUs are linear thermoplastic polymers with hydrophilic groups or segments in the main chain in order to disperse excellently in water,which restricts their application.The purpose of this dissertation is aimed to improve the properties and enlarge the applying scope of waterborne polyurethane(WPU).Based on mass optimization of the synthetic process and formula of basic WPU,several kinds of silicon containing waterborne hybrid polyurethane were prepared through the design of chain extender,organic-inorganic composites,and self-crosslinked structure.The film properties and the relationship between structure and properties were systematically investigated.The main research works are as follows:1.Preparation and properties of anionic waterborne polyurethaneTaking the synthesis of basic anionic WPU as the starting point for the formula design.The stability of the dispersions and properties of the corresponding films are used as the evaluation criteria.The key parameters,namely the R(NCO/OH)value,the amount of DMBA,and the degree of neutralization were studied systematically to obtain the optimal synthesis condition.The particle size and stability of WPU dispersions were directly influnenced by the amount of DMBA.The particle size was smaller and the dispersion was more stable with the increase in the amount of DMBA.The R value had a great impact on the particle size,mechanical properties and optical transparency of WPU.The particle size was increased and the mechanical properties of WPU was increased firstly then decreased with the increase of R value.In the optimal case of R = 2.0,the maximum tensile strength was 47.6 MPa.The WPU film had a better optical transparency especially for the lower R value.In the case of R= 1.2,the optical transmittance reached 95%.2.Preparation and properties of WPU with urea-silane side-groups(AWPU)A diol with urea-silane side-chain group(APD-Si)was designed and synthesized and used as the chain extender.We succussefully prepared a series of AWPU dispersions through the selection of alcohol/amine chain extender,the adjustment of DMBA content and R value,and then thoroughly investigated the effect of APD-Si,especially the rigid urea linkage in the side-chain of APD-Si,on the structure and properties of final materials.It was found in the FTIR and DMA results that this extender with crosslinkable silane groups attached to the backbone by urea groups strongly enhances the microphase separation of the hard and soft segments.XPS results indicated that both the self-condensation and the emigration toward the film surfaces of alkoxysilane groups were restricted but mainly in higher APD-Si content.The synergism of the chemical network from the curing of silane and the physical network with the hard segmental domains as the crosslinking points impoved the properties of AWPU.With the addition of 1.5%APD-Si,AWPU film had maximum tensile strength and elongation at break,and their values are 16.2 MPa and 650.4%,respectively.As the amount of APD-Si increased from 0%to 15%,the water contact angle(WCA)increased from 72.9° to 92.4°,the water absorption deceased from 31.2%to 14.6%,pencil hardness increased from H to 4H,and the adhesion increased from 2 level to 0 level.3.Preparation and properties of WPU with ester-silane side-groups(DWPU)In the second chapter,we found that the crosslink of silane side-group was depressed by urea linkage.In order to solve this problem,we designed and synthesized a diol with flexible ester-silane side-groups(DEA-Si)and used it as a chain extender in the systhsis of WPU.Through the selection of alcohol/amine chain extender,the adjustment of DMBA content and the selection of polyol,we thoroughly investigated the effect of DEA-Si on the structure and properties of final materials.The long,flexible alkyl-ester side chain is favorable for the silane components to emigrate toward the film surface and crosslink during the film formation process.The introduction of Si-O-Si crosslink network improved the mechanical properties,water resistance and thermal stability,and it also made the film become more hydrophobic.The results showed that the modulus was 32.6 MPa,the tensile strength was 24.5 MPa,the pencil hardness was 4H,the adhesion was 1 level,the water absorption reduced to 5.8%,the water contact angle increased to 99.3°,and the optical transmittance was above 80%in the range of visible light with the addition of 16.5%DEA-Si.4.Study of DWPU/PSQ composites prepared by blending(BL)method Polysilsesquioxane(PSQ)nanoparticle latex was firstly prepared by the sol-gel process in the presence of emulsifiers.The impact of different kind and amount of emulsifiers,the amount of basic catalyst and reaction temperature on the particle size and stability of PSQ nanoparticle latex were thoroughly studied.Taking the particle size and stability of composite dispersion as the evaluation criteria and optimizing the reaction conditions of pH and temperature,different kinds of PSQ nanoparticle latexs and DWPU dispersion were directly mixed and then cast into films.After that a series of DWPU/PSQ composites were obtained though the hydrolysis and condensation reaction between silane and silanol groups in PSQ and DWPU.Finally we systematically studied the effect of Poly(phenylsilsesquioxane)(PPSQ)content on the structure and properties of DWPU/PPSQ composite film.We found that the modulus increased from 9.5 MPa to 16.8 MPa,the tensile strength increased from 9.6 MPa to 13.6 MPa,the pencil hardness increased from 2H to 3H,the water contact angle increased from 77.3° to 94.0° and the water absorption decreased from 11.9 to 8.6%with the PPSQ content increased from 0%to 20%.5.Study of DWPU/PSQ IS composites prepared by in-situ sol-gel(IS)methodDWPU/PSQ IS composites were firstly prepared by the co-condensation of silane precursor and DWPU and the effect of different kinds of precursor on the properties of DWPU/PSQ IS composites was studied.Then we investigated the effect of the amount of phenyltrimethoxysilane(PhTMS)precursor on the structure and properties of DWPU/PSQ IS composites.With the addition of PhTMS,the crosslink density of the system was increased.The phase separation degree of the composite films was increased firstly and then decreased with the increasing amount of PhTMS.This was attributed to the synergistic effect between the increased thermodynamic incompatibility and crosslink density.Finally,the BL method was compared with the IS method.In IS method,the in-situ generated PPSQ had more chances to form chemical bonds with the polyurethane matrix.As a result,the system had a higher crosslink density.It was found that the self-aggregation and self-migration of PPSQ was restricted by the silsesquioxane crosslinking during the film formation.PPSQ was distributed uniformly in the polyurethane matrix in the form of nanoparticles,which had an impact on the structure and properties of the obtained film.With the load of 20%PPSQ,the IS-20 film prepared by IS method had the pencil hardness of 3H,the flexibility of 2 mm,the adhesion of 0 level,the water contact angle of 83.9°,and the optical transmittance above 80%in the range of visible light.Compared with those of BL-20 film prepared by BL method,the modulus,tensile strength,and water absorption of IS-20 film were increased 2.4%,7.4%,and decreased 10.5%,respectively.