Preparation,property And Modification With Organosilicon Of Self-matting Waterborne Polyurethane

With the changes of people's aesthetic conceptions,matting coatings due to natural appearance and great feel have been widely used in surface finishing process of leather,texture and paper.It is a most commonly used method to introduce matting agents in order to prepare matting coatings,however,matting coatings obtained by this method tend to become fragile,have poor storage stability and cause inhomogeneity of gloss in the surface.Self-matting waterborne polyurethane(WPU)is not only able to meet the environmental demands but also avoid the defects of adding matting agents,which is a product achieving the goal of environmental protection,stability and high performance in a real sense.A series of WPU dispersions in which isophorone diisocyanate(IPDI),poly-1,4-butylene adipate glycol(PBAG),2,2-bis(hydroxymethyl)propionic acid(DMPA)and trimethylol propane(TMP)were all used as raw materials of prepolymer,triethyl amine(TEA)and/or N,N-dimethylethanolamine(DMEA)as neutralizers,2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt(A95)and hydrazine hydrate as post-chain extenders,were synthesized by prepolymer emulsification process.Many instruments such as Zeta potential analyzier,universal testing machine,TG,DMA,SEM,UV-vis,laser nanometer particle size analyzer and gloss meter were used to study effects of variables(i.e.R value,TMP content,DMPA content and A95 content)and DMEA on the properties of WPU,in addition,WPU was modified by organosilicon,there was a method investigated to maintain matting performance and enhance surface hydrophobicity and water resistance for WPU film.The impact of organosilicon on the properties of WPU was investigated as well.Firstly,suitable preparing conditions obtained were that raw materials of polyurethane prepolymer were reacted for 4 hours at 80?,after neutralization process,aqueous solution containing A95 was charged into flask to carry out chain extension and emulsification,finally post-chain extension was conducted by the means of adding hydrazine hydrate dropwise.FT-IR analysis showed WPU dispersion was synthesized successfully by the above process.Secondly,effects of R value,TMP content,DMPA content and A95 content on Zeta potential,water absorption,adhesion,tensile property and thermal property of WPU were studied.It was indicated that,as R value increasing,adhesion(T-peel strength)decreased and brittleness increased.In contrast,adhesion decreased and tensile strength increased with higher TMP content.Moreover,as DMPA content or A95 content increasing,the absolute values of Zeta potential increased significantly,water absorption increased dramatically as well.According to TG analysis,it was found that the heat resistance of WPU film declined with an increase in R value,the results of DMA analysis showed TMP had the capacity of increasing the degree of microphase separation,and WPU samples containing A95 all had the performance of microphase separation at different levels.And then effects of R value,TMP content,DMPA content and A95 content on surface topography,mean particle size,transmittance and gloss for WPU film were studied,the optimal formulation to prepare self-matting WPU was concluded: R value was 1.7~1.9,TMP content was 1%~1.5%,DMPA content was 2.7%,A95 content was 0.5%.What's more,a series of WPU dispersions neutralized by DMEA and TEA containing different amounts of DMPA were synthesized and characterized,it was demonstrated that DMEA had the capacity of enhance and maintain the matting performance of WPU.Finally,organosilicon(i.e.PDMS or KH550)was used to modify self-matting WPU.The results indicated that WPU containing DMEA modified by organosilicon was able to maintain matting performance and enhance surface hydrophobicity and water resistance.The further research suggested that when WPU containing DMEA was modified by PDMS,there was no impact on mean particle size,surface topography,gloss,water absorption and tensile strength,in contrast,transmittance and adhesion both decreased with higher PDMS content,water contact angle increased with an increase in PDMS content.WPU containing DMEA modified by PDMS and KH550,when compared with one modified by PDMS,had many changes which was that mean particle size decreased,spherical granules in film surface disappeared,gloss increased,water absorption decreased,transmittance remained almost unchanged,water contact angle increased,adhesion decreased and brittleness increased.