Preparation and Properties of Waterborne Polyurethane Self-matting Coatings Modified by Bio-based Sporopollenin Exine Capsules
To prepare the waterborne polyurethane(WPU)self-matting coatings,sporopollenin exine capsules(SEC)were dispersed in the WPU emulsion using the physical blending method.The mechanisms of SEC-enhanced WPU were investigated through analyzing surface chemical properties and physical structure characteristics,employing Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),thermogravimetric analysis(TGA),mechanical property testing,surface water contact angle testing,and glossiness testing.SEM results reveal a well-interconnected mesh structure of SEC with the matrix.Further analyses indicate that the tensile properties and thermal performances of SEC/WPU composite materials surpass those of SEC-0/WPU(pure WPU).The tensile fracture strength of SEC-0/WPU is 7.5 MPa.With the adding of SEC,the tensile fracture strength of samples increases.When themassfraction of SEC is 0.46%,the tensile fracture strength of SEC-0.46/WPU is 21.3 MPa.Additionally,the temperature at which the mass retention reaches 70%rises from 320.6℃for SEC-0/WPU to 333.4℃for SEC-0.84/WPU.The incorporation of SEC also reduces the decomposition rates of WPU soft segments,elevating the glass transition temperature(Tg).The Tg of SEC-0/WPU is merely 27.84℃,while the Tg of SEC-0.14/WPU achieves 56.53℃.Compared with SEC-0/WPU,the surface water contact angle of SEC-0.84/WPU increases by 17.6°,while the surface glossiness of SEC-0.84/WPU decreases from 81.4 GU to 6.8 GU,successfully synthesizing the self-matting coatings with outstanding tensile and thermal properties.
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