Improved water resistance, thermal stability, and mechanical properties of waterborne polyurethane nanohybrids reinforced by fumed silica via in situ polymerization

Abstract

In this study, a series of waterborne polyurethane/fumed silica (WPU/S) hybrids were prepared by an optimized in situ polymerization through a grafting process. Fourier transform infrared spectrum and X-ray diffraction confirmed the enhanced interfacial interactions between fumed silica particles and polyurethane (PU) segments. Atomic force microscopy demonstrated well dispersion of fumed silica in PU matrix and the rough surface of WPU/S hybrid films, which contributed to improved water resistance. The thermal stability of WPU was also improved by the incorporation of fumed silica, and the glass transition temperature of WPU/S increased compared with pure WPU. Moreover, as the content of fumed silica increased from 0% to 4%, the tensile strength of WPU/S increased from 29.0 MPa to 37.6 MPa without losing high elongation at break.

Analyzing the influence of different synthetic talcs in waterborne polyurethane nanocomposites obtainment

“…The results of R a , R q , and R max demonstrates that with fillers addition the surface roughness of the nanocomposites increased, indicating the fillers influence on the surface morphology of the systems. As seen in Figure , with the addition of fillers on the nanocomposites the rugged domains come more prominent evidencing the interactions between filler/polymer probably by hydrogen bonding among fillers and hard segments of the WPU . This interactions corroborates the mechanical properties improvements in nanocomposites once compared to pristine WPU.…”

“…Nevertheless, WPU have some disadvantages as low thermal–mechanical properties, low adhesion, low drying rate, and so on . The incorporation of inorganic particles in the WPU matrix is a solution to improve its physical–chemical properties . Organic–inorganic nanocomposites have been widely discussed, improvements promoted by nanofillers are frequently associated to their concentration, shape, size, degree of aggregation, surface area, degree of dispersion, and the interaction between nanofiller/polymer .…”

“…Dispersed nanofillers improve physical/chemical properties of nanocomposites such as mechanical strength, conductivity, thermal stability, and optical properties . Literature describes that different fillers have been introduced into WPU such as silver nanoparticles, halloysite nanotubes, metallic oxides, graphene, silica, nanoclays, nano‐Fe 3 O 4 , and cellulose nanocrystals . Talc is also a good alternative due to its low cost and availability.…”

Effect of phase separation on water resistance of green waterborne polyurethanes: Unexpected stronger impact compared to hydrophilic segments

“…[1][2][3][4][5][6] As a significant characteristic of PUs, phase separation has been studied extensively through the application of differential scanning calorimetry, dynamic mechanical analysis (DMA), infrared spectroscopy, small angle X-ray scattering, transmission electronic microscope, scanning electronic microscope, and atomic force microscope. Therefore, water resistance (hydrophobicity, always defined by water absorption ratio and water contact angle [28][29][30] ) is one of the most important properties of WPUs which strongly affect the performance of WPU materials. [15][16][17][18] Waterborne PUs (WPUs) are one of the most prosperous branches of polymer materials because of their adjustable molecular structures, excellent properties such as low-temperature resistance, high tensile strength, and high flexibility, and environmentally friendly characteristic compared with solvent-borne PUs.…”

“…[7][8][9][10][11][12][13][14] And a large number of studies investigated the relationship between phase separation and mechanical properties of PUs, disclosing that the excellent mechanical properties of PUs should be ascribed to phase separation. [28][29][30] Xu et al [20] prepared a WPU and reported that the water resistance of WPU films was highly affected by the content of dimethylol propionic acid (DMPA) which used as an internal emulsifier (hydrophilic segment). [19][20][21][22][23] They have been used widely in many fields like coatings, inks, adhesives, and leather finishings.…”