Preparation and properties of environmentally benign waterborne polyurethane composites from sodium-alginate-modified nano calcium carbonate

Abstract

Well-dispersed inorganic nanoparticles in organic polymers are critical in the preparation of high-performance nanocomposites. This study prepared a series of waterborne polyurethane (WPU)/calcium carbonate nanocomposites using the solution blending method. Next, FT-IR, TG-DTG and XRD tests were carried out to confirm that the biopolymer sodium alginate (SA) was successfully encapsulated on the surface of the calcium carbonate nanoparticles, and that SA achieved satisfactory surface modification of the calcium carbonate nanoparticles. The Zeta and ultraviolet (UV) absorbance test results reveal that SA-modified nano calcium carbonate(MCC) had good dispersion stability in water. The effects of the MCC dosage on the composite mechanical properties, thermal stability, and cross-sectional morphology observed by scanning electron microscopy (SEM), and the water resistance of the nanocomposite were investigated. The results reveal that the incorporation of 3wt% of MCC in WPU had stable distribution, which led to a 54% increase in the tensile strength of the nanocomposite, while maintaining excellent elongation at break (2187%) and increasing the maximum decomposition temperature to 419.6 °C. Importantly, the improved water resistance facilitates the application of this environmentally benign composite material in humid environments.

Preparation and properties of water‐borne polyurethane‐sodium lignosulfonate/nano‐calcium carbonate composites

“…21 This allows it to remain relatively stable in water due to the electrostatic repulsive forces and spatial site resistance created by negative charges between each particle. 13 As shown in Figure 2, the stability of CaCO 3 /SL dispersion was effectively improved compared with nano-CaCO 3 . The higher the absolute value of the zeta potential at different ratios of CaCO 3 /SL, the longer it takes for CaCO 3 /SL to settle entirely in water.…”

“…The reason for this is that, as an anionic surfactant, SL adsorbs on the surface of CaCO 3 nanoparticles and provides a significant amount of negative charge 21 . This allows it to remain relatively stable in water due to the electrostatic repulsive forces and spatial site resistance created by negative charges between each particle 13 …”

“…These new peaks were observed in the same position as diffraction peaks of nano‐CaCO 3 , and the intensity of the diffraction peaks near 2 θ = 18° decreased as the amount of compounding increased. The reason for this is that the doping of CaCO 3 /SL influenced the amorphous structure of the films, 13 indicating the successful preparation of WPU‐CaCO 3 /SL composite films.…”

“…The reasons for the increase in water contact angle can be explained as follows: (1) The addition of CaCO 3 /SL prevents water diffusion. 13 With the gradual increase of the CaCO 3 /SL composite, the cross-linking density between the WPU molecules increases. The nanoparticles fill the voids between the polymers, which makes the film dense; the free volume declines, and it becomes difficult for the water molecules to penetrate the film's interior.…”

“…Wang et al 12 prepared a sodium lignosulfonate/calcium carbonate nanoparticle composite filler by dry milling and incorporated it into polypropylene, which improved the elongation at break, impact strength, and thermal stability of the polypropylene. Yuhang et al 13 used sodium alginate (SA) to modify the nano‐CaCO 3 , and prepared WPU nanocomposites with different doping levels of modified nano‐CaCO 3 . They found that the modified nano‐CaCO 3 had good compatibility and dispersion between the modified nano‐CaCO 3 and the WPU films, which improved their water resistance and mechanical strength.…”