Nanocomposites made from thermoplastic waterborne polyurethane and colloidal silica. The influence of nanosilica type and amount on the functional properties

• Published in: Progress in organic coatings 2016-12, Vol.101, p.342-349
• Main Authors: Serkis, Magdalena, Špírková, Milena, Hodan, Jiří, Kredatusová, Jana
• Format: Article
• Language: English
• Subjects: Colloids; Crosslinking; Dispersions; Elongation; Hydrogen bonds; Hydrogen storage; Ludox (trademark); Mechanical properties; Microstructure; Microstructures; Modulus of elasticity; Nanocomposites; Nanostructure; Polycarbonate resins; Polycarbonates; Polymer matrix composites; Polymer-matrix composites (PMCs); Polyurethane; Polyurethane resins; Silicon dioxide; Thermal analysis; Thermoplastic resins; Water resistance
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2016.07.021

[Display omitted] •Novel nanocomposite coatings based on polyurethane/colloidal silica water dispersions were prepared.•The influence of commercial silica type on nanocomposite film properties was investigated.•Silica Ludox AS, less hydrophilic and smaller than Ludox TMA, revealed better improvement of mechanical, thermal and swelling resistance of the coatings.•Obtained nanocomposite films are linear materials, possible to recycling. Novel waterborne polyurethane/silica nanocomposites were prepared via blending of two aqueous dispersions. Polyurethane water dispersion (PUD) was synthesized from polycarbonate diol (PC), 1,6-diisocyanatohexane (HDI) and butane-1,4-diol (BD) in order to provide solely linear character of PU chain. Two types of commercial colloidal silica, Ludox AS and Ludox TMA, differing in the size, shape and type of counter ions were used. The nanocomposites were made from negatively charged PUD and aqueous nanofiller sol at concentrations 5, 32 and 50wt% of nanosilica. The films were obtained after slow drying of the water mixtures and characterized by AFM, SEM, tensile testing, DMTA, TG and water uptake measurements. It was found that all films are thermoplastics materials, reinforced by hydrogen bonds between silica particles and the polymer matrix, soluble in organic solvents and possible to re-production of PUD. Ludox AS was smaller than TMA and revealed better improvement of PUD-based films due to higher physical cross-linking density. It was observed that film containing 32wt% of silica Ludox AS showed ten-times increasing Young’s modulus with slight improvement of elongation at break and two-times higher melting temperature in comparison to the neat PU matrix. Moreover sample with 5wt% of AS nanofiller loading revealed excellent water resistance (swelling 0.8%). The obtained PU/silica nanocomposites have promising applications in recyclable environment-friendly waterborne coatings.