Hydroxypropyl Cellulose Films Filled with Halloysite Nanotubes/Wax Hybrid Microspheres

Abstract

The design of novel nanocomposite films based on hydroxypropyl cellulose (HPC) and wax/halloysite hybrid microspheres has been reported. In particular, we first prepared wax/clay Pickering emulsions which were characterized by thermogravimetric analysis and microscopy. SEM images allowed more detailed insights on the nanotubes disposition at the wax/water interface, acting as an outer stabilizing shell. Therefore, the cellulosic biopolymer was added, and it was found that HPC enhances the colloidal stability of the particles, preventing their coalescence and sedimentation. The preparation of the composite films was carried out by the solvent casting method, which enabled the development of very homogeneous materials. Contact angle and sliding angle measurements showed that the increasing amount of wax/halloysite microparticles into the biopolymeric matrix is responsible for an enhanced hydrophobic nature of the films and, at the same time, it facilitates the rolling process of droplets on the surfaces, thus making the prepared materials promising protective coatings. These findings were also confirmed by the decrease of the vapor permeability of the nanocomposites, which can act as a gas barrier. Moreover, the effect of the composition on the optical properties, namely transparency and colorimetric features, was investigated together with the thermal properties of the films. Results demonstrated that the presence of wax/halloysite microspheres as fillers within the HPC matrix has profound effects on the prepared systems, which were evaluated to be good energy storage and heat reservoir materials. In light of these aspects, the new HPC/wax/halloysite nanocomposites represent promising tools for the surface modification.