Mechanical and Thermal Properties of Waterborne Polyurethane Coating Modified through One-Step Cellulose Nanocrystals/Graphene Materials Sols Method

Abstract

Developing multifunctional coatings with excellent mechanical and thermal properties is highly desirable for wood-based composite application. The recent development of waterborne coatings for wood products suggests that a promising thermosetting material needs to also have properties like low volatile organic contents (VOCs), hardness, and fast curing. The cellulose nanocrystals/graphene materials (CNC/GM) sols were prepared through the one-step method as the thermally conductive and reinforced modifier for preparing waterborne polyurethane (WPU) coatings. The influence of this modifier on the thermal and mechanical properties such as thermal conductivity, abrasion resistance, and adhesion of WPU coatings was investigated. The results indicated that adding CNC/GM sols increased the hardness, abrasion resistance, and thermal conductivity of the WPU coatings, and meanwhile maintained the coating adhesion at the highest grade (level 1). The highest abrasion resistance value of 0.023 g/100 r was obtained for the modified WPU coating when the addition of GM was 3%.

Addition of Graphene Oxide in Different Stages of the Synthesis of Waterborne Polyurethane-Urea Adhesives and Its Influence on Their Structure, Thermal, Viscoelastic and Adhesion Properties

“…Nine et al [32] prepared graphene composite by growth of sodium metaborate crystals at the interface and between the graphene layers during GO reduction intended as fire-retardant coatings for metal and glass, upon which they found good cross-hatch adhesion and high mechanical strength; the enhanced adhesion was ascribed to strong binding between the native oxide layer on the metal surface and the borate groups. Similarly, the mechanical and thermal properties of waterborne polyurethane coatings modified with cellulose nanocrystals and graphene by using a sol method have been studied by Yang et al [33] improved hardness, abrasion resistance, high thermal conductivity, and adhesion. Kale et al [34] mixed a commercial waterborne polyurethane with 0.2 wt % graphene oxide and silica nanocomposites intended for leather coatings and improved mechanical and thermal properties, flexibility, and adhesion were obtained, while the enhanced adhesion was ascribed to improved interfacial interactions.…”

Conductive Biomass Films Containing Graphene Oxide and Cationic Cellulose Nanofibers for Electric-Heating Applications

“…However, the mechanical strength of the films is mainly due to the combined effect of the forces between molecules and hydroxyl bonding. When the amount of GO was increased, the contact surface between the GO molecules increased, although the composite retained the mechanical properties of the cellulose nanofiber membrane [ 27 , 28 , 29 ]. However, when the GO changed from being wrapped by nanocellulose to being partially connected, and cellulose nanofibers did not form a chemical bond, the mechanical performance deteriorated, and the films exhibited brittle fractures during the stretching process.…”

Cellulose Nanocrystals/Graphene Hybrids—A Promising New Class of Materials for Advanced Applications

“…To extend the application of CNC/GN hybrids as anti-static or electromagnetic interference shielding materials, Liu et al have prepared sandwiched films of epoxy resin and GNC/GN paper. Firstly, a hybrid paper of GN containing 10 wt.% of CNC was produced using ultrasonication process in aqueous suspension [147]. This hybrid displayed an electrical conductivity of 16,800 S/m and tensile strength of 31.3 MPa.…”