Synthesis of bio-based polyurethanes with simultaneous film formation: Use of SiO2 nanoparticles and blankets obtained by blow spinning from solution to add properties to the films

Abstract

Using lignocellulosic biomass components for developing bio-based materials is increasingly important, given the growing need to replace raw materials from fossil sources to support environmental sustainability. This project aims to synthesize bio-based polyurethanes using polyols derived from vegetal biomass. These polyols include microcrystalline cellulose (MCC) or Kraft lignin (LK), and ricinoleic acid triglyceride (the primary component of castor oil, CO), along with the hexamethylene diisocyanate (tHDI) trimer. The synthesis entails simultaneous film formation without the use of solvents and catalysts. MCC was selected for its average molar mass (approximately 20,000 g/mol), making it suitable for use as a "macromonomer," while LK was chosen due to its abundance in the country as a byproduct of the wood pulping process, and CO for its potential to act as an additional polyol and aid in dispersing solid reactants in the reaction medium. The reaction mixture will be spread on a glass plate using an extender, and films will form simultaneously at the end of the reaction.The reaction will take place at room temperature or above, as needed. The films may or may not include SiO2 nanoparticles (NPs-SiO2) due to their potential antibacterial properties, essential for applications such as dressings and packaging. The decision to add NPs-SiO2 influenced the selection of tHDI, a low-viscosity isocyanate that aids in dispersing the nanoparticles in the reaction medium. It is also intended to prepare mats made up of submicrometric or micrometric fibers using the solution blow spinning (SBS) technique. Bio-based polyurethanes will be synthesized by seeking polymers soluble in volatile solvents, as is necessary for SBS application. These fiber mats will be layered between films to form composites to evaluate their performance as reinforcements, particularly in enhancing tensile properties. The use of polyurethanes in both the films and mats should promote strong intermolecular interactions at the mat/film interface, leading to improved adhesion, which usually positively impacts the properties of composites. Part of the mats will be prepared with NPs-SiO2 rather than adding the NPs to the films. This approach may make it difficult for the NPs to migrate outside when in possible applications. The films will undergo characterization via infrared spectroscopy (IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for morphological evaluation (TEM will be used when NPS-SiO2 is present), and ultraviolet-visible spectroscopy to study optical properties. Other analyses include assessing the presence of charges on the surface with water via zeta potential, determining hydrophilic/hydrophobic characteristics through contact angle (CA), and measuring tensile properties and glass transition temperature (Tg) using dynamic mechanical analysis (DMA). Furthermore, crystallinity will be evaluated using X-ray diffraction, and antibacterial properties will be assessed. The mats will be characterized using IR, SEM, TEM, zeta potential, DMA, and tensile properties. Further characterizations may be deemed suitable as the project progresses. The outcomes obtained will facilitate a more comprehensive identification of potential applications. As far as is known, the approach of this project is unprecedented.