FTIR and XPS study of the reaction of phenyl isocyanate and cellulose with different moisture contents

Purpose - To evaluate the competing reaction of isocyanate with cellulose and water which can provide direction for further studies on bonding and curing reactions of isocyanate with wood. Design/methodology/approach - Two modern analytical techniques, Fourier transform infra-red (FTIR) and X-ray photoelectron spectroscopy (XPS), were used. The FTIR was used to identify the products of the reaction of phenyl isocyanate (PI) with alcohol, water, and cellulose; while the XPS was used to evaluate the proportions of isocyanate that reacted with water or cellulose when PI reacted with cellulose at different moisture contents (MCs), respectively. Findings - Methods for the IR identifications of reaction results of PI with n-propanol, water, and cellulose, in which the reactions of PI with water and PI with cellulose resulted in N,N'-diphenylurea and carbamate, respectively, were developed. It was discovered that the extent of reaction of isocyanate and cellulose decreased with increasing cellulose MC, and 92.98 per cent isocyanate reacted with water when 9.78 per cent MC was reached. It was confirmed that the products of the PI reaction were distributed mainly on the surface of the cellulose particles. Research limitations/implications - The study only focused on the reaction of PI. However, the industrial isocyanates, e.g. methylene diphenyl diisocyanate (MDI), polymerized methylene diphenyl diisocyanate (p-MDI) that have complexities in chemical structures and components, make analyses with FTIR and XPS impossible. Practical implications - The paper provides some instructive information about the isocyanate reaction that will help understanding the characteristics of isocyanate and guiding the design of technology bonding isocyanate to fibre, wood, etc. Originality/value - The application of FTIR and XPS for evaluating the reaction of isocyanate with cellulose having different MCs was novel and may be used as a reference for other relevant studies.