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

Abstract

PurposeTo 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/approachTwo 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.FindingsMethods 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/implicationsThe 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 implicationsThe 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/valueThe 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.

Desenvolvimento de biocompósitos de poli(L-ácido láctico) (PLLA) com serragem de madeira

“…O carbamato formado reage com o isocianato, de forma que quanto mais carbamato é formado, mais forte é a ligação do isocianato com a madeira. Entretanto, quando a madeira contém umidade, ocorre uma reação competitiva, pois o isocianato também reage com a água formando a poliuréia, dificultando a formação de carbamato, o que diminui a eficácia na ligação do isocianato com a madeira [34], o que reforça a importância da fase de secagem, anterior à exposição aos isocianatos. Dentre os isocianatos mais utilizados estão o difenilmetano diisocianato (MDI) e o tolueno diisocianato (TDI) [35].…”

Effects of vinyl isocyanate coupling agent on the tensile properties of Kraft fiber‐unsaturated polyester composites

“…Therefore, a VI was proposed in current study to further improve the mechanical properties and mechanical stabilities of Kraft‐reinforced UPE composites via the formations of chemical adhesions between the interfaces of Kraft fiber and UPE resin. Isocyanate is a highly reactive compound that can react with most materials composed of active hydrogen, and therefore, polyisocyanates have been used to prepare polyurethane resin for both bonding and impregnation‐modifying wood 27, 28. Karmarkar et al have successfully grafted an isocyanate called m‐TMI (m‐isopropenyl‐a, a‐dimethylbenzylisocyanate) onto polypropylene as a compatibilizer, which resulted in significant improvement in the tensile and flexural strength of wood‐PP composites 29.…”

Pretreatment of pine needles/wood particles and their composites with isocyanate prepolymer adhesive

“…MDI may react with the hydroxyl groups as well as moisture existed on the surface of pine needles to form urethane (I) and urea linkages (II). It is reported [22] that isocyanate and water have a faster reaction rate than the isocyanate and hydroxyl groups of ligno‐cellulosics. The possibility on formation of cross‐ linked interphase would exist between the reaction products of pretreated fibers and isocyanate terminated prepolymer adhesive (III).…”

“…Isocyanate prepolymer provides the functional groups necessary for curing in the environment. Previously, several studies [6, 7, 19–24] have focused on bonding of polyisocyanates with ligno‐cellulosics with the aim of developing stronger and durable new products. It is commonly experienced that polyisocyanates have sticking problem with a caul plate and thus, causing damage to the surface of composite panels during demoulding [20].…”