Enhancing the properties of urea formaldehyde wood adhesive system using different generations of core‐shell modifiers based on hydroxyl‐terminated dendritic poly(amidoamine)s

Abstract

Different generations of hydroxy-terminated dendritic poly(amidoamine) (GnAOH) with ethylenediamine as a core were prepared by successive alternative addition of methylacrylate and the core up to the third generation while employing ethanolamine only in the last step of every full generation. The different generations prepared were used as modifiers for urea-formaldehyde (UF) resins. The enhanced durability and stabilizing effect of the (GnAOH)s along with the reduced levels of free formaldehyde and improved mechanical performance of wood joints glued with the modified resins are discussed.

Hyperbranched Poly(amidoamine)s as Additives for Urea Formaldehyde Resin and Their Application in Particleboard Fabrication

“…In brief, this hyperbranched polymer, HB(MA-EDA)3, was not suitable for the modification of UF resins as particleboard binders, at least when it was added as a final additive. This may imply the necessity for starting the modification of UF resins with this modifier in the early steps of the resin preparation to ensure effective insertion into the network structure (Essawy et al 2009;2010;Essawy and Mohamed 2011). To enhance the water resistance of the MUF resin, these reactive PAMAMs were also used as additives to adjust the pH at the end stage instead of using sodium hydroxide, as in a previous study (Amirou et al 2014).…”

“…The highly branched and three-dimensional architecture of these macromolecules have attracted considerable attention in the past few decades (Uhrich et al 1992;Frechet 1994;Inoue 2000). In addition to numerous applications in various fields such as medicine, chemistry, materials science, biology, and physics, there is interest in the use of dendrimers as modifiers for wood adhesives (Essawy et al 2009;2010;Essawy and Mohamed 2011;Zhou et al 2013;. The dendritic poly(amidoamine)s (PAMAMs) are among the most widely used dendrimers as a result of their ready commercialization.…”

“…The dendritic compounds proved to be effective as adhesion promoters for UF resins, which was ascribed in part to the improved wetting over the substrate, a role that is fundamentally related to the great number of functional groups present at the interface. In the case of hydroxyl-terminated dendritic PAMAM (Gn-OH) (Essawy et al 2010), enhanced stability of the modified UF resin along with remarkable reduced levels of free formaldehyde and improved mechanical performance of wood joints were obtained.…”

Degradable Nursery Containers Made of Rice Husk and Cornstarch Composites

“…UF showed peaks of relevance at 1666 cm -1 , 1542 cm -1 , and 1340 cm -1 , which were characteristic of amide I (C=O stretching), amide II (N-H bending), and amide III (C-N and N-H stretching), respectively (Essawy et al 2010). The peak at 1124 cm -1 and its shoulder at about 1022 cm -1 were ascribed to C-H and C-O-C stretching of the carbohydrate fraction in UF, while the broad, strong peak of UF at around 3200 cm -1 to 3500 cm −1 was due to the stretching vibration of the hydroxyl and amine groups in UF (Essawy et al 2010). The O-H and N-H groups in the UF adhesive form inter-and intra-molecular hydrogen bonding with the C=O group of the amidogen in the UF structure.…”

Effect of addition of glycolysis products of poly(ethyleneterephthalate) wastes to urea‐formaldehyde resin on its adhesion performance to wood substrates and formaldehyde emission

“…These fractions showed acid value up to 17.44 mg KOH/g while about 10-folds of equivalent hydroxyl number (174.41 mg KOH/g). The existence of such high hydroxyl number gives rise to their capability to incorporate in the network formation during gelation or crosslinking while the extremely shorter shelf-life (maximum 2 months for most of the samples) relative to our previous studies based on modification of UF resins with dendritic poly(amidoamines) (PAMAM) (14)(15)(16)(17) is ascribed to availability of ACOOH groups in reasonable amount that can selfcatalyze the condensation reactions during storage and therefore shorten the shelf life.…”