Polyurethane Wood Adhesives Prepared from Modified Polysaccharides

Abstract

This study investigated the performance of polyurethane adhesives prepared with various combinations of wheat starch that had been modified by isophorone diisocyanate (MS), two polyol types (1,3-propanediol (PD) and glycerol (Gly)), native wheat starch (NS), and 4,4′-diphenylmethane diisocyanate (pMDI) at a NCO:OH weight ratio of 1:1. Two more adhesives were also synthesized with NS, PD, or Gly and pMDI blends and served as controls. The thermal behavior of the adhesives before and after the curing process, as well as their rheological performance and lap shear strength, were analyzed. Differential scanning calorimetry (DSC) showed a reduction in curing temperature and heat by adding MS. The thermal stability of the cured adhesives was slightly increased by MS addition. The viscosity of the adhesives that contained MS substantially increased at a linear ascendant ramp of shear, while the controls exhibited relatively low viscosity during the whole shear rate spectrum from 0.1 to 100 s−1. The tensile shear strength of wood veneers was also significantly increased by the incorporation of MS under both dry and wet measuring conditions. The maximum dry shear strength was obtained for the adhesive with Gly polyol and a higher content of MS and was comparable to the control adhesive with pMDI.

A dialdehyde starch-based adhesive for medium-density fiberboards

“…It is extensively used in many industrial sectors, such as food, textile, pharmaceutical, paper, and biofuel. However, the use of starch in the wood industry presents limitations, mainly related to viscosity issues, storage stability, and bonding capacity (Hosseinpourpia et al 2022). Chemical modification of starch polymer (crosslinking, acid hydrolysis, oxidation, etherification, esterification, cationization, and polymer grafting) has been employed for improving the starch properties and make it a competitive biopolymer for wood bonding (Hemmilä et al 2017;Hosseinpourpia et al 2018;Chen et al 2021;Hosseinpourpia et al 2021Hosseinpourpia et al , 2022.…”

Synthesis and Mechanical Performances of Polyurethane Bio-Based Adhesives Resulted from the Depolymerization of Lignocellulose Biomass

“…19 The main issue concerning these products is related with the formaldehyde-based formulations that are proven to affect the environment and human health due to the formaldehyde emissions. 19 Thus, bicomponent PUR adhesive chemistry is nowadays in a transition to formaldehyde-free adhesives in which polyols (component A) can be manufactured from renewable resources. 20 In terms of PUR wood adhesives, the mechanical performances are strongly related to the conditions necessary to obtain bio-polyols with suitable properties such as hydroxyl number or viscosity.…”

“…15,17 Regardless of their chemical structure, the global market for adhesives is predicted to approach 21 billion USD by 2024. 19 The main issue concerning these products is related with the formaldehyde-based formulations that are proven to affect the environment and human health due to the formaldehyde emissions. 19 Thus, bicomponent PUR adhesive chemistry is nowadays in a transition to formaldehyde-free adhesives in which polyols (component A) can be manufactured from renewable resources.…”

“…Regardless of their chemical structure, the global market for adhesives is predicted to approach 21 billion USD by 2024. 19 The main issue concerning these products is related with the formaldehyde-based formulations that are proven to affect the environment and human health due to the formaldehyde emissions. 19 …”

“… 19 The main issue concerning these products is related with the formaldehyde-based formulations that are proven to affect the environment and human health due to the formaldehyde emissions. 19 …”