Novel Isocyanate Binder Systems for Composite Wood Panels

Abstract

The growing demand for structural composite wood panels has created an opportunity for novel cost effective binder systems. Recently, much data has been published extolling the virtues of isocyanates (PMDI) as binders for composite wood panels intended for exterior applications. To date, there are two main drawbacks which inhibit the wide spread use of PMDI as binders: 1) generally, isocyanates are more expensive than the commonly used formaldehyde binder systems and 2) isocyanates adhere strongly to the caul plate during the pressing cycle. To overcome this sticking problem, release agents are necessary which increases the overall cost of an isocyanate binder system. This study was undertaken to investigate the cost/performance of isocyanate binder systems which incorporate significant levels of low cost reactive diluents. Several binder systems were evaluated which were cost/performance effective when compared to phenol-formaldehyde (exterior) and urea-formaldehyde (interior) binders for composite wood panels.Laboratory studies have demonstrated that propylene carbonate (PC) is one such effective diluent in conjunction with isocyanates. The data indicates that acceptable composite wood panels, both exterior and interior grade, can be pro-This paper was presented at The Downloaded from 207 duced even when 30% of the isocyanate is replaced by propylene carbonate. Economical analyses indicate that the 70% PMDI/30% PC binder system offers cost advantages over 7% phenol-formaldehyde (PF) or 9% urea-formaldehyde (UF) binder systems.

Nanocellulose in Heterogeneous Water-Based Polymerization for Wood Adhesives

“…The main advantage of this adhesive is that it can be used at much lower adhesive loads for the same results, which compensate its higher price compared to PF adhesives. pMDI adhesives offer additional benefits, including a high reactivity, fast curing, excellent dry/wet bonding strengths, and good tolerance to substrate moisture content [94], decreasing thickness swelling, and providing high flexural strength to OSB, laminated strand-lumber, and exterior particleboard [95]. Most of the research done in this area has utilized the physical method for mixing CNPs and isocyanate adhesives.…”

Adhesives made from isocyanates and pyrolysis oils for wood composites

“…The study of Rosthauser (2001) was a starting point of the work presented here. Gaul et al (1984) made particleboard blended with low viscosity hybrid mixtures of pMDI with propylene oxide and propylene carbonate. Economics indicated that particleboards blended with 3.5% of the 30% propylene carbonate/pMDI binder system are competitive with particleboards containing 7% of a commercial PF or 9% of a commercial urea-formaldehyde (UF) adhesive.…”

“…Preliminary tests were done with 40% PO content hybrid adhesive to choose the right quantity of adhesive for the particleboard in order to obtain acceptable mechanical properties. Particleboards were made using between 2% and 6% adhesive content (based on oven-dry wood basis, including the amount of water already in the PO oil), reflecting the work of Rosthauser (2001) and Gaul et al (1984), where adhesive content used was 3-8%.…”

Lignin as a Key Component in Lignin-Containing Cellulose Nanofibrils for Enhancing the Performance of Polymeric Diphenylmethane Diisocyanate Wood Adhesives

“…17 Polymeric diphenylmethane diisocyanate (pMDI) has gained a large market share as it is a formaldehydefree wood adhesive and it offers additional benefits, including high reactivity, fast curing, excellent dry/wet bonding strengths, and good tolerance to substrate moisture content. 18 T h i s c o n t e n t i s However, pMDI can deeply penetrate into the wood substrate, which sometimes results in a starved bondline, and this drawback limits the broader applications of pMDI in making, for example, plywood where a continuous bondline is required. 19 With regard to this challenge, our previous findings demonstrated the good promise of developing strong adhesion performance of pMDI wood adhesives by incorporating LCNFs (Klason lignin content of 22 wt %); LCNFs not only served as a medium to close the gaps between the adhesive layer and the wood substrate layer but also reinforced the resulting continuous bondline by having interactions with the cured pMDI network.…”

“…However, since formaldehyde was labeled as a human carcinogen, formaldehyde-free adhesives are gradually taking over the market, especially for indoor applications . Polymeric diphenylmethane diisocyanate (pMDI) has gained a large market share as it is a formaldehyde-free wood adhesive and it offers additional benefits, including high reactivity, fast curing, excellent dry/wet bonding strengths, and good tolerance to substrate moisture content …”