Several fungal laccases have been compared for the oxidation of a nonphenolic lignin dimer, 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)propan-1,3-diol (I), and a phenolic lignin model compound, phenol red, in the presence of the redox mediators 1-hydroxybenzotriazole (1-HBT) or violuric acid. The oxidation rates of dimer I by the laccases were in the following order:Trametes villosa laccase (TvL) > Pycnoporus cinnabarinus laccase (PcL) > Botrytis cinerealaccase (BcL) > Myceliophthora thermophila laccase (MtL) in the presence of either 1-HBT or violuric acid. The order is the same if the laccases are used at the same molar concentration or added to the same activity (with ABTS [2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)] as a substrate). During the oxidation of dimer I, both 1-HBT and violuric acid were to some extent consumed. Their consumption rates also follow the above order of laccases, i.e., TvL > PcL > BcL > MtL. Violuric acid allowed TvL and PcL to oxidize dimer I much faster than 1-HBT, while BcL and violuric acid oxidized dimer I more slowly than BcL and 1-HBT. The oxidation rate of dimer I is dependent upon bothk cat and the stability of the laccase. Both 1-HBT and violuric acid inactivated the laccases, violuric acid to a greater extent than 1-HBT. The presence of dimer I or phenol red in the reaction mixture slowed down this inactivation. The inactivation is mainly due to the reaction of the redox mediator free radical with the laccases. We did not find any relationship between the carbohydrate content of the laccases and their inactivation. When the redox potential of the laccases is in the range of 750 to 800 mV, i.e., above that of the redox mediator, it does not affectk cat and the oxidation rate of dimer I.

This study investigated a new adhesive system, consisting of soy protein isolate (SPI) and Kymene ® 557H (simply called Kymene) (a commercial wet-strength agent for paper), that was prepared by mixing SPI and Kymene. Wood composites bonded with SPI-Kymene adhesive preparations had shear strengths comparable to or higher than those bonded with commercial phenol formaldehyde resins. Wood composites bonded with the new adhesive system had high water resistance and retained relatively high strength even after they had undergone a boiling-water test. The new adhesive system is formaldehyde-free, easy to use, and environmentally friendly. Kymene was proposed to serve as a curing agent in SPI-Kymene adhesives.

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Existing pressure sensitive adhesives (PSAs) are mainly derived from petrochemicals. This study describes a novel approach for development of biobased PSAs. Epoxidized soybean oil was polymerized and cross-linked with a dicarboxylic acid to generate superior PSAs. The dicarboxylic acids used in this study included dimer acid (DA), sebacic acid, adipic acid, and a difunctional polymeric carboxylic acid that was prepared from polymerization of bisphenol A diglycidyl ether (BPAGE) and an excess of DA. AMC-2, a chromium-(III)-based organometallic compound, was found to be the most effective catalyst for the polymerization/cross-linking. The PSAs had a peel strength of 1.4−5.0 N/cm, a loop tack of 7.1−12.6 N, a shear strength of 34 min to more than 168 h, and a good aging resistance. The adhesive properties of the PSAs can be tailored for specific applications such as PSA tapes and labels through the selection of the dicarboxylic acid and its usage. Incorporation of a small amount of phenylene-containing monomer BPAGE into the PSAs significantly increases the peel and shear strengths of the resulting PSAs. This new class of PSAs can be fully based on renewable materials. The preparation of the PSAs does not use any organic solvent or toxic chemicals, thus being environmentally friendly.

In this study, we developed a formaldehydefree adhesive from abundant, renewable, and inexpensive soy flour (SF). The main ingredients of this adhesive included SF, polyethylenimine (PEI), and maleic anhydride (MA). The optimum formulation of this adhesive and the optimum hot-press conditions for making plywood were investigated. A three-cycle soak test and a boiling water test (BWT) were employed for evaluating the strength and water-resistance of plywood bonded with this adhesive. Results showed that SF, PEI, MA and sodium hydroxide were all essential components for the adhesive and the SF/ PEI/MA weight ratio of 7/1.0/0.32 resulted in the highest water-resistance. When the hot-press temperature was in the range of 140-170°C, both water-resistance and shear strength of plywood bonded with the adhesive remained statistically the same, except that the dry shear strength of plywood at 170°C was statistically lower than that at 160°C. When the hot-press time ranged from 2 to 6 min, the plywood panels at 5 min had the highest boiling water test/wet (BWT/w) shear strength. The plywood panels made at 5 min had a higher dry shear strength than those made at 3 min. Plywood panels bonded with this SF/PEI/ MA adhesive exceeded the requirements for interior applications.