The enthalpy of melting and the freezing point depression of European beech (Fagus sylvatica L.) wood modified with 0.8, 1.3, and 2.3 M 1,3-dimethylol-4,5-dihydroxy ethylene urea (DMDHEU) were determined at different levels of moisture content above the fibre saturation point by differential scanning calorimetry. The results permitted estimations of the amount of water bound to the cell wall, non-freezing water (NFW), and pore size distribution. The NFW of wood modified with DMDHEU, calculated on a dry wood basis, was not significantly lower than that of the control. The ratio of bound to total water present in the sample was higher in unmodified than in DMDHEUmodified samples. The proportion of pores with a diameter F30 nm was 70% of the total cell wall voids for wood modified with 2.3 M DMDHEU and 18% for unmodified wood. These results indicate that DMDHEU reduced the pore size of the samples by occupying the void space present in the cell wall.
The dimensional stability and some mechanical properties were tested in plywood produced with veneers modified with 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU). The experimental design included Betula sp. and Fagus sylvatica impregnated with 0.8 M, 1.3 M, and 2.3 M DMDHEU. The plywood consisted of five veneers glued with a phenolic resin. Dimensional stability tests were conducted after 10 cycles of soaking/oven-drying to determine volume changes and anti swelling efficiency (ASE). The mechanical properties tested were hardness (Brinell), modulus of elasticity in bending (MOE), bending strength (BS) and work to maximum load in bending (WMLB). The modified samples for both species were considerably more dimensionally stable than the untreated samples. The samples of Betula sp. and F. sylvatica modified with DMDHEU presented a MOE and a BS unaffected by the treatment. The WMLB was consistently lower in the modified samples than in the unmodified samples. As determined by the Brinell method, the DMDHEU-modified plywood of the Betula sp. and F. sylvatica was harder than the unmodified plywood.
A novel lignin-based slow release fertilizer with low environmental impact has been developed. More precisely, a granulated simple superphosphate fertilizer, consisting of calcium phosphate monobasic [Ca(H2PO4)2·H2O] and gypsum (CaSO4·2H2O) was coated with modified kraft lignins and the diffusion of phosphorus was observed as a function of time. The lignin was hydroxymethylated with formaldehyde and subsequently cross-linked with phenol-formaldehyde resin resulting in HML-PF as coating. Moreover, coating films were prepared from a mixture of acetylated lignin (Lac) and acetylated cellulose (Cellac). Both coatings show similar permeability to calcium phosphate and controlled effectively the P-release, particularly at the initial stages of the experiment. The P-release was linear in the decay phase but there is no lag time in the process. A significant P amount was not released from the particles coated with HML-PF, i.e. 80–50% remained irreversible bound, depending on the coating formulation. The maximum fractional P-release varied among the different coatings tested. Phosphorus is partly retained inside the slightly soluble calcium sulfate matrix.
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