Diane Schorr

Determination of In Situ Esterification Parameters of Citric Acid-Glycerol Based Polymers for Wood Impregnation

The development of wood treatments is of increasing industrial importance. A novel technique for improving the properties of lodgepole pine and white pine through modification of the microstructure is described. The present investigation is devoted to the synthesis and determination of in situ parameters of citric acid and glycerol based polymers for wood impregnation. This solvent free approach is environmentally friendly and achieved through an esterification condensation reaction under acidic conditions. Crude glycerol and citric acid reactants were cross-linked via a curing process at 160 °C creating a polymer with only water as the byproduct. The ester bonds and crosslinking levels were controlled using different catalysts and citric acid contents and related to the reaction time and temperature. The nature of bonding within the polymers and at the wood cell walls was determined by FT-IR analysis. The thermal properties such as glass transition temperature (Tg) were studied using TGA/DSC and the effect of citric acid content and catalyst type determined. Dimensional stability of impregnated wood samples improved above 50% for each sample with HCl and p-TSA catalysts compared to control samples. FTIR spectra were studied to show the presence of the ester linkages of the polymer in situ at the wood cell walls. Bonding between the polymer and wood macromolecules were observed by scanning electron microscopy and interpreted as evidence of chemical bonds at the wood cells. When prepared using a catalyst, the polymer was intimately incorporated into wood structure significantly improving the substrate dimensional stability. Enhanced stability makes this approach of particular interest for exterior wood products especially as a green renewable option for the wood industry.

Synthesis and incorporation of poly(methyl methacrylate) microspheres with UV stabilizers in wood clear coating binder

The durability of clear coatings is an important problem in the coatings industry. This problem can be partly solved with the addition of UV absorbers (UVAs) in the coating formulation. UVAs can absorb part of the UV radiation and convert it into harmless heat. Organic UVAs are prone to photodegradation and can migrate in the binder of a coating formulation. In this study, commercial UVAs have been encapsulated in poly(methyl methacrylate) microspheres using the internal phase separation method. Microspheres have been incorporated into a clear acrylic binder. The acrylic was then applied on wood panels and was placed into an artificial UV chamber. Efficiency of coatings after aging as well as chemical and physical properties were monitored using a colorimeter, FTIR spectroscopy and transmission electron microscopy. This study presents a comparison between the efficiency of free and encapsulated Tinuvin 1130 and 292 commercial absorbers. Results have shown that the coating efficiency is slightly improved when using the encapsulated products.

Glycerol and Citric Acid Treatment of Lodgepole Pine

ABSTRACT As part of a research program to expand the potential of wood products in exterior applications, lodgepole pine wood was impregnated with a solution of glycerol and citric acid to improve its dimensional stability and other relevant properties. Two catalysts were studied: one liquid (hydrochloric acid, HCl) and one solid (nanoclay, Cloisite 30B). After impregnation, the specimens were polymerized at two temperatures (160°C and 180°C). The nanoclay dispersion and reticulation analysis were performed by XRD and TEM methods. Other analysis methods such as SEM, DSC, TGA, FT-IR were used to characterize the treatment solutions, polymers and treated specimens. The dimensional stability, hardness, adhesion strength and roughness of the specimens were measured and analyzed. Cloisite 30B proved to be a good catalyst, as it contributed to improving the dimensional stability and hardness of the wood while outperforming the HCl catalyst in counteracting the adhesion strength loss attributed to the wood-polymer composite. The polymerization temperature also affected the results. At 180°C, dimensional stability and adhesion strength were higher than at 160°C and the loss of treatment solution was also higher. Impregnating wood with a glycerol ester could drastically improve its physical properties, including dimensional stability and hardness, particularly when Cloisite 30B nanoclay is used as a catalyst.

Comparison of two encapsulation systems of UV stabilizers on the UV protection efficiency of wood clear coats

Abstract One of the major issues in the wood industry is the durability of clear coatings. The addition of organic ultraviolet absorbers (UVAs) improves coating resistance by the absorption and conversion of UV radiation into harmless heat. Organic UVAs are, however, easily degraded by free radicals produced by photodegradation inside the polymer matrix and are prone to migration in the coating. In this study, commercial UVAs and hindered amine light stabilizers (HALS) entrapped into poly(methyl methacrylate) (PMMA) microspheres and CaCO3 templates coated with UV-responsive polymers were added into clear acrylic water-based coating formulation. Artificial accelerated weathering experiments were performed on each formulation. Raman spectroscopy mapping was performed to visualize the concentration and distribution of UVAs and HALS. This study also presents a comparison of the mechanical properties of coatings obtained by dynamic mechanical analysis. Results showed that coating mechanical properties were improved when using encapsulated UVAs and HALS inside PMMA microspheres. The color change of the wood and coating system was minimized and the production of photo-oxidation compounds in the binder was also limited.

Wood particleboards produced with unmodified and esterified Kraft lignins

Abstract Hardwood Kraft lignins were esterified with succinic anhydride and chemically, thermally and morphologically characterised compared to their unmodified counterparts. Esterification was confirmed by NMR and Fourier transform infrared spectrometer (FT-IR). Esterified lignins were found to be porous, less thermally stable and slightly more hydrophilic than unmodified lignins because esterification with cyclic acid anhydride is accompanied with the simultaneous liberation of carboxylic acid groups. These free carboxylic acid groups are interesting for panel production as they could create new ester groups with wood components. The wood particleboard panels were produced via compression moulding using different concentrations of unmodified and esterified Kraft lignins as sole binders (10, 20 and 30%). All the mechanical properties [impact strength, modulus of elasticity (MOE) and modulus of rupture (MOR)] of the studied wood particleboard panels significantly increased with the addition of the succinated and unmodified Kraft lignins. However, the best mechanical properties were determined for panels containing 20% of unmodified Kraft lignins. Therefore, the condensation reactions of the unmodified Kraft lignins taking place during the compression moulding seem explain why these lignins act as a more efficient binder than the succinated lignins.