In the present contribution, investigations on the chemical modification of thermosetting melamine formaldehyde resins by natural polyol compounds are presented. As representative agents soluble starch, sucrose, and glycerol were chosen to cover three different classes of polyols. The major aim was to use substances produced from natural bio-renewable feedstock that are available in large quantities and may serve as environmentally innocuous and bio-renewable substitutes for petro-chemically derived and potentially hazardous materials. Different reaction conditions lead to resins with varying technical performance. For soluble starch no reaction conditions could be found that allow the adoption of this substitute for the laminate industry due to insufficient technological performance. Sucrose and glycerol on the other hand yielded impregnation resins with suitable performance. Chemical linkage of the modifying agent into the chain propagation by poly-condensation however, was only found with glycerol. The covalent incorporation of glycerol in the network was observed with addition of glycerol at different stages during synthesis. The technological performance of the various modified thermosetting resins was assessed by determining flow viscosity, molar mass distribution, the storage stability, and in a second step laminating impregnated paper to particle boards and testing the resulting surfaces according to standardized quality tests.
Melamine formaldehyde (MF) resins are widely used for the gluing and surface coating of wood‐based consumer products in the interior design of living environments. MF resins are especially relevant in decorative laminate applications because of their good performance‐to‐price ratio. In their industrial processing, an important intermediate state is the liquid MF prepolymer that is used for decorative paper impregnation. Here, the drying of impregnated papers is investigated with respect to premature curing. A new method to quantify water release upon drying that allows estimation of the degree of undesired precuring is described. Since curing proceeds via polycondensation, crosslinking brings about the release of water molecules. By thermogravimetric analysis (TGA), drying was studied in terms of water release due to physical drying (elimination of “dilution water”) and chemical crosslinking of the prepolymer to a three‐dimensional MF network (elimination of chemically liberated water). The results obtained by TGA/IR spectroscopic analysis of the liberated volatiles show that the emission of water from b‐stage MF can be clearly analytically separated into a physical (evaporation of dilution water) and a chemical (liberation via condensation) sequence. TGA experiments were correlated with curing experiments performed with differential scanning calorimetry (DSC) to estimate the residual crosslinking capacities of the impregnated papers. The drying conditions used during the preparation of impregnated decorative papers seemed to significantly affect their remaining reactivity only when harsh drying conditions were used. Upon heat exposure for prolonged time, precuring of the oligomer units results in a shift of the temperature maxima in TGA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39860.
A highly efficient, catalytic open-air ring opening polymerization for cyclic esters is reported. Using titanium alkoxides, Ti(OiPr) 4 and Ti(OnBu) 4 , as catalysts reproducible ROPs even with high monomer/initiator ratios without protecting gas are feasible. † Electronic supplementary information (ESI) available: Experimental details of the polymerization process, analyzing methods and the locations where the experiments were carried out. See
Decorative laminates based on melamine formaldehyde (MF) resin impregnated papers are used at great extent for surface finishing of engineered wood that is used for furniture, kitchen, and working surfaces, flooring and exterior cladding. In all these applications, optically flawless appearance is a major issue. The work described here is focused on enhancing the cleanability and antifingerprint properties of smooth, matt surface‐finished melamine‐coated particleboards for furniture fronts, without at the same time changing or deteriorating other important surface parameters such as hardness, roughness or gloss. In order to adjust the surface polarity of a low pressure melamine film, novel interface‐active macromolecular compounds were prepared and tested for their suitability as an antifingerprint additive. Two hydroxy‐functional surfactants (polydimethysiloxane, PDMS‐OH and perfluoroether, PF‐OH) were oxidized under mild conditions to the corresponding aldehydes (PDMS‐CHO and PF‐CHO) using a pyridinium chlorochromate catalyst. With the most promising oxidized polymeric additive, PDMS‐CHO, the contact angles against water, n‐hexadecane, and squalene increased from 79.8°, 26.3° and 31.4° for the pure MF surface to 108.5°, 54.8°, and 59.3°, respectively, for the modified MF surfaces. While for the laminated MF surface based on the oxidized fluoroether the gloss values were much higher than required, for the surfaces based on oxidized polydimethylsiloxane the technological values as well as the lower gloss values were in agreement with the requirements and showed much improved surface cleanability, as was also confirmed by colorimetric measurements. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40964.
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