Modifications of melamine resins for functional surface finishing

Melamine Formaldehyde (MF) resins are thermosetting synthetic materials. The present work deals with the evaluation of the impregnation process, modification of resin structure and abrasion resistant applications. During the industrial process paper is impregnated by aqueous oligomers. The drying procedure and the corresponding residual volatile content is a crucial step during production, because of its influence on the later surface quality. Standard measurement routines do not differentiate between physical and chemical origin. Using TGA and DSC methods, the evaporation of water could be characterized as a clear separation of solvent evaporation and the release of water during condensation. The method could be used to upgrade current quality control as well as reaction condition tuning. According to the characteristics of duroplastic material, the formed network is very dense but also brittle. Challenging applications require highly modified resins in order to decrease the network density. Substances from bio renewable resources offer chemical possibilities for covalent crosslinking. Several substance classes have been tested for compatibility via hydroxyl groups or amines. The addition of polyols under appropriate reaction conditions showed chemical incorporation into the MF prepolymer. NMR methods have been used to characterize the resins. The synthesized polymers represent a suitable alternative for the usage in challenging furniture and flooring laminate applications. MF applications for scratch and wear resistant surfaces are commonly reinforced by multiple layer setups with inorganic particles. Fulfilling normative requirements a one sheet setup of decorative paper has been developed and tested. The incorporation of special corundum particles directly on the decorative printed paper combined with a new coating system resulted in surfaces of the requested quality for wear resistance surfaces

On the suitability of natural polyols as resin components for paper-based laminates

Three different polyols (soluble starch, sucrose, and glycerol) were tested for their potential in the chemical modification of melamine formaldehyde (MF) resins for paper impregnation. MF impregnated papers are widely used as finishing materials for engineered wood. These polyols were selected because the presence of multiple hydroxy groups in the molecules was suspected to facilitate cocondensation with the main MF framework. This should lead to good resin performance. Moreover, they are readily produced from natural feedstock. They are available in large quantities and may serve as economically feasible, environmentally harmless alternative co-monomers suitable to substitute a portion of fossil-based starting material. In the presented work, a number of model resins were synthesized and tested for covalent incorporation of the natural polyol into the MF Framework. Spectroscopic evidence of chemical incorporation of glycerol was found by applying by 1H, 13C, 1H/13C HSQC, 1H/13C HMBC, and 1H DOSY methods. It was furthermore found that covalent incorporation of glycerol in the network took place when glycerol was added at different stages during synthesis. Further, all resins were used to prepare decorative laminates and the performance of the novel resins as surface finishing was evaluated using standard technological tests. 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. In most cases, the average board surface properties were of acceptable quality. Our findings demonstrate the possibility to replace several percent of the petrol-based product melamine by compounds obtained from renewable resources

Improving the cleanability of melamine-formaldehyde-based

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