Dynamic mechanical properties of decorative papers impregnated with melamine formaldehyde resin Andreas Kandelbauer, Alfred Teischinger To cite this version: Andreas Kandelbauer, Alfred Teischinger. Dynamic mechanical properties of decorative papers im- pregnated with melamine formaldehyde resin. European Journal of Wood and Wood Products, Springer Verlag, 2009, 68 (2), pp.179-187. 10.1007/s00107-009-0356-7. hal-00568243 HAL Id: hal-00568243 https://hal.archives-ouvertes.fr/hal-00568243 Submitted on 23 Feb 2011 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. 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Holz als Roh- und Werkstoff Draft Manuscript for Review Dynamic mechanical properties of decorative papers impregnated with melamine formaldehyde resin ForJournal: Holz Peer als Roh- und WerkstoffReview Manuscript ID: HRW-08-0139.R1 Manuscript Type: ORIGINALARBEITEN / ORIGINALS Date Submitted by the 28-Jan-2009 Author: Complete List of Authors: Kandelbauer, Andreas; University of Natural Resources and Applied Life Sciences, Wood Science and Technology; Kompetenzzentrum Holz GmbH, WOOD Carinthian Competence Centre (W3C) Teischinger, Alfred; University of Natural Resources and Applied Life Sciences, Wood Science and Technology Decorative laminates, Impregnated paper, Melamine formaldehyde Keywords: resin, Wood based panel industry Editorial Office, TU Mˆ…nchen, Holzforschung Mˆ…nchen, Winzererstr. 45, 80797 Mˆ…nchen, Germany Page 1 of 14 Holz als Roh- und Werkstoff 1 2 3 4 Dynamic mechanical properties of decorative 5 6 papers impregnated with melamine 7 formaldehyde resin 8 9 10 11 Dynamisch mechanische Eigenschaften von 12 13 mit Melamin-Formaldehyd-Harz imprägnierten 14 Dekorpapieren 15 16 17 18 1, 2 1 19 Andreas Kandelbauer *, Alfred Teischinger 20 For Peer Review 21 22 1 23 University of Natural Resources and Applied Life Sciences, Dept. of Wood Science and 24 Technology, Peter Jordan Strasse 82, A-1190 Vienna, Austria 25 2Kompetenzzentrum Holz GmbH, WOOD Carinthian Competence Centre (W3C), 26 Klagenfurterstrasse 87 – 89, A-9300 St. Veit an der Glan, [email protected] , 27 28 29 30 * Corresponding author 31 32 33 34 35 Abstract 36 Papers impregnated with melamine formaldehyde based resins are widely used in 37 decorative surface finishing of engineered wood based panels for indoor and outdoor 38 applications. For cost-effective production of high-quality impregnated papers it is of great 39 importance to understand the complex interplay between manufacturing conditions and 40 technological property profile. In the present study, three raw papers from different 41 suppliers were impregnated with melamine formaldehyde resin in an industrial scale 42 experiment to study the influence of some important manufacturing variables on the 43 processability of impregnated papers. As numerical factors the resin loading, the final 44 moisture content and the amount of curing catalyst were systematically varied according 45 to a statistical central composite design. The model papers were analyzed for their 46 rheological and thermal properties using the dynamic mechanical method developed by 47 Golombek. As target values flow time, cure time, curing rate and flexibility were used to 48 calculate quantitative models for the processability of the impregnated papers using 49 response surface methodology. It is shown that the relevant rheological and thermal 50 paper parameters are significantly influenced by the supplier of the raw paper as well as 51 the manufacturing variables. 52 53 54 55 Zusammenfassung 56 Melaminharz imprägnierte Dekorpapiere werden häufig in der Oberflächenveredelung 57 von plattenförmigen Holzwerkstoffen für Innen- und Außenanwendungen verwendet. Für 58 die kosteneffiziente Produktion von qualitativ hochwertigen imprägnierten Papieren ist es 59 nötig, das komplexe Zusammenspiel zwischen den industriellen 60 Herstellungsbedingungen und dem technologischen Eigenschaftsprofil der Materialien zu verstehen. In der vorliegenden Studie wurden drei vergleichbare Rohpapiere von unterschiedlichen Herstellern im Rahmen eines industriellen Experiments unter verschiedenen Bedingungen mit Melaminharz imprägniert, um den Einfluss einiger 1 Editorial Office, TU Mˆ…nchen, Holzforschung Mˆ…nchen, Winzererstr. 45, 80797 Mˆ…nchen, Germany Holz als Roh- und Werkstoff Page 2 of 14 1 2 3 wichtiger Prozessvariablen auf die Herstellung von imprägniertem Papier zu analysieren. 4 Die Modellpapiere wurden auf ihre rheologischen und dynamisch-mechanischen 5 Eigenschaften nach der Methode von Golombek untersucht. Als Zielgrößen wurden 6 Fließzeit, Härtungszeit, Härtungsgeschwindigkeit und Flexibilität bestimmt und der 7 Einfluss der Produktionsvariablen wurde nach Response Surface-Methoden quantifiziert. 8 Es wird gezeigt, dass die relevanten rheologischen und dynamisch-mechanischen 9 Papierparameter signifikant vom Rohpapierhersteller und den Produktionsbedingungen 10 abhängen. 11 12 13 14 15 16 1. Introduction 17 Paper sheets impregnated with an aminoplastic thermosetting resin are frequently used 18 for the surface protection and decoration of medium density fibreboards (MDF) and 19 particleboards in the furniture (Kandelbauer et al. 2008, Nemli and Colakoglu 2005, Soiné 20 1995) and theFor laminate Peerflooring (Kalaycioglu Review and Hiziroglu 2006, Bauer and Kandelbauer 21 2004) industries. Such paper sheets are typically core impregnated with urea 22 formaldehyde (UF) or melamine formaldehyde (MF) resin in a first step and surface 23 coated with MF resin in a second step (Bader et al. 2000, Ruhdorfer 1980) using a paper 24 impregnation machine such as the one designed by Vits Systems GmbH (Vits 2007, 25 2001), (Figure 1). After impregnation, the paper is dried to a final moisture content of 6 – 26 9 % and subsequently pressed onto the carrier board at temperatures around 180 °C. 27 Since the impregnation resin is not completely cured during paper impregnation there is 28 no additional adhesive required for the surface finishing of the boards. 29 30 31 Figure 1: Schematic representation of the impregnation process of papers for decorative 32 laminates 33 34 The technological properties of impregnated papers must not only fulfil numerous 35 requirements with respect to the final product such as durable surface films, hardness, 36 temperature and chemical resistance etc (cf. for example EN 13 329). They must also fit 37 the demands of the laminates manufacturer in terms of processability such as sufficiently 38 long shelf-life, complete curing during rapid pressing, no blocking when stored in a stack, 39 homogenous film formation etc. The properties of the finished panel product as well as of 40 the intermediate paper sheet are governed by the manufacturing conditions of 41 impregnated papers. Important process parameters that need to be carefully adjusted 42 during the manufacture of such papers are the composition of the resin solution, the 43 numerous roller parameters, the drier conditions and the type of paper used as raw 44 material. 45 One of the most important components of the impregnation solution is the curing catalyst (Becker and Braun 1988). The reactivity of the catalyst governs the speed at which 46 impregnated papers can be processed in the laminating step (Barash 2008). Very 47 reactive systems may cause the resin to pre-cure during impregnated paper manufacture, 48 leading to bad gluability. The reactivity of impregnated paper needs therefore to be 49 carefully adjusted. The drier conditions are important since they govern the cross-linking 50 of the impregnation resin. If set too harsh the required self-gluing property of the paper 51 may be lost rendering the product unusable. 52 The amount of resin is another relevant factor. To reduce the costs, low resin loads are 53 desired. However, if too low amounts of resin are applied the paper is not saturated 54 during core impregnation, the pores are not completely filled and subsequently applied 55 coating resin may sink in leaving a defective surface film (Roberts and Evans 2004). 56 Finally, the paper properties of the raw paper such as density, wet strength or ash 57 content may strongly influence the production process. For instance, paper density 58 affects resin penetration and indirectly determines production speed. Although testing 59 methods have been devised to determine the penetration behaviour of paper/resin 60 systems (see for example http://www.emtec-papertest.com/deutsch/index.html), little is known about the interrelation of raw paper and the properties of impregnated paper. The rheological and thermal properties of impregnated paper such as paper flexibility, resin flow and curing characteristics of MF are very important for evaluating its quality and 2 Editorial Office, TU Mˆ…nchen, Holzforschung Mˆ…nchen, Winzererstr. 45, 80797 Mˆ…nchen, Germany Page 3 of 14 Holz als Roh- und Werkstoff 1 2 3 processability. For instance, the resin flow at the surface of impregnated paper governs 4 film formation and the final surface properties of the coated board. Too low resin flow 5 causes an inhomogeneous film