Abstract
Melamine-formaldehyde (MF) resins are widely used as surface finishes for engineered wood-based panels in decorative laminates. Since no additional glue is applied in lamination, the overall residual curing capacity of MF resins is of great technological importance. Residual curing capacity is measured by differential scanning calorimetry (DSC) as the exothermic curing enthalpy integral of the liquid resin. After resin synthesis is completed, the resulting pre-polymer has a defined chemical structure with a corresponding residual curing capacity. Predicting the residual curing capacity of a resin batch already at an early stage during synthesis would enable corrective measures to be taken by making adjustments while synthesis is still in progress. Thereby, discarding faulty batches could be avoided. Here, by using a batch modelling approach, it is demonstrated how quantitative predictions of MF residual curing capacity can be derived from inline Fourier Transform infrared (FTIR) spectra recorded during resin synthesis using partial least squares regression. Not only is there a strong correlation (R2 = 0.89) between the infrared spectra measured at the end of MF resin synthesis and the residual curing capacity. The inline reaction spectra obtained already at the point of complete dissolution of melamine upon methylolation during the initial stage of resin synthesis are also well suited for predicting final curing performance of the resin. Based on these IR spectra, a valid regression model (R2 = 0.85) can be established using information obtained at a very early stage of MF resin synthesis.
Highlights
Melamine-formaldehyde (MF) resins have been widely used in the wood-processing industry as glues, binders and coatings for many decades due to their outstanding properties [1]
By using a batch modelling approach, it is demonstrated how quantitative predictions of MF residual curing capacity can be derived from inline Fourier Transform infrared (FTIR) spectra recorded during resin synthesis using partial least squares regression
The arrows indicate the directions of the mInostht esisgpneicftircaalnrtegcihoannfgroems d1u75r0intgo t7h5e0 ccomn−d1e, nmsealtaimoninpe hshaoswe.s the characteristic absorbance bands found in melamine formaldehyde resins (Figure 4b)
Summary
Melamine-formaldehyde (MF) resins have been widely used in the wood-processing industry as glues, binders and coatings for many decades due to their outstanding properties [1]. Since the 1950s, much research has been conducted to understand melamine-formaldehyde resins and to develop MF resins for special applications. Nd ether bridges formation take place under alkaline or acidic conditions. They cannot be clearly separated from one another since methyMloelstphayrtliocilpaattieoinn caosndweneslaltiaosn mreaecttihonysleasnseo-oenthasetrheaynadreefotrhmeerdb[1r3id,14g]e. Polymers[220021–, 2132, ]2.54H1 owever, this is only possible within certain limits and both the processing be-3 of 19 havior and the performance in solid state of a resin are mainly determined by the applied synthesis conditions and, in particular, by the melamine-to-formaldehyde ratio [23]. The dry impregnated paper is processed on a substr2a.teMmataetreirailasla. nd Methods
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