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The core of decorative laminates is generally made of stacked Kraft paper sheets impregnated with a phenolic resin. As the impregnation process in industry is relatively fast, new methods need to be developed to characterize it for different paper-resin systems. Several phenolic resins were synthesized with the same Phenol:Formaldehyde ratio of 1:1.8 and characterized by Fourier Transform Infrared Spectrometry (FTIR) as well as Size-Exclusion Chromatography (SEC). In addition, their viscosities and surface tensions when diluted in methanol to 45% of solid content were measured. The capacity of each resin to penetrate a Kraft paper sheet was characterized using a new method, which measures the conductivities induced by the liquid resin crossing the paper substrate. With this method, crossing times could be measured with a good accuracy. Surprisingly, the results showed that the penetration time of the resin samples is not correlated to the viscosity values, but rather to the surface tension characteristics and the chemical characteristics of paper. Furthermore, some resins had a higher swelling effect on the fibers that delayed the crossing of the liquid through the paper. [ABSTRACT FROM AUTHOR]

Abstract: Grafting polymerisation of acrylic monomers onto cellulose chains represents a useful method of restoration for both artificially and naturally aged paper-based materials. In this paper, some results concerning the grafting polymerisation of ethyl acrylate/methyl methacrylate 75/25wt.% copolymer onto several paper grades are reported, highlighting how the presence of fillers in the raw materials reduced the grafting yields. The consolidating and protective effects have been investigated by evaluating the mechanical properties and the wetting behaviour of the grafted samples, and comparing them with the original and aged substrates. [Copyright &y& Elsevier]