Norsodyne resin

Two different styrene-unsaturated polyester resins were involved in this study (1) Norsodyne resin (Norsolor, France) and (2) a research flexible formulation based... 

Norsodyne Resin, Isophthalic type (high resistance to hydrolysis and organic solvents) acid index, 13 styrene content, 50 wt % viscosity (Brookfield-type rotational viscometer) at 25 °C, 160 mPa s (cP) and volumetric shrinkage, 9%. 

The best results in this study were obtained with the Norsodyne resin, which is currently used for artifact treatment. No cracks were observed on treated samples that presented a hard surface. However, radial cracking occurred with cylindrical forms. The mean shrinkages in the longitudinal (/), radial (r), and tangential (t) directions were, respectively for beech samples, 0.9% (/), 2.3 % (r), and 4.6% (t) for oak samples, 0% (Z), 0.9% (r), and 1.2% (t). As far as highly deteriorated wood is concerned, some warping can be expected. 

Figure 4. Effect of dose rate on polymerization temperature of Norsodyne styrene-unsaturated polyester resin.

No significant volumetric change was observed on oak samples after dehydration. On the other hand, deteriorated beech samples showed a mean volumetric shrinkage of 3% in both solvents. Acetone-impregnated samples were immersed for 2 weeks in Norsodyne and Ludopal resins diluted by 15% acetone in each first bath. The solutions were then changed three times by pure resins at 2-week intervals, totaling an impregnation time of 8 weeks for this final phase. 

Impregnation with the Ludopal formulation gave the following results For beech samples, the mean shrinkages were 0.1% (Z), 0.9% (r), and 3.5% (t) Some radial cracks were present because the wood has a relatively soft surface. The softness can be explained by the presence of butyl acrylate in the formulation, which gave a more flexible resin than the Norsodyne formulation, but was more sensitive to oxygen inhibition. For oak samples, the mean shrinkages were 0.4% (Z), 1.2% (r), and 0.9% (f). No cracks were observed. 

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