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Melamine-dialdehyde starch resins used for wood surface finishes have been developed. The reaction of melamine with dialdehyde starch has been shown to occur by FTIR and MALDI ToF spectrometry, with several oligomer species due to the reaction of the two materials being identified, and the resin thermal stability was studied by thermogravimetric analysis. The resins were prepared by two different procedures when it was realized that dialdehyde starch is sensitive to too high a temperature for prolonged times. The melamine-dialdehyde starch resins were applied on particleboard supports as a direct liquid surface finish and a resin-impregnated paper. The surface finishes were tested for adhesion by the cross-cut test, their initial sessile drop contact angle, and the contact angle evolution as a function of time. The best results were obtained by the resins catalyzed by 2% ammonium sulfate and applied to the support surface as a resin-impregnated paper hot pressed for 3 min at 200°C, although the results at 180°C also looked promising. [ABSTRACT FROM AUTHOR]

Screw connection is a type most commonly applied to timber structures. As important commercial tree species in China, Masson pine and Chinese fir have the potential to prepare wood structures. In this study, the effects of the diameter of the self-tapping screw and the guiding bores on the nail holding performance on different sections of Masson pine and Chinese fir dimension lumbers were mainly explored. The results showed that: (1) The nail holding strength of the tangential section was the maximum, followed by that of the radial section, and that of the cross section was the minimum. (2) The nail holding strength of Masson pine was higher than that of Chinese fir. (3) The nail holding strength grew with the increase in the diameter of self-tapping screws, but a large diameter would lead to plastic cracking of the timber, thus further affecting the nail holding strength. Masson pine and Chinese fir reached the maximum nail holding strength when the diameter of self-tapping screws was 3.5 mm. (4) Under a large diameter of screws, prefabricated guiding bores could mitigate timber cracking and improve its nail holding strength. (5) Prefabricated guiding bores were more necessary for the screw connection of Masson pine. The results obtained could provide a scientific basis for the screw connection design of Masson pine and Chinese fir timber structures. [ABSTRACT FROM AUTHOR]