Development of nanomodified multifunctional protection systems for wood structures

Introduction. Nowadays multi-storey buildings, composed of wood structures, are built in different countries. The durabi-lity of structures depends to a large extent on the protection systems used. The most effective ones are multifunctional protection systems that rise the fire protection ability, hydrophobicity, and biostability of structural materials. The application of carbon nanotubes is expected to improve the uniformity of a protective layer and the coating performance. The purpose of the project is to develop a multifunctional protection system designated for wood structures. This system must ensure their fire resistance and hydrophobicity without deteriorating the mechanical properties of wood. Materials and methods. Pine wood samples were used in the research. Carbon nanotubes were used as nano-modifiers. Wood samples, surface-modified with methylphosphonic (MPH) and nitrilo-trimethylphosphonic (NPH) acids, were used to develop multifunctional protection systems. Integrated protection systems were developed by adding carbon nanotubes. Fire hazard properties were assessed pursuant to GOST 27484-87, water absorption properties were analyzed pursuant to GOST 16483.20-72, mechanical properties were addressed with reference to GOST 16483.11-72 and 16483.10-73. Hydrophobicity was evaluated using the wetting angle method. The character of the sample surface and its chemical composition were studied using the double-beam scanning electron-ion microscope FEI Quanta 3D FEG with an EDAX Octane select attachment needed for the energy dispersion analysis. Results. All studied coating systems belong to the first group of the fire retardant efficiency, the best of them reduce weight loss in the course of combustion of samples: Δweight = 3.7 – 1.34 %. Wood develops hydrophobic properties; its water absorption reduces 1.5-fold, while its across-fiber mechanical compressive strength goes up 1.6-fold. The assessment of the wood surface and its chemical composition shows that high fire resistance correlates with higher phosphorus content in the char layer formed during combustion. Conclusions. Surface modification of wood by protection systems is recommended as an effective means of rising the durability of structures.