The effect of natural aging time on the physicochemical properties and combustion characteristics of pine wood

The study took Ming, Qing and modern pine as research objects to reveal the degradation mechanisms of ancient architectural pine in the process of natural aging, and analyzed the evolution law of physicochemical properties and combustion characteristics of natural aging pine by scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR), mechanical tensile testing and cone calorimetry. The results showed that natural aging could promote cell wall cracking and degradation of organic components in wood, resulting in a 3.6% increase in cellulose crystallinity of Ming Dynasty pine compared with modern pine. The degradation of organic components led to an increase in wettability, surface contact angle decreased by 31.9° in Ming Dynasty pine. Natural aging also reduced mechanical strength of pine wood, the tensile and bending strength of pine are linearly related to natural aging time. Furthermore, natural aging decreased the organic matter and increased the pore size of pine wood, and then showed lower peak heat release rate(PHRR) and total heat release(THR) during combustion. Compared with modern pine, PHRR and THR of pine wood in Ming Dynasty decreased by 34.1% and 34.7%.