Thermal Decomposition Kinetics And Crystallization Kinetics Of Wood Materials

Increasing global population,emerging issues such as carbon sequestration and carbon neutrality will drive trends in the use of wood in specific directions.The development of woodbased materials with novel properties is a powerful means to achieve a more efficient use of wood-based materials.The pyrolytic and crystallization properties of wood materials are important characteristic parameters,and their use scenarios are greatly constrained by these parameters,so that the investigation of the pyrolytic and crystallization properties of wood materials can be a guide for their use in specific directions.Parameters such as pyrolysis reaction temperature and activation energy obtained from pyrolysis kinetic calculations are important evaluation indicators to describe wood materials in the process of pyrolysis,however,not all pyrolysis models can be used to calculate the pyrolysis parameters of wood materials,and there are no studies to systematically compare and analyze these models.In this paper,the kinetics of thermal decomposition of different kinds of wood materials,wood-plastic composites and radiata pine based carbon quantum dot films were investigated by using F-W-O model,C-R model,Friedman model,Kissinger model and Gaussian multi-peak fitting model to discuss the changes in the thermal decomposition process of the above wood materials and the applicability of each model.The Avrami model and the Avrami-Ozawa model were used to investigate the non-isothermal crystallization process and discuss the variation pattern of the above wood materials during the crystallization process and the applicability of the models.The main findings are as follows.(1)The activation energies of the hardwoods and sapwoods of the eight woods ranged from120 to 140 k J/mol,the average activation energies of the wood-plastic composites(WPCs)ranged from 144 to 205 k J/mol,and the average activation energies of the carbon quantum dots(CQDs)films ranged from 108 to 140 k J/mol.The addition of plastic as a gaining material could significantly improve the thermal stability of the wood materials.The reaction in the activation energy value is an increase in the average activation energy.However,the average activation energy of the wood material decreased instead when the size of the wood material is smaller and reaches the nanometer level.In addition,within the same wood species,the activation energy of heartwood is slightly higher than that of sapwood.(2)The F-W-O model,C-R model,Friedman model and Gaussian multi-peak fitting model can calculate some parameters in the thermal decomposition process of wood materials more accurately.Among them,the Gaussian multi-peak fitting model can fit and predict the conversion curves of wood materials in the thermal decomposition process,and the curves of conversion obtained from the model predictions were in good agreement with the actual conversion curves.However,the apparent activation energy calculated by Friedman’s model was different from the apparent activation energy calculated by the other three models,which means that Friedman’s model is not suitable for calculating the activation energy of wood materials.(3)The crystallinity of natural solid wood and wood-plastic composites increased with the increase of the heating rate.In wood-plastic composites,wood flour made of natural solid wood and basalt fibers made of natural solid wood acted as nucleating agents.The addition of basalt fibers and wood flour changed the crystallinity of the wood composites.In addition,basalt fibers and wood flour acted as nucleating agents with the ability to accelerate the crystallization of wood composites without changing the crystallization mechanism of these composites.