| Compared to the mechanical properties and optical properties of paper (pulp), thermal properties of paper (pulp) still need to be understood and researched. To understand and study thermal properties of paper (pulp) profoundly can help researchers develop and use the thermal properties based on existing features, and help offer a deeper understanding of the influence by thermal effect on the changes of paper properties, as well as provide a theoretical basis for reducing thermal aging of paper and paper documentation. This thesis will focus on the research of paper (pulp) thermal properties to compensate the lack of related research and establish the foundation for further research and utilization.In the study, thermogravimetry was used to explore the thermal decomposition characteristics of a variety of cellulose pulps on high-temperature (200~380℃) firstly. Thermal stabilities of different pulp celluloses were compared detaily based on pulp cellulose pyrolysis kinetics equation gained from TG analysis. Secondly, a lower temperature (120~170℃) aging test was carried out in terms of thermal analysis, and a degradation model of paper thermal aging was established by discussing the trends of aging characteristics. Moreover, the feasibility of using TG to evaluate the aging of paper was discussed, and a new quantitative evaluation method of paper aging based on TG, which made the detection of the paper aging quickly and easily come true, was build Finally, Near-Infrared spectroscopy (NIR) was applied for paper aging to get non-destructive determination. The main conclusions obtained are:1. At a given heating rate, the weight loss during pyrolysis can be divided into two stages: dehydration and weight loss caused by cellulose pyrolysis. A preliminary judgment for pulp thermal stability could be obtained by single or multiple critical temperatures. The sequences of pulp thermal stability were: softwood pulp>hardwood pulp>non-wood pulp. Cotton pulp owned the best thermal stability. Deinked Pulp and mechanical pulp had poorer thermal stability compared with chemical pulp. Thermal stability index had a good combination with thermogravimetric curve profile and critical temperature, and it could be a comprehensive and accurate evaluation for pulp thermal stability.2. Pulp pyrolysis mechanism function was described by the model equation: G (a )=-ln(1-a).Pulp pyrolysis kinetics equation was: ln[G(α)/T~2]=ln(AR/βE)-E/RT. Thermal dynamic parameters including activation energy E and pre-exponential factor A could be estimated according to pyrolysis model. The larger activation energy of pyrolysis, the smaller extent of degradation, and the better thermal stability. The qualitative judgment of pulp thermal stability could be gained according to the magnitude of activation energy, and the consequences fitted the results from critical temperature and thermal stability index well.3. Mechanical (tensile strength) and optical (brightness)properties of paper were significantly affected by the aging temperature. Tensile strength, brightness and degree of polymerization (DP) decreased with the aging time increasing. The cellulose crystal type and degree of crystallinity didn't change during the aging process. The dynamic model of cellulose degradation was derived. The more practical and extensive first-order model and second-order model were obtained based on TTSP. The improved model could be used to evaluate paper aging properties under other aging conditions by existing data.4. DP/DP0 index had an exponential model with DT0.5. The equation are: DP/DP0=0.8064exp(-DT0.5/0.8404)+0.1625. DT0.5 could be used as a parameter for evaluating paper aging grade. A rapid method for quantitative evaluation of paper aging could be established by thermogravimetry. The obtained exponential model had a nice consistency with the datas taken from experiment. The model had a good practicability.5. NIR principal component analysis provided a new approach to determine the degree of paper aging. DP calibration model was established on the basis of NIR. The deviation between predicted and measured values was in the range from -4.88 to 4.53%, which showed the prediction was good. The model could be used to determine the DP of paper during aging quickly as well as non-destructive. Amorphous and semi-crystalline regions were largely influenced by the aging, while the changes of crystalline region were indeterminate.
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