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In this study, hydroxyapatite (HA) was surface modified with silane coupling agent. The modified HA was named HA-APTES, and its structure was analyzed. Hydroxyapatite modified urea-formaldehyde resin (HUF) were prepared by adding different amounts of HA-APTES in the synthesis process. The properties of the resin were tested to determine the optimal addition amount of HA-APTES, and the thermal curing properties of resins were investigated by differential scanning calorimetry. The results suggested that HA-APTES has excellent formaldehyde-reducing effect and can significantly improve the wet shear strength of the resin, and the optimal addition amount of HA-APTES is 3%. Notably, compared to UF resin, the peak temperature and activation energy (Eα) of HUF resin are increased, the reaction sites are increased, and the network structure is complicated. [ABSTRACT FROM AUTHOR]

In this work, tea powder was used as a filler to produce low-formaldehyde-emission tea-based melamine-modified urea–formaldehyde resin (TMUF). The thermal stabilities of TMUF and the resin without tea powder (MUF0) were characterized using thermogravimetry. The optimal amount of tea powder m(tea)/m(tea + urea) was equal to 0.15. The formaldehyde emission of the three-layer plywood produced by TMUF was reduced by 75.43%, and the wet bonding strength of the plate was increased by 26.67% as compared with the plywood prepared by MUF0. Compared with MUF0, the thermal degradation peak temperature of TMUF resin was shifted to higher temperature, while the carbon residue was increased. The thermal degradation activation energies of TMUF and MUF0 were similar, while TMUF had a lower pre-exponential A. The Flynn–Wall–Ozawa model-free method is used to estimate various activation energy values at different conversion rates and to predict possible reaction mechanisms. Judging the reaction mechanism according to the slope of the straight line fitted by different models, the best model was based on random nucleation. [ABSTRACT FROM AUTHOR]

In order to evaluate the significant effects of curing temperature, solid content, and pH on the pre-curing behavior of the UF resin, the isothermal and non-isothermal thermal behaviors were discussed by differential scanning calorimetry in this work. The results indicated that the temperature and pH showed significant influence on the whole shape of the DSC curves and the conversion at the same time of the UF resin. Meanwhile, the non-isothermal thermal behavior showed that when the UF resin pre-cured for the same time of 30 s, the onset and peak and end temperature of the DSC curves were decreased, and the activation energy and the conversion was also increased with the increasing curing temperature or decreasing pH. Based on the analysis of the contribution rate of the temperature, solid content, and pH on the conversion and heat of pre-curing UF resin, the results indicated that the pH and temperature showed significance effect on the pre-curing action than solid content. [ABSTRACT FROM AUTHOR]

The thermal decomposition characteristics of microwave liquefied rape straw residues with respect to liquefaction condition and pyrolysis conversion were investigated using a thermogravimetric (TG) analyzer at the heating rates of 5, 20, 50 °C min−1. The hemicellulose decomposition peak was absent at the derivative thermogravimetric analysis (DTG) curve of liquefied residues, because it had been decomposed during the liquefaction. Furthermore, among the liquefied residues, the one from the reaction condition of 180 °C/15 min had the highest thermal stability under a high temperature (>700 °C). The DTG profiles revealed that raising the temperature heating rate could result in an increase in the maximum decomposition temperature. The apparent activation energy (Eα) values of the liquefied residues were lower than that of non-liquefied raw rape straw, whereas the recondensation reaction occurred at 180 °C/15 min remarkably increased the Eα. A noticeable increase in the Eα was observed for the liquefied residue from the 180 °C/10 min samples as the pyrolysis conversion increased from 0.15 to 0.55, suggesting a complex decomposition process with the increasing pyrolysis temperature. The liquefaction process could decrease the thermal decomposition temperature of biomass, which means higher reactivity and lower operational costs during pyrolysis. [ABSTRACT FROM AUTHOR]