聚氨酯硬泡外墙保温材料的热稳定性分析

Thermal stability analysis of the rigid polyurethane foam for the exterior insulation

在空气和氮气气氛下对聚氨酯硬泡(Rigid Polyurethane Foam,RPUF)进行了热重分析。在空气气氛下将样品分别以10℃/min、20℃/min、40℃/min和50℃/min的升温速率从室温加热至800℃。用Flynn-Wal-l Ozawa(FWO)等转化率方法和非线性多参数回归方法(Mu-ltivariate Non-linear Regression Method)计算热动力学参数。RPUF在空气和氮气气氛中的热解可认为是2步连续反应。RPUF在空气气氛中的热解过程可由Fn→Fn机理准确描述,在氮气气氛中则可由Fn→D3机理描述。基于可靠的动力学参数和反应机理函数,对RPUF在不同温度下的寿命进行了预测。结果表明,RPUF的寿命对温度变化非常敏感,同时受分解气氛等因素的影响。

This paper is intended to introduce an analysis method for thermo-gravimetric study of the rigid polyurethane foam （RPUF） of commercial grade in the atmospheric and nitrogen conditions. The samples we adopted should be heated from the ambient temperature to 800 ℃ at the heating rates of 10 ℃/min, 20 ℃/min, 40 ℃/min and 50 ℃/min, respectively. In the above said conditions, the RPUF to be tested has to undergo four decomposition stages as is required in the said conditions, whereas the first two stages were mainly supposed to experience the loss of water and small molecules, which are actually not essential for the dominant stages. However, the last two stages are supposed to be of great significance. With the increase of the heating rate, the temperature of the onset decomposition Ton, the temperature at the maximum decomposition rate Tm, and the maximum decomposition rate - （dwt/dt）m, are pushed to the high temperature region. Furthermore, the variations of activation energy with the conversion degree are evaluated by using Flynn-Wall-Ozawa （FWO） isoconversional method. In our study, we have also investi- gated the reaction model and corresponding kinetic parameters with the multivariate non-linear regression method. The kinetic parameters we have gained demonstrate that the decomposition of RPUF tends to undergo two successive reaction steps both under the atmospheric condition and nitrogen condition. The decomposition of RPUF can be described by Fn→Fn kinetic model under the atmospheric condition while that of RPUF under nitrogen condition can be described by Fn→D3 kinetic model. The kinetic model can further be verified by comparing the activation energy values obtained by FWO method and the multivariate non-linear regression method. Based on the analysis of the reliable kinetic parameters and the reaction models, the lifetime of RPUF under different temperatures can be predicted. It is also very sensitive to temperature variations and prone to the effects of other factors, for example, the decomposition atmosphere, etc. Thus, it can be seen that the present paper can provide useful experimental data for the improvement of classification of the burning behaviors and establishment of the system of the fire prevention codes of the exterior insulation.