高压气体氛围中的聚氨酯非等温固化动力学

Non-isothermal curing kinetics of polyurethane under high-pressure gas atmosphere

采用高压DSC对0.1~6 MPa压力范围二氧化碳(CO2)及氮气(N2)氛围中的聚氨酯非等温固化动力学进行了研究。利用Kissinger法及两种不同积分形式的等转化率法求取了聚氨酯固化过程的表观活化能Ea,在此基础上采用Málek法确定了固化反应的机理函数及动力学参数,得到固化反应动力学方程,并分析了高压CO2及N2的存在对固化过程的影响。研究结果表明,该聚氨酯体系的活化能随着反应转化率的增加呈现出典型的先减小后增加的S型反应特征,由于高压气体的静压作用及溶剂效应,体系的表观活化能随着气体压力的升高而逐渐降低,CO2的溶剂效应明显强于N2;利用Sestak-Berggren模型进行拟合,发现在不同压力的气体氛围中该模型与非等温测试得到的DSC曲线较为吻合,表明该体系在常压及高压气体存在下均符合自催化模型。

The non-isothermal curing kinetics of polyurethaneunder CO2 and N2 atmosphere in the pressure range of 0.1-6 MPa were studied using a high-pressure DSC.The Kissinger method and isoconversional method with two different integral equations were adopted to calculate the activation energy.Based on the non-isothermal measurements,the curing mechanism functions f(α)and kinetic parameters could be obtained by the Málek mehod.Then the curing kinetic equations of PU at different pressures of CO2 and N2 were determined,and the effects of high pressure CO2 and N2 on the curing process could also be investigated.The results indicated that the activation energy decreased with the increasing of gas pressures which could be explained by the solvent effect and static pressure effect,and high pressure CO2 is more beneficial to promote curing reaction than N2.Using the Sestak-Berggren model,it is found that the model is consistent with the DSC curve obtained by non-isothermal test in different pressure gas atmospheres,indicating the system conforms to the autocatalytic model in the presence of atmospheric pressure and high pressure gas.