热致液晶共聚酯60PHB/PEN的热降解动力学研究--(Ⅰ) 非等温热降解动力学

在氮气氛中采用热重分析的方法对热致液晶共聚酯60PHB／PEN的热降解动力学进行了研究。采用Friedman和Chang两种单一加热速率方法对活化能Ea、反应级数n和频率因子Z等降解反应动力学参数进行了分析。讨论了加热速率和计算方法对热稳定性及降解动力学参数的影响。     

纤维素油酸酯热性能及热降解动力学

利用热重法(TG)和差示扫描量热法(DSC)研究了不同取代度的纤维素油酸酯(CO)在氩气中的热降解及热降解动力学。为确定CO的热降解动力学参数,首先采用Kissinger法计算反应级数n,再利用Coats-Redfern法计算活化能Ea和频率因子A,计算结果适用于起始降解温度(Td)到最大降解速率温度(Tp)附近的温度范围。计算结果表明,CO热降解反应级数n随取代度的增加由2.9(S1)下降为1.4(S3);CO的Td和Tp均随取代度的增加而降低,说明CO的热稳定性随取代度的增加而降低;活化能Ea和频率因子A同样随取代度的增加而降低。     

微波辐射凝固天然橡胶硫化胶热降解动力学的研究

采用热分析法(TA)研究了微波辐射凝固天然橡胶(NR-m)和自然微生物凝固天然橡胶(NR-n)的硫化胶在氮气气氛中的热降解行为,为探索微波凝固天然胶乳这种新加工工艺提供了科学依据.采用Achar法和CoatsRedfern's法求出NR-m和NR-n硫化胶热降解反应中的机理函数,确定热降解反应中可能遵循的动力学机理,并得到了各步反应中的平均表观活化能Ea以及频率因子A等动力学参数.     

D,L-聚乳酸热降解动力学研究

通过热重分析研究了D,L-聚乳酸(PDLLA)在N2气氛中,不同升温速率条件下的热降解过程及其动力学行为.结果表明,PDLLA的主热降解过程为一级反应,当温度超过250℃时即发生明显降解,同时分别利用Ozawa-Flynn-Wall、Friedman和Freeman-Carroll方法对其动力学参数进行了测定,得到PDLLA的热降解活化能值为97.78kJ/mol.     

聚丙烯/煤泥复合材料热降解动力学研究

用热重分析法研究了聚丙烯(PP)/煤泥复合材料的热降解过程,采用Kissinger、Friedman和Flynn-WallOzawa等方法对PP/煤泥复合材料的热降解表观活化能(Ea)进行研究。结果表明,煤泥含量分别为5%(wt,质量分数,下同)、10%和20%时,在升温速率β为5℃/min时热降解起始温度T0较纯PP分别提高了4℃、7.48℃和12.62℃。并且随着煤泥含量的增加,复合材料的Ea呈现出先增加后降低的趋势,当煤泥含量为5%时达到最大,由Kissinger法计算得出Ea较纯PP提高了79.34kJ/mol。说明煤泥的加入使材料的热稳定性能得到了改善。     

ZR-VV电缆护套和绝缘材料热解动力学研究

采用热重分析（thermogravimetric analysis）的方法研究了阻燃聚氯乙烯电缆（ZR-VV）护套和绝缘材料在空气中的热降解行为，并采用Kissinger法和Flynn-Wall法计算了护套材料的热降解动力学参数．TG曲线表明，阻燃处理的聚氯乙烯电缆护套和绝缘材料热降解均可分为5个阶段，材料的热降解速率随升温速率的增加而增加．由Kissinger法和Flynn-Wall法计算得到阻燃聚氯乙烯电缆护套材料的降解平均活化能依次为102和118kJ／mol，绝缘材料的降解平均活化能为133和134kJ／mol。     

共聚甲醛的热降解行为及动力学

TGA结果表明三种CPOM(Y—M90、D-90EM和B—M90S)降解特征温度在氮气氛中均比空气氛中高70℃～100℃。这主要是由于在空气氛中聚甲醛的降解行为除了热裂解外,还存在自动氧化降解和氧化降解产物导致的酸解水解等降解方式,在较低的温度下由于空气中氧的作用,降解产物甲醛可被氧化成甲酸进而强化酸解水解作用,使CPOM的降解温度明显降低。用Freeman—Carroll方法研究了CPOM热降解动力学,计算得到的活化能和反应级数等参数在氮气氛中主要适用于350℃～385℃,质量损失区间在主要分解行为阶段(20％～70％);在空气和氮气氛中,D-90EM的n分别为0．36和1．06,差别最大,而Y—M90的n值分别为0．73和0．83,反应机制最为接近;三种CPOM在空气中n值以D-90EM和Y—M90差别最大,分别为0．36和0．73,而在氮气中B—M90S和D-90EM热降解接近一级反应,n值分别为1．08和1．06,降解机制最为相近。     

侧基含磷共聚酯的热降解动力学及热稳定性

采用不同的升温速率,用Kissinger法研究了聚酯(PET)和侧基含磷共聚酯(FR-PET)在氮气气氛中热降解动力学,采用时-温等效原理对其热稳定性进行了深入研究,等温热失重法和Kissinger法将寿命方程及动力学参数联系起来,确定了它们之间的关系。结果表明,阻燃剂的引入降低了PET整个热降解过程的平均活化能,并改变了反应级数,但使PET的热稳定性有所提高。两种方法所确定的寿命方程较为接近,Kissinger法更为简便、迅速,为材料寿命的预测提供了捷径。     

新型聚合物NSMA的热性能及热降解动力学

采用差示扫描量热仪和红外光谱仪研究了N-苯基马来酰亚胺、苯乙烯和马来酸酐三元共聚物(NSMA)的热性能,热降解过程和热降解动力学.结果表明,N-苯基马来酰亚胺可以有效地提高聚合物的热性能,合成的NSMA的玻璃化温度(Tg)达212℃;用Flynn-Wall-Ozawa法求得的NSMA热降解表观活化能为186.31kJ/mol,由Crane法求得热降解的反应级数n=1.0.     

聚砜酰胺基单聚合物复合材料的热性能及降解动力学

采用热重分析对作为耐高温材料使用的聚砜酰胺基单聚合物复合材料(PSA SPCs)进行热性能研究。通过计算积分程序分解温度(IPDT)和温度指数Ts分别评价材料的热稳定性和长期使用温度,通过计算温度指数Tzg来表征耐热性能。PSA SPCs的IPDT、Ts以及Tzg分别为1305℃,248℃和255℃,而PSA树脂材料相对应的参数值依次是1162℃,243℃和244℃,表明PSA SPCs的热性能优于PSA树脂材料。采用不同升温速率,分别用Flynn-Wall-Ozawa法和Kissenger法研究其热降解动力学,计算得到反应活化能(Ea)分别为152.26 k J/mol,146.85 k J/mol,优于PSA树脂材料的Ea值(133.54 k J/mol,127.88 k J/mol)。     

Thermal stability and thermal degradation kinetics of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate) blends

The kinetics of thermal degradation of poly(ethylene 2,6-naphthalate)/poly(trimethylene terephthalate) (PEN/PTT) blends with different weight ratio were investigated by thermogravimetry analysis from ambient temperature to 800 °C in flowing nitrogen. The kinetic parameters, including the activation energy E _a, the reaction order n, and the pre-exponential factor ln(Z), of the degradation of the PEN/PTT blends were evaluated by three single heating rate methods and advanced isoconversional method developed by Vyazovkin. The three single heating rate methods used in this work include Friedman, Freeman–Carroll, and Chang method. The effects of the heating rate, the calculation methods, and the content of the PEN component on the thermal stability and degradation kinetic parameters of the PEN/PTT blends were systematically discussed. The PEN/PTT blends which degraded in two distinct stages were stable under nitrogen, also, the maximum rate of weight loss increased linearly with increasing of heating rate and decreased with increasing of PEN content. The obtained kinetics data suggested that the introduction of PEN component increased the activation energy, enhanced the stability of the blend system, and affected the process of degradation of PEN/PTT blend.     

成核剂对PET/PEN共混体系热降解与结晶形态的影响

用热失重(TGA)、X射线(WAXS)和偏光显微镜(PLM)研究了三种成核剂对聚对苯二甲酸乙二酯/聚萘二甲酸乙二醇酯(PET/PEN)共混体系的热降解行为、结晶行为和形态的影响。结果表明,成核剂的加入,加速了PET/PEN共混物的降解;且DBS[1,3:2,4-二(亚苄基)-D山梨醇]对PET/PEN共混物的影响最大,CaCO3对PET/PEN共混物的影响最小;含有DBS的PET/PEN共混物形成了环带球晶,CaCO3与PET/PEN共混物同时结晶,且成核剂的加入使晶体形态更完善。用差减微分法研究了PET/PEN/成核剂共混体系热降解动力学,计算得到了活化能(E)和反应级数(n),计算得到的活化能关系为EPET/PEN>EPET/PEN/DBS>EPET/PEN/CaCO3>EPET/PEN/SB。     

Mechanochemical degradation treatment of TBBPA: A kinetic approach for predicting the degradation rate constant

Persistent organic pollutants (POPs) have been banned from production and use. The brominated flame retardant TBBPA is a type of POP and has been widely used in plastics to enhance their fire resistance. However, because the natural degradation of TBBPA is a difficult process, it is particularly important to propose an appropriate treatment method. Hence, the mechanochemical degradation of TBBPA is a feasible method because it does not require high temperature heating and does not produce secondary pollutants after the reaction is completed. In this study, we performed a series of TBBPA degradation experiments with a planetary ball mill and confirmed the degradation efficiency and the rate under various conditions. Then, we conducted a discrete element method (DEM) simulation to compute the collision energies in the ball mill. By comparing the degradation rate and collision energies, we revealed that the mechanochemical degradation rate of TBBPA can be predicted by a normal collision energy computed by DEM simulation. This kinetic approach enables us to predict the rate constant and consequently, the energy consumption for the mechanochemical treatment. The predictability of these parameters will encourage the further application of mechanochemical reaction in the field of POPs treatment.     

On the pyrolysis kinetics of scrap automotive tires

Pyrolysis kinetics of scrap tires of passenger car and truck have been investigated thermogravimetrically under heating rates of 5, 10, 20 and 30K/min and temperature range 373-1273K in nitrogen. The results show that the initial reaction temperatures are 482-521K for the tire of passenger car and 458-511K for truck tire. Both tires exhibit similar behaviors that the initial reaction temperature decreases, but reaction range and reaction rate increase when heating rate is increased. The overall rate equation for each tire can be modeled satisfactorily by a simple one equation from which the kinetic parameters such as the activation energy (E), the pre-exponential factor (A), and the reaction order (n) of unreacted material based on Arrhenius form are determined using Friedman's method. The results show that two tires behave similarly and the average kinetic parameters of two tires are E = 147.95 +/- 0.21kJ/mol, A = (6.295 +/- 1.275)x10(10)min(-1), and n = 1.81 +/- 0.18. The predicted rate equations compare fairly well with the measured data.     

多官能团环氧树脂体系的固化反应

采用非等温差示扫描量热（DSC）对多官能团环氧树脂体系固化反应进行了研究,确定了环氧树脂所用固化剂为甲基纳迪克酸酐（MNA）。对AG-70/MNA/2-乙基-4-甲基咪唑（EMI-2,4）环氧树脂体系在不同升温速率下的固化反应进行测试,根据DSC曲线,用温度-升温速率外推法,求出环氧树脂体系的三个特征温度,温度参数能为...     

升温速率对煤粉燃烧反应动力学的影响

采用热重分析法对不同升温速率(10、20、30℃/min)下的煤粉燃烧特性进行研究,由热重数据进行煤粉燃烧特征参数和动力学参数的计算,分析升温速率对煤粉燃烧特性的影响。结果表明:随着升温速率的升高,着火温度和燃尽温度随之升高。煤粉燃烧出现热滞后现象,反应动力学参数随升温速率的变化而不同。     

杂萘联苯聚醚砜酮/环氧树脂共混体系固化反应动力学

采用热熔法制备了杂萘联苯聚醚砜酮(PPESK)/环氧树脂(E-51)共混物,利用差示扫描量热仪(DSC)对共混物的固化反应动力学进行了研究。借助Ozawa和Kissinger等方法确定了PPESK增韧E-51体系的固化动力学参数,包括反应的表观活化能E,指前因子A和反应级数n;结果表明,采用新型高性能热塑性树脂PPESK增韧环氧树脂不仅在工艺上具有可行性,而且PPESK的加入降低了固化反应的表观活化能,促进了固化反应的进行。     

非等温DSC法研究复合材料用环氧树脂的固化反应

采用非等温DSC研究了一种复合材料用环氧树脂体系的固化反应。采用n级反应模型和Malek等转化率法确定了固化反应动力学方程,通过外推法优化其固化工艺,测试优化后工艺下制备的树脂浇铸体的固化度和力学性能。结果表明,n级反应模型与实验值差别较大;采用Malek等转化率法判断固化反应按自催化反应机理进行,在2.5～15℃/min升温速率下,自催化模型计算曲线与实验曲线吻合较好;优化确定其固化工艺为70℃/2h+110℃/2h,在该工艺下制备的浇铸体固化度达98.51%,拉伸强度和弯曲强度分别为75.11MPa和128.10MPa。     

Nonisothermal Reaction Kinetics of Commercial DOPO-modified Epoxy Novolac (PEN) and4,4'-Diaminodiphenylmethane ( DDM)

Nonisothermal reaction kinetics of a commercial DOPO-modified epoxy novolac (PEN) with 4,4'-diaminodiphenylmethane (DDM) was systematically investigated with a differential scanning calorimeter (DSC) according to the model-fitting and model-free advanced isoconversional methods.It was found that increasing the heating rate led the reaction exothermic peak to at a higher temperature with broadened areas,but the reaction enthalpy (-91-94kJ/mol) and the glass-transition temperatures of the cured resins (133.4-135.8 ℃) changed slightly.The global reaction activation energy determined with the Kissinger method was 53.6 kJ/mol,and the SB(m,n) model was confirmed to be able to well model the reaction rate.Furthermore,the effective activation energy as a function of conversion of epoxy groups was determined with the advanced isothermal conversional method (AICM),on the basis of which the reaction mechanisms was discussed in detail.     

先进复合材料用环氧树脂的固化反应和化学流变

用等温差示扫描量热法(DSC)研究了HD03环氧树脂在一定温度范围内的固化反应。试验结果表明,该环氧树脂体系的固化动力学符合自催化固化反应模型。由试验确定了模型中的动力学参数。发现在树脂的固化后期,固化反应由化学反应控制转变为扩散控制。用以绝对反应速率理论为基础的化学粘度分析模型研究了较高温度范围内HD03环氧树脂的等温粘度和变温的动态粘度变化。用MCR 300流变仪测量并计算了HD03环氧树脂的等温粘度和动态粘度。理论预测与试验结果相吻合。