Cure Kinetics of DGEBA with Hyperbranched Poly(3-hydroxyphenyl) Phosphate as Curing Agent Studied by Non-isothermal DSC

The cure kinetics of diglycidyl ether of bisphenol A （DGEBA） with hyperbranched poly （3-hydroxyphenyl） phosphate（HHPP） as the curing agent was investigated by means of non-isothermal differential scanning calorimetry （DSC） at various heating rates. The results were compared with the corresponding results by using 1,3-dihydroxybenzene（DHB） as a model compound. The results show that HHPP can enhance the cure reaction of DGEBA, resulting in the decrease of the peak temperature of the curing curve as well as the decrease of the activation energy because of the flexible --P--O-- groups in the backbone of HHPP. However, both the activation energy of the cured polymer and the peak temperature of the curing curve are increased with DHB as a curing agent. The cure kinetics of the DGEBA/HHPP system was calculated by using the isoconversional method given by Malek. It was found that the two-parameter autocatalytic model（Sestak-Berggren equation） is the most adequate one to describe the cure kinetics of the studied System at various heating rates. The obtained non-isothermal DSC curves from the experimental data show the results being accordant with those theoretically calculated.

ESTIMATION OF THE CRITICAL RATE OF TEMPERATURE INCREASE OF THERMAL EXPLOSION OF NITROCELLULOSE USING NON-ISOTHERMAL DSC

A method of estimating the critical rate of temperature increase of thermal explosion for the first orderautocatalytic decomposition reaction system using non-isothermal DSC is presented. Information is obtained on theincreasing rate of temperature in nitrocellulose containing 13.54% of nitrogen when the first order autocatalytic decomposition converts into thermal explosion.

Estimation of Critical Rate of Temperature Rise for Thermal Explosion of First Order Autocatalytic Decomposition Reaction Systems by Using Non-isothermal DSC

A method of estimating the critical rate of temperature rise for the thermal explosion of first order autocatalytic decomposition reaction systems by using non-isothermal DSC is presented. The information was obtained on the increasing rate of temperature for the first order autocatalytic decomposition of nitrocellulose containing 13.86% nitrogen converting into the thermal explosion.

Estimation of Critical Temperature of Thermal Explosion for Trinitromethyl Explosives by Non-isothermal DSC

Two general expressions and their six derived formulae for estimating the critical temperature（Tb） of thermal explosion for energetic materials（EMs） were derived from the Semenov＇s thermal explosion theory and eight non-isothermal kinetic equations via reasonable hypothesis. We can easily obtain the values of the initial temperature（T0i） at which DSC curve deviates from the baseline of the non-isothermal DSC curve of EMs, the onset temperature（Tei）, the exothermic decomposition reaction kinetic parameters and the values of Too and Te0 from the equation Toiorei=Tooore0＋α1β1＋α2β2＋...＋αL-2βi^L-2, i=1, 2, …, L and then calculate the values of Tb by means of the six derived formulae. The results obtained with the six derived calculating methods for six trinitromethyl explosives： bis（2,2,2- trinitroethyl-N-nitro） ethylene diamine（BTNEDA）, 2,2,2-trinitroethyl-4,4,4-trinitrobutyrate（TNETB）, bis（2,2,2- trinitroethyl） formal（BNTF）, bis（2,2,2-trinitroethyl-nitramine）（BTNNA）, 2,2,2-trinitroethyl-2,2,2-trinitroethyl-N- nitroamino acetate（TNTNNA） and tetrakis [2,2,2-trinitroethyl] orthoester（TTNOE） agree well with each other.

Estimation of Critical Temperature of Thermal Explosion for Energetic Materials Based on Non-isothermal Kinetic Equation dα/dt =A_0 exp(bT)[1+(T–T_0 )b]f(α)

Critical temperature（Tb） of thermal explosion for energetic materials is estimated from Semenov＇s thermal explosion theory and the non-isothermal kinetic equation da/dt=Aoexp（bT）[1＋（T-T0）b][（a） deduced via reasonable hypotheses, where To is the initial point of the deviation from the baseline of DSC curve. The final formula is （Tb-Te0）{ 1＋1/[1＋（ Tb-T00）b]}=1. We can easily obtain the initial temperature（T0/） and onset temperature（Tci） from the non-isothermal DSC curves, the values of Too and Tc0 from the equation TOi or ei=T00 or c0＋α1βi＋a2βi^2＋…＋aL-2L-2βiL-2, i=1,2,…L, the value of b from the equation： In[β/（Tei-T0i）]=ln[A0/G（a）]＋bTei, so as to calculate the value of Tb. The result obtained with this method coincides completely with the value of Tb obtained by Hu-Yang-Liang-Wu method.

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION

A kinetic equation of non-isothermal crystamzation was derived by extending Avrami's equation to the non-isothermal situation. More crystallization information can be obtained from this kinetic equation. The curves of non-isothermal and isothermal crystallizations were analysed and compared for poly (ethylene terephthalate) (PET), and the results were discussed.

ON A DIFFERENTIAL EQUATION FOR KINETICS OF NON- ISOTHERMAL CRYSTALLIZATION

A new differential equation was derived from the modified first-order kinetic model to describe the polymer crystallization processes. The crystallization experiments were carried out by means of DSC. Poly (ethylene terephthalate) resins were selected as the samples containing different catalysts. The relationships between the parameters obtained from the known Avrami equation and from one in the present paper were discussed. A method for applying the equation to determine the kinetic parameters from a constant heating and a constant cooling curve was proposed.

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION OF POLY (ETHYLENE TEREPHTHALATE) MODIFIED BY POLY (ETHYLENE GLYCOL)

The non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) modified by poly (ethlene glycol) (PEG) were determined by DSC. The dual linear regression method was used to evaluate the relationship between the reciprocal of t 1/2 ( the half life of crystallization) and the appropriate temperature variable. The parameters such as the activation energy (Ed) for transport, the equilibrium melting temperature (T_m^0),the nucleation parameter (ψ),themaximum crystallization temperature (T_(e, max)), and the kinetic crystallizability (G) for the copolyesters were obtained. The influence of the PEG content in PET chains on the parameters characterizing crystallization kinetics and crystallization thermodynamics was discussed.

等温DSC法研究RFI用环氧树脂固化动力学

为了预测固化反应的进程,采用STA 449C型差示扫描量热仪,用等温DSC法研究了室温下成膜、中温固化的RFI工艺用(E-44/E-21(6/4,质量比))/GA-327=100/40(质量比)环氧树脂体系在80、90、100、110、120℃下的固化过程,通过Matlab数据拟合良好性统计法得到了n级固化模型、自催化模型及复合模型方程中的各个参数值。根据R2和离差平方和SSE确定了适合的动力学模型。研究表明:该树脂体系的固化反应具有自催化和扩散控制的特征,低温下受扩散控制的影响更大;该体系的固化反应动力学符合自催化反应动力学模型,其表观活化能Ea为56.7 kJ/mol,指前因子A为1.18×107s-1,固化反应的反应级数m、n分别为0.529和1.561。

等温DSC法研究树枝状大分子PAMAM与环氧树脂的固化反应动力学

The curing process of dendritic polymer PAMAM with bis-phenol A epoxy resin was investigated using isothermal differential scanning calorimetry（DSC）,the mechanism of this reaction was autocatalytic.The data of two reaction rate constants k1,k2 and reaction orders m,n were obtained from Kamal equation.The overall reaction order m+n was between 2.07 and 2.29,the apparent activation energies of E1 and E2 were 59.79 kJ/mol and 56.51 kJ/mol, respectively.The reaction entered into a diffusion controlled stage at the conversion of 50%,experimental data and theoretic curve had deviation at this time.The reaction conversion,at which the deviation occurred,decreased with lowering curing temperature.

用非等温DSC估算硝化棉热爆炸的临界温升速率(英文)

提出了用非等温DSC估算一级自催化分解反应体系热爆炸的临界温升速率(dT/dt)Tb方法,得到了NC(11.92%N)由一级自催化分解过渡到热爆炸时的(dT/dt)Tb值。

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。

关于从不同恒速降温条件下的DSC曲线峰温计算结晶/凝固反应动力学参数的一点注释

提出了从不同恒速降温条件下的DSC曲线峰温计算放热结晶/凝固反应动力学参数(表观活化能E和表观指前因子A)的方法和计算式。比较了用该计算式与Kissinger方程计算E和A值的适用性条件,认为Kissinger法不适于计算题称反应的动力学参数。因此,对题称反应,用Kissinger法所得的负E值,是不合理的。

从恒速升温速率下的DSC曲线峰温计算含能材料放热分解反应动力学参数的理论和数值方法(英文)

根据Kooij公式和van′t Hoff公式,从恒速升温速率下的DSC曲线峰温导出了计算含能材料放热分解反应动力学参数的两个数学表达式,提出了计算相应动力学参数的数值方法。对1,3,5-三硝基-1,3,5-三氮杂环己酮-2(Keto-RDX),由导出的两个表达式、Kissinger法、Ozawa法、Tang法、Hu-Gao-Zhang法、非线性等转化率积分法(NL-INT)所得的活化能E值彼此接近,表明Kooij′s公式中的a值取0.5,van′t Hoff公式的b值取0.003,可得到合理的动力学参数。

用DSC研究尼龙69的非等温结晶和结晶动力学

本文用ＤＳＣ方法研究了尼龙６９在不同等速降温速率下的结晶过程，并利用由等温Ａｖｒａｍｉ方程推导得到的等速降温非等温结晶方程，研究了其结晶动力学。结果表明，随降温速率β增大，结晶温度向低温偏移，并与β成直线关系，通过ｌｎ［－ｌｎ（１－Ｃｒ（Ｔ））］～ｌｎβ曲线求得了不同温度下的Ａｖｒａｍｉ指数，其值为２．９±０．２，具有良好的一致性，说明把非等温结晶方程应用于尼龙６９结晶过程进行动力学处理时，把ｎ视为常数是合理的。并根据结晶方程，求得了尼龙６９的结晶动力学参数人ｎ、Ｋ（Ｔ）、ｔ＿（１／２）（Ｔ）．

用DSC曲线数据估算硝化棉的C_nB和表观经验级数自催化分解反应热爆炸临界温升速率

采用非线性约束优化问题的信赖域算法,由不同升温速率(β)条件下硝化棉(NC,14.14%N)的DSC曲线数据得到了NC的n级自催化分解反应(Cn B)和表观经验级数自催化分解反应的动力学参数和动力学方程。并由计算得到的β→0时的onset温度(Te0),热爆炸临界温度(Tb),相应于Tb时的转化率(αb)和动力学参数值获得了NC的热爆炸临界温升速率值。结果表明,在非等温DSC条件下NC分解反应可用表观经验级数自催化反应速率方程dα/dt=1015.76exp(-170830/RT)(1-α)0.95+1015.76exp(-159070/RT)α1.81(1-α)1.16描述。NC由自催化分解转向热爆炸时的热爆炸临界温升速率值为0.060K/s。

秸秆等温干燥热质传输机理研究(Ⅰ)——TG/DSC实验分析

对干玉米秸秆进行了元素分析和组分分析;通过热重分析仪和差示扫描量热仪对不同含湿量的粉末状玉米秸秆进行等温干燥实验,通过对热流曲线积分得到干燥需热量并对其进行定量研究。结果表明:以最大干燥速率为分界点,玉米秸秆干燥过程可分为升速干燥段和降速干燥段;热流曲线与干燥失水过程有明显的对应关系;90℃干燥1kg含湿量20%～40%的湿秸秆需热量在380～620kJ之间;50～110℃干燥含湿量25%秸秆的需热量在210～610kJ之间。

用非等温DSC估算一些呋咱环化合物的热爆炸临界温度(英文)

通过合理假设,从谢苗诺夫(Semenov)热爆炸理论和8个非等温动力学方程,导出了估算含能材料(EMs)热爆炸临界温度(Tb)的2个通式和它们的6个派生式。从EMs的非等温DSC曲线可获得DSC曲线偏离基线的起始温度(T0)、onset温度(Tei)和放热分解反应的动力学参数。由方程T0ior ei=T00 or e0+a1βi+a2βi2+…+aL-2βiL-2,i=1,2,…,L可得到T00和Te0值,随后用6个派生式可计算Tb值。对1,4,5,8-四硝基-1,4,5,8-四氮杂双呋咱[3,4-c:3′,4′-h]十氢化萘,1,4,5,8-四氮杂双呋咱[3,4-c:3′,4′-h]十氢化萘,1,3,4-三硝基咪唑烷酮[4,5-b]呋咱[3,4-e]哌嗪,咪唑烷酮[4,5-b]呋咱[3,4-e]哌嗪,1,3,4,8-四硝基咪唑烷酮[4,5-b]呋咱[3,4-e]哌嗪,1,4,5,8-四硝基-1,4,5,8-四氮杂萘呋咱[3,4-b]十氢化萘,1,3,5-三硝基-1,3,5-三氮杂呋咱[3,4-f]环庚烷,由6个派生式所得的Tb值甚接近。

从DSC曲线数据计算/确定含能材料自催化分解反应动力学参数和热爆炸临界温升速率的方法

为应用热爆炸临界温升速率(dT/dt)Tb评价含能材料(EMs)的热安全性,得到计算(dT/dt)Tb值的基本数据,用合理的假设,由Semenov的热爆炸理论和9个自催化反应速率方程[dα/dt=Aexp(-E/RT)α(1-α)(I),dα/dt=Aexp(-E/RT)(1-α)n(1+Kcatα)(II),dα/dt=Aexp(-E/RT)[αa-(1-α)n](III),dα/dt=A1exp(-Ea1/RT)(1-α)+A2exp(-Ea2/RT)α(1-α)(IV),dα/dt=A1exp(-Ea1/RT)(1-α)m+A2exp(-Ea2/RT)αn(1-α)p(V),dα/dt=Aexp(-E/RT)·(1-α)(VI),dα/dt=Aexp(-E/RT)(1-α)n(VII),dα/dt=A1exp(-Ea1/RT)+A2exp(-Ea2/RT)(1-α)(VIII),dα/dt=A1exp(-Ea1/RT)+A2exp(-Ea2/RT)α(1-α)(IX)]导出了计算(dT/dt)Tb值的9个表达式.提出了从不同恒速升温速率(β)条件下的差示扫描量热(DSC)曲线数据计算/确定EMs自催化分解反应的动力学参数和自催化分解转向热爆炸时的(dT/dt)Tb的方法.由DSC曲线数据的分析得到了用于计算(dT/dt)Tb值的β→0时的onset温度(Te0),热爆炸临界温度(Tb)和相应于Tb时的转化率(αb).分别用线性最小二乘法和信赖域方法得到方程(I)和(VI)及方程(II)-(V)和方程(VII)-(IX)中的自催化分解反应动力学参数.用上述基础数据得到了EMs的(dT/dt)Tb值.结果表明:(1)在非等温DSC条件下硝化棉(NC,13.54%N)分解反应可用表观经验级数自催化反应速率方程dα/dt=1015.82exp(-170020/RT)(1-α)1.11+1015.82exp(-157140/RT)α1.51(1-α)2.51描述;(2)NC(13.54%N)自催化分解转向热爆炸时的(dT/dt)Tb值为0.103K·s-1.

环氧树脂固化动力学的非等温DSC研究

用非等温DSC对环氧树脂在动态升温过程中的固化动力学进行了研究,采用Kissinger方程对固化动力学模型参数中固化反应活化能、反应级数和指前因子进行了计算,并用Ozawa法对固化反应活化能进行了验证,计算结果表明,EP/DDS固化反应符合n阶固化动力学模型,结合不同升温速率下的特征温度,对环氧树脂的固化条件进行了优化。