高聚物的低温动态力学性能

用ＤＭＡ（动态机械热分析仪）研究了几种高聚物的低温动态力学性能,测定了样品的动态力学性能参数,并且应用动态力学性能的ＴＴＳ（时温叠加）原理,求得了ＷＬＦ方程的常数Ｃ１和Ｃ２,由Ｃ１和Ｃ２进一步计算出材料的脆性参数,同时从分子结构角度解释了本文所研究试样之间贮能模量和脆性参数的差别。     

无限接近临界点的克拉佩龙方程和临界参数计算

本文将无限接近临界状态的克拉佩龙（Ｂ．Ｐ．Ｅ．Ｃｌａｐｅｙｒｏｎ）方程与安托因（Ｃ．Ａｎｔｏｉｎｅ）公式相结合，导出了纯物质的临界温度计算公式，并以有机同系物直链烷烃为例，计算了乙烷～庚烷的临界参数（临界温度Ｔ_ｃ、临界压力Ｐ_ｃ和临界体积Ｖ_（ｍ，ｃ））。     

NR/BR并用硫化胶热氧降解动力学研究

用热重分析法（ＴＧ）研究了天然橡胶／顺丁橡胶（ＮＲ／ＢＲ）并用硫化胶在室温至５００℃范围的热氧降解动力学。由Ｃｏａｔｓ－Ｒｅｄｆｅｒｎ法求得了两个降解阶段的反应级数和活化能，用Ｄｏｙｌｅ法计算了并用胶不同降解程度的表观活化能和频率因子，获得了相应的反应速率常数－温度（ｋ－Ｔ）关系，并用Ｆｕｏｓｓ方程计算了ＮＲ和ＢＲ氧化的活化能。     

聚氯乙烯乳胶机械稳定性

采用稳态剪切的方法测定聚氯乙烯（ＰＶＣ）乳胶的机械稳定性，并以临界凝结时间ｔ＿ｃ表征机械稳定性与剪切速率γ、乳胶含固率φ及温度Ｔ的关系。结果表明，随剪切速率的增大，含固率增加及温度升高，乳胶的机械稳定性均降低。根据实验数据回归出经验式：ｔ＿ｃ＝ｅｘｐ（－３４．７５－１．９４０ｌｎγ＋２２．３１φ＋１．５７２×１０￣４／Ｔ－１．１８５×１０￣４φ／Ｔ），其计算值与实验值较吻合。     

应用毛细管流变仪研究ABS／PVC塑料合金的稳定性

应用毛细管流交仪研究了ＡＢＳ／ＰＶＣ塑料合金的稳定性。发现合金的对数表观粘度（Ｉｎηａ）与受热时间（ｔ）之间为折线关系；对数稳定时间（Ｉｎｔ）与绝对温度的倒数（１／Ｔ）之间为直线关系。同时对合金的４种稳定体系作了稳定时间、分解速率以及颜色变化综合考查，确定了最佳稳定体系。     

沉淀铁挤条F-T合成催化剂WGS反应考察

采用固定床积分反应器， 在工业条件下 （５００ ｈ－ １， １ ＭＰａ～２．６ ＭＰａ）， 对挤条Ｆｅ－Ｃｕ－Ｋ工业催化剂进行了水煤气变换反应性和ＦＴ反应产物分布链增长几率的考察． 在稳态下， 保持一定的轴向温度分布， 求得宏观动力学方程， 与实验数据符合较好．     

二元复合体系／大庆原油间的动态低界面张力研究

大庆馏份油经汽相氧化、皂化制得的石油羧酸盐［１］，加减后构成的复合体系，在不外加助剂醇情况下，可以和大庆原油形成动态低界面张力（ＬＩＦＴ）。本文探讨了动态ＬＩＦＴ形成的原因，并研究了盐含量，碱含量对复合体系／大庆原油间动态ＬＩＦＴ的影响。结果表明，低界面张力主要是石油羧酸盐活性剂的贡献，而动态ＬＩＦＴ过程是由水相中碱与原油中的有机酸反应生成的界面活性物质引起的。在某一含量范围内，随ＮａＣｌ或ＮａＯＨ含量增加，动态ＬＩＦＴ曲线移向低ＩＦＴ区，ＮａＯＨ对ＩＦＴ值的影响更显著。     

F型环氧树脂的NMR表征

用核磁共振波谱技术对两种Ｆ型环氧树脂的结构进行了表征,并通过二维１Ｈ—１Ｈ相关谱（ＣＯＳＹ）及１Ｈ—１３Ｃ化学位移相关谱（ＨＥＴＣＯＲ）对１Ｈ、１３Ｃ谱中各共振峰进行了指认。     

铅系复合钙钛矿Pb（Fe1／2Ta1／2）O3铁电陶瓷的介电弛豫特性

用普通合成法制备了纯钙钛矿结构相的Ｐｂ（Ｆｅ１／２Ｔａ１／２）Ｏ３（ＰＦＴ）陶瓷，并进行了９００℃退火热处理。对其介电性质测试结果表明，未热处理与热处理过的ＰＦＴ陶瓷在０．１￣１００ＫＨｚ频率下均表现出介电弥散性转变。未热处理的ＰＦＴ陶瓷最大介电常数对应的温度（Ｔ０）不随测量频率变化；热处理过的ＰＦＴ陶瓷在此频率范围Ｔ０值表现出明显的频率依赖性（频率色散），即△Ｔ０＝５℃。由此可以认为ＰＦＴ是弛豫     

铅系复合钙钛矿Pb（Fe_（1／2）Ta_（1／2））O_3铁电陶瓷的介电弛豫

用普通合成法制备了纯钙钛矿结构相的Ｐｂ（Ｆｅ＿（１／２）＝Ｔａ＿（１／２））Ｏ＿３（ＰＦＴ）陶瓷，并进行了９００℃退火热处理。对其介电性质测试结果表明，未热处理与热处理过的ＰＦＴ陶瓷在０．１～１００ｋＨｚ频率下均表现出介电弥散性转变。未热处理的ＰＦＴ陶瓷最大介电常数对应的温度（Ｔ＿０）不随测量频率变化；热处理过的ＰＦＴ陶瓷在此频率范围Ｔ＿０值表现出明显的频率依赖性（频率色散），即ΔＴ＿０＝５℃。由此可以认为ＰＦＴ是弛豫铁电体。ＸＲＤ结果表明，未热处理的ＰＦＴ陶瓷无超晶格衍射；而热处理过的ＰＦＴ陶瓷则有较弱的（１１１）超晶格衍射。利用有序－无序转变理论及超顺电结构模型对其结构与性质进行了探讨。     

Vitrification effect on the curing reaction of epoxy resin

Summary The curing reaction of diglycidyl ether of Bisphenol A(DGEBA) with triethylene tetramine(TETA) was studied by the differential scanning calorimetry(DSC). The reaction was affected as the vitrification occurred when the glass transition temperature(T_g) of the reaction mixture exceeded the curing temperature. In order to describe the curing reaction in the rubbery state as well as in the glassy state, the reaction kinetic equation containing the generalized WLF equation term was proposed and the parameters were determined from the DSC data.Nomenclature a_T time temperature shift factor, dimensionless - A_T temperature dependent frequency factor, /sec - A_Tg temperature dependent frequency factor at T_g, /sec - A_To temperature dependent frequency factor at T_g, /sec - A empirical parameter in temperature dependent frequency factor, dimensionless - B empirical parameter in temperature dependent frequency factor, K - C₁ empirical parameter in the generalized WLF equation, dimensionless - C₂ empirical parameter in the generalized WLF equation, K - D correction parameter in temperature dependent frequency factor, K - E activation energy, cal/mole - E_x/E_m ratio of lattice energies for crosslinked and uncrosslinked polymer, dimensionless - F_x/F_m ratio of segmental mobilities for crosslinked and uncrosslinked polymer, dimensionless - H_t cumulative heat generated up to time t, cal/g - H_RXN heat of reaction under complete conversion, cal/g - n reaction order, dimensionless - S _r scan rate of the DSC experiment, °C/sec - t time, second - T temperature, K - T_g glass transition temperature of the partially cured reaction mixture, K - T_go glass transition temperature of uncured reactant, 253 K - X conversion, dimensionless     

Modeling of dynamic mechanical properties of vulcanized fluoroelastomer

The dynamic mechanical properties of a vulcanized fluoroelastomer (FKM) were studied over a range of temperatures and shear frequencies. Dynamic mechanical analysis and differential scanning calorimetry were used for the purpose of the study. A model was developed in order to describe FKM's viscoelastic behavior at various temperatures. The model was fitted to experimental data using an algorithm, which was developed for this purpose. As a result the FKM discrete relaxation spectrum at two reference temperatures was obtained, as well as the Williams‐Landel‐Ferry (WLF) equation parameters or the activation energy equivalent. Further on, the model was applied on storage modulus and loss tangent values obtained from the experiments, during which the temperature increased linearly. It was observed that the WLF equation fits well with the results during the glass transition, while the Arrhenius‐type relationship predicted too rapid decrease of the storage modulus during the glass transition. The master curves were constructed using the previously calculated WLF parameters and the activation energy equivalent. The developed model may be readily applied for the prediction of the numerous FKM compounds' frequency–temperature behavior using the dynamic mechanical properties obtained from either isothermal or low linear heating rate program measurements. POLYM. ENG. SCI., 47:2085–2094, 2007. © 2007 Society of Plastics Engineers     

Stress Relaxation Modulus of a Commercial Glass

The stress relaxation modulus in compression of a container glass was investigated over a wide range of strain, time, modulus, and temperature. The glass is a linear viscoelastic liquid up to 2% strain, and the modulus is a smooth function of time, with no pseudorubbery plateau apparent down to a modulus of 10° dynes/cm². The data cover 4 decades in time and a range of almost 100°C above the glass transition, T ₀ =536°C. Within experimental error, changes in temperature simply shift the modulus-vs-time curve along the time axis without altering its shape. This behavior implies that the same mechanism controls both the bulk and shear spectra. The shift factors fit the WLF equation well with values for the parameters c₁ and c₂ of 16.7±0.2 and 345±5°C, respectively. Data from the literature for silicate glasses agree with these parameters.     

Aging of the Binders GAP-N100 and HTPB-IPDI Investigated by Torsion-DMA

The aging of the binders GAP-N100 and HTPB-IPDI was investigated by DMA in torsion mode to find out the changes in the storage shear modulus G′(ω), loss shear modulus G″(ω) and in the glass transition temperature T_G. The forced sinusodial deformation method was used with measuring frequencies between 0.1 Hz and 56.2 Hz. A measurement temperature range between −100°C and +50°C was applied. The DMA instrument was a Rheometrics Dynamical Spectrometer, type RDS II/7700. Non-aged GAP-N100 shows a well defined steep glass transition between −40°C and −25°C, which is found with aged samples also but shifted to higher temperatures. The glass transition of the binder HTPB-IPDI lies between −70°C and −10°C, but HTPB-IPDI has not a well defined glass transition. With aging it looses its glass transition, which can be seen by a smoothing out of the transition step in the curve G′(ω)=f(T). The behaviour and the differences of these binders are explainable on a molecular basis. The systematic shift of the glass transition temperature of the non-aged and aged GAP-N100 as well as of the non-aged HTPB-IPDI is describable by the Williams-Landel-Ferry equation. This equation was used to extrapolate the values of the glass transition temperatures to shear rates possible during operational use of propellants.     

Temperature and frequency dependent rheological behaviour of carbon black filled natural rubber

Abstract

The temperature and frequency dependent viscoelasticity of carbon black filled rubber is investigated. Temperature sweep and frequency sweep dynamic mechanical analysis tests are performed to investigate the frequency dependent glass transition temperature and to identify the thermorheological nature of the material. The test results show that master curves of dynamical properties can be constructed by horizontal shifts along the frequency axis alone and cover a frequency range of 21 decades, verifying the material’s thermorheological simplicity. This simplicity is confirmed by van Gurp–Palmen and Cole–Cole plots. Moreover, the temperature dependence of the shift factor is modelled well by both the Williams–Landel–Ferry equation and the Arrhenius equation.     

Dielectric analysis of the cure of thermosetting epoxy/amine systems

A low molecular weight epoxy resin is cured isothermally with an aromatic amine hardener, and the dielectric properties are measured as a function of the frequency, reaction time, and cure temperature. At specific stages in the cure, small samples from the reacting mixture are quenched and subsequently analyzed for the glass transition temperature and epoxy group conversion by differential scanning calorimetry. In this manner, the change In dielectric properties can be directly correlated with the network structure. The ionic conductivity is modeled as a function of the cure temperature and the cure-dependent glass transition temperature using a Williams-Landel-Ferry (WLF) relation. Combining this WLF relation with the DiBenedetto equation, a comprehensive model relating conductivity with the extent of reaction and cure temperature has been developed.     

BA9913环氧树脂固化动力学和TTT图

以BA9913树脂的全动态DSC扫描实验为基础,结合半经验的唯象模型获得了基于唯象模型的高韧性环氧(牌号:BA9913)树脂的固化动力学参数,建立相应的动力学模型,并测定了BA9913树脂在100℃时保温不同时间后的凝胶固化度。利用Di Benedetto方程研究了该等温条件下BA9913树脂固化度与加热时间的关系,得到其玻璃化转变温度与固化时间的关系表达式。采用测凝胶储能模量的方法得到了BA9913树脂凝胶时的固化度和玻璃化转变温度之间的关系,绘制了BA9913树脂的TTT图。在此基础上对T300/BA9913的固化工艺进行了优化,并研究了优化前后T300/BA9913复合材料的内部质量、基本力学性能及玻璃化转变温度。     

Dynamic Mechanical Behavior of PBX

The dynamic mechanical properties of PBX1314 and its binder are systematically investigated. Based on split‐Hopkinson pressure bar technique, the experimental results of PBX1314 and its binder are obtained under high strain rate. A constitutive theory is developed for modeling the mechanical response of dynamically loaded PBX1314 binder. To accomplish this aim, the PBX1314 binder is assayed by relaxation tests at different temperatures, in order to apply the time‐temperature superposition principle (TTSP) and raise the master curves, based on WLF equation. The rate dependence of mechanical response of the polymer binder is accounted for by a generalized Maxwell viscoelasticity model. The basis for this work is Mori and Tanaka's effective medium theory. The grains in this analysis are assumed to be spherical and uniformly distributed in the binder. The relaxation constitutive relations of particulate reinforced composites are investigated by Laplace transformation and the corresponding principle. The theoretical prediction coincides with experimental results.     

A reaction order functional relationship with the Williams–Landel–Ferry equation in curing kinetics

A methodology is presented to obtain a kinetic model for curing reactions, from conversion against time and the glass‐transition temperature versus conversion data. Isothermal runs for a cyanate ester resin from 140 to 190°C, reported previously, were evaluated. The approach utilizes the conversion measurement time derivatives that allow following the estimated parameters' trends: the rate constant and the reaction order, in this case. An autocatalytic model was found, and the rate constants were truly constant along the experiments; thus, their Arrhenius parameters were evaluated. The methodology allowed constructing a master curve relating the variable reaction order with a temperature difference (reaction and glass transition) explained by the Williams–Landel–Ferry (WLF) equation. Four parameters describing the reaction order variation, two related to an exponential‐like behavior and two required by the WLF equation, allowed describing the whole experimental set accurately. POLYM. ENG. SCI., 54:1900–1908, 2014. © 2013 Society of Plastics Engineers