探讨物料工业干燥动态特性的新方法

针对小质量物料干燥动态过程恒速率干燥阶段和降速率干燥阶段，提出了用偏差活化能的方法来避免寻找该两个干燥阶段临界湿分点的困难，并从物理化学的概念推导出了理论动态数学模型，建立了物料干燥动态特性实验台，以实验数据验证模拟结果，效果较好。研究结果表明，利用物料干燥过程偏差活化能的变化特性来研究物料的工业干燥动态特性和干燥机理是可行的。     

Prediction of compressive strength of fly ash concrete by new apparent activation energy function

A new prediction model using apparent activation energy is proposed to estimate the variation of compressive strength of fly ash concrete with aging. After analyzing the experimental result with the model, fly ash replacement content and water-binder ratio influence on apparent activation energy was investigated.According to the analysis, the model provides a good estimation of compressive strength development of fly ash concrete with aging. As the fly ash replacement content increases, limiting relative compressive strength and initial apparent activation energy increase. Concrete with water-binder ratio smaller than 0.40 gives nearly constant limiting relative compressive strength and initial apparent activation energy when analyzed with various water-binder ratios. However, concrete with water-binder ratio larger than 0.40 increases limiting relative compressive strength and initial apparent activation energy.     

物料温度和几何尺寸对动态干燥偏差活化能的影响

利用偏差活化能方法研究物料工业干燥动态特性和探索干燥机理的有效途径。通过实验和理论分析，研宛了被干燥物料的偏差活化能随其几何尺寸变化的规律，以及相同几何尺寸时偏差活化能随干燥环境温度变化的关系。研究表明，物料在干燥过程中，不同几何尺寸的试样其偏差活化能均呈现波动趋势，环境温度从低温到高温变化过程中出现偏差活化能最低的环境温度最佳区域。并非干燥环境温度越高，干燥率越高；在温度较低的干燥环境下，物料从泥状到小几何尺寸时，偏差活化能变化不大；偏差活化能随着被干燥物料几何尺寸的减小而降低，相对偏差活化能随着干燥温度的升高而较快地接近1。     

丁苯橡胶老化表观活化能的实验研究

进行了丁苯橡胶在海水中和热空气中的加速老化实验,测试了老化过程中的硬度和拉伸性能,得到了不同指标测定的老化活化能。结果表明：丁苯橡胶在海水中和热空气中老化时,断裂伸长率的表观老化活化能分别为49.65 kJ/mol、62.22 kJ/mol,100%定伸应力变化的表观活化能分别为45.23 kJ/mol、64.35 kJ/mol,硬度的表观活化能分别为85.45 kJ/mol7、3.21 kJ/mol。     

Determination of the apparent activation energy of one concrete by calorimetric and mechanical means: Influence of a superplasticizer

An instrument has been developed to perform calorimetric tests on concrete in isothermal conditions using 0.11×0.22-m cylindrical samples. The purpose of this article is to determine the apparent activation energy of one concrete as a function of temperature (10, 20 and 40 °C) using this technique and to compare it with that obtained by a mechanical means in order to validate the hypothesis made in maturity measurements, according to which the apparent activation energy values are assumed to be equivalent. The two means give relatively similar results (with differences of the order of 3 kJ/mol). It also seems possible to use a single apparent activation energy value over the entire temperature range (10-40 °C). Lastly, the effect of a superplasticizer on the apparent activation energy is examined, and it appears that its role is relatively small in the case of the concretes studied here.     

Structural relaxation and dynamic fragility of freely standing polymer films

In addition to a tremendous reduction in the glass transition temperature, dielectric spectra of freely standing films reveal two other intriguing features: a temperature dependent asymmetric broadening of the structural relaxation peak towards lower temperatures and a reduction of the dynamic fragility down to the monomer limit. We verified that this experimental evidence is a manifestation of a gradient of glass transition temperatures across the film thickness induced by an enhanced molecular mobility at the two free surfaces of the membrane. As a direct implication of the peculiar features just described, the properties of freely suspended membranes neither correspond to those in bulk nor to a simplified scenario where the structural relaxation peak is merely shifted towards lower temperatures.     

Determination of the degradation apparent activation energy of acrylonitrile/acrylic acid copolymers

Acrylonitrile/acrylic acid copolymers were prepared by H₂O/dimethyl formamide suspension polymerization technique. Differential scanning calorimetry was used to investigate the degradation of acrylonitrile/acrylic acid copolymers in air. The apparent activation energy of degradation of the copolymer was calculated with the Kissinger method. Effects of copolymerization conditions on the apparent activation energy of copolymer were studied. It has been found that increasing the dimethyl formamide concentration in the solvent mixture led to a gradual increase (97.3–149.4 kJ mol^?1) in the apparent activation energy of degradation of the acrylonitrile/acrylic acid copolymers. The apparent activation energy decreases with increase in acrylic acid concentration, and this change became less prominent as the acrylic acid/acrylonitrile weight ratio is more than 5/95. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4668–4671, 2006     

Something about amber: Fictive temperature and glass transition temperature of extremely old glasses from copal to Triassic amber

In previous work we successfully used a stable Dominican amber to investigate the sub-glass transition dynamics of an organic glass with extremely low fictive temperature. The results provided an incentive to seek other stable ambers with lower values of fictive temperature. In the present work, a series of fossil resins from different locations, and ages ranging from approximately 100 years–230 million years, has been investigated using differential scanning calorimetry. The measurement results show the thermal signatures for each fossil sample: copals are unstable, and have lower glass transition temperatures than the amber samples. For the amber samples, there is not a systematic age dependence for the amber's glass transition temperature. Furthermore, even for the same sort of amber, the thermal properties can be different for different samples. The stability of the fossil resins was studied and glass transition temperatures were determined. For the stable samples, fictive temperature was also determined.     

Strength development of mortars containing ground granulated blast-furnace slag: Effect of curing temperature and determination of apparent activation energies

The strength development of mortars containing ground granulated blast-furnace slag (ggbs) and portland cement was investigated. Variables were the level of ggbs in the binder, water-binder ratio and curing temperature. All mortars gain strength more rapidly at higher temperatures and have a lower calculated ultimate strength. The early age strength is much more sensitive to temperature for higher levels of ground granulated blast-furnace slag. The calculated ultimate strength is affected to a similar degree for all ggbs levels and water-binder ratios, with only the curing temperature having a significant effect. Apparent activation energies were determined according to ASTM C1074 and were found to vary approximately linearly with ggbs level from 34 kJ/mol for portland cement mortars to around 60 kJ/mol for mortars containing 70% ggbs. The water-binder ratio appears to have little or no effect on the apparent activation energy.     

Copolymerization kinetics of poly(acrylonitrile‐ran‐2‐ethenyl‐pyridine) and its degradation apparent activation energy

2‐Ethenyl‐pyridine (EPD) was first used to successfully copolymerize with acrylonitrile (AN) in a H₂O/dimethyl formamide (DMF) mixture by using azobisisobutyronitrile as the initiator. Kinetics of copolymerization and degradation of poly(AN‐ran‐EPD) were discussed. The kinetic equation of copolymerization and the apparent activation energy of degradation of poly(AN‐ran‐EPD) were obtained. In H₂O‐rich reaction medium, copolymerization followed the suspension polymerization more, but in DMF‐rich reaction medium, copolymerization followed the solution polymerization more. Increase in DMF concentration in the solvent mixture lead to a rapid increase in the degradation apparent activation energy. The apparent activation energy decreased quickly with an increase in EPD concentration, and such a change became less prominent as the molar ratio of EPD/AN went beyond 3/100. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Reactivity assessment of coals via a weighted mean activation energy

A method has been developed for describing the reactivity or combustibility of solid fuels, such as lignite, bituminous coals and petroleum coke, in terms of a weighted mean apparent activation energy, derived from simultaneous $\text{TG}\text{DTG}$ readings on a 20 mg sample heated at a constant rate in a flowing air atmosphere. It is proposed that this quantity, labelled E_m′, could supplant the established method which involves recording several temperatures on the DTG (burning profile) curve.     

阴离子型微乳液的电导活化能及洗涤效果

微乳体系是热力学稳定体系，能自发形成，这为开发浸泡型洗涤剂提供了可能。通过测定不同温度下0／7／型微乳液的电导率，计算体系电导活化能，发现该体系活化能随含水量的增加呈“U”型曲线变化。电导活化能与洗涤效果之间有一定的关系。m(SDS)：m(正丁醇)：m(二甲苯)：m(水)=5：8：2．5：24．5组成的微乳液作为浸泡型洗涤剂，对原油污染的纯棉白布洗净度为75％。在表面活性剂的质量分数相同的情况下，微乳体系的浸泡洗涤效果最好。     

Interaction Between P(VC-VA) and SAN Copolymer Blends Investigated by Thermal Analysis

Miscibility and activation energy of the binary polymer system consisting of Poly (vinyl chloride-vinyl acetate)/Poly (styrene-acrylonitrile) of various compositions (100/0, 85/15, 75/25, 50/50, 25/75, 15/85, 0/100) has been investigated by Differential Scanning Calorimeter (DSC). The interaction parameters were calculated from the measurements based on glass transition temperature of the blends. The thermal stability and activation energy of the blends was calculated using Doyle's method. The results suggest that the extent of partial miscibility of the two components is very limited.     

GAP/PTPET弹性体的交联与热性能研究

采用点击化学反应制备了GAP(叠氮缩水甘油聚醚)/PTPET(端炔基环氧乙烷–四氢呋喃共聚醚)弹性体,通过平衡溶胀法和DSC-TG(差热–热重)表征了弹性体的交联与热性能。在不同增塑比条件下,研究了不同配比的GAP/PTPET弹性体的交联密度、玻璃化转变温度(T_g)和热分解表观活化能。结果表明:在相同增塑比条件下,GAP/PTPET弹性体的交联密度随反应物中PTPET含量的增大而呈增大的趋势;增塑比为2.6时,弹性体有较高的交联密度;GAP/PTPET弹性体中软段的T_g偏高于原材料PTPET中软段的T_g;在相同增塑比条件下,随PTPET质量分数的增大,弹性体中软段的T_g减小。GAP/PTPET弹性体的热分解分为3个阶段,第一阶段和第二阶段的热分解表观活化能分别为122.2kJ/mol和137.4kJ/mol,均低于GAP均聚物的热分解表观活化能。     

环氧树脂密度与二面角扭转能的仿真计算

基于COMPASS分子力场,利用分子动力学模拟方法和Materials Studio软件建立了低固化度交联耦合的双酚A型环氧树脂交联结构模型,并利用环氧树脂交联体系模型模拟计算了不同温度下交联环氧树脂的密度和二面角扭转能,以此预测了环氧树脂的玻璃化转变温度(Tg)。结果表明,计算得到的Tg与实验值具有良好的一致性,分子动力学模拟方法可以应用于复杂聚合物体系结构与性质的研究中。     

几种不同PE和PP树脂的粘流活化能研究

测试了几种常用PE和PP树脂在一系列温度下的流变曲线,研究剪切速率对粘流活化能的影响。结果发现,相同剪切速率下,PP、LDPE、LLDPE的粘流活化能相对较高,HDPE树脂的粘流活化能相对较低,说明PP、LDPE和LLDPE对温度的敏感性较高,即升温有利于LDPE和LLDPE的加工;PP树脂的粘流活化能随剪切速率的增加而减小的幅度较大,表现出切力敏感性;剪切速率对PE树脂的粘流活化能的影响较小,在较宽的剪切速率范围内,温度对其流变性能的影响更明显。     

固体酸催化剂脱附活化能动力学模型研究及酸强度表征

基于脱附动力学,确定了脱附活化能动力学模型方程,建立了基于一套程序升温脱附(TPD)数据确定固体酸催化剂脱附活化能的动力学模拟方法。不同温度活化的催化剂TPD实验数据模拟计算结果指出,催化剂的脱附过程符合2级脱附规律;随着活化温度的提高,催化剂的脱附活化能（或酸强度）呈先增大后降低的变化趋势。比较单套数据法和多套数据法的计算结果可知,两种方法测定的脱附级数相同,各活化催化剂的脱附活化能有相似的变化趋势,单套数据法具有操作简便和结果可靠的优点。     

The effect of the glass transition temperature on the toughness of photopolymerizable (meth)acrylate networks under physiological conditions

The purpose of this study is to evaluate how the toughness of photopolymerizable (meth)acrylate networks is influenced by physiological conditions. By utilizing two ternary (meth)acrylate networks, MA-co-MMA-co-PEGDMA and 2HEMA-co-BMA-co-PEGDMA, relationships between glass transition temperature (T_g), water content and state, and toughness were studied by varying the weight ratio of the linear monomers (MA to MMA or 2HEMA to BMA). Differential scanning calorimetry and thermogravimetric analysis were performed to evaluate the thermal behavior and water content as a function of either MA or 2HEMA concentration while tensile strain-to-failure tests were performed at 37 °C to determine network toughness. Both networks exhibited a maximum in toughness in PBS in the composition corresponding to a T_g close to the testing temperature. This toughness maximum was achieved by adjusting the glass transition temperature and/or hydrophilicity through changes in chemistry. These relationships may be utilized to design tough photopolymerizable networks for use in mechanically rigorous biomedical applications.     

加勒比松Na_2S预处理硫酸盐─AQ蒸煮机理及脱木素反应活化能

对加勒比松Na2S预处理硫酸盐─AQ法蒸煮过程纤维细胞各部位木素与Na2S的反应和溶出规律进行了研究．在本试验条件下，Na2S预处理段及硫酸盐─AQ蒸煮段脱木素反应活化能分别为41．1kJ／mol及94．2kJ／mol，其相对反应速率常数分别用下列方程式计算：KR1=e12.28－4952/T;KR2=e26020-11349/T.     

Correlation between structural and dynamic mechanical transitions of regenerated silk fibroin

Dynamic mechanical analysis (DMA) was applied to investigate the correlation between dynamic mechanical behaviors of regenerated silk fibroin (RSF) and its structural transition which was characterized by near-infrared (NIR) spectroscopy. The tan δ peak split of DMA demonstrated that the apparent glass transition of amorphous RSF film (at around 177 °C) was the contribution of both uncrystallizable and crystallizable segments through homogeneous amide-amide hydrogen bonds, which were gradually separated from each other and produced disordered and β-sheet domains during ethanol treatment. Furthermore, DMA was also applied as “thermal fingerprint” to investigate water effect on the disordered domains of silk fibroin. The results showed that glass transition temperature of permanently disordered domains in crystallized RSF films was increased from 155 °C to 190 °C after thermal dehydration, and even approached 205 °C for stretched RSF films.