Properties of water blown rigid polyurethane foams with different functionality

Water blown rigid polyurethane foams with different functionality were prepared. The physical properties of rigid foams were measured with rotational viscometer （NDJ-1 ）, universal testing machine （Instron3365）, scanning electron microscope （SEM） and differential scanning calorimeter （DSC）. The results show that the viscosity of polyether polyol increases exponentially from 62 mPa s to 6 000 mPa s with the increase of functionality from 2 to 5.6, respectively. The overall density of foam increases slightly from 31.7 kg/m^3 to 37.4 kg/m^3 with increasing functionality while core density exhibited little difference. Compressive strength of foam shows the similar behavior with density except for 2-functional sample. At the same time, dimensional stability becomes better with increasing functionality except for 5.6-functional foam that has worse stability than 4.8-functional foam. From the SEM results, the functionality is not an important factor in determining distribution of cell size of foam. According to the results of thermal analysis, the glass transition temperature （T） shifts to a higher temperature from 128.9 ℃ to 166.3 ℃ for the 2 to 5.6 functional foam, respectively.     

聚氨酯泡沫保温材料的制备及性能初探

通过对发泡剂和国产聚醚的筛选,研制一种硬质聚氨酯保温材料,其泡沫的主要性能指标为:平均芯密度41.8 kg/m3,10%压缩强度158.4 kPa,导热系数0.014 W/(m·K).结果表明,以正戊烷为发泡剂的硬质聚氨酯泡沫具有泡孔均匀、规整及导热系数低等性能特点.     

AlF3.3H2O非等温热分解动力学

采用ＴＧ－ＤＴＧ法确定了三水氟化铝的热分解过程分三步进行,求得了第一步脱水反应的表现活化能（Ｅ）和指前因子（Ａ）分别为４１．９ｋＪ／ｍｏｌ和１０＾２．４９Ｓ＾－１;第二步脱水反应的Ｅ为４７．５ＫＪ／ｍｏｌ,其非等温动力学方程为－ｌｎ（１＿ａ）＝Ａ．ｅｘｐ（－Ｅ／ＲＴ）．ｔ;在３８０℃以上,ＡｌＦ３发生水解反应,其Ｅ和非等温动力学方程汾别是８０．４ＫＪ／ｍｏｌ和「－ｌｎ（１－ａ」２／３＝Ａ．ｅｘｐ（     

Oil spill sorption using raw and acetylated sugarcane bagasse

In the recent decades oil spills in the aquatic environments are one of the major sources of environmental pollutions, which are steadily growing with the increase in oil consumption. Adsorption is a rapid and cost effective process to minimize the environmental impacts of oil spills and cleanup these pollutants. In this work, the crude oil sorption capacity was examined with raw sugarcane bagasse and acetylated sugarcane bagasse. Results show that the acetylated bagasse was significantly more oleophilic than the raw bagasse and acetylation reaction can increase bagasse oil sorption ability by about 90%. The maximum sorption capacities of acetylated bagasse were obtained about 11.3 g and 9.1 g in dry system(crude oil sorption) and oil layer sorption, respectively. The physicochemical characteristics of the sorbents such as composition, water solubility, moisture content and density were measured according to ASTM standard methods. Also Fourier transform infrared spectroscopy(FTIR) of raw and acetylated bagasse was performed to investigate the effect of acetylation on sugarcane bagasse structure.     

蔗渣纤维素的自由基清除活性研究

研究了蔗渣纤维素对二苯代苦味酰自由基(DPPH)和2-连氮-双-(3-乙基苯并噻唑啉-6-磺酸)(ABTS)自由基的清除性能.结果表明,当反应时间为30 min时,蔗渣纤维素清除DPPH和ABTS自由基的IC50值分别为23.8 mg/L和1.5 mg/L;蔗渣纤维素清除DPPH的平衡时间为220 min,清除ABTS自由基的平衡时间为60 min.可见,蔗渣纤维表现出了很好的自由基清除活性,将蔗渣纤维素开发成食品或者食品添加剂,可充分发挥其抗氧化作用.     

(CeO2,MgO)掺杂ZrO2溶胶热分解动力学

利用德国耐驰STA449C型热分析仪结合Kissinger法求解了Zr(OH)4·x(Ce(OH)4)·y(Mg(OH)2)体系的热分解动力学参数.结果显示,Zr(OH)4·x(Ce(OH)4)·y(Mg(OH)2)体系的热分解活化能为60.9 kJ/mol,反应级数2.28;晶态转变活化能为297.6 kJ/mol,相变指数1.6.     

聚氧丙烯醚的非等温热分解动力学及寿命

利用热重(TG)分析技术对聚氧丙烯醚的热失重行为进行了研究.采用非等温TG-DTG技术，在5.0、10.0、15.0和20.0 K/min线性升温速率和空气气氛条件下，考察了聚氧丙烯醚的非等温热分解机理及反应动力学.运用Freeman-Carroll、Kissinger、Ozawa、Coats-Redfern和Achar等方法对非等温动力学数据进行分析，确定了聚氧丙烯醚热分解反应的机理函数为Mampel Power法则(m=1)，对应机理为幂函数法则，其表观活化能为62.5 kJ/mol，指前因子为106.17 s-1.同时采用等温TG技术得到失重10%和15%为寿终指标的寿命方程.     

菱铁矿热分解动力学研究

菱铁矿具有热分解特性,在一定温度与气氛条件下,经焙烧后放出CO2气体,并生成强磁性的磁铁矿,利于弱磁选富集.用TG和DTG(热重法和微商热重法)研究了大西沟菱铁矿的热分解过程,判定了发生热分解反应的温度范围,分析了热分解反应的动力学行为,采用微分法计算了大西沟菱铁矿的热分解动力学参数,并判定热分解过程所符合的动力学模型,用多种积分方法和非等温线性拟合法对计算结果进行了验证.结果表明:大西沟菱铁矿的热分解反应温度较低,在400-600℃之间.热分解过程符合F1模型.     

城市生活垃圾衍生燃料热分解特性

城市生活垃圾制备衍生燃料( RDF) 是一种能够有效地解决我国城市垃圾问题的途径之一． 采用热重－ 微商热重法( TG-DTG) 分析了城市垃圾衍生燃料热分解特性,实验发现RDF 分别在空 气和氮气条件下热分解失重曲线,都有两个明显的失重段,在低温段两种条件下的失重状况基本一 致,表明分解是主要由纤维素、半纤维素类物质挥发分分解的结果． 对RDF 试样热分解产生的气 体进行气相色谱分析,发现气态有机产物在200 ℃左右开始产生,随温度升高而增加,且在300 ℃ 时达到最大． 同时,通过对气相热分解产物进行红外光谱分析,发现RDF 中的氯元素在低温段即可 大部分以HCl 形式释放出．     

丙烯腈-丁二烯-苯乙烯共聚物热降解反应动力学

研究了丙烯腈-丁二烯-苯乙烯共聚物热分析动力学参数.采用热重差热分析法,分别测定了在氮气气氛中5、10、15、20℃/min 4种不同升温速率下的的热降解过程,得到了4条热重和差热曲线,并用Kissinger法对其热降解过程进行了动力学分析.结果表明:提高升温速率,热重曲线向高温方向移动,温度滞后越严重.初始分解温度及终止分解温度更高,温度区间也变宽.升温速率的不同对最终失重率影响不大,最终失重率都在90%以上.随着升温速率的增加,差热曲线峰变高且峰顶温度向高温方向移动.通过Kissinger法分析在不同升温速率下丙烯腈-丁二烯-苯乙烯共聚物热降解反应的热重差热数据得出反应的活化能为160.9kJ/mol、表观指前因子为27.61、热降解反应级数为0.965 4等动力学参数.     

Thermal properties of open-celled aluminum foams prepared by two infiltration casting methods

Contrastive research was carried out to study the thermal properties of open-celled aluminum foams prepared by counter-gravity infiltration casting system and the traditional process respectively.The experimental results show that the thermal conductivity coefficients of aluminum foams prepared by two different infiltration methods have similar increasing trend with the increase of particle size; along with the reducing porosity,the thermal conductivity coefficients will be enhanced oppositely.However,with the same particle size,the open-celled aluminum foam prepared by the former method has a higher thermal conductivity coefficient obviously.It is largely because that the sample prepared by counter-gravity infiltration casting has a lower void content and better dense crystallization of metal-matrix after the constant pressure process.     

The Thermal Decomposition Kinetics of Polysiloxane/Polymethylacrylate IPNs Materials

1Introduction Recently,anincreasingattentionhasbeenpaidtopolysiloxanebecausepolysiloxaneisthermallyresistantpolymerinhightemperaturewiththermalenduranceinoxidativeatmosphereupto300℃andmoreininertat mosphere.Thermoanalyticaltechniques,suchasthermo gravimetric(TG),differentialthermolgravimetric(DTG),anddifferentialscanningcalorimetry(DSC)havewidelybeenusedtocharacterizepolymericmaterials.Qingzeng Zhu[1]investigatedthethermaldecompositionofsilazanepolymerswiththermogravimetrymethodandindicat…     

Preparation of basic magnesium carbonate and its thermal decomposition kinetics in air

The thermal decomposition process of basic magnesium carbonate was investigated. Firstly, Basic magnesium carbonate was prepared from magnesite, and the characteristics of the product were detected by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Subsequently, the thermal decomposition process of basic magnesium carbonate in air was studied by thermogravimetry-differential thermogravimetry (TG-DTG). The results of XRD confirm that the chemical composition of basic magnesium carbonate is 4MgCO₃·Mg(OH)₂·4H₂O. And the SEM images show that the sample is in sheet structure, with a diameter of 0.1–1 μm. The TG-DTG results demonstrate that there are two steps in the thermal decomposition process of basic magnesium carbonate. The apparent activation energies (E) were calculated by Flynn-Wall-Ozawa method. It is obtained from Coats-Redfern’s equation and Malek method that the mechanism functions of the two decomposition stages are D3 and A1.5, respectively. And then, the kinetic equations of the two steps were deduced as well.     

火电厂燃料配给模型及其分解方法

从分析火电厂燃料管理的整个过程入手,论述了火电厂燃料配给模型的建立和改进过程。建立了燃料配给模型,并根据实际情况推导出了分解方法,给出了原问题的主导问题的概念及一般形式。最后给出了一个燃料配给应用实例,验证了该模型的实效性,同时分析了该模型的应用前景。     

Thermal decomposition analysis of coal-waste sludge and coal-sunflower seed husk blends

The thermal decomposition analysis of coal-pharmaceutical waste sludge,coal-sewage waste sludge blends and coal-sunflower seed husk blends are studied by TG dynamic runs at the heating rate of 20 ℃/min within the temperature range of 25 ℃-900 ℃.The effect of different kinetic models on the determination of kinetic parameters of thermal decomposition has been investigated.Results show that for coal-pharmaceutical sludge blend,coal-sewage sludge blend and coal-sunflower seed husk blend the optimal model functions are the three-dimensional diffusion reaction,2-dimensional and 3-diemensional nucleation and growth reactions,respectively.The Arrhenius kinetic parameters of the pre-exponential factor and activation energy of blends,as well waste sludge and sunflower seed husk only are proposed.     

航天器刚性基板太阳电池阵在轨热分析

针对周期性热交变环境引起的航天器上刚性太阳电池阵温度变化对其性能和可靠性有着较大影响的问题.以4块电池板组成的太阳电池阵作为研究对象,将其内部传热过程看成无内热源三维各向异性的非稳态导热问题,全面考虑光电转换效率、布片效率和外热流等各种影响因素,进行刚性太阳电池阵在轨热分析.首先进行网格划分,计算节点为5 060个,然后运用有限差分法,考虑节点的不同位置特点,建立全隐式离散方程,最后采用AD I算法求解离散方程,得到太阳电池阵周期温度变化及各方向上温度分布规律,并与太阳电池阵的遥测数据进行比对,验证了热分析的正确性.该研究为太阳电池阵可靠设计提供参考.     

刚性路面结构参数反演弯沉盆衍生指标法综合分析

为解决刚性路面结构参数反演方法的适用性问题,综合分析刚性路面结构参数反演中3类代表性的弯沉盆衍生指标法.在系统梳理弯沉盆面积指数法、惰性点法、弯沉盆重心距离法的模型体系的基础上,采用理论数值分析的方法,定量分析3类衍生指标的规律特性,并从工程适用的简单、易操作性出发,提出惰性点法的计算图表和弯沉盆面积指数法及重心距离法的回归公式.以典型的刚性道面结构形式为例,对比分析3类弯沉盆衍生指标法的参数反演结果的准确性和鲁棒性,检验所提出模型或图表的有效性.计算结果表明:提出的计算图表或公式大幅简化了参数反演中衍生指标的计算,3种衍生指标法的参数反演结果存在明显差异,弯沉盆重心距离法充分利用各测点的信息并以拟合误差最小化为原则,显著提高参数反演的精确性和鲁棒性.     

Synthesis,characterization of monodispersed MgO microspheres and thermal decomposition kinetics of its precusor

Monodispersed MgO microspheres were successfully synthesized by a simple solvothermal method using PEG-400 as solvent. The samples were characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The results reveal that the precusor was monoclinic Mg5（CO3）4（OH）2·4H2O and composed of nanosheets with the thickness of about 250 nm. By calcining the precusor at 500 °C for 5 min, cubic MgO with similar morphology was obtained. According to the SEM images, it is found that the volume ratio of PEG-400 to deionized water is considered as a crucial factor in the evolution of the morphology. Based on the SEM images obtained under different experimental conditions, a possible growth mechanism which involves self-assembly process was proposed. The thermal decomposition process of MgO precusor was studied by thermogravimetry-differential thermogravimetry（TG-DTG） at different heating rates in air. Thermal analysis kinetics results show that the most probale mechanism models of MgO precusor are An and D3, respectively. In addition, isothermal prediction was studied to quantitatively characterize the thermal decomposition process.     

Study on kinetics of thermal decomposition of low LOI goethetic hematite iron ore

In the present study, the kinetics of thermal decomposition of hydrated minerals associated in natural hematite iron ores has been investigated in a fixed bed system using isothermal methods of kinetic analysis. Hydrated minerals in these hematite iron ores are kaolinite, gibbsite and goethite, which contribute to the loss on ignition(LOI) during thermal decomposition. Experiments in fixed bed have been carried out at variable bed depth(16, 32, 48 and 64 mm),temperature(400-1200 ℃) and residence time(30,45, 60 and 75 min) for iron ore samples. It is observed that beyond a certain critical bed depth(16 mm), 100% removal of LOI is not found possible even at higher temperature and higher residence time. Most of the solid-state reactions of isothermal kinetic analysis have been used to analyze the reaction mechanism. The raw data are modified to yield fraction reacted "α" versus time and used for developing various forms of "α" functions.f(α) is the inverse of first derivative of g(α) with respect to α. The study demonstrates that decomposition of hydrated mineral in hematite follows the chemical kinetics.The estimated activation energy values in all the experimental situations are found to high, of the order of 60 kJ/mol, reinstating that the reactions are indeed controlled by moving phase boundary and random nucleation.     

Thermal decomposition behaviour of polyacrylamidomethyltrimethyl ammonium chloride in red mud separation process

In order to provide references for selecting highly efficient red mud flocculants, the behaviour of polyacrylamidomethyltrimethyl ammonium chloride （PATAC） in red mud separation process was investigated. PATAC was employed as a flocculant for red mud separation from the caustic aluminate liquor at 95 ℃. The used red mud was generated from Chinese diaspore bauxite in Bayer process of alumina production. And the changes of PATAC before or after being treated in caustic solution at 95 ℃ were studied by thermogravimetry （TG） and Fourier transform infrared （FTIR） spectral analysis. The results show that PATAC fails in effectively focculating red mud and PATAC is readily converted to a quaternary ammonium hydroxide （PATAH） in caustic solution. PATAH can be decomposed to a new polymer （HPATAH） even at 95 ℃. Furthermore, there is an intramolecular hydrogen bond formed in the HPATAH polymer chain with two functional groups of--CH2--OH and --CONH2. Therefore, the poor flocculation property of PATAC for red mud separation can be attributed to the thermal decomposition of PATAC in the caustic red mud slurry at 95 ℃ and the formation of intramolecular hydrogen bond in the polymer chain of HPATAH during the thermal decomposition, which causes the absorbable functional groups of PATAC to decrease greatly.