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.     

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.     

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.     

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。     

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.     

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.     

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.     

桑蚕茧的热分解动力学和反应机理的研究

本文用热重分析法(TGA)研究了桑蚕茧的热分解动力学和反应机理。根据四个不同升温速率的热重分析谱图,求得热分解百分数为5、10和15时的热分解活化能分别为410.8,376.7和324.0 kJ/mol.又根据热分解的气体产物和固体残留物的红外光谱图,推出了热分解反应的机理。     

以多羧酸为桥的锌配合物的合成和热分解动力学研究

在水-甲醇体系中,Zn(C2H3O2)2.2H2O与吡唑、邻苯二甲酸氢钾水热反应,形成以邻苯二甲酸根桥联的在xy平面一维无限的锯齿形链状锌的配位聚合物[Zn(μ2-C6H4(COO)2)(pz)2],用元素分析,红外光谱等进行了表征,并用X-ray测定了配合物的晶体结构.此外,还对配合物进行了非等温热分解动力学研究.研究表明:此配合物的热分解反应是分两步进行的.通过计算,该配合物热分解的第一步反应的可能机理为化学反应,第二步反应的可能机理为成核与生长,n=1/4,其动力学方程分别为:dα/dT=A/βe-E/RT(1-α)2和dα/dT=A/βe-E/RT1/4(1-α)[-Ln(1-α)]-3.热分解反应的表观活化能分别是177.95和303.8 kJ/mol;指前因子InA分别是41.87和53.74 s-1.     

蓖麻油基水性聚氨酯的合成及性能

采用蓖麻油(C.O.)、甲苯二异氰酸酯(TDI)和二羟甲基丙酸(DMPA)反应合成了水性聚氨酯(WPU)分散体,研究了n(-NCO)/n(-OH)、DMPA含量对聚氨酯乳液及涂膜性能的影响.实验表明:当n(-NCO)n(-OH)为2.2:1,DMPA添加量为7.0%,反应温度为70℃,乳化温度为30℃时合成的水性聚氨酯涂料具有优良的成膜性,较高的硬度、良好的柔韧性和较好的疏水性.     

蓖麻油基水性聚氨酯的合成及性能

采用蓖麻油（C．O．）、甲苯二异氰酸酯（TDI）和二羟甲基丙酸（DMPA）反应合成了水性聚氨酯（WPU）分散体,研究了n（-NCO）／n（-OH）、DMPA含量对聚氨酯乳液及涂膜性能的影响．实验表明：当n（一NCO）／n（0H）为2．2：1,DMPA添加量为7．0％,反应温度为70℃,乳化温度为30℃时合成的水性聚氨酯涂料具有优良的成膜性、较高的硬度、良好的柔韧性和较好的疏水性．     

利用煤泥制备蓄热陶瓷及抗热震性能

以煤泥为主要原料,利用无压烧结工艺,制备了用于太阳能热利用的蓄热陶瓷。研究了烧成温度对样品吸水率、气孔率、体积密度、抗折强度和抗热震性能的影响。结果表明:经1 260℃烧成的A4、A5配方样品的抗折强度分别为68.65 MPa和68.89 MPa,吸水率为0.22%和0.23%,体积密度为2.316g/cm3和2.319g/cm3,抗热震循环(500℃~室温,空气中冷却)30次无裂纹。XRD和SEM分析表明,样品的主晶相为针棒状、短柱状的莫来石和颗粒状的石英。样品的抗热震性机理研究表明,莫来石、石英、玻璃相热膨胀系数不匹配以及低膨胀系数的锂瓷石的加入,皆有利于提高样品的抗热震性能。     

Synthesis and characterization of polyurethane

Polyurethane was synthesized by the copolymerization with isocyanate and diols. The structure and properties of the copolymers were characterized by infrared spectrometer (IR), differential scanning calorimetry (DSC) and thermogravimetry (TG). The rabbit blood samples was dripped on the polyurethane, which was prepared by drying and die, and the contact angle was measured by contact angle measurement, then infiltration phenomenon was observed by electron microscopy. The results showed that the contact angle of blood samples and polyurethane was decreased with increasing time, and the platelets on the polyurethane would gradually increase and more rules. Thus the polyurethane coating had good hydrophilic property and anticoagulant activity.     

电化学沉积法制备泡沫铁及其性能研究

以导电聚氨酯泡沫为基体,采用电沉积/还原处理方法制备了多孔泡沫铁.研究了工艺条件(电解液质量浓度、pH值、抗氧化剂、起始表观电流密度)对电沉积泡沫铁的电流效率和质量的影响,优化了工艺参数,用热重与差热分析仪测量了聚氨酯泡沫基体的热分解温度,采用显微硬度计和微机控制电子万能试验机测定了泡沫铁的显微硬度和抗压强度.结果表明,起始表观电流密度为4~6 A/dm2,pH=2~3时,电沉积效率较高,可得到质量分布均匀、显微硬度高的泡沫铁;800℃下通H2还原和热处理1 h所获得产品的抗压强度和显微硬度较为理想.