PBAMO的热分解反应机理

采用无模型法对聚3,3-双叠氮甲基环氧丁烷(PBAMO)的热分解反应动力学进行了计算,并用热重-红外-质谱(TG-IR-MS)联用技术研究了其热分解反应产物。PBAMO表现出了独特的热分解过程,TG曲线中在210℃~270℃叠氮基团的分解失重之后没有第二个明显的失重台阶;PBAMO第一阶段的热分解活化能为150 kJ/mol,当分解率大于0.4时,活化能降为负值。TG-IR-MS结果表明,在叠氮基团分解时释放的热量加速了剩余氮原子的氧化还原过程,主要产物形式为NO,主链中的氧原子被消耗掉,从而导致了碳链骨架的大量残留。     

PBAMO-GAP-PBAMO三嵌段共聚物的制备及表征EI北大核心CSCD

以三氟化硼四氢呋喃络合物(BF_3·THF)为催化剂,用端羟基聚环氧氯丙烷(PECH)大分子引发3,3-双氯甲基氧杂环丁烷(BCMO)开环聚合得到三嵌段共聚醚,再经过叠氮化反应得到聚3,3-双叠氮甲基氧杂环丁烷-聚叠氮缩水甘油醚-聚3,3-双叠氮甲基氧杂环丁烷(PBAMO-GAP-PBAMO)三嵌段共聚物。采用红外光谱、核磁共振碳谱、凝胶渗透色谱和差示扫描量热分析等对产物的结构和性能进行了测试和表征。对聚合反应和叠氮化反应的条件进行了研究,结果表明,聚合反应时间为8 h、PECH与BCMO的质量比为1∶2,并以N,N-二甲基乙酰胺作叠氮化反应溶剂时,得到的聚合产物相对分子质量可达6242,叠氮取代率达98.2%;产物的玻璃化转变温度为-46.1℃,热分解温度为235. 1℃。     

BAMO-AMMO三嵌段共聚物的间接法合成及表征

以3,3′-双溴甲基环氧丁烷(BBMO)和3-溴甲基-3’-甲基环氧丁烷(BrMMO)为单体,通过活性顺序聚合法合成了BBMO-BrMMO三嵌段共聚物,并采用相转移催化法实现了3,3′-双叠氮甲基环氧丁烷-3-叠氮甲基-3′-甲基环氧丁烷(BAMO-AMMO)三嵌段共聚物的间接法合成。探讨了溶剂的选择及叠氮化反应时间的影响:选用极性和溶度参数接近的异亚丙基丙酮为溶剂,24 h后叠氮化率为99.97%。通过核磁共振(13C-NMR)和凝胶渗透色谱(GPC)对所得产物进行了表征,结果表明,共聚物组成接近于1∶1,分子量7053,分子量分布1.47。     

交替嵌段型BAMO-AMMO热塑性弹性体的性能

以3,3′-双叠氮甲基环氧丁烷-3-叠氮甲基-3′-甲基环氧丁烷(BAMO-AMMO)三嵌段共聚物为预聚物,甲苯二异氰酸酯(TDI)和1,4-丁二醇(BDO)为扩链剂,采用溶液法合成了交替嵌段型BAMO-AMMO热塑性弹性体,并进行了结构和相关性能的表征。结果表明,弹性体中叠氮基团与氨基甲酸酯形成氢键作用,氢键键合氨基与自由氨基的摩尔比为3.56∶1。弹性体的数均相对分子质量为30432;随着扩链剂含量(w(TDI+BDO))的增加,Tg逐渐升高;TDI和BDO的质量分数为20%时,Tg为-42.14℃,拉伸强度可达9.21 MPa,断裂伸长率为375%,蠕变恢复时间为200s,其最小形变值为0.1%,具有良好的抗蠕变性和蠕变恢复能力。     

聚叠氮缩水甘油醚/聚乙二醇双软段含能聚氨酯弹性体的性能

为改善聚叠氮缩水甘油醚(GAP)的性能,以三羟甲基丙烷(TMP)为交联剂,异佛尔酮二异氰酸酯(IPDI)为固化剂,选用聚乙二醇(PEG)制备出GAP/PEG/TMP/IPDI双软段含能聚氨酯弹性体,采用红外光谱(FT-IR)、差示扫描量热(DSC)等手段进行了表征。实验结果表明,弹性体中引入聚乙二醇(PEG),拉伸强度提高168%,延伸率提高77%,所选PEG软段分子量较小,弹性体中只出现了GAP软段的Tg。随交联剂含量的增大,GAP软段的Tg由-36.85℃上升到-34.81℃,继而又下降到-40.31℃,弹性体的热分解分两段进行,初始分解温度为183℃。     

PBAMO-GAP-PBAMO三嵌段共聚物的制备及表征

以三氟化硼四氢呋喃络合物(BF_3·THF)为催化剂,用端羟基聚环氧氯丙烷(PECH)大分子引发3,3-双氯甲基氧杂环丁烷(BCMO)开环聚合得到三嵌段共聚醚,再经过叠氮化反应得到聚3,3-双叠氮甲基氧杂环丁烷-聚叠氮缩水甘油醚-聚3,3-双叠氮甲基氧杂环丁烷(PBAMO-GAP-PBAMO)三嵌段共聚物。采用红外光谱、核磁共振碳谱、凝胶渗透色谱和差示扫描量热分析等对产物的结构和性能进行了测试和表征。对聚合反应和叠氮化反应的条件进行了研究,结果表明,聚合反应时间为8 h、PECH与BCMO的质量比为1∶2,并以N,N-二甲基乙酰胺作叠氮化反应溶剂时,得到的聚合产物相对分子质量可达6242,叠氮取代率达98.2%;产物的玻璃化转变温度为-46.1℃,热分解温度为235. 1℃。     

含ADN或TKX-50的叠氮高能固体推进剂能量特性分析

利用最小自由能法研究了叠氮类［如聚叠氮缩水甘油醚(GAP)、3,3’-双叠氮甲基氧丁烷-四氢呋喃共聚醚(PBT)、聚3-甲基-3-叠氮甲基环氧丁烷(PAMMO）］高能固体推进剂的能量特性参数,重点研究了二硝酰胺铵(ADN)和5,5’-联四唑-1,1’-二氧二羟铵(TKX-50)在不同固体填料配比下对推进剂能量特性的影响规律。结果表明:在高固含量的叠氮推进剂中,用ADN取代高氯酸铵(AP),由于燃烧产物平均相对分子量降低,推进剂比冲提高;叠氮类推进剂能量由大到小为GAP、PBT、PAMMO;TKX-50用于叠氮类高能固体推进剂中,由于体系内的负氧平衡问题,TKX-50与奥克托今(HMX)、AP或ADN间存在能量的最优配比。用TKX-50完全取代HMX时,ADN/TKX-50/Al推进剂的理论比冲为2 790.6 N?s/kg,比ADN/HMX/Al推进剂的理论比冲增加了30.7 N?s/kg。     

GAP/PET聚氨酯粘合剂胶片的制备及其性能研究

为改善聚叠氮缩水甘油醚(GAP)推进剂的力学性能,选用链段柔软的环氧乙烷/四氢呋喃共聚醚(PET),采用三羟甲基丙烷(TMP)为交联剂,异佛尔酮二异氰酸酯(IPDI)为固化剂,与GAP制备聚氨酯粘合剂胶片.实验结果表明:在R为1.9,GAP:PET:TMP羟基比为1:1:3条件下,粘合剂胶片拉伸强度为3.29MPa,延伸率为625.07%.粘合剂胶片经硝化甘油/一缩二乙二醇二硝酸酯增塑后,其力学性能变化较大.在增塑比为0.5～2.1范围内,增塑胶片的Tg符合方程:Y=-77.60233+36.45135exp(-x/0.055019).     

BAMO/GAP无规共聚物的合成与表征

采用1,4-丁二醇-三氟化硼乙醚(BDO/BTFE)体系通过阳离子开环聚合合成了3,3-二溴甲基氧丁环/环氧氯丙烷(BBMO/ECH)无规共聚物,再通过叠氮化反应,得到3,3-二叠氮甲基氧丁环/叠氮缩水甘油醚(BAMO/GAP)无规共聚物。通过反应条件优化,确定了阳离子开环反应的最佳条件是n(BTFE)∶n(BDO)=1∶2,反应温度15℃。通过红外光谱(FT-IR),核磁共振(13C-NMR),凝胶渗透色谱(GPC)和差示扫描量热(DSC)对其进行了表征。BAMO/GAP无规共聚物的-Mn=1750,分子量分布1.12,齐聚物含量约为22%;DSC结果证明,其玻璃化转变为-57.68℃,无结晶性。     

PMMA-b-PHEA嵌段共聚物的制备和表征

采用分步法合成了两嵌段共聚物聚甲基丙烯酸甲酯-b-聚丙烯酸-2-羟乙酯(PMMA-b-PHEA):首先采用AIBN作为引发剂,FeCl3/PPh3作为催化体系,通过MMA的反向原子转移自由基聚合(RA-TRP),得到含端基Cl的M-n为17128聚合物PMMA-Cl;然后以PMMA-Cl为大分子引发剂,FeCl2/PPh3为催化体系,引发丙烯酸-2-羟乙酯(HEA)的原子转移自由基聚合(ATRP),得到的产物PMMA-b-PHEA分子量分布达到1.32,凝胶渗透色谱(GPC)、红外光谱(FTIR)、核磁共振(1HNMR)、差示扫描量热仪(DSC)和热重分析仪(TGA)对产物结构进行了表征,证实了嵌段共聚物PMMA-b-PHEA的生成。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。