酚改性二甲苯甲醛树脂的热分解动力学

用热重法(TGA)分析了酚改性二甲苯甲醛(XF)树脂的热分解过程。运用Ozawa和Kissinger法进行动力学研究,得到其热分解活化能。结果表明:与普通线性酚醛树脂相比,苯酚改性XF树脂和双酚A改性XF树脂这两种改性树脂在热分解过程中的活化能都高,热分解温度也较高,热失重率降低;其中双酚A改性XF树脂的热分解活化能和热分解温度最高,热失重率最低;这说明双酚A改性XF树脂具有优异的耐热性能。     

A10改性聚甲醛热稳定性的研究

通过分子量测定、红外光谱分析(FT-IR)研究了聚甲醛(POM)的热降解机理并根据降解机理采用稳定剂A10对POM进行共混改性。运用热失重(TG)、差动扫描(DSC)、机械力学测试探讨了A10对聚甲醛改性后热稳定性能的影响。研究结果显示:热降解产生新的端基,熔融温度高于200℃时POM大分子链的断裂加快;稳定剂A10改性POM纤维在100℃老化处理250h后纤维断裂强度和断裂伸长保持率分别达95%以上和89%以上;随着稳定剂A10比例增大,热分解活化能增加,聚甲醛的热失重率逐渐降低,热分解温度升高。     

原位聚合法制备聚苯胺/多壁碳纳米管纳米复合材料及其热稳定性能

为合成树脂/聚苯胺(PANI)/多壁碳纳米管(MWCNTs)三元纳米复合电磁屏蔽材料的制备提供理论依据,在苯胺的盐酸溶液中,以过硫酸铵为氧化剂,采用原位聚合法制备PANI/MWCNTs纳米复合材料,并对PANI/MWCNTs纳米复合材料的结构、形貌以及热稳定性能进行研究。结果表明:PANI成功包覆在MWCNTs表面,且PANI和MWCNTs存在一定的相互作用;PANI在MWCNTs表面不均一性的有序生长,有效地改善了MWCNTs的分散性;PANI/MWCNTs纳米复合材料的热分解起始温度达到280℃,当温度为364℃时,热失重率为20%,说明PANI/MWCNTs纳米复合材料具有良好的热稳定性。     

甘蔗渣对聚甲基丙烯酸甲酯热降解的影响

目的分析生物质材料对塑料废弃物热降解的影响,以聚甲基丙烯酸甲酯(PMMA)为对象,探讨甘蔗渣对其热分解行为和动力学的作用。方法利用溶液共混法制备PMMA/甘蔗渣混合物,采用热失重法研究其在氮气中的热分解过程,通过最大失重速率法和Ozawa等失重法计算PMMA热分解反应的动力学参数活化能和频率因子。结果甘蔗渣使得PMMA的初期热分解温度明显降低,但是PMMA的热分解活化能和频率因子却都显著增加。最大失重速率法的计算结果表明,PMMA加入甘蔗渣后的热分解活化能增加了26.2 k J/mol,等失重法的结果显示活化能和频率因子分别为168.14 k J/mol和28.41 min-1,比纯PMMA相应地增大了72.6 k J/mol和12.52 min-1。结论甘蔗渣的加入对PMMA的热降解有显著的影响,使其热分解变得困难,因此有必要进一步探讨其他生物质对PMMA热分解的影响。     

纳米TiO_2的表面改性及MF/纳米TiO_2复合树脂的制备

采用硅烷偶联剂KH550对纳米TiO2进行表面改性,将改性纳米TiO2与三聚氰胺甲醛树脂(MF)混合,制备MF/纳米TiO2复合树脂。红外分析表明偶联剂成功接枝于纳米TiO2表面;热失重分析得出表面改性的最佳工艺为:改性剂的添加量2%,改性温度70℃,改性时间120min;透射电镜分析表明纳米TiO2的表面改性提高了其在有机溶剂中的分散性;研究TiO2添加量对MF/纳米TiO2复合树脂的粘度、固化时间、固化温度和抗菌性的影响,结果表明TiO2的添加对树脂固化时间和固化温度影响很小,但能显著提高材料的粘度和抗菌性能。     

聚氨酯弹性体纳米复合材料的制备与表征

利用几种不同的纳米粒子[包括纳米SiO2、CaCO3、八乙烯基硅倍半氧烷(即八乙烯基POSS)]对聚氨酯弹性体进行改性,制备纳米复合材料。同时,研究了不同纳米粒子对聚氨酯弹性体性能的影响。测试结果表明,聚氨酯弹性体力学性能提高;热失重(TGA)结果表明加入纳米SiO2、CaCO3、八乙烯基POSS后,复合材料的初始热分解温度分别提高了16.01℃、10.95℃、15.00℃,材料热稳定性增强;扫描电镜(SEM)观察到纳米粒子在聚氨酯基体中分散性不够理想,存在团聚现象。     

三种耐热剂对全氟聚醚橡胶材料耐热性能的影响

研究了碳纳米管(CNTs)、有机蒙脱土(OMMT)、Fe_2O_3对全氟聚醚(PFPE)橡胶力学性能、压缩永久变形、热稳定性及耐热空气老化性能的影响;采用热分解动力学模型分析了未添加耐热剂的PFPE橡胶的热降解机制。结果表明:CNTs、OMMT、Fe_2O_3均能提高PFPE橡胶基体的热稳定性,其中,CNTs/PFPE橡胶复合材料起始热失重温度及失重5%时的温度相比未添加耐热剂的PFPE橡胶分别提高了32.1℃和29.0℃;Fe_2O_3能明显稳定PFPE橡胶基体在200℃热空气条件下老化72h后的性能。在空气及N_2气氛下,随着升温速率的提高,未添加耐热剂的PFPE橡胶的热失重曲线均向高温方向移动。根据Kissinger方程,计算出PFPE橡胶基体在空气气氛下的热解活化能为135.06kJ/mol,在N_2气氛下的热解活化能为262.46kJ/mol。     

聚芳氧基磷腈的合成及热稳定性的研究

以聚二氯磷腈为主要原料,制备了3种不同的类型的聚芳氧基磷腈聚合物。通过1 H-NMR对高分子结构进行了表征。通过热失重分析研究了高分子在不同条件下的热失重行为;比较了芳环上不同类型的取代基团对高分子热稳定性的影响。结果表明,在氮气条件下3种类型的聚合物都具有较高的初始分解温度;且供芳环上有电子基团的存在有利于提高聚合物材料的热稳定性;空气条件下的热重研究表明,卤素原子的存在,会减缓高分子材料在高温阶段的热分解速率。     

层间增韧环氧树脂碳纤维单向带的热解特及动力学研究

利用差热-热重同步分析仪研究层间增韧环氧树脂碳纤维单向带的热稳定性,研究在不同升温速率条件下该复合材料的失重温度和失重规律。研究结果表明,随着升温速率的提高,层间增韧环氧树脂碳纤维单向带每个阶段的初始分解温度、反应最终温度及最大失重速率温度均向高温方向移动,热解温度范围逐渐扩大,质量损失明显增加。分别应用微分法和积分法对样品进行热解动力学相关参数计算,计算结果表明,层间增韧环氧树脂碳纤维单向带整体活化能较高,分子间碰撞激烈,热分解反应不易进行,其热稳定性较高。     

聚碳酸酯/羟基磷灰石纳米复合材料的力学性能与热性能

采用低剪切应力分散混合方法制备了不同含量的聚碳酸酯/羟基磷灰石纳米复合材料(PC/HAP),并研究了其力学性能和热行为。结果表明:采用低剪切应力法复合加入的HAP在基体中分散均匀但界面结合较弱,材料的屈服强度略有提高,而冲击性能有一定程度下降;对PC与PC/HAP复合材料在空气中热降解动力学的研究表明:在空气气氛中PC与PC/HAP均呈现二阶失重,HAP可显著提高材料的最大热失重温度及热稳定性,一阶热降解活化能由109 kJ/mol上升到186 kJ/mol,二阶热降解活化能由127 kJ/mol上升到195 kJ/mol。     

有机改性高岭土/聚氨酯纳米复合材料的制备与表征

用原位插层复合法制备了有机改性纳米高岭土/聚氨酯复合材料。研究了纳米复合材料的力学性能、耐热性能及纳米填料在复合材料中的形态。结果表明,当改性纳米高岭土质量分数为3%时,复合材料的拉伸强度为29.3 MPa、弹性模量达6.23 MPa、断裂伸长率达492%,均比纯聚氨酯弹性体增加10%以上,同时其热稳定性也有所提高;改性纳米高岭土加入量低于3%时,以剥离形态存在于聚氨酯基体中,而高于3%时,则开始出现片层形态且有团聚现象。     

半芳族共聚酰胺合成及表征

采用低温溶液法制备不同链长的均聚酰胺、交替共聚酰胺和嵌段共聚酰胺,探究反应条件对聚酰胺序列结构的影响.结果表明,红外可定性区分半芳族及脂肪族聚酰胺,二胺链节中间碳原子的13 C-NMR化学位移和峰裂分情况可用于鉴别不同碳链长度的均聚酰胺、交替共聚酰胺及嵌段共聚酰胺.交替共聚酰胺PA6T/66、PA4T/46和PA3T/...     

树脂微球敏化乳化炸药的安全性研究

介绍了乳化炸药敏化技术的安全性现状,对比分析了具有封闭微孔、表面光滑、耐压强度高的树脂微球作为敏化剂的乳化炸药的安全性,并对树脂微球敏化的乳化炸药在常温(20℃)及高温(95℃)时的摩擦感度、撞击感度、热感度、热分解温度、真空安定性及乳胶基质同树脂微球的相容性进行检测。结果表明:树脂微球提高了乳化炸药的本质安全性及产品的爆炸性能和储存稳定性;树脂微球敏化的乳化炸药机械感度低,具有良好的热安全性及化学安定性。该敏化技术对高温敏化及中低温敏化乳化炸药生产线均适用。     

聚烯烃用含硅阻燃剂的阻燃机理

采用TGA、FT-IR、SEM和TGA-FTIR联用等方法对新型含硅阻燃剂(SFR-H)的阻燃机理研究表明,SFR-H为凝聚相成炭型阻燃剂。在受热或燃烧过程中,SFR-H能迁移到材料表面降解生成高热氧稳定性的残留覆盖物,还对LLDPE基体具有催化成炭作用,能迅速在材料表面形成一层连续致密阻隔炭层,起着有效的隔热隔质作用,从而通过延缓内部材料热分解来提高材料的阻燃性能。     

磷-氮阻燃水性聚氨酯在涤丝纺上的阻燃研究

为了提高织物的阻燃性能,采用磷-氮阻燃水性聚氨酯（PU）整理涤丝纺织物,用TG、DSC和氧指数仪等研究整理后织物的热稳定性和阻燃性能,并利用扫描电镜和能谱仪对织物燃烧后的炭层进行分析.实验结果表明：与未阻燃整理织物相比,织物用PU整理后降低了起始分解温度,提高了高温下的热稳定性,分解温度范围变宽.阻燃整理织物的极限氧指...     

Modification of dispersibility of nanodiamond by grafting of polyoxyethylene and by the introduction of ionic groups onto the surface via radical trapping

To improve the dispersibility of polycrystalline nanodiamond (ND) in solvents, the grafting of polymers and introduction of ionic groups onto ND surface via radical trapping by ND surface were investigated. The grafting of polyoxyethylene (POE) onto ND surface by trapping of POE radicals formed by the thermal decomposition of POE macro azo-initiator (Azo-POE) was examined. The polymer radicals formed by the thermal decomposition of Azo-POE were successfully trapped by ND surface to give POE-grafted ND. The effect of temperature on the grafting of POE onto ND was discussed. In addition, the introduction of cationic protonated amidine groups onto ND was achieved by the trapping of radicals bearing protonated amidine groups formed by thermal decomposition of 2,2′-azobis(2-methylpropionamidine)dihydrochloride (AMPA). The anionic carboxylate groups was introduced onto ND surface by the trapping of the radicals bearing carboxyl groups formed by thermal decomposition of 4,4′-azobis(4-cyonovaleric acid) (ACVA) followed by the treatment with NaOH aqueous solution. The dispersibility of ND in water was remarkably improved by the grafting of POE, based on the steric hindrance of polymer chains and by the introduction of ionic groups, based on the ionic repulsion, onto ND surface.     

Surface Position-Resolved Thermophysical Properties for Metallic Alloys

Thermophysical properties are collective measures of a material to transport dynamical quantities of physical nature on its surface or through the bulk. As such, the exact nature of couplings between particles in a many-body assembly of building block atoms or molecules sensitively determines their values. The couplings between nearest neighbors are the product of the local elemental composition and the material phase. In this study, thermal cycling of a four-element Wood’s alloy specimen brings out cadmium-rich patches to the top surface of the specimen. An assembly of such patches leads to depth-dependent deviations of elemental composition from that of the bulk. Surface-layer atoms are driven to form a high temperature laser-produced plasma (LPP), and time-resolved spectroscopy of their emissions show the variability of elemental composition over surface positions as well as over depth from the surface. These thermal history-driven composition anomalies contribute to significant variability in the measured values of spectral emissivity and thermal diffusivity.     

Effect of DOPO units and of polydimethylsiloxane segments on the properties of epoxy resins

New flame retardant epoxy resins containing phosphorus and/or silicon atoms were prepared by the introduction into the epoxy chemical structure of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and/or of polydimethylsiloxane segments. The structure and morphology of cured epoxy resins were evaluated by Fourier transform infrared spectroscopy and scanning electron microscopy analyses, respectively. The polymers exhibited good thermal stability, having initial decomposition temperature above 310 °C. Thermogravimetric analyses and limiting oxygen index values indicated that the incorporation of DOPO units/polydimethylsiloxane segments in the polymer structure significantly enhanced flame retardancy and thermal stability of char layer at high temperature. Broadband dielectric spectroscopy measurements over a wide range of frequency and temperature revealed two subglass transitions, γ and β. The experimental data were fitted to the Havriliak–Negami and Arrhenius models, and the obtained parameters were analyzed. An α relaxation process attributed to the glass transition was observed in the high temperature and high frequency ranges. The influence of DOPO units and polydimethylsiloxane segments on the properties of the polymers was examined.     

退火气氛对镶嵌在SiO2中Ag纳米颗粒热演变影响效应的研究

将70 keV的Ag离子以5×10¹⁶ cm^-2的剂量注入到SiO₂基底中, 随后分别在400~800℃的Ar、N₂、空气气氛中退火, 详细研究了样品的表面形貌、光吸收特性、结构及成分随退火气氛及退火温度的变化规律。原子力显微镜、紫外-可见分光光度计及掠入射X射线衍射仪的测试结果显示: Ar气氛退火样品中形成的Ag纳米粒子(NPs)细小均匀, 其颗粒密度在700℃时达到最大值, 光吸收性能最佳; N₂气氛退火引发Ag纳米颗粒的团聚生长, 在样品近表面形成较大的Ag NPs, 其颗粒密度也在700℃时达到最大值; 而空气中退火后, 由于AgO的形成、分解, 样品的光吸收强度随退火温度升高持续下降。最后, 卢瑟福背散射研究结果表明, 样品的这些变化主要归因于Ag原子在不同退火气氛下随退火温度的扩散行为不同。     

Formation and Transport of Atomic Hydrogen in Hot-Filament Chemical Vapor Deposition Reactors

In this paper we focus on diamond film hot-filament chemical vapor deposition reactors where the only reactant is hydrogen so as to study the formation and transport of hydrogen atoms. Analysis of dimensionless numbers for heat and mass transfer reveals that thermal conduction and diffusion are the dominant mechanisms for gas-phase heat and mass transfer, respectively. A simplified model has been established to simulate gas-phase temperature and H concentration distributions between the filament and the substrate. Examination of the relative importance of homogeneous and heterogeneous production of H atoms indicates that filament-surface decomposition of molecular hydrogen is the dominant source of H and gas-phase reaction plays a negligible role. The filament-surface dissociation rates of H2 for various filament temperatures were calculated to match H-atom concentrations observed in the literature or derived from power consumption by filaments. Arrhenius plots of the filament-surface hydrogen dissociation rates suggest that dissociation of H2 at refractory filament surface is a catalytic process, which has a rather lower effective activation energy than homogeneous thermal dissociation. Atomic hydrogen, acting as an important heat transfer medium to heat the substrate, can freely diffuse from the filament to the substrate without recombination.