BMI用量对改性苯并噁嗪树脂性能的影响

采用BMI树脂对苯并噁嗪进行改性,采用DSC法研究了BMI树脂用量对苯并噁嗪体系反应特性的影响,制备了改性苯并噁嗪树脂固化物,对其耐热性进行了表征.结果表明,改性苯并噁嗪树脂体系,只有一个反应的放热峰,峰顶温度为232℃,且放热峰的峰顶温度与BMI的用量无关.改性苯并噁嗪体系的热稳定性与苯并噁嗪体系相比较为复杂,BMI...     

新型酚醛树脂--苯并噁嗪树脂的研究进展

摘要：综合论述了新型酚醛树脂——苯并噁嗪树脂的研究进展,主要侧重于从苯并噁嗪单体的合成及表征、苯并噁嗪聚合反应动力学与聚合反应机理、苯并噁嗪分子结构与性能的关系以及苯并噁嗪树脂的应用开发等方面进行论述。     

RTM改性苯并噁嗪树脂及复合材料性能研究

研究了RTM改性苯并噁嗪树脂及复合材料性能.用DMA研究RTM改性苯并噁嗪树脂体系的储能模量、损耗模量和玻璃化转变温度;用流变仪研究黏度特性;用TGA和TGA微分曲线研究热分解性能;并研究了RTM改性苯并噁嗪树脂及复合材料的力学性能.结果表明:RTM改性苯并噁嗪树脂体系的玻璃化转变温度是206℃;至少有400min的低黏度(η≤0.5Pa.s)时间作为工艺开放期;在氮气气氛下,RTM苯并噁嗪树脂体系热失重分两个主要阶段,在375℃时发生5％热失重,800℃残碳率是45.2％;RTM苯并噁嗪树脂基体拉伸强度72.4MPa,拉伸模量5.07GPa,弯曲强度173MPa,弯曲模量4.6GPa;碳纤维增强RTM苯并噁嗪树脂基复合材料的常规力学性能优异.     

超支化聚硼酸酯改性苯并噁嗪树脂阻燃性能研究

苯并噁嗪是一种类似酚醛树脂的开环固化型热固性树脂,具有一定的耐热性和阻燃性,但在阻燃要求高的场合使用时,需要进一步改善其阻燃性、力学性能及工艺性。而已有的阻燃改性方法较难实现在提高树脂阻燃性的同时兼顾其力学性能和工艺性。采用一种具有增韧作用的耐高温超支化聚合物—超支化聚硼酸酯(HBPB),在改善苯并噁嗪树脂力学性能和固化工艺性的基础上对其进行阻燃改性。加入2.5或5.0wt%的HBPB后,苯并噁嗪树脂的800℃(氮气)残碳率可由46.0%提高至50.9%和54.8%;阻燃性能明显提升,由UL-94V1提高到UL-94V0级,苯并噁嗪树脂的极限氧指数也由24%增加到30%和33%。HBPB改性苯并噁嗪树脂燃烧产物表面形成的致密表面结构,是树脂阻燃性提高的重要原因。     

ANPyO高温下热分解过程的分子动力学模拟

采用Reax FF力场研究了凝聚相ANPy O在不同温度(T=1500 K、2000 K、2500 K、3000 K、3500 K)的热分解,通过指数函数拟合势能演化曲线得到了平衡和诱导期以及整体反应时间和热解活化能Ea(88.65 k J·mol-1)。结果表明,晶胞中的ANPy O分子几乎完全分解时系统的势能开始显著衰减,但是在不同的温度表现出不同的反应机理。在低温(1500 K≤T≤2000 K)下ANPy O热解的初始反应为—NH_2上H转移至ortho—NO_2生成H_2O和NO分子;在高温(2500 K≤T≤3500 K)下热解的主要初始反应为C-NO_2键的断裂和C—NO_2→C—ONO重排布断裂产生NO_2和NO。有限时间步长的产物识别分析结果表明,ANPy O热解的主要产物为H_2O、N_2、NO_2、NO、CO_2、CO、OH以及HONO。氧化性中间产物NO_2、NO、OH以及HONO与NH_2、H再次反应,产生系统最稳定的产物H_2O和N2,从而使其分布显示出剧烈的波动特征。环上基团相互反应或直接脱落后主环间C-C和C-N才发生断裂,一部分分解成CO_2、CO和NO,另一部分聚集生成碳团簇。     

双酚AP基苯并噁嗪树脂等温固化动力学研究

以4,4'-(1-苯乙基)双酚(双酚AP)、正辛胺和甲醛为原料,采用溶剂法合成了一种新型双酚AP基苯并噁嗪单体,利用FT-IR和1H NMR对产物结构进行了表征,采用差式扫描量热仪(DSC)研究了苯并噁嗪单体的等温固化反应动力学.结果表明,该树脂体系的固化反应在反应前期为化学动力学控制,后期变为扩散控制占主导地位的反应,苯并噁嗪的固化过程为自催化和扩散控制.在反应后期实验数据和理论数据出现了偏差,通过将扩散因子引入到自催化模型中,改进后的自催化模型与实验数据相符.     

氢氧化铝改性苯并噁嗪及阻燃性的研究

以加入氢氧化铝(ATH)提高苯并噁嗪树脂(BOZ)的阻燃性,并对阻燃聚苯并噁嗪树脂的性能进行研究.结果表明,当氢氧化铝质量分数大于20%时,聚苯并噁嗪树脂的阻燃性可以达到UL-94V0级.差示扫描量热(DSC)和动态机械分析(DMA)测试显示氢氧化铝的加入,使苯并噁嗪树脂开环固化反应放热热焓和峰值温度均有降低,使聚苯并...     

聚乙烯热解制备二氧化硅表面碳涂层的机理研究

利用反应分子动力学ReaxFF方法模拟了聚乙烯热解碳沉积二氧化硅基底的微观过程，通过分析沉积过程中碳结构、体系产物数目及碳碳径向分布函数的变化来揭示聚乙烯碳化机理。结果表明：碳结构的形成主要是远离基底芳香环的沉积成片生长和靠近基底的小分子碳的渗入、析出，连接在沉积的碳结构上。其中远离基底的聚乙烯热解有两个方向，一是直接热解为小分子的碳氢化合物(C₂H₄、C₃H₆、C₄H₈等),继而小分子碳氢化合物继续反应脱氢，重组形成碳链和碳环；二是未完全断链的碳氢长链(C>5),与碳氢小分子进行反应。研究温度和保温时间对沉积的影响得知，升温可以加快反应速率，但不改变整体的反应趋势。温度为2500K,在保证碳源充足的情况下，会有更多的碳形成稳定的碳环结构，持续生长。从ReaxFF动力学角度研究高分子聚合物制备碳材料的机理，可以为相关实验研究提供理论支持。     

环三磷腈基苯并噁嗪的合成及热性能研究

为提高苯并噁嗪树脂的耐高温性能,以水杨醛、对氨基苯酚、环三磷腈衍生物为原料通过多步反应制备了环三磷腈基苯并噁嗪单体(CPBOZ),通过核磁共振(1 H-NMR、31 P-NMR)和傅里叶红外光谱(FT-IR)对所合成化合物的结构进行了表征;利用FT-IR和热重分析(TGA)考察了苯并噁嗪的固化行为及树脂的热稳定性。结果显示:环三磷腈结构的引入,显著提高了相应苯并噁嗪树脂的耐热性,其固化后失重率为5%和失重率为10%时的温度分别达到了365℃和397℃;在900℃(N2)时的失重率达到了48.2%,比普通苯并噁嗪树脂提高了约65.64%。     

吸热型碳氢燃料正辛烷的热分解机理

利用反应分子动力学方法,对正辛烷在不同温度条件下的热解特性进行研究,并用密度泛函理论(DFT)对结果进行验证比较。结果表明:正辛烷初始反应为八种热解均裂反应,分别为四种碳碳键断裂和四种碳氢键断裂,且碳碳键比碳氢键更容易发生断裂,分子端部的化学键断裂比较困难。讨论了温度对热解产物的影响,热解的主要产物是H_2、CH_4、CH_2=CH_2,其他产物为CH_3-CH_3。H_2有两种形成机理,分别是自由基攻击反应和自由基间结合反应。CH_4有两种形成机理,与H_2的相似。CH_2=CH_2的形成机理为大分子自由基β键断裂反应。本工作从分子尺度研究了正辛烷的热解机理,为其他吸热型碳氢燃料的热裂解特性研究提供了参考。     

苯乙烯／丁二烯的阴离子反应挤出聚合机理

在双螺杆挤出机中以有机锂为引发剂,采用丁二烯(B)与苯乙烯(S)混合单体,本体一步合成了苯乙烯/丁二烯(S/B)共聚物。采用差示-紫外联用的双检测GPC对共聚物的组成分布进行了研究,结果表明,相比高分子量的共聚物,低分子量共聚物的组成分布比较均一。采用小角激光光散射仪(MALLS)联用GPC对降解后样品进行测试表明,共聚物分子链是由一个聚苯乙烯长嵌段连接着大量的(S-B)小嵌段构成的。     

Competition of Reactive red 4, Reactive orange 16 and Basic blue 3 during biosorption of Reactive blue 4 by polysulfone-immobilized Corynebacterium glutamicum

Competition of Reactive red 4 (RR4), Reactive orange 16 (RO16) and Basic blue 3 (BB3) during biosorption of Reactive blue 4 (RB4) by polysulfone-immobilized protonated Corynebacterium glutamicum (PIPC) was investigated in batch and column mode of operations. Through potentiometric titrations, and with the aid of proton-binding model, carboxyl, phosphonate and amine were identified as functional groups of PIPC, with apparent pK(a) values of 3.47+/-0.05, 7.08+/-0.07 and 9.90+/-0.05 mmol/g, respectively. Since reactive dyes release dye anions (ROSO(3)(-)) in solutions, the positively charged amine groups were responsible for biosorption. PIPC favored biosorption at pH 3 when RB4 was studied/used as single-solute; while the presence of RR4 and RO16 severely affected the RB4 biosorption. When present as a single-solute, PIPC recorded 184.5mg RB4/g; while PIPC exhibited 126.9, 120.9 and 169.6 mg RB4/g in the presence of RR4, RO16 and BB3, respectively. In general, the accessibility of amine group depends on the molecular size, number of sulfonate groups and reactivity of each reactive dye. Single and multicomponent Freundlich equations successfully described the biosorption isotherms. With 0.1M NaOH, it is possible to reuse PIPC for RB4 biosorption in 10 repeated cycles. Column experiments in an up-flow packed column coincided with batch results, that is PIPC showed strong preference towards highly reactive and relatively small RB4 anions; however, the presence of competing dyes hinder the RB4 column biosorption performance.     

Reactive sintering of stainless steel

Abstract

Pressed and sintered 316L type stainless steel compacts have been produced using an innovative process termed reactothermitic sintering RTS. This technique has the ability to produce full density, near net shape parts using conventional compaction and mesh belt furnace practices. It utilises chemical reactions at the surface of the stainless steel powders in which the energy balance is matched to provide transient liquid films that can be frozen at high cooling rates to consolidate the material without slumping. Small quantities of elemental aluminium and nickel powders are added before compaction that react, during sintering, both with themselves and with oxide layers present on the bulk stainless steel powder surfaces. In addition to the naturally occurring oxides present on the surface of stainless steel powders, artificial oxide layers, deposited by sol-gel and direct thermal oxidation, have been used to aid investigations into the nature of the reactions involved. The RTS technique leads to the generation of novel microstructures in the systems described that are characterised by negligible interconnected porosity. The present paper details the experimental programme undertaken to ascertain and substantiate these phenomena together with a model of how porosity is eliminated in this system.     

Reactive sintering of zinc ferrite

The reactive sintering of zinc ferrite, i.e. firing without previously calcining, has been studied using three types of iron oxide. The conversion into ferrite as well as the simultaneous densification were investigated upon variations in morphology and impurity content. The formation reaction is shown to be accompanied by a strong increase of the median pore size. This phenomenon appears responsible for the generally smaller density of the final material as compared with single-phase sintering. It is shown that reactive sintering is inevitably accompanied by expansion, irrespective of molecular volume variations. A calcining step appears indispensable for the preparation of the highest quality of ferrites.     

反应热喷涂的发展

反应热喷涂是自蔓延高温合成同热喷涂技术相结合而发展起来的新技术，作者综述了反应热喷涂的工艺，过程，涂层结构及性能。     

Reactive sintering of manganese ferrite

The reactive sintering of manganese ferrite, i.e. the concurrence of a chemical reaction with densification during firing, has been studied using several raw materials. It was shown that the formation reaction from the raw materials is always accompanied by expansion and that such processing invariably results in a less dense end product. After calcining the powder, these phenomena did not occur. This was shown to be related to an improved initial homogeneity rather than to the degree of conversion. On the other hand, calcining increased the change of excessive grain growth, which was further influenced by the porosity, the firing temperature and the presence of impurities.     

Reactive Synthesis of Aluminide Intermetallics

Reactive synthesis of bulk and reinforced aluminides are reviewed. When processed under optimal conditions, reactively-synthesized aluminides display room-temperature mechanical properties as good as, or better than, cast aluminides. Frequently encountered defects resulting from reactive synthesis are: (i) porosity, (ii) incomplete synthesis and (iii) loss of shape due to liquid formation. Using a simple mass balance, the amount of liquid aluminide is calculated as a function of the initial temperature of the reactants. Process maps are discussed for some of the aluminides of nickel and titanium.     

Reactive plasma cleaning of metals

Reactive plasmas formed in an r.f. discharge are effective in removing contaminants and barrier layers from a variety of metals. Reactive d.c. discharges are ineffective. A mixture of argon (90–99%) with a reactive gas or a gas which will decompose to a reactive species in the discharge was used in the r.f. reactive plasmas. A soft X-ray appearance potential spectrometer was used for in situ surface analysis to evaluate the surface cleaning. Carbon-containing gases, such as those used in reactive plasma etching, left a carbon residue on the surface. Oxygen additions to the reactive plasma, such as are used in reactive etching, prevented cleaning of the metal surfaces. Reactive plasmas containing hydrochloric acid were the most effective. Reactive plasma cleaning in Ar-HCl was as effective as r.f. sputter cleaning and could be accomplished at much lower power levels. For example, reactive plasma cleaning of titanium was accomplished in 90 min using 500 V r.f. and 30 W in an Ar-5% HCl plasma. Similar r.f. sputter cleaning required 90 min at 2 kV r.f. and 600 W in Ar. It is proposed that the reactive species reacts with the surface, forming compounds which are more easily volatilized or sputtered.     

紫外光固化活性稀释剂的进展

本文介绍了近年来紫外光固化活性稀释剂的进展，以及它们的性能、特点和主要生产厂家。     

反应等离子喷涂TiN陶瓷涂层

采用气道型反应等离子喷涂技术,制备了TiN陶瓷涂层,通过XRD、SEM等手段对陶瓷涂层进行了相分析和横断面形貌分析。结果表明,陶瓷涂层主要由TiN相组成,并含有微量复杂成分的氧化物;TiN陶瓷涂层具有典型的层状组织结构,且层与层之间结合较好;显微压痕和断口显示TiN涂层的韧性较Al2O3涂层有明显提高。