有机过氧化物热动力学及热危险评价研究进展

总结了有机过氧化物、有机过氧化物与不相容物混合、有机过氧化物与稀释剂混合等条件下的热动力学及热危险参数确定方法,探讨了有机过氧化物与其他物质相容性判据以及稀释剂减敏效果判据,论述了有机过氧化物自加速分解温度的确定方法,分析了采用定量结构性能相关方法 (quantitative structureproperty relationship,QSPR)预测有机过氧化物热危险性的可行性,为有机过氧化物热分解机理研究以及安全生产、储运和使用提供了参考。     

有机过氧化物分解机理及热危害

为了预防及控制有机过氧化物的分解爆炸事故,需要对其热危害进行必要的评估。利用塞塔姆C80微量热仪对不同种类的9种有机过氧化物进行热扫描测试,并分别利用n级反应模型及自催化反应模型对扫描曲线进行拟合,准确得到了这些物质的分解热及分解机理。根据反应动力学数据,采用Semenov爆炸模型及联合国H.3-等温储存试验原理,得到了9种有机过氧化物的临界温度及自加速分解温度（SADT）。结果表明,大部分有机过氧化物分解遵循n级反应模型,反应级数在1左右,少部分有机过氧化物分解时有一定的自催化效应。所得的SADT数据与文献值符合较好,证明本文动力学模拟及SADT计算方法的科学性。     

酸、碱污染物对过氧化苯甲酸叔丁酯热危险性影响

过氧化苯甲酸叔丁酯(TBPB)对热不稳定,一旦在生产、储运过程中被H⁺或OH^－污染,可能会对其热危险性产生较大影响。采用绝热加速量热仪在“加热-等待-搜索”和“等温”模式下研究了H₂SO₄、NaOH存在下TBPB的热分解反应行为,从热分解特性参数、反应动力学参数、最大反应速率达到时间TMR、自加速分解温度SADT四个方面定量表征了H⁺、OH^－对TBPB热危险性的影响。采用“伪逆矩阵法”确定反应动力学参数,得到最不利条件下的热分解特征参数。采用Townsend算式,得到了考虑反应机理和反应物浓度的TMR推算式。基于Semenov理论,推算了0.5 L Dewar瓶和常用商业包装的SADT。结果表明:OH^-污染物使TBPB发生两次放热,第一次放热释放能量不足以维持热失控反应,但加速TBPB老化变质,从而导致第二次放热反应动力学参数升高,热危险性减弱;H⁺污染物降低TBPB反应动力学参数,加剧热危险性;TMR和SADT推算结果表明H⁺污染物降低了TMR对应的报警温度,降低了包装容器的SADT。     

热分析动力学数据处理

近年来,热分析广泛地应用在高分子、石油化工、化学材料、火炸药等各个领域。由于它具有试样用量少、快速,并能研究在观察温度范围内的物质受热变化的全过程等优点,所以已成为研究物质物理和热化学过程以及化学反应动力学的重要手段之一。化学反应动力学的研究是为了了解物质反应速度与温度的关系以及反应过程的机理,从而求出有关的动力学参数,一般我们经常采用的热分析方法为 DTA、DSC 和 TG。利用实验所获得的等温或非等     

热分析法测定含能材料自加速分解温度的研究进展

从自加速分解温度（SADT）评价含能物质的热危险性出发,分析了联合国危险物运输专家委员会推荐的几利-方法对含能材料热危险性评价的局限性,简述了与热分析法相关的测定含能材料自加速分解温度的方法,主要有加速量热仪法、TG—DTA、DSC、微量热法、动力学模拟法、绝热自点火实验法等。同时对各种方法的优缺点分别进行了分析,讨论了热分析法评价含能材料热危险性的发展趋势。     

烯烃聚合工业有机过氧化物危险性分析及对策

根据烯烃聚合工业用有机过氧化物自分解温度低,易发生反应失控引发火灾爆炸等特征,对有机过氧化物的结构、分类、化学性质、反应特性以及贮存、使用、管理等过程中的危险性进行了分析.提出了过氧化物贮存、运输、使用、报废等方面的风险消减与事故预防措施.     

沥青热缩聚过程的动力学问题

本文综述了以凝胶渗透色谱(GPC)、电子自旋共振(E.S.R)、溶剂抽提(S.E)及核磁共振氢谱(H.n.m.r)等方法研究碳化化学中沥青热缩聚的动力学问题。介绍了一些动力学的测定及计算方法,整理出反应级数、速率常数、活化能等一批参数,并讨论了热缩聚机理及动态过程中反应物与生成物的结构变化规律。     

水和弱酸对过氧化氢异丙苯热危险性的影响

为研究水和弱酸对过氧化氢异丙苯(CHP)热危险性的影响,利用C600微量热仪研究了CHP及CHP与不同含量水、不同含量弱酸、不同pH值弱酸的混合物在空气中受热分解的反应和放热特性,根据实验数据得出了相应的动力学和热力学参数,利用Semenov热爆炸模型计算出了自加速分解温度(SADT)。结果表明:少量的水和弱酸都能够使CHP的起始放热温度、最大放热温度、活化能降低;弱酸的pH值对CHP的热危险性也有影响,pH值越低,CHP的热危险性越大;计算得到CHP的SADT为84℃,通过对CHP及CHP与不同含量水、弱酸和不同pH值弱酸混合物SADT进行比较,发现少量的水和弱酸均能降低CHP的SADT,弱酸的pH值对SADT也有影响,pH值越低,CHP与弱酸混合物的SADT越小。     

聚乙烯热裂解制备聚乙烯蜡四集总动力学模型

通过对高密度聚乙烯进行釜式热裂解实验,研究高密度聚乙烯的热裂解行为,计算动力学反应参数,建立了聚乙烯热裂解的集总动力学模型,并讨论了反应温度及反应时间对模型的影响,对预测产品产率及分布起到指导性作用。     

1-丁烯热裂解自由基反应模型的建立及验证

基于自由基链式反应机理,将Materials Studio(MS)模拟和Aspen Plus模拟计算相结合研究了1-丁烯热裂解自由基反应机理,运用MS软件对1-丁烯的结构进行优化、分析,建立了初步的、可能发生的12个自由基反应网络和2个可能反应路径;对1-丁烯可能发生的热裂解自由基反应进行模拟计算,得到1-丁烯裂解自由基反应相关动力学参数如活化能(Ea)及速率常数(k)等;用Aspen模拟软件建立裂解反应器模拟实验过程,预测1-丁烯热裂解自由基反应产物分布情况。结果表明,1-丁烯热裂解自由基反应机理模型与一维热裂解工艺模型软件模拟1-丁烯热裂解的主要产物的种类一致,预测的产物分布也吻合,1-丁烯热裂解的主要目的产物是丁二烯、丙烯及少许乙烯,与已有的实验结论相符。     

基于非均相反应小尺度实验的固态有机过氧化物自加速分解温度推算

引言 有要过氧化物的分子结构中含有双氧键,具有不稳定、易分解的特性,在较低的温度下就能发生热分解,放出大量的热,加速系统升温分解,从而发生剧烈反应,甚至导致热爆炸.     

Low surface energy coatings covalently bonded on diamond-like carbon films

In the present work, a chemical treatment with perfluorinated peroxides is proposed to obtain protective layers covalently linked to a diamond-like carbon (DLC) surface. The lubricant properties of perfluorinated compounds and the stability of the chemical modification of DLC surface simultaneously cooperate in this technical approach. Each fluorinated layer is deposed on an bare DLC surface by a dip coating application technique and the covalent linkage of the fluorinated layers is obtained by the thermal decomposition of the peroxidic moieties of the perfluorinated peroxides. Reactive perfluorinated radicals are generated close to the sp² sites of the DLC surface, allowing the formation of covalent bonds. The fluorinated peroxides used in this work belong to the class of the PFPE peroxides and to the class of the perfluorodiacyl (PFDA) peroxides. The effect of the fluorinated coatings on the DLC surface is studied using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), with contact angle (CA) measurements and, in particular, the friction forces are evaluated by means of lateral force microscopy (LFM).     

Dynamically vulcanized PP/EPDM blends by multifunctional peroxides: Characterization with various analytical techniques

The characterization of peroxide‐cured PP/EPDM TPVs using various spectroscopic techniques is difficult. These techniques are most suited for analysis of solutions, while the PP‐phase does not dissolve in common organic solvents at room temperature. To obtain more insight into the chemistry and reactivity involved between the multifunctional peroxides and EPDM rubber, several characterization techniques were employed. In the present investigation, FTIR, GC‐(FID + MS), HP‐SEC, and element analysis were used to characterize the multifunctional peroxides TBIB and DTBT, before and after the dynamic curing of the EPDM phase. The decomposition products obtained from these multifunctional peroxides are most likely grafted onto the EPDM‐rubber, thereby reducing their volatility and avoiding the common unpleasant smell. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1393–1403, 2005     

Peroxide-initiated crosslinking of polypropylene in the presence of p-benzoquinone

Crosslinking of polypropylene was investigated when initiated by thermal decomposition of organic peroxides. p-Benzoquinone was found to be an effective coagent of crosslinking. The efficiency of benzoquinone is about 5 times higher than that of polyfunctional monomers. Almost complete crosslinking of polypropylene can be reached at proper conditions.     

Chemistry of hydroperoxycarbonyls in secondary organic aerosol

Abstract

Highly oxidized multifunctional compounds (HOMs) formed through gas-phase reactions are thought to account for a significant fraction of the secondary organic aerosol (SOA) formed in low-nitric oxide (NO) environments. HOMs are known to be peroxide-rich and unstable in SOA, however, and their fate once they partition into particles is not well understood. In the study reported here, we identified particle-phase reactions and decomposition products for an α-alkoxy hydroperoxyaldehyde that served as a convenient model for HOMs, and also quantified rate and equilibrium constants for cyclic peroxyhemiacetal formation and the effects of particle acidity and relative humidity on reaction products and timescales for decomposition of peroxide-containing compounds. Sulfuric acid increased the rate of acetal formation and subsequent peroxide decomposition, but the effect was eliminated when aqueous seed particles were used in humid air, indicating that organic/aqueous phase separation can affect the ability of strong acids to catalyze these and other reactions in SOA. The results will be useful for understanding and predicting the atmospheric fate of organic peroxides and the effects of their particle-phase reactions on SOA composition.

Copyright © 2018 American Association for Aerosol Research     

Crosslinking of polypropylene in the presence of polyfunctional monomers

The crosslinking of atactic and isotactic polypropylene initiated by organic peroxides in presence of diallyl maleate or pentaerythrityl tetramethacrylate was studied. The influence of concentration of the components of the crosslinking system as well as the effect of temperature and reaction time was followed. For high yield of gel, a high rate of initiation is necessary. Also the rate of reaction of double bonds must be similar to the rate of peroxide decomposition.     

Lipid oxidation: Mechanisms,products and biological significance

This paper reviews our studies of fatty acid hydroperoxides, their secondary products and mechanisms for their formation in the context of some of their possible biological consequences. The uneven distribution of isomeric hydroperoxides in oxidized linolenate and photosensitized oxidized linoleate is related to the formation of hydroperoxy cyclic peroxides. Interest in the hydroperoxy mono-and bi-cycloendoperoxides from oxidized linolenate stems from their structural relationship to the prostaglandins. However, the biological activity of hydroperoxy cyclic peroxides formed by autoxidation has not yet been reported. Thermal decomposition studies of secondary lipid oxidation products show they are important precursors of volatile compounds. An acid-acetalation decomposition procedure establishes that 5-membered hydroperoxy cyclic peroxides and 1,3-dihydroperoxides are important precursors of malonaldehyde. This approach provides a more specific test than the thiobarbituric acid (TBA) color reaction to evaluate lipid oxidation products as sources of malonaldehyde and its biological effects due to crosslinking. A better understanding is needed of the biological effects of a multitude of lipid oxidation decomposition products other than malonaldehyde.     

Peroxide modification of linear low-density polyethylene: A comparison of dialkyl peroxides

A commercial-grade LLDPE resin was cross-linked using three different dialkyl peroxides, at three different concentrations. The peroxides were ranked in order of their Cross-linking efficiency and their effectiveness at increasing the storage modulus of the virgin resin at the cure temperature. The chemical mechanism by which the cross-linking occurs is shown to be closely related to the changes in concentrations of reactive vinyl species on the polyethylene molecules, which follows well with proposed mechanisms of previous publications. Finally, a direct relationship is shown to exist between the rate of peroxide decomposition and the rate of increase in storage modulus of the rubbery modified resin during the curing reaction. © 1993 John Wiley & Sons, Inc.