A theory of pseudo cross-link

Summary A theory of pseudo cross-link model suggests the existence of multiple links of various size composed of 116 segmental units. They possesses the heat and entropy of various magnitude giving various transition temperature, T_A for the cross-link composed of 4 segments and T_B for that of 16 segments. The glass-transition point T_g and the melting point T_m are defined by the different size of lateral multiple links. Relationships, T_m = 2 T_A and T_g = (2/3)T_m = (4/3)T_A, are derived. A wedge-type relaxation spectrum is obtained as a distribution of size of cross-links. For temperature dependence the WLF-equation is obtained.     

Theory of pseudo cross-link

Summary Stress-relaxation, creep and stress-strain relations are discussed in terms of pseudo cross-link concept. The decrease of cross-links by the stress or strain leads to an equation similar to the Mooney-Rivlin equation. Viscous flow is also an important factor decreasing the cross-sectional area of the specimen and the chain-extension. Viscosity much decreases with increasing rate of extension and temperature. Filler ingredient plays roles of not only enchancing the chain strain but also providing the pseudo cross-link due to adsorption of the rubber on the filler surface.     

A carbonium pseudo ionic liquid with excellent extractive desulfurization performance

Lewis hard acid AlCl₃ was softened by some butyl halides forming highly polarized liquids. These liquids are similar to the ionic liquids (ILs) with metallic complex anion and varying composition, and thus termed here as carbonium pseudo ILs (CPILs). The CPILs, that is, t‐C₄H₉Cl‐AlCl₃, n‐C₄H₉Cl‐AlCl₃, and t‐C₄H₉Br‐AlCl₃, show very strong desulfurization activity for various thiophenic compounds like 3‐methylthiophene, benzothiophene, and dibenzothiophene. The above thiophenic compounds can be removed completely from model oils within 20 min by a very small amount of CPILs reactive extractant. The extractive mechanism is deemed as an acid–base complexation along with alkylation of the thiophenic compounds, and the Lewis acidity comes from both carbonium ion (borderline acid) and the dissolved AlCl₃ (hard acid). The t‐C₄H₉Cl‐AlCl₃ shows good selectivity for three thiophenic compounds even in toluene‐containing system. Further, some CPILs show satisfactory desulfurization performance for the model gasoline that mimics the composition of real one. © 2012 American Institute of Chemical Engineers AIChE J, 59: 948–958, 2013     

Chromogenic cross-link formation in green fluorescent protein

Recent advances in our understanding of the mechanism of chromophore formation in green fluorescent protein (GFP) are presented. GFP is the best-studied member of the family of GFP-like proteins, proteins that exhibit bright coloration spanning most of the visible spectrum. GFPs undergo a post-translational self-modification process that yields an intrinsic fluorophore constructed from an internal main-chain cross-link that is susceptible to air oxidation. A combination of protein X-ray crystallographic and kinetic experiments has led to the development of a mechanistic model that entails conformational pre-organization, electrophilic and base catalysis, and production of hydrogen peroxide upon protein oxidation. The process is concluded by a slow proton abstraction step from a tyrosine-derived carbon acid.     

Regime transition in viscous and pseudo viscous systems: A comparative study

A comprehensive quantitative study on the effect of liquid viscosity (1 ≤ µ_L ≤ 1149 mPa‐s) on the local flow phenomena of the gas phase in a small diameter bubble column is performed using ultrafast electron beam X‐ray tomography. The internal dynamic flow structure and the bubble size distribution shows a dual role of the liquid viscosity on the hydrodynamics. Further, the effect of solid concentration (C_s = 0.05, 0.20) on the local flow behavior of the gas phase is studied for the pseudo slurry viscosities similar to the liquid viscosities of the gas–liquid systems. The effects of liquid and pseudo slurry viscosities on flow structure, bubble size distribution, and gas phase distribution are compared. The bubble coalescence is significantly enhanced with the addition of particles as compared to the system without particles for apparently same viscosity. The superficial gas velocity at which transition from homogeneous bubbly to slug flow regime occurs is initiated by the addition of particles as compared to the particle free system for apparently same viscosity. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3079–3090, 2014     

Influence of cross-link density on the properties of ROMP thermosets

A norbornene-based cross-linker was synthesized and mixed at different loadings with two separate monomers for self-healing polymer applications: 5-ethylidene-2-norbornene (ENB) and endo-dicyclopentadiene (endo-DCPD). The monomer/cross-linker systems were polymerized by ring-opening metathesis polymerization (ROMP) with Grubbs' catalyst. The thermal-mechanical properties of the polymerized networks were evaluated by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) and the curing process was monitored by parallel plate oscillatory rheometry. The viscosities of the pre-polymer blends are shown to be adequately low for self-healing, and exhibit a high ROMP reactivity to form cross-linked networks with enhanced thermal-mechanical properties. The addition of cross-linker increases the glass transition temperature (T_g) and the storage modulus both above and below T_g. The storage modulus increase above T_g is used to estimate the molecular weight (M_c) between entanglements or cross-link sites for both ENB and endo-DCPD-based networks. The cross-linker also greatly accelerates network formation as defined by the gelation time.     

丙烯腈接枝交联淀粉的制备及应用研究

以玉米交联淀粉为原料,环氧氯丙烷为交联剂,制备了交联接枝玉米淀粉;再以FeSO4-H2O2为引发剂,研究了丙烯腈接枝交联淀粉的制备工艺及其在处理生活污水方面的应用。结果表明,10g玉米交联淀粉、丙烯腈用量10mL、引发剂用量4mL、接枝时间1.5h、反应温度40℃,此条件下接枝率可达83.7%,接枝效率为116.3%,丙烯腈接枝交联淀粉处理过的污水透光率达96.5%。     

微生物凝固天然橡胶交联密度的研究

采用核磁共振交联密度仪,考察了微生物凝固天然橡胶（NR-m）和酸凝固天然橡胶（NR-a）在硫化过程交联密度（XLD）、网链含量（AMc）、自由小分子含量（AT2）以及相邻交联点间的分子质量（Mc）的动态变化规律。研究结果表明,NR-m硫化胶的XLD比NR-a的高,NR-m硫化胶磁化曲线随时间衰减的速率比NR-a快,纵向松弛时间（T1）和横向驰豫时间（T2）比NR-a低,NR-m硫化胶网链部分的质量含量（AMc）明显高于NR-a的,而自由末端数则明显比NR-a的低。这表明微生物凝固法促进了天然橡胶的硫化作用,提高了硫化胶的交联密度。     

一种基于伪Wigner-Ville分析的动态优化问题网格重构策略

为了解决控制向量参数化方法逼近精度和计算时间之间的矛盾，提出了一种基于伪Wigner-Ville时频分析的控制向量参数化方法。该方法首先给定较少的网格进行第一次优化迭代，快速获得控制变量的大致轨迹。然后通过伪Wigner-Ville分析得出不同时间网格节点瞬时频率变化对性能指标的影响，籍此对原有网格节点进行重构，包括对时间节点的消除、细化。并且结合变时间节点控制向量参数化方法的思想，将瞬时频率为极大值时对应的时间节点作为待优化参数，与控制变量一同进行求解优化，从而找到准确的最优时间切换点。三个经典的化工反应实例用于验证所提方法，计算结果表明：与传统的控制向量参数化方法和文献结果相比，所提方法可以更有效地重构时间网格，找到准确的时间切换点，不仅计算成本低，而且计算精度更出色。     

准水溶性光敏环氧酚醛树脂的合成

用二甲苯胺取代溴化季胺盐作催化剂、用甲苯部分取代二氧六环做溶剂合成了准水溶性丙烯酸改性光敏酚醛树脂。实验发现,含31％（质量分数）二氧六环的混合溶剂体系有利于反应的进行,当n（环氧基）:n（丙烯酸）:n（羧基）=50∶50∶49时,其树脂能溶于1％的碳酸钠溶液;当交联体系中活性稀释剂的碳碳双键数与树脂中碳碳双键数相近、m（树脂）∶m（马来酸酐）=239∶1时,漆膜的性能最佳,可耐温230℃并具有其他优良性能。     

聚合物微球-缔合聚合物复合体系的封堵性能研究

针对海上稠油油藏地质特征及提高采收率的具体要求,选择聚合物微球与缔合聚合物进行复配,通过填砂管封堵实验和人造岩心驱油实验,发现复合体系兼具深部调剖和增黏驱油的性能,封堵性能、液流改向能力和驱油效果均优于单纯聚合物溶液。说明微球和缔合聚合物之间产生较好协同作用,为改善聚合物驱效果提供了新的方法。     

拟薄水铝石胶溶质量的表征

拟薄水铝石溶胶是FCC催化剂双铝基黏结剂的重要组成部分,影响催化剂强度,然而按照目前质量指标生产的双铝基黏结剂存在黏结性能不稳定的问题。结合现有指标,认为缺少对拟薄水铝石胶溶过程的考察。而且FCC催化剂在制备过程中,从浆液到最终喷雾干燥升温过程明显,因此,通过新的表征方式对拟薄水铝石在胶溶过程和升温过程中的黏度变化,定义了新的参数黏温活化能。结果表明,黏温活化能可以较好反映拟薄水铝的胶溶状态。     

聚合物微球-缔合聚合物复合体系的封堵性能研究

针对海上稠油油藏地质特征及提高采收率的具体要求,选择聚合物微球与缔合聚合物进行复配,通过填砂管封堵实验和人造岩心驱油实验,发现复合体系兼具深部调剖和增黏驱油的性能,封堵性能、液流改向能力和驱油效果均优于单纯聚合物溶液.说明微球和缔合聚合物之间产生较好协同作用,为改善聚合物驱效果提供了新的方法.     

A pseudo first order rate model for the adsorption of an organic adsorbate in aqueous solution

Five low rank, coal‐based adsorbents, i.e. coal, grus, two chars, and an activated carbon were used to adsorb a low molecular weight organic compound from aqueous solution. The rates of adsorption were found to conform to pseudo first order kinetics with good correlation (r² greater than 0.996). This kinetic model was used to calculate pseudo first order rate constants (k₁^′ min ⁻¹) and relative rate constants (rate constant/unit mass of adsorbent, k₁^″ min⁻¹ g⁻¹) for the adsorption process. Rate properties have been explained in terms of both a diffusion and chemically controlled rate determining step. Rate constants for the five adsorbents vary as expected on the basis of their physical properties, that is slowest for grus (compressed coal) and fastest for the activated carbon. © 1999 Society of Chemical Industry     

Polymer swelling 2: A restudy of poly(styrene-co-divinylbenzene) swelling in terms of the cross-link density1

A very convenient and reliable gravimetric method was developed for measuring swelling of poly(styrene-co-divinylbenzene) in particulate form. The method is based on the gravimetric procedure reported earlier² for monitoring liquid uptake by thin (<0.3 mm) microporous composite films, consisting of swellable particulate (80% by weight) enmeshed in poly(tetrafluoroethylene) microfibers (20%). The swellability S (in milliliter of liquid absorbed per gram of polymer in equilibrium with excess liquid) for six sty-co-DVB polymers with crosslink densities ranging from 0.01 to 0.12 was measured in 19 organic liquids. In each study of S as a function of the relationship was given by where is the average number of carbon atoms in the “backbone” of the polystyrene segments between cross-link junction, C is the relative swelling power of the liquid, and is the critical cross-link density above which S is equal to zero.     

Investigation of DNA-protein cross-link formation between lysozyme and oxanine by mass spectrometry

Reactive nitrogen species are implicated in inflammatory diseases and cancers. Oxanine (Oxa) is a DNA lesion product originating from the guanine base through exposure to nitric oxide, nitrous acid, or N-nitrosoindoles. Oxanine was found to mediate formation of DNA-protein cross-links (DPCs) in the cell extract. We have previously characterized two DNA-protein cross-links from the reaction between Oxa and glutathione: namely, the thioester and the amide. In this study, lysozyme was used to study site-specific modification on protein by Oxa moieties in DNA. With the aid of nanoLC coupled with nanospray ionization tandem mass spectrometry, addition of Oxa was found at Lys13, Lys97, Lys116, Ser85, and Ser86 of lysozyme when it was treated with 2'-deoxyoxanosine (dOxo). Furthermore, incubation of lysozyme with Oxa-containing calf thymus DNA, produced by treating DNA with nitrous acid, led to lysozyme modification at Lys116, Ser85, and Ser86. Interestingly, none of the cysteine residues was modified by dOxo, in contrast with our previous findings that dOxo reacted with oxidized glutathione disulfide, forming the thioester. This might be due to the half-life of the dOxo-derived thioester being 2.2 days at the pH of incubation. Furthermore, the sites of modifications on lysozyme are in good agreement with the solvent accessibility of the residues. Since repair of Oxa-derived DPCs has not been extensively investigated, these results suggest that these stable DPCs might represent important forms of cellular damage caused by reactive nitrogen species involved in inflammationrelated diseases.     

交联型高粘度醋-丙共聚油画布胶的研制

以聚乙烯醇为保护胶体,在催化剂作用下,加以增稠剂,对醋酸乙烯-丙烯酸酯共聚乳液进行改性增粘,可以获得低固含高粘度,满足于油画布上胶需要的乳液制品。     

A new gelation theory

Summary Based on an infinite network gel model, using Graph theory and Probability as investigative tools, first of all, advanced a new theory about predicting the gel point P_c The critical state equations of gelation for three kinds of non-linear polymerization have been derived. The P_c obtained by these equations lies between the results from Carothers equation and Statistical theory, and is in good agreement with experimental results.     

A modified absorption theory

Absorption is normally considered as comprising two separate mechanisms, viz adsorption and capillary condensation. One part of the water (or other absorbed substance) is assumed to be adsorbed, the other part capillary condensed. By means of a small modification to the BET-theory for adsorption, this theory can be made to describe the total absorption as one mechanism, where no difference is made between adsorbed and condensed water. The application of the modified theory to cylindrical and slit-shaped pores is demonstrated. Desorption is also discussed.