A theory of pseudo cross-link

Summary The calculation of entanglement is reexamined and it is expressed by two factors nc² and n²c², n and c being the length of the polymer and its concentration, respectively. Both factors are concerned with the inter-coil interaction revealing in the melt viscosity so that is proportional to n^3.5c^4.5. At the melt temperature T_B, a critical chain length n_B is 256 and T_B is twice as high as t_A, i.e. a liquid-solid transition. At T_B the entropy of cross-linking becomes 2/3 times of that at T_A. The osmotic pressure increases in the semi-dilute solution by a factor of (c/c^*)^4/3, c^* being a critical concentration for overlapping. In the dilute solution in -solvents the cohesion of segments enables the independent coil to form an intra-coil linking even below c^* and induces the coil-globule transition at the -point to give rise to self-coaguration.     

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。     

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。     

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     

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 generalized flow theory

A generalized flow theory is put forward which is derived from a review of accepted types of stress–response curves. The theory is summarized in a single flow curve of universal shape from which all types of liquid flow can be interpreted. This “generalized flow curve” can be applied to polymer melts in particular, but there is no reason why it should not equally apply to solutions, dispersions, suspensions, emulsions, or pure liquids. The generalized flow curve is exactly analogous to the typical fully developed load–deformation curve which applies to tough plastics in the solid state. A molecular interpretation of the processes involved in producing the flow phenomena implicit in the various portions of the generalized flow curve is put forward. The evidence on which the theory is based is reviewed. Some fundamental implications are discussed.     

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.     

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。     

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.     

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.     

Dynamics of hydrate formation and deposition under pseudo multiphase flow

Gas hydrate formation is considered one of the major challenges in the flow assurance of deepwater oil and gas pipelines, as their blockage by hydrate can lead to significant production/economic loss and safety risk. Understanding the hydrate formation and deposition processes can improve the management methods in field development and production. This study used a high‐pressure rocking cell to simulate multiphase flow conditions to visually investigate the hydrate formation and deposition from an oil‐gas‐water system. The changing hydrate morphologies, flow pattern and particle distribution during hydrate formation were studied and a conceptual model was proposed. The relative motion of hydrates to the cell wall and the final morphology of the hydrate chunks are found to be two critical parameters for evaluating hydrate deposition characteristics in the flow system. Five types of hydrate deposition morphologies are observed and these are correlated to the hydrate porosity. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4136–4146, 2017     

A theory of case II diffusion

A theory is proposed to explain the transport behaviour of organic penetrants in glassy polymers in terms of two basic parameters: the diffusivity of the penetrant, D, and the viscous flow rate of the glassy polymer, $\text{1}\text{η}{}_0$. The rate controlling process for transport in these systems is considered to be diffusion of solvent down an activity gradient coupled with time-dependent mechanical deformation of the polymer glass in response to the swelling stress. The theory combines these two factors and is able to predict a wide range of observed transport phenomena from Fickian diffusion kinetics at one extreme to so-called Case II and Super-Case II behaviour at the other. The existence of a sharp front separating swollen and unpenetrated polymer is shown to result from the concentration dependence of the viscous flow rate.     

A modification of rubber elasticity theory

Summary Based on a reconsideration of the packing conditions in amorphous polymers, a modification of the statistical theory of rubber elasticity is derived. The main assumption is, that the mean square end-to-end distance of a free chain in the bulk state depends on the dimensions of the surrounding chains. The theory describes quite well the deformation behaviour of real elastomeric networks.