Acetic acid/water separation by pervaporation with silica filled PDMS membrane

Silica‐filled polydimethylsiloxane (PDMS) composite membranes are prepared on a polytetrafluoroethylene support structure. The structure and the performance of the membranes are characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X‐ray diffraction, and thermogravimetry. The pervaporation process for acetic/water separation is performed within the PDMS membranes. The vulcanization temperature was found to have a great influence on the separation performance of the membrane. The addition of silica can significantly improve the pervaporation flux and enhance the thermal stability of the membrane. With an increase in the feed temperature, selectivity decreases and permeation flux increases. Performed with a pure PDMS membrane vulcanized at 30°C, the separation factor at first will increase, then decrease when the feed flow rate was increased from 14 to 38 L · h^?1. The maximum separation factor is achieved when the feed flow rate is 26 L · h^?1. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

白炭黑补强ESBR混炼胶中网络结构的研究

试验研究白炭黑补强乳聚丁苯橡胶（ESBR）混炼胶中的网络结构及网络结构对胶料门尼粘度和动态粘弹性的影响.结果表明,在白炭黑补强ESBR胶料中加入偶联剂Si69并进行热处理可显著提高胶料中的结合胶含量及网络结构的稳定性,网络结构受停放时间和温度的影响较小.与未加偶联剂Si69或加入偶联剂Si69但未进行热处理的胶料相比,加入偶联剂Si69并进行热处理的胶料中网络结点主要由柔性的橡胶组成,网络承受变形能力较强;胶料的门尼粘度和动态模量较小,且动态模量对应变（ε）变化不敏感;ε较小时动态损耗较大,ε较大时动态损耗较小。     

Chemometric solid-state C NMR analysis of morphology and dynamics in irradiated crosslinked polyolefin cable insulation

The relative concentrations and carbon spin-lattice relaxation constants (T_1,C) of the amorphous, intermediate, and crystalline phases of unaged crosslinked polyolefin cable insulation (ultimate elongation, e=310%), ⁶⁰Co γ-irradiated (e=22%), and irradiated+annealed (e=220%) samples were determined by chemometric analyses of directly polarized solid-state ¹³C NMR spectra. The T_1,C relaxation curves of the intermediate and amorphous components were found to be mono-exponential. The intermediate component contains 23±5% of the CH₂ segments in the unaged sample and has an T_1,C relaxation constant of 1.4±0.3 s. γ-Irradiation caused a slight decrease in the amount of intermediate component to 19±5% and an increase of the relaxation constant to 1.8±0.3 s. The subsequent annealing of the irradiated sample resulted in an additional increase of the relaxation constant to 2.1 s and a slight loss of crystallinity. The amorphous T_1,C relaxation constants were found to be identical in all three samples and have a value of 0.38±0.03 s. At ambient temperature, the crystalline phase was found to relax via chain diffusion from the intermediate component. The rate of helical jumps was twice as fast in the irradiated and irradiated+annealed samples compared with the unaged material.     

Isoprene rubber filled with silica generated in situ

We modified synthetic isoprene rubber by means of the in situ generation of silica particles through the sol–gel process starting from tetraethoxysilane (TEOS) as an inorganic oxide precursor. Different reaction conditions were investigated with variations in the initial TEOS content, the reaction time of the sol–gel process, and the presence of a coupling/surfactant agent (octyltriethoxysilane). Organic–inorganic hybrid materials with a silica content up to 70 phr were obtained with the complete conversion of TEOS to silica for a long enough sol–gel reaction time. A very homogeneous dispersion of silica particles was observed in all cases together with a very good adhesion between the filler and matrix. The size of the in situ generated silica was controlled by the appropriate addition of octyltriethoxysilane. Swelling and extraction tests and dynamic mechanical analysis indicated that the vulcanization process of isoprene rubber was perturbed by the sol–gel process; this led to a slight decrease in the crosslinking degree. However, a significant reinforcing effect due to the presence of silica particles was observed for all of the investigated samples. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Dielectric and thermal studies of segmental dynamics in silica/PDMS and silica/titania/PDMS nanocomposites

Effects of silica and silica/titania nanoparticles on glass transition and segmental dynamics of poly(dimethylsiloxane) (PDMS) were studied for composites of a core–shell type using differential scanning calorimetry, thermally stimulated depolarization current, and dielectric relaxation spectroscopy techniques. Strong interactions between the filler and the polymer suppress crystallinity (T_c, X_c) and affect significantly the evolution of the glass transition in the nanocomposites. The segmental relaxation associated with the glass transition consists of three contributions, arising, in the order of decreasing mobility, from the bulk (unaffected) amorphous polymer fraction (α relaxation), from polymer chains restricted between condensed crystal regions (α_c relaxation), and from the semi‐bound polymers in an interfacial layer with strongly reduced mobility due to interactions with surface hydroxyls of silica and silica/titania nanoparticles (α′ relaxation). The evolution of surface affected CH₃ groups, as well as the degree of interaction of PDMS molecules with surface hydroxyl groups as a function of treatment temperature, was assessed by Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis. The effectiveness of silica/PDMS and silica/titania/PDMS nanocomposites as hydrophobic coatings was investigated by static contact angle measurements. It was shown that the presence of titania nanoparticles and adsorbed PDMS promotes the hydrophobic properties of the PDMS coating after treatment in the 80–650°C range. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41154.     

Magnetic Resonance Visualisation of Flow and Pore Structure in Packed Beds with Low Aspect Ratio

Different NMR techniques were combined to obtain the structure and velocity information for a systematic investigation of fixed beds with low aspect ratio (tube diameter to particle diamter, d_t/d_p) in the range 1.4 to 32. The structure of the void space was determined for a variety of packed beds of glass beads or regular and irregular porous pellets by magnetic resonance imaging (MRI). Based on the images the radial distribution of the voids within the bed was obtained. Ordering effects were found even for non‐spherical and polydisperse particles, and a maximum of the fluid density near the tube wall was confirmed for all pellet geometries and sizes. By combining MRI with velocity encoding, velocity profiles and distributions of flow velocity components of a single fluid phase through packed beds have been acquired. The radial velocity distribution follows an oscillatory pattern which largely reflects the ordering of the particles, which can be accessed from the density distribution of the interparticle fluid. Maximum velocities of up to four times the average value were found to occur near the tube wall. This wall effect was observed for all but the smallest particles, where the aspect ratio was d_t/d_p = 32. Moreover, a visualisation of flow pattern in the presence of packed particles was achieved by using a tagging technique, and the stationary flow field could be identified for an experimental time of several hours.     

Influence of network chain orientation on the mechanical property of epoxy resin filled with silica particles

When tensile stress was applied to epoxy resin filled with silica particles, we expected that the stress concentration would occur in the epoxy matrix near the interface between the matrix and the silica particles. We investigated the plastic deformation of the network chains near the interface, which was quantitatively evaluated using a polarized microscope FTIR technique. A biphenol‐type epoxy resin, which has a mesogenic group in the backbone moiety, was used as the matrix resin. As a result, reorientation of the network chains along the direction of the tensile stress near the interface with the silica particles was observed. Especially when the silica/matrix interface has good bonding properties, the reorientation of the network chains was observed at a larger area around the silica particles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 787–794, 2003     

Supermolecular morphology of polypropylene filled with nanosized silica

The supermolecular morphology of injection‐molded SiO₂/polypropylene (PP) nanocomposites was investigated via thin sections analyzed under polarized light and the systematic development of an appropriate etching technique, which allowed the study of the supermolecular morphologies with light microscopy (LM) and high‐resolution field emission scanning electron microscopy (FESEM). In parallel, information regarding the dispersion, distribution state, and morphology of SiO₂ particles was investigated via transmission electron microscopy (TEM) and scanning electron microscopy (SEM) of the ion‐polished and fractured surfaces of SiO₂‐filled PP. The TEM/SEM results demonstrated an almost homogeneous dispersion and distribution of SiO₂ particle agglomerates in the PP matrix. With polarized transmitting LM, reflecting LM, and FESEM, the spherulitic structure of the nanocomposites could be visualized to obtain information on the nanoparticle influence on the crystallization and structural behavior. The size and size distribution of the spherulites analyzed with transmitting light (thin sections) and reflecting light (etched specimens) showed an excellent correlation. With increasing filler loading, the mean size of the spherulites decrease as did the degree of crystallinity. This was a clear indication that the particles acted as nucleation agents and, on the other hand, hindered the arrangement of the molecules during the crystallization. As a result, the particles were most likely located in three areas: the center of the spherulites, the areas between the highly crystalline branches, and the spherulite boundaries. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39655.     

Magnetic Resonance Imaging in Chemical Engineering: Basics and Practical Aspects

The huge potential of nuclear magnetic resonance imaging is increasingly exploited in chemical engineering. However, optimal use of this rather complex method requires some background knowledge. In this paper, first the basic principles are presented in a form dedicated to readers with an engineering formation. Subsequently, practical aspects such as resolution in space and time are discussed. Emphasis is put on established methods implemented on standard magnetic resonance imaging (MRI) hardware, as mainly used in the research presented in this issue.     

Modeling of network degradation in mixed step-chain growth polymerizations

The ability to form degradable hydrogels having controlled network structure is important for applications related to both drug delivery and tissue engineering. Although significant advances have occurred, these applications cannot reach full potential without the availability of materials with tunable degradation behavior. Here, we present novel thiol-acrylate degradable networks, which provide a simple method for forming degradable networks having specific degradation profiles. Degradable thiol-acrylate networks are formed from copolymerizing a thiol monomer with PLA-b-PEG-b-PLA based diacrylate macromers. A theoretical model has been developed to describe the kinetic chain length distribution, the bulk degradation behavior, and the reverse gelation point of these thiol-acrylate hydrogels. Varying the thiol functionality, as well as the relative stoichiometries of the thiol and acrylate functional groups, provides a facile means to control the kinetic chain length distribution and the concomitant degradation behavior of these systems. The extent of percentage mass loss of the network at the reverse gelation point is controlled from as low as 30% to as high as 95%, thereby giving the unique ability to dictate the material properties of the hydrogel before the network becomes completely soluble.     

己脒定的合成

己脒是合成新型去屑止痒剂-己脒定二羟基磺酸盐的重要原料,它的应用开发前景广阔。文章是以对氰基苯酚为起始原料,通过一系列的亲核取代等反应得到己脒产物。通过核磁共振对产物进行了简单的解析,确定是目标产物。     

Characterization of aged nitrile rubber elastomers by NMR spectroscopy and microimaging

¹H spin-lattice and spin-spin NMR relaxation times change markedly during the aging of nitrile rubber elastomers. NMR microimaging reveals heterogeneous changes in the aged samples. Aging proceeds mainly via additional chain cross-linking, and scission of the polymer chains does not appear to contribute. T₁ imaging shows that there is no spatial distribution of spin-lattice relaxation times.     

Effect of filler network on dynamic viscoelastic properties of uncured polymethylvinylsiloxanes filled with silica and carbon black

Dynamic properties of polymethylvinylsiloxane (PMVS) filled with filler‐blends composed of carbon black (CB) and silica (SiO₂) were investigated using an advanced rheometric expansion system. A variety of weight fraction of CB to SiO₂ were 0/100, 10/90, 30/70, 50/50, 70/30, 90/10, and 100/0, and a bifunctional organsilane, bis(3‐triethoxysilylpropyl)tetrasurfane, was used to facilitate the filler dispersion. The results reveal that the incorporation of CB/SiO₂ filler‐blends into PMVS result in a reduced Payne effect. This effect reaches a minimum when the ratio of CB/SiO₂ approaches 1, and then it began to rebound with the ratio increase. Meanwhile, a characteristic Newtonian viscosity plateau appearing in low frequencies also significantly decreases, depending on the amount of CB or SiO₂ added. On the basis of a simplified Fowke model, we ascribe this phenomenon to the deteriorated filler network, which is predominantly induced by the totally different surface activity between CB and SiO₂. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3477–3482, 2006     

Combination of Time‐Dependent Self‐Diffusion Measurements (Dynamic Imaging) with Magnetic Resonance Imaging

The new NMR method, demonstrated in the present work, allows within local small volumes the determination of integral structural parameters like the surface‐to‐pore volume ratio or the tortuosity of a fluid‐filled porous medium. A combination of conventional imaging (MRI) with measurements of observation‐time dependent self‐diffusion (dynamic imaging) was used.     

Structure Characterization of Filled Polymers by Means of MRI

The structure of foams and filled polymers can be analyzed by means of Magnetic Resonance Imaging (MRI). It is also possible to observe the deformation behavior of the structure of foams and filled polymers in situ. A displacement experiment was performed in a magnet and observed by MRI. The NMR images are analyzed by image processing. Average distances between particles are estimated by the use of the autocorrelation function and the spectrum of the autocorrelation function. The spectrum shows the spatial frequency of the distances. The displacement field was calculated by the cross‐correlation function. Thus, information concerning the particle distances and micromechanical deformation can be obtained by NMR imaging methods by combining autocorrelation and cross‐correlation. Such data are important for the evaluation of the mechanical strength of filled polymers.     

Highly Resolved Determination of Structure and Particle Deposition in Fibrous Filters by MRI

A new method for the quantitative three‐dimensional structure determination of a coarse filter medium as well as the particle deposition inside this medium is described. The filter structure was imaged at a voxel resolution of 59 μm which is close to the mean fiber diameter, therefore allowing individual fibers and their position to be determined. The data processing method for determining the filter structure as well as the quantification of the mass deposited in the filter are explained in detail. For particle deposition investigations the spatial resolution used was 235 μm. Hereby, a linear correlation between deposited mass and signal intensity was observed.     

Phase-mixing and molecular dynamics in poly(urethane urea) elastomers by solid-state NMR

The dynamical heterogeneity in a series of 4,4′-dicyclohexylmethane diisocyanate-diethyltoluenediamine-poly(tetramethylene oxide) based poly(urethane urea) (PUU) elastomers was studied by solid-state nuclear magnetic resonance (NMR) methods. Extensive phase mixing was evidenced by the ¹H wideline signal, which can be approximately fitted by a single exponential model. ¹³C T₁ relaxation time measurements indicate that the hard segments (HS) exhibit some small-amplitude mobility, likely “activated” by neighboring soft segments (SS). Fitting of the time-domain wideline separation (TD-WISE) data was employed to characterize the extent of phase mixing, which revealed that a PUU elastomer contains four fractions: rigid-HS, mobile-HS, rigid-SS, and mobile-SS regions. For a variety of SS MWs, the dynamics and relative portions of rigid vs. mobile fractions among HS were substantially similar, while those for the SS exhibit large contrast. Furthermore, the dynamics in the rigid-SS fraction is at least an order of magnitude slower than that in mobile-SS for all PUUs. Greater phase-mixing substantially lowers the SS mobility, facilitating SS to undergo glass transition at high strain rates, thus can be key to enhancing dynamic mechanical strengthening.     

Interplay between nematic ordering and thermomechanical response in a side-chain liquid single crystal elastomer containing pendant azomesogen units

Photoactive materials based on azobenzene derivatives exhibit interesting properties related to the reversible photo-isomerisation between the trans and cis isomers of the azo-compound. In this work we report the preparation and physical-chemical characterization of Liquid Single Crystal Elastomers (LSCEs) containing azobenzene derivative side-chain mesogens as co-monomer. The interplay between the orientational ordering and mechanical response in the nematic phase is investigated by thermomechanical measurements as well as by deuteron NMR spectroscopy. We demonstrate that local nematic order can be reliably probed in azo-LSCEs using low molar mass deuterated cyanobiphenyl nematogen in low concentrations. No phase separation of the dopant is observed. The nematoelastic coupling eav(T)∝Sav(T) between the effective sample deformation and average nematic order parameter is present over a wide temperature range even in the systems with relatively large heterogeneity of the nematic order and misaligned nematic domains.     

ZDMA/白炭黑填充HNBR的结构与性能

以甲基丙烯酸锌(ZDMA)/白炭黑填充氢化丁腈橡胶(HNBR),研究ZDMA/白炭黑并用比、硫化剂DCP用量及硫化时间对HNBR硫化胶结构和性能的影响。结果表明,在填料总量不变的前提下,随着白炭黑用量的增大,ZDMA/白炭黑填充HNBR硫化胶拉伸强度和压缩永久变形先减小后增大,填料分散性下降;随着硫化剂DCP用量的增大,ZDMA/白炭黑填充HNBR硫化胶物理性能和动态性能提高,填料分散性变好。当ZDMA/白炭黑并用比为10/30、硫化剂DCP用量为5～6份、一段硫化条件为160℃×45min、二段硫化条件为150℃×(9～12)h时,ZDMA/白炭黑填充HNBR硫化胶综合性能较好。     

改性接枝白炭黑填充丙烯酸酯橡胶的性能研究

主要探讨了甲基丙烯酸缩水甘油酯(GMA)接枝改性的白炭黑与橡胶的作用机理及在橡胶基体中的分散性。研究了不同种类和不同用量的白炭黑对丙烯酸酯橡胶(ACM)力学性能的影响。实验结果表明:接枝GMA的白炭黑在橡胶基体中具有较好的分散性,接枝改性的白炭黑与橡胶基体具有很好的相容性,接枝GMA的白炭黑填充的ACM力学性能较好;在白炭黑质量分数为40%时,拉伸强度达到最大值10.2MPa,而断裂伸长率在白炭黑质量分数为50%时,达到最大值345%。