Untersuchungen zur Haftungsbeeinflussung von Pigmentdrucken durch UV-Laser-Behandlung

Investigations on Adhesion of Pigment Printings by UV-Laser Treatment Investigations on the influence of UV-laser treatment of polyethyleneterephthalate and polyamide fibers and foils on the adhesion properties of pigment printings are presented. It could be shown that even irradiation with low energy densities and low number of pulses applied increases binder film adhesion very efficiently. Some interpretations of the laser action upon adhesion improvement related to surface modification are presented.     

Transcrystallinity effects in high‐density polyethylene. I. Experimental observations in differential scanning calorimetry analysis

The crystallization of a high‐density polyethylene was analyzed with differential scanning calorimetry (DSC) measurements. An intense transcrystallinity was observed at the contact between the polymer and the DSC pans. The modification of the crystallization kinetics induced by this phenomenon was studied as a function of cooling rate and sample thickness. We point out that most of the theoretical predictions of our previous model could be checked. The crystallization temperature was a function of the sample thickness and could be also correlated with the thickness of the transcrystalline zones. The shapes of the DSC traces were complex and correlated with the amount of trancrystallization. The usual interpretations of such DSC curves were not accurate. We conclude that specific experimental procedures must be proposed to understand and correctly use such measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 725–733, 2002     

TiO2 nano-flakes with high activity obtained from phosphorus doped TiO2 nanoparticles by hydrothermal method

TiO₂ nano-wires (Ti-NWs) and nano-flakes (Ti-NFs) were obtained from phosphorus doped TiO₂ nanoparticles (Ti-P) by hydrothermal method and by subsequent heat treatment respectively. FE-SEM micrograph of the as prepared sample depicts well formed, entangled and randomly oriented nano-wires morphology, which changes to nano-flakes morphology after heat treatment. Structural characterization of the samples by X-ray diffraction shows anatase phase for both the samples. Absorption edge of the Ti-NWs sample shows blueshift where as the Ti-NFs sample exhibit redshift compared to precursor sample as evidenced by UV–Visible absorption spectra, which is due to change in morphology and crystallinity of the samples. XPS studies indicate the presence of titanium and oxygen species only. From the EPR measurements with in-situ visible light irradiation, the number of photogenerated charge carriers is found to be very high for nano-flakes sample. Methyleneblue degradation profiles depict very high activity of Ti-NFs sample compared to Ti-NWs and the precursor samples, which is due to the observed redshift in the absorption edge, change in morphology and high crystallinity of the sample which in turn increases the optical response and separation of photogenerated charge carriers as evidenced by the optical and EPR measurements respectively.     

General Requirements and Recommendations for Vapor Nucleation Rate Experiments

Agreement between experimentally measured vapor nucleation rates and current theoretical predictions exists for only a limited number of systems. These inconsistencies can result from differences in measurement methods and assumptions used to interpret the experimental results. Usually the causes of these disagreements are unclear. The current state of the art is such that experimental results using different methods can lead to very different interpretations of the same phenomenon. In this note, well-defined standard systems are suggested as a means to verify experimental system performance. The combination n-pentanol-helium is suggested as a standard reference system. Using this system, measurements produced by multiple research groups have been compiled, and from these experimental results, a nucleation rate equation was developed that can serve as a standard basis for method comparison. This equation provides a scale to relate nucleation rates over a range of nucleation temperatures and is a useful basis of comparison even if the proposed equation is not fully accurate. It is further suggested that the nucleation rate measurements be performed using small steps in nucleation temperature of around 2 or less to identify the features in the system such as phase changes in the critical embryos. In this note, a method that uses monotonicity and continuity conditions for the nucleation rate surface to detect such singularities is outlined. These monotonicity and continuity criteria can be formulated as a dimensionless quantity. The semiempirical construction of nucleation rate surfaces can indicate conditions where multiple nucleation rate surfaces may be detected. Experimental systems that include size distribution measurements have the potential to discern particles produced through multiple nucleation channels such that nucleation rates can be measured for each channel. Detection of nucleation rate surface singularities is important because these singularities indicate the existence of two-channel nucleation where one-channel nucleation theory cannot be applied.     

A rapid quantitative protocol for measuring carbon nanotube degree of dispersion in a waterborne epoxy–amine matrix material

The available literature makes it very clear that accurate measurements of carbon nanotube dispersion quality are very complicated and the typical characterization is neither simple nor reliable. Most methods to quantify carbon nanotube dispersion reported in the literature require investigator-chosen assumptions or software interpretations that are impractical at best and misleading at worst for facile application. Herein, we report on the use of visible light absorption-based method(s) and validate that these were quantitative for discerning dispersibility differences for MWCNTs with three distinct surface chemistry modifications and concentration levels blended with polymeric materials. Ultimately, the dispersion quality was quantified via the trendline slope of the thickness-normalized absorbance values as a function of MWCNT concentration. Extremely poor dispersions were represented by statistically insignificant slope trendlines. Our data revealed that hydroxyl surface modification increased MWCNT dispersibility by a factor of ~2.8 and ~2.6 compared to the as-received MWCNT formulations via the absorption and the blackness methods, respectively. These results support and quantifiably validate that simple optical blackness values directly measured the degree of dispersion for MWCNTs in coatings applied to substrates, and our data support that this is a simple and effective quality control metric.     

The steady flow shear modulus of polymer melts

Relaxation times of polyethylene melts have been measured by Aloisio, Matsuoka, and Maxwell. One implication regarding their observations is that the elastic properties of polymer melts must be time-dependent. In particular, the steady-flow shear modulus depends on the strain rate. Some interpretations of data in the literature have been based on concepts in rubber elasticity where the steady-flow modulus is an equilibrium value, independent of strain rate. We have used Pao's theory for viscoelastic flow together with measurements of relaxation times to discuss the strain rate dependence of the steady-flow shear modulus of melts. The existence of a strain rate-dependent shear modulus leads naturally to a nonlinear relation between shear stress and recoverable shear strain. The conclusions regarding the molecular weight dependence of the modulus also differ from interpretations based on rubber elasticity.     

Kinetic studies of thermally induced phase separation in polymer–diluent system

Thermally induced phase separation was studied by the light scattering in polypropylene/methyl salicylate system. Data could be well fitted with the linear Cahn theory for spinodal decomposition (SD) in the early stage of phase separation. Characteristic properties of the early stage of SD, such as an apparent diffusion coefficient and an interphase periodic distance, were obtained. The periodic distance ranged from 3 μm to 4 μm. The growth of the phase‐separated structure obeyed power‐law scaling in the later stage, and the structure factor could be scaled into a universal time‐independent form. Domain sizes obtained from the light‐scattering measurements were consistent with the optical microscope measurements. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1028–1036, 2000     

Solution properties of poly(fluorostyrene-co-chlorostyrene) copolymers. I. Light scattering,differential refractometry and viscometry

The weight-average molecular weights (M?_w) of nominally random, unfractionated copolymers of ortho- and para-fluorostyrene and ortho- and para-chlorostyrene were determined by light scattering measurements in tetrahydro-furan, toluene, carbon tetrachloride and chloroform. It was shown that there is no significant variation in measured M?_w in the various solvents, a finding indicating that the copolymers are not compositionally heterogeneous. Intrinsic viscosity measurements in the same solvents established a consistent relationship between [n] and M?_w despite the differences in copolymer compositions. It was not possible to establish a similar relationship between the second virial coefficient A₂ and M?_w. It was concluded that measurements of the specific refractive index increment could be used for determining copolymer composition if the measurements were performed in thermodynamically poorer solvents. The results established for the Mark-Houwink constant α, intrinsic viscosity, and A₂ values indicated that these solvated copolymer molecules are in a less expanded conformation than are polystyrene molecules of similar molecular weights in a given solvent.     

Preliminary analysis of the 1H- and 13C-NMR spectra of poly(3-vinyl-1-methylindole)

Summary The title monomer was synthesized and polymerized via free radical initiation. The high field ¹H- and ¹³C-NMR spectra were recorded and analyzed. Many resonances displayed multiplicities indicating a sensitivity to polymer stereochemistry but, in most cases, the resolution was insufficient for any reasonable interpretations to be made. The resonances that were well enough resolved for relatively accurate measurements to be made were analyzed in terms of polymer stereochemistry. The analysis suggests that poly(3-vinyl-1-methyl-indole) is an atactic polymer.     

Factors affecting the wettability of polymer surfaces

The inconsistencies in contact angle data presented in the literature can be attributed to a number of factors. The awareness of these factors would allow novice researchers to make meaningful contact angle measurements and interpretations. In this survey the effects of surface roughness and heterogeneity, surface preparation and the presence of contaminants, the vapor environment, pressure and temperature, drop size, electrical charge, and heat transfer on the wettability of polymer surfaces were examined.     

Structure and dynamics of a pentablock copolymer of polystyrene-polybutadiene in a butadiene-selective solvent

We have examined solutions of a polystyrene-polybutadiene pentablock copolymer in n-heptane, a strongly selective solvent for polybutadiene. Small angle neutron scattering from 7 to 15% samples reveals domains about 10 nm in radius formed by the association of 200 polystyrene blocks. Dynamic light scattering measurements on 8 and 9% samples showed three modes: a fast diffusive mode related to the collective diffusion in semidilute solutions/gels; a relaxational mode related to the local dynamics of polystyrene domains trapped in the gel formed by bridging the domains with the polybutadiene chains; and a very slow diffusive mode. The relaxational dynamics persisted over the entire temperature range, becoming faster with increasing temperature, indicating a decreased microviscosity at higher temperatures. The slow dynamics seems to be connected with heterogeneities in the physical gel due to microsyneresis and almost disappeared above 50 °C. Macroscopic phase separation into two liquid phases was observed in a dilute solution of the un-associated copolymer, and into a liquid and gel phase at higher concentrations. The absence of flower-like micelles in dilute solutions and the macroscopic phase seperation suggest that the gels in the pentablock are formed by random association of multiplet domains and not by bridging of micellar domains.     

Characterizing bubbles in bioreactors using light or ultrasound probes: Data analysis by classical means and by neural networks

The applicability of neural networks to a typical biochemical engineering problem was investigated. The data treatment required for a novel technique for measuring the mean bubble size and the specific interfacial area in aerobic bioreactors was chosen as an appropriate example in case. The new measuring technique is based on either light or ultrasound transmission measurements through the dispersion. The function relating the results of such measurements to bubble size cannot be explicitly modelled. It was therefore approximated by a purely mathematical function fitted to numerically simulated examples. By training neural networks, the same unknown relationship could be mapped with similar or better precision without any prior knowledge of its structure or form and without any physical understanding of the problem.     

Properties of hydrophobically modified polyacrylamide with low molecular weight and interaction with surfactant in aqueous solution

Hydrophobically modified polyacrylamide (HMPAM), with a molecular weight of 10⁴ g/mol, was studied using a range of rheological methods and dynamic light scattering (DLS). DLS measurements indicate that the association of the modified polymer begins at low concentration. The modified polymer with high substitution forms transient networks below the critical concentration, but the networks are disrupted by the micelles formed by the polymer itself, and the networks do not contribute to viscosity enhancement. The modified polymers exhibited surface activity, and so they may be regarded as nonionic polymeric surfactants rather than thickeners. On the other hand, HMPAM is shown to interact with the surfactant SDS while PAM is inert to SDS. In the hydrophobic domains, it undergoes a surfactant‐induced association process; in the hydrophobe‐surfactant transition regions, the surfactant binds to the polymer in a noncooperative way and forms a polymer–surfactant complex. Contracted polymer chains begin to extend because of electrostatic repulsion, which can overcome the association at surfactant domains. The conformation of HMPAM polymer chains could be controlled by adding a specific amount of surfactant. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4348–4360, 2006     

Compared imbibitions of ordinary and high performance concrete with null or positive water pressure head

A method to simultaneously measure the moisture diffusion coefficient, D_θ, of unsaturated concrete, and the saturated concrete hydraulic conductivity, K_l, was developed for cylindrical specimens placed on a container filled with water that could be maintained at a given hydraulic pressure. Ordinary Portland cement Concrete (OPC) with a moderate and High Performance Concrete (HPC) with a low water to cement ratio were tested. The time dependent distribution of water content in the specimens was measured using a non-intrusive method based on gamma-ray attenuation. The measurements were conducted with varying hydraulic head (positive or null). Boltzmann's transformation was used to analyze the experimental results obtained at different hydraulic pressures and the difference between the null (or atmospheric) and positive pressure results is used to accurately determine K_l and also D_θ . This paper will present the results obtained using this original method, possible interpretations and future research.     

The critical involvement of anaerobic bacterial activity in modelling the corrosion behaviour of mild steel in marine environments

The modelling of both short- and long-term corrosion loss and maximum pit depth is increasingly of interest to engineers and others interested in predicting the remaining life of coastal and ocean infrastructure. Traditional models are demonstrably of poor quality. A more refined modelling approach applicable both to corrosion loss and to pitting of mild steel in marine environments is described. A crucial aspect is that explicit consideration is given to the influence of microbial activity. The model is unique in that it considers the governing corrosion process to change with increased exposure time. The rationale for this approach and some of the key findings are described. It is supported by observations of the corrosion response to changes in metal alloying and to water pollution effects. The model also permits more rational explanations to be offered for the effects of water velocity, depth of immersion and seawater salinity. Recently the effect of anaerobic bacteria on very early corrosion has been re-examined and an explanation offered in terms of the influence of water pollution on the initial corrosion rate. Applications to pitting corrosion of mild steel has led to new interpretations of pit data and new interpretations for the probability distributions associated with maximum probable pit depth. The model has been calibrated using an extensive re-examination of literature data and extensive use of specially commissioned field tests.     

玉米麸质阿拉伯木聚糖在水溶液中的聚集和构象

从玉米麸皮中提取碱溶性阿拉伯木聚糖(AX)并用乙醇分级。用体积排除色谱-多角度激光光散射联用(SEC-MALS)和动态光散射(DLS)研究了AX的构象和聚集。碱溶性麸质AX的相对分子质量随均方旋转半径(Rg)的变化可以用Mw~Rdfg表示。玉米麸质AX分子链的分形维数(df)为1.47,其结构因子ρ=Rg/Rh为1.70。忽略分子间作用,根据"蠕虫链"模型可以估算出玉米麸质AX的持久长度(Lp)为1.72 nm。即使在很稀的溶液中,玉米麸质AX也可以形成紧密的聚集,其df在3.0左右。     

Inverse solution for a biochemical heat source in a porous medium in the presence of natural convection

The inverse problem approach by conjugate gradient with adjoint equations is adapted to the context of a non-isothermal bioprocess, controlled by internal heat generation from microbial oxidation, as could be found in a composting reactor for instance, to determine the heat source from internal temperature measurements. The volumetric heat source is assumed proportional to the rate of consumption of a substrate by a biomass, as described by a Monod model. Computations are performed for Rayleigh numbers equal to 0.25 and 25, for a representative biochemical reaction under typical boundary conditions, for constant and temperature-dependent model parameters. The influence of noisy input data is also considered. It is found that good solutions can be obtained when heat release and diffusion occur over very different time scales. The variation of the model parameters with temperature must be taken into account, but single sensor solutions are possible at relatively small Rayleigh numbers when convection is present.     

Designing novel Sn-Bi, Si-C and Ge-C nanostructures, using simple theoretical chemical similarities

A framework of simple, transparent and powerful concepts is presented which is based on isoelectronic (or isovalent) principles, analogies, regularities and similarities. These analogies could be considered as conceptual extensions of the periodical table of the elements, assuming that two atoms or molecules having the same number of valence electrons would be expected to have similar or homologous properties. In addition, such similar moieties should be able, in principle, to replace each other in more complex structures and nanocomposites. This is only partly true and only occurs under certain conditions which are investigated and reviewed here. When successful, these concepts are very powerful and transparent, leading to a large variety of nanomaterials based on Si and other group 14 elements, similar to well known and well studied analogous materials based on boron and carbon. Such nanomaterias designed in silico include, among many others, Si-C, Sn-Bi, Si-C and Ge-C clusters, rings, nanowheels, nanorodes, nanocages and multidecker sandwiches, as well as silicon planar rings and fullerenes similar to the analogous sp2 bonding carbon structures. It is shown that this pedagogically simple and transparent framework can lead to an endless variety of novel and functional nanomaterials with important potential applications in nanotechnology, nanomedicine and nanobiology. Some of the so called predicted structures have been already synthesized, not necessarily with the same rational and motivation. Finally, it is anticipated that such powerful and transparent rules and analogies, in addition to their predictive power, could also lead to far-reaching interpretations and a deeper understanding of already known results and information.     

X-ray Fluorescence Uptake Measurement of Functionalized Gold Nanoparticles in Tumor Cell Microsamples

Quantitative cellular in vitro nanoparticle uptake measurements are possible with a large number of different techniques, however, all have their respective restrictions. Here, we demonstrate the application of synchrotron-based X-ray fluorescence imaging (XFI) on prostate tumor cells, which have internalized differently functionalized gold nanoparticles. Total nanoparticle uptake on the order of a few hundred picograms could be conveniently observed with microsamples consisting of only a few hundreds of cells. A comparison with mass spectroscopy quantification is provided, experimental results are both supported and sensitivity limits of this XFI approach extrapolated by Monte-Carlo simulations, yielding a minimum detectable nanoparticle mass of just 5 pg. This study demonstrates the high sensitivity level of XFI, allowing non-destructive uptake measurements with very small microsamples within just seconds of irradiation time.