Hydrogen storage performance of methyl-substituted mesoporous silica with tailored textural characteristics

Journal of Porous Materials - The present study reports a systematic analysis of morphology and hydrogen sorption capacity of mesoporous organic-inorganic silica prepared by varying the silica...     

Effect of D-lactide content of annealed poly(lactic acid) on its thermal,mechanical, heat deflection temperature,and creep properties

In our research, the effect of D-lactide content in injection-molded and annealed poly(lactic acid) (PLA) was investigated for crystallinity as well as crystalline forms (less-ordered α′ and more-ordered α crystalline forms) and thus on the mechanical, heat deflection temperature (HDT), and creep properties. Three different PLA grades 3052D, 3001D, and 3100HP were investigated with D-lactide contents of 4%, 1.4%, and 0.5%, respectively. The injection-molded PLA specimens were then postproduction annealed in a heat chamber at 80–140 °C for 1 h to develop various crystallinities and various ratios of α′ and α crystal forms. It was demonstrated that not only annealing but also the D-lactide content significantly influences the crystallization, crystal structure, and accordingly properties of PLA like notched Charpy impact strength, HDT, and creep characteristics. Higher HDT, impact properties, and creep resistance could be reached by using PLA with lower D-lactide content with a certain annealing temperature range to develop definite crystal structures. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47103.     

Hierarchical structure of phase‐separated segmented polyurethane elastomers and its effect on properties

Polyurethanes were prepared from 4,4′‐methylenebis(phenyl isocyanate), 1,4‐butanediol and poly(1,4‐butanediol adipate) polyester polyol. The hydroxyl functional group ratio of polyol/total diol was kept constant at 0.4, while the ratio of the isocyanate and hydroxyl groups (NCO/OH ratio) changed between 0.90 and 1.15. The polymers were prepared by one‐step bulk polymerization in an internal mixer. They were characterized using a number of methods including Fourier transform infrared spectroscopy, wide‐ and small‐angle X‐ray scattering, differential scanning calorimetry, dynamic mechanical analysis, light transmittance and tensile testing. Changing the stoichiometry modifies the molecular weight in accordance with the laws of stepwise polymerization, and the relative concentration of end groups also changes at the same time. Competitive interactions among various groups including chain‐end functional groups lead to the formation of slightly ordered phases of sub‐nanometre size at both ends of the composition range. These structures assemble into larger units at the 10 nm level, which associate further to even larger entities of micrometre size causing scattering of light and a decreased transparency of the samples. The order of the primary units, together with the number and size of assemblies at both higher levels, decrease as the composition approaches equimolar stoichiometry. The amount of less ordered amorphous phase has a maximum in this range. The stiffness of the polymers is determined by the amount of this phase, while ultimate properties are influenced also by molecular weight and the number of physical crosslinks formed. Copyright © 2010 Society of Chemical Industry     

Septic complications after biliary tract stone surgery: a review and report of the European prospective study

We report a prospective, controlled study of the incidence of septic complications following biliary tract stone surgery. This study included a total of 280 patients operated on in eight hospitals in various European countries. In this study the computer program "Surgery" was used. Of 280 patients, 77 (27.5%) were male and 203 (72.5%) were female. The age ranged from 20 to 92 years (mean 54.8 years); 78.9% of the cases corresponded to clean-contaminated surgery; 85% of the patients received antibiotic prophylaxis with cefazolin. Twenty-one patients developed postoperative septic complications (7.5%) of which 12 (4.3%) were wound infections; five patients (1.8%) had intra-abdominal infections. The wound infection rate was 3.2% in clean-contaminated surgery, 7.7% in contaminated and 20% in dirty (p < 0.02). In laparoscopic cholecystectomy the global rate of septic complications was 3.6% vs. 12.6% in open cholecystectomy (p < 0.01); 2.4% and 6.3% wound infection respectively. The mean age of patients who developed postoperative septic complications was 61.5 years and 54.2 years old who did not develop any complications (p < 0.03). The duration of the postoperative period was 5 days in patients without infection and 13 days in patients with infection (p < 0.0001). Two patients died, one of them (0.4%) caused by sepsis. In addition to the European prospective study, a review of the problems of sepsis in biliary surgery was carried out.     

Small-angle X-ray scattering experiments and computer simulations to characterise anisotropy of activated carbons prepared from wood

Small-angle scattering was measured from activated carbon monoliths prepared from three different wood species (European beech, Pedunculate oak and Norwegian spruce). Substantial differences were found in the scattering images of axial and tangential slices, attributed to their characteristic phytogenic structures. The decrease in anisotropy in the nanostructured carbon matrix due to the activation process is also different among the three investigated types of wood. For quantitative characterization of the anisotropy and its decrease, the degree of alignment was calculated from the azimuthal scattering curves. A simple numeric model was constructed on the basis of direct information obtained by atomic force microscopy. Scattering patterns calculated from the model were compared with the experimental ones to explain the possible structural changes in the carbon skeleton.