Processing window in impact-modified rigid PVC

A method is described for quickly evaluating the processing window of impact-modified rigid PVC formulations. This involves mixing the compound in a bowl mixer at various temperatures and to various levels of total work input. The impact properties are measured and plotted as a contour map versus melt temperature and work input. The melt temperature is the dominant factor in controlling the impact processing window. The total work input is a secondary effect, which mainly influences the system through shear heating effects on the melt temperature. This method was used to evaluate formulations with different impact modifiers and lubricant and filler levels. Impact modifier type, polyethylene wax, and filler concentrations are the dominant factors. The mechanisms involved are discussed.     

Real time TEM observation of alumina ceramic nano-particles during compression

The behavior of alumina nano-particles taken from a commercial powder is investigated during in situ compression experiments in a transmission electron microscope (TEM). Small particles of 40 nm in diameter can undergo severe plastic deformation without failure, whereas brittle fracture is observed for 120 nm sized nano-particles. This is evidence of a critical size under which alumina, at least in the form of nano-particles, cannot be considered as brittle materials even at room temperature and a direct observation of the grinding limit generally observed during ball milling.     

SEM–EDX and XRD characterization of zeolite NaA, synthesized from rice husk and aluminium scrap by different procedures for preparation of the initial hydrogel

A number of investigations have demonstrated that zeolite NaA could be synthesized using Si, extracted from rice husk ash; however, experiments on direct extraction of Si from rice husk (RH) are scarce. The main objective of the present study was to explore the possibility to synthesize high-quality zeolite NaA from RH and waste aluminium cans (as a source of Al), applying different procedures for the preparation of initial hydrogel and a unified procedure for crystallization of zeolite NaA. Products were characterized by SEM–EDX and XRD analyses. The investigation demonstrated that Si could be extracted directly from RH, avoiding the process of RH burning. Practically complete dissolution of Si from RH was achieved by alkali treatment (with 10 % NaOH for 7 h) at boiling temperature and atmospheric pressure, i.e. using refluxing system instead of autoclave for the preparation of Si-gel. Zeolite NaA samples synthesized from such Si-gels were pure, highly crystalline and white. Furthermore, it was found that the direct dissolution of Al in Si-gel did not affect the quality of the final product. Although this investigation was not focused on the mechanism of zeolite NaA crystallization, the results obtained indicated clearly that the history of Si-gel preparation played an important role in the nucleation and growth of zeolite NaA crystals and influenced their yield, size, and shape. Therefore, the optimization of Si-gel preparation procedure has to be considered as essential not only for the economy of the synthesis of NaA from RH, but also for the quality of the final product.     

Influence of the structure of the onium iodide salts on the properties of modified montmorillonite

Dialkyl imidazoline, alkyl pyridine and alkyl quinoline containing salts have been synthesized and used as new surfactants for cationic exchange of layered silicates, such as montmorillonite (MMT) in order to evaluate their role in the formation of intercalated MMT clays. The new salts have been characterized by FTIR, ¹H, ¹³C‐NMR spectra. These compounds have been intercalated into the layers of MMT via a solution dispersion technique and the extent of the interlayer space expansion was confirmed by using wide angle X‐ray diffraction and FTIR spectra. Thermogravimetry analysis shows that these salts can be used in place of ammonium salts to produce organophilic clays with higher thermal stability than commercial alkyl ammonium‐treated MMT. Moreover, the results also show that the imidazolium‐modified clays have a greater thermal stability compared to the quinolinium and the pyridinium‐modified clay. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The role of eye movements in the missing-letter effect revisited with the rapid serial visual presentation procedure.

When participants read a text while searching for a target letter, they are more likely to miss the target letter embedded in frequent function words than in less frequent content words. This effect is usually observed with a text displayed normally, for which it has been found that frequent function words are fixated for a smaller amount of time than less frequent content words. However, similar pattern of omissions have been observed with a rapid serial visual presentation procedure in which words appear one at a time. These parallel results would demonstrate that fixation duration per se is not the proximal cause of the missing-letter effect only if eye movements are not made during the rapid serial visual presentation procedure. Therefore, the authors performed eye monitoring during the rapid serial visual presentation procedure. Results revealed that, with a rapid serial visual presentation procedure, participants fixated function and content words for almost the entire presentation duration. It is concluded that eye movements are not the proximal cause of the missing-letter effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of Two Homogalacturonan Pectins with Immunomodulatory Activity from Green Tea

Two natural homogalacturonan (HG) pectins (M_W ca. 20 kDa) were isolated from green tea based on their immunomodulatory activity. The crude tea polysaccharides (TPS1 and TPS2) were obtained from green tea leaves by hot water extraction and followed by 40% and 70% ethanol precipitation, respectively. Two homogenous water soluble polysaccharides (TPS1-2a and TPS1-2b) were obtained from TPS1 after purification with gel permeation, which gave a higher phagocytic effect than TPS2. A combination of composition, methylation and configuration analyses, as well as NMR (nuclear magnetic resonance) spectroscopy revealed that TPS1-2a and TPS1-2b were homogalacturonan (HG) pectins consisting of a backbone of 1,4-linked α-d-galacturonic acid (GalA) residues with 28.4% and 26.1% of carboxyl groups as methyl ester, respectively. The immunological assay results demonstrated that TPS1-2, which consisted mainly of HG pectins, showed phagocytosis-enhancing activity in HL-60 cells.     

P3HT : PCBM solar cells—The choice of source material

Bulk heterojunction solar cells based on P3HT : PCBM blend films are among the most intensively studied polymer solar cells. In spite of that, there is a huge variation of reported efficiencies in the literature, even for same device architectures and film preparation procedures. Here we investigated the influence of starting properties of P3HT and PCBM (different suppliers) on blend film morphology and device performance. We found that there was a strong dependence of the film morphology and device performance on the source of chemicals used. Both P3HT and PCBM affected the results, and higher nominal purity did not necessarily result in better device performance. The dependence of the film morphology and device performance on the properties of P3HT and PCBM is discussed in detail. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39776.     

The role of interface modification on thermal degradation and crystallization behavior of composites from commingled polypropylene fiber and banana fiber

The thermal degradation behavior of banana fiber and polypropylene/banana fiber composites has been studied by thermogravimetric analysis. Banana fiber was found to be decomposing in two stages, first one around 320°C and the second one around 450°C. For chemically treated banana fiber, the decomposition process has been at a higher temperature, indicating thermal stability for the treated fiber. Activation energies for thermal degradation were estimated using Coats and Redfern method. Calorific value of the banana fiber was measured using a constant volume isothermal bomb calorimeter. Crystallization studies exhibited an increase in the crystallization temperature and crystallinity of polypropylene upon the addition of banana fiber. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

The Engineering of Bacteria Bearing Azido‐Pseudaminic Acid‐Modified Flagella

Catch a tiger by the tail : We have demonstrated that by feeding nonmotile mutant C. jejuni bacteria with a neutral azide‐labelled pseudaminic acid precursor we can restore their ability to generate functional flagella. The presence of azido‐pseudaminic acid on the surface of the flagella provides a bio‐orthogonal chemical handle that can be used to modify the flagellar proteins.