Weathering of low‐density polyethylene grafted with itaconic acid in laboratory tests

Polyethylene grafted with itaconic acid was subjected to weathering under laboratory accelerated conditions. The course of the photo‐oxidative degradation process of that material was studied by FTIR spectroscopy both through quantitative measurements of changes in absorbance values at selected wave numbers and through measurements of surface area values for absorption bands which were separated by means of deconvolution. The use of both those procedures of quantitative determinations resulted in a general conclusion that the oxidation process was initiated from the very first moment of irradiation, and it produced ketones, acids, esters (intramolecular and of acetate type), peracids, peresters, hydroperoxides, and alcohols. The molecular weight values and gel number values, which were established as well, pointed out that oxidation was accompanied by cracking of polymer macromolecules, and also by polymer crosslinking to a limited degree. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A supported titanium postmetallocene catalyst: Effect of selected conditions on ethylene polymerization

Ethylene polymerization with a titanium complex [N,N‐ethylenebis(3‐methoxysalicylideneiminato)titanium dichloride] immobilized on the magnesium support with the formula MgCl₂(THF)_0.32(Et₂AlCl)_0.36 was studied. In particular, the effects of polymerization temperature, monomer pressure, and polymerization time on the activity of the catalyst and on the polyethylene properties (molecular weight and its distribution, melting point, crystallinity, and bulk density) were evaluated. The findings of investigations prove that the studied supported titanium catalyst is highly active in ethylene polymerization, and its activity increases with increasing temperature and monomer pressure. Moreover, stability of the catalytic systems is dependent on the activator type used. Me₃Al, when employed as an activator, makes the catalytic system undergo no deactivation in practice. The catalyst coupled with MAO turned out less stable. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Reliability analysis in building physics design

The idea of reliability analysis in building physics design is presented. Reliability of building performance is described in terms of the probability of exceeding the critical values by the physical measures as a result of the changes of physical state of a building due to variations of climatic, structural or serviceability parameters.     

Starch modified by high-pressure homogenisation of the pastes – Some structural and physico-chemical aspects

According to literature data, high-pressure homogenisation of starch paste in the optimum conditions gives a product of digestibility reduced by 50%. This product has been analysed from the point of view of its resistance to enzyme activity. Results obtained by X-ray diffraction, scanning electron microscopy, optical microscopy and measurements of surface activity prove that reduction in the product digestibility is not related to changes in its crystalline structure and morphology of its particles. The product of high-pressure homogenisation of the paste is also found to be characterised by very slow kinetics of wetting. In comparison to the native starch, the aqueous solutions of the product of homogenisation show significantly different surface activity and different mode of iodine complexation.     

An inter-laboratory evaluation of new multi-element reference materials for atmospheric particulate matter measurements

Eight institutes using 12 different instruments analyzed newly developed multi-element reference materials (RM) for atmospheric particulate matter (PM) measurements. These RM have the potential to fill a gap in the currently available quality assurance resources for element analysis of PM samples such as X-ray fluorescence and inductively-coupled plasma mass spectrometry. This study evaluates the performance of these new RM generated by the University of California, Davis. The methodological challenge was to determine the reference loadings on the RM. Gravimetry is the most robust method to determine the sample deposit mass but cannot be used for these RM because some solution components are volatile and result in unpredictable total mass loadings on the RM. Instead of using gravimetry, a single well-measured element, along with the assumption that the relative mass fractions in the solutions were maintained in the aerosol deposited on the filters, was used to determine the reference loadings on the RM. This assumption appears to be valid for most elements in the solutions; notable exceptions include volatile species such as chlorine and bromine. Results from the 12 different instruments in the inter-laboratory evaluation agreed very well with the reference loadings (adjusted R² > 0.9 and slope between 0.7 and 1.3) for 17 of the 28 elements. In many cases, one or two instruments did not meet the performance criteria, which points to individual instrument calibration problems. For the 11 elements that did not perform as well, development work continues, and this intercomparison helped identify and fix a source of contamination in the system used to create the RM.

Copyright © 2019 American Association for Aerosol Research     

Mesoporous silica obtained by polycondensation of octahydridooctasilsesquioxane

Mesoporous silica, due to its porosity and morphological features, have been considered a fascinating material for many technological applications. In this report, we describe the preparation of a structurally stable mesoporous silica material using octahydridooctasilsesquioxane (T₈ ^H). The structure and properties of final samples were determined by XRD, FT-IR, and TEM methods. Structural analysis has shown that the siliceous material is amorphous but mesoporous. BET surface area, pore volumes, and pore size distribution were measured using nitrogen sorption methods—data were collected from the adsorption branch using BJH method for mesopores and t-plot method for micropores. It was found that the cage-type structure of T₈ ^H molecules and the process conditions determine the specific morphology of the cross-linked products. Completely inorganic, mesoporous silica of a narrow pore distribution was obtained. It was found that the materials have large surface area and pores in the meso range (2–5 nm). The amount of mesopores and the characteristic surface area of the prepared samples strongly depended on the reaction conditions.     

Synthesis and activity of zirconocene catalysts supported on silica-type sol-gel carrier for ethylene polymerization

Summary Synthesis and activity of bis(cyclopentadienyl)zirconium dichloride catalyst supported on unconventional silica-type material obtained in sol-gel process and activated by organoaluminium co-catalyst were studied. The effect of support modification conditions (thermal dehydration and/or modification by organoaluminium compound) and a type of co-catalyst on an activity of the catalytic system in ethylene polymerization and properties of resulting polymers were investigated and compared with results obtained earlier for vanadium catalysts supported on mentioned sol-gel carrier. The most appropriate method of the sol-gel silica-type support preparation is thermal pre-treating (200°C) followed by modification with AlEt₂Cl. Metallocene catalyst supported on such sol-gel product and activated by MAO appeared to be most active among studied systems. Studied Cp₂ZrCl₂/MAO supported on silica-type sol-gel carrier allow to obtain polyethylene (at 50°C polymerization temperature) with yield up to 30·10⁶ g/(mol_Zr·h), molecular weight below 300 000 and MWD=2−4. Received: 4 September 2000/Revised version: 3 January 2001/Accepted: 3 January 2001     

Model for the 3D Location of Buried Assets Based on RFID Technology

As construction and renovation equipment excavate in the vicinity of utility lines, the buried infrastructure is likely to suffer some form of “attack,” be that simple mechanical abrasion or a major rupture. Damage to underground services can lead to widespread disruption and significant upstream (service provider) and downstream (end user) losses, often resulting in whole communities being isolated from emergency services and losing essential utilities such as water, gas, and electricity. The ability to physically determine on site the location of underground utilities is critical to reduce risk and consequence during excavation. For these reasons, the location and efficient maintenance of buried assets are a high priority, especially for utility companies. This paper presents the development of a model for the three-dimensional (3D) location of buried assets based on radio frequency identification (RFID) technology and findings from laboratory and field experiments. Passive, low frequency RFID devices were used during the research. Two approaches of this model, “Method A” and “Method B,” along with major experimental findings are discussed within the paper. In order to validate the applicability of each method, “real-world” field experiments were performed. The findings from this research demonstrated that applying RFID technology to locate buried assets has a great potential for facilitating the accurate 3D data of underground infrastructure.     

Lattice and Grain‐Boundary Diffusion of Al in Tetragonal Yttria‐Stabilized Zirconia Polycrystalline Ceramics (3Y‐TZP) Analyzed Using SIMS

Aluminum oxide was deposited on the surface of 3 mol% yttria‐stabilized tetragonal zirconia polycrystals (3Y‐TZP). The samples were annealed at temperatures from 1523 to 1773 K. Diffusion profiles of Al in the form of mean concentration vs. depth in B‐type kinetic region were investigated by secondary ion mass spectroscopy. The experimental results for the lattice diffusion (D_B) and grain boundary diffusion (D_GB) are as follows: and where δ is the grain‐boundary width and s is the segregation factor.     

Diazepinoporphyrazines Containing Peripheral Styryl Substituents and Their Promising Nanomolar Photodynamic Activity against Oral Cancer Cells in Liposomal Formulations

The photochemical properties and photodynamic activity of three porphyrazines (Pzs) containing annulated diazepine rings, including novel demetalated porphyrazine‐possessing bis(styryl)diazepine moieties were investigated. The porphyrazines were evaluated in terms of their electronic absorption and emission properties, their tendency to undergo aggregation and photodegradation, as well as their singlet oxygen generation efficiency. The in vitro photodynamic activity of the porphyrazines and their liposomal formulations were examined by using two oral squamous cell carcinoma cell lines. Magnesium(II) tribenzodiazepinoporphyrazine ( 1 ) revealed the highest phototoxic effect in both cell lines used, H413 and HSC‐3. Encapsulation of Pz 1 into L ‐α‐phosphatidyl‐d,l ‐glycerol:1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine liposomes resulted in a nearly threefold increase in photocytotoxicity relative to that of the solution of Pz 1 (IC₅₀ values of 45 and 129 nM , respectively).