Mechanical properties of blends of HDPE and recycled urea‐formaldehyde resin

The mechanical properties of blends of high‐density polyethylene (HDPE) with a recycled thermosetting filler, urea‐formaldehyde grit (UFG), were evaluated in the range of 0–23% of filler by volume. Ethylene‐acrylic acid (EAA) copolymers and an ionomer based on EAA were evaluated as compatibilizers. The observed tensile modulus of the ionomer‐treated blends was raised to three times the modulus of virgin polyethylene, whereas the modulus of the untreated blends reached double that of polyethylene. The ionomer‐treated blends also showed a higher tensile strength than the blends without filler treatment. The improvement in the properties was assigned to an increased interaction between the filler and the polymer matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3220–3227, 2000     

Combustion of Ytterbium Metal

Ytterbium metal powder burns with a luminous vapor phase diffusion flame in oxygen. Consolidated stoichiometric mixtures with both polytetrafluoroethylene and hexachloroethane upon ignition yield intense luminous flames. With UV/Vis spectroscopy of the combustion flames Yb, YbO, YbCl, and YbF species have been identified contributing to the selective emission in the green spectral range. The flame temperatures of ytterbium combustion in oxygen and with halocarbon based oxidizers are in the same range as for comparable magnesium based systems.     

Production of New Functionalized Polymer Nanoparticles and Use for Manufacture of Novel Nanobiocatalysts

New nanoparticles are synthesized through emulsion polymerization, using distinct comonomers (styrene, divinylbenzene, glycidyl methacrylate and pentafluorostyrene). Then, for the first time, two strategies are adopted to functionalize such nanoparticles using benzylamine and thiophenol: (i) after the manufacture of the nanoparticles; and (ii) in situ during the polymerization reaction. Afterwards, the functionalized nanoparticles are used as nanosupports for immobilization of lipase B from Candida antarctica and the performance of the novel nanobiocatalysts are evaluated. It is shown that the nanoparticles exhibit different properties (specific areas ranging from 34 m² g^?1 to 324 m² g^?1; and contact angles ranging from 29° to 126°), indicating that both procedures can be used to adjust the properties of the polymer supports. Moreover, the nanobiocatalysts are applied successfully in hydrolysis and esterification reactions, exhibiting higher activities than the non‐functionalized biocatalysts. It is also observed that more hydrophilic supports result in more active biocatalysts in hydrolysis (27 ± 1 U g^?1) and intermediate hydrophobic matrices conduct to more active biocatalysts in esterification reactions (1564 ± 50 U g^?1). It is shown that highly hydrophobic surfaces may cause a significant decrease in the activity of such biocatalysts, probably due to distortions on the enzyme active center and to more intense chemical partitioning effects.     

The effect of water on the thermal transitions of fish scales from Arapaima Gigas

Fish scales are collagen based structures that display interesting mechanical properties, particularly in the wet state. In this paper we study the effect of water content on the thermal transitions of scales from the Amazonian fish Arapaima Gigas by means of Differential Scanning Calorimeter (DSC) tests. The endothermic peaks found are discussed and the results are compared with previous studies of other collagen based structures. The peaks observed were found to depend on the water content of the samples. The role of water on the thermal stability of fish scales is discussed. The peak temperature related to the denaturation of collagen was found to increase with increasing water content. Hence, samples with higher water content were more thermally stable than samples with lower water content. This tendency is contradictory with regard to that observed on other collagen based structures such as bones and tendons.     

Estonian electricity supply scenarios for 2020 and their environmental performance

Estonia is the only country in Europe with significant environmentally intensive oil shale-based energy production. However, the legal obligations of the EU will make substantial changes over the coming years to current electricity production technology. Increasing the use of alternative energy carriers for responding to future requirements has also been in focus. In this study, three different future electricity supply scenarios for Estonia in 2020 are considered and compared to the situation in 2002. They are based on domestic oil shale, imported natural gas, and imported nuclear power. According to the aims of the national energy policy, renewable energy sources were raised to 10% in all scenarios. Using the LCA methodology, the least damaging impact on the environment occurs in the ‘nuclear scenario’, with nuclear energy as the main energy source. The best scenario, however, depends on the weight or acceptance of accidental releases or other impacts not defined in this context. The ‘Oil shale scenario’ would be a slightly more damaging alternative than the ‘Natural gas scenario’ even if new technical solutions will remarkably improve the environmental performance of oil shale electricity production. Land use and waste disposal are crucial issues, particularly for oil shale and nuclear electricity production. However, the depletion of oil shale is not as critical an issue as the depletion of natural gas and uranium. According to the significance analysis of impact categories, climate change is the most significant impact on the environment in the scenarios. Future decisions on the development of the Estonian energy sector are most likely to be based on technological, economical and political aspects. Political aspects are likely to be the most significant. However, this type of study can give additional value to the discussion due to the increasing role of sustainability in energy issues.     

Analysis of fouling mechanisms and membrane cleaning during ultrafiltration of bee venom

ABSTRACT

The knowledge about permeate flux decline regarded to apitoxin can be a useful tool to allow industrial fractionation of the mixture. Hermia’s models were used to predict the fouling mechanisms during cross-flow ultrafiltration of bee venom in 10 kDa regenerated cellulose membrane. Three different apitoxin concentrations (0.2 to 1 g/L) were tested at 1 bar and 0.08 m/s. Fouling mechanisms varied as a function of feed content. Membrane cleaning with sodium dodecyl sulphate was effective. Phospholipase A₂ rejection coefficients were a function of membrane fouling, varying from 35 to 93%.     

Pilot‐scale development of core–shell polymer supports for the immobilization of recombinant lipase B from Candida antarctica and their application in the production of ethyl esters from residual fatty acids

A recombinant lipase B from Candida antarctica (LipB) in Pichia pastoris was synthesized through submerged fermentation using crude glycerin as substrate. The immobilization of this enzyme on the core–shell polymeric supports is an effective alternative for its application. The supports with distinct levels of hydrophobicity were produced through combined suspension and emulsion polymerization in pilot scale. Particles with distinct compositions were synthesized (PMMA/PMMA; PMMA‐co‐DVB/PMMA‐co‐DVB; and PS‐co‐DVB/PS‐co‐DVB) and employed on the immobilization of the produced lipase (LipB) and the commercial enzyme (CalB). The morphological properties (specific area, average pore diameter, specific volume of pores, and hydrophobicity level) and the influence of the polymerization conditions on the morphology of the supports were studied. The thermal stability of such biocatalysts was also investigated in the presence of calcium cation (Ca⁺²), maintained 100% of the activity after 3 h at 50°C when the PMMA‐co‐DVB/PMMA‐co‐DVB was employed. The synthesized enzyme and supports manufactured in pilot scale were employed successfully for production of esters using residual fatty acids as substrates, adding value to these raw materials and increasing the ranges of possible applications.     

On the Oxidation and Combustion of AlH3 a Potential Fuel for Rocket Propellants and Gas Generators

Aluminum hydride is a promising candidate for application in energetic materials and hydrogen storages. E.g. an AP/HTPB rocket propellant filled with alane was calculated for a 100 N s kg⁻¹ higher specific impulse compared to the same concentration of aluminum. Different investigations on α‐AlH₃ polyhedra using thermoanalytical methods and X‐ray diffraction were performed to receive a better understanding of dehydration at about 450 K, passivation of the remaining porous aluminum particles and further oxidation. A modeling approach to describe these conversions including diffusion processes, Avrami‐Erofeev mechanism and Arrhenius type reaction steps of n‐th order were introduced. Results were discussed in comparison to experimental investigations under pressure with model propellants on the base of gelled pure nitromethane and also filled with alane or pure aluminum in concentrations of 5%, 10% and 15%. Both alane and aluminum increase the burning rate on a factor of two correlated with a temperature increase up to 500 K and more. A mesa burning effect at 6 to 10 MPa was indicated by the mixtures with alane.     

Retinoprotective Effects of PACAP Eye Drops in Microbead-Induced Glaucoma Model in Rats

Glaucoma is associated with increased intraocular pressure (IOP), causing the apoptosis of retinal ganglion cells (RGCs) and the loss of their axons leading to blindness. Pituitary adenylate cyclase activating polypeptide (PACAP) is neuroprotective in several neural injuries, including retinopathies. The aim of this study was to investigate the effects of PACAP1-38 eye drops in a model of glaucoma. IOP was elevated bilaterally by injections of microbeads to block the aqueous humor outflow. The control groups received the same volume of saline. Animals were treated with PACAP1-38 (1 µg/drop, 3 × 1 drop/day) or vehicle for 4 weeks starting one day after the injections. Retinal morphology by histology and optical coherence tomography, function by electroretinography, and IOP changes were analyzed. Animals were sacrificed 8 weeks after the injections. Microbeads injections induced a significant increase in the IOP, while PACAP1-38 treatment lowered it to normal levels (~10 mmHg). Significant retinal degeneration and functional impairment were observed in the microbead-injected group without PACAP1-38 treatment. In the microbeads + PACAP1-38 group, the retinal morphology and functionality were close to the normal values. In summary, our results show that PACAP1-38, given in form of eye drops, is neuroprotective in glaucoma, providing the basis for potential future therapeutic administration.