Recycled car bumpers' impact resistance investigated by wide‐angle X‐ray diffraction

The recycled polyolefinic product from discarded standard car bumpers collected from Rio de Janeiro suburb shops was characterized by mechanical and wide‐angle X‐ray scattering (WAXS) methods. We found that the recycled plastic mixture is composed mainly of polypropylene (PP), containing ethylene‐propylene‐diene (EPDM) terpolymers and a minor proportion of high‐density polyethylene (HDPE), and is highly resistant to impact. The results were compared with the corresponding data obtained from binary and ternary blends of virgin PP, EPDM, and HDPE. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 999–1004, 2000     

An innovative electromagnetic compressive split Hopkinson bar

This paper proposes a new design for the compressive split Hopkinson bar that makes use of the intense pressure created in a transient magnetic field formed by the passage of a pulse of electric current through a series of coils. The proposed technology enables to characterize the behaviour of materials under high strain-rates with a small acceleration path length of the striker bar and, because propulsion is purely electromagnetic, the overall performance can be easily controlled and nearly infinitely adjustable. The presentation is focused on the design and fabrication of the mechanical, electrical and electromagnetic components of the new compressive split Hopkinson bar and includes results from stress–strain characterization at high strain-rates to demonstrate the validity of the proposed concept.     

Microstructure and texture assessment of Al–Mn–Fe–Si (3003) aluminum alloy produced by continuous and semicontinuous casting processes

Aluminum sheets are currently produced by the direct-chill process (DC). The need for low-cost aluminum sheets is a challenge for the development of new materials produced by the twin roll caster (TRC) process. It is expected that sheets produced from these different casting procedures will differ in their microstructure. These differences in microstructure and in the crystallographic texture have great impact on sheet mechanical properties and formability. The present study investigated microstructure and evaluated texture of two strips of Al–Mn-Fe–Si (3003) aluminum alloy produced by TRC and by hot-rolling processes. It was possible to notice that the microstructure, morphology, and grain size of the TRC sample were more homogenous than those found in hot-rolled samples. Both strips, obtained by the two processes, showed strong texture gradient across the thickness.     

Microalgae for biodiesel production and other applications: A review

Sustainable production of renewable energy is being hotly debated globally since it is increasingly understood that first generation biofuels, primarily produced from food crops and mostly oil seeds are limited in their ability to achieve targets for biofuel production, climate change mitigation and economic growth. These concerns have increased the interest in developing second generation biofuels produced from non-food feedstocks such as microalgae, which potentially offer greatest opportunities in the longer term. This paper reviews the current status of microalgae use for biodiesel production, including their cultivation, harvesting, and processing. The microalgae species most used for biodiesel production are presented and their main advantages described in comparison with other available biodiesel feedstocks. The various aspects associated with the design of microalgae production units are described, giving an overview of the current state of development of algae cultivation systems (photo-bioreactors and open ponds). Other potential applications and products from microalgae are also presented such as for biological sequestration of CO₂, wastewater treatment, in human health, as food additive, and for aquaculture.     

Filamentous bulking sludge--a critical review

This paper reviews the long-standing bulking sludge problem in activated sludge systems. Despite the extensive amount of research that has been done on bulking sludge, it still occurs world-wide and a comprehensive solution does not seem to be available. Bulking sludge can be approached as a microbiological problem (occurrence of a specific filamentous bacterium) or as an engineering problem (growth of bacteria with a filamentous morphology). In the first case species-specific solutions should be found, whereas in the latter case, a generic approach might be available. Since bulking sludge is caused by a group of bacteria with a specific morphology, but not a specific physiology we believe that a generic approach would be feasible. Several theories for bulking sludge are discussed. Based on these theories the application and associated problems with the use of biological selectors are critically evaluated. Finally, a set of open research questions is identified.     

Composite resins based on novel and highly reactive bisglycidyl methacrylate monomers

Three new bisglycidyl monomers; 1,4‐bis((2‐hydroxy‐3‐methacryloxypropoxy) methyl)benzene (MB‐Phe‐OH), 1,4‐bis(2‐hydroxy‐3‐methacryloxypropoxy)2‐cis‐butene (MB‐Cis‐OH), and 1,7‐bis(2‐hydroxy‐3‐methacryloxypropoxy)heptane (MB‐1,7‐OH); were synthesized and used as Bis‐GMA/TEGDMA (bisphenolglycidyl methacrylate/triethylene glycol dimethacrylate) composite resin additives. Flexural properties and double bond conversion of the dental resins composed of silanizated inorganic filler and organic matrices containing new monomers were evaluated. The composite resins formulated, using the monomers MB‐Cis‐OH and MB‐1,7‐OH, have mechanical properties and double bond conversion comparable with those of Bis‐GMA/TEGDMA composite resin used as control. The composite containing the new monomer MB‐Phe‐OH has better flexural properties (flexural strength 65.01 MPa and flexural modulus 5675.91 MPa) than the control composite resin (flexural strength 52.85 MPa and flexural modulus 4879.72 MPa); this could be attributed to the molecular structure of the monomer and its high double bond conversion level of 74.19%. The new bisglycidyl methacrylate monomer MB‐Phe‐OH could be potentially useful in the development of new organic matrices for dental composite resins with high double bond conversion and enhanced mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40971.     

Non-isothermal crystallization kinetics of thermotropic polyesters with flexible spacers in the main chain

The non-isothermal crystallization kinetics of two thermotropic polyesters with flexible spacers in the main chain were studied. The influence of the spacer type on the kinetics has been considered. The Ozawa theory for non-isothermal crystallization was used to analyse the differential scanning calorimetry data. The polyester with an oxyethylenic group as the flexible spacer followed the Ozawa equation and allowed the calculation of the Avrami exponent under non-isothermal conditions, but in the case of the polyester with methylenic groups as the flexible spacer the Ozawa theory is not valid.