1,720,986 research outputs found
Thermal behavior and structural study of SiO2/Poly(ε-caprolactone) hybrids synthesized via sol-gel method
No full textSiO2-based organic-inorganic hybrids (OIHs) are versatile materials whose properties may change significantly because of their thermal treatment. In fact, after their preparation at low temperature by the sol-gel method, they still have reactive silanol groups due to incomplete condensation reactions that can be removed by accelerating these processes upon heating them in controlled experimental conditions. In this study, the thermal behavior of pure SiO2 and four SiO2-based OIHs containing increasing amount (6, 12, 24 and 50 wt %) of poly(ε-caprolactone) (PCL) has been studied by simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC). The FTIR analysis of the gas mixture evolved at defined temperatures from the samples submitted to the TG experiments identified the mechanisms of thermally activated processes occurring upon heating. In particular, all samples already release ethanol at low temperature. Moreover, thermal degradation of PCL takes place in the richest-PCL sample, leading to 5-hexenoic acid, H2O, CO2, CO and ε-caprolactone. After the samples' treatment at 450, 600 and 1000 °C, the X-ray diffraction (XRD) spectra revealed that they were still amorphous, while the presence of cristobalite is found in the richest-PCL material. © 2018 by the authors
Identification and characterization of plastics from small appliances and kinetic analysis of their thermally activated pyrolysis
No full textThe first step consisted in a field investigation carried out in Waste Electric and Electronic Equipment (WEEE) treatment plants coupled with a bibliographic product analysis and FT-IR spectroscopy polymers identification. Three main polymers of the thermoplastic fraction of small appliances were identified: in the external cases it was possible to find acrylonitrile- butadiene-styrene (ABS) and high impact polystyrene (HIPS), while polybutadiene terephthalate (PBT) was contained in the printed circuit boards (PCBs). Taking into account this identification, a ternary polymer mixture of ABS-HIPS-PBT was prepared as a representative sample of the thermoplastic fraction contained in WEEE (real WEEE sample). From the thermal characterization (proximate and ultimate analysis, high heating value (HHV) direct measurement and Energy-Dispersive-X-Ray-Fluorescence analysis (ED-XRF)) the only polymer whose properties sensibly differ from the analogous virgin polymer is the one contained in PCBs. A kinetic analysis of pyrolysis occurring on the three components and on their ternary mixture was performed using a thermogravimetry (TG) apparatus in argon atmosphere under non isothermal conditions. Triplicates of TG experiments at four heating rates of 2, 5, 10 and 15 K min-1 were carried out and two different model-free approaches were adopted, namely the Kissinger and Ozawa-Flynn-Wall methods in order to determine the activation energy E (as a single mean value or as a function of the degree of conversion α). The conversion dependencies of both activation energy and pre-exponential factors were determined as well as the reaction model, representing the reaction mechanism. The suitability of the models selected was tested using the Akaike's Information Criteria (AIC) score, being the geometric model R3 the best found for pyrolysis of ABS, HIPS and real WEEE samples, while PBT sample showed an uncertainty between the R3 and the diffusion D2 model. The reaction time values to achieve the maximum pyrolysis rate in the three main components and in the real WEEE sample were also calculated. © 2014 Elsevier Ltd. All rights reserved
Characterization of the residue of a commingled post-consumer plastic waste treatment plant: a thermal, spectroscopic and pyrolysis kinetic study
No full textA plastic packaging residue provided by a central Italy recycling facility was the subject of study of the present paper. The aim is to propose the valorization of plastic film residue (PFR) through a pyrolysis process. The PFR was thermo-chemically characterized through heating value, proximate and ultimate analysis. Fourier transformed infrared measurements have shown that PFR is constituted by 92–95 mass% of polyethylene (PE) film, around 5 mass% of PP, polystyrene (PS) < 1 mass%, PET < 1 mass% and traces of foreign materials. The extremely high percentage (98.7 mass%) of volatile matter and the low content of ash (2.1 mass%), humidity (0.6 mass%) and chlorine (0.1 mass%) make PFR an optimum candidate as load of a pyrolytic reactor. Thermogravimetry (TG) experiments were carried out at five different heating rates (2, 5, 7, 10, 12 K min−1) to determine the kinetic parameters of pyrolysis (activation energy E, pre-exponential factor A and the reaction model). No significant variation of activation energy, calculated by an integral isoconversional method proposed by Vyazovkin, is observed with increasing the degree of conversion. An average value of 264 ± 5 kJ mol−1 was estimated. Then, the Coats–Redfern method and the compensation effect were used to determine the lnA versus α data (being 41.9 the average value within the 0.25 < α < 0.85 range) and the reaction mechanism (R2 contracting cylinder model). Furthermore, the minimum energy required to pyrolyze 1 kg of PFR, about 2.27 MJ, was estimated by differential scanning calorimetry. It corresponds to about 5.5% of the exploitable energy of the input material
Plastic waste recycling in additive manufacturing: Recovery of polypropylene from WEEE for the production of 3D printing filaments
Full text linkThe inefficient management of wastes recovered from electric and electronic apparatuses (the so-called WEEE or e-waste) has become a severe global concern in the last years, since the indiscriminate accumulation of wastes containing hazardous material poses serious risks for the environmental, as well as for the human health. Despite the continuous development of innovative and efficient technologies for the mechanical recycling of WEEE plastics, the effective re-utilization of these fractions is often limited by their poor value-added. In this work, we propose a strategy for the valorization of a typical WEEE plastic stream recovered from small appliances (mainly composed on polypropylene filled with talc particles) through the formulation of filaments suitable for Fused Filament Fabrication (FFF) 3D printing processes. Preliminary spectroscopic analyses on the WEEE plastics allowed separating the sample in two streams, according to the different content of talc. Both streams were first characterized from a rheological point of view, aiming at assessing their 3D printability. Then, the mechanical properties and the morphology of the filaments (obtained after a close optimization of the extrusion conditions) were evaluated; the obtained results indicated the achievement of a regular geometry and mechanical properties comparable to those of commercial filaments. Finally, 3D printed specimens showed a satisfactory quality in terms of resolution and definition, demonstrating the possibility of profitably enhancing the value-added of WEEE plastics, using them as feedstock to produce sustainable 3D printing filaments
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Optimization of Pyrolysis Parameters by Design of Experiment for the Production of Biochar from Sewage Sludge
Full text linkSewage sludge management is a key concern in today’s world. Improper disposal can lead to various environmental issues including air, water and soil pollution. Among the available technologies, thermal treatments, particularly pyrolysis, are gaining interest for their ability to reduce sewage sludge volume and to recover materials and energy from it. This study explored the influence of some relevant parameters in the thermal pyrolysis process. The design of experiment, named central composite design, was accounted to optimize temperature, heating rate and residence time in order to maximize the biochar yield and its CO2 adsorption capacity. A two-factor interaction model provided a satisfactory interpretation of the results. Within the studied ranges, maximum values of 47.8 wt% and 0.514 mol CO2/kg were obtained for the yield and CO2 adsorption capacity, respectively. Two significant experiments were repeated in a different pyrolysis system highlighting how other factors (e.g., reactor geometry, granulometry, etc.) can influence the quantity and the quality of produced biochar. The biochar obtained under the best pyrolysis conditions was characterized by a surface area of 124 m2/g and an ash content of 61 wt%. Lastly, the theoretical energy balance showed that the drying process is the main energy-intensive step in the pyrolysis of sewage sludge
Thermal and catalytic pyrolysis of a synthetic mixture representative of packaging plastics residue
No full textA synthetic mixture of real waste packaging plastics representative of the residue from a material recovery facility (plasmix) was submitted to thermal and catalytic pyrolysis. Preliminary thermogravimetry experiments coupled with Fourier transform infrared spectroscopy were performed to evaluate the effects of the catalysts on the polymers’ degradation temperatures and to determine the main compounds produced during pyrolysis. The thermal and catalytic experiments were conducted at 370°C, 450°C and 650°C using a bench scale reactor. The oil, gas, and char yields were analyzed and the compositions of the reaction products were compared. The primary aim of this study was to understand the effects of zeolitic hydrogen ultra stable zeolite Y (HUSY) and hydrogen zeolite socony mobil-5 (HZSM5) catalysts with high silica content on the pyrolysis process and the products’ quality. Thermogravimetry showed that HUSY significantly reduces the degradation temperature of all the polymers—particularly the polyolefines. HZSM5 had a significant effect on the degradation of polyethylene due to its smaller pore size. Mass balance showed that oil is always the main product of pyrolysis, regardless of the process conditions. However, all pyrolysis runs performed at 370°C were incomplete. The use of either zeolites resulted in a decrease in the heavy oil fraction and the prevention of wax formation. HUSY has the best performance in terms of the total monoaromatic yield (29 wt-% at 450°C), while HZSM5 promoted the production of gases (41 wt-% at 650°C). Plasmix is a potential input material for pyrolysis that is positively affected by the presence of the two tested zeolites. A more effective separation of polyethylene terephthalate during the selection process could lead to higher quality pyrolysis products. [Figure not available: see fulltext.]
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Thermal pyrolysis of a real plastic sample from small WEEE and characterization of the produced oil in view of fuel or feedstock uses
No full textThe possibilities of valorizing by pyrolysis a plastic fraction from small waste from electrical and electronic equipment (WEEE-R4) rejected by a material recovery facility have been assessed. The characterization revealed that WEEE-R4 was mainly composed of acrylonitrile–butadiene–styrene (ABS) and blends of polycarbonate (PC)-ABS (75 and 25 wt%, respectively) and had good physicochemical properties as feed for pyrolysis processes: high values for volatile matter (95 wt%) and low heating value (LHV, 35 MJ/kg) and low ash and moisture content (2.5 and 0.33 wt%, respectively). On the contrary, the high content of heteroatoms, in particular Br from brominated flame retardants, arose as source of concern. Thermal analysis coupled with evolved gas Fourier transform Infrared (FTIR) spectroscopy showed that WEEE-R4 degraded in two steps in the range 310–460 °C and mainly to the monoaromatic compounds phenol and styrene. Thermal pyrolysis at 400 °C was carried out in a bench-scale reactor and the yields of the products were 18 wt% solids, 58 wt% light oil, 16 wt% tar and 8 wt% gas. The gaseous fraction was composed mainly of CO2 (60 wt%), originating from the thermal degradation of PC. After removing CO2, the gas had a good LHV (32.5 MJ/kg) such to contribute for the 66 % to the energy required for the pyrolysis process of WEEE-R4. The properties of the light oil were evaluated by means of the same standard tests used for commercial fuels or crude oils. The results were interesting but far from the more refined gasoline and diesel oil, with the concentration of nitrogen and bromine even higher than the typical composition of petroleum. Nevertheless, this study shows that pyrolysis followed by a refining treatment such as, distillation is capable of producing monoaromatic hydrocarbon in significant amount (>30 wt%)
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