Qualitative and quantitative contaminants assessment in recycled pellets from post-consumer plastic waste by means of spectroscopic and thermal characterization

The complexity of any plastic recycling initiative lies in the heterogeneous nature of the post-consumer commingled plastic waste stream: recycling treatments are challenging without prior reliable sorting. A suitable identification system should be able to recognize different plastics and blends. Nowadays, the main technique used as quality control in plastic waste sorting centers is differential scanning calorimetry, whose result can be purely qualitative or semi-quantitative, since only the crystalline fraction is evaluated. Moreover, the time required for data acquisition is relatively long. Infrared spectroscopy is an alternative, faster technique extensively used in applied research, but not widely utilized in industry. In this work, the cross-use of infrared spectroscopy and calorimetry is tested in a real, practical case: the quality control of recycled pellets (namely composed of polyolefins only), which represent the output of a commingled plastic recycling plant and are used as secondary raw materials for different applications. Appropriate infrared spectroscopy calibration curves were built to allow the quantitative analysis with respect to the most common polymers found in the commingled plastic waste stream; the composition and contaminants in the recycled pellets were thereby determined and tracked through different production batches through the cross-use of the two techniques outlined above

Ant-nest corrosion failure of heat exchangers copper pipes

This paper reports on the failure analysis carried out on leaking copper pipes from three different air conditioning systems. Pinhole leaks originating from localized corrosion morphology were reported. Microscopic interconnecting tunnels inside the pipe section were observed; these tunnels were filled with corrosion products. Experimental findings and similarity to previously reported cases pointed out a corrosion mechanism known as \u201cant-nest corrosion\u201d as failure cause. This type of corrosion could develop in heat exchanger components stored after assembly, during leakage tests or in the initial operational stages. It was shown that an ant-nest corrosion attack could start due to different reasons and propagate in different ways (from the inside or from the outside of the tube). In the first examined case, it was supposed that the hydrolysis of a halocarbon gas circulating in the pipe was the triggering cause of the corrosion event; in the other cases, we ascribed the starting corrosion event to the presence of residual organic contaminants on the external pipe surface

Characterization of Large Microplastic Debris in Beach Sediments in the Po Delta Area

The use of single-use or disposable plastic objects has massively increased during the last few decades, and plastic has become the main type of litter found in marine environments. The Adriatic Sea is seriously prone to marine litter pollution, and it collects about one-third of all the freshwater flowing into the Mediterranean, mainly via the river Po. This study investigated the type and composition of large microplastic debris collected in different sites in the Po Delta area. Visual classification was performed by relevant criteria, while chemical composition was assessed by infrared spectroscopy. The main plastic fraction is composed of polyolefin (76%), followed by polystyrene (19%). This proportion roughly matches global plastic production, rescaled after excluding plastics with negative buoyancy: all the identified compounds have a specific gravity lower than that of the seawater. Fragments (irregularly shaped debris) represent the most abundant category fraction (85%), followed by pellets, which represent roughly 10% of the total. Overall, the results provided an insight into large microplastic pollution in beach sediments in the Po delta area

A sustainable acoustic customization of open porous materials using recycled plastics

Foams are commonly used as sound absorbers and thermal insulators for many industrial and construction applications. The insulating materials market is currently dominated by inorganic fibres like glass and mineral wool, as well as plastic foams. However, worldwide plastics consumption produces huge amounts of waste, generating concerns about soil, air and especially seawater pollution. Hence, new methods for recycling marine microplastic litter according to cleaner production criteria are being sought. This paper presents a novel, sustainable and eco-friendly foamy material made of microplastic waste, namely polyethylene terephthalate (PET) and polystyrene (PS), incorporated into a bio-based matrix. Samples with different compositions were prepared and then characterized for sound absorption properties. Evidence is presented of very good acoustic performances and of how the acoustic characteristics of the end product can be customized using different microplastic content and type. This allows envisioning many industrial and civil applications for this novel open-cell material

A home-made system for IPCE measurement of standard and dye-sensitized solar cells

A home-made system for incident photon-to-electron conversion efficiency (IPCE) characterization, based on a double-beam UV-Vis spectrophotometer, has been set up. In addition to its low cost (compared to the commercially available apparatuses), the double-beam configuration gives the advantage to measure, autonomously and with no need for supplementary equipment, the lamp power in real time, compensating possible variations of the spectral emission intensity and quality, thus reducing measurement times. To manage the optical and electronic components of the system, a custom software has been developed. Validations carried out on a common silicon-based photodiode and on a dye-sensitized solar cell confirm the possibility to adopt this system for determining the IPCE of solar cells, including dye-sensitized ones

Effect of basalt fibre hybridisation and sizing removal on mechanical and thermal properties of hemp fibre reinforced HDPE composites

Despite the advantages offered by natural fibre-based thermoplastic composites in terms of environmental impact and cost, their mechanical performance is generally lower than that of synthetic counterparts. Hybridisation with mineral fibres (basalt) can broaden the industrial applications of natural fibre reinforced composites. The present study focused on the performance of injection-moulded short basalt fibre, hemp fibre and hemp/basalt fibre hybrid high density polyethylene (HDPE) composites. Effects of a maleated coupling agent on the thermal and mechanical properties of the resulting composites were evaluated as a function of the fibre mass fraction. Hybridisation of hemp fibres with basalt fibres was found to significantly increase the mechanical properties and the crystallinity of hemp-fibre reinforced composites thus suggesting that short hemp/basalt fibre hybrid HDPE composites are promising candidates for semi-structural applications. Additionally, a sizing removal procedure mimicking the conditions experienced in an end-of-life composite thermal recycling process was defined and discussed in terms of residual mechanical properties of basalt/HDPE composite

The effect of artificial weathering on PP coextruded tape and laminate

The aim of this work was to analyse the influence of artificial weathering on polypropylene (PP) selfreinforced composite both as fabric constituent (tape) and as laminate. Particular attention has been focused on the interaction between radiation and material microstructural characteristics, especially for the selective action that the former causes in PP amorphous regions. The evaluation of carbonyl index performed by Fourier Transform Infrared (FT-IR) spectroscopy has highlighted that tapes are more prone to degradation since their drawn structure induces internal stress. Differential scanning calorimetry (DSC) measurements have denoted a shift towards lower temperature of PP melting peak. While crystallinity determination performed by DSC and FT-IR spectroscopy has underlined an increasing trend for laminate over exposure time due to the higher amount of amorphous phase, Raman spectroscopy has revealed that photo-degradation induces a rise of the isomeric defect fraction, limiting chemicrystallisation both for tapes and laminates

Influence of substrate on molecular order for self-assembled adlayers of CoPc and FePc

Self-assembled metal phthalocyanine thin films are receiving considerable interest due to their potential technological applications. In this study, we present a comprehensive study of CoPc and FePc thin films of about 50 nm thickness on technologically relevant substrates such as SiOx/Si, indium tin oxide (ITO) and polycrystalline gold in order to investigate the substrate induced effects on molecular stacking and crystal structure. Raman spectroscopic analysis reveals lower intensity for the vibrational bands corresponding to phthalocyanine macrocycle for the CoPc and FePc thin films grown on ITO as compared to SiOx/Si due to the higher order of phthalocyanine molecules on SiOx/Si. Atomic force microscopy analysis displays higher grain size for FePc and CoPc thin films on ITO as compared to SiOx/Si and polycrystalline gold indicating towards the influence of molecule\u2013substrate interactions on the molecular stacking. Grazing incidence X-ray diffraction reciprocal space maps reveal that FePc and CoPc molecules adopt a combination of herringbone and brickstone arrangement on SiOx/Si and polycrystalline gold substrate, which can have significant implications on the optoelectronic properties of the films due to unique molecular stacking

X-ray photoelectron spectroscopy analysis as a tool to assess factors influencing magnetic anisotropy type in Co/MgO system with gold interlayer

X-ray photoelectron spectroscopy (XPS) studies of Au/Co/Au(0.3 nm)/MgO and Au/Co/MgO systems were conducted in order to monitor the electronic structure modification at Co/MgO interface with/without gold interlayer. A detailed analysis of Co 2p states revealed that the amount of minor oxygen contribution at Co/MgO interface decreased after the Au interlayer was added. The obtained XPS results together with density functional theory (DFT) allowed explanation of the increase of surface anisotropy energy in the sample with the gold interlayer in terms of (i) noble and transitional metal d-d orbital hybridization; (ii) interfacial Co 3d and O 2p; and (iii) interface imperfectio

Transparent carbon nanotubes promote the outgrowth of enthorino-dentate projections in lesioned organ slice cultures

The increasing engineering of carbon-based nanomaterials as components of neuro-regenerative interfaces is motivated by their dimensional compatibility with subcellular compartments of excitable cells, such as axons and synapses. In neuroscience applications, carbon nanotubes (CNTs) have been used to improve electronic device performance by exploiting their physical properties. Besides, when manufactured to interface neuronal networks formation in vitro, CNT carpets have shown their unique ability to potentiate synaptic networks formation and function. Due to the low optical transparency of CNTs films, further developments of these materials in neural prosthesis fabrication or in implementing interfacing devices to be paired with in vivo imaging or in vitro optogenetic approaches are currently limited. In the present work, we exploit a new method to fabricate CNTs by growing them on a fused silica surface, which results in a transparent CNT-based substrate (tCNTs). We show that tCNTs favour dissociated primary neurons network formation and function, an effect comparable to the one observed for their dark counterparts. We further adopt tCNTs to support the growth of intact or lesioned Entorhinal-Hippocampal Complex organotypic cultures (EHCs). Through immunocytochemistry and electrophysiological field potential recordings, we show here that tCNTs platforms are suitable substrates for the growth of EHCs and we unmask their ability to significantly increase the signal synchronization and fibre sprouting between the cortex and the hippocampus with respect to Controls. tCNTs transparency and ability to enhance recovery of lesioned brain cultures, make them optimal candidates to implement implantable devices in regenerative medicine and tissue engineering. This article is protected by copyright. All rights reserved