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

Impact sound of timber floors in sustainable buildings

Timber buildings represent a robust alternative to traditional heavyweight constructions. They allow CO2 storage, high structure and performance reproducibility, fast assembly and final certification of every panel. Nowadays, acoustic insulation is one of the most requested performances on the part of inhabitants, but not always fulfilled. Since these kind of edifices are relatively new in the market, there are very few studies on acoustic properties, regarding on impact sound performances. In this paper, an in-depth analysis of impact noise on bare timber floors is presented, focusing on how impact sound reduction cannot be as efficient as in heavyweight constructions. Two new equations are proposed, modelling the impact sound pressure level of common bare timber structures and the influence of traditional floating floor systems is analysed

Innovative thermal and acoustic insulation foam from recycled waste glass powder

An innovative powder-foaming process able to produce thermal and acoustic insulating foams obtained by sol-gel and a subsequent freeze-drying process was developed. Gel containing glass powder was formed using alginate, a polysaccharide composed of 1-4linked \u3b1-L-guluronic acid and \u3b2-D-mannuronic acid, capable to form stable gels in presence of calcium cations. In order to obtain a porous foam, gels were frozen and then freeze-dried. Foam properties strongly depend on production parameters, particle dimension and different binder concentrations, their influence was investigated. The resulting glass foams were characterized in order to evaluate structure, density, mechanical and acoustic properties. The results pointed out an improved acoustic insulating performance respect to rock wool. Foams were also subjected to a thermal process to better fix powders into the final glass structure

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

Sviluppo e sintesi di nanoparticelle funzionalizzate per bio-analisi attraverso la spettroscopia SERS

2011/2012The objective of this doctoral research is the development and the implementation of SERS-active substrates with biological samples. The substrates consist in coated silver nanoparticles synthesized by chemical reduction of a silver salt. The biological samples are the anionic chromophore bilirubin and two heme protein, the cationic cytochrome-c and the anionic protein cytochrome b5. In the first part of this work, positively charged nanoparticles were prepared by coating citrate-reduced silver nanoparticles with the cationic polymer poly-L-lysine and were employed with bilirubin in the experiments listed below: detection of nanomolar bilirubin concentrations in aqueous solutions, showing that the SERS intensity increases linearly with concentration in a range from 10 nM to 200 nM, allowing quantitative analysis of bilirubin aqueous solutions. indirect quantification of bilirubin cellular up-take, demonstrating the ability to detect the bilirubin also in a buffer solution suitable for cell growth with pH 7.4. Since the bilirubin quantification at this pH is no longer possible, the poly-L-lysine was substituted by two polymers with a quaternary nitrogen atom. bilirubin measurement in serum, but TEM images highlights the formation of a albumin layer around the nanoparticles, blocking the interaction between bilirubin and the nanoparticles. Hence the citrate-reduced silver nanoparticles were coated with an hydrophobic capping and re-dispersed in hexane, to avoid the albumin layer around the nanoparticles. In the second part of this doctoral thesis, silver nanoparticles were prepared via seed growth method and subsequently coated with chitosan or silica in order to obtain positively or negatively charged nanoparticles respectively. Such substrates enhance the spectrum of the cytochrome-c and cytochrome-b5 on polished silver electrode without directly interact with the protein. Thanks to the presence of chitosan or silica coated nanoparticles, the cytochrome-c and cytochrome-b5 can be detected on a gold substrate.L’obiettivo di questo dottorato è lo sviluppo e l’implementazione di substrati SERS attivi con campioni biologici. Nanoparticelle di argento ricoperte sono state scelte come substrati. I campioni biologici analizzati sono la bilirubina e due proteine eme, il citocromo-c (cationico) e il citocromo-b5 (anionico). Nella prima parte di questo lavoro le nanoparticelle di argento sono state preparate usando come agente riducente il citrato e successivamente sono state ricoperte con un polimero cationico, la poli-lisina. Le nanoparticelle cariche positivamente così ottenute sono state impiegate con la bilirubina nei seguenti esperimenti: rilevazione di concentrazioni nano-molari di bilirubina in soluzioni acquose, dimostrando che per concentrazioni comprese tra 10 e 200 nM, l’intensità degli spettri SERS aumenta linearmente con la concentrazione. È quindi possibile l’analisi quantitativa di bilirubina in soluzioni acquose. quantificazione indiretta dell’assorbimento cellulare di bilirubina, documentando la possibilità di rilevare la bilirubina in una soluzione tampone che permetta la crescita cellulare a pH 7.4. Dal momento che la quantificazione della bilirubina in questa soluzione buffer non è più possibile, la poli-lisina è stata sostituita con due polimeri che presentano un azoto quaternario. misura della bilirubina nel siero, ma le immagini TEM evidenziano la formazione intorno alle nanoparticelle di uno strato di albumina, che impedisce l’interazione della bilirubina con le nanoparticelle ricoperte di poli-lisina. Per evitare la formazione dello strato di albumina, le nanoparticelle di argento sono state quindi ricoperte con un capping idrofobico e ridisperse in esano. Nella seconda parte di questa tesi di dottorato, le nanoparticelle di argento sono state preparate a partire da nanoparticelle di qualche nanometro e successivamente ricoperte con chitosano o silice. Lo spettro del citocromo-c e del citocromo-b5 sono stati amplificati grazie alla presenza di queste nanoparticelle senza interagire direttamente con le proteine. Grazie alla presenza delle nanoparticelle ricoperte di chitosano o silice, il citocromo-c e il citocromo-b5 sono stati misurati su un substrato d’oro.XXV Ciclo198

Failure investigation of a protective epoxy coating by means of crosscheck between infrared spectroscopy and thermal analysis

This paper reports the failure of an epoxy coating that was applied for corrosion prevention on the inner walls of a heat exchanger. The coating became brittle and detached from the walls of the exchanger after one year of service. An investigation was performed in order to evaluate the failure cause by means of thermal analysis, optical microscopy and infrared spectroscopy. Thermal analysis excluded an incomplete curing of the detached paint. Optical microscopy highlighted sediments, pores and cracks over the detached coating surface; infrared spectroscopy revealed vibrational bands associated with thermo-oxidative phenomena. A thermo-oxidative simulation was performed on fresh coating samples, pointing out that epoxy coating starts degrading around 100-120 \ub0C. Taking into account the temporary malfunction of the cooling system reported by the user, the failure cause was identified in an overheating that induced a thermo-oxidative degradation of the coating and its subsequent embrittlement and detachment

Life cycle analysis of a novel thermal insulator obtained from recycled glass waste

This paper focused on the application of the Life Cycle Analysis methodology to a novel thermal insulator by means of comparison with traditional materials widely used in the building sector. This innovative insulating foam was produced from recycled glass powder and green-chemistry reagents via a freeze-drying process. The materials inventory for this insulator was built from primary laboratory data, while energy flows were estimated according to available secondary sources. Materials inventory, energy flow and emission data for traditional insulators were obtained and averaged from literature and relevant environmental product declarations. Global warming, acidification, eutrophication and abiotic resource depletion potentials were evaluated as environmental impact factors to assess the environmental performances of the innovative insulator respect to the available materials. The benefits of the novel material in terms of these indexes were then highlighted taking into account also different local energetic sources

Surface-enhanced Raman effect in hybrid metal\u2013semiconductor nanoparticle assemblies

Hybrid metal\u2013semiconductor nanoparticles consisting of silver nanoparticle cores (AgNPs) coated with a layer of CdSe quantum dots (QDs) have been studied by Raman spectroscopy. The hybrid nanoparticles were prepared via electrostatic interaction by mixing aqueous suspensions of QDs and AgNPs, where opposite charges on the AgNPs and QDs surfaces were induced by opportunely selected capping agents. Assemblies of such hybrid nanoparticles show an increased intensity of the Raman spectrum of up to 500 times, when compared to that of the sole QDs. This enhancement is attributed to the SERS effect (Surface-enhanced Raman scattering). Such enhancement of the Raman modes suggests several opportunities for further research, both in imaging and sensing applications

Time-depending performance of resilient layers under floating floors

In the floating floor system the performance of resilient layers, in terms of impact sound pressure level reduction, is of paramount importance. In the present study in order to evaluate the time-depending performances, a comprehensive characterization of twenty different layers was carried out, evaluating dynamic stiffness, compressibility and compressive creep. The aim of this work was to find out a possible correlation among these parameters and the effect of service time on mechanical and acoustical properties. Results indicated that a general rule couldn\u2019t be defined. Furthermore, the presence of a coating, as well as different density and/or contact shape, has proved to influence the final acoustical performances