Industrial paper recycling process. Suitable micronization for additive polymer application

The traditional paper recycling process has problems related to the disposal of sludge and waste, the use of incinerators and water treatment. Because of that, an interesting alternative proposed from dep. of chemical and materials engineering of Sapienza University of Rome to Carlucci industrial typography, is using paper as filler in thermoplastics or recycled thermoplastic matrix composite. In this way it’s possible re-use paper, but it also possible reduces the amount of polymer with equal volume. The paper has to be subjected by grinding. The chosen grinding process is fundamental to obtain a suitable product for composite. After a pre-grinding process obtaining 5-10 mm of paper fragments, the charge have to be subjected to a micronization process. In this study are selected two different type of micronization: the superfine grinding mill SF, a micronization process based on system that uses simultaneously the impact and friction action, and a knife mill that uses instead the cutting and friction action. Thanks to the first process, it is possible obtaining fibres with diameters of about 15-20 microns and lengths of the order of 250-500micron: a product therefore suitable for the application of filler in composites. This process unfortunately causes the production of fluff, as will shown in figure 2, because of the interfibrillar bonds between the fibers: an optimal dispersion of the fibers is necessary to avoid agglomerates which would decrease the composite properties. From the second process it is possible to obtain both fiber than particles as illustrated in figure 3. This morphologies mix allows to achieve a higher fluency preventing agglomerates. The turbomixer equipment realizes the production process of the composite, this process allows to introduce a higher percentage of filler respect the traditional injection moulding technique. The resulting composite is subjected by a morphological and mechanical characterization: look at the SEM analysis of the fracture surface, the fiber-matrix interface is weak, in spite of this, however, from the tensile test there is a constant elastic modulus and in some cases growing respect to the matrix devoid of fibres. From these results, the importance of optimize the grinding and micronization processes is clear and there is the opportunity of additives introduction to improve fiber-matrix interface

Dual morphology (fibres and particles) cellulosic filler for WPC materials

Wood-plastic composites (WPC) were fabricated by using a polyethylene (PE) matrix and filling it with wood flour in the amount of 30 wt.%, and compared with the same composites with further amount of 10 wt.% of cellulosic recycled fibres added. The materials were produced by turbomixing and subsequent moulding under pressure. Mechanical properties of both WPC and WPC with cellulosic recycled fibres were evaluated through mechanical and physical-chemical tests. Tensile tests clarified that a moderate reduction is strength is observed with the bare introduction of wood flour with respect to the neat PE matrix, whilst some recovery is offered by the addition of recycled cellulose fibres. Even more promisingly, the elastic modulus of PE matrix is substantially improved by the addition of wood flour (around 8% on average) and much more so with the further addition of recycled cellulose (around 20% on average). The fracture surfaces from the tensile test were analysed by scanning electron microscope (SEM) indicating a reduction in microporosity as an effect of added cellulose. The water absorption test and the hardness measure (Shore D) were also performed. SEM analysis underlined the weak interface between both wood particle and cellulosic recycled fibres and matrix. The water absorption test showed a higher mass variation for pure WPC than WPC with cellulosic recycled fibres. The hardness measurement showed that the presence of cellulosic recycled fibres improves both superficial hardness of the composite and temperature resistance. © 2016 Author(s)

Dense and cellular zirconia produced by gel casting with agar: preparation and high temperature characterization

A modified gel-casting process was developed to produce both dense and highly porous (40% volume) yttria tetragonal zirconia polycrystal (Y-TZP) using agar, a natural polysaccharide, as gelling agent. A fugitive phase, made of commercial polyethylene spheres, was added to the ceramic suspension before gelling to produce cellular ceramic structures. The characterization of the microstructural features of both dense and cellular ceramics was carried out by FEG SEM analysis of cross-sections produced by focused ion beam. The mechanical properties of the components were characterized at room temperature by nanoindentation tests in continuous stiffness measurement mode, by investigating the direct effect of the presence of residual microporosity. The presence of a diffuse residual microporosity from incomplete gel deaeration resulted in a decay of the bending strength and of the elastic modulus. The mechanical behavior of both dense and cellular zirconia (in terms of elastic modulus, flexural strength, and deformation at rupture) was investigated by performing four-point bending tests at the temperature of 1500°C

Effect of different lignocellulosic fibres on poly(ε-caprolactone)-based composites for potential applications in orthotics

This work compares the mechanical and thermal behaviour of fully biodegradable biocomposites based on polycaprolactone reinforced with three different natural fibres, namely hemp, sisal and coir, for potential applications in the field of orthoses. The same properties were further compared to those of two commercially available materials commonly used in the same prospective field. The results confirmed that the addition of natural fibres, irrespective of the origin of the fibres (leaf, bast or fruit) to a biodegradable matrix allows for significant improvement of the mechanical behaviour of the ensuing composites compared to traditional thermoplastic materials used in orthotics

Carbon-Fiber-Recycling Strategies: A Secondary Waste Stream Used for PA6,6 Thermoplastic Composite Applications

With a view to achieving sustainable development and a circular economy, this work focused on the possibility to valorize a secondary waste stream of recycled carbon fiber (rCF) to produce a 3D printing usable material with a PA6,6 polymer matrix. The reinforcing fibers implemented in the research are the result of a double-recovery action: starting with pyrolysis, long fibers are obtained, which are used to produce non-woven fabrics, and subsequently, fiber agglomerate wastes obtained from this last process are ground in a ball mill. The effect of different amounts of reinforcement at 5% and 10% by weight on the mechanical properties of 3D-printed thermoplastic composites was investigated. Although the recycled fraction was successfully integrated in the production of filaments for 3D printing and therefore in the production of specimens via the fused deposition modeling technique, the results showed that fibers did not improve the mechanical properties as expected, due to an unsuitable average size distribution and the presence of a predominant dusty fraction ascribed to the non-optimized ball milling process. PA6,6 + 10 wt.% rCF composites exhibited a tensile strength of 59.53 MPa and a tensile modulus of 2.24 GPa, which correspond to an improvement in mechanical behavior of 5% and 21% compared to the neat PA6,6 specimens, respectively. The printed composite specimens loaded with the lowest content of rCF provided the greatest improvement in strength (+9% over the neat sample). Next, a prediction of the "optimum" critical length of carbon fibers was proposed that could be used for future optimization of recycled fiber processing

Environmental effects on the mechanical behaviour of pultruded jute/glass fibre-reinforced polyester hybrid composites

The environmental degradation of the mechanical properties of pultruded jute and jute/glass hybrid reinforced polyester composites with high fibre volume fraction (0.70) has been investigated with special focus on the effects of water ageing and moderate temperature (up to 80 C). Water absorption tests were conducted by immersing specimens in distilled water at room temperature until saturation (4076 h). Water absorption curves and characteristic parameters such as coefficient of diffusion and equilibrium moisture content were determined. The composites exhibited a deviation from the Fickian behaviour with a positive role played by the addition of glass fibres in terms of moisture resistance. The influence of water uptake on tensile and flexural properties of composites was evaluated and a significant reduction in both strength and modulus was observed, with a superior strength retention offered by hybrid composites. Acoustic emission (AE) and scanning electron microscopy enabled to identify the weakening of fibre! matrix interface induced by water ageing. The effects of temperature were mitigated by glass fibres if compared with the higher degradation experienced by jute fibres. (C) 2014 Elsevier Ltd. All rights reserved

Plasma sprayed composite coatings obtained by liquid injection of secondary phases

A secondary suspension injection system was designed, manufactured and tested, with the aim of depositing composite coatings formed by a conventional air plasma sprayed matrix embedding heat-sensitive phases sprayed and protected in a liquid suspension flow. The system is composed of two main sections: a pressurized vessel, equipped with regulation and recirculation sub-systems, and an adjustable nozzle holder. Preliminary experimental activities were performed with an alumina/graphite system and focused on the evaluation of the effect of the main SSIS parameters on the amount of retained lubricating phase in the deposits on deposition efficiency and coating microstructure. Alumina powders were fed in the plasma plume by a conventional injection system (argon carrier gas) whereas graphite powder was injected by SSIS from a water-based slurry. A CFD (Computational Fluid Dynamics) software, originally developed for the simulation of plasma spray processes, was implemented in order to confirm the possibility of predicting the effect of the variation of operating parameters on the amount of surviving heat-sensitive phases, potentially embedded in the ceramic matrix. Deposited composite coatings were characterized in terms of thickness, graphite content, phase distribution and tribological properties. (C) 2008 Elsevier B.V. All rights reserved

Rivestimenti multistrato termospruzzati metalloceramici per barriere termiche di nuova concezione

Nel presente lavoro vengono esposti i risultati relativi alle prime fasi di progettazione, realizzazione e test di una nuova tipologia di barriera termica costituita da rivestimenti multistrato metallo-ceramici ottenuti per termodeposizione al plasma. Scopo dell’attività di ricerca è stato quello di caratterizzare i materiali utilizzati nel sistema multistrato sia da un punto di vista termo-meccanico che termo-fisico, di modellizzare il comportamento della barriera termica con l’analisi agli elementi finiti, e infine di valutare le effettive proprietà del sistema per mezzo di prove di esposizione ad elevati flussi termici. I materiali che compongono i vari strati del rivestimento (ZrB2-SiC, Mo, ZrO2- Y2O3), sono stati testati individualmente per mezzo di prove di flessione a 4 punti e di misure di coefficiente di dilatazione termica così da valutarne le proprietà termomeccaniche a temperatura ambiente e fino a 1500 °C. Inoltre, utilizzando la tecnica laser-flash, sono state studiate le proprietà termo-fisiche (diffusività e conducibilità termica) dei materiali oggetto della sperimentazione sia a temperatura ambiente che ad elevata temperatura. I risultati ottenuti sono stati utilizzati per l’implementazione di appositi modelli agli elementi finiti del sistema (substrato - rivestimento multistrato) con l’obiettivo di ottimizzare spessori e numero di strati e quindi di valutare e minimizzare gli stress termo-meccanici indotti dai carichi termici applicati. Infine sono state condotte prove preliminari di esposizione sul rivestimento multistrato per valutarne la resistenza ai flussi termici e le proprietà di isolamento termico. La sperimentazione ha mostrato la possibilità di realizzare barriere termiche di concezione innovativa con tecniche di termodeposizione al plasma in atmosfera controllata, e ne ha evidenziato le potenzialità in termini di protezione termica e di resistenza all’ossidazione.In the present paper presents the results related to the early stages diprogettazione, implementation and testing of a new type of thermal barrier coatings costituitada multilayer metal-ceramic obtained by termodeposizione to plasma.Scopo of the research was to characterize the materials used nelsistema Multilayer both from a point of view that the thermo-mechanical thermo-physical, dimodellizzare the behavior of the thermal barrier with the finite element analysis, einfine to evaluate the actual properties of the system by means of exposure tests adelevati flows termici.I materials that make up the various layers of the coating (ZrB2-SiC, Mo, ZrO2-Y2O3), were tested individually by means of a 4-point bending tests and dimisure of coefficient of thermal expansion so as to evaluate the properties termomeccanichea room temperature and up to 1500 ° C. Furthermore, using the tecnicalaser-flash, were studied thermo-physical properties (diffusivity and conducibilitàtermica) of the material object of the trial is at ambient temperature that adelevata temperatura.I results obtained were used for the implementation of specific models of finite aglielementi system (substrate - multilayer coating) with the aim diottimizzare thickness and number of layers and then to evaluate and minimize the mechanical stresstermo-induced thermal loads applicati.Infine tests were carried out preliminary exposure rivestimentomultistrato to evaluate the resistance to heat flow and the properties of isolamentotermico. The test showed the possibility of thermal barriers diconcezione with innovative techniques termodeposizione plasma atmosferacontrollata, and has highlighted the potential in terms of thermal protection and wear-resisting oxidation

Identification and evaluation of post-depositional mechanical traces on quartz assemblages. An experimental investigation

The evaluation of the state of preservation of archaeological lithic artefacts is the first step before starting a functional analysis. If lithic artefacts show a variety of damage from many contact materials, they are also subject to modifications from “natural” causes, such as water transport, soil abrasion, trampling etc. Studying alteration features gives us information to reconstruct the life story of lithic tools after their abandonment and helps us to better understand formation processes of archaeological sites. Prolonged movements under soil could be responsible for post depositional surface modifications that sometimes look like wear traces due to use. These alterations could have chemical and/or mechanical origin. Recognizing them is of paramount importance especially on quartz assemblages where usewear analysis requires a long and complex methodology that differs to a certain extent from the protocol applied to other artefacts produced with different raw materials such as flint, obsidian etc … For this reason, the use wear and post-depositional surface modification analysis on quartz and quartzite tools have been undertaken by very few researchers until now. The aim of this paper is to increase the experimental quartz field through the attempt to recreate mechanical contact between quartz flakes and sediments such as in archaeological contexts. Through the use of a Polishing Machine MECAPOL P320 equipped with two counter-rotating platens, it was possible to wear out two experimental flakes in a sandy quartzite sediment coming from Sai Island (Sudan) for 240 h. After the experimentation, the two flakes showed no edge damage or other visible modifications, but some micro traces on the crystal surface were present. Although long and demanding, this step sharply reduces possible errors in the recognition of use-wear during the experimental stage. The micro traces definable as abrasions on some parts of the crystal surface, have been analysed by a metallographic microscope and compared with the same crystal portion taken before the experiment. Even if it is difficult to reconstruct post depositional processes in a laboratory, this attempt shows that the contact between sediment and stone tools in a continuous movement can randomly abrade the crystal surface