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In the last years, bistable composite structures are finding interest in several aeronautical applications such as power harvesting devices or morphing applications on very small aircraft/drones, not needing servo-activated control systems. Residual stresses, developed upon cooling after curing, leads to warped the composite laminates. Several batches of unsymmetrical and unbalanced [0°/90°] laminates were cured in an autoclave according to a standard temperature cycle, following the pre-preg supplier suggested curing cycle. In order to increase the thermal stresses (and hence the bistability phenomenon), these laminates were removed from the autoclave immediately after the curing reaction and rapidly cooled down at room temperature not applying the indicated cool rate between 2 and 5 °C min−1. During storage at room temperature, thermal stresses changed over time, indicating that asymptotic stress relaxation occurs. The first part of this work looks at residual stress characterization of bistable composite plates measuring the changes of shape observed during room temperature annealing. Rectangular plates were produced and the bistable geometric shapes were accurately assessed using a laser scanner system over several days, in order to monitor the curvature changes due to stress relaxation. Then phenomenological viscoelastic predicting models were proposed for a quick estimate for the strain/stress relaxation phenomenon. The loss of bistability was demonstrated with the help of numerical simulation and experimental testing. The final goal was to gain a better knowledge of the relation between processing and final shape of bistable laminates, in order to make them suitable for application on small air vehicles.

Composite materials, in addition to the high specific mechanical properties, have properties enabling their applications in high-pressure, high-temperature (HPHT) and corrosive environment as occurs in deep water. Their use for manufacturing pipelines and offshore risers can provide relevant performance advantages over steel such as lower weight, improved fatigue capacity, corrosion resistance and higher strain limits. However, composite materials are more complex to use in design than metallic materials due to their anisotropic properties and lack of accurate failure prediction models. Thus, a continuous in-situ and in real-time Structural Health Monitoring (SHM) of composite components would be necessary and useful to promote their use in a wider range of operational conditions. In this work, an FRP pipe sample was instrumented with Piezoelectric Wafer Active Sensors (PWAS) used either as passive receivers or as transmitters of guided waves for active health monitoring in pitch-catch configuration. The propagation properties of guided waves in glass fibres reinforced composites were studied by developing MATLAB scripts, running FE simulation and experiments. The numerical and experimental signals were post-processed in MATLAB by Short Time Fourier Transform (STFT) in order to evaluate their frequency and time-frequency content. Furthermore, the guided waves were used to detect artificial defects imposed on the structure identifying their location. Several testcases were studied to find out the limitations and the most suitable conditions of using guided waves for defects monitoring in a composite pipe. The work proposes effective methods for pipe structural health evaluation by non-destructive techniques and ultrasonic guided waves.

Heritage buildings worldwide are primarily masonry construction. Over the centuries, these structures have demonstrated a high vulnerability in seismic events. The seismic protection and retrofitting of these historical structures require an effective structural solution, without compromise, cover or loss of architectural and artistic value. For these scenarios, the use of Fiber Reinforced Polymers (FRPs) is discouraged since removability of the intervention is often a mandatory requirement, and the polymeric adhesives bond the fiber to the masonry substrate, eliminating the possibility of preserving the underlying material during a replacement operation. In FRP-strengthening, the force transfer from the substrate to the FRP occurs by means of bond stresses. However, in the case of column confinement, while full bond is nevertheless developed through the adhesive, it is not necessary for the effectiveness of the confinement. Instead, the confining pressure is applied by the FRP when transversal dilatation of the column is mobilized. Thus, with the exception of the overlapping regions, an FRP retrofit for column confinement works due to a contact phenomenon instead of bond. In this context, new FRP-confinement techniques, based on contact rather than adhesion, can be developed. This paper presents research on fully-reversible contact-based techniques for FRP-confinement. Three different techniques were developed and demonstrated by the authors. Each technique was experimentally evaluated through compression tests of small-scale limestone cylinders. The reversibility of each technique was verified through comparison of the substrates before the FRP-confinement and after the testing. The effectiveness of each technique was evaluated by comparing the compressive strength and the deformability with those obtained for unconfined specimens. The concepts show promise as effective and reversible strengthening techniques.

Carbon fiber-epoxy thin laminates, manufactured adopting a [0/90] non-symmetric lay-up, are characterized by two stable curved shapes, so being bistable. These composite thin laminates are attracting great interest for their potential application as novel morphing structures and power harvesting devices in many engineering fields. The curvature changes of rectangular bistable plates were monitored at room temperature by a laser scanner system over a time span of 10 d. These changes were ascribed to the relaxation of thermal stresses over time. Anisotropic stress relaxation behavior was then studied looking at the matrix dominated properties, such as the transverse modulus in accelerated high temperature experiments and the moisture absorption. Then, a simple viscoelastic model was proposed together with a finite element analysis of the distortion arising from laminate cooling at the end of high temperature cure process. The experimental and numerical results showed that the transverse elastic modulus and the hygroscopic effect are the main factors affecting the shape relaxation of bistable laminates.

This work is aimed at proposing demonstrative actions devoted to show reprocessing and recyclability of PET originating from bottles collected from the seaside, in order to increase the consumer awareness on the importance of recycling plastics. To this purpose, collected bottles were washed, cut, grinded, extruded in the form of a thin wire adopting different cooling rates, which leads to a modulation of the crystallinity content. Once having optimized the processing parameters, the extruded wire was used to produce 3D printed samples through the fused deposition modelling (FDM). The changes in the crystalline structure due to the different processing conditions were assessed by DSC and XRD analyses, while rheological tests were performed in order to evaluate any modification in the viscosity of PET after repeated processing cycles. The reduction in thermal stability was confirmed by TGA analysis, which showed a progressive decrease in the degradation temperature as processing cycles increased. Finally, tensile tests highlighted the difference in the mechanical response due to the predominance of the crystalline or amorphous phase in the tested sample. In particular, a good mechanical behavior was found for the 3D-printed samples.

Although the high performance thermoplastics matrix composites have been studied for more than thirty years, only recently their advantages have been properly perceived and exploited, for a wide range of applications either in secondary either in primary aeronautical structures. In this work, compression testing of a flat panel stiffened with L-shaped stringers made of Polyphenylene-sulfide (PPS) matrix reinforced with carbon fibres, is presented. The stiffeners were joined to the base plate by induction welding, as reported in a former study. The numerical activities, aimed at static, buckling and post-buckling analysis, first of a single stringer, then of the stiffened panel under compressive load, provided results in good agreement with the experimental ones. The analyses were performed taking into account either for the geometric non-linearity associated with the large deformations of the structures under the action of compressive loads either for the local buckling of the flanges composing the stringers. Experimental activities were aimed at the characterization of the adopted materials with a special focus on the determination of buckling loads either of an L-shaped stringer either of a panel stiffened with four stingers. In both cases an excellent structural behaviour was shown, the panel and a single stringer being able to take huge loads after the first buckling appeared. The panel, in particular, showed an excellent post-buckling strength and broke by buckling failure of stringers. The welded interfaces did not fail indicating that thermoplastic welding is a suitable technique for assembly composite structural elements.

This work is aimed to study the application of a bio-based plasticizer, obtained by acetylation and epoxydation of cardanol, for the production of soft PVC foams. The use of epoxidized cardanol acetate allowed obtaining a more efficient foaming of soft PVC compared to phthalate plasticizer bis(2-ethylhexyl) phthalate (DEHP), mainly due to the lower viscosity attained in the decomposition range of azodicarbonamide (AZDC). As a consequence, the foams produced by epoxidized cardanol acetate showed a lower density compared to those produced with DEHP. The lower density yielded lower values of compressive modulus. However, the modulus was shown to be not only dependent on the density, but also showed a direct dependence on the type of plasticizer used, in addition to processing temperature and AZDC content. As a consequence, the specific compressive modulus also showed a direct dependence on the type of plasticizer, processing temperature and AZDC content. Such dependence was explained by considering different cellular morphologies developed during foaming under different processing conditions, including type of plasticizer. In particular, it was shown that the lower viscosity attained by epoxidized cardanol acetate plasticized PVC involved an increase of the average pore size of the foam, which was shown to be the main cause of the variation of the specific compressive modulus.

Out-of-plane permeability of reinforcement preforms is of crucial importance in the infusion of large and thick composite panels, but so far, there are no standard experimental methods for its determination. In this work, an experimental set-up for the measurement of unsaturated through thickness permeability based on the ultrasonic wave propagation in pulse echo mode is presented. A single ultrasonic transducer, working both as emitter and receiver of ultrasonic waves, was used to monitor the through thickness flow front during a vacuum assisted resin infusion experiment. The set-up was tested on three thick carbon fiber preforms, obtained by stacking thermal bonding of balanced or unidirectional plies either by automated fiber placement either by hand lay-up of unidirectional plies. The ultrasonic data were used to calculate unsaturated out-of-plane permeability using Darcy&rsquo, s law. The permeability results were compared with saturated out-of-plane permeability, determined by a traditional gravimetric method, and validated by some analytical models. The results demonstrated the feasibility and potential of the proposed set-up for permeability measurements thanks to its noninvasive character and the one-side access.

This work is aimed to study the suitability of cardanol and its derivatives as plasticizers for poly(lactic acid), PLA. Differential scanning calorimetry (DSC) was used to assess the plasticizing effectiveness of cardanol (CARD) and its derivatives, cardanol acetate and epoxidated cardanol acetate, comparing the results with those obtained with a commercially available plasticizer, poly (ethylene glycol), PEG, with an average molecular weight of 400 g mol−1. Measurement of the glass transition temperature highlighted that, among the tested cardanol derivatives, neat cardanol is the most effective plasticizer for PLA. In fact, the glass transition temperature of PLA plasticized by CARD is only slightly higher than that of PLA plasticized by PEG. This is attributed to the lower compatibility between PLA and CARD compared to PLA and PEG, as estimated by the interaction radius. Therefore, cardanol could represent a technically valid, economic, and largely available plasticizer for PLA. Moreover, DSC, an X-ray diffraction analysis, showed that, compared to PEG, the addition of CARD involves a limited increase of the rate of crystallization, even in this case, due to its lower compatibility with PLA. Dynamic mechanical analysis showed that, below glass transition, PEG is able to reduce the stiffness of PLA by a higher extent. However, as the temperature increases, retention of the shear modulus of PEG-plasticized PLA is much higher than that of CARD-plasticized PLA. As a consequence, above glass transition, the stiffness of CARD-plasticized PLA becomes lower than that of PEG-plasticized PLA. Therefore, despite its lower compatibility with PLA, CARD can impart to plasticized PLA lower modulus compared to PEG, when the plasticizer content is high enough to reduce the glass transition below room temperature.

In this study, carbon based ashes were produced by the wooden biomass pyro-gasification plant CMD ECO20. CMD ECO20 is a micro-scale combined heat and power system powered with biomass, under development by the Italian company Costruzioni Motori Diesel (C.M.D) S.p.A. It is an integrated system combining a downdraft gasifier, a spark ignition internal combustion engine, an electric generator and syngas cleaning devices, and it is able to produce electric and thermal power up to 20 kWe and 40 kWth. Three different types of fillers were produced from ashes starting from innovative green waste: the first type (MA) was obtained by mortar milling, while the second (DBA) and the third (WBA) one were produced by dry and wet ball milling, respectively. MA, DBA e WBA fillers were characterized by several techniques including Scanning Electron Microscopy (SEM), Multi-angle light scattering (MALS) and Energy Dispersive X-ray (EDX) Spectrometry. Each filler was added to epoxy resin EC01 in an amount equal to 1, 3, 5 and 10 wt%. The curing agent (22phr) was added to the resin that was cured for 1 h at 60 °C and 2 h at 150 °C. Finally, the flexural properties and the glass transition temperature of the cured neat epoxy and ashes filled epoxy composites were measured. The elastic modulus of the epoxy resin containing an amount of fillers from 1 to 10 wt% is higher in comparison to that of the neat epoxy. The flexural strength of the epoxy resin containing an amount of DBA of 3 wt% is also higher than that of the neat epoxy.

This study is aimed at the synthesis of antimicrobial hydroxyapatite (HAP)‐based composites for dental application by stereolithography (SLA). A micron‐sized commercial HAP was modified by methacrylate and quaternary ammonium salt, and, then, it was used in different amounts (namely 2.5, 5, and 10 wt%) as filler for a photocurable custom made resin for SLA. Thermal stability, microstructure, and particles size of the pristine (HAP) and modified HAP (mHAP) were evaluated by thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and particle size analyser (CILAS). The suitability of each formulation for stereolithography process was assessed by measuring viscosity, degree of conversion (DC%) by Fourier transform infrared spectroscopy (FTIR), glass transition temperature, and thermal stability. Photo‐cured specimens for physical, mechanical, and antimicrobial testing were built by SLA. The flexural strength of the samples was measured using a 3‐point bending test method, and the fractured surface was analysed by scanning electron microscopy (SEM). The antimicrobial activity of samples was investigated against some standard microorganisms (Staphylococcus aureus, Escherichia coli, and Candida albicans), as representative Gram positive and Gram negative bacteria and fungus, respectively. The flexural strength increased with a filler content up to 5% and slightly decreased for higher content. SEM analysis confirmed the presence of uniformly distributed HAP. The incorporation of mHAP reduced the bacterial and fungal growth in dose‐dependent manner in comparison with the neat samples. Finally, a prototype of dental bite was built by SLA.

Continuous induction welding for thermoplastic matrix composites requires an accurate modeling of the temperature distribution in the laminates, depending on the electromagnetic field. In this work, a transient three-dimensional finite element (FE) model was developed in order to study the heat transfer phenomena, and melting and crystallization in the welding area during the continuous induction welding of carbon fiber reinforced Poly(ether ether ketone) (CF/PEEK) laminates. The multiphysics problem was solved by coupling electromagnetic and heat transfer equations considering matrix melting and crystallization behavior. The model was able to simulate the continuous process along a linear path at a constant speed. The computed temperatures were in good agreement with experimental measurements. Several numerical simulation were used for selecting a processing window as a function of coil speed and current, for the welding of CF/PEEK joints. The results of welding experiments were evaluated by single lap shear tests and morphology characterization of the welded interfaces and fracture surfaces. Keywords: Carbon fiber, Finite element analysis, Joining, Heat treatment, Induction welding, Thermoplastic resin

During autoclave processing of composites for high-performance applications, it is mandatory to limit the porosities, which mainly depend on the hydrostatic pressure in the resin. This pressure, which is not constant during heating being affected either by resin flow either by elastic stress in the fiber stack, can be significantly different from the autoclave pressure. Modeling of resin flow and stress in the fiber stack is a key issue for prediction of the resin hydrostatic pressure, which can be related to void development. Also, the viscosity of the thermosetting matrix is a relevant parameter since it is not constant but evolves during curing going through a minimum and then increasing to an infinite value at gel point. In this work, a viscoelastic model is adopted to calculate the evolution of resin pressure during an autoclave cycle up to gelation, accounting for viscosity and degree of reaction changes. Therefore, the model includes a kinetic and rheological model whose input parameters have been experimentally determined by Differential Scanning Calorimetry and rheological analysis. The predicted resin pressure for three case studies associated to different composite and bleeder thicknesses and reinforcement materials have been discussed. POLYM. ENG. SCI., 57:631–637, 2017. © 2017 Society of Plastics Engineers

Electronic devices used for marine applications suffer from several issues that can compromise their performance. In particular, water absorption and permeation can lead to the corrosion of metal parts or short-circuits. The added mass due to the absorbed water affects the inertia and durability of the devices, especially for flexible and very thin micro-systems. Furthermore, the employment of such delicate devices underwater is unavoidably subjected to the adhesion of microorganisms and formation of biofilms that limit their reliability. Thus, the demand of waterproofing solutions has increased in recent years, focusing on more conformal, flexible and insulating coatings. This work introduces an evaluation of different polymeric coatings (parylene-C, poly-dimethyl siloxane (PDMS), poly-methyl methacrylate (PMMA), and poly-(vinylidene fluoride) (PVDF)) aimed at increasing the reliability of piezoelectric flexible microdevices used for sensing water motions or for scavenging wave energy. Absorption and corrosion tests showed that Parylene-C, while susceptible to micro-cracking during prolonged oscillating cycles, exhibits the best anti-corrosive behavior. Parylene-C was then treated with oxygen plasma and UV/ozone for modifying the surface morphology in order to evaluate the biofilm formation with different surface conditions. A preliminary characterization through a laser Doppler vibrometer allowed us to detect a reduction in the biofilm mass surface density after 35 days of exposure to seawater.

A novel, green route for pre-exfoliation of graphite based on a biodegradable polymer and high-power ultrasound is presented. Candelilla wax (CW), derived from the leaves of the candelilla plant, has been used for the first time as a natural non aqueous medium to induce the pre-exfoliation of expanded graphite (EG) under ultrasonic irradiation in an economical way. The proposed method uses also D-limonene as a natural organic solvent for reducing viscosity and increasing the affinity between the polar groups of EG and candelilla wax, thus improving the intercalation/exfoliation of EG. The quality of dispersion of the nanofiller in the natural wax matrix has been evaluated using multiple techniques. The addition of EG to wax and use of ultrasonic treatment leads to a reduced crystallinity, probably due to restrictions of the molecular movements, improved thermal stability of wax, and to an increased shear thinning exponent, which are all indicative of a high degree of EG dispersion. The ultrasonic dynamic mechanical results suggest a reduction in the cluster size and a better filler dispersion in the wax matrix promoted by polar or chemical reactions between the CW fractions and the graphite stacks, which was observed by XPS analysis. The results were compared to those obtained with paraffin, a synthetic wax, and confirmed the dispersion improvement obtained by using natural wax as a pre-exfoliating medium.

In this study, two different fillers were prepared from carbon-based ashes, produced from the wooden biomass of a pyro-gasification plant, and starting from lignocellulosic waste. The first type was obtained by dry ball-milling (DBA), while the second one was prepared by oxidation in H2O2 of the dry ball-milled ashes (oDBA). The characterization of the fillers included wide-angle x-ray diffraction (WAXD), thermogravimetric, and Fourier-transform infrared spectroscopy (FTIR) analysis. The DBA and oDBA fillers were then tested as possible catalysts for the crosslinking reaction of a diglycidyl ether of bisphenol A (DGEBA) with a diamine. The cure reaction was studied by means of rheometry and differential scanning calorimetry (DSC). The oDBA filler exhibits both a higher catalytic activity on the epoxide&ndash, amine reaction than the DBA sample and improved mechanical properties and glass transition temperature. The results obtained indicate, hence, the potential improvement brought by the addition of carbon-based waste ashes, which allow both increasing the flexural properties and the glass transition temperature of the epoxy resin and reducing the curing time, acting as a catalyst for the crosslinking reaction of the epoxy resin.

Focused on biomedical applications of thermo-responsive polymers, low-doses of gamma radiation from a 60Co source were applied in a simple one-pot method to synthesize graft copolymers of alginate and poly(N-isopropylacrylamide) (PNIPAAm) with different compositions. The molar percentage of grafted NIPAAm (% molar NIPAAm) was determined by thermogravimetric analysis (TGA) and elemental analysis (EA), being the copolymer structure-property relationship studied in terms of thermo-associative and rheological behavior in aqueous solutions. The addition of more NIPAAm monomer in the initial mixture of reaction, as well as, increasing absorbed dose lead to a greater grafting. However, increasing radiation dose produces copolymers with diminished viscoelastic properties caused by the alginate backbone scission. From rheological curves, two transition temperatures, Ta and Tgel, were determined as a consequence of the thermo-responsiveness of PNIPAAm side chain. Storage (G′) and loss (G″) modulus curves undergo a slope inversion at Ta temperature, where both moduli begin to increase caused by an associative behavior of PNIPAAm domains. While, Tgel temperature is related to the onset of the gelation process at the G′/G″ crossover. In order to design samples with liquid-gel transitions close to the human body, able to form gels in situ once inoculated, it was possible to tailor both transition temperatures selecting copolymers with an appropriate PNIPAAm content and optimizing the copolymer concentration in the aqueous solution. A good agreement between transition temperatures and viscoelastic properties was achieved for 5 wt% aqueous solutions of copolymers with low NIPAAm content synthesized at the lowest absorbed dose (0.5 kGy). Fil: Lencina, María Malvina Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina Fil: Rizzo, Chiara. University of Salento; Italia Fil: Demitri, Chistian. University of Salento; Italia Fil: Andreucetti, Noemi Amalia. Universidad Nacional del Sur. Departamento de Química; Argentina Fil: Maffezoli, Alfonso. University of Salento; Italia

The anisotropy of a short fiber reinforced composite produced by injection molding of basalt fibers and polypropylene matrix has been studied by X-ray microtomography (or micro-CT). Fiber orientation was analyzed using four stereological methods: Mean Intercept Length (MIL), Volume Orientation (VO), Star Volume Distribution (SVD) and Star Length Distribution (SLD). The fabric tensor obtained from micro-CT analysis provided information on the fiber orientation, indicating that fibers were partially aligned in the injection direction.

The goal of the work was the manufacturing of hydroxyapatite microsphere/polylactic acid (PLA) scaffolds by means of fused deposition modelling (FDM). Micrometer-sized hydroxyapatite spheres synthesized by spray drying (sdHA), were dispersed in PLA by extrusion compounding. Composite filaments were obtained from extrusion which were used in FDM 3D printing for the production of macroporous scaffolds. The sdHA microspheres were used in the composite in order to improve the biomimicry and the bioactivity of the 3D printed scaffold to increase the bone regeneration capacity. Morphological, thermal, physical and mechanical characterizations were performed on the 3D printed composites. Pure PLA scaffolds were 3D printed and used as a reference. Thermal analyses, TGA and DSC evidenced that the glass transition temperature and the degree of crystallinity of PLA were not influenced by the presence of sdHA. Morphological analysis showed a smooth surface of the printed samples when pure PLA was used. A rough surface was found on the PLA/sdHA composites, confirming, the homogeneous dispersion of the ceramic phase in the polymeric matrix. The higher porosity of the composite samples compared to PLA ones, most likely caused a decrease of the mechanical performances of the PLA/sdHA scaffolds. Composite scaffolds displayed stiffness values compatible with that of bone tissue.

This work is aimed at studying the suitability of polylactic acid (PLA) plasticized by two cardanol derivatives, i.e., cardanol and epoxidized cardanol acetate, in rotational molding, for the production of hollow items. For this purpose, plasticized PLA samples were obtained by melt mixing and then processed by a lab-scale rotational molding equipment. For comparison, poly(ethylene glycole), PEG, and plasticized PLA samples were also produced. Despite the very low cooling rates attained in rotational molding, completely amorphous samples were obtained with neat PLA and PLA plasticized by cardanol derivatives. In contrast, PEG plasticized PLA showed a very high degree of crystallinity, as highlighted by DSC and XRD analysis, which made the extraction of the rotomolded box-shaped specimens impossible. The plasticizing effectiveness of cardanol derivatives was proven by tensile testing of rotational molded prototypes, which highlighted the reduced modulus and strength and improved strain to break, compared to neat PLA. Therefore, efficient toughening of PLA can be attained by the use of the two cardanol derived plasticizers, which involves a significant reduction of the polymer glass transition, as well as a reduced increase of the crystallization kinetic. On the other hand, the reduction of the glass transition temperature due to the addition of plasticizer is responsible for significant crystallization effects even during ageing at room temperature, which involves significant embrittlement of the material.

Liquid resin infusion processes are becoming attractive for aeronautic applications as an alternative to conventional autoclave-based processes. They still present several challenges, which can be faced only with an accurate simulation able to optimize the process parameters and to replace traditional time-consuming trial-and-error procedures. This paper presents an experimentally validated model to simulate the resin infusion process of an aeronautical component by accounting for the anisotropic permeability of the reinforcement and the chemophysical and rheological changes in the crosslinking resin. The input parameters of the model have been experimentally determined. The experimental work has been devoted to the study of the curing kinetics and chemorheological behavior of the thermosetting epoxy matrix and to the determination of both the in-plane and out-of-plane permeability of two carbon fiber preforms using an ultrasonic-based method, recently developed by the authors. The numerical simulation of the resin infusion process involved the modeling of the resin flow through the reinforcement, the heat exchange in the part and within the mold, and the crosslinking reaction of the resin. The time necessary to fill the component has been measured by an optical fiber-based equipment and compared with the simulation results.

This work is aimed to the development and property optimization of cardanol derived plasticizers. To this purpose, different plasticizers were produced though different epoxidation routes, characterized by low toxicological and environmental impact. The plasticizers are characterized by different yield of epoxidation of the alkyl chain double bonds. The properties of the cardanol derived plasticizers were compared to the properties of commercial plasticizers, either phthalates or natural derived. Mechanical properties of soft PVC plasticized by cardanol derivatives were shown to be comparable to those of PVC with commercial plasticizers. The plasticizing efficiency of cardanol derivatives was significantly improved by increasing the yield of epoxidation. Also, mechanical properties performed after ageing showed the excellent stability of the properties of the cardanol derived plasticizer characterized by the higher yield. Evaluation of the property retention index after ageing indicated that such plasticizers showed an improved stability of properties compared to other commercial plasticizer. The results obtained highlight the relevance of an high conversion of the double bonds into epoxies in order to produce high quality plasticizers.

This work is aimed to study the suitability of a bio based compound, cardanol acetate (CA), as plasticizing agent of poly(lactic acid) (PLA). Compared to other natural derived plasticizers, cardanol acetate is not obtained from food crops but as a by product of cashew nut extraction. In addition, the cardanol derived plasticizers can be obtained by the use of non toxic and low environmental impact reagents. The plasticizing effectiveness of cardanol acetate was confirmed by the decrease of the glass transition temperature and flexural modulus, which were comparable to those obtained by the use of conventional oil based plasticizers, such as diethylhexyl phthalate (DEHP). In addition, calorimetric analysis revealed that the addition of the plasticizer, both cardanol derived and phthalate, involves a significant increase of the crystallization kinetics. An analysis of the flexural strength and deformation at break indicated that the increase of the crystallization kinetics has more dramatic effects compared to the decrease of the glass transition, particularly at low plasticizer content, finally leading to a decrease of the ductility. At higher plasticizer content, an increase of the ductility is observed, and PLA plasticized by 10% of CA showed a significant higher deformation at break than PLA plasticized by DEHP. In addition, plasticizer migration tests showed a lower weight loss of PLA plasticized by CA compared to DEHP plasticized PLA, which indicates the potential higher stability of properties of the cardanol derived plasticizer.

This paper is aimed to study the morphology of intercalated nanocomposites, by coupling experimental permeability data with different analytical models. X-Ray diffraction provided the reference morphological features of the nanocomposite, including gallery thickness and aspect ratio of the lamellar stacks. Afterward, the water permeability of two intercalated nanocomposites was used for the calculation of the nanofiller aspect ratio, following different approaches. The obtained results indicate that an assumption of impermeable stacks involves a significant over-estimation of the nanofiller aspect ratio. Further, when the morphological features determined in the assumption of impermeable particles are used for estimation of the nanocomposite diffusivity by the use of the Fricke model, results do not show a satisfactory agreement with experimental data. On the other hand, fitting experimental permeability data with an analytical model accounting for intra-stack diffusion provided an estimation of the nanofiller aspect ratio in excellent agreement with that obtained by XRD. Further, applying the Fricke equation with the morphological features determined by the permeable stack model, an excellent agreement to the experimental data was obtained. The results indicate the relevance of intra-stack diffusion in intercalated nanocomposite, and the need to account for it when modeling mass transfer in nanocomposites.

Stress relaxation behavior of unidirectional AS4/8852 carbon/epoxy composites at high temperatures has been investigated. Specimens with an off axis angle of 90° and ±45° have been exposed to constant strain and high temperature. The mechanical results have been modeled by Standard Linear Solid model. The obtained parameters have been implemented in a finite element (FEM) model able to predict the residual stresses in carbon fiber reinforced composites, both in the elastic and in the viscoelastic field.Stress relaxation behavior of unidirectional AS4/8852 carbon/epoxy composites at high temperatures has been investigated. Specimens with an off axis angle of 90° and ±45° have been exposed to constant strain and high temperature. The mechanical results have been modeled by Standard Linear Solid model. The obtained parameters have been implemented in a finite element (FEM) model able to predict the residual stresses in carbon fiber reinforced composites, both in the elastic and in the viscoelastic field.

This work is concerned with the mechanical characterization of bistable composite plates in order to investigate their nonlinear behavior dependence on mechanical factors, e.g. strain, stress trends and potential energy. The bistable laminates have two stable shapes that are actuated by a variety of mechanisms (piezoelectric ceramic based actuators, shape memory alloys or thermal actuation) to induce “snap-through” between states. These composite structures are receiving interest in several aeronautic applications such as shape changing applications without the need of servoactivated control systems. Scope of the work is to describe the “0” strain-stress status of the asymmetric bistable laminates, immediately after the manufacturing process. An experimental testing is carried out with the purpose of collecting enough data for the numerical and analytical analyses. Numerical simulations based on Finite Element Models (FEM) are used to study strain and stress fields of the laminates and successively to validate semi-analytical results. By the Classic Plate Lamination Theory (CLPT), an analytical model is developed to provide an interpretation of the bistability phenomenon. The experimental results, with FE and CLPT models, help to understand the relation between the mechanical features of the composite laminate and the bistability phenomenon. This paper reports on detailed nonlinear characterization of bistable plates using numerical, analytical and experimental data in order to provide a starting point for future works characterizing bistable strain-stress evolution over the time.

An aromatic epoxy monomer, formed by glycidylation of gallic acid, was crosslinked by adopting different curing agents to obtain bio-based, crosslinked resins with suitable engineering properties. Specifically, tri- and tetra-glycidyl ether of gallic acid (GEGA) were obtained using a two-step synthesis. These bio-based monomers were cured in the following three epoxy formulations: a stiff cycloaliphatic primary amine, isophorone diamine, and a flexible polypropylene oxide amine (Jeffamine D-230). Next, the homopolymerization of GEGA was studied using an ionic initiator, N,N-dimethylbenzylamine, and a complex curing mechanism highlighted by calorimetric and mass spectra analysis. Calorimetric and rheological measurements were used to compare the curing behavior of the studied GEGA-based formulations. Mechanical properties of the gallic acid-based epoxy resins were comparable with those of standard epoxy resin formulations, based on di-glycidyl ether of bisphenol A. Thermogravimetric analysis of cured samples showed a relevant char content at high temperatures.

The mechanical and electrochemical behavior of ultrasonic spot welded hybrid joints, made of AA5754 aluminum and carbon fiber reinforced epoxy with a co-cured thermoplastic surface layer, was studied. The effect of the welding parameters (energy and force) and the thickness of a thermoplastic film, applied as an upper ply in the composite lay-up, on the development of adhesion strength, was investigated. The best mechanical results were obtained when the welding parameters were able to achieve a large bonding area of mechanical interlocking between naked carbon fibers and aluminum and a better load distribution. The electrochemical results excluded the possibility of galvanic corrosion between aluminum and composite adherends thanks to the insulating action provided by the thermoplastic film.

Calcium phosphate, like hydroxyapatite (HA), is the principal bioactive material for bone grafts substitute, but being ceramics materials, it is not suitable for low-cost 3D printing techniques, such as fused deposition modeling (FDM). To this aim, HA is usually mixed with a 3D-printable thermoplastic polymer, like polylactic acid (PLA), in order to realize customized substitutes by FDM technique. However, in order to enhance the bioactivity of the substitute, it is important to produce high hydroxyapatite-loaded 3D-printable filaments. In this study, an innovative one-step solvent-free process for the production of PLA filaments, loaded with different amounts of HA, up to 50 mass%, was proposed. The filaments have been firstly characterized by rheological and thermal analysis [thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)] in order to assess their suitability for the 3D printing process, in terms of viscosity at melting point and degradation temperature. The filaments were then characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy in order to analyze the dispersion of HA in the polymeric matrix and the influence of the inorganic filler on the amorphous structure of the polymer. All filaments produced evidenced a value of viscosity suitable for the FDM process at the melting point (measured by DSC analysis) and a degradation temperature (measured by TGA analysis) higher than the temperature selected for the 3D printing process, still evidencing a good dispersion of the HA powder in the PLA matrix, even at the highest content of the filler. For this reason, all filaments were used to build objects of simple geometry by FDM. The preliminary high loaded 3D-printed samples present the same thermal and structural properties of the filaments indicating that the printing process does not alter the properties of the composite material.

The approach for joining thermosetting matrix composites (TSCs) proposed in this study is based on the use of a low melting co-cured thermoplastic film, added as a last ply in the stacking sequence of the composite laminate. During curing, the thermoplastic film partially penetrates in the first layer of the thermosetting composite, leading to macro-mechanical interlocking as the main connection mechanism between the thermoplastic film and the underlying composite. After curing, the thermosetting composite joints with the thermoplastic modified surface can be assembled by welding. Welding of the TSC-TSC joints is performed by ultrasonic and induction welding. The weld strength is investigated by morphological characterization of cross sections and failure surfaces and by mechanical testing. The effect of the thermoplastic film thickness on the welding process and on its outcome is also analyzed. Both induction and ultrasonic welding mostly result in good-quality welded joints. The welding process used as well as the initial thickness of the thermoplastic film are found to have a significant effect on the final thickness of the weld line and on the location of failure. Thicker thermoplastic films are found to ease the welding processes.

This work is aimed to the study of the thermal and UV stability of Poly Vinyl Chloride (PVC) plasticized by cardanol derivatives. To this purpose, soft PVC obtained by cardanol derivatives, as well as by commercial plasticizers, were subjected to different sources of degradation, i.e. thermal treatments and UV weathering, and characterized by means of the tensile tests. Analysis of variance (ANOVA) was used to highlight the statistical significance of the type of plasticizer and treatment of soft PVC on the mechanic properties. In particular, estimation of the retention index of different plasticizers to different sources of degradation allowed highlighting the better performances of PLACARD compared to the other commercial plasticizers. In absence on any relevant loss of plasticizer during thermal treatment or UV weathering, the change in mechanical properties was attributed to change in the chemical structure of PVC homopolymer, which was studied by FTIR analysis. It was shown that the better retention of property of soft PVC plasticized by PLACARD is due to a lower amount of thermal or UV activated degradation. Therefore, the results highlight that PLACARD plasticizer can also act as an efficient thermal and UV stabilizer, which could increase soft PVC durability and recyclability, and contribute to a reduction of the amount of thermal and UV stabilizers, with additional relevant effects on the toxicological and environmental impact of soft PVC.

The structural behaviour of bolted joints of composite laminates for aerospace applications was modelled comparing the shape, amplitude and phase of stress–strain cycles. This study proposes a model for the bolted joints resulting in a typical load–displacement curve, under cyclic loading, significantly affected by hysteretic effects. From the data gathered through the experimental activities, a constitutive relationship between strain and stress was proposed, starting from simple physical models. The assumption of a rigid shift between the laminates was used to correlate load and displacement curves in the different phases of the load cycle. The hysteretic behaviour was attributed to friction phenomena and interpreted using damping coefficients characterizing the global dynamic response of the structural joint.

The engineering aspects, which are associated with the development of nanocomposites, involve in either final properties or processability of nanocomposites. Both are affected by the distribution of nanofiller in the matrix and by the aspect ratio of the nanofiller. A nanofilled thermosetting resin can be exploited as a matrix for continuous fibers when the alignment of a high aspect ratio nanofiller is achieved, and in this case, a hierarchical composite is obtained. In this study, a new procedure for the alignment of nanofillers in a thermosetting matrix is proposed. The two-step approach is based on (i) the alignment of nanofillers (carbon nanotubes, graphene, etc.) in thermoplastic fibers by a fiber spinning process and (ii) the use of these nanocomposite fibers as a carrier to bring aligned nanofillers into a reactive thermosetting resin. These fibers, soluble in the thermosetting resin, release the nanofillers orientated according to the direction in which fibers are positioned, even after the curing of the matrix. The proof of concept is demonstrated by producing melt spun polyethylene terephtalate (PETg) fibers filled with graphene nanoplatelets (GNP) and multiwall carbon nanotubes (MWCNT) with a very high filler content (up to 10 wt%) in view of producing a hierarchical composite. POLYM. COMPOS., 36:1096–1103, 2015. © 2015 Society of Plastics Engineers

This work is aimed to study the diffusion in 3D nanocomposites obtained with stacks of lamellar nanofillers characterized by the presence of permeable galleries, by finite element (FE) analysis. To this purpose, a geometric model, based on a random distribution of noninterpenetrating stacks, with each one being made of regularly spaced lamellae, was developed. The developed model is able to account for diffusion between stacks (interstack diffusion) as well as diffusion inside stacks (intrastack diffusion). Simulation results showed that intrastack diffusion, related to flow inside galleries, can be quite relevant, particularly at high values of gallery thickness. Comparison of the simulation results with literature models shows that when intrastack diffusion is not taken into account, the diffusion behavior in intercalated nanocomposites is not well predicted. Therefore, intrastack permeability of nanofillers such as organic modified clays cannot be neglected. Such intrastack diffusivity is shown to depend on the morphological features of the nanofiller requiring the development of a proper mathematical model.

In this work the architectural anisotropy of short fiber reinforced polymers (SFRPs) has been characterized using X-ray computed micro-tomography (micro-CT) with four different morphometric methods: Mean Intercept Length (MIL), Volume Orientation (VO), Star Length Distribution (SLD) and Star Volume Distribution (SVD). The fabric tensor obtained from micro-CT analysis provided information on the fiber orientation, indicating that fibers were partially aligned in the injection direction. The fiber length and orientation obtained from optical microscopy and from the morphometric analysis in 3D, respectively, has been used to determine the mechanical properties of the composite sample, using a model based on micro and macromechanics. This approach leads to the prediction of the elastic constants of the component for any possible composite morphology resulting from injection, representing a key need for the design of SFRP components.

This article compares the catalytic activities of oxidized carbon black (oCB) and graphene oxide (eGO) samples on the kinetics of a reaction of diglycidyl ether of bisphenol A (DGEBA) with a diamine, leading to crosslinked insoluble networks. The study is mainly conducted by rheometry and Differential Scanning Calorimetry (DSC). Following the same oxidation procedure, CB samples are more efficiently oxidized than graphite samples. For instance, CB and graphite samples with high specific surface areas (151 and 308 m2/g), as oxidized by the Hummers’ method, exhibit O/C wt/wt ratios of 0.91 and 0.62, respectively. Due to the higher oxidation levels, these oCB samples exhibit a higher catalytic activity toward the curing of epoxy resins than fully exfoliated graphene oxide.

Transparent nanocomposite films were prepared using bacterial cellulose (BC) as reinforcement and diethylene glycol bis(allyl carbonate) polymer (DEAC) as matrix by vacuum infiltration and UV polymerization. The BC/DEAC nanocomposites exhibit excellent transparency up to 88% at wavelength of 550 nm. The uniform dispersion of resin in BC 3D network was evidenced from SEM and ATR-FTIR analyses, confirms the complete photo-polymerization of diethylene glycol bis(allyl)carbonate monomer to Poly (diethylene glycol bis(allyl carbonate) in BC network. The BC/DEAC composites have good mechanical properties, reaching a tensile strength of 130 MPa and a Young’s Modulus of 6.4 GPa. Applying a micromechanic modeling approach, the elastic modulus of the composite was used in order to determine the average aspect ratio of BC fibers. These flexible transparent BC/DEAC composite films can be considered as functional films for optoelectronics application.

Adhesion is attracting increasing interest in the aerospace field since composite materials have become, together with aluminium alloys, the main structural materials for aircraft primary structures. Nano-graphite was demonstrated to improve the mechanical performance of several polymers used as composite matrices. In this work Single Lap Joints (SLJs) of unidirectional composite laminates were manufactured, tested and simulated: two families of specimens were investigated and compared, one joined using conventional epoxy resin, the other joined with an adhesive obtained mixing the same epoxy resin with nano-graphite particles. The dispersion of expanded and sonicated graphene stacks (EGS, 3% wt) in the epoxy matrix was obtained by the swelling method, dispersing first the filler in acetone and then mixing it with the epoxy oligomers. Finally the solvent was evaporated and the filler-epoxy mixture was degassed under vacuum before adding an amine curing agent in a stoichiometric quantity. The research demonstrates the superior mechanical properties of the adhesive with the addition of nano-graphite through experimental characterization of its behaviour in terms of strength and energy absorption. Finite element numerical simulations have been carried out using the Cohesive Zone Model (CZM) element, obtaining as parameters the maximum shear stress and the critical fracture energy for the two adhesives. A good correlation between numerical and experimental results has been achieved and the criteria for developing reliable and accurate non-linear models of the adhesive failure have been established.

The growing use of reinforcement preforms during composite manufacturing requires resin soluble binders which significantly affect the properties of crosslinking thermosetting resins. In this study, for the first time the influence of an epoxy preforming binder on the curing kinetics and chemorheological behavior of a crosslinking epoxy matrix was studied. The results proved that the addition of the binder lead to a significant change of the curing behavior suggesting that the epoxy binder was an essential component needed to complete the stoichiometry of the resin-hardener mixture. The developed kinetic and chemorheological model of the experimental results could be used for process optimization.

Ultrasonic metal welding has been applied for joining aluminum AA5754 sheets to a thermoset matrix composite consisting in a carbon fiber reinforced epoxy resin (CF/epoxy). To overcome the limitations of thermosetting resins, that, unlike thermoplastic polymers, cannot melt due to their chemical structure, a thermoplastic film of Polyamide 6 (PA6) has been used as a surface layer of the CF/epoxy stack before curing. The functional surface created on the thermoset matrix composite enables a fast welding with a metallic sheet. By a proper selection of welding energy and force, an average adhesion strength of 34.8 MPa has been obtained on CF/epoxy-PA6-AA5754 ultrasonically welded joints. The morphological characterization has revealed that the aluminum-composite interface is characterized by carbon fibers in a direct contact or even embedded in aluminum, whose surface presents pores and crevices due to the pronounced plastic deformation of the Al interfacial area.

Skeletal defects reconstruction, using custom-made substitutes, represents a valid solution to replacing lost and damaged anatomical bone structures, renew their original function, and at the same time, restore the original aesthetic aspect. Rapid prototyping (RP) techniques allow the construction of complex physical models based on 3D clinical images. However, RP machines usually work with synthetic polymers; therefore, producing custom-made scaffolds using a biocompatible material directly by RP is an exciting challenge. The aim of the present work is to investigate the potentiality of 3D printing as a manufacturing method to produce an osteogenic hydroxyapatite-polylactic acid bone graft substitute.

The need for reconstructing complex bone defects in the maxillofacial region as a result of trauma, tumor surgery or congenital malformation has become a hot topic in the field of tissue engineering. Tools such as 3D computer aided design (CAD) systems and rapid prototyping (RP) machines can be exploited to fabricate custom made bone scaffolds. RP techniques allow the construction of complex physical models based on 3D clinical images elaborated by suitable software and CAD systems. Hydroxyapatite (HA) is one of the most commonly used materials for bone reconstruction because of its close similarity in composition to human bone and teeth. Thus, producing a custom-made scaffold from a ceramic material directly by RP represents an exciting challenge. The aim of this paper is the development of a suspension of HA powder dispersed in an UV curable epoxy based resin, suitable for stereolithography (SLA). The influence of different HA concentrations within the ceramic suspension on the kinetics of the photochemical reaction was firstly investigated. The rheological behavior of the same ceramic suspensions was also analyzed by verifying the effect of HA on the viscosity and the stability of the suspensions as a function of the shear rate and the time from preparation. After the selection of a suitable suspension, simple green ceramic bars built by stereolithography and sintered with an appropriate thermal cycle, were built and characterized, showing good mechanical properties. A complex prototype, starting from a CAD model, was finally built by a SLA apparatus. & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

The strong influence of graphite oxide (GO) nanofiller on the glass transition temperature ( T g ) of epoxy resins, generally attributed to restricted molecular mobility of the epoxy matrix by the nanofiller or to the crosslinking of GO layers via the epoxy chains, is investigated. The study confirms that large increases of the glass transition temperature of the nanocomposite can be observed in presence of GO. However, similar T g increases are observed, when the filler is a high-surface-area graphite (HSAG), lacking oxidized groups. Moreover, these T g differences tend to disappear as a consequence of aging or thermal annealing. These results suggest that the observed T g increases are mainly due to a catalytic activity of graphitic layers on the crosslinking reaction between the epoxy resin components (epoxide oligomer and di-amine), rather than to reaction of the epoxide groups with functional groups of GO. This hypothesis is supported by investigating the catalytic activity of graphite-based materials on reactions between analogous monofunctional epoxide and amine compounds.

This work is aimed to present an innovative technology for the reinforcement of beams for urban furniture, produced by in-mold extrusion of plastics from solid urban waste. This material, which is usually referred to as “recycled plastic lumber”, is characterized by very poor mechanical properties, which results in high deflections under flexural loads, particularly under creep conditions. The Prowaste project, founded by the EACI (European Agency for Competitiveness and Innovation) in the framework of the Eco-Innovation measure, was finalized to develop an innovative technology for selective reinforcement of recycled plastic lumber. Selective reinforcement was carried out by the addition of pultruded glass rods in specific positions with respect to the cross section of the beam, which allowed optimizing the reinforcing efficiency. The reinforcement of the plastic lumber beams with pultruded rods was tested at industrial scale plant, at Solteco SL (Alfaro, Spain). The beams obtained, characterized by low cost and weight, were commercialized by the Spanish company. The present paper presents the most relevant results of the Prowaste project. Initially, an evaluation of the different materials candidates for the reinforcement of recycled plastic lumber is presented. Plastic lumber beams produced in the industrial plant were characterized in terms of flexural properties. The results obtained are interpreted by means of beam theory, which allows for extrapolation of the characteristic features of beams produced by different reinforcing elements. Finally, a theoretical comparison with other approaches which can be used for the reinforcement of plastic lumber is presented, highlighting that, among others, the Prowaste concept maximizes the stiffening efficiency, allowing to significantly reduce the weight of the components.

This work is aimed to study the use of pultruded profiles for the selective reinforcement of linear low density polyethylene (LLDPE) parts produced by rotational molding. A preliminary screening on different types of pultruded profiles was performed, highlighting the relevance of adhesion to LLDPE in order to prevent debonding of the reinforcing pultruded profiles. As expected, high density polyethylene (HDPE) matrix pultruded tapes are characterized by a very high adhesion to rotomolded LLDPE. Therefore, HDPE matrix pultruded tapes, fastened on the inner surface of the mold, are incorporated into LLDPE during rotomolding. Plate bending tests performed on reinforced rotomolded plates and pressurization tests performed on the box shaped prototypes showed a significant increase of the stiffness with a negligible amount of reinforcement and increase of the weight of the component.

In this work, nanocomposite adhesives obtained using an organically modified montmorillonite (OMM) in a polyurethane matrix were studied. The basal distance of OMM before and after mixing with the polyol and after curing was characterized by X-Ray diffraction. The viscosity of polyols-OMM systems was studied as function of shear rate in a cone-plate rheometer in order to correlate the viscosity with the aggregation state of OMM. A simple model accounting for an apparent increase of rheological units size associated with the intercalation of macromolecules into OMM galleries is proposed. Curing was performed at room temperature for 1 week. The basal distances of crosslinked PU nanocomposites were obtained by X-ray diffraction. The glass transition temperature, Tg, of PU nanocomposites, as measured using differential scanning calorimetry, increases with increasing volume fraction of OMM. Finally, the permeability to oxygen and water vapor of polyurethane clay-nanocomposites was measured. The gas permeation through the composites was correlated to the volume fraction of the impermeable inorganic part of the OMM. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

In this work, films and fibers of Polypropylene based composites reinforced with quartz were investigated. The materials were processed in a twin screw extruder with filler contents of 1, 2.5, and 5 wt%. Morphology, thermal properties, and mechanical behavior of these materials were studied. A homogeneous filler dispersion and particle alignment in the extrusion direction was detected for the films. Thermograms displayed a marginal nucleating effect of quartz particles. Uniaxial tensile tests indicated a high ductility level and strain hardening for the composites processed as films (in the extrusion direction). Single fiber tests displayed improved tensile properties compared with the same materials produced as films. Quasi-static fracture tests showed a completely ductile behavior for the films in the extrusion direction. In addition, films fracture toughness was found to increase with filler content. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

The present work deals with the development of a biodegradable superabsorbent hydrogel, based on cellulose derivatives, for the optimization of water resources in agriculture, horticulture and, more in general, for instilling a wiser and savvier approach to water consumption. The sorption capability of the proposed hydrogel was firstly assessed, with specific regard to two variables that might play a key role in the soil environment, that is, ionic strength and pH. Moreover, a preliminary evaluation of the hydrogel potential as water reservoir in agriculture was performed by using the hydrogel in experimental greenhouses, for the cultivation of tomatoes. The soil-water retention curve, in the presence of different hydrogel amounts, was also analysed. The preliminary results showed that the material allowed an efficient storage and sustained release of water to the soil and the plant roots. Although further investigations should be performed to completely characterize the interaction between the hydrogel and the soil, such findings suggest that the envisaged use of the hydrogel on a large scale might have a revolutionary impact on the optimization of water resources management in agriculture.