Publications by authors named "Mariaenrica Frigione"

21 Publications

  • Page 1 of 1

Reliability Prediction of Acrylonitrile O-Ring for Nuclear Power Applications Based on Shore Hardness Measurements.

Polymers (Basel) 2021 Mar 19;13(6). Epub 2021 Mar 19.

Department of Manufacturing Engineering, Universidad Nacional de Educación a Distancia (UNED), 28040 Madrid, Spain.

The degradation of polymeric components is of considerable interest to the nuclear industry and its regulatory bodies. The objective of this work was the development of a methodology to determine the useful life-based on the storage temperature-of acrylonitrile O-rings used as mechanical sealing elements to prevent leakages in nuclear equipment. To this aim, a reliability-based approach that allows prediction of the use-suitability of different storage scenarios (that involve different storage times and temperatures) considering the further required in-service performance, is presented. Thus, experimental measurements of Shore A hardness have been correlated with storage variables (temperature and storage time). The storage (and its associated hardening) was proved to have a direct effect on in-service durability, reducing this by up to 60.40%. Based on this model, the in-service performance was predicted; after the first three years of operation the increase in probability of failure (POF) was practically insignificant. Nevertheless, from this point on, and especially, from 5 years of operation, the POF increased from 10% to 20% at approximately 6 years (for new and stored). From the study, it was verified that for any of the analysis scenarios, the limit established criterion was above that of the storage time premise considered in usual nuclear industry practices. The novelty of this work is that from a non-destructive test, like a Shore A hardness measurement, the useful life and reliability of O-rings can be estimated and be, accordingly, a decision tool that allows for improvement in the management of maintenance of safety-related equipment. Finally, it was proved that the storage strategies of our nuclear power plants are successful, perfectly meeting the expectations of suitability and functionality of the components when they are installed after storage.
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http://dx.doi.org/10.3390/polym13060943DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8003519PMC
March 2021

Cold-Cured Bisphenolic Epoxy Adhesive Filled with Low Amounts of CaCO: Effect of the Filler on the Durability to Aqueous Environments.

Materials (Basel) 2021 Mar 10;14(6). Epub 2021 Mar 10.

Department of Innovation Engineering, University of Salento, Via Arnesano, 73100 Lecce, Italy.

The effects of aging exposures to three non-saline aqueous environments on the compressive mechanical properties of a calcium carbonate-filled bisphenolic epoxy adhesive, cold-cured with the addition of two curing agents suitable for the cure at ambient temperature (i.e., Mannich base and triethylenetetramine), were assessed. The amount of the added filler (CaCO) varied from 1 to 3 g per 100 g of resin; the immersion times in each of the selected medium varied from 1 to 10 months. It was found that the mechanical properties measured in compression mode on cylindrical specimens of unfilled and CaCO-loaded epoxy were scarcely influenced by the kind of curing agent employed; only the compressive modulus was limitedly affected by this parameter. Referring to the behavior when aged in water, the CaCO-filled epoxies displayed noticeable growths in modulus, small reductions in strength, and limited variations in strain, with a certain influence of the exposure time, especially when comparing the properties at the lowest time with those at medium-long times. On the basis of the results of statistical MANOVA analysis, it can be concluded that among the compositional factors (i.e., the type of curing agent employed to cure the epoxy compounds and the micro-filler content), only the amount of CaCO filler significantly affects the compressive modulus.
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http://dx.doi.org/10.3390/ma14061324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7998940PMC
March 2021

Novel Nano-Filled Coatings for the Protection of Built Heritage Stone Surfaces.

Nanomaterials (Basel) 2021 Jan 25;11(2). Epub 2021 Jan 25.

Department of Innovation Engineering, University of Salento, Prov.le Lecce-Monteroni, 73100 Lecce, Italy.

An experimental nano-filled coating, based on a fluorine resin containing SiO nano-particles, was applied on calcareous stones, representative of materials used in buildings and monuments of the Mediterranean basin; for comparison purposes, two commercial products were applied on the same substrates. The efficacy of the protective treatments was assessed by analyzing different characteristics of the three experimental/commercial products, i.e., color changes and permeability to water vapor to evaluate the treatments' harmlessness; capillary water absorption and water stone contact angle to evaluate the protection against water ingress; oleophobicity of the treated surfaces and the behavior under staining by acrylic blue-colored spray paint and felt-tip marker to verify the anti-graffiti action. Finally, the properties of the treated stone surfaces were analyzed also after the application of pancreatin, used to simulate bird excreta (guano). The protective coatings were found to promote graffiti removal, reducing also the detrimental effects due to simulated guano. The experimental nano-filled product, in addition, was able to provide outstanding performance but using smaller amounts of product in comparison to commercial systems.
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http://dx.doi.org/10.3390/nano11020301DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7912206PMC
January 2021

Innovative Materials for Construction.

Materials (Basel) 2020 Dec 2;13(23). Epub 2020 Dec 2.

Civil Engineering Department, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal.

Academic and industrial efforts around the world are continuously engaged to develop new smart materials that can provide efficient alternatives to conventional construction materials and improve the energy-efficiency in buildings or are able to upgrade, repair, and protect existing infrastructures [...].
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http://dx.doi.org/10.3390/ma13235448DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7730497PMC
December 2020

Aging Effects of Aqueous Environment on Mechanical Properties of Calcium Carbonate-Modified Epoxy Resin.

Polymers (Basel) 2020 Oct 30;12(11). Epub 2020 Oct 30.

Department of Innovation Engineering, University of Salento, Via Arnesano, 73100 Lecce, Italy.

The purpose of this study was to assess the effects of different aqueous environments (i.e., demineralised, distilled and spring water) on the mechanical properties of a cold-cured bisphenolic epoxy resin modified with the addition of calcium carbonate filler, typically employed as structural adhesive. The parameters selected for the analysis have been; the kind of curing agent employed to cure the epoxy resin at ambient temperature (i.e., Mannich base and triethylenetetramine); the load of calcium carbonate added to liquid epoxy (i.e., from 1 to 3 g per 100 g of resin) and; the duration of the exposure to the different aging conditions (i.e., from 1 to 10 months). Cylindrical specimens of calcium carbonate-modified epoxy systems were tested in compression mode, before and after each of the aging regimes. The effect of the selected curing agents is very small, and they are both suitable for a cure at ambient temperature, on the unfilled epoxy on compressive maximum strength and strain at break; the choice of the hardener affects instead the compressive modulus. The CaCO3 amount was demonstrated to have a significant effect on the mechanical characteristics of un-aged epoxy systems, leading to growth in compressive modulus and maximum strength with reductions in strain at break. Generally speaking, the aging time noticeably affects the compressive properties of calcium carbonate-modified epoxies while almost negligible is the kind of water employed in each exposure regime. Notwithstanding the adverse effects of an aqueous environment on compressive mechanical properties of CaCO-filled epoxies, these systems keep compressive modulus and maximum strength greater than, and close to, respectively, the same characteristics measured on unaged unfilled control epoxies, demonstrating the positive effect of the addition of this kind of filler to epoxy-based structural adhesives, especially with the addition of 2 and 3 g of CaCO per 100 g resin. The results obtained in this study demonstrated that it is possible to contrast the detrimental effects observed in cold-cured epoxy-based structural adhesives due to their aging in water upon the addition of limited amounts (particularly at 2 and 3 g per 100 g resin) of a cheap CaCO filler.
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http://dx.doi.org/10.3390/polym12112541DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693412PMC
October 2020

Tomato Oil Encapsulation by α-, β-, and γ-Cyclodextrins: A Comparative Study on the Formation of Supramolecular Structures, Antioxidant Activity, and Carotenoid Stability.

Foods 2020 Oct 27;9(11). Epub 2020 Oct 27.

Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Monteroni di Lecce, 73100 Lecce, Italy.

Cyclodextrins (CDs) are oligosaccharides, comprising 6 (α), 7 (β), or 8 (γ) glucose residues, used to prepare oil-in-water emulsions and improve oil stability towards degradation. In this research, the aptitude of α-, β-, and γ-CDs to form complexes with a supercritical CO extracted lycopene-rich tomato oil (TO) was comparatively assessed. TO/CD emulsions and the resulting freeze-dried powders were characterized by microscopy, Fourier transform infrared-attenuated total reflection (FTIR-ATR), and differential scanning calorimetry (DSC), as well as for their antioxidant activity. Furthermore, carotenoid stability was monitored for 90 days at 25 and 4 °C. Confocal and SEM microscopy revealed morphological differences among samples. α- and β-CDs spontaneously associated into microcrystals assembling in thin spherical shells (cyclodextrinosomes, Ø ≈ 27 µm) at the oil/water interface. Much smaller (Ø ≈ 9 µm) aggregates were occasionally observed with γ-CDs, but most TO droplets appeared "naked". FTIR and DSC spectra indicated that most CDs did not participate in TO complex formation, nevertheless structurally different interfacial complexes were formed. The trolox equivalent antioxidant capacity (TEAC) activity of emulsions and powders highlighted better performances of α- and β-CDs as hydrophobic antioxidants-dispersing agents across aqueous media. Regardless of CDs type, low temperature slowed down carotenoid degradation in all samples, except -[]-lycopene, which does not appear efficiently protected by any CD type in the long storage period.
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http://dx.doi.org/10.3390/foods9111553DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693019PMC
October 2020

Experimental Studies and Modeling of the Degradation Process of Poly(Lactic--Glycolic Acid) Microspheres for Sustained Protein Release.

Polymers (Basel) 2020 Sep 8;12(9). Epub 2020 Sep 8.

Department of Innovation Engineering, University of Salento, Via Arnesano, 73100 Lecce, Italy.

In this study, poly(lactic--glycolic acid) microspheres (PLGA MS)for controlled protein release by double emulsion-solvent evaporation were produced and characterized for their morphological and technological features. MS autocatalytic degradation was described by a mathematical model based on a Michaelis and Menten-like chemical balance. Here, for the first time MS degradation was correlated to the advancement of MS degradation front with respect to the degraded radius, derived from mass loss experiments. The model can satisfactorily describe the kinetics of advancement of the degradation front experimentally derived for all MS formulations, especially when produced at higher PLGA concentrations.
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http://dx.doi.org/10.3390/polym12092042DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7569845PMC
September 2020

Recent Advances and Trends of Nanofilled/Nanostructured Epoxies.

Materials (Basel) 2020 Aug 3;13(15). Epub 2020 Aug 3.

CNR-SPIN, via Giovanni Paolo II 132, 84084 Fisciano (Salerno), Italy.

This paper aims at reviewing the works published in the last five years (2016-2020) on polymer nanocomposites based on epoxy resins. The different nanofillers successfully added to epoxies to enhance some of their characteristics, in relation to the nature and the feature of each nanofiller, are illustrated. The organic-inorganic hybrid nanostructured epoxies are also introduced and their strong potential in many applications has been highlighted. The different methods and routes employed for the production of nanofilled/nanostructured epoxies are described. A discussion of the main properties and final performance, which comprise durability, of epoxy nanocomposites, depending on chemical nature, shape, and size of nanoparticles and on their distribution, is presented. It is also shown why an efficient uniform dispersion of the nanofillers in the epoxy matrix, along with strong interfacial interactions with the polymeric network, will guarantee the success of the application for which the nanocomposite is proposed. The mechanisms yielding to the improved properties in comparison to the neat polymer are illustrated. The most important applications in which these new materials can better exploit their uniqueness are finally presented, also evidencing the aspects that limit a wider diffusion.
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http://dx.doi.org/10.3390/ma13153415DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7435812PMC
August 2020

Thermal Performance of Mortars Based on Different Binders and Containing a Novel Sustainable Phase Change Material (PCM).

Materials (Basel) 2020 Apr 28;13(9). Epub 2020 Apr 28.

Innovation Engineering Department, University of Salento, Prov. le Lecce-Monteroni, 73100 Lecce, Italy.

Increasing concerns about climate change and global warming bring about technical steps for the development of several energy-efficient technologies. Since the building sector is one of the largest energy users for cooling and heating necessities, the incorporation of a proper energy-efficient material into the building envelopes could be an interesting solution for saving energy. Phase change material (PCM)-based thermal energy storage (TES) seems suitable to provide efficient energy redistribution. This is possible because the PCM is able to store and release its latent heat during the phase change processes that occurs according to the environmental temperature. The purpose of this paper was the characterization of the thermal properties of a composite PCM (i.e., Lecce stone/poly-ethylene glycol, previously developed) incorporated into mortar compositions based on different binders (i.e., hydraulic lime and cement). The study was carried out using an experimental set up through which it was possible to simulate the different seasons of the years. It was observed that the addition of PCM in mortars leads to a decrease of the maximum temperatures and increase of the minimum temperatures. Furthermore, the results shown a reduction of the heating and cooling needs, thus confirming the capability of this material to save energy.
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http://dx.doi.org/10.3390/ma13092055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7254294PMC
April 2020

Experimental Cold-Cured Nanostructured Epoxy-Based Hybrid Formulations: Properties and Durability Performance.

Polymers (Basel) 2020 Feb 19;12(2). Epub 2020 Feb 19.

Loughborough University, Loughborough, UK.

Different hybrid epoxy formulations were produced and cold-cured, monitoring the properties development during low temperature curing and aging. All systems were based on silane functionalized bis-phenol A (DGEBA) resins (Part A), cured at ambient temperature with two amine hardeners (Part B). The different components of the formulations were selected on their potential capability to bring about enhancements in the glass transition temperature. The durability of the produced hybrids was probed in comparison to the corresponding neat epoxies by monitoring changes in glass transition temperature () and flexural mechanical properties after exposure to different levels of humidity and immersion in water and at temperatures slightly higher than the local ambient temperature, in order to simulate the conditions encountered during summer seasons in very humid environments. The thermal degradation resistance of the hybrid systems was also evaluated by thermogravimetric analysis.
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http://dx.doi.org/10.3390/polym12020476DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7077680PMC
February 2020

Applications of Sustainable Polymer-Based Phase Change Materials in Mortars Composed by Different Binders.

Materials (Basel) 2019 Oct 25;12(21). Epub 2019 Oct 25.

Civil Engineering Department, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal.

Eco-sustainable, low toxic and low flammable poly-ethylene glycol (PEG) was forced into flakes of the porous Lecce stone (LS), collected as stone cutting wastes, employing a very simple cheap method, to produce a "form-stable" phase change material (PCM). The experimental PCM was included in mortars based on different binders (hydraulic lime, gypsum and cement) in two compositions. The main thermal and mechanical characteristics of the produced mortars were evaluated in order to assess the effects due to the incorporation of the PEG-based PCM. The mortars containing the PEG-based PCM were found to be suitable as thermal energy storage systems, still displaying the characteristics melting and crystallization peaks of PEG polymer, even if the related enthalpies measured on the mortars were appreciably reduced respect to pure PEG. The general reduction in mechanical properties (in flexural and compressive mode) measured on all the mortars, brought about by the presence of PEG-based PCM, was overcome by producing mortars possessing a greater amount of binder. The proposed LS/PEG composite can be considered, therefore, as a promising PCM system for the different mortars analyzed, provided that an optimal composition is identified for each binder.
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http://dx.doi.org/10.3390/ma12213502DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6861952PMC
October 2019

Electron dispersive X-ray spectroscopy and degradation properties of hyaluronic acid decorated microparticles.

Colloids Surf B Biointerfaces 2019 Sep 19;181:896-901. Epub 2019 Jun 19.

Dipartimento di Farmacia, Università di Napoli Federico II, Via D. Montesano 49, 80131, Napoli, Italy; Interdisciplinary Research Centre on Biomaterials, CRIB, Università di Napoli Federico II, P.le Tecchio, 80, 80125, Napoli, Italy.

The purpose of this study was to produce poly(DL-lactic-co-glycolic acid) (PLGA) - based microparticles (MPs), externally decorated with hyaluronic acid (HA). The MPs are intended for intravitreal injections in the treatment of posterior eye segment and have been designed to prolong the release of growth factors into the vitreous body, therefore aiming to increase the time interval between two consecutive injections. The MPs, prepared by a modified double emulsion-solvent evaporation technique and loaded with bovine serum albumins (BSA) and ciliary neurotrophic factor (CNTF), were spherical, with a diameter around 70 μm and a >90% encapsulation efficiency. Energy Dispersive Spectroscopy (EDS) outcomes indicated that HA presence in the external aqueous phase of the emulsion did affect the surface properties of MPs. Moreover, poloxamers drastically slowed down MP degradation properties which are, in turn, closely related to their ability to prolong drug release. This is promising for the envisaged application of the produced MPs. Further work will be devoted to optimizing MP formulation with respect to the envisaged intravitreal route of administration.
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http://dx.doi.org/10.1016/j.colsurfb.2019.06.044DOI Listing
September 2019

Phase Change Materials for Energy Efficiency in Buildings and Their Use in Mortars.

Materials (Basel) 2019 Apr 17;12(8). Epub 2019 Apr 17.

Innovation Engineering Department, University of Salento, Prov.le Lecce-Monteroni, 73100 Lecce, Italy.

The construction industry is responsible for consuming large amounts of energy. The development of new materials with the purpose of increasing the thermal efficiency of buildings is, therefore, becoming, imperative. Thus, during the last decades, integration of Phase Change Materials (PCMs) into buildings has gained interest. Such materials can reduce the temperature variations, leading to an improvement in human comfort and decreasing at the same time the energy consumption of buildings, due to their capability to absorb and release energy from/in the environment. In the present paper, recent experimental studies dealing with mortars or concrete-containing PCMs, used as passive building systems, have been examined. This review is mainly aimed at providing information on the currently investigated materials and the employed methodologies for their manufacture, as well as at summarizing the results achieved so far on this subject.
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http://dx.doi.org/10.3390/ma12081260DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6515401PMC
April 2019

Cold-Cured Epoxy-Based Organic⁻Inorganic Hybrid Resins Containing Deep Eutectic Solvents.

Polymers (Basel) 2018 Dec 22;11(1). Epub 2018 Dec 22.

Department of Engineering for Innovation, University of Salento, via per Monteroni, 73100 Lecce, Italy.

The development of improved cold-cured resins, to be used as either adhesives or matrices for FRP (fiber reinforced polymer) composites employed in the construction industry, has become the focus of several academic and industrial research projects. It is expected that the use of nano-structured organic⁻inorganic hybrid materials could represent a realistic alternative to commercial epoxy-based resins due to their superior properties, especially in terms of higher durability against: moisture, temperatures, harsh environments, and fire. In this context, organic⁻inorganic epoxy hybrids were synthesized by a modified sol⁻gel method without the addition of water. The experimental formulations were prepared starting from a mixture of a silane-functionalized epoxy resin, alkoxysilane components and a deep eutectic solvent (DES) based on a blend of choline chloride and urea. The latter was added in two different loads in order to analyze in depth its effect as a promoter for an effective dispersion of silica nano-phases, formed through hydrolysis and condensation reactions, into the cross-linked epoxy network. The produced formulations were cold-cured for different time spans in the presence of two hardeners, both suitable for a curing process at ambient temperature. In this first part of a wider experimental program, several analyses were carried out on the liquid (rheological and calorimetric) and cold-cured (calorimetric, thermogravimetric, dynamic-mechanical, flexural mechanical, and morphological) systems to evaluate and quantify the improvement in properties brought about by the presence of two different phases (organic and inorganic) in the same epoxy-based hybrid system.
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http://dx.doi.org/10.3390/polym11010014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6401923PMC
December 2018

Durability Issues and Challenges for Material Advancements in FRP Employed in the Construction Industry.

Polymers (Basel) 2018 Feb 28;10(3). Epub 2018 Feb 28.

Institute of Archaeological Heritage-Monuments and Sites, CNR⁻IBAM, Prov.le Lecce-Monteroni, 73100 Lecce, Italy.

The use of fiber reinforced polymer (FRP) composites for the rehabilitation of buildings or other infrastructure is increasingly becoming an effective and popular solution, being able to overcome some of the drawbacks experienced with traditional interventions and/or traditional materials. The knowledge of long-term performance and of durability behavior of FRP, in terms of their degradation/aging causes and mechanisms taking place in common as well as in harsh environmental conditions, still represents a critical issue for a safe and advantageous implementation of such advanced materials. The research of new and better performing materials in such fields is somewhat limited by practical and economical constrains and, as a matter of fact, is confined to an academic argument.
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http://dx.doi.org/10.3390/polym10030247DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6414872PMC
February 2018

Assessment of collagen crosslinking and denaturation for the design of regenerative scaffolds.

J Biomed Mater Res A 2016 Jan 27;104(1):186-94. Epub 2015 Aug 27.

Department of Engineering for Innovation, University of Salento, Lecce, 73100, Italy.

Crosslinking and denaturation were two variables that deeply affected the performance of collagen-based scaffolds designed for tissue regeneration. If crosslinking enhances the mechanical properties and the enzymatic resistance of collagen, while masking or reducing the available cell binding sites, denaturation has very opposite effects, as it impairs the mechanical and the enzymatic stability of collagen, but increases the number of exposed cell adhesive domains. The quantification of both crosslinking and denaturation was thus fundamental to the design of collagen-based scaffolds for selected applications. The aim of this work was to investigate the extents of crosslinking and denaturation of collagen-based films upon dehydrothermal (DHT) treatment, that is, one of the most commonly employed methods for zero-length crosslinking that shows the unique ability to induce partial denaturation. Swelling measurements, differential scanning calorimetry, Fourier transform infrared spectroscopy, colorimetric assays for the quantification of primary amines, and mechanical tests were performed to analyze the effect of the DHT temperature on crosslinking and denaturation. In particular, chemically effective and elastically effective crosslink densities were evaluated. Both crosslinking and denaturation were found to increase with the DHT temperature, although according to different trends. The results also showed that DHT treatments performed at temperatures up to 120°C maintained the extent of denaturation under 25%. Coupling a mild DHT treatment with further crosslinking may thus be very useful not only to modulate the crosslink density, but also to induce a limited amount of denaturation, which shows potential to partially compensate the loss of cell binding sites caused by crosslinking.
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http://dx.doi.org/10.1002/jbm.a.35554DOI Listing
January 2016

UV-curable nanocomposite based on methacrylic-siloxane resin and surface-modified TiO2 nanocrystals.

ACS Appl Mater Interfaces 2015 Jul 7;7(28):15494-505. Epub 2015 Jul 7.

‡Department of Engineering for Innovation, University of Salento, Via Arnesano, I-73100 Lecce, Italy.

A novel UV-light-curable nanocomposite material formed of a methacrylic-siloxane resin loaded with 1 wt % oleic acid and 3-(trimethoxysilyl)propyl methacrylate silane (OLEA/MEMO)-coated TiO2 nanorods (NRs) has been manufactured as a potential self-curing structural coating material for protection of monuments and artworks, optical elements, and dental components. OLEA-coated TiO2 NRs, presynthesized by a colloidal chemistry route, have been surface-modified by a treatment with the methacrylic-based silane coupling agent MEMO. The resulting OLEA/MEMO-capped TiO2 NRs have been dispersed in MEMO; that is a monomer precursor of the organic formulation, used as a "common solvent" for transferring the NRs in prepolymer components of the formulation. Differential scanning calorimetry and Fourier transform infrared spectroscopy have allowed investigation of the effects of the incorporation of the OLEA/MEMO-capped TiO2 NRs on reactivity and photopolymerization kinetics of the nanocomposite, demonstrating that the embedded NRs significantly increase curing reactivity of the neat organic formulation both in air and inert atmosphere. Such a result has been explained on the basis of the photoactivity of the nanocrystalline TiO2 which behaves as a free-radical donor photocatalyst in the curing reaction, finally turning out more effective than the commonly used commercial photoinitiator. Namely, the NRs have been found to accelerate the cure rate and increase cross-linking density, promoting multiple covalent bonds between the resin prepolymers and the NR ligand molecules, and, moreover, they limit inhibition effect of oxygen on photopolymerization. The NRs distribute uniformly in the photocurable matrix, as assessed by transmission electron microscopy analysis, and increase glass transition temperature and water contact angle of the nanocomposite with respect to the neat resin.
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http://dx.doi.org/10.1021/acsami.5b03731DOI Listing
July 2015

Cold-Curing Structural Epoxy Resins: Analysis of the Curing Reaction as a Function of Curing Time and Thickness.

Materials (Basel) 2014 Sep 22;7(9):6832-6842. Epub 2014 Sep 22.

Department of Engineering for Innovation, University of Salento, 73100 Lecce, Italy.

The curing reaction of a commercial cold-curing structural epoxy resin, specifically formulated for civil engineering applications, was analyzed by thermal analysis as a function of the curing time and the sample thickness. Original and remarkable results regarding the effects of curing time on the glass transition temperature and on the residual heat of reaction of the cold-cured epoxy were obtained. The influence of the sample thickness on the curing reaction of the cold-cured resin was also deeply investigated. A highly exothermal reaction, based on a self-activated frontal polymerization reaction, was supposed and verified trough a suitable temperature signal acquisition system, specifically realized for this measurement. This is one of the first studies carried out on the curing behavior of these peculiar cold-cured epoxy resins as a function of curing time and thickness.
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http://dx.doi.org/10.3390/ma7096832DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5456125PMC
September 2014

A Perspective on the Prowaste Concept: Efficient Utilization of Plastic Waste through Product Design and Process Innovation.

Materials (Basel) 2014 Jul 23;7(7):5385-5402. Epub 2014 Jul 23.

CETMA Consortium, S.S.7 Km.706+030, 72100 Brindisi, Italy.

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.
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http://dx.doi.org/10.3390/ma7075385DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5455834PMC
July 2014

Microgel Modified UV-Cured Methacrylic-Silica Hybrid: Synthesis and Characterization.

Materials (Basel) 2013 Sep 6;6(9):3805-3825. Epub 2013 Sep 6.

Department of Engineering for Innovation, University of Salento, 73100 Lecce, Italy.

An innovative photopolymerizable microgel modified UV-cured acrylic-silica hybrid formulation was developed and characterized for possible use as protective coating for different substrates. A deep investigation, aiming at providing a strong scientific basis for the production of organic-inorganic (O-I) hybrids exhibiting phase co-continuity, was firstly carried out. The O-I hybrid first proposed in this study was obtained from organic precursors with a high siloxane content, which are mixed with tetraethoxysilane (TEOS) in such a way to produce co-continuous silica nanodomains dispersed within the crosslinked organic phase, as a result of the sol-gel process. The first part of the research deals with the selection and optimization of suitable systems through appropriate chemical modifications, in order to ensure that curing reactions can be carried out at room temperature and in the presence of UV radiation. Firstly, the silica domains are formed, followed by crosslinking reactions of the acrylic groups in the oligomer via a free radical polymerization. The crosslinking reaction was controlled with the use of a suitable photoinitiator. Most of the experimental work was devoted to understanding the morphology of the hybrid system, both in uncured and cured states, and to assess its final thermal and optical properties, using different experiential techniques.
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http://dx.doi.org/10.3390/ma6093805DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5452670PMC
September 2013

Recycling of PET bottles as fine aggregate in concrete.

Waste Manag 2010 Jun 21;30(6):1101-6. Epub 2010 Feb 21.

Department of Engineering for Innovation, University of Salento, Via per Monteroni, 73100 Lecce, Italy.

An attempt to substitute in concrete the 5% by weight of fine aggregate (natural sand) with an equal weight of PET aggregates manufactured from the waste un-washed PET bottles (WPET), is presented. The WPET particles possessed a granulometry similar to that of the substituted sand. Specimens with different cement content and water/cement ratio were manufactured. Rheological characterization on fresh concrete and mechanical tests at the ages of 28 and 365days were performed on the WPET/concretes as well as on reference concretes containing only natural fine aggregate in order to investigate the influence of the substitution of WPET to the fine aggregate in concrete. It was found that the WPET concretes display similar workability characteristics, compressive strength and splitting tensile strength slightly lower that the reference concrete and a moderately higher ductility.
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http://dx.doi.org/10.1016/j.wasman.2010.01.030DOI Listing
June 2010