Publications

Publications


  • Multifunctional glass fiber/polyamide composites with thermal energy storage/release capability 2018

    Fredi, G.; Dorigato, A.; Pegoretti, A., "Multifunctional glass fiber/polyamide composites with thermal energy storage/release capability" in EXPRESS POLYMER LETTERS, v. 12, n. 4 (2018), p. 349-364. - URL: http://www.expresspolymlett.com/ . - DOI: 10.3144/expresspolymlett.2018.30

    Thermoplastic composite laminates with thermal energy storage (TES) capability were prepared by combining a glass fabric, a polyamide 12 (PA12) matrix and two different phase change materials (PCMs), i.e. a paraffinic wax microencapsulatedin melamine-formaldehyde shells and a paraffin shape stabilized with carbon nanotubes. The melt flow index ofthe PA12/PCM blends decreased with the PCM concentration, especially in the systems with shape stabilized wax. Differentialscanning calorimetry showed that, for the matrices with microcapsules, the values of enthalpy were approximatelythe 70% of the theoretical values, which was attributed to the fracture of some microcapsules. Nevertheless, most of the energystorage capability was preserved. On the other hand, much lower relative enthalpy values were measured on the compositeswith shape stabilized wax, due to a considerable paraffin leakage or degradation. The subsequent characterization ofthe glass fabric laminates highlighted that the fiber and void volume fractions were comparable for all the laminates exceptfor that with the higher amount of shape stabilized wax, where the high viscosity of the matrix led to a low fiber volumefraction and higher void content. The mechanical properties of the laminates were only slightly impaired by PCM addition,while a more sensible drop of the elastic modulus, of the stress at break and of the interlaminar shear strength could be observedin the shape stabilized wax systems.

    2018 journal paper

  • Evaluation of the shape memory behavior of a poly(cyclooctene) based nanocomposite device 2018

    Dorigato, A.; Pegoretti, A., "Evaluation of the shape memory behavior of a poly(cyclooctene) based nanocomposite device" in POLYMER ENGINEERING AND SCIENCE, v. 58, n. 3 (2018), p. 430-437. - URL: https://onlinelibrary.wiley.com/doi/abs/10.1002/pen.24590 . - DOI: 10.1002/pen.24590

    The objective of the present work is to investigate the electro-activated shape memory behavior of a polycyclooctene (PCO) based nanocomposite device. At this aim, carbon black (CB) and exfoliated graphite nanoplatelets (xGnP) were melt compounded with a PCO matrix crosslinked with a dicumylperoxide content of 2 wt% and a total filler amount of 4 wt%. Electrical resistivity measurements on bulk materials evidenced a noticeable decrease of the electrical resistivity upon CB addition, while no synergistic effects were detected mixing CB and xGnP. Nanocomposite with a CB amount of 4 wt% revealed also a noticeable heating capability through Joule effect for voltage levels higher than 100 V. The subsequent characterization of an electro active shape memory device based on this composition demonstrated how it is possible to prepare a shape memory nanocomposite material able to completely recover its original shape after 100 s with a voltage of 90 V. The retention of the shape memory behavior after several (50) programming cycles was also demonstrated. © 2017 Society of Plastics Engineers

    2018 journal paper

  • Multifunctional epoxy/carbon fiber laminates for thermal energy storage and release 2018

    Fredi, Giulia; Dorigato, Andrea; Fambri, Luca; Pegoretti, Alessandro, "Multifunctional epoxy/carbon fiber laminates for thermal energy storage and release" in COMPOSITES SCIENCE AND TECHNOLOGY, v. 158, (2018), p. 101-111. - URL: https://www.sciencedirect.com/science/article/pii/S0266353817325939 . - DOI: 10.1016/j.compscitech.2018.02.005

    This work is focused on the preparation and characterization of novel multifunctional structural composites with thermal energy storage (TES) capability. Structural laminates were obtained by combining an epoxy resin, a paraffinic phase change material (PCM) stabilized with carbon nanotubes (CNTs), and reinforcing carbon fibers. The stabilized paraffin kept its ability to melt and crystallize in the laminates, and the melting enthalpy of the composites was proportional to the paraffin weight fraction with a maximum value of 47.4 J/cm3. This thermal response was preserved even after fifty consecutive heatingcooling cycles. Moreover, the thermal conductivity of the laminates through thickness direction resulted to increase proportionally to the content of CNT-stabilized PCM. The capability of the developed TES laminates to contribute to the thermal energy management was also proven by monitoring their cooling rates through thermal imaging. The flexural modulus was only slightly affected by the presence of the PCM, while a decrease of flexural strength, strain at break and interlaminar shear strength was detected. Optical microscopy highlighted that this could be attributed to the preferential location of the PCM in the interlaminar region. The obtained results demonstrated the feasibility of the concept of multifunctional structural TES composites. ©2018 Elsevier Ltd. All rights reserved.

    2018 journal paper

  • Thermoplastic Polyurethane Blends With Thermal Energy Storage/Release Capability 2018

    Dorigato, A; Rigotti, D; Pegoretti, A, "Thermoplastic Polyurethane Blends With Thermal Energy Storage/Release Capability" in FRONTIERS IN MATERIALS, v. 2018, n. 5 (2018), p. 1-10. - URL: https://www.frontiersin.org/articles/10.3389/fmats.2018.00058/full . - DOI: 10.3389/fmats.2018.00058

    In this work innovative thermal energy storage materials were developed by encapsulating a paraffin having a melting temperature of 6 degrees C (M6D) in a thermoplastic polyurethane (TPU), and the most important physical properties of the resulting samples were investigated from a thermo-mechanical point of view. Field emission scanning electron microscope (FESEM) micrographs demonstrated a homogeneous microcapsules distribution and good interfacial adhesion with the TPU matrix even at elevated M6D concentrations. With a capsule concentration of 60 wt% it was possible to obtain elevated melting enthalpy values (up to 95 J/g), retaining the energy storage/release properties even after 50 thermal cycles. The hardness and the dimensional stability of the TPU matrix above its glass transition temperature were strongly increased upon M6D addition, but this stiffening effect was associated to a certain embrittlement. The investigated blends could be applied for winter sport application for low temperature thermal energy storage/release materials.

    2018 journal paper

  • 3D printable thermoplastic polyurethane blends with thermal energy storage/release capabilities 2018

    Rigotti, D.; Dorigato, A.; Pegoretti, A., "3D printable thermoplastic polyurethane blends with thermal energy storage/release capabilities" in MATERIALS TODAY COMMUNICATIONS, v. 15, (2018), p. 228-235. - URL: http://www.journals.elsevier.com/materials-today-communications/ . - DOI: 10.1016/j.mtcomm.2018.03.009

    The aim of this work was to develope novel 3D printable thermoplastic polyurethane (TPU) blends with thermalenergy storage (TES) capabilities. The target are potential applications for winter sport equipment. Differentamounts of an encapsulated paraffin were added to a TPU matrix, and the resulting blends were then used toproduce 3D printed samples. FESEM observation evidenced a homogeneous distribution of the capsules in thepolymer matrix and a good adhesion between the layers in the 3D printed parts. DSC tests indicated that aneffective energy storage/release capability was obtained in the 3D printed parts, with melting enthalpy values upto 70 J/g. The hard shells of the microcapsules, made of melamine formaldehyde resin, induced an increase ofthe stiffness, of the creep stability and of the Shore A hardness of the material, accompanied by a decrease of theelongation at break.

    2018 journal paper

  • Synergistic effects of carbon black and carbon nanotubes on the electrical resistivity of poly(butylene-terephthalate) nanocomposites 2018

    Dorigato, Andrea; Brugnara, Marco; Pegoretti, Alessandro, "Synergistic effects of carbon black and carbon nanotubes on the electrical resistivity of poly(butylene-terephthalate) nanocomposites" in ADVANCES IN POLYMER TECHNOLOGY, v. 37, n. 6 (2018), p. 1744-1754. - URL: https://onlinelibrary.wiley.com/doi/abs/10.1002/adv.21833 . - DOI: 10.1002/adv.21833

    In this study, novel electrically conductive polymeric nanocomposites based on polybutylene terephthalate (PBT) filled with commercial carbon black (CB) and carbon nanotubes (CNTs) at different relative ratios have been investigated. Field emission scanning electron microscope (FESEM) analysis revealed how a good nanofiller dispersion was obtained both by introducing CB and CNT. Melt flow index measurements highlighted that the processability of the nanocomposites was heavily compromised at elevated filler amounts, and the viscosity percolation threshold was established at 3 wt% for CNTs and between 6 and 10 wt% for CB nanocomposites. Differential scanning calorimetry (DSC) measurements evidenced how the presenceof CNT slightly increased the glass transition temperature of the materials, and an increase of 12°C of the crystallization temperature was obtained with a CNT amount of 6 wt%. Also the crystalline fraction was increased upon CNT addition. Electrical resistivity measurements evidenced that the most interesting results were obtained for nanocomposites with a total filler content of 6 wt% and a CNT/CB relative amount equal to 2:1. The synergistic effect obtained with the combination of both nanofillers allowed the achievement of a rapid surface heating through Joule effect even at applied voltages of 2 V.

    2018 journal paper

  • Ultrathin wood laminae-polyvinyl alcohol biodegradable composites 2018

    Dorigato, Andrea; Negri, Martino; Pegoretti, Alessandro, "Ultrathin wood laminae-polyvinyl alcohol biodegradable composites" in POLYMER COMPOSITES, v. 39, n. 4 (2018), p. 1116-1124. - URL: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1548-0569 . - DOI: 10.1002/pc.24040

    Novel polyvinyl alcohol (PVOH) based biodegradablecomposites were prepared by a hand lay-up processusing ultrathin beech laminae cut by a specializedplaner machine, and the resulting materials werethermo-mechanically characterized. Density measuredshowed how the adopted procedure led to laminateshaving a high porosity degree (about 50% by volume)and an elevated wood concentration (about 80% byweight). In fact, because the wood fibers were perfectlycut (not pressed and abraded), wood porositywas partially filled by the PVOH resin, as documentedby field emission scanning electron microscope(FESEM) micrographs. The occlusion of wood porosityby the PVOH matrix resulted to be beneficial for thetensile mechanical properties of the composites. Infact, quasi-static tensile tests and DMTA analysisrevealed how the stiffness (E, E0) and strength (rb) valuesof the composites both along longitudinal andtransversal directions were considerably higher thanthose of the constituents. On the other hand, the valuesof the specific energy adsorbed under impact conditionsby the composites samples were rather low,if compared to the neat matrix.

    2018 journal paper

  • Combined effect of fumed silica and metal hydroxides as fire retardants in PE single-polymer composites 2018

    Fredi, Giulia; De Col, A; Dorigato, A; Lopez-Cuesta, J-M; Fambri, L; Pegoretti, A, "Combined effect of fumed silica and metal hydroxides as fire retardants in PE single-polymer composites" in AIP Conference Proceedings, Melville, NY, USA: American Institute of Physics Inc., 2018, p. 020021-1-020021-4. - (AIP CONFERENCE PROCEEDINGS). - ISBN: 9780735416970. Proceedings of: 9th International Conference on Times of Polymers and Composites: From Aerospace to Nanotechnology, Ischia, Naples; Italy, 17–21 June, 2018. - URL: http://scitation.aip.org/content/aip/proceeding/aipcp . - DOI: 10.1063/1.5045883

    This work aimed to study the combined effect of metal hydroxides and fumed silica in enhancing the fire-retardant properties of a polyethylene single-polymer composite. The LLDPE matrix was blended with fumed silica and aluminum or magnesium hydroxides in different weight fractions. The obtained matrices were characterized to select that with the best combination of processability, mechanical and thermal properties, and fire resistance, to produce a single-polymer composite (SPC). The current research is focusing on the selection of the processing parameters for the production of the SPC, and on the characterization of the obtained laminates.

    2018 conference paper

  • Novel phase change materials using thermoplastic composites 2018

    Dorigato, A; Fredi, G; Pegoretti, A, "Novel phase change materials using thermoplastic composites" in AIP Conference Proceedings, Melville, NY, USA: American Institute of Physics Inc., 2018, p. 020044-1-020044-4. - (AIP CONFERENCE PROCEEDINGS). - ISBN: 9780735416970. Proceedings of: 9th International Conference on Times of Polymers and Composites: From Aerospace to Nanotechnology, Ischia, Naples; Italy, 17-21 June 2018. - URL: http://scitation.aip.org/content/aip/proceeding/aipcp . - DOI: 10.1063/1.5045906

    In this work a Polyamide 12 (PA12) matrix was melt compounded with different amounts of discontinuous carbon fibers with different length and encapsulated paraffin, in order to develop novel thermoplastic composites with thermal energy storage/release capability. The microstructural, thermal and mechanical properties of the resulting materials were investigated. SEM images demonstrated how a rather good fiber matrix adhesion was obtained both by using long and short carbon fibers, while the microcapsules seem to be partially damaged by melt compounding operations and present also an interfacial debonding. DSC tests revealed how the melting enthalpy increased with the capsules amount, but the thermal energy storage/release capability of the composites was limited by the partial breakage of the microcapsules and the consequent molten paraffin leakage within the material. The introduction of microcapsules in the PA12 matrix determined an evident decrease of the elastic modulus, of the stress at yield and of the deformation at break, even when carbon fiber reinforcement was present, probably because of the limited interfacial adhesion between PA12 matrix and the microcapsules.

    2018 conference paper

  • Novel polyamide 12 based nanocomposites for industrial applications 2017

    Dorigato, Andrea; Brugnara, Marco; Pegoretti, Alessandro, "Novel polyamide 12 based nanocomposites for industrial applications" in JOURNAL OF POLYMER RESEARCH, v. 24, n. 6 (2017), p. 1-13. - URL: https://link.springer.com/article/10.1007/s10965-017-1257-9 . - DOI: 10.1007/s10965-017-1257-9

    In this paper novel electro-active polyamide 12 (PA12) based nanocomposites were prepared though melt compounding by adding different kinds of carbonaceous nanofillers. The thermo-electrical properties of the bulk samples were then compared with those of the corresponding fibers. FESEM images highlighted an homogenous dispersion of carbon black (CB) and carbon nanofibers (CNF) within the matrix, while exfoliated graphite nanoplatelets (xGnP) based nanocomposites showed an aggregated morphology. A slight increase of the glass transition and of the crystallization temperature was evidenced by DSC tests, while thermogravimetric analysis showed an improvement of the thermal degradation resistance. Nanofiller addition promoted substantial increments of the elastic modulus coupled with an electrical resistivity drop up to 103 Ω cm, with interesting synergistic effects for nanocomposites filled with both CB and CNF. FESEM micrographs on the fibers demonstrated how the drawing process promoted the breakage of CB aggregates and their alignment along the drawing direction, leading to an increase of both the elastic and failure properties with respect to the neat fibers. On the other hand, nanofiller orientation led to an electrical resistivity enhancement of two orders of magnitude with respect to the corresponding bulk materials, and a CB amount of 10 wt% was thus required to observe a sensible fiber heating upon voltage application.

    2017 journal paper

  • Phase changing nanocomposites for low temperature thermal energy storage and release 2017

    Dorigato, Andrea; Canclini, P.; Unterberger, S. H.; Pegoretti, Alessandro, "Phase changing nanocomposites for low temperature thermal energy storage and release" in EXPRESS POLYMER LETTERS, v. 11, n. 9 (2017), p. 738-752. - URL: http://www.expresspolymlett.com/letolt.php?file=EPL-0008111&mi=c . - DOI: 10.3144/expresspolymlett.2017.71

    The aim of this paper is to develop new elastomeric phase change materials (PCM) for the thermal energystorage/release below room temperature. In particular, poly(cyclooctene) (PCO)/paraffin blends filled with various concentrationsof carbon nanotubes (CNTs), were prepared by a melt compounding process. The microstructural, thermo-mechanicaland electrical properties of the resulting materials were investigated.The microstructure of these materials was characterized by the presence of paraffin domains inside the PCO, and CNTs werelocated only inside the paraffin domains in forms of aggregated clusters. DSC tests evidenced the existence of two distinctcrystallization peaks at –10 and at 6 °C, respectively associated to the paraffin and the PCO phases, indicating that both thepolymeric constituents are thermally active below room temperature. Moreover, CNT addition did not substantially alterthe melting/crystallization properties of the material. Noticeable improvements of the mechanical properties and of the electricalconductivity with respect to the neat PCO/paraffin blend could be obtained upon CNT addition, and also thermal conductivity/diffusivity values were considerably enhanced above the percolation threshold. Finite element modeling demonstratedthe efficacy of the prepared nanocomposites for applications in the thermal range from –30 to 6 °C.

    2017 journal paper

  • Electrically conductive nanocomposites for fused deposition modelling 2017

    Dorigato, A; Moretti, V.; Dul, S.; Unterberger, S. H.; Pegoretti, A., "Electrically conductive nanocomposites for fused deposition modelling" in SYNTHETIC METALS, v. 2017, 226, (2017), p. 7-14. - URL: https://www.sciencedirect.com/science/article/abs/pii/S0379677917300097 . - DOI: 10.1016/j.synthmet.2017.01.009

    An acrylonitrile-butadiene-styrene (ABS) matrix was melt compounded with various amounts (from 1 to 8 wt%) of multi-walled carbon nanotubes (MWCNT) predispersed in an ABS carrier. The resulting materials were then i) compression molded (CM) to obtain plaques or ii) extruded infilaments used to feed a fused deposition modelling (FDM) machine. 3D printed samples were obtained under three different orientations.The nanofiller addition within the ABS matrix caused a remarkable increase of both stiffness and stress at yield of the bulk samples, accompanied by a strong reduction of the elongation at break. The mechanical properties of 3D printed samples resulted to be strongly dependent on the printingorientation. The addition of CNTs was very effective in improving the electrical conductivity with respect to neat ABS even at the smallestfiller content. The FDM process determined a partial loss in the electrical conductivity of ABS nanocomposites, with a marked dependency on the printing orientation. For CNT amounts higher than 4 wt%, CM samples manifested a rapid heating by Joule effect, while the process was less efficient in the printed samples. CNT addition has high impact on thermal properties, resulting in a decrease of specific heat and a increase of thermal diffusivity and conductivity. Like observed for electric conductivity FDM also influences properties of thermal diffusivity and conductivity, resulted by a possible orientation of CNT. © 2017 Elsevier B.V. All rights reserved.

    2017 journal paper

  • POLYETHYLENE WAX/EPDM BLENDS AS SHAPE-STABILIZED PHASE CHANGE MATERIALS FOR THERMAL ENERGY STORAGE 2017

    Dorigato, Andrea; Ciampolillo, M. V.; Cataldi, Annalisa; Bersani, M.; Pegoretti, Alessandro, "POLYETHYLENE WAX/EPDM BLENDS AS SHAPE-STABILIZED PHASE CHANGE MATERIALS FOR THERMAL ENERGY STORAGE" in RUBBER CHEMISTRY AND TECHNOLOGY, v. 90, n. 3 (2017), p. 575-584. - DOI: 10.5254/rct.82.83719

    Various amounts of a paraffinic wax were dispersed by melt mixing in an ethylene/propylene diene monomers (EPDM) rubber matrix. The resulting compounds were then vulcanized to obtain shape-stabilized rubbery phase change materials for thermal energy storage. The addition of the paraffinic wax induced a retardation in the vulcanization kinetics of the EPDM matrix. Calorimetric measurements evidenced how the homogenous distribution of the wax domains within the rubber, confirmed by electron microscopy observations, allowed for retaining the melting enthalpy of the neat paraffinic wax even at elevated concentration. The thermal energy storage and release capabilities of the investigated compounds were maintained even after various thermal cycles. The incorporation of polyethylene wax had a positive effect (increasing proportionally to its content) on the mechanical properties of the EPDM matrix, as documented from both the dynamical and the quasi-static tensile tests.

    2017 journal paper

  • Fatigue behaviour of biocomposites 2017

    Pegoretti, A; Dorigato, A., "Fatigue behaviour of biocomposites" in Luigi Ambrosio (edited by), Biomedical Composites - Second Edition, Duxford, UK: Elsevier /Woodhead Publishing Ltd, 2017, p. 431-478. - ISBN: 978-0-08-100752-5. - URL: https://www.elsevier.com/books/biomedical-composites/ambrosio/978-0-08-100752-5

    2017 chapter

  • Wax confinement with carbon nanotubes for phase changing epoxy blends 2017

    Fredi, Giulia; Dorigato, Andrea; Fambri, Luca; Pegoretti, Alessandro, "Wax confinement with carbon nanotubes for phase changing epoxy blends" in POLYMERS, v. 2017, n. 9 (2017), p. 1-16. - URL: http://www.mdpi.com/2073-4360/9/9/405/pdf . - DOI: 10.3390/polym9090405

    A paraffin wax was shape stabilized with 10 wt % of carbon nanotubes (CNTs) and dispersed in various concentrations in an epoxy resin to develop a novel blend with thermal energy storage capabilities. Thermogravimetric analysis showed that CNTs improve the thermal stability of paraffin, while differential scanning calorimetry showed that the paraffin kept its ability to melt and crystallize, with enthalpy values almost proportional to the paraffin fraction. In contrast, a noticeable loss of enthalpy was observed for epoxy/wax blends without CNTs, which was mainly attributed to the partial exudation of paraffin out of the epoxy matrix during the curing phase. Dynamic mechanical thermal analysis contributed to elucidate the effects of the melting of the paraffin phase on the viscoelastic properties of the epoxy blends. Flexural elastic modulus and strength of the blends decreased with the wax/CNT content according to a rule of mixtures, while flexural strain at break values deviate positively from it. These results show the potentialities of the investigated epoxy blends for the development of multifunctional structural composites.

    2017 journal paper

  • Effects of carbonaceous nanofillers on the mechanical and electrical properties of crosslinked poly(cyclooctene) 2017

    Dorigato, Andrea; Pegoretti, Alessandro, "Effects of carbonaceous nanofillers on the mechanical and electrical properties of crosslinked poly(cyclooctene)" in POLYMER ENGINEERING AND SCIENCE, v. 57, n. 5 (2017), p. 537-543. - URL: https://onlinelibrary.wiley.com/doi/abs/10.1002/pen.24449 . - DOI: 10.1002/pen.24449

    In this work the mechanical and electrical behavior of poly(cyclooctene) (PCO)-based nanocomposites were investigated. At this aim, different amounts (0.5–4 wt%) of carbon black (CB), carbon nanofibers (NF) and exfoliated graphite nanoplatelets (xGnP) were melt compounded with a PCO matrix and crosslinked with dicumylperoxide (DCP). The progressive increase of the DCP concentration led to an evident decrease of both the melting temperature and the crystallization temperature, and also the relative crystallinity was strongly reduced. Microstructural observations on nanocomposites materials with a DCP amount of 2 wt% evidenced how CB nanocomposites were characterized by a good nanofiller dispersion within the matrix, while NF and xGnP nanofilled samples presented a more aggregated morphology. The introduction of CB and xGnP determined an enhancement of the elastic modulus of the material, without impairing the ultimate properties of the pristine matrix. Electrical resistivity measurements evidenced how the prepared composites can be interesting as electro-active materials for CB concentrations higher than 2 wt%. © 2016 Society of Plastics Engineers

    2017 journal paper

  • Effects of the extrusion processes on the rheological, chemical, and coloration properties of a copper phthalocyanine-based masterbatch 2017

    Buccella, M; Dorigato, A; Rizzola, F; Caldara, M; Fambri, L, "Effects of the extrusion processes on the rheological, chemical, and coloration properties of a copper phthalocyanine-based masterbatch" in THE JOURNAL OF ELASTOMERS AND PLASTICS, v. 2017, (2017), p. 1-17. - URL: http://journals.sagepub.com.ezp.biblio.unitn.it/doi/pdf/10.1177/0095244317718597 . - DOI: 10.1177/0095244317718597

    The production process of a monodispersed blue masterbatch for the coloration of thecarpet filaments, constituted by a polyamide 6 (PA6) resin and a copper blue phthalocyaninepigment, was investigated and optimized. It was found that a compoundingprocess based on three extrusions without any subsequent filtration was the best way toachieve a fine pigment dispersion within the PA6 matrix, with a filter pressure valuereduction of 50% and a relative color strength increase of about 10% with respect to thestandard production process (i.e. a single extrusion). Rheological tests, viscosity measurementsand end groups analyses were used to determine the thermal stability of theprepared compounds. It was found that the triple extrusion promoted thermo-oxidativereactions. This innovative process setup can reduce the production waste, increasing theproductivity and the quality of the final product without compromising the rheologicalproperties of the monodispersed masterbatches.

    2017 journal paper

  • Mechanical behaviour of cyclic olefin copolymer/exfoliated graphite nanoplatelets nanocomposites foamed by supercritical carbon dioxide 2016

    Biani, A.; Dorigato, Andrea; Bonani, Walter; Slouf, Miroslav; Pegoretti, Alessandro, "Mechanical behaviour of cyclic olefin copolymer/exfoliated graphite nanoplatelets nanocomposites foamed by supercritical carbon dioxide" in EXPRESS POLYMER LETTERS, v. 10, n. 12 (2016), p. 977-989. - URL: http://www.expresspolymlett.com/letolt.php?file=EPL-0007313&mi=c . - DOI: 10.3144/expresspolymlett.2016.91

    A cycloolefin copolymer matrix was melt mixed with exfoliated graphite nanoplatelets (xGnP) and the resultingnanocomposites were foamed by supercritical carbon dioxide. The density of the obtained foams decreased with the foamingpressure. Moreover, xGnP limited the cell growth during the expansion process thus reducing the cell diameter (from 1.08to 0.22 mm with an XGnP amount of 10 wt% at 150 bar) and increasing the cell density (from 12 to 45 cells/mm2 with ananofiller content of 10 wt% at 150 bar). Electron microscopy observations of foams evidenced exfoliation and orientationof the nanoplatelets along the cell walls. Quasi-static compressive tests and tensile creep tests on foams clearly indicatedthat xGnP improved the modulus (up to a factor of 10 for a xGnP content of 10 wt%) and the creep stability.

    2016 journal paper

  • Cyclic olefin copolymer–silica nanocomposites foams 2016

    Pegoretti, Alessandro; Dorigato, Andrea; Biani, Andrea; Slouf, Miroslav, "Cyclic olefin copolymer–silica nanocomposites foams" in JOURNAL OF MATERIALS SCIENCE, v. 51, n. 8 (2016), p. 3907-3916. - URL: http://link.springer.com/journal/10853 . - DOI: 10.1007/s10853-015-9710-9

    A cyclic olefin copolymer (COC) matrix wasmelt compounded with various amounts of fumed silicananoparticles (1, 3 and 5 vol%) and the resulting materialswere foamed through supercritical carbon dioxide. Foamswere produced at four different foaming pressures (90, 110,130, and 150 bar), keeping all other processing parametersconstant. The main physical properties of both bulk andfoamed samples were investigated in order to assess therole of both nanofiller content and foaming pressure. It wasobserved that the density values of the foamed materialsdecreased as the foaming pressure increased and that thepresence of nanofillers leads to slightly denser materials.Both scanning and transmission electron microscopy evidencedthe presence of filler aggregates on the bulk composites.These aggregates resulted to be elongated along thecell wall direction upon foaming. Dynamic mechanicalthermal analysis, quasi-static tensile tests, and creep testsevidenced a positive effect played by nanosilica inimproving the stiffness, the strength, and the creep stabilityof the polymer matrix for all foaming pressures. Theapplication of a theoretical model for closed-cell foamshighlighted how the stiffening effect provided by thenanosilica networking is mostly effective at elevated filleramounts and reduced foaming pressure values.

    2016 journal paper

  • Thermal and mechanical behavior of innovative melt-blown fabrics based on polyamide nanocomposites 2016

    Dorigato, Andrea; Brugnara, Marco; Giacomelli, Gianmarco; Fambri, Luca; Pegoretti, Alessandro, "Thermal and mechanical behavior of innovative melt-blown fabrics based on polyamide nanocomposites" in JOURNAL OF INDUSTRIAL TEXTILES, v. 45, n. 6 (2016), p. 1504-1515. - URL: http://jit.sagepub.com . - DOI: 10.1177/1528083714564633

    A commercial organo-modified clay (OMC) was added to a polyamide 6 (PA6) matrix atvarious concentrations during the polymerization stage or by melt compounding in atwin-screw extruder, and the resulting pellets were used for the production of depthfilters in the shape of cylindrical nonwoven webs through a melt-blown process. Theprocessability of the investigated materials was significantly affected by nanofiller introduction.Differential scanning calorimetry revealed that OMCs play a nucleating effecton the crystallization of the polyamide matrix, with a remarkable increase in the crystallizationtemperature on cooling from the melt. Consequently, a parameter related tothe filtering performances of the web, such as the pressure drop (P) evaluated oncylindrical filters, decreased with the increase in die-to-collector distance in a morepronounced way for nanocomposite nonwovens. This behavior was related to thesignificant decrease of the connecting points in the networks due to the rapid coolingof the filaments on the collecting mandrel. Compressive mechanical tests evidencedhow organoclay addition led to a remarkable increase of the rigidity of the web, whenthe data were compared at the same P value, irrespectively from the preparationtechnique.

    2016 journal paper

  • Influence of the Processing Parameters on the Dispersion and Coloration Behavior of a Halogenated Copper Phthalocyanine-Based Masterbatch 2016

    Buccella, Mauro; Dorigato, Andrea; Rizzola, Fabio; Caldara, Mauro; Fambri, Luca, "Influence of the Processing Parameters on the Dispersion and Coloration Behavior of a Halogenated Copper Phthalocyanine-Based Masterbatch" in ADVANCES IN POLYMER TECHNOLOGY, v. 2016, (2016), p. 1-8. - URL: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1098-2329 // http://onlinelibrary.wiley.com.ezp.biblio.unitn.it/doi/10.1002/adv.21721/epdf . - DOI: 10.1002/adv.21721

    A monodispersed green masterbatch was produced through an industrial extrusion process, by mixing a commer-cial Polyamide 6 matrix (PA6) with a halogenated copper phthalocyanine green pigment. The production process was investigatedand optimized in order to improve the pigment dispersion, reducing the clogging power and increasing the color strength of theresulting products. The compounding process based on three extrusions without filtration led to a filter pressure value (FPV)reduction of about 84% and a relative color strength (RCS) increase of about 50% with respect to the standard production process(i.e single extrusion). The thermal stability of the prepared compounds was evaluated by rheological test, viscosity measurements,and end group analysis, and it was found that a triple extrusion without filtration promoted thermo-oxidative matrix degradation.However, the same processing conditions led to a significant reduction of the production waste, increasing the productivity andthe quality of the final product.

    2016 journal paper

  • Innovative microcrystalline cellulose composites as lining adhesives for canvas 2015

    Cataldi, Annalisa; Dorigato, Andrea; Deflorian, Flavio; Pegoretti, Alessandro, "Innovative microcrystalline cellulose composites as lining adhesives for canvas" in POLYMER ENGINEERING AND SCIENCE, v. 55, n. 6 (2015), p. 1349-1354. - URL: https://onlinelibrary.wiley.com/doi/10.1002/pen.24074 . - DOI: 10.1002/pen.24074

    Thin adhesive composite films were prepared by meltcompounding and compression molding of a thermoplastic resin (ParaloidVR B72) widely used for art protection and restoration with a microcrystalline cellulose powder (MCC). To simulate an oil painting restoration work, MCC-based composites were applied as lining adhesives on two kinds of canvases (English linen and woven polyester). Interestingly, single–lap shear tests both in quasi-staticand creep conditions showed a remarkable stabilizing effect provided by MCC addition. Post-mortem microstructural analysis of the overlap adhesive area proved how MCC introduction did not change the fracture behavior of the bonded joints. The visual assessment of transparency and color measurements evidenced a chromatic variation of MCC-based films with a filler amount of 30 wt%, while, UV-vis analysis showed a decrease of relative transmittance in proportion to the MCC content. Additionally, rheological tests highlighted a viscosity increase for Paraloid B72 in both dry and wet conditions (T523C and RH5of 55%) as the MCC content increases. © 2015 Society of Plastics Engineers

    2015 journal paper

  • Liquid crystalline polymer nanocomposites reinforced with in-situ reduced graphene oxide 2015

    Pedrazzoli, Diego; Dorigato, Andrea; Conti, T.; Vanzetti, L.; Bersani, M.; Pegoretti, Alessandro, "Liquid crystalline polymer nanocomposites reinforced with in-situ reduced graphene oxide" in EXPRESS POLYMER LETTERS, v. 9, n. 8 (2015), p. 709-720. - URL: http://www.expresspolymlett.com/letolt.php?file=EPL-0005975&mi=c . - DOI: 10.3144/expresspolymlett.2015.66

    In this work liquid-crystalline polymer (LCP) nanocomposites reinforced with in-situ reduced graphene oxide are investigated. Graphene oxide (GO) was first synthesized by the Hummers method, and the kinetics of its thermal reduction was assessed. GO layers were then homogeneously dispersed in a thermotropic liquid crystalline polymer matrix (Vectran ®), and an in-situ thermal reduction of GO into reduced graphene oxide (rGO) was performed. Even at low rGO amount, the resulting nanocomposites exhibited an enhancement of both the mechanical properties and the thermal stability.Improvements of the creep stability and of the thermo-mechanical behavior were also observed upon nanofiller incorporation. Furthermore, in-situ thermal reduction of the insulating GO into the more electrically conductive rGO led to an important surface resistivity decrease in the nanofilled samples.

    2015 journal paper

  • Coloration properties and chemo-rheological characterization of a dioxazine pigment-based monodispersed masterbatch 2015

    Buccella, M.; Dorigato, A.; Crugnola, F.; Caldara, M.; Fambri, L., "Coloration properties and chemo-rheological characterization of a dioxazine pigment-based monodispersed masterbatch" in JOURNAL OF APPLIED POLYMER SCIENCE, v. 132, n. 7 (2015), p. 1-7. - URL: http://onlinelibrary.wiley.com/doi/10.1002/app.41452/abstract . - DOI: 10.1002/app.41452

    A dioxazine-based color pigment was added to a commercial polyamide 6 (PA6) through an extrusion process, in order to prepare monoconcentrated violet masterbatches through different production set-up. A detailed characterization of the resulting materials was carried out in order to find the best processing parameters combination to optimize pigment dispersion and to reduce the clogging power. The preparation of masterbatches with repeated extrusions markedly reduced the filter pressure value and increased the Relative Color Strength, while filtration did not significantly influence pigment dispersion. Rheological measurements and end-groups analysis were conducted on the same materials with the aim to evaluate their thermal degradation resistance, and the thermal stability of the compounds was retained even upon three extrusions. Therefore, it can be concluded that a proper optimization of the process parameters could lead to an important reduction of the production waste, increasing the quality of the final product

    2015 journal paper

  • Thermo-mechanical properties of innovative microcrystalline cellulose filled composites for art protection and restoration 2014

    Cataldi A; Dorigato A; Deflorian F; Pegoretti A., "Thermo-mechanical properties of innovative microcrystalline cellulose filled composites for art protection and restoration" in JOURNAL OF MATERIALS SCIENCE, v. 49, n. 5 (2014), p. 2035-2044. - DOI: 10.1007/s10853-013-7892-6

    Microcrystalline cellulose (MCC) powder was selected as a natural reinforcement for a commercial acrylic adhesive widely used in the field of art protection and restoration (Paraloid B72). In particular, various amounts (from 5 to 30 wt%) of MCC were melt compounded with Paraloid B72 to prepare new thermoplastic polymer composites for the cultural heritage conservation field. Scanning electron microscopy showed that MCC flakes are uniformly dispersed within the matrix at allthe tested compositions, without preferential orientation. Thermogravimetric analysis evidenced an increase of thermal stability due to the MCC introduction, even at low filler amounts, while DSC measurements demonstrated that the glass transition temperature progressively increases with the MCC content. Interestingly, DMTA analysis revealed a stabilizing effect on the material produced by microcellulose addition, with an increase of the storage modulus and a decrease of the thermal expansion coefficient, in proportion to the filler loading. Moreover, MCC addition determined an increase of the elastic modulus and creep stability with respect to the neat resin, and an enhancement of fracture toughness (KIC).

    2014 journal paper