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Entropically-driven ring-opening polymerization (ED-ROP) of strainless macrocyclic oligomers (MCOs) of condensation polymers has received a great deal of attention in the past three decades. Typical features of ED-ROP, such as no need for solvents, no emission of volatiles, practically no heat evolution, no particular need for mixing, automatic stoichiometric balance, make this process a useful synthetic tool in a variety of applications involving polymers of industrial interest. Selected examples exploiting ED-ROP of MCOs to (i) achieve multicomponent polymer materials (copolymers, blends, composites and nanocomposites), (ii) aid melt processing, (iii) enhance phase compatibility, (iv) modify material properties or (v) allow chemical recycling are reviewed.

The demand for high dielectric constant materials and high energy density capacitors has rapidly increased in recent years due to the continuous and rapid development of the electronic industry and the need to store electrostatic energy more efficiently. The introduction of ferroelectric inclusions in a polymeric matrix enables the effective dielectric constant of the composite to be significantly increased while preserving the high breakdown field typical of polymers, thus improving the stored energy density. By varying the size, shape and volume fraction of the inclusions, the dielectric properties of the composite can be tailored, as a consequence of the alteration of the electric field distribution inside the material. A further approach for the modification of the electric field in the composite is coating the particles used as inclusions with an oxide layer with a different dielectric constant. In this work we have fabricated polyvinyldene fluoride (PVDF) composites containing 30 vol.% BaTiO3@AO2 (A = Si, Ti) particles. Barium titanate particles with a diameter of ?100 nm were synthesized using a hydrothermal-like method and coated with a thin shell (10 nm) of SiO2 or TiO2 by means of colloidal chemistry methods. The composites were prepared by solution casting and subsequent compression moulding. Reference composites were prepared by the same process using uncoated BaTiO3 particles. In order to understand the effect of interfacial modification by coating of the filler, the dielectric properties of the composites (dielectric constant and loss tangent) were measured at different frequencies (1 - 106 Hz) in the temperature range 25-150 °C. The coating results in a significant modification on the effective permittivity, which is mainly determined by the value of its dielectric constant. To gain insight into the role of the coating layer, the electric field distribution and the effective dielectric constant were calculated for the different composites using a 3D finite element modelling and compared to experimental results. This study provides some guidelines for tuning the dielectric properties of ferroelectric PVDF-ceramic composites. Acknowledgements: This work was funded by Fondazione Bancaria Compagnia di San Paolo, under the framework of the Project "Polycom".

In this work, an alternative and smart approach to tune PVDF polymorphism was proposed, that is exploiting the compression moulding to induce, within the not completely molten material, internal shear stresses similar to those occurring in a rolling process. The moulding conditions were properly modified to investigate their influence on the crystalline phases obtained. The electroactive phase amount was estimated by ATR-FTIR spectroscopy, after having carried out a principal component analysis in order to verify the representativeness of the two infrared bands usually used in literature for such a calculation. A multiple linear regression was employed to evaluate the trend of the ? phase quantity as a function of the plate thickness and moulding temperature, obtaining a non-monotonous trend, due to the effects of two contrasting factors: (i) the effectiveness of compression, which increases by increasing the amount of molten polymer; (ii) the phase transition, which involves only the solid portion of the polymer bulk. Taking into account this, a series of moulding conditions was selected to prepare PVDF samples for further morphological, calorimetric, structural, dynamic-mechanical and dielectric characterization. Gathered results indicate that the processing method, by changing the polymorphism of PVDF, consequently affects the dielectric response of the polymer but also changes its ultimate properties independently from the induced crystalline phases. By hot pressing the PVDF below the melting temperature, an orienting effect (verified by polarized optical microscopy) was obtained, leading to the ? to ? phase transition and consequent increasing of the dielectric permittivity. On the other hand, the dielectric losses and the dynamic-mechanical properties appear to be not affected so much by the ? phase content but rather by a different packing of the polymer chains.

Global industry is showing great interest in the field of sustainability, thanks to the increased attention for ecological safety and utilization of renewable materials. For the scientific community the challenge lies in the identification of greener synthetic approaches and new alternatives to petroleum-based materials in order to reduce the environmental impact. In this context, we propose the preparation of novel bio-composites consisting of natural rubber latex (NRL) and sepiolite (Sep) fibers through the latex compounding technique (LCT), a more eco-friendly approach, compared to traditional melt mixing, where the filler is directly mixed with a stable aqueous elastomer colloid dispersion (latex).

The present contribution focus on eco-composites based on a commercial bio-polyester (PBAT) and high amounts of raw HFs. To promote the adhesion between the polyester matrix and the fibrous reinforcement, the fiber surface was treated with suitable coupling agents. Two different experimental strategies were explored: i) chemical modification of HFs by using PBAT macrocyclic oligomers (MCOs) as the coupling agent [1]; and ii) plasma treatment through a novel soft plasma jet device (developed by Nadir SrL) contemporary able to activate the fiber surface and deposit on it reactive monomers, such as methyl methacrylate (MMA), (3-aminopropyl)triethoxysilane (APTES), and (3-glycidyloxypropyl)trimethoxysilane (GLYMO). Unmodified and surface modified fibers were characterized and compared in terms of thermal behavior and morphological features. Long-fiber eco-composites were then prepared by a suitable compression molding procedure and characterized by thermal, morphological and dynamic-mechanical analysis.

Global industry is showing a great interest in the field of sustainability owing to the increased attention for ecological safety and utilization of renewable materials. For the scientific community, the challenge lies in the identification of greener synthetic approaches for reducing the environmental impact. In this context, we propose the preparation of novel nanocomposites (NCs) consisting of natural rubber latex (NRL) and sepiolite (Sep) fibers through the latex compounding technique (LCT), an ecofriendly approach where the filler is directly mixed with a stable elastomer colloid (1). This strategy favors a homogeneous dispersion of hydrophilic Sep fibers in the rubber matrix, allowing the production of high-loaded sepiolite/natural rubber (Sep/NR) NCs) without the use of surfactants. This process is more sustainable than melt mixing, in which the incorporation of very large amounts of filler requires significant energy input and may lead to the release of powder in the working environment, rising problems of compounding, dispersibility and contamination. The main physicochemical parameters which control aggregation processes in the aqueous medium, i.e., pH, ?-potential, size and shape of colloidal systems, and the morphological features of the final NCs were comprehensively investigated in order to figure out the interactions among Sep fibers and NR, and to propose a flocculation mechanism characteristic of each Sep/NR system. Finally, the mechanical properties of NR/Sep NCs obtained by LCT were determined by strain sweep analysis and compared to those of analogues NCs prepared by conventional melt blending

Polymer-ceramics nanocomposites are spreading in the field of printed wiring boards and microelectronic packaging because they provide an ideal solution to combine the good dielectric and electrical properties of the ceramic filler with the resistance to high electric field, the low-temperature processability and the suitable mechanical properties of the polymer matrix [1]. The dielectric properties of these composites can be in principle tunable by changing amount, dimension and type of filler. In this work, 0-3 connectivity nanocomposites based on poly(vinylidene fluoride) (PVDF) and containing 30 vol% of ceramic inclusions were prepared by solution casting followed by compression moulding. In particular, BaTiO3 nanoparticles were employed as such or coated with shells of SiO2 or TiO2 at different thickness in order to study the influence of surface coating on the final properties of the composites.

Research activities on macromolecules and polymeric materials at ISMAC Genova

High-permittivity (high-k) polymer-ceramic composites with engineered nano-architecture meet the increasingly marked tendency towards a more rational and sustainable use of energy. They provide a smart solution to combine the good dielectric properties of the ceramic filler with the processability, flexibility and high breakdown strength of the polymer matrix [1]. In this work, 0-3 connectivity nanocomposites based on poly(vinylidene fluoride) (PVDF) and containing 30 vol% of ceramic inclusions were prepared by solution casting followed by compression moulding. BaTiO3 nanoparticles, both as synthesised and coated with a thin shell of a binary oxide (SiO2 or TiO2), were employed to understand the role of interfaces, shape and morphology of inclusions. A better insight of the correlation between composite microstructure and dielectric properties was gained by combining FEM simulation and experimental data.

In the present work, an alternative method to induce the formation of PVDF ? phase was proposed, exploiting a well-known technique widely used for the polymer processing: the compression molding. In particular, it was used a double step process (P2), which consists in preparing a plate of material (i.e. neat PVDF or composite) and then repressing it at high pressure and at a temperature lower than the PVDF melting temperature. As concerns the neat PVDF, the molding conditions were modified to investigate their influence on the final amount of electroactive phase(s) obtained. The impact of processing on dielectric and dynamic-mechanical properties of the PVDF films was also studied on a selected series of samples. PVDF-based composites containing different amount of ceramic particles (such as BaTiO3 and PZT), widely used in the field of energy harvesting, were then prepared by solvent casting or melt blending. Besides a single-step (P1) molding carried out on samples with completely molten PVDF, also the P2 process was applied to the composites in order to investigate its effect on their final properties. The ensuing samples were characterized from morphological, spectroscopic, dynamic-mechanical and dielectric point of views.

The development of high-performance polymer nanocomposites (NCs) requires a strong interfacial interaction between filler and polymer matrix and an optimal filler nanodispersion. Among layered silicates, sepiolite has attracted researcher attention because of its easy availability, low cost, strong mechanical and chemical stability, and anisotropic particle shape. Even if several applications of sepiolite-polymer materials have been proposed in literature, the use of pristine sepiolite as filler in elastomers is very limited due to its hydrophilic surface and to the consequent low affinity towards polymers. To face with these issues, we explored a new approach to prepare rubber NCs based on the use of nano-sized sepiolite (NS-Sep) fibers. Pristine and organically-modified sepiolites were structurally modified by an acid treatment, which provides NS-Sep fibers with reduced particle size and increased silanol groups on the layer surface, preserving the anisotropic features. NS-Sep fibers were used to prepare by ex-situ blending styrene-butadiene rubber (SBR) NCs. Morphological, spectroscopic, thermal and mechanical analyses were performed for a complete characterization of the hybrid materials.

The demand for high dielectric constant materials and high energy density capacitors has rapidly increased in recent years due to the continuous and rapid development of the electronic industry and the need to store electrostatic energy more efficiently. The introduction of ferroelectric inclusions in a polymeric matrix enables the effective dielectric constant of the composite to be significantly increased while preserving the high breakdown field typical of polymers, thus improving the stored energy density. The effective dielectric constant of the composite can be tailored by varying size, shape and volume fraction of the inclusions as well as the dielectric constant of the polymeric matrix. In other words, the dielectric properties of the composite can be controlled by altering the electric field distribution inside the material. A further approach for modifying the distribution of the electric field is by coating the particles used as inclusions with an oxide layer with a different dielectric constant. In this work we have fabricated polyvinyldene fluoride (PVDF) composites containing 30 vol.% BaTiO3@AO2 (A = Si, Ti) particles and determined their dielectric properties. Barium titanate particles with a diameter of ?100 nm were synthesized using a hydrothermal-like method and coated with a thin shell (10 nm) of SiO2 or TiO2 by means of colloidal chemistry methods. The composites were prepared by solution casting using dimethylacetamide as solvent and subsequent compression molding. Reference composites were prepared by the same process using uncoated BaTiO3 particles. The dielectric properties of the composites (dielectric constant and loss tangent) were measured at different frequencies (1 - 10e6 Hz) in the temperature range 25-150 °C. The coating results in a significant modification on the effective permittivity which is mainly determined by the value of its dielectric constant. To gain insight into the role of the coating layer, the electric field distribution and the effective dielectric constant were calculated for the different composites using a 3D finite element modelling and compared to experimental results. This study provides some guidelines for tuning the dielectric properties of ferroelectric PVDF-ceramic composites.

The inclusion of ferroelectric ceramic particles into a polymer matrix increases the electric energy storing capability of the material, combining the high dielectric constant of the inclusions with the high breakdown field of polymers. The coating of the inclusions with a shell of binary oxide with a different dielectric constant, modifies the electric field distribution and tailors the final dielectric properties. PVDF-based composites containing BaTiO3 particles coated, by three different procedures, with a thin layer of TiO2 were prepared by solvent casting. The morphological and spectroscopic features of the BaTiO3@ TiO2 core-shell particles, their dispersion and the polymorphism of PVDF, were correlated to the dielectric properties. Gathered results show the influence of the morphological features of the core-shell particles on the final dielectric properties.

Rapporto finale sull'attività svolta per il progetto Polycom, nel periodo 18/03/2016 - 30/11/2018. L'attività si è svolta seguendo la programmazione dettagliata nel progetto allegato alla domanda di finanziamento. L'attività è stata concentrata sulla fabbricazione e caratterizzazione dei compositi PVDF-BaTiO3. L'attività effettuata nel periodo è sintetizzabile come segue: WP1) Sintesi di polveri di BaTiO3 con diversi diametri e rivestimento di tali particelle con ossidi binari nelle quantità richieste per la fabbricazione dei compositi nel WP3. WP2) Funzionalizzazione di particelle di BaTiO3 non rivestite e rivestite con derivati silanici. WP3) Fabbricazione di compositi PVDF-BaTiO3 tramite miscelazione nel fuso (melt blending) o filmatura da solvente (solvent casting). I film sono stati poi realizzati tramite stampaggio per pressofusione (pressure moulding). I film sono stati caratterizzati dal punto di vista della microstruttura, della tipologia di gruppi funzionali presenti, delle proprietà termiche. WP4) Misura delle proprietà dielettriche in funzione della frequenza e della temperatura effettuata su semplici capacitori preparati utilizzando i film prodotti nel WP3. Su alcuni compositi selezionati sono state effettuate misure in funzione del campo elettrico applicato. WP5) Simulazione FEM 3D delle proprietà dielettriche di compositi contenenti tre diversi tipi di particelle, non rivestite e rivestite con due ossidi binari, in funzione della frazione in volume delle inclusioni e dello spessore del rivestimento. WP6) Le attività principali hanno riguardato la messa a punto definitiva e l'aggiornamento del sito web, l'organizzazione di due meeting di progetto, la presentazione dei risultati per mezzo di comunicazioni a conferenze, la stesura di pubblicazioni scientifiche. In tutti i casi è stata data la dovuta visibilità alla Compagnia di San Paolo come ente finanziatore. Prot. CNR-ICMATE n. 3080 del 19/12/2018

PVDF-based composites containing 30 vol% ferroelectric ceramic inclusions were prepared by solution casting followed by two different compression molding procedures. BaTiO3 (BT) or core-shell BT@AO2 (A= Ti or Si) nanoparticles were considered. For BT and BT@TiO2 nanoparticles the effect of silanization was also investigated. All nanoparticles were thoroughly characterized by FTIR and TEM. The amount of PVDF electro-active crystalline phases in the composites was determined by ATR-FTIR spectroscopy, particle distribution/dispersion into the polymer matrix was analyzed by SEM-EDX microscopy, and the dielectric constant as well as the loss tangent were measured at different frequencies by impedance spectroscopy.

A new approach to prepare PNCs based on nano-sized sepiolite (NS-Sep) fibres was explored. Pristine Sep was structurally modified by an acid treatment, which provides NS-Sep fibers with reduced particle size and increased silanol groups on the surface layer. NS-Sep fibers were used to prepare styrene-butadiene rubber (SBR) NCs with enhanced mechanical properties. Dynamic-mechanical analysis of Sep NCs demonstrated that the modified Sep fibers provided an excellent balance between reinforcing and hysteretic behavior compared with large-sized pristine Sep and isotropic silica.

The demand for high dielectric constant materials and high energy density capacitors has rapidly increased in recent years due to the continuous and rapid development of the electronic industry and the need to store electrostatic energy more efficiently. The high breakdown field typical of polymers can be preserved while increasing the effective permittivity, if ferroelectric inclusions are embedded in the polymer matrix by forming a 0-3 connectivity composite, thus improving the stored energy density. The dielectric properties of the composite can be tailored by varying size, shape and volume fraction of the inclusions as well as the dielectric constant of the polymeric matrix, thus altering the electric field distribution inside the material. Moreover, the distribution of the electric field can be modified by coating the particles used as inclusions with an oxide layer with a different dielectric constant. In this work we have fabricated poly(vinylidene fluoride) (PVDF) composites containing 30 vol.% BaTiO3@AO2 (A = Si, Ti) particles and measured their dielectric properties. Barium titanate particles with a diameter of ?100 nm were synthesized using a hydrothermal-like method and coated with a thin shell (?10 nm) of SiO2 or TiO2 by means of colloidal chemistry methods. The composites were prepared by solvent casting followed by compression moulding. The dielectric properties of the composites (permittivity and loss tangent) were measured at different frequencies and several temperatures. The coating results in a significant modification of the effective permittivity, which is mainly determined by the value of its dielectric constant. To gain insight into the role of the coating layer, the electric field distribution and effective dielectric constant were calculated for the different composites using a 3D finite element modelling and compared to experimental results. Acknowledgement Work carried out in the framework of Project Polycom (IDROL:10359) funded by Fondazione Bancaria Compagnia di San Paolo.

Polymer-based composites are very attractive for advanced applications in the field of energy harvesting, storage and conversion. For instance, the introduction of high-permittivity ceramic particles into a polymer matrix, characterized by high breakdown field, leads to dielectric materials able to store large amounts of energy while maintaining desirable properties of the polymer, such as processability and flexibility. In particular, poly(vinylidene fluoride) (PVDF) is widely used as matrix due to its higher dielectric permittivity (?10), compared to other polymers, and its capability to crystallize in five different polymorphs, some of which possess a neat moment dipole. In this work 0-3 connectivity PVDF-based composites containing 30 vol% ferroelectric BaTiO3 (BT) ceramic inclusions were prepared by solution casting followed by compression molding, properly adjusting the processing conditions in order to induce the formation of the electro-active ? polymorph of PVDF. Three different compression molding methods were employed for realizing PVDF-BaTiO3 composites: the most promising procedure was then used for the preparation of composites containing modified, i.e. core-shell and/or functionalized, BT nanoparticles. All nanoparticles were characterized by FTIR and TEM. A thorough characterization was performed on the composites to investigate the influence of processing conditions and of filler type on the resulting dielectric properties, taking into account PVDF polymorphism and particles dispersion within the polymer matrix.

In this work was investigated the influence of processing conditions on PVDF polymorphism in PVDF/BaTiO3 composite dielectrics for energy storage applications

In this work polymer-based composites containing 10-35 vol.% BaTiO3 nanoparticles were prepared by melt blending followed by compression moulding to obtain sheets 0.5-1 mm thick. A commercial poly(vinylidene fluoride) (PVDF, SOLEF 1008 Solvay) grade was chosen as polymer matrix and BaTiO3 particles (diameter ca. 100 nm) synthesized by a hydrothermal-like method [3] were used as inorganic inclusions. The BaTiO3 particles were used bare or surface-modified with proper coupling molecules (silane derivatives) [4] and/or coated with a thin TiO2 shell (thickness 5-20 nm). Such engineered polymer/ceramic interfaces should facilitate the fine dispersion of the inclusions leading to a more homogeneous distribution of the electric field. Microstructural features and thermal behaviour of the ensuing composites were characterized by SEM, TG and DSC analyses. The amount of the ferroelectric crystalline ? phase in the PVDF matrix was determined by FT-IR spectroscopy and X-ray diffraction. The dielectric constant and the loss tangent of the composite materials were measured at different frequencies by impedance spectroscopy. Simulation of the field distribution in model composites was performed by 3D finite element modelling and correlated with the experimental evidences.

Report on surface functionalization of inorganic particles with silane coupling agents

BaTiO3 nanoparticles (100÷150 nm), prepared in-house by a hydrothermal-like method starting from BaCl2 and TiCl4 precursors, were dispersed into a matrix of poly(vinylidene fluoride) (PVDF, Solef 6008 Solvay). 0-3 connectivity composites containing up to 35 vol% of ceramic inclusions were obtained either by solution casting or melt blending in a Brabender type batch-mixer; a compression moulding step was performed to obtain sheets 0.5-1 mm thick enriched in the electro-active ? polymorph of PVDF. Bare and surface-modified BaTiO3 particles were used, modification included functionalization with silane-based coupling molecules and/or coating with a thin shell of TiO2 (k ? 100). Such engineered polymer/ceramic interfaces should facilitate a fine dispersion of the inclusions by realizing, from the particle core to its surface, a gradient of the dielectric constant giving a more homogeneous distribution of the electric field in the resulting composites. Morphological and microstructural features of particles and composites were investigated by TEM and SEM-EDX microscopy, respectively. The amount of the ferroelectric crystalline ? phase in the PVDF matrix was determined by ATR-FTIR spectroscopy and X-ray diffraction. The dielectric constant and the loss tangent of the composites were measured at different frequencies by impedance spectroscopy. Simulations of electric field distribution performed by 3D finite element modelling were correlated with the experimental evidences.

The demand for high dielectric constant materials and high energy density capacitors has rapidly increased in recent years due to the continuous and rapid development of the electronic industry and the need to store electrostatic energy more efficiently. The combination of dissimilar materials in a composite represents an effective approach for the optimization of the dielectric properties. The addition of ferroelectric (barium titanate, BaTiO3) nanoparticles with high dielectric constant (k 1000) enables the relative dielectric constant of the polymer (k 3-10) to be significantly increased without compromising some of the most useful properties of the material. Polymer composites were prepared using polyvinylidene fluoride (PVDF) as a matrix and BaTiO3 nanoparticles (d~100 nm) as inclusions. The composites were fabricated by mixing PVDF and BaTiO3 particles at 200°C using the melt-blend method. The microstructure was observed on fracture surfaces by SEM. The amount of ferroelectric beta phase in the PVDF matrix was determined by FT-IR spectroscopy and the dielectric propeties were determinated at different frequencies and temperature by impedance spectroscopy. Simulation of the field distribution in model composites was performed by 3D finite element modelling.

In the present work, raw hemp fibres were used to reinforce a commercial biopolyester, namely poly(1,4-butylene adipate-co-terephthalate), thus improving its mechanical properties. To this purpose, an appropriate surface treatment of the fibres was necessary to enhance the fibre/matrix adhesion. To reduce the intrinsic hydrophilicity of the hemp fibres, they were preliminary washed with diluted NaOHaq in mild conditions and then treated with a green process based on a novel soft plasma jet (developed by Nadir Srl). In the present case, this system allowed the use of a Ar + O2 gas mixture, coupled with deposition of methyl metacrylate. Thermogravimetric analysis (TGA) was carried out to evaluate thermal and thermo-oxidative stability of the ensuing composites and determine the fibre content. Morphological analysis of fibres and composites was performed by scanning electronic microscopy (SEM) coupled with EDX probe for element microanalysis. The eco-composites were investigated in terms of rheological, mechanical, and dynamic-mechanical behaviour in comparison with the neat biopolyester matrix. Specific mechanical testing were performed on fibres before and after surface modification treatments

Un materiale elastomerico ideale per applicazioni di tenuta deve possedere un profilo di proprietà tale da impedire perdite. L'utilizzo di nanocariche rinforzanti può permettere di modulare le proprietà meccaniche dei materiali elastomerici e di soddisfare requisiti sempre più stringenti. In questo lavoro è stato studiato l'effetto dell'aggiunta di piccole quantità di nanotubi di carbonio ad una mescola commerciale a base di gomma nitrilca per applicazioni di tenuta ad alte prestazioni. Accanto ad una caratterizzazione termo-meccanica e morfologica di base, è stata sviluppata una specifica procedura di prova per studiare la capacità di tenuta del materiale durante la fase di deformazione transiente. Tale fase può verificarsi in esercizio in applicazioni di tenuta statiche a causa di una perdita di accoppiamento o di una improvvisa variazione di carico. Sono stati studiati gli effetti del quantitativo di carica, del rilassamento del materiale e della velocità di spostamento della controparte sul comportamento del materiale a tenuta.

A biobased Janus molecule, 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3-propanediol (serinol pyrrole, SP), was used to prepare adducts with few layers graphene. Polyurethanes were prepared through the solvent free reaction of SP and 1,6-hexamethylene diisocyanate and polyethers were obtained from SP and 1,6-dibromo-hexane. Oligomers of both polymers gave stable interaction with carbon allotropes, such as few layers graphene and carbon nanotubes. This work demonstrates that is possible to introduce functional groups on graphene layers avoiding the oxidation reaction and, thus, harsh reaction conditions, dangerous and toxic reagents, solvents and catalysts. Moreover, SP allows the preparation of few layers graphene without adopting the two step oxidation-reduction process. The mechanism for the reaction of SP with graphene layers is discussed.

In this paper the effect of MWCNTs on a commercial CB filled nitrile-butadiene rubber (NBR), having 60 degree of Shore A hardness, used for high performance sealant applications, was studied. The CB filled NBR was added via melt blending using an open two roll mill with different weight percentages of MWCNTs: 1%, 2%, and 4%. The material behavior was analyzed by different laboratory tests: standard mechanical characterization tests (hardness, compression set, uniaxial compression, tensile and stress relax-ation test) and thermal analysis were carried out. The material characterization was focused on the behavior of the composite material at medium-high deformation levels (from 10% to 30% of strain in compression), typical for elastomeric materials in sealing application conditions. The state of dispersion of MWCNTs was correlated with mechanical response of the final materials.

There is an increasing demand of high permittivity (high-k) materials due to the rapid development of the electronic industry and the need of more efficient energy storage devices. The combination of dissimilar components in composites is expected to be an effective approach to better dielectric materials. The inclusion of high-k particles, such as Ag and BaTiO3, in a polymeric matrix can significantly increase the dielectric constant while preserving the flexibility and the high breakdown voltage typical of polymers. The combination of high-permittivity and large breakdown fields is a fundamental requirement to store electrostatic energy with high density. Ferroelectric BaTiO3 nanoparticles (50-100 nm) were obtained by a hydrothermal-like method starting from cheap inorganic precursors (BaCl2 and TiCl4). The size of the particles was tailored by changing the precursor concentration. Silver particles (20-200 nm) were synthesized by a solvothermal method using ethylene glycol as a solvent and AgNO3 as a precursor and adding polyvinylpyrrolidone (PVP) as growth modifier to control the particle size. The nature of the inclusion-polymer interface has a strong impact on the dispersion of the inorganic particles and the dielectric properties of the resultant composite. The compatibility between the two phases was improved by functionalizing the particles with specific coupling molecules, such as silane-based compounds. As a further strategy to improve the dielectric properties of the composite, the particles were coated with a thin TiO2 shell, which has a dielectric constant intermediate between the filler and the polymer matrix and thus realizes a more homogeneous distribution of the electric field.

The aim of this work is to study a spheroidal phyllosilicate, namely Halloysite NanoTubes (HNTs), as a possible reinforcing filler for tyre applications. HNT is a 1:1 alumino-silicate with a unique combination of tubular nanostructure. It has natural availability, rich functionality, good biocompatibility and high mechanical strength. However, HNTs are poorly compatible with the elastomers due to their hydrophilic character and the low concentration of functional groups on the external surface. In order to favor both the filler-polymer interaction and the particle dispersion in the rubber matrix, we investigated an effective method to increase the hydroxyl group density on the HNT surface, through controlled basic treatment. Moreover HNTs were functionalized with silane coupling agents to improve the compatibility with rubber. Modified nanotubes were used by ex-situ blending to prepare Styrene Butadiene Rubber nanocomposites. Morphological, spectroscopic and thermal analyses were performed for a complete characterization of the modified HNTs and their nanocomposites. The dynamic mechanical properties were evaluated and compared to those obtained by using pristine HNTs. The preliminary results revealed that HNT can act as a promising filler

This work reports new experimental results focused on polylactide/clay nanocomposites using PBAT as coupling agent [1]. The samples have been accurately characterized by different experimental techniques: XRD, TEM, TGA, standard DSC and MT-DSC with the aim to highlight the effect of lamellae dispersion and distribution at nanoscale onto the thermal features of resulting nanocomposites. We show that the presence of different interaction levels at the interface PLA/OMMT, even tuned by the presence of PBAT, affects both the crystalline phase structure (by differently promoting crystallization of ? and ?' forms) and the distribution between the amorphous fractions (rigid and mobile). Furthermore, we show that the cooperativity degree obtained from MT-DSC is a powerful complementary tool to X-Ray diffraction and microscopy when investigating the morphology of nanocomposites since it probes the physical interactions between the matrix and the filler. When the dominant morphology of the nanocomposite is exfoliated, the interfacial interactions between the matrix and the filler increase the cooperativity. On the other hand, intercalated morphology renders less effective the formation of physical bonds due to the confinement of the macromolecules in the galleries of fillers, decreasing hence the cooperativity degree.