Morphology and properties evolution upon ring-opening polymerization during extrusion of cyclic butylene terephthalate and graphene-related-materials into thermally conductive nanocomposites

In this work, the study of thermal conductivity before and after in-situ ring-opening polymerization of cyclic butylene terephthalate into poly (butylene terephthalate) in presence of graphene-related materials (GRM) is addressed, to gain insight in the modification of nanocomposites morphology upon polymerization. Five types of GRM were used: one type of graphite nanoplatelets, two different grades of reduced graphene oxide (rGO) and the same rGO grades after thermal annealing for 1 hour at 1700{\deg}C under vacuum to reduce their defectiveness. Polymerization of CBT into pCBT, morphology and nanoparticle organization were investigated by means of differential scanning calorimetry, electron microscopy and rheology. Electrical and thermal properties were investigated by means of volumetric resistivity and bulk thermal conductivity measurement. In particular, the reduction of nanoflake aspect ratio during ring-opening polymerization was found to have a detrimental effect on both electrical and thermal conductivities in nanocomposites

Effect of morphology and defectiveness of graphene-related materials on the electrical and thermal conductivity of their polymer nanocomposites

In this work, electrically and thermally conductive poly (butylene terephthalate) nanocomposites were prepared by in-situ ring-opening polymerization of cyclic butylene terephthalate (CBT) in presence of a tin-based catalyst. One type of graphite nanoplatelets (GNP) and two different grades of reduced graphene oxide (rGO) were used. Furthermore, high temperature annealing treatment under vacuum at 1700{\deg}C was carried out on both RGO to reduce their defectiveness and study the correlation between the electrical/thermal properties of the nanocomposites and the nanoflakes structure/defectiveness. The morphology and quality of the nanomaterials were investigated by means of electron microscopy, x-ray photoelectron spectroscopy, thermogravimetry and Raman spectroscopy. Thermal, mechanical and electrical properties of the nanocomposites were investigated by means of rheology, dynamic mechanical thermal analysis, volumetric resistivity and thermal conductivity measurements. Physical properties of nanocomposites were correlated with the structure and defectiveness of nanoflakes, evidencing a strong dependence of properties on nanoflakes structure and defectiveness. In particular, a significant enhancement of both thermal and electrical conductivities was demonstrated upon the reduction of nanoflakes defectiveness

Textile Membranes Reused as a Tool for Noise Control

Textile membranes are an architectural solution used for their maximal lightness, efficiency and adaptability. Unfortunately, once they reach their end-of-life phase, it is difficult to recover them. To be disposed of, they undergo very expensive and often difficult recycling processes. Their reuse as an acoustic treatment and reverberation control system is a solution to creating a light, economical and effective acoustic system that also solves the difficult end-of-life scenario. The membranes take on the role of acoustic diffusers, elements that, through their geometric conformation, can control the behavior of sound. The structure of the system allows the acoustics of the interior spaces to be conditioned through some peculiar characteristics that are influenced, in part, by the material they are made of but above all by their shape. By cutting and joining the membranes, a modular and repeatable element is created, which, in combination with others, enables the creation of an acoustic control device capable of competing with traditional acoustic treatment systems without the use of newly produced materials. The optimized shape of the membranes is the variable responsible for the effective reduction in reverberation times: 2.2 s compared to the initial value of 7.5 without the textile membranes

Design-driven Uniaxial and Biaxial Tensile Testing of Knitted Fabrics Applied to Construction

Knitted fabrics are rarely subjected to tensile stress tests in the field of architectural construction materials, mostly due to their common use as drapery. However, recent non-standard applications of tensioned knitted textiles to hybrid lightweight constructions call for the assessment of their mechanical behavior. In the light of the absence of specific testing methodologies regarding knitted fabrics in the field of construction, this study aims at investigating customized testing techniques that target design requisites, as well as extending previous groundwork on plain weftknitted textiles to tuck-loop knit structures. Fabrics with a piquet Lacoste loop structure are tested uniaxially and biaxially in order to estimate the feasibility of a relatively large-scale project. The challenging task consists of stretching the limited production width in weft direction to the extended dimensions of the tensile architectural project. Hence the study focuses on elongation limits and especially on the maximum elongation that allows elastic deformation. Extracted empirical data are expressed in the form of stress/strain curves that enable an appropriate understanding of the textiles’ mechanical behavior. This inquiry points out the extent to which knit pattern favors directional elongation in warp as opposed to weft or vice-versa. In addition, it addresses the mechanical performance of knitted textiles by means of a strategic customization of tensile tests that can make them better at informing the design process and feasibility assessment

La riforma dei servizi ispettivi in materia di lavoro e previdenza sociale. Commentario al decreto legislativo 23 aprile 2004, n. 124

Il presente volume nasce dalla volontà di contribuire alla diffusione dei contenuti di una riforma – quella dei servizi ispettivi e delle attività di vigilanza prevista dal d.lgs. n. 124/2004 – di cui ancora troppo poco si parla e discute, e che pure potrebbe risultare decisiva per il progetto di modernizzazione del nostro mercato del lavoro delineato con la c.d. legge Biagi. L’effettività delle regole del diritto del lavoro è, in effetti, la condizione primaria per una più efficiente tutela dei diritti dei lavoratori e, al tempo stesso, è anche garanzia di leale competizione tra le imprese

Polyhedral oligomeric silsesquioxane (POSS) surface grafting: A novel method to enhance polylactide hydrolysis resistance

This work considers the development of an easy and scalable approach to change the features of poly(L-lactide) (PLLA) films, which is based on the application of a surface treatment with an amino-functionalized polyhedral oligomeric silsesquioxane (POSS). Indeed, the developed approach is based on the potential reactivity of POSS amino group towards the polymer functionalities to produce an aminolysis reaction, which should promote the direct grafting of the silsesquioxane molecules on the polymer surface. Neat and treated films were studied by infrared spectroscopy and X-ray photoelectron spectroscopy, which proved the effectiveness of POSS grafting. Moreover, scanning electron microscopy measurements demonstrated the homogeneous distribution of Si on the film surface treated with the silsesquioxane. The influence of the film treatment on the surface wettability was evidenced by contact angle measurements. These findings demonstrated a relevant enhancement of the surface hydrophobicity, which increase turned out to depend on the conditions applied, as it increased by increasing the reaction temperature and the contact time. Finally, in order to evaluate the stability of neat and of the treated PLLA films the surface morphology of the samples treated with pH 7.4 buffer at 50 \ub0C was studied

On the stability of solutions of semilinear elliptic equations with Robin boundary conditions on Riemannian manifolds

We investigate existence and nonexistence of stationary stable nonconstant solutions, i.e. patterns, of semilinear parabolic problems in bounded domains of Riemannian manifolds satisfying Robin boundary conditions. These problems arise in several models in applications, in particular in Mathematical Biology. We point out the role both of the nonlinearity and of geometric objects such as the Ricci curvature of the manifold, the second fundamental form of the boundary of the domain and its mean curvature. Special attention is devoted to surfaces of revolution and to spherically symmetric manifolds, where we prove refined results

Efeito da aplicação do ferro dextrano sobre o desempenho de leitões lactentes produzidos no Sistema Intensivo de Suínos Criados ao Ar Livre - SISCAL.

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