In Situ Synthesis of Rubber Nanocomposites

Abstract The preparation and characterization of rubber based nanocomposites prepared by in situ generation of inorganic oxides by means of the hydrolytic solgel process are reviewed in the present chapter. The sol-gel approach has been applied to several rubber matrices to prepare reinforced vulcanized and unvulcanized rubbers. Several synthetic procedures are presented while the most investigated filler is silica obtained by hydrolysis and condensation of tetraethoxysilane. The effects of the different preparation conditions and of the filler content are generally discussed in terms of morphology (investigated by electron microscopy and small angle X-ray scattering) and mechanical properties (modulus, strength and extensibility). The mechanical properties of the in situ filled nanocomposites are generally better than those of the corresponding materials prepared with the conventional mechanical mixing of preformed particulates and elastomers. This enhancement is generally attributed to a lower tendency to filler-filler aggregation due to a lower particle surface interaction resulting from the 'bottomup approach' of the sol-gel process applied to the preparation of organic-inorganic hybrid materials

Thermo-Mechanical and Morphological Properties of Polymer Composites Reinforced by Natural Fibers Derived from Wet Blue Leather Wastes: A Comparative Study

The present work investigated the possibility to use wet blue (WB) leather wastes as natural reinforcing fibers within different polymer matrices. After their preparation and characterization, WB fibers were melt-mixed at 10 wt.% with poly(lactic acid) (PLA), polyamide 12 (PA12), thermoplastic elastomer (TPE), and thermoplastic polyurethane (TPU), and the obtained samples were subjected to rheological, thermal, thermo-mechanical, and viscoelastic analyses. In parallel, morphological properties such as fiber distribution and dispersion, fiber–matrix adhesion, and fiber exfoliation phenomena were analyzed through a scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) to evaluate the relationship between the compounding process, mechanical responses, and morphological parameters. The PLA-based composite exhibited the best results since the Young modulus (+18%), tensile strength (+1.5%), impact (+10%), and creep (+5%) resistance were simultaneously enhanced by the addition of WB fibers, which were well dispersed and distributed in and significantly branched and interlocked with the polymer matrix. PA12- and TPU-based formulations showed a positive behavior (around +47% of the Young modulus and +40% of creep resistance) even if the not-optimal fiber–matrix adhesion and/or the poor de-fibration of WB slightly lowered the tensile strength and elongation at break. Finally, the TPE-based sample exhibited the worst performance because of the poor affinity between hydrophilic WB fibers and the hydrophobic polymer matrix

Mechanical performance of epoxy coated AR-glass fabric Textile Reinforced Mortar: Influence of coating thickness and formulation

The mechanical performance of epoxy coated AR-glass fabric reinforced composite is investigated. A three-stage manufacturing process is considered, which involves fabric surface functionalization, liquid coating deposition and long-term setting and finally fabric embedment in the mortar matrix. Two epoxy coatings are considered, which only differ by the hardening agent. However, coating thickness is significantly diverse as a result of modified viscosity during liquid deposition. Performance is assessed in uni-axial tension as well as in three-point bending and it is expressed in terms of strength curves, data dispersion, crack pattern and failure mechanism. Remarkably, despite being very similar, the analyzed coatings produce a significantly different performance, especially when data dispersion is incorporated and design limits are considered. Indeed, although both coatings are able to consistently deliver fabric rupture at failure, only the thinnest is associated with small data scattering and an almost plastic post-peak behavior in bending. The associated design elongation limit reaches the maximum allowed value according to the ICC guidelines. In fact, it appears that coating thickness plays a crucial role in determining mechanical performance and fabric flexibility. The proposed manufacturing process proves extremely effective at enhancing matrix-to-fabric adhesion and thereby prevent telescopic failure

Printing and characterization of 3D high-loaded nanocomposites structures

Additive Manufacturing (AM) technologies are spreading rapidly both in academic research and industrial environments [1]. Nanomaterials have proven to provide new size-dependent properties compared to traditional bulk materials [2]. The integration of nanotechnology into AM opens new and interesting challenges in manufacturing advanced nanocomposite materials with custom-made properties and geometries [3]. Synergy between nanomaterials, such as metal and oxide nanoparticles, and AM can in fact result in improved functional and structural performance of manufactured devices, filling the gap between design and production of a specific tool. For instance, silica nanoparticles (SiO2 NPs) are increasingly used as nanofillers, thanks to their excellent mechanical properties, to fabricate nanocomposites used in a wide range of applications [4]. Stereolithography (SLA) represents one of the most widespread AM technologies used to fabricate 3D engineered structures. The general procedure for building objects with SLA involves photo-polymerization of liquid monomer into solid resin by means of an ultraviolet (UV) laser, which creates targeted cross-linked regions where the light irradiates the matrix [5]. SLA AM of nanocomposites usually involves mixing of ex situ synthesized nanoparticles with commercially available acrylic monomers, followed by an optimized printing process. Stable dispersion of colloidal SiO2 NPs in acrylate monomers or oligomers are commercially available, such as Nanocryl product family commercialized by Evonik. These products are traditionally used in adhesive and electronic applications, such as highly scratchresistant coatings for fiber optic cables, conformal coatings, UV curing adhesives for printed circuit boards and can be successfully employed in AM of high-loaded nanocomposites. The produced 3Dprinted specimens were employed to characterize the nanocomposites microstructure and thermomechanical properties respectively by means of scanning electron microscopy (SEM) and dynamicmechanical analyses (DMA)

Special Resins for Stereolithography: In Situ Generation of Silver Nanoparticles

The limited availability of materials with special properties represents one of the main limitations to a wider application of polymer-based additive manufacturing technologies. Filled resins are usually not suitable for vat photo-polymerization techniques such as stereolithography (SLA) or digital light processing (DLP) due to a strong increment of viscosity derived from the presence of rigid particles within the reactive suspension. In the present paper, the possibility to in situ generate silver nanoparticles (AgNPs) starting from a homogeneous liquid system containing a well dispersed silver salt, which is subsequently reduced to metallic silver during stereolithographic process, is reported. The simultaneous photo-induced cross-linking of the acrylic resin produces a filled thermoset resin with thermal-mechanical properties significantly enhanced with respect to the unfilled resin, even at very low AgNPs concentrations. With this approach, the use of silver salts having carbon-carbon double bonds, such as silver acrylate and silver methacrylate, allows the formation of a nanocomposite structure in which the release of by-products is minimized due to the active role of all the reactive components in the three dimensional (3D)-printing processes. The synergy, between this nano-technology and the geometrical freedom offered by SLA, could open up a wide spectrum of potential applications for such a material, for example in the field of food packaging and medical and healthcare sectors, considering the well-known antimicrobial effects of silver nanoparticles

Introduction

This issue of Itinera aims to address the connections between architecture and the performing arts in its various aspects and from multiple points of view. The growing emphasis on the performative character of artistic practices, namely, their ability to involve spectators directly and pervasively (Dixon 2007), imbues the relationship between architecture, the performing arts, and the spectator’s experience. The sharing of the scenic space by spectators and performers is essential for the co-production of a common energy which operates as a “transforming force” and thereby opens up the shared experience of discovering oneself and the other as a union of the body and the mind (Fischer-Lichte 2004).This issue of Itinera aims to address the connections between architecture and the performing arts in its various aspects and from multiple points of view. The growing emphasis on the performative character of artistic practices, namely, their ability to involve spectators directly and pervasively (Dixon 2007), imbues the relationship between architecture, the performing arts, and the spectator’s experience. The sharing of the scenic space by spectators and performers is essential for the co-production of a common energy which operates as a “transforming force” and thereby opens up the shared experience of discovering oneself and the other as a union of the body and the mind (Fischer-Lichte 2004)

Shape memory nanocomposite of poly(L-lactic acid)/graphene nanoplatelets triggered by infrared light and thermal heating

In this study, the effect of graphene nanoplatelets (GNPs) on the shape memory properties of poly(L-lactic acid) (PLLA) was studied. In addition to thermal activation, the possibility of infrared actuating of thermo-responsive shape memory PLLA/GNPs nanocomposite was investigated. The incorporated GNPs were expected to absorb infrared wave’s energy and activate shape memory PLLA/GNPs. Different techniques such as differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), field emission gun scanning electron microscope (FEG-SEM) and dynamic mechanical thermal analysis (DMTA) were used to characterize samples. DSC and WAXD results indicated that GNPs augmented crystallinity due to nucleating effect of graphene particles. GNPs improved both thermal and infrared activating shape memory properties along with faster response. Pure shape memory PLLA was slightly responsive to infrared light and its infrared actuated shape recovery ratio was 86% which increased to more than 95% with loading of GNPs. Drastic improvement in the crystallinity was obtained in nanocomposites with lower GNPs contents (0.5 and 1 wt%) due to finer dispersion of graphene which resulted in more prominent mechanical and shape memory properties enhancement. Infrared activated shape memory PLLA/GNPs nanocomposites can be developed for wireless remote shape control of smart medical and bio-systems

Enhancing the scratch resistance of polycarbonate with poly(ethylene oxide)-silica hybrid coatings

Scratch-resistant coatings for bisphenol-A polycarbonate sheets were obtained by the sol–gel synthesis of an organic–inorganic hybrid system based on poly(ethylene oxide) and silica. The organic–inorganic hybrids were thermally cured into hard transparent coatings by using conventional and microwave (MW) ovens. Both techniques proved to be equally efficient in promoting the system’s crosslinking, as evaluated by 29Si MAS-NMR. The MW-assisted curing, however, was much faster. Photoelasticity analysis showed that MW-assisted curing causes localized overheating of the samples, inducing a state of residual plane stresses that bring about dimensional instability of the coated material. Instrumented scratch tests for the coated samples revealed an increase of 1 order of magnitude in the minimal load at which a scratch track appears on the sample surface. However, the friction coefficient values for samples with thermally cured coatings were lower than those produced by MW-assisted curing

Novel PBAT‐Based Biocomposites Reinforced with Bioresorbable Phosphate Glass Microparticles

Biocomposites based on poly(butylene adipate terephthalate) (PBAT) and reinforced with micro-particles of inorganic biodegradable phosphate glass (PG) at 2, 10, and 40 wt% are prepared and characterized from a mechanical and morphological point of view. Scanning electron microscope (SEM) images show a good dispersion of the PG micro-grains, even at high concentrations, in the PBAT matrix, resulting in homogeneous composites. Tensile and dynamic-mechanical tests, respectively, indicate that Young’s and storage moduli increase with PG concentration. The reinforcement of PBAT aims at modifying and tailoring the mechanical and viscoelastic properties of the material to expand its application field especially in the food and agricultural packaging sector, thanks to the similarity of PBAT performance with polyethylene

Hydrophobic and Oleophobic Coatings Based on Perfluoropolyether/Silica Hybrids by the Sol-Gel Method

Glass substrates were spin-coated with a perfluoropolyether oligomer based organic-inorganic hybrid material, and prepared by the sol-gel process. Contact angle analysis and atomic force microscopic analysis were carried out to characterize the surface of the prepared coatings. All systems exhibited strong hydrophobic and oleopophobic characteristics. The wettability behavior was found to be almost independent of both molecular weight and functionality of the fluorinated oligomer. The low values obtained for the contact angle and surface tension indicate that surface segregation of perfluoropolyether segments is likely to take place within the network. On the basis of these results and the high quality of the obtained coatings, these materials could be used as functional coatings to impart water and oleo-repellent characteristics to glasses and other similar substrates