A Green Treatment Mitigates the Limitations of Coffee Silver Skin as a Filler for PLA/PBSA Compatibilized Biocomposites.

The development of fully renewable and biodegradable composites for short-term applications was pursued by combining a compatibilized poly(lactic acid) (PLA)/poly(butylene succinate-co-adipate) (PBSA) (60:40 wt:wt) blend with coffee silver skin (CSS), an industrial byproduct from coffee processing. An epoxy-based reactive agent (Joncryl ADR-4468) was added as a compatibilizer. CSS was incorporated at 5, 10, and 20 wt% in the blend both in the as-received state and after a simple thermal treatment in boiling water, which was performed to mitigate the negative impact of this filler on the rheological and mechanical properties of the blend.

Toughening Effect of 2,5-Furandicaboxylate Polyesters on Polylactide-Based Renewable Fibers.

This work presents the successful preparation and characterization of polylactide/poly(propylene 2,5-furandicarboxylate) (PLA/PPF) and polylactide/poly(butylene 2,5-furandicarboxylate) (PLA/PBF) blends in form of bulk and fiber samples and investigates the influence of poly(alkylene furanoate) (PAF) concentration (0 to 20 wt%) and compatibilization on the physical, thermal, and mechanical properties. Both blend types, although immiscible, are successfully compatibilized by Joncryl (J), which improves the interfacial adhesion and reduces the size of PPF and PBF domains. Mechanical tests on bulk samples show that only PBF is able to effectively toughen PLA, as PLA/PBF blends with 5-10 wt% PBF showed a distinct yield point, remarkable necking propagation, and increased strain at break (up to 55%), while PPF did not show significant plasticizing effects.

Development of Novel Polypropylene Syntactic Foams Containing Paraffin Microcapsules for Thermal Energy Storage Applications.

polypropylene (PP) syntactic foams (SFs) containing hollow glass microspheres (HGMs) possess low density and elevated mechanical properties, which can be tuned according to the specific application. A possible way to improve their multifunctionality could be the incorporation of organic Phase Change Materials (PCMs), widely used for thermal energy storage (TES) applications. In the present work, a PCM constituted by encapsulated paraffin, having a melting temperature of 57 °C, was embedded in a compatibilized polypropylene SF by melt compounding and hot pressing at different relative amounts.

Three Dimensional Printing of Multiscale Carbon Fiber-Reinforced Polymer Composites Containing Graphene or Carbon Nanotubes.

Three-dimensional printing offers a promising, challenging opportunity to manufacture component parts with ad hoc designed composite materials. In this study, the novelty of the research is the production of multiscale composites by means of a solvent-free process based on melt compounding of acrylonitrile-butadiene-styrene (ABS), with various amounts of microfillers, i.e.

Evaluating the Multifunctional Performance of Structural Composites for Thermal Energy Storage.

The simultaneous need for high specific mechanical properties and thermal energy storage (TES) function, present in several applications (e.g., electric vehicles), can be effectively addressed by multifunctional polymer-matrix composites containing a reinforcing agent and a phase change material (PCM).

Mechanical Behaviour of Multifunctional Epoxy/Hollow Glass Microspheres/Paraffin Microcapsules Syntactic Foams for Thermal Management.

Epoxy/hollow glass microsphere (HGM) syntactic foams (SFs) are peculiar materials developed to combine low density, low thermal conductivity, and elevated mechanical properties. In this work, multifunctional SFs endowed with both structural and thermal management properties were produced for the first time, by combining an epoxy matrix with HGM and a microencapsulated phase change material (PCM) having a melting temperature of 43 °C. Systems with a total filler content (HGM + PCM) up to 40 vol% were prepared and characterized from the mechanical point of view with a broad experimental campaign comprising quasi-static, impact, and fracture toughness tests.

Thermophysical Properties of Multifunctional Syntactic Foams Containing Phase Change Microcapsules for Thermal Energy Storage.

Syntactic foams (SFs) combining an epoxy resin and hollow glass microspheres (HGM) feature a unique combination of low density, high mechanical properties, and low thermal conductivity which can be tuned according to specific applications. In this work, the versatility of epoxy/HGM SFs was further expanded by adding a microencapsulated phase change material (PCM) providing thermal energy storage (TES) ability at a phase change temperature of 43 °C. At this aim, fifteen epoxy (HGM/PCM) compositions with a total filler content (HGM + PCM) of up to 40 vol% were prepared and characterized.

Electrostatic bellow muscle actuators and energy harvesters that stack up.

Future robotic systems will be pervasive technologies operating autonomously in unknown spaces that are shared with humans. Such complex interactions make it compulsory for them to be lightweight, soft, and efficient in a way to guarantee safety, robustness, and long-term operation. Such a set of qualities can be achieved using soft multipurpose systems that combine, integrate, and commute between conventional electromechanical and fluidic drives, as well as harvest energy during inactive actuation phases for increased energy efficiency.

Graphene/Carbon Nanotube Hybrid Nanocomposites: Effect of Compression Molding and Fused Filament Fabrication on Properties.

The present work reports on the production and characterization of acrylonitrile butadiene styrene (ABS) hybrid nanocomposite filaments incorporating graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) suitable for fused filament fabrication (FFF). At first, nanocomposites with a total nanofiller content of GNP and/or CNT of 6 wt.% and a GNP/CNT relative percentage ratio of 0, 10, 30, 50, 70, and 100 were produced by melt compounding and compression molding.

Effects of the Nanofillers on Physical Properties of Acrylonitrile-Butadiene-Styrene Nanocomposites: Comparison of Graphene Nanoplatelets and Multiwall Carbon Nanotubes.

The effects of carbonaceous nanoparticles, such as graphene (GNP) and multiwall carbon nanotube (CNT) on the mechanical and electrical properties of acrylonitrile⁻butadiene⁻styrene (ABS) nanocomposites have been investigated. Samples with various filler loadings were produced by solvent free process. Composites ABS/GNP showed higher stiffness, better creep stability and processability, but slightly lower tensile strength and electrical properties (low conductivity) when compared with ABS/CNT nanocomposites.

Filaments Production and Fused Deposition Modelling of ABS/Carbon Nanotubes Composites.

Composite acrylonitrile-butadiene-styrene (ABS)/carbon nanotubes (CNT) filaments at 1, 2, 4, 6 and 8 wt %, suitable for fused deposition modelling (FDM) were obtained by using a completely solvent-free process based on direct melt compounding and extrusion. The optimal CNT content in the filaments for FDM was found to be 6 wt %; for this composite, a detailed investigation of the thermal, mechanical and electrical properties was performed. Presence of CNT in ABS filaments and 3D-printed parts resulted in a significant enhancement of the tensile modulus and strength, accompanied by a reduction of the elongation at break.

Wax Confinement with Carbon Nanotubes for Phase Changing Epoxy Blends.

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.

Effects of Fumed Silica and Draw Ratio on Nanocomposite Polypropylene Fibers.

Hydrophylic fumed silica AR974 was tested as a potential nanofiller for the production of composite isotactic polypropylene filaments/fibers (containing 0.25⁻2 vol % of nanoparticles) via melt compounding and subsequent hot drawing. The objectives of this study were as follows: (i) to investigate the effects of the composition and the processing conditions on the microstructure and the thermal and mechanical properties of the produced fibers; (ii) to separate the effects of silica addition from those produced by fiber drawing; and (iii) to interpret the changes in the matrix molecular mobility (produced by silica and/or drawing).

Modeling of the devolatilization kinetics during pyrolysis of grape residues.

Thermo-gravimetric analysis (TGA) was performed on grape seeds, skins, stalks, marc, vine-branches, grape seed oil and grape seeds depleted of their oil. The TGA data was modeled through Gaussian, logistic and Miura-Maki distributed activation energy models (DAEMs) and a simpler two-parameter model. All DAEMs allowed an accurate prediction of the TGA data; however, the Miura-Maki model could not account for the complete range of conversion for some substrates, while the Gaussian and logistic DAEMs suffered from the interrelation between the pre-exponential factor k0 and the mean activation energy E0--an obstacle that can be overcome by fixing the value of k0 a priori.

Poly(D, L-lactide/epsilon-caprolactone)/hydroxyapatite composites as bone filler: an in vivo study in rats.

In this study, a novel composite bone substitute was implanted in animal models (rats) and their in vivo characteristics were examined. A D,L-lactide and E-caprolactone copolymer (Mw: 80,000; Mn:40,000, and PI:2.00) was synthesized by ring-opening polymerization of the respective dimers using stannous octoate as the catalyst.

Finite element analysis of a glass fibre reinforced composite endodontic post.

In this work the mechanical response to external applied loads of a new glass fibre reinforced endodontic post is simulated by finite element (FE) analysis of a bidimensional model. The new post has a cylindrical shape with a smooth conical end in order to adequately fit the root cavity, and to avoid edges that could act as undesired stress concentrators. Mechanical data obtained by three-point bending tests on some prototypes fabricated in the laboratory are presented and used in the FE model.

Poly(epsilon-caprolactone-co-D,L-lactide) /silk fibroin composite materials: preparation and characterization.

Poly(epsilon-caprolactone-co-D,L-lactide) copolymers with 10, 30, and 50% by weight of silk particles (size range: 5-250 microm) derived from Bombyx mori were blended in acetone solution. After evaporation of the solvent, the morphology, thermal behavior, and mechanical properties of the composites were examined. The composites were transparent and the silk fibroin particles were homogeneously distributed within the composite structure.

Poly(D,L-lactide/epsilon-caprolactone)/hydroxyapatite composites.

In this study, elastomeric D,L-lactide and epsilon-caprolactone copolymers with two different molecular weights (Mn: 108.000 and 40.000) were synthesized by ring-opening polymerization of the respective dimers by using stannous octoate as the catalyst, as a potential bone-filling material.

Preparation and properties of poly(L-lactide)/hydroxyapatite composites.

In this study, two different viscosity-average molecular weight (eta = 4.0 and 7.8) poly(L-lactide) (PLLA) were synthesized by ring-opening polymerization and the poly(L-lactide)/hydroxyapatite composites (PLLA/HA) were prepared by blending HA particles (size range: 25-45 microm and Ca/P = 1.

Experimental evaluation of a resorbable intramedullary plug for cemented total hip replacement.

In order to evaluate degradation kinetics and biocompatibility of a resorbable poly(D,L-lactic acid) (PDLLA) plug for total cemented hip prostheses, an experimental in vitro and in vivo study was carried out. Degradation rate studies were performed in Ringer solution and after in vivo plug implantation in the femoral medullar cavity of rabbits. In vitro biocompatibility was evaluated in murine fibroblast cell cultures.

Polymerization kinetics, glass transition temperature and creep of acrylic bone cements.

Sulfix-6 and Zimmer LVC 60/30 bone cements were selected and the polymerization kinetics and resulting glass transition temperature Tg; creep behaviour in the dry or water-saturated state; and sorption and diffusion of water were studied. The calculation of conversion was based on a comparison of the residual polymerization heat measured by differential scanning calorimetry and the corresponding theoretical value. The conversion reached 99% after 90 min of quasi-adiabatic polymerization starting at 23 degrees C or after 10 min of isothermal polymerization at 37 degrees C.

A study on the in vitro degradation of poly(lactic acid).

The in vitro degradation of samples of L- and D,L-lactic acid polymers, P(L)LA and P(DL)LA respectively, having different molecular weights, morphology and/or geometry, has been studied through the determination of viscometric molecular weight, mass and mechanical properties as function of the immersion time in Ringer solution at 37 degrees C. In particular have been compared the degradation kinetics of P(L)LA, amorphous and crystalline, and of P(L)LA and P(DL)LA having different molecular weight and sample geometry. From the molecular weight versus the degradation time data, a degradation rate has been defined, as the derivative of the function best fitting the data, normalized to the molecular weight of the polymer at each time.

Reproducibility of late phase pulmonary response to exercise and its relationship to bronchial hyperreactivity in children with chronic asthma.

To determine the reproducibility of the delayed response to exercise and its effect on bronchial hyperreactivity, we had 26 asthmatic children perform treadmill exercise challenge on two occasions 1 week apart. Both challenges were preceded by 2 control days and 1 histamine challenge day, and were followed by another histamine challenge day. Peak expiratory flow rate (PEFR) was measured hourly for 12 hours on each control day and for 12 hours after each exercise or histamine challenge.