Nanoparticle Dynamics in Polymer Melts

The effect of small amounts of nanoparticles on the melt-state linear viscoelastic behaviour is investigated for different polymer-nanoparticles model systems characterized by poor polymer-particles interactions and low particle contents.contents. The drastic increase of the rheological properties with respect to the matrices is related to the formation of a filler network above a critical particles volume fraction. Once formed, the filler network exhibits an elastic feature that mixes with the intrinsic viscoelastic response of the polymer matrix, resulting in a complex Φ- and ω-dependent viscoelastic response of the nanocomposite. However, we show that the contributions of filler network and suspending medium can be decoupled due to the weak polymer-particle interactions and the differences in temporal relaxation scales. The adopted approach is validated through the building of a master curve of the moduli, which reflects the scaling of the elasticity of composites along the viscosity of the suspending medium. The two-phase model well works irrespective of the structure of the filler network, making evident the strict interrelationships between the structure, both on nano- and micro-scale, and the melt- state behaviour of the studied PNCs

Thermal Conductivity of Polypropylene-Based Materials

In this work, the authors aimed to provide an overview about the thermal conductivity of polypropylene, of its related compounds and the main methods of measurement. The growing spread of polypropylene in the industrial world together with the increasing demand of thermally conductive plastics represented the driving force of studying the heat transport in the polypropylene, and of recent progress and development of the thermal conduction in polypropylene-based materials. At regard, the common approach has been devoted to fill the polymer with thermally conductive materials: metallic, carbon based, ceramic and mineral fillers have been taken into account depending on the need to preserve electrical insulation, lightweight, production increasing or cost saving in the final compositions. Different parameters have been considered in order to optimize the ultimate thermal performances in the realized composites: (i) filler dispersion, (ii) filler/matrix and filler/filler interactions. The introduction of functional groups on the filler surface or in the polymer chain has been tested for acting on the dispersion and on the interfacial interaction. Then, hybrid materials, consisting in two particles different in size and shape combined with the attempt to realize a synergistic effect and to support a conductive network in the matrix, have been investigated

Solid particle erosion and viscoelastic properties of thermoplastic polyurethanes

The wear resistance of several thermoplastic polyurethanes (TPUs) having different chemical nature and micronscale arrangement of the hard and soft segments has been investigated by means of erosion and abrasion tests. The goal was correlating the erosion performances of the materials to their macroscopic mechanical properties. Unlike conventional tests, such as hardness and tensile measurements, viscoelastic analysis proved to be a valuable tool to study the erosion resistance of TPUs. In particular, a strict correlation was found between the erosion rate and the high-frequency (~10^7 Hz) loss modulus. The latter reflects the actual ability of TPU to dissipate the impact energy of the erodent particles

Controlling Process Variables in 3D Printing to Limit the Energy Consumption

This study looked at effective energy usage and renewable resources to make 3D printing more environmentally friendly. The use of bio-based materials and the investigation of technological aspects that maximized the mechanical properties of 3D-printed products and assured energy cost savings were the adopted strategies. Two bio-based thermoplastics made from pure and filled polylactide acid (PLA) with wood were examined. These filaments were printed by changing the extruder temperature (from 190 to 220°C, respectively) and the printing speed (from -30% to +30% of default value) to verify the actual process conditions that allow the material to be extruded for a given printer apparatus. A dynamic mechanical analysis was performed on developed specimens. The energy consumption, to heat and melt the thermoplastics, for every combination of processing variables, was calculated. Results allowed to attest that storage modulus of printed parts and the amount of energy spent during printing were more affected by printing speed than by extruder temperatures. Particularly in the case of PLA+WOOD, by doubling the printing speed, the productivity increased by 37% despite a 30% rise in energy usage. The mechanical properties and printing accuracy did not appear to be severely impacted by an increase in printing speed from 70 to 130 mm/s at least for simple geometries and small sample sizes

Fully Bio-Based Nanocomposite: Formulations For Packaging Application

The effect of a small amount of organoclay (OMMT) on mechanical, dynamic-mechanical, barrier and thermal properties of blown films based on blends of poly(lactic acid) (PLA) and polyamide 11 (PA11) was investigated. The addition of PA11 results in a decrease of elastic modulus (E) and tensile strength (σR) compared to neat PLA, which suggests poor interfacial adhesion between the polymer phases. Besides an enhancement of E and σR, the addition of 1 wt% of OMMT brings about a significant increase of the elongation at break. Neither blending with PA11 nor adding OMMT cause appreciable alterations of the barrier properties of the films, which remain essentially the same as those of pure PLA. Thermogravimetric analysis reveals that the onset of thermal degradation of the OMMT-filed blend is 15°C higher than of neat PLA. This improvement is probably due to the labyrinth effect of the PA11 phase. Finally, the OMMT brings about a slight enhancement of the glassy modulus compared to the unfilled blend, which suggests that the clay may exert some compatibilizing action. Such a beneficial effect of the OMMT endures up to the glass transition of PLA. he testing methods such as CCT, RCT, FCT, COBB, bursting etc. are supported by statistical technique and do not provide accurate results. The reason is the deviation of testing results. The same problem can be defined at the classification of different paper materials and qualities. This paper describes a new possible testing method to analyze the chemical and thermo-analytical nature of papers. This method can be used to specify effectively the limits of a given paper quality using in packaging industry and can help to ensure the exact traceability of paper identification. The results show that the this method on the one hand can be helpful to testing the paper during packaging producing process on the other hand after using as a packaging. To the testing a DSC measurement device was used as a thermo-analytical method to observe new specifics of paper based packaging

Assessment of Recycled PLA-Based Filament for 3D Printing

n/

Dielectric behavior of biopolymer based composites containing multi wall carbon nanotubes: Effect of filler content and aspect ratio

Multi wall carbon nanotubes (MWCNTs) with different aspect ratios (30, 105 and 667) were included in a commercial fully biodegradable blend using melt mixing. Samples of composite systems prepared by hot molding and containing up to 1.2 vol% of MWCNTs were studied by means of DC electrical resistivity and dielectric spectroscopy in order to enhance effect of filler content and aspect ratio on their dielectric behavior. Raman spectroscopic investigations and morphological observations were also performed in order to correlate dielectric behavior with surface carbon nanotubes features and to check the actual level of dispersion of carbon nanotubes under the applied processing conditions. Results emphasized that the carbon nanotubes aspect ratio and their surface regularity determine the electrical properties of composites because they strongly influence percolation thresholds, dielectric permittivity and dissipation factor of produced materials. A satisfying dispersion of the filler seems to be achieved under the employed processing conditions. These preliminary results demonstrates possible applications of this type of biobased systems in many applications going from stress control to devices for high storage energy

Ultrafine Magnetite Nanopowder: Synthesis, Characterization, and Preliminary Use as Filler of Polymethylmethacrylate Nanocomposites

Magnetite (Fe3O4) nanoparticles prepared by microwave-assisted hydrothermal synthesis have been characterized in terms of morphological and structural features. Electron micrographs collected in both scanning (SEM) and transmission (TEM) modes and evaluations of X-ray powder diffraction (XRD) patterns have indicated the achievement of a monodispersed crystallite structure with particles having an average size around 15–20 nm. Structural investigations by Micro-Raman spectroscopy highlighted the obtainment of magnetite nanocrystals with a partial surface oxidation to maghemite (γ-Fe3O4). Preliminary attention has been also paid to the use of these magnetite nanoparticles as filler for a commercial polymethylmethacrylate resin. Hybrid formulations containing up to 3 wt% of nanoparticles were prepared by melt blending and characterized by calorimetric and thermogravimetric tests. For sake of comparison, same formulations containing commercial Fe3O4nanoparticles are also reported. Calorimetric characterization indicates an increase of both glass transition temperature and thermal stability of the nanocomposite systems when loaded with the synthesized magnetite nanoparticles rather then loaded with the same amount of commercial Fe3O4. This first observation represents just one aspect of the promising potentiality offered by the novel magnetic nanoparticles when mixed with PMMA

Melt-spun bioactive sutures containing nanohybrids for local delivery of anti-inflammatory drugs.

In this work, a novel concept is introduced in drug-eluting fibres to ensure a good control of drug delivery features and wide applicability to different bioactive compounds. Composite bioactive sutures based on fibre grade poly(ε-caprolactone) (PCL) and loaded with the anti-inflammatory drug Diclofenac (Dic) or a Dic nanohybrid where the drug is intercalated in a synthetic hydrotalcite (Mg/Al hydroxycarbonate) (HT-Dic) were developed. Fibres were prepared by melt-spinning at different PCL/HT-Dic/Dic ratios and analysed in terms of morphology, mechanical properties and drug release features. Results emphasized that tensile properties of fibres are clearly affected by Dic or HT-Dic addition, while the presence of knots has limited influence on the mechanical behaviour of the sutures. Release of Dic strongly depends on how Dic is loaded in the fibre (as free or nanohybrid) whereas the combination of free Dic and HT-Dic can allow a further tuning of release profile. In vivo experiments show a reduction of inflammatory responses associated with Dic-loaded fibers. Thus, a proof of principle is provided for a novel class of bioactive sutures integrating advanced controlled-release technologies