Fabrizio Tarterini

Managing heat phenomena in epoxy composites production via graphenic derivatives: synthesis, properties and industrial production simulation of graphene and graphene oxide containing composites

A commercial two-components epoxy resin formulation was successfully modified by adding graphene and related materials (GRMs) and the effect of these nanofillers was assessed on their thermomechanical properties as well as on the simulation of their industrial application for the production of thick composites objects with interesting results. GMRs were added in different concentrations in order to improve thermo-mechanical properties of the nano-composite thermoset. Different dispersion methods were taken into account in order to produce stable long-lasting dispersion of the GRMs, that can withstand a commercial shelf life. Addition of the GRMs improves the glass transition temperature of the nanocomposite up to 20 °C with respect to the plain commercial formulation, and both stress and elongation at break increase up to almost 4 times the original values. Moreover, the industrial curing of some of the more promising modified resins was computer-simulated when the two-components resins are used to produce a carbon-fibre reinforced thick composite beam. Simulation results show that some of the applied GRMs helps reducing or even completely preventing the overheat phenomena that are well renown to induce significant thermal stresses negatively affecting the final object performances. These interesting effects would contribute reducing the time required for a single industrial production cycle, since no time for overheat dispersion is required, thus helping increasing the production rate.

Image analysis of lutrol/gelucire/olanzapine microspheres prepared by ultrasound-assisted spray congealing

Nine systems were prepared containing Gelucire 50/13 and various amounts (9-18-36-45% w/w) of Lutrol F68 and F127 in the presence and in the absence of 10% w/w of olanzapine and formulated as a solid dispersion in the form of microspheres by ultrasound (US)-assisted spray congealing. Thermal analysis, using differential scanning calorimetry (DSC) and thermomicroscopy (HSM), suggested the presence of particles of reduced size of olanzapine precipitated inside the microspheres. The microspheres were also studied by means of electron microscopy (SEM) for their shape and aspect, by some image analysis parameters (fractal dimension) and using Energy-dispersive X-ray (X-EDS) and micro-Raman spectroscopy to qualitatively evaluate the composition of different points of the surface. The surface of the microspheres displayed a non-homogeneous distribution of the drug by the presence of wart-like protuberances, whose number increases as the Lutrol content of the systems increases. The same systems in the absence of US, obtained after cooling the molten mixtures, lack these structures and only a very few of them can be found. The blooming of the surface was hypothesized as related to crystallization or phase de-mixing or lipid component diffusion of the carrier mixture inside the cooling mass subjected to ultrasound vibration. Ultrasounds accelerate the physical changes concerning carriers and drug, outlining the importance of ultrasound to achieve stability for formulations of this type. The microspheres de-aggregate on contact with the dissolution medium and release the drug with a bimodal mode according to the Lutrol content.

Release Problems for Nifedipine in the Presence of Soluplus

Nifedipine/soluplus co-precipitates were prepared at 1:9 and 1:1 weight ratios, using the solvent method, with the aim to obtain an improvement of the drug release. The release, though accelerated with respect to physical mixtures and pure drug, resulted slow with respect to similar systems containing soluplus and are characterized by the appearance in suspension of micro-particulates that, at the optical microscope, revealed a large variety of shapes typical of flower-like aggregates, not previously reported. For comparison systems were also prepared with PVP K30 and sucrester P1670 and two mixtures, without any evidence of this last phenomenon. The systems were studied by thermal (differential scanning calorimetry – DSC, thermomicroscopy – HSM) and spectroscopic (SEM, FT-IR, micro-Raman) analysis. Slow release of nifedipine and formation of colloidal micro-particulates were hypothesized due to the gelling tendency of soluplus associated to drug/polymer multi-site-interactions: when one of these parameters is absent in the system the two phenomena could not be observed together, such as in the case of PVP K30 or sucrester P1670, when used as carriers for nifedipine release. *Corresponding author: Adamo Fini, Professor, Department of FABIT, University of Bologna, Via San Donato 15, 20127 Bologna, Italy, Tel: +00390512095655; Fax: +00390512095652; E-mail: adamo.fini@unibo.it Citation: Cavallari, C., et al. Release Problems for Nifedipine in the Presence of Soluplus. (2016) J Pharm Pharmaceutics 3(2): 113. Release Problems for Nifedipine in the Presence of Soluplus Cristina Cavallari1, Selenia Ternullo2, Fabrizio Tarterini3, Adamo Fini1* Received date: April 19, 2016 Accepted date: May 31, 2016 Published date: June 06, 2016 DOI: 10.15436/2377-1313.16.020 1 Fini, A., et al. J Pharm Pharmaceutics | volume 3: issue 2 2 to prepare co-precipitate of drug by hot-melt extrusion[16]. It represents a hydrophilic non-ionic multipurpose carrier for its ability to act as polymer matrix former suitable for co-precipitates; and is considered as a member of the fourth generation of co-precipitate carriers[17]. Due to hydrophilic and hydrophobic functionalities in its chains, soluplus displays solubilising properties through micelle formation in solution (CMC 7.6 mg/l)[18]. But it also exhibits a lower critical solution temperature (LCST) near 40°C[19], above which it aggregates into larger micelles, displays gel-forming ability that makes turbid the releasing medium[16]. As a consequence the final result for this carrier, proposed to improve the release of the embedded drug, could depend on the relative weight of these opposite parameters. In the case of the association nifedipine/soluplus literature has been mainly concerned with the study of interaction between the drug and the polymer, the miscibility limits, the effects of the preparing techniques and aging on dissolution behavior[12-15]. The original aim of our research was to compare a range of hydrophilic carriers, including soluplus, such as Gelucires, PEGs and Lutrols, in the nifedipine release improvement from co-precipitates. In the present paper we preferred a more in-depth examination of the soluplus system, since nifedipine experiments unexpected release problems in the presence of soluplus, unlike other carriers; moreover an unusual formation of particulates, different in shape and size from the starting particles, was observed during the release test. While few examples are reported in the literature for slow drug release in the presence of soluplus, presence of this type of particulates was not observed or reported in previous papers, which separately referred to nifedipine or to soluplus. To interpret this fact, for comparison, also PVP and sucrester P1670 were employed as carriers for nifedipine, alone or in mixture with soluplus. All the systems thus prepared were examined by thermal (DSC, TGA, HSM) and spectroscopic (FT-IR, Raman, SEM) analysis and a mechanism was hypothesized for the slow release and the formation flower-like particulates during the release tests. Materials and Methods Chemicals Nifedipine was a commercial sample of pharmaceutical grade: its thermogram fits that of a commercial sample; soluplus, sucrester P1670 and PVP K30 were commercial samples of the highest degree available (Sigma, Milan, and Italy). Preparation of the physical mixtures Physical mixtures were prepared mixing powders of the same particle size range of nifedipine and each carrier in order to obtain the formulations shown in (Table 1). Table 1: Weight percent composition of the formulations examined Nifedipine Soluplus PVP Sucrester

Dry Sliding Behaviour of Peo (Plasma Electrolytic Oxidation) Treated AA 2618/20% Al2O3p Composite

The present study focuses on the influence of the PEO (Plasma Electrolytic Oxidation) treatment on the tribological behaviour of the AA2618/20 % vol. Al2O3p composite, dry sliding against induction hardened UNI C55 steel. Particle-reinforced Al based composites offer a higher wear resistance by comparison with the corresponding unreinforced alloys, however, the presence of critical loads and/or velocities which lead to transition towards severe wear regime, was often observed. In such conditions, the composite can show higher wear rates than those of unreinforced alloys. For this reason, surface modifications, such as PEO, might contribute to improve wear resistance. In this paper, topography, microstructure, phase constitution and surface hardness of the PEO-treated composite were investigated and its tribological behaviour was studied by dry sliding tests using a block-on-ring tribometer. The results were compared with those from the uncoated composite, demonstrating a very positive effect of the PEO treatment, which moved transitions from mild to severe wear towards more severe test conditions, in terms of both load and velocity.

Friction Stir Welding of Aluminium Based Composites Reinforced with Al2O3 Particles

This paper presents the results of microstructural and mechanical characterization of Friction Stir Welding joints of two aluminum-based particles reinforced composites. The composites were FSW in the extruded and T6 heat treated condition. No post-weld heat treatment was carried out on the FSW joints. Hardness, tensile, low-cycle fatigue and impact tests were carried out. Microstructural and fractographic characterization were performed both on the base and FSW material, in order to investigate the effect of the solid-state welding process on the reinforcement particles and aluminum matrix. The FSW produced high quality joints with good microstructural characteristics: the welded zone displayed a refinement of the Al matrix grain size and reinforcement particles, and a better particle distribution. The FSW specimens showed high efficiency, both in the tensile, impact and fatigue tests.

On the Evaluation of the Service Life of Shaft-Bushing Tribosystems at Low Speed

This work presents the results of a set of endurance tests performed on steel to steel shaft/bushing tribosystems, without re-lubrication after start-up. The experimental procedure was designed in order to provide simulation for the operative conditions of earthmoving machinery. For this purpose, a new testing machine was specifically manufactured so as to accommodate shaft/bushing assemblies up to a nominal coupling diameter of 90 mm, with a maximum radial load capability of 300 kN. The machine was operated in alternating rotation, with a span angle of 180 degrees, at an angular speed of 10 rpm. The effects of contact pressure intensity were investigated, as well as the effects of grease lubrication type and of the geometry of grease breeding grooves that were located on the bushings inner surface. The tribology behaviour of the tested assemblies was quantified by means of the transmitted torque, grease temperature at the surface of contact and the metallographic analysis of wear out surfaces.