PC/ABS BLENDS:COMPATIBILIZATION AND MECHANICAL-BEHAVIOR

PC/ABS(M) blends, encompassing the whole composition range between pure PC and ABS(M), were prepared by melt-mixing in a Brabender-like apparatus. Thermal, mechanical and impact tests were performed on compression moulded specimens. Inward Tg shifts were

Formulações nanobiotecnológicas para vetorização da Curcumina e seus derivados

Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências Farmacêuticas

Mathematical modelling and optimisation of the formulation and manufacture of aggregate food products

In this PhD study, mathematical modelling and optimisation of granola production has been carried out. Granola is an aggregated food product used in breakfast cereals and cereal bars. It is a baked crispy food product typically incorporating oats, other cereals and nuts bound together with a binder, such as honey, water and oil, to form a structured unit aggregate. In this work, the design and operation of two parallel processes to produce aggregate granola products were incorporated: i) a high shear mixing granulation stage (in a designated granulator) followed by drying/toasting in an oven. ii) a continuous fluidised bed followed by drying/toasting in an oven. In addition, the particle breakage of granola during pneumatic conveying produced by both a high shear granulator (HSG) and fluidised bed granulator (FBG) process were examined. Products were pneumatically conveyed in a purpose built conveying rig designed to mimic product conveying and packaging. Three different conveying rig configurations were employed; a straight pipe, a rig consisting two 45° bends and one with 90° bend. It was observed that the least amount of breakage occurred in the straight pipe while the most breakage occurred at 90° bend pipe. Moreover, lower levels of breakage were observed in two 45° bend pipe than the 90° bend vi pipe configuration. In general, increasing the impact angle increases the degree of breakage. Additionally for the granules produced in the HSG, those produced at 300 rpm have the lowest breakage rates while the granules produced at 150 rpm have the highest breakage rates. This effect clearly the importance of shear history (during granule production) on breakage rates during subsequent processing. In terms of the FBG there was no single operating parameter that was deemed to have a significant effect on breakage during subsequent conveying. A population balance model was developed to analyse the particle breakage occurring during pneumatic conveying. The population balance equations that govern this breakage process are solved using discretization. The Markov chain method was used for the solution of PBEs for this process. This study found that increasing the air velocity (by increasing the air pressure to the rig), results in increased breakage among granola aggregates. Furthermore, the analysis carried out in this work provides that a greater degree of breakage of granola aggregates occur in line with an increase in bend angle.

Optimisation of granola breakfast cereal manufacturing process by wet granulation and pneumatic conveying

This study has considered the optimisation of granola breakfast cereal manufacturing processes by wet granulation and pneumatic conveying. Granola is an aggregated food product used as a breakfast cereal and in cereal bars. Processing of granola involves mixing the dry ingredients (typically oats, nuts, etc.) followed by the addition of a binder which can contain honey, water and/or oil. In this work, the design and operation of two parallel wet granulation processes to produce aggregate granola products were incorporated: a) a high shear mixing granulation process followed by drying/toasting in an oven. b) a continuous fluidised bed followed by drying/toasting in an oven. In high shear granulation the influence of process parameters on key granule aggregate quality attributes such as granule size distribution and textural properties of granola were investigated. The experimental results show that the impeller rotational speed is the single most important process parameter which influences granola physical and textural properties. After that binder addition rate and wet massing time also show significant impacts on granule properties. Increasing the impeller speed and wet massing time increases the median granule size while also presenting a positive correlation with density. The combination of high impeller speed and low binder addition rate resulted in granules with the highest levels of hardness and crispness. In the fluidised bed granulation process the effect of nozzle air pressure and binder spray rate on key aggregate quality attributes were studied. The experimental results show that a decrease in nozzle air pressure leads to larger in mean granule size. The combination of lowest nozzle air pressure and lowest binder spray rate results in granules with the highest levels of hardness and crispness. Overall, the high shear granulation process led to larger, denser, less porous and stronger (less likely to break) aggregates than the fluidised bed process. The study also examined the particle breakage of granola during pneumatic conveying produced by both the high shear granulation and the fluidised bed granulation process. Products were pneumatically conveyed in a purpose built conveying rig designed to mimic product conveying and packaging. Three different conveying rig configurations were employed; a straight pipe, a rig consisting two 45° bends and one with 90° bend. Particle breakage increases with applied pressure drop, and a 90° bend pipe results in more attrition for all conveying velocities relative to other pipe geometry. Additionally for the granules produced in the high shear granulator; those produced at the highest impeller speed, while being the largest also have the lowest levels of proportional breakage while smaller granules produced at the lowest impeller speed have the highest levels of breakage. This effect clearly shows the importance of shear history (during granule production) on breakage during subsequent processing. In terms of the fluidised bed granulation, there was no single operating parameter that was deemed to have a significant effect on breakage during subsequent conveying. Finally, a simple power law breakage model based on process input parameters was developed for both manufacturing processes. It was found suitable for predicting the breakage of granola breakfast cereal at various applied air velocities using a number of pipe configurations, taking into account shear histories.

Challenges in modelling biofluids in microchannels

This paper presents the challenges encountered in modelling biofluids in microchannels. In particular blood separation implemented in a T-microchannel device is analysed. Microfluids behave different from the counterparts in the microscale and a different approach has been adopted here to model them, which emphasize the roles of viscous forces, high shear rate performance and particle interaction in microscope. A T-microchannel design is numerically analysed by means of computational fluid dynamics (CFD) to investigate the effectiveness of blood separation based on the bifurcation law and other bio-physical effects. The simulation shows that the device can separate blood cells from plasma.

Integrated biomedical device for blood preparation

The separation of red blood cells from plasma flowing in microchannels is possible by bio-physical effects such as an axial migration effect and Zweifach-Fung bifurcation law. In the present study, subchannels are placed alongside a main channel to collect cells and plasma separately. The addition of a constriction in the main microchannel creates a local high shear force region, forcing the cells to migrate and concentrate towards the centre of the channel. The resulting lab-on-a-chip was manufactured using biocompatible materials. Purity efficiency was measured for mussel and human blood suspensions as different parameters including flow rate and geometries of parent and daughter channels were varied.

Thixotropic studies of lead-based solder, lead-free solder and conductive adhesive pastes

The stencil printing process is an important process in the assembly of Surface Mount Technology (SMT)devices. There is a wide agreement in the industry that the paste printing process accounts for the majority of assembly defects. Experience with this process has shown that typically over 60% of all soldering defects are due to problems associated with the flow properties of solder pastes. Therefore, the rheological measurements can be used as a tool to study the deformation or flow experienced by the pastes during the stencil printing process. This paper presents results on the thixotropic behaviour of three pastes; lead-based solder paste, lead-free solder paste and isotropic conductive adhesive (ICA). These materials are widely used as interconnect medium in the electronics industry. Solder paste are metal alloys suspended in a flux medium while the ICAs consist of silver flakes dispersed in an epoxy resin. The thixotropy behaviour was investigated through two rheological test; (i) hysteresis loop test and (ii) steady shear rate test. In the hysteresis loop test, the shear rate were increased from 0.001 to 100s-1 and then decreased from 100 to 0.001s-1. Meanwhile, in the steady shear rate test, the materials were subjected to a constant shear rate of 0.100, 100 and 0.001s-1 for a period of 240 seconds. All the pastes showed a high degree of shear thinning behaviour with time. This might be due to the agglomeration of particles in the flux or epoxy resin that prohibits pastes flow under low shear rate. The action of high shear rate would break the agglomerates into smaller pieces which facilitates the flow of pastes, thus viscosity is reduced at high shear rate. The solder pastes exhibited a higher degree of structural breakdown compared to the ICAs. The area between the up curve and down curve in the hysteresis curve is an indication of the thixotropic behavior of the pastes. Among the three pastes, lead-free solder paste showed the largest area between the down curve and up curve, which indicating a larger structural breakdown in the pastes, followed by lead-based solder paste and ICA. In a steady shear rate test, viscosity of ICA showed the best recovery with the steeper curve to its original viscosity after the removal of shear, which indicating that the dispersion quality in ICA is good because the high shear has little effect on the microstructure of ICA. In contrast, lead-based paste showed the poorest recovery which means this paste undergo larger structural breakdown and dispersion quality in this paste is poor because the microstructure of the paste is easily disrupted by high shear. The structural breakdown during the application of shear and the recovery after removal of shear is an important characteristic in the paste printing process. If the paste’s viscosity can drop low enough, it may contribute to the aperture filling and quick recovery may prevent slumping.

Study of the rheological behaviour of Sn-Ag-Cu solder pastes and their correlation with printing performance

Solder paste plays an important role in the electronic assembly process by providing electrical, mechanical and thermal bonding between the components and the substrate. The rheological characterisation of pastes is an important step in the design and development of new paste formulations. With the ever increasing trend of miniaturisation of electronic products, the study of the rheological properties of solder pastes is becoming an integral part in the R&D of new paste formulations and in the quality monitoring and control during paste manufacture and electronic assembly process. This research work outlines some of the novel techniques which can be successfully used to investigate the rheology of leadfree solder pastes. The report also presents the results of the correlation of rheological properties with solder paste printing performance. Four different solder paste samples (namely paste P1, P2, P3 and P4) with different flux vehicle systems and particle size distributions were investigated in the study. As expected, all the paste samples showed shear thinning behaviour. Although the samples displayed similar flow behaviour at high shear rates, differences were observed at low shear rates. In the stencil printing trials, round deposits showed better results than rectangular deposits in terms of paste heights and aperture filling. Our results demonstrate a good correlation between higher paste viscosity and good printing performance. The results of the oscillatory and thixotropy tests were also successfully correlated to the printing behaviour of solder paste.

Co-melt fluidised bed granulation of pharmaceutical powders: Improvements in drug bioavailability

This study investigates the use of co-melt fluidised bed granulation for the agglomeration of model pharmaceutical powders, namely, lactose mono-hydrate, PEG 10000, poly-vinyl pyrolidone and ibuprofen as a model drug. Granulation within the co-melt system was found to follow a nucleationâ??steady growthâ??coating regime profile. Using high molecular weight PEG binder, the granulation mechanism and thus the extent of granulation was found to be significantly influenced by binder viscosity. The compression properties of the granulate within the hot fluidised bed were correlated using a novel high temperature experimental procedure. It was found that the fracture stress and fractural modulus of the materials under hot processing conditions were orders of magnitude lower than those measured under ambient conditions. A range of particle velocities within the granulator were considered based on theoretical models. After an initial period of nucleation, the Stokes deformation number analysis indicated that only velocities within the high shear region of the fluidised bed were sufficient to promote significant granule deformation and therefore, coalescence. The data also indicated that larger granules de-fluidised preventing agglomeration by coalescence. Furthermore, experimental data indicated that dissipation of the viscous molten binder to the surface was the most important factor in the latter stages of the granulation process. From a pharmaceutical perspective the inclusion of the model drug, ibuprofen, combined with PVP in the co-melt process proved to be highly significant. It was found that using DSC analysis on the formulations that the decrease in the heat of fusion associated with the melting of ibuprofen within the FHMG systems may be attributed to interaction between PVP and ibuprofen through inter-molecular hydrogen bonding. This interaction decreases the crystallinity of ibuprofen and facilitates solubilisation and bioavailability within the solid matrix.

Hot-melt extrusion technology and pharmaceutical application

The use of hot-melt extrusion (HME) within the pharmaceutical industry is steadily increasing, due to its proven ability to efficiently manufacture novel products. The process has been utilized readily in the plastics industry for over a century and has been used to manufacture medical devices for several decades. The development of novel drugs with poor solubility and bioavailability brought the application of HME into the realm of drug-delivery systems. This has specifically been shown in the development of drug-delivery systems of both solid dosage forms and transdermal patches. HME involves the application of heat, pressure and agitation through an extrusion channel to mix materials together, and subsequently forcing them out through a die. Twin-screw extruders are most popular in solid dosage form development as it imparts both dispersive and distributive mixing. It blends materials while also imparting high shear to break-up particles and disperse them. HME extrusion has been shown to molecularly disperse poorly soluble drugs in a polymer carrier, increasing dissolution rates and bioavailability. The most common difficulty encountered in producing such dispersions is stabilization of amorphous drugs, which prevents them from recrystallization during storage. Pharmaceutical industrial suppliers, of both materials and equipment, have increased their development of equipment and chemicals for specific use with HME. Clearly, HME has been identified as an important and significant process to further enhance drug solubility and solid-dispersion production. © 2012 Future Science Ltd.

Design, production and characterisation of granular adsorbent material for arsenic removal from contaminated wastewater

The objective of this research was to design granulated iron oxide for the adsorption of heavy metals from wastewater. Polyvinyl acetate (PVAc) was chosen as a suitable binder; as it is water insoluble. Initial experiments on selection of suitable solvent of the polymer were carried out using three solvents namely; methanol, acetone and toluene. Based on the initial tests on product yield and mechanical strength, acetone was selected as the solvent for the polyvinyl acetate binder. Design of experiment was then used to investigate the influence of granulation process variables; impeller speed, binder concentration and liquid to solid ratio on the properties of the granular materials. The response variables in the study were granules mean size, stability in water and granule strength. The results showed that the combination of high impeller speed and high binder concentration favour the formation of strong and stable granules. Results also showed that leaching of the binder into the simulated was water was negligible. Trial adsorption experiments carried out using the strongest and most stable iron oxide granules produced in this work showed removal efficiency of around 70% of synthetic arsenic solutions with initial concentration of 1000 ppb.

Régulation de la fonction plaquettaire par un aptamère dirigé contre le domaine A1 du facteur Von-Willebrand

Drs Dandachli and Arzamendi contributed equally to this work.

Caractérisation et évaluation de textiles antifongiques

Hypothèse: L’impression sur textile d’une formulation de microparticules lipidiques avec un principe actif (éconazole nitrate) permet de conserver ou d’améliorer son activité pharmaceutique ex vivo et in vitro. Méthode: Une formulation de microparticules d’éconazole nitrate (ECN) a été formulée par homogénéisation à haut cisaillement, puis imprimée sur un textile LayaTM par une méthode de sérigraphie. La taille des microparticules, la température de fusion des microparticules sur textile et la teneur en éconazole du tissu ont été déterminées. La stabilité de la formulation a été suivie pendant 4 mois à 25°C avec 65% humidité résiduelle (RH). L’activité in vitro des textiles pharmaceutiques a été mesurée et comparée à la formulation commerciale 1% éconazole nitrate (w/w) sur plusieurs espèces de champignons dont le C. albicans, C. glabrata, C. kefyr, C. luminisitae, T. mentagrophytes et T. rubrum. La thermosensibilité des formulations a été étudiée par des tests de diffusion in vitro en cellules de Franz. L’absorption cutanée de l’éconazole a été évaluée ex vivo sur la peau de cochon. Résultats: Les microparticules d’éconazole avaient des tailles de 3.5±0.1 μm. La température de fusion était de 34.8°C. La thermosensibilité a été déterminée par un relargage deux fois supérieur à 32°C comparés à 22°C sur 6 heures. Les textiles ont présenté une teneur stable pendant 4 mois. Les textiles d’ECN in vitro ont démontré une activité similaire à la formulation commerciale sur toutes ii espèces de Candida testées, ainsi qu’une bonne activité contre les dermatophytes. La diffusion sur peau de cochon a démontré une accumulation supérieure dans le stratum corneum de la formulation textile par rapport à la formulation Pevaryl® à 1% ECN. La thermo-sensibilité de la formulation a permis un relargage sélectif au contact de la peau, tout en assurant une bonne conservation à température ambiante.

Recyclable Short Fibre Reinforced Plastics PP/Nylon and HDPE/Nylon composites

The study shows that standard plastics like polypropylene and high density polyethylene can be reinforced by adding nylon short fibres. Compared to the conventional glass reinforced thermoplastics this novel class of reinforced thermoplastics has the major advantage of recyclability. Hence such composites represent a new spectrum of recyclable polymer composites. The fibre length and fibre diameter used for reinforcement are critical parameters While there is a critical fibre length below which no effective reinforcement takes place, the reinforcement improves when the fibre diameter decreases due to increased surface area.While the fibres alone give moderate reinforcement, chemical modification of the matrix can further improve the strength and modulus of the composites. Maleic anhydride grafting in presence of styrene was found to be the most efficient chemical modification. While the fibre addition enhances the viscosity of the melt at lower shear rates, the enhancement at higher shear rate is only marginal. This shows that processing of the composite can be done in a similar way to that of the matrix polymer in high shear operations such as injection moulding. Another significant observation is the decrease in melt viscosity of the composite upon grafting. Thus chemical modification of matrix makes processing of the composite easier in addition to improving the mechanical load bearing capacity.For the development of a useful short fibre composite, selection of proper materials, optimum design with regard to the particular product and choosing proper processing parameters are most essential. Since there is a co-influence of many parameters, analytical solutions are difficult. Hence for selecting proper processing parameters 'rnold flow' software was utilized. The orientation of the fibres, mechanical properties, temperature profile, shrinkage, fill time etc. were determined using the software.Another interesting feature of the nylon fibre/PP and nylon fibre/HDPE composites is their thermal behaviour. Both nylon and PP degrade at the same temperature in single steps and hence the thermal degradation behaviour of the composites is also being predictable. It is observed that the thermal behaviour of the matrix or reinforcement does not affect each other. Almost similar behaviour is observed in the case of nylon fibre/HDPE composites. Another equally significant factor is the nucleating effect of nylon fibre when the composite melt cools down. In the presence of the fibre the onset of crystallization occurs at slightly higher temperature.When the matrix is modified by grafting, the onset of crystallization occurs at still higher temperature. Hence it may be calculated that one reason for the improvement in mechanical behaviour of the composite is the difference in crystallization behaviour of the matrix in presence of the fibre.As mentioned earlier, a major advantage of these composites is their recyclability. Two basic approaches may be employed for recycling namely, low temperature recycling and high temperature recycling. In the low temperature recycling, the recycling is done at a temperature above the melting point of the matrix, but below that of the fibres while in the high temperature route. the recycling is done at a temperature above the melting points of both matrix and fibre. The former is particularly interesting in that the recycled material has equal or even better mechanical properties compared to the initial product. This is possible because the orientation of the fibre can improve with successive recycling. Hence such recycled composites can be used for the same applications for which the original composite was developed. In high temperature recycling, the composite is converted into a blend and hence the properties will be inferior to that of the original composite, but will be higher than that of the matrix material alone.