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Khosrow Khodabakhshi - One of the best experts on this subject based on the ideXlab platform.

  • Anionic Polymerisation of caprolactam at the small-scale via DSC investigations
    Journal of Thermal Analysis and Calorimetry, 2014
    Co-Authors: Khosrow Khodabakhshi, Marianne Gilbert, Saeed Fathi, Philip Dickens
    Abstract:

    This work was part of a major project aiming to produce polyamide 6 parts using an additive manufacturing process. This is by manufacturing 3D parts layer by layer. The influence of heating strategy (heating rate, cooling rate and maximum temperature) on Anionic Polymerisation of caprolactam in a small-scale was investigated by means of differential scanning calorimetry (DSC). The relationship between heating rate and the Polymerisation–crystallisation processes was determined. Two different catalyst/activator compositions were used to study the influence of a di-functional activator on Polymerisation. Results showed that unlike cooling rate, the heating rate and maximum heating temperature had a major effect on the final properties of polymer such as crystallinity, monomer conversion and polymer chains regularity. Using a di-functional activator resulted in slowing down the crystallisation process due to the enhanced rate of branching.

  • Anionic polymarisation of caprolactam: an approach to optimising thr Polymerisation condition to be used in the jetting process
    2011
    Co-Authors: Khosrow Khodabakhshi
    Abstract:

    The main aim of this project was to investigate the possibility of manufacturing 3D parts of polyamide (nylon or PA) 6 by inkjetting its monomer caprolactam (CL). The principle of this process was similar to the other rapid prototype (RP) and rapid manufacturing (RM) processes in which a 3D part is manufactured by layer on layer deposition of material. PA6 was used as the thermoplastic polymer in this work because of its good properties and also because PA6 can be produced by heating its monomer (i.e. plus catalyst and activator) in a short time. Two Polymerisation mixtures of CL-catalyst (mixture A) and CL-activator (mixture B) are intended to be jetted separately using conventional jetting heads and polymerise shortly after heating. Anionic Polymerisation of CL (APCL) was investigated in the bulk and on a smaller scale. Sodium caprolactamate (CLNa and C10) and caprolactam magnesium bromide (CLMgBr) were used as catalysts and N-acetylcaprolactam (ACL) and a di-functional activator (C20) were used as activators. The influence of Polymerisation conditions was investigated and optimised. These were catalyst-activator concentration, Polymerisation temperature and the influence of the Polymerisation atmosphere. The physical properties (monomer conversion, crystallinity, and viscosity average molecular weight) of PA6 samples produced using each catalyst-activator combinations were measured and compared. Small scale Polymerisation was carried out using a hotplate, by hot stage microscopy and using differential scanning calorimetry (DSC). The influence of heating strategy on small scale Polymerisation was studied using DSC. The Polymerisation mixture compositions were characterised using rheometry, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and optical microscopy to investigate their suitability in jetting for using the available jetting heads. It was shown that the combination of CLMgBr-ACL resulted in fast Polymerisation which was not sensitive to moisture. The C10-C20 combination resulted in fast Polymerisation with the best properties in a protected environment (nitrogen); however, the Polymerisation was affected by moisture in air and the properties of polymer produced and rate of Polymerisation decreased in air. Polymers produced using CLNa-ACL had the poorest properties and Polymerisation did not occur in air. Material characterisation showed that micro-crystals of CLMgBr existed in CLMgBr-CL mixture at the jetting temperature (80oC) which were too large to be jetted. However, the mixture of C10 in CL could be partially jetted. The activator mixtures had similar properties to CL and were easily jetted. Drop on drop Polymerisation was carried out by dripping droplets of mixtures A and B (at 80oC) on top of each other on a hotplate at the Polymerisation temperature. Small scale Polymerisation in a DSC showed that the monomer conversion increased with increase in Polymerisation temperature from 140oC to 180oC and decreased from 180oC to 200oC. The crystallinity of the polymer produced in the DSC decreased with increase in Polymerisation temperature. Hot stage microscopy produced evidence for simultaneous Polymerisation and crystallisation processes on heating. Small scale Polymerisation in an oven and analysed by DSC showed that increasing catalystactivator concentration resulted in increasing monomer conversion and decrease in crystallinity. Monomer conversion also increased with increase in Polymerisation temperature and Polymerisation time. Comparison between small scale and bulk Polymerisations shows a good agreement between the two Polymerisation rates. This shows that the Polymerisation mechanism did not change significantly when the quantity of materials was reduced to less than 20mg. Finally, the Polymerisation was carried out in a DSC after jetting C10-CL and C20-CL mixtures into a DSC pan using a jetting system, which was made in another work

Philip Dickens - One of the best experts on this subject based on the ideXlab platform.

  • Anionic Polymerisation of caprolactam at the small-scale via DSC investigations
    Journal of Thermal Analysis and Calorimetry, 2014
    Co-Authors: Khosrow Khodabakhshi, Marianne Gilbert, Saeed Fathi, Philip Dickens
    Abstract:

    This work was part of a major project aiming to produce polyamide 6 parts using an additive manufacturing process. This is by manufacturing 3D parts layer by layer. The influence of heating strategy (heating rate, cooling rate and maximum temperature) on Anionic Polymerisation of caprolactam in a small-scale was investigated by means of differential scanning calorimetry (DSC). The relationship between heating rate and the Polymerisation–crystallisation processes was determined. Two different catalyst/activator compositions were used to study the influence of a di-functional activator on Polymerisation. Results showed that unlike cooling rate, the heating rate and maximum heating temperature had a major effect on the final properties of polymer such as crystallinity, monomer conversion and polymer chains regularity. Using a di-functional activator resulted in slowing down the crystallisation process due to the enhanced rate of branching.

Saeed Fathi - One of the best experts on this subject based on the ideXlab platform.

  • Anionic Polymerisation of caprolactam at the small-scale via DSC investigations
    Journal of Thermal Analysis and Calorimetry, 2014
    Co-Authors: Khosrow Khodabakhshi, Marianne Gilbert, Saeed Fathi, Philip Dickens
    Abstract:

    This work was part of a major project aiming to produce polyamide 6 parts using an additive manufacturing process. This is by manufacturing 3D parts layer by layer. The influence of heating strategy (heating rate, cooling rate and maximum temperature) on Anionic Polymerisation of caprolactam in a small-scale was investigated by means of differential scanning calorimetry (DSC). The relationship between heating rate and the Polymerisation–crystallisation processes was determined. Two different catalyst/activator compositions were used to study the influence of a di-functional activator on Polymerisation. Results showed that unlike cooling rate, the heating rate and maximum heating temperature had a major effect on the final properties of polymer such as crystallinity, monomer conversion and polymer chains regularity. Using a di-functional activator resulted in slowing down the crystallisation process due to the enhanced rate of branching.

  • Fundamental investigation on inkjet printing of reactive nylon materials
    2011
    Co-Authors: Saeed Fathi
    Abstract:

    Several additive manufacturing processes have been developed for plastic parts. However, there is an ongoing interest to increase the functionality of these parts which are mainly considered as prototypes due to the material and process limitations. This research investigated a novel additive approach for producing a functional engineering plastic, nylon 6. The idea was to combine inkjet printing technology and Anionic Polymerisation of caprolactam by depositing mixtures of caprolactam with activator and catalyst on top of each other under the appropriate conditions. An experimental setup was integrated based on two identical jetting assemblies with pneumatic and thermal control, synchronised with a deposition system for the reaction of the mixtures upon radiation heating. Different offline material characterisation and inline process monitoring methods were employed to obtain an understanding of the material behaviour at each stage of the research. These included the use of high speed imaging, fluorescent microscopy, particle tracking and image analysis tools. Samples were monitored before and after the drop-on-drop deposition and radiation heating, and then assessed by thermal analysis to find the appropriate conditions for the reaction. It was found that although some monomer conversion was achieved, the rates were much less than with the bulk Polymerisation approach. Jetting of thousands of tiny droplets in air could have resulted in a very high monomer deactivation. This highlighted the importance of the environment as a more significant parameter for jetting of nylon 6 compared with the conventional method

Elder Judith - One of the best experts on this subject based on the ideXlab platform.

  • PMMA Clay Nanocomposites
    2009
    Co-Authors: Elder Judith
    Abstract:

    Polymer clay nanocomposites (PCN) of poly(methyl methacrylate) (PMMA) and clay, were synthesised in-situ using a free radical suspension Polymerisation technique. The weight fraction of clay in the PCN was systematically varied in order to understand the effect of clay on the physical properties of the resulting PCNs. However, unexpectedly it was found that the weight fraction of clay had a dramatic impact upon the molecular weight of the polymer matrix and a relationship between clay concentration and polymer molecular weight was established. Furthermore, it was also found that the change in molecular weight was dependent upon the clay type. Three different clay types were investigated; an organically modified montmorillonite (Cloisite 15a), a synthetic clay (Laponite RD) and a PEO modified Laponite RD. To produce the modified Laponite RD, mono amino PEO was synthesised via Anionic Polymerisation using dimethyl ethanol amine as an initiator. The modification of the Laponite RD clay took place in the reaction flask prior to the suspension Polymerisation of the PCN. The PCN were characterised using size exclusion chromatography (SEC), X-ray diffraction (XRD), transmission electron microscopy (TEM) and oscillatory shear rheology. Morphological studies of the PCN showed that the extent of clay dispersion depended on the clay type. Within the PMMA/Laponite RD nanocomposites an unusual network structure was formed, which appeared to be continuous throughout the material. Thermal properties of the PCN were investigated using DSC, TGA and Microcalorimetry. From oscillatory shear rheology, the full master curves for the PCN were obtained by applying the time-temperature superposition (TTS) principle. To quantify the effect of the clay upon the rheology, the experimental data was compared to the time dependent diffusion model of Des Cloizeaux for polydisperse polymer melts, which enables polydispersity to be incorporated through the use of the molecular weight distribution obtained via SEC

  • PMMA clay nanocomposites
    2009
    Co-Authors: Elder Judith
    Abstract:

    Polymer clay nanocomposites (PCN) of poly(methyl methacrylate) (PMMA) and clay, were synthesised in-situ using a free radical suspension Polymerisation technique. The weight fraction of clay in the PCN was systematically varied in order to understand the effect of clay on the physical properties of the resulting PCNs. However, unexpectedly it was found that the weight fraction of clay had a dramatic impact upon the molecular weight of the polymer matrix and a relationship between clay concentration and polymer molecular weight was established. Furthermore, it was also found that the change in molecular weight was dependent upon the clay type. Three different clay types were investigated; an organically modified montmorillonite (Cloisite 15a), a synthetic clay (Laponite RD) and a PEO modified Laponite RD. To produce the modified Laponite RD, mono amino PEO was synthesised via Anionic Polymerisation using dimethyl ethanol amine as an initiator. The modification of the Laponite RD clay took place in the reaction flask prior to the suspension Polymerisation of the PCN. The PCN were characterised using size exclusion chromatography (SEC), X-ray diffraction (XRD), transmission electron microscopy (TEM) and oscillatory shear rheology. Morphological studies of the PCN showed that the extent of clay dispersion depended on the clay type. Within the PMMA/Laponite RD nanocomposites an unusual network structure was formed, which appeared to be continuous throughout the material. Thermal properties of the PCN were investigated using DSC, TGA and Microcalorimetry. From oscillatory shear rheology, the full master curves for the PCN were obtained by applying the time-temperature superposition (TTS) principle. To quantify the effect of the clay upon the rheology, the experimental data was compared to the time dependent diffusion model of Des Cloizeaux for polydisperse polymer melts, which enables polydispersity to be incorporated through the use of the molecular weight distribution obtained via SEC.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Shamsudin Suriani - One of the best experts on this subject based on the ideXlab platform.

  • The Synthesis and Characterisation of Dendritic Macromolecules for Drug Delivery Application
    'University of Sheffield Conference Proceedings', 2012
    Co-Authors: Shamsudin Suriani
    Abstract:

    Today, drugs used in treating disease are almost all hydrophobic, which makes them unattractive for applying to patients. To overcome this problem, an amphiphilic macromolecule was designed which can deliver drugs to the specific targeted area. Therefore, this study focuses on the synthesis of water soluble hyperbranched polymers and their application in drug delivery systems. The first part of the thesis describes the synthesis of water soluble hyperbranched polymers by the Anionic-Polymerisation technique, with p-nitrophenol as the core and glycidol as the monomer. The core is important to control the molecular weight of the hyperbranched polymer. We then produced five different molecular weights by varying the core to monomer ratio, which produced hyperbranched polymers with molecular weights of 4000 Da, 8000 Da, 12500 Da, 27000 Da and 50000 Da, and four different concentrations of each molecular weight, 1.00 x 10-4 M, 2.00 x 10-4 M, 4.00 x 10-4 M and 6.00 x 10-4 M. To investigate the performance of the hyperbranched polymers, four different hydrophobic molecules were studied. The molecules were naphthalene, ibuprofen, tetracarboxyphenyl porphyrin (TCPP) and anti-prion drug. Encapsulation studies showed the concentration of each molecule increased with an increase in molecular weight and concentration of the hyperbranched polymer The functionalisation of folic acid on the surface of the hyperbranched polymer would enhance the effectiveness of the polymer as a drug delivery agent for targeting in cancer treatment. The above macromolecule was synthesised by conjugation with folic acid through poly (ethylene glycol) as spacer. The final chapter of this work describes the encapsulation of two hydrophobic molecules, ibuprofen and tetracarboxyphenyl porphyrin with water soluble PAMAM dendrimers. PAMAM dendrimers from G0.5 to G2.5 were synthesised. The results showed that more drug solubilised, the concentration of both molecules increased with an increase in dendrimer concentration. Then a comparison was made between encapsulation with water soluble hyperbranched polymers and water soluble PAMAM dendrimers. Similar molecular weight was used for both polymers of 4000 Da. For both polymers, the result demonstrated that the concentration of drug rose at 2.00 x 10-4 M and plateaued at a polymer concentration of 6.00 x 10-4 M. It was suggested the above trend was due to the aggregation of polymer. The above studies make a valuable contribution to the development of good drug delivery systems

  • The synthesis and characterisation of dendritic macromolecules for drug delivery application
    2012
    Co-Authors: Shamsudin Suriani
    Abstract:

    Today, drugs used in treating disease are almost all hydrophobic, which makes them unattractive for applying to patients. To overcome this problem, an amphiphilic macromolecule was designed which can deliver drugs to the specific targeted area. Therefore, this study focuses on the synthesis of water soluble hyperbranched polymers and their application in drug delivery systems. The first part of the thesis describes the synthesis of water soluble hyperbranched polymers by the Anionic-Polymerisation technique, with p-nitrophenol as the core and glycidol as the monomer. The core is important to control the molecular weight of the hyperbranched polymer. We then produced five different molecular weights by varying the core to monomer ratio, which produced hyperbranched polymers with molecular weights of 4000 Da, 8000 Da, 12500 Da, 27000 Da and 50000 Da, and four different concentrations of each molecular weight, 1.00 x 10-4 M, 2.00 x 10-4 M, 4.00 x 10-4 M and 6.00 x 10-4 M. To investigate the performance of the hyperbranched polymers, four different hydrophobic molecules were studied. The molecules were naphthalene, ibuprofen, tetracarboxyphenyl porphyrin (TCPP) and anti-prion drug. Encapsulation studies showed the concentration of each molecule increased with an increase in molecular weight and concentration of the hyperbranched polymer The functionalisation of folic acid on the surface of the hyperbranched polymer would enhance the effectiveness of the polymer as a drug delivery agent for targeting in cancer treatment. The above macromolecule was synthesised by conjugation with folic acid through poly (ethylene glycol) as spacer. The final chapter of this work describes the encapsulation of two hydrophobic molecules, ibuprofen and tetracarboxyphenyl porphyrin with water soluble PAMAM dendrimers. PAMAM dendrimers from G0.5 to G2.5 were synthesised. The results showed that more drug solubilised, the concentration of both molecules increased with an increase in dendrimer concentration. Then a comparison was made between encapsulation with water soluble hyperbranched polymers and water soluble PAMAM dendrimers. Similar molecular weight was used for both polymers of 4000 Da. For both polymers, the result demonstrated that the concentration of drug rose at 2.00 x 10-4 M and plateaued at a polymer concentration of 6.00 x 10-4 M. It was suggested the above trend was due to the aggregation of polymer. The above studies make a valuable contribution to the development of good drug delivery systems.EThOS - Electronic Theses Online ServiceGBUnited Kingdo