Micrometer injection moulding is a type of moulding in which moulds have geometrical design features on a micrometer scale that must be transferred to the geometry of the produced part. The difficulties encountered due to very high shear and rapid heat transfer of these systems has motivated this investigation into the fundamental mathematics behind polymer heat transfer and associated processes. The aim is to derive models for polymer dynamics, especially heat dynamics, that are considerably less approximate than the ones used at present, and to translate this into simulation and optimisation algorithms and strategies, Thereby allowing for greater control of the various polymer processing methods at micrometer scales.

Les contributions de cette thèse de doctorat sont focalisées sur les développements de formulations à base de polymères bio sourcés et déliantable à l’eau basés sur l’emploi d’acétate butyrate de cellulose (CAB) et de polyéthylène glycol (PEG). Ces nouvelles formulations ont été appliquées sur différentes nuances de poudres métalliques (invar) et céramiques (zircones). Ces matériaux possèdent une bonne stabilité dimensionnelle sous une large gamme de température imposée et possèdent de très bas coefficients d’expansion thermique.L’objective est l’étude et la compréhension du comportement des liants à base de CAB et PEG quand ils sont utilisés dans les variantes du procédé MIP (étapes de moulage avec ou sans pression, conditions particulières liées à la micro-injection, …) réalisées avec différentes nuances de poudres et différentes granulométries.Les caractéristiques intrinsèques de chaque CAB, leurs interactions avec le PEG et les poudres, l’influence de la nuance de poudre employée, ainsi que la granulométrie et la morphologie des poudres employées ont été étudiées et analysées en fonction du comportement final de la formulation développé et des taux de charges obtenues.L’homogénéité des mélanges développés, leurs taux de charge critique et maximal, ainsi que leurs comportements mécaniques, thermiques et rhéologiques ont été analysés et investigués par différentes études mécaniques, thermo et physico-chimiques. De nouvelles analyses chimiques et physiques ont été introduites par accroitre les connaissances sur les formulations développées. Les formulations optimales ont été validées pour différentes applications et avec l’emploi de différentes variantes du procédé MIP conduisant à l’élaboration de composants et de micro-composants PIM obtenus sans défauts et possédant d’excellentes propriétés fonctionnelles. L’étape de déliantage ainsi que l’étape de densification ont été optimisées en termes de cinétique et d’atmosphère aboutissant aux propriétés physiques et mécaniques escomptées pour l’ensemble des nuances de poudres considérées dans cette étude.En conclusion, les formulations développés des liants basées sur l’emploie de CAB et PEG sont exploitable au niveau de la recherche et au niveau industriel dans le procédé MIP. Elles apportent des améliorations par rapport aux liants conventionnels grâce à un procédé plus écologique. Cette première contribution représente une avancée significative dans l’émergence d’un procédé MIP plus écologique mais d’autres travaux futurs sont encore possibles. / This PhD Thesis studied the use of binders based on cellulose acetate butyrate (CAB) andpoly(ethylene glycol) (PEG) in different type of materials, including a ceramic, the zirconiumsilicate, and a metallic alloy, the Invar 36. These materials share their low dimensionalstability with temperature with low coefficients of thermal expansion.The scope of this work is the study and comprehension of the behaviour of the mentionedbinder systems when they are employed in different PIM processes and under differentconditions and powder-types. With regard to this matter, different formulations were designedwith several types of PEG and CAB. These formulations were compared with commercialones. The intrinsic characteristics of each CAB were linked with the behaviour of the differentfeedstock also containing PEG and powder particles. The mixtures homogeneity, the optimumand critical solid loading and its flowability were assessed by torque and capillary rheology.Other complementary techniques such as electronic and light microscopy or the measurementof the mixtures densities by pycnometry were carried out to contrast rheology results. Thecompatibility between the feedstocks’ components and their thermal behaviour were analysedby calorimetry and thermogravimetry techniques. These methods were employed by the firsttime to determine the optimal solid loading.The optimal compositions were injected by using low or high pressures or by a micro injectionmoulding process. The debinding and sintering stages were optimised using severalatmospheres. Finally, the physical and mechanical properties of the final consolidated partswere measured.It could be concluded that the studied binder systems based on PEG and CAB presentedsuitable characteristics for PIM, providing improvements with respect to conventional bindersystems and by a more environmental friendly processing. However, that doctoral work wasjust a first approach to the use of these types of binder systems in PIM. Along this workseveral issues were detected and some topics regarding the processing should be furtherinvestigated to obtain the best of these binder systems.

The feasibility of the injection moulding (IM) was explored for the development of novel drug delivery systems. Controlled release formulations were developed using a substituted cellulose derivative, hydroxypropyl methyl cellulose acetate succinate (HPMCAS) and a graft co-polymer (Soluplus®). BCS class II drugs ibuprofen and the felodipine were selected based on their physicochemical properties. In the present work, a homogenous dispersion of drugs in the polymer matrices was achieved using Hot Melt Extrusion (HME) and extruded pellets obtained were used for the development of the injection moulded systems. Four systems were developed using the IM consisting of ibuprofen-HPMCAS, ibuprofen-Soluplus®, felodipine-PEO-HPMCAS and felodipine-Soluplus®. The ibuprofen acts as a good plasticiser compared to felodipine therefore, felodipine containing IM systems required a plasticiser (PEO) when processed with HPMCAS. The analysis of extruded pellets and injection moulded systems using modulated DSC (MDSC) and Raman spectroscopy confirmed the formation of an amorphous molecular dispersion (i.e solid solution) in the case of all four systems. The phase separation behaviour and the amorphous stability of the systems was studied at various stress conditions. This revealed the “surface crystallisation” behaviour of the ibuprofen-HPMCAS systems. Temperature-composition phase diagram constructed based on the melting point depression and the Flory-Huggins lattice solution theory provided the explanation for the phase separation and crystallisation behaviour of ibuprofen-HPMCAS systems. The advanced characterisation techniques like DMA, 2D XRD and 3D laser microscopy provided the detailed understanding of crystal habits, phase seperation and surface crystallisation. The significant effect of the stress conditions on the rate of shrinkage was observed where, higher shrinkage tendency of a HPMCAS IM system was observed compared to Soluplus® IM systems. The extruded pellets provided the faster drug release compared to the moulded tablets suggests the effect of particle size as well as the densification during IM on the dissolution rate of the dosage form. The nature of the polymer and processing history were the contributing factors for the dissolution of the dosage forms.

The thermal control of a die is crucial for the development of high efficiency injection moulds. For successful thermal management, this research provides an effective control strategy to find sensor locations, identify thermal dynamic models, and design controllers. By applying a clustering method and sensitivity analysis, sensor locations are identified. The neural network and finite element analysis techniques enable the modeling to deal with various cycle-times for the moulding process and uncertain dynamics of a die. A combination of off-line training through finite element analysis and training using on-line learning algorithms and experimental data is used for the system identification. Based on the system identification which is experimentally validated using a real system, controllers are designed using fuzzy-logic and self-adaptive PID methods with backpropagation (BP) and radial basis function (RBF) neural networks to tune control parameters. Direct adaptive inverse control and additive feedforward control by adding direct adaptive inverse control to self-adaptive PID controllers are also provided. Through a comparative study, each controller’s performance is verified in terms of response time and tracking accuracy under different moulding processes with multiple cycle-times. Additionally, the improved cooling effectiveness of the conformal cooling channel designed in this study is presented by comparing with a conventional straight channel.

The thermal control of a die is crucial for the development of high efficiency injection moulds. For successful thermal management, this research provides an effective control strategy to find sensor locations, identify thermal dynamic models, and design controllers. By applying a clustering method and sensitivity analysis, sensor locations are identified. The neural network and finite element analysis techniques enable the modeling to deal with various cycle-times for the moulding process and uncertain dynamics of a die. A combination of off-line training through finite element analysis and training using on-line learning algorithms and experimental data is used for the system identification. Based on the system identification which is experimentally validated using a real system, controllers are designed using fuzzy-logic and self-adaptive PID methods with backpropagation (BP) and radial basis function (RBF) neural networks to tune control parameters. Direct adaptive inverse control and additive feedforward control by adding direct adaptive inverse control to self-adaptive PID controllers are also provided. Through a comparative study, each controller’s performance is verified in terms of response time and tracking accuracy under different moulding processes with multiple cycle-times. Additionally, the improved cooling effectiveness of the conformal cooling channel designed in this study is presented by comparing with a conventional straight channel.

The use of ultrafast lasers in material surface engineering has gained pre-eminence in recent years. This is due to optimal utility arising from their versatility, better process control, repeatability and high precision fabrication, without need for post processing. Reported in this thesis are experimental results on the use of picosecond laser to produce micro-patterns on cyclone components and their effects on flow characteristics. Results show that micro- dimples achieved reduction in dust accumulation within a multi-cyclone system considered, up to 78%. These micro-dimples when applied on the cyclone roof effected a 3% reduction in inlet velocity and 5% reduction on the dynamic pressure across the cyclone, without dust introduction. Results support the possibility for energy savings, without compromise on cyclone overall separation efficiency. Findings further demonstrated the effects of micro-riblets on cyclonic airflow at the wall boundary. Research outcomes supported the view that surface roughness of the cyclone roof could contribute on its dust separation capacity. Injection moulding was used to produce bumps on ABS plastic materials utilising picosecond laser machined micro-dimples on H13 tool steel. A statistical model detailing the interactions between the critical factors involved with picosecond laser interaction with H13 for micro-patterning was proposed. Critical factors identified were laser fluence, scanning speed and number of laser scans. In addition, results demonstrated the suitability of predicting depth of 40 - 100 µm for H13 tool steel, with 96% accuracy. The findings in this research could be explored to develop embedded micro/nano-wires within riblets through injection moulding, to effect electrically biased charging within the internal walls of a cyclone to aid dust separation processes.

End-gated and centre gated mouldings have been assessed with varying thickness and sprue geometries for the centre gate. Alternative image analysis techniques are used to measure the orientation and length of injection moulded short and long fibres composite components. The fibre orientation distribution (FOD) measurements for both geometries have been taken along the flow path. In shear flow the FOD changes along the flow path, however the FOD remains relatively constant during expansion flow. The core width and FOD at the skin within a long glass fibre (LGF) specimen is different in comparison to a short glass fibre (SGF) specimen. Fibre length measurements have been taken from the extrudate, sprue and 2 positions within the centre gate cavity. The size of the sprue has little influence on fibre breakage if the moulding is more than 1 mm thick The SGF FOD prediction models within Autodesk Simulation Moldflow Insight 2014 (ASMI) have been validated against measured SGF data. At present, by default, the models over-predict the < cos2θ > for most geometries. When the coefficients are tailored for each model, drastic improvements are seen in the FOD prediction. The recently developed SGF RSC model accurately predicts the FOD in shear, in a thin geometry, whereas the Folgar-Tucker model predicts the FOD accurately in expansion flow. The measured LGF fibre length distribution (FLD) and FOD have been validated against the LGF prediction models. The LGF models are currently under predicting the breakage and over-predicting < cos2θ >. The breakage prediction improves if measured FLD of the extrudate is input into the model.

The emergence of microneedle (MN) technologies offers a route for a pain free, straightforward and efficient way of transdermal drug delivery, but technological barriers still exist which pose significant challenges for manufacture of MN systems with high volume outputs at low cost. The main aim of this research was to develop new ways for MN manufacture primarily using micro-injection moulding processes with high performance engineering thermoplastics. During the moulding process these polymeric melts will be subjected to extreme stress and temperature gradients and detailed material characterisation combined with in-line monitoring is desirable to optimise the moulding parameters and will help in achieving sharp microneedles with acceptable quality. Hence high shear rheology of these selected materials was performed at wall shear rates carried out in excess of 107 s-1 over a range of temperatures to predict the flow behaviour of polymer melts at such high shear strain rates. This information was fed into injection moulding simulation software tools (Moldflow) to assist the MN production process design. The optimal design was then used to produce a full 3D solid model of the injection mould and mould insert. Furthermore various design of experiments were conducted considering input parameters such as injection pressure, injection speed, melt temperature, filling time and mould cavity temperature. Response variables including product quality and data acquired from the cavity pressure and temperature transducers were used to optimise the manufacturing process. The moulded MNs were geometrically assessed using a range of characterisation techniques such as atomic force microscopy, confocal microscopy and scanning electron microscopy. An attempt to make hollow MNs was performed and encountered many challenges like partial cavity filling and part ejection during processing. Studies were carried out to understand the problem and identified the major problem was in tool design and improvements to the moulding tool design were recommended. Plasma treatment and mechanical abrasion were employed to increase the surface energy of the moulded polymer surfaces with the aim of enhancing protein adsorption. Sample surface structures before and after treatment were studied using AFM and surface energies have been obtained using contact angle measurement and calculated using Owens-Wendt theory. Adsorption performance of bovine serum albumin and release kinetics for each sample set was assessed using a Franz diffusion cell. Results indicate that plasma treatment significantly increases the surface energy and roughness resulting in better adsorption and release of BSA. To assist design-optimisation and to assess performance, a greater understanding of MN penetration behaviour is required. Contact stiffness, failure strength and creep behaviour were measured during compression tests of MN against a steel surface, and in-vitro penetration of MNs into porcine skin. The MN penetration process into porcine skin was imaged using optical coherence tomography. Finally, a finite element model of skin was established to understand the effect of tip geometry on penetration. The output of findings from this research will provide proof of concept level development and understanding of mechanisms of MN penetration and failure, facilitating design improvements for micro-injection moulded polymeric MNs.

The master’s thesis is focused on the reduction of rejection rate in production of plastic bowls with the use of statistic methods. The theoretical part of this thesis describes among others Statistical Process Control, Process capability and types regulatory diagrams. The basis for the practical part is data collection over a certain period of production, from which the percentage of the rejection rate is evaluated. Experiments and corrective actions are designed to improve the process and thereby reduce scrap.

The diploma thesis pointed out the possibility of using rapid prototyping methods in the field of plastic injection, specifically to make shaped inserts into the injection mold. The universal frame of the injection mold was used and only the shaped inserts were changed. The main part of the work was the construction of an injection mold with the subsequent practical production of shaped inserts for a specified part. In the introductory part, a theoretical search was performed, about which production methods in combination with suitable materials could be theoretically used. Furthermore, the polyjet and DLP methods were chosen, which were used to produce components (core and cavity). The result of the diploma thesis was a summary of all parameters, comparison of materials and production methods. Polypropylene and polyamide 6 materials were injected into the injection mold, from which the first prototype products were made. Instructions for the production of shaped inserts with the recommended technology and material were created for the selected type, which could be used in practice.