Development of binder systems based on CAB powder injection moulding (PIM) and micro powder injection moulding (?-PIM) of zircon and invar powders
- Autores: Javier Hidalgo García
- Directores de la Tesis: José Manuel Torralba Castelló (dir. tes.), Antonia Jiménez Morales (dir. tes.)
- Lectura: En la Universidad Carlos III de Madrid ( España ) en 2014
- Idioma: inglés
- Tribunal Calificador de la Tesis: Elena Gordo Odériz (presid.), M. Victoria Bargues Lopez (secret.), Leandro Bolzoni (voc.), Efrain Carreño Morelli (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: e-Archivo
- Resumen
Powder injection moulding (PIM), in its different versions, is a manufacturing method that in the last decades has been consolidated as an effective and competitive alternative to fabricate small size and complex geometry parts in large batches. Its future expansion to new applications and sectors requires an exhaustive research in new materials and the improvement of the manufacturing process itself. A better understanding between the variables materialprocessing- properties is still needed to improve the quality and repeatability. In the last decades, a growing environmental awareness has been observed not only by the costumers but by the own industry. Within the PIM process, there are many possibilities to reduce the energy consumption and the emission of hazardous products. One of those alternatives would consist on using binder systems formulations that do not involve organic solvents, toxic vapours during processing or that allow reducing the fabrication temperatures. The binder systems based on natural derivatives, such as the thermoplastic polysaccharides, offer an interesting alternative to the conventional use of petroleum derivatives that has been scarcely investigated. Their use would suppose a cero balance of CO?emissions during the thermal debinding. This PhD Thesis studied the use of binders based on cellulose acetate butyrate (CAB) and poly(ethylene glycol) (PEG) in different type of materials, including a ceramic, the zirconium silicate, and a metallic alloy, the Invar 36. These materials share their low dimensional stability with temperature with low coefficients of thermal expansion. The scope of this work is the study and comprehension of the behaviour of the mentioned binder systems when they are employed in different PIM processes and under different conditions and powder-types. With regard to this matter, different formulations were designed with several types of PEG and CAB. These formulations were compared with commercial ones. The intrinsic characteristics of each CAB were linked with the behaviour of the different feedstock also containing PEG and powder particles. The mixtures homogeneity, the optimum and critical solid loading and its flowability were assessed by torque and capillary rheology. Other complementary techniques such as electronic and light microscopy or the measurement of the mixtures densities by pycnometry were carried out to contrast rheology results. The compatibility between the feedstocks’ components and their thermal behaviour were analysed by calorimetry and thermogravimetry techniques. These methods were employed by the first time to determine the optimal solid loading. The optimal compositions were injected by using low or high pressures or by a micro injection moulding process. The debinding and sintering stages were optimised using several atmospheres. Finally, the physical and mechanical properties of the final consolidated parts were measured. It could be concluded that the studied binder systems based on PEG and CAB presented suitable characteristics for PIM, providing improvements with respect to conventional binder systems and by a more environmental friendly processing. However, that doctoral work was just a first approach to the use of these types of binder systems in PIM. Along this work several issues were detected and some topics regarding the processing should be further investigated to obtain the best of these binder systems. ---------------------------------------------
