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Industrial processing of polymers can involve complex conditions and materials. Therefore, prediction and control of the properties are not always well understood. It sometimes happens that unwanted phenomena occur in the final product. In order to minimize as much as possible such problems, investigation of the conditions leading to various morphologies is required. In this thesis, the focus is on the delamination phenomenon which causes a peeling of injected pieces. Here, we seek to understand what kind of morphology is responsible for delamination in injected pieces. Various techniques such as X-ray and light scattering, optical and electron microscopy, rheology and calorimetry have been used to investigate the different length scales of matter organization. The material under consideration is a polyamide/polytetramethylene-glycol copolymer with a high content of polyamide. The first approach consists in studying the morphologies of that material as a function of temperature and shear. Two kinds of organized states were observed. The first one results from the natural tendency of the different segments to segregate leading to a microphase separation in the molten state. A microphase separation in the molten state is observed. However, the time required for such an organization to appear is so large that this morphology is very unlikely to be involved in the delamination phenomenon. On the other hand, the semi-crystalline state which originates from the fast crystallization of the polyamide segments may play a role. A comparative study of the crystallization after applying flow to the neat polyamide and to the multiblock shows that the latter is not very sensitive to the imposed shear. As a consequence, no large changes in crystalline morphology are expected during injection and hence trans-crystallinity is not likely to be a source of decohesion and hence of delamination. The second approach takes into account that the real material used during injection molding is in a fact a mixture of two chemically similar multiblocks. For practical reasons, additives such as antimony oxide (flame retardant), carbon black (enhanced electroconductivity), dyes (coloration), zinc oxide (prevents the photo-oxidation) are required to produce performance materials. In the case of the polymer investigated, the additives are introduced via the use of a soft multiblock. It was observed that the two materials are partially miscible and it was predicted that with the conditions imposed during injection, fibrils made of the dispersed phase are expected to be present in the final pieces. This was confirmed by the observation of injected pieces by means of transmission electron microscopy. Such a morphology is very likely to be responsible for the delamination since it produces a discontinuity in the piece over a large scale. A relatively simple experiment in real injection conditions is suggested to confirm the previous assumption. Finally, based on this study, suggestions are made to suppress or diminish the probability of producing delaminating pieces. The second approach takes into account that the real material used during injection molding is in a fact a mixture of two chemically similar multiblocks. For practical reasons, additives such as antimony oxide (flame retardant), carbon black (enhanced electroconductivity), dyes (coloration), zinc oxide (prevents the photo-oxidation) are required to produce performance materials. In the case of the polymer investigated, the additives are introduced via the use of a soft multiblock. It was observed that the two materials are partially miscible and it was predicted that with the conditions imposed during injection, fibrils made of the dispersed phase are expected to be present in the final pieces. This was confirmed by the observation of injected pieces by means of transmission electron microscopy. Such a morphology is very likely to be responsible for the delamination since it produces a discontinuity in the piece over a large scale. A relatively simple experiment in real injection conditions is suggested to confirm the previous assumption. Finally, based on this study, suggestions are made to suppress or diminish the probability of producing delaminating pieces.

Academic collection --- 66.095.26 --- 669 --- Polymerization --- Metallurgy --- Theses --- 669 Metallurgy --- 66.095.26 Polymerization

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Academic collection --- 66.095.26 --- 66.095.26 Polymerization --- Polymerization --- Theses

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Polymers --- Polymères --- 66.095.26 --- #KVIV --- #WSCH:MACG --- Polymerization --- 66.095.26 Polymerization --- Polymères --- VINYL POLYMERS --- SYNTHESIS

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66.095.26 --- 66.095.26 Polymerization --- Polymerization --- Polymerisation --- Polymers --- Polymers and polymerization --- Synthesis of polymers --- Chemical reactions --- Synthesis --- POLYMERIZATION

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Polymers --- Catalysis --- Ziegler-Natta catalysts --- Polyacetylenes --- Olefins --- Polymères --- Catalyse --- Catalyseurs de Ziegler-Natta --- Oléfines --- 66.095.26 --- Polymerization --- 66.095.26 Polymerization --- Alkenes. --- Polymères --- Oléfines