Morphological, mechanical and thermal properties of Amorphous Copolyester/ Polyoxymethylene blends

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dc.contributor.authorKok Loon, Lam
dc.date.accessioned2014-11-14T07:49:40Z
dc.date.available2014-11-14T07:49:40Z
dc.date.issued2005
dc.descriptionMasteren_US
dc.description.abstractThe research on amorphous copolyester/polyoxymethylene (POM) blends consists of two parts. The first part was to study the effects of blend composition on the morphological, mechanical and thermal properties of amorphous copolyester/POM blends. Poly(ethylene glycol-co-cyclohexane-1, 4-dimethanol terephthalate) (PETG) was selected as copolyester. PETG/POM blends were produced by melt blending covering the whole composition range. The specimens of the blends were prepared using injection and compression molding. Properties such as melt flow index (MFI), density, tensile and flexural stiffness of these incompatible PETG/POM blends followed the additivity rule as a function of composition. However, the elongation at break, energy absorbed until tensile failure, flexural strength, notched Izod impact strength and static fracture toughness, Kc showed lower values than either of the neat blend components. This was traced to the poor interfacial adhesion between PETG and POM. The degree of crystallinity of the PETG/POM blends decreased with increasing the PETG concentration. This was attributed to the amorphous nature of PETG. A cocontinuous morphology was ascertained by the combination of selective extraction and SEM for the blends PETG/POM 60/40 and 50/50 wt%/wt%. The tensile fracture surface of the 50/50 blend exhibited a fibrillar morphology owing to the injection moldinginduced distortion of the initial co-continuous phase structure. The elongation at break, energy to tensile failure, notched Izod impact strength and fracture toughness of the co-continuous PETG/POM blends were slightly higher than those blends with dispersed phase structure. However, the values were still below the corresponding values of the neat PETG and POM. The second part of the research involves the usage of thermoplastic polyurethane (TPU) as a compatibilizer in PETG/POM blends. Two types of TPU (i.e. polyester based and polyether based) were used to compatibilize the blends system. The co-continuous PETG/POM (50/50 wt%/wt%) blends were prepared. The mechanical properties of the co-continuous PETG/POM blends were studies through flexural and single-edge notch tensile test (SEN-T). The flexural strength of the PETG/POM blends was decreased in the presence of TPU. This was attributed to the elastomeric nature of the TPU. The compatibilizing effects of TPU on the PETG/POM blends were proven by moderate improvement in the fracture toughness and confirmed by the SEM observation. The SEN-T fractured surface of the compatibilized blends showed gross matrix shear yielding as compared to the uncompatibilized system. The Kc values of the PETG/POM blends decreased with the increasing of testing speed. The optimum toughening effect was observed in PETG/POM blends compatibilized with polyether based TPU at testing speed of 100mm/min. The polyether based TPU is a more efficient compatibilizer as the amount required being 1/2 to that of the polyester based counterpart to achieve the same Kc value. This was attributed to the elastomeric nature of the polyether based TPU. The softer nature of polyether based TPU could provide better toughening effect than the polyester based TPU, which is relatively harder in nature.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/491
dc.language.isoenen_US
dc.subjectMaterials and Mineral Resources Engineeringen_US
dc.subjectAmorphous Copolyesteren_US
dc.titleMorphological, mechanical and thermal properties of Amorphous Copolyester/ Polyoxymethylene blendsen_US
dc.typeThesisen_US
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