Publicação
Development of polymeric systems for safety footwear
| Resumo: | In the recent years, the Portuguese Footwear industry seeks to affirm itself in a global competitive market, with high technical and innovative solutions able to offer high quality products. The Safety footwear market deserves special attention since the manufactured products are used to protect worker’s feet from potential hazards. The toe cap is one of the key components in safety shoes and one of the main contributors to the overall weight since most safety shoes are built with steel toe caps due to their high mechanical performance. Efforts have been made to replace these toe caps by non-metallic solutions, because they are lighter, provide better thermal and electrical insolation, and are insensitive to magnetic fields. However, most of these toe caps require higher volume concept to achieve a comparable performance to their metallic counterparts, causing aesthetic and design problems. This thesis aimed to foster new solutions based on the enhancement of polycarbonate (PC) mechanical properties and to establish a numerical methodology based on the OpenFOAM®. To this end, PC blends and PC (nano)composites were prepared by melt blending, with ABS, ABS-g-MA, SEBS-g-MA, COPE, nanoclay and natural fibers, and characterized in terms of morphology, topology, structure, tensile and impact behavior of each system. The results demonstrate that ductile to brittle transition mode is highly dependent on the polymeric system and that PC suffers extensive thermo-oxidative degradation during processing, which can be delayed by blending with the elastomeric materials. SEBS-g-MA and COPE can improve toughness, while nanoclay and natural fiber slightly increases the elastic modulus, and ABS and ABS-g-MA only show a marginal increase on both. For the numerical studies, a commercially available toe cap was characterized, and the corresponding tensile behavior was obtained to feed the numerical simulations. A toolbox developed within the OpenFOAM® for solid mechanics and fluid-solid interaction was used to simulate the EN 12568 tests (15 kN of compression force and 200 J of impact) required for safety footwear product approval, showing excellent agreement with the experimental data, with a maximum error of 6.8%. |
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| Autores principais: | Rodrigues, Pedro António Veiga |
| Assunto: | Elastomers OpenFOAM Polycarbonate Safety footwear Toe cap Biqueira Calçado de segurança Elastómeros Policarbonato |
| Ano: | 2020 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | In the recent years, the Portuguese Footwear industry seeks to affirm itself in a global competitive market, with high technical and innovative solutions able to offer high quality products. The Safety footwear market deserves special attention since the manufactured products are used to protect worker’s feet from potential hazards. The toe cap is one of the key components in safety shoes and one of the main contributors to the overall weight since most safety shoes are built with steel toe caps due to their high mechanical performance. Efforts have been made to replace these toe caps by non-metallic solutions, because they are lighter, provide better thermal and electrical insolation, and are insensitive to magnetic fields. However, most of these toe caps require higher volume concept to achieve a comparable performance to their metallic counterparts, causing aesthetic and design problems. This thesis aimed to foster new solutions based on the enhancement of polycarbonate (PC) mechanical properties and to establish a numerical methodology based on the OpenFOAM®. To this end, PC blends and PC (nano)composites were prepared by melt blending, with ABS, ABS-g-MA, SEBS-g-MA, COPE, nanoclay and natural fibers, and characterized in terms of morphology, topology, structure, tensile and impact behavior of each system. The results demonstrate that ductile to brittle transition mode is highly dependent on the polymeric system and that PC suffers extensive thermo-oxidative degradation during processing, which can be delayed by blending with the elastomeric materials. SEBS-g-MA and COPE can improve toughness, while nanoclay and natural fiber slightly increases the elastic modulus, and ABS and ABS-g-MA only show a marginal increase on both. For the numerical studies, a commercially available toe cap was characterized, and the corresponding tensile behavior was obtained to feed the numerical simulations. A toolbox developed within the OpenFOAM® for solid mechanics and fluid-solid interaction was used to simulate the EN 12568 tests (15 kN of compression force and 200 J of impact) required for safety footwear product approval, showing excellent agreement with the experimental data, with a maximum error of 6.8%. |
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