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Nuevos conceptos en los elastómeros termoplásticos: el caso del polipropileno sindiotáctico, un elastómero no
Finizia Auriemma1, Claudio De Rosa
1Dipartimento di Chimica, Università di Napoli Federico II, Complesso Monte Sant'Angelo, via Cintia, 80126 Napoli, Italy. auriemma@chemistry.unina.it
Journal of the American Chemical Society
|October 23, 2003
Resumen
El polipropileno sindiotáctico (sPP) exhibe una elasticidad única debido a una transición de fase cristal-cristal reversible. Esta transformación martensítica, observada durante el estiramiento y la relajación, explica el comportamiento elástico poco convencional del material.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- Física de los polímeros Física de los polímeros
- La cristalografía es una técnica de cristalografía.
Sus antecedentes:
- El polipropileno sindiotáctico (sPP) muestra notables propiedades elásticas a pesar de su alta cristalinidad.
- Esta inusual elasticidad está vinculada a una transición reversible de fase cristal-cristal.
- Comprender esta transición es clave para explicar el comportamiento de sPP como un elastómero no convencional.
Objetivo del estudio:
- Investigar el mecanismo y la escala de tiempo de la transición de la fase cristal-cristal en sPP durante la deformación cíclica.
- Para aclarar el origen de la elasticidad en el polipropileno sindiotáctico.
- Para determinar si la transición de fase es responsable de las propiedades elastoméricas de sPP.
Principales métodos:
- Mediciones de difracción de rayos X de ángulo ancho con resolución de tiempo (WAXD).
- Utilizó la radiación sincrotrón de alto flujo en la línea de luz de la Instalación Europea de Radiación Sincrotrón (ESRF) ID11.
- Experimentos cíclicos de estiramiento y relajación en las fibras de sPP.
Principales resultados:
- La transformación estructural durante la deformación fue analizada in situ.
- La transición de fase inducida por el estrés fue identificada como una transformación martensítica.
- Se observó que la transición ocurría fácil y directamente.
Conclusiones:
- La elasticidad del polipropileno sindiotáctico es en parte de origen entálpico.
- La transformación martensítica observada proporciona un mecanismo para la elasticidad reversible de sPP.
- Este estudio aclara el comportamiento fundamental de sPP como un material elastomérico avanzado.
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