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Determinación de los cambios de microestructura iniciales y a largo plazo en el polietileno de peso molecular
Chuping Luo1, Teresa D Z Atvars, Pavla Meakin
1Department of Chemistry, Georgetown University, Washington, D.C. 20057-1227, USA.
Journal of the American Chemical Society
|September 25, 2003
Resumen
Un nuevo modelo explica cómo se deforma el polietileno de peso molecular ultraalto cristalizado en gel (UHMWPE). Los movimientos de las microfibras disminuyen la cristalinidad y aumentan el volumen libre a bajas relaciones de tracción, lo que afecta las propiedades del material.
Área de la Ciencia:
- La ciencia de los polímeros es la ciencia de los polímeros.
- Ciencia de los materiales Ciencia de los materiales.
- Química Física es la química física.
Sus antecedentes:
- El polietileno de peso molecular ultraalto (UHMWPE) es crucial en la investigación de materiales.
- Comprender los mecanismos de deformación en UHMWPE es esencial para optimizar sus propiedades.
- Las películas de UHMWPE cristalizadas en gel exhiben características únicas influenciadas por el procesamiento.
Objetivo del estudio:
- Para investigar los procesos de deformación en las películas de UHMWPE cristalizadas en gel hasta altas relaciones de tracción (DR).
- Para correlacionar las propiedades estructurales y dinámicas utilizando diversas técnicas espectroscópicas y térmicas.
- Proponer un nuevo modelo para la deformación de UHMWPE basado en pruebas experimentales.
Principales métodos:
- Se usó difracción de rayos X (XRD), calorimetría de barrido diferencial (DSC) y espectroscopia de aniquilación de positrones (PALS).
- El dopaje de pireno y la espectroscopia de fluorescencia sondearon la dinámica molecular.
- Se midió la difusión de N,N-dimetilanilina (DMA) en películas dopadas.
Principales resultados:
- Se propuso un nuevo modelo de deformación que involucra movimientos microfibrilares de "estiramiento" y " volteo".
- Las bajas tasas de extracción condujeron a una disminución de la cristalinidad y un aumento del volumen libre medio.
- Las altas relaciones de tracción resultaron en un aumento de la cristalinidad, cadenas más rígidas y procesos de relajación alterados.
Conclusiones:
- El modelo propuesto explica con éxito los cambios observados en la cristalinidad y el volumen libre.
- La deformación influye significativamente en el comportamiento de relajación y la movilidad molecular en UHMWPE.
- Este estudio proporciona una comprensión completa de la morfología y los mecanismos de deformación de UHMWPE.
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