Elongational properties and crystallization of poly (isobutylene)melts probed by synchrotron radiation

EN ESTE TRABAJO SE DESCRIBE LA TRANSICION DE FASES DE POLIISOBUTILENO DE VARIOS PESOS MOLECULARES SOMETIDOS A ESFUERZOS ELONGACIONALES. EXPERIMENTOS DE REOMETRIA Y DIFRACCION DE RAYOS X DE ANGULO AMPLIO SE REALIZAN SIMULTANEAMENTE PARA CORRELACIONAR LAS PROPIEDADES MECANICAS Y LA ESTRUCTURA DEL MATERIAL. MUESTRAS DE POLIMERO DE BAJO PESO MOLECULAR NO CRISTALIZAN EN EL INTERVALO DE VELOCIDADES DE DEFORMACION APLICADAS. AL INCREMENTAR EL PESO MOLECULAR DEL POLIMERO LA CRISTALIZACION OBTENIDA ES PRECEDIDA POR UN ENDURECIMIENTO DEL MATERIAL DEBIDO A LA DEFORMACION. Abstract IN THIS PAPER, WE DESCRIBE A PHASE TRANSITION IN POLY(ISOBUTYLENE) OF VARIOUS MOLECULAR WEIGHT UNDER ELONGATIONAL STRESS. RHEOMETRY AND WIDE ANGLE X-RAY DIFFRACTION HAVE BEEN PERFORMED SIMULTANEOUSLY TO CORRELATE MECHANICAL AND STRUCTURAL PROPERTIES OF THE MATERIAL. THE LOW MOLECULAR WEIGHT SAMPLES DID NOT CRYSTALLIZE UNDER THE FLOW IN THE RANGE OF THE STRAIN RATES APPLIED. ON THE OTHER HAND, AS THE MOLECULAR WEIGHT INCREASES THE CRYSTALLIZATION IS ALWAYS PRECEDED BY A STRAIN OF THE SAMPLES UNDER STRETCHING.