Evolution of properties of a thermosetting isocyanate/epoxy/glass fiber model composite system with increasing cure

Autor: John K. Gillham, M. T. DeMeuse, F. Parodi
Rok vydání: 1997
Předmět:
Zdroj: Journal of Applied Polymer Science. 64:27-38
ISSN: 1097-4628
0021-8995
DOI: 10.1002/(sici)1097-4628(19970404)64:1<27::aid-app3>3.0.co;2-t
Popis: A methodology is reported for monitoring the evolution of isothermal physical properties of thermosetting systems with increasing conversion (cure). For this report, measurements of modulus vs. temperature of a single composite specimen were obtained on repetitive cooling and subsequent heating to successively higher temperatures : Cooling and subsequent heating data often displayed thermohysteresis. Crossplotting provided plots of isothermal modulus vs. conversion ( as measured in the same experiment by T g ) for a wide range of temperatures (i.e., from -180 to +380°C) from both the cooling and the heating data. Comparison of isothermal cooling and heating data provided a measure of toughness of the matrix vs. conversion through the extent of hysteresis of the data. The basis of the approach depended on five factors: (a) use of composite specimen, (b) the ability to obtain data both on cooling and on heating, (c)the effect of microcracking ( which is presumably responsible for the observed hysteresis) could be removed by heating (healing) near the glass transition temperature, (d) the use of a single specimen provided an internal reference for comparing data, and (e) the assumption that T g is a direct measure of conversion. The methodology is demonstrated using a complex thermosetting isocyanate/epoxy/glass fiber composite system using the TBA torsion pendulum technique.
Databáze: OpenAIRE
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