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Fabrication, morphology, and dynamic mechanical properties of a model composite system containing in situ-grown filler

1972; Taylor & Francis; Volume: 6; Issue: 2 Linguagem: Inglês

10.1080/00222347208212886

1525-609X

J. L. Kardos, W. L. Mcdonnell, J. Raisoni,

Synthesis and properties of polymers

Abstract The technique of in situ crystallization was utilized to fabricate a model composite system in which the filler morphology is variable under constant interface conditions. A butadiene-acrylonitrile copolymer was chosen as the matrix from which acetanilide was crystallized in two distinctly different crystal morphologies for filler volume loadings up to 0.35. At the same volume fraction filler, the shape of the relative modulus-filler loading curve is sensitive to the filler crystallization temperature and, thus, to the filler size and shape. For a given crystallization temperature (25°C), the data in the low-volume loading region (>0.2) can be represented reasonably well with the Mooney equation which indirectly yields a filler aspect ratio in agreement with scanning electron micrographs. When the observed morphological parameters are utilized for the entire filler loading range, the 25°C data are best predicted by the Halpin-Tsai equation in conjunction with lamination theory. In general, filler interlocking at high filler volume loadings (∼0.3) causes the experimental modulus to rise significantly higher than can be predicted with existing theory and the known filler morphology. The normalized damping ratio, (G″/G′)f/(G″/G′)uφ1, rises significantly above 1.0 with increased filler loading at temperatures above Tg. This rise is attributed to changes in the properties of the polymer matrix near and at the interface. The in situ-grown composite system described here also provides an interesting link between the equations used to design structural composite materials and crystalline polymers.