Investigation of the transcrystalline interphase in fiber-reinforced polypropylene composites
- Princeton Univ., NJ (United States)
- DuPont Central R&D, Wilmington, DE (United States)
A unique crystalline morphology which develops in certain fiber reinforced thermoplastics has been the focus of numerous investigations in recent years. This unique morphology, termed {open_quotes}transcrystallinity{close_quotes}, occurs as a result of dense nucleation of polymer crystals along the surface of reinforcing fibers. As these fiber-sponsored nuclei grow, they impinge upon one another which forces growth to occur in an anisotropic columnar manner away from the fiber, outward into the thermoplastic matrix. Several mechanisms have been proposed to describe why this dense nucleation occurs at the fiber surface, including epitaxial matches between the fiber and polymer matrix unit cells, thermal conductivity mismatches between fiber and matrix, and shear induced nucleation. Most likely any of these mechanisms would produce a crystalline polymer morphology around the reinforcing fiber which would resemble {open_quotes}transcrystallinity{close_quotes} on the micron scale. To date much of the work conducted at TRI/Princeton regarding this phenomenon has concerned the effect of reinforcing fibers on the isothermal crystallization kinetics of various systems. Other groups have attempted to elucidate the role of the transcrystalline layer (TCL) on the mechanical properties of composites. Much of this work has dealt with model single fiber composites. Relatively little research, however, has been conducted on the molecular and lamellar arrangement of the polymeric material within the TCL. Our current work, therefore, focuses on discerning the nature of the molecular orientation of the TCL in millimeter-thick composites containing realistic fiber loadings, with the goal of relating this structural information to mechanical properties.
- OSTI ID:
- 602860
- Report Number(s):
- CONF-961108--
- Country of Publication:
- United States
- Language:
- English
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