Transcrystallinity in natural fillers-polypropylene composites

A. J. NUÑEZ; B. A. ACHA; M.M. REBOREDO; M.I. ARANGUREN; N. E. MARCOVICH

Quantitative level of chemical reactions

Nova Science Publishers Inc.

Lugar: New York; Año: 2004; p. 217 - 232

Different methods were employed to modify the compatibility of wood flour and jute fibers with polypropylene. These modifications led to different surface topologies and chemistry of the fibers and to different degrees of interfacial adhesion between the filler and the matrix. The effect of these compatibilization techniques on the crystallization behavior of polypropylene and the formation of a transcrystalline layer were analyzed. Optical microscopy indicated that untreated fibers (both, wood flour and jute), maleic anhydride (MAN) treated wood flour and washed jute fibers acted as heterogeneous nucleating agents for PP and led to the formation of a transcrystalline layer. On the other hand, samples prepared with alkenyl succinic anhydride treated jute, or with untreated wood flour and a coupling agent (a maleated polypropylene) did not show these phenomena. The presence of rather long chains attached to the lignocelullosic surfaces inhibited the heterogeneous nucleation. Only treated wood flour induced PP crystallization in β-phase in the composites. X-ray diffractometry suggested that the crystallization in β-phase was a shear-induced phenomenon favored by the chemical modification of the wood flour surface.