Use of SEM/EDX for the Chemical Anchoring Characterization of Polypropylene onto Glass Fibers

ETCHEVERRY, MARIANA; FERREIRA, MARÍA LUJÁN; BARBOSA, SILVIA ELENA; YANEZ, MARIA JULIA

Rosario, Argentina

Congreso; 10th Inter-American Congress on Electron Microscopy (CIASEM 2009) y 1st Congress of the Argentine Society of Microscopy (SAMIC 2009),; 2009

Sociedad Argentina de Microscopía

The adhesion between matrix and fibers is an essential factor in determining the performance of thermoplastic-based polymer composite materials. The interfacial adhesion of the polypropylene (PP) and glassfibers(GF) could be highly improved by chemical anchoring between PP and GF. In this sense, metallocenic polymerization of PP from active sites on GF is proposed. The experimental route involves an initial contact with methylaluminoxane (MAO) and hydroxy-a-olefin to generate the anchorage points on the fiber surface, followed by a propylene polymerization catalyzed by EtInd2ZrCl2 (metallocene)/MAO. In order to assess the chemical bonding between PP and GF, an experimental method baed on selective extractions and a combination of scanning electron microscopy (SEM) with X-ray disperse energy microanalysis (EDX) was used. Samples were etched with n- heptane at high temperature for extracting the polymer “physically” bonded to GF. At this condition it was proved that the polymer dissolves into the solvent. Then, if polymer remains onto fibers is chemically bonded. The combination between SEM-EDX gives a very valuable tool to relate and analyze morphology and elemental chemical composition of the interphase, because it allows the characterization of the elements involve in an area directly observed by SEM. In this sense, the samples treated in this way were measured by SEM/EDX and comparing with pure GF. Different morphologies of polymers onto fibers were observed and the typical carbon peak, absent in pure GF, appears. Also Al peak grows between MAO treatments. The above analysis was corroborated by a second use of SEM directly onto cryogenic fractures of composites prepared with the “polymerized fibers”. Typical debonding is observed in samples prepared with fibers without treatment and characteristic fracture lines from fibers, indicating good adhesion, are evident in composites prepared with “polymerized fibers”.