MECHANICAL PROPERTIES IMPROVEMENT OF CONTINUOUS PP/GF COMPOSITES BY IN-SITU POLYMERIZATION REACTION

MARIANA ETCHEVERRY; MARÍA LUJÁN FERREIRA; NUMA CAPIATI; SILVIA BARBOSA

San Sebastián, España

Congreso; V International Conference on Science and Technology of Composite Materials 8° Congreso Nacional de Materiales Compuestos; 2009

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 glass fibers (GF) can be highly improved by chemical anchoring between PP and GF. Another problem, that limits the use of thermoplastics in high performance composites, is its high viscosity that impedes the polymer penetration in mats of fibers. In this sense, direct polymerization enhances the penetration because the polymer is formed in-situ. In this work, a methodology for direct polymerization of PP onto GF is proposed. The reaction route includes 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. As a result of this reaction, PP chains grow by copolymerization of propylene with the olefin anchored to the GF surface. This procedure was carried out either on continuous strand or on woven mat. With these fibers, continuous PP/GF composite samples were prepared and tensile mechanical properties measured. Results show that modulus was increased and it is a function of the “copolymerization reaction parameters”. The PP/GF adhesion, as well as, the PP penetration in the woven mat was characterized by Scanning Electron Microscopy (SEM) with X-ray Disperse Energy Microanalysis on line (SEM/EDX) on cryogenic fracture surfaces. The results were interpreted in terms of theoretical mechanical models.