Fiber reinforced polypropilene: influence of iPP molecular mass on morphology, crystallization, thermal and mechanical properties

International audienceThe influence of molecular weight and its distribution on the nucleation density, crystallization, thermal and mechanical behavior of isotactic polypropylene based composites has been investigated. The composites were prepared by compression molding. The ability of carbon and Kevlar fibers to nucleate the polypropylene has been studied during isothermal and nonisothermal crystallization, by optical microscopy and differential scanning calorimetry (DSC), as function of crystallization temperature Tc and iPP molecular weight. Two extreme crystallization conditions were tested: quenching and slow crystallization to obtain crystals and amorphous phases of different structure. The ability of fibers to enhance mechanical properties in polypropylene based composites was examined by tensile tests at room temperature. It was found that nucleation density, crystallization parameters, and the results of tensile tests strongly depend on the molecular weight Mw of iPP, molecular weight distribution, and thermal history of polypropylene. The numerical values of the nucleation density have been found to strongly depend on the nature of fiber. In fact, Kevlar fiber has shown a better nucleating ability than carbon fiber. The results of tensile tests have been related to the sample morphology. The analysis of fractured specimens also provided useful information about fiber‐matrix adhesio

Broom fibres as reinforcements for thermoplastic matrices

International audienceVegetable fibers deriving from the basts of broom plants have been used as reinforcement for two polypropylenic matrices: a conventional isotactic polypropylene (iPP) and a maleate modified one (iPPMA). Before mixing the fibers were subjected to two different extraction procedures: a conventional alkaline treatment and an innovative steam explosion process. Afterwards, the composites obtained by compression moulding were thermally, morphologically, and mechanically characterized. Moreover, water absorption tests, to examine the behaviour of these materials in wet conditions, were also performed

Influence of molecular mass and molecular mass distribution on crystallization and thermal behaivour of isotactic polypropilene

International audienc

Usaturated polyester resins: a study on mechanism and kinetics of the curing process by FTiR spectroscopy

International audienc

Research and training programme for third Mediterranean countries

Collaboration with International Cooperation DivisionConsiglio Nazionale delle Ricerche (CNR). Biblioteca Centrale / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Steam exploded wheat straw fibers as reiforcing for polypropylene based composites. Characterization and properties.

International audienceAus Weizenstrohfasern und Polypropylen (iPP) bzw. mit maleinsäureanhydrid modifiziertem Polypropylen (iPPMA) wurden Composite hergestellt. Die Weizenstrohfasern wurden vor dem Einmischen in die Polypropylenmatrix einem Dampfexplosionsprozeß unterworfen, der bei Lignocellulosematerialien morphologische und strukturelle Veränderungen bewirkt, die zu einer Verbesserung der Wechselwirkungen mit der thermoplastischen Matrix führen können. Die modifizierte iPPMA-Matrix weist im Vergleich zur iPP-Matrix bessere mechanische Eigenschaften (Zug- und Schlagverhalten) und eine bemerkenswerte Verringerung der Wasseraufnahme, einer der Hauptnachteile von Compositen mit Naturfasern, auf. Die gute Grenzflächenhaftung in den iPPMA-Compositen kann mit den beim Mischen der Fasern mit der Polymerschmelze gebildeten kovalenten Esterbindungen zwischen den Maleinsäureanhydrid-Segmenten und den dampfbehandelten Fasern erklärt werdenComposites of wheat straw fibers with polypropylene (iPP) and maleic anhydride modified polypropylene (iPPMA) were prepared.Before being mixed with polypropylene matrices, the wheat straw fibers were subjected to a steam explosion process that induces morphological and structural changes in lignocellulosic materials. Such changes are able to enhance the interactions with the thermoplastic matrix.Compared with iPP, the modified matrix (iPPMA) has shown higher mechanical performances (tensile and impact behavior) and a remarkable decrease of water absorption, that is one of the main drawbacks of natural fiber composites.Finally, the presence of covalent bonds between maleic anhydride and steam-exploded (STEX) fibers, by means of an esterification reaction, produced during the melt-mixing process, can explain the resulting good interfacial adhesion found in iPPMA-based composites