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Abstract. Halloysites/polypropylene nanocomposites with different nanotubes contents were prepared by diluting a masterbatch containing 30 wt.% halloysites with polypropylene (PP). Unmodified (HNTs) and quaternary ammonium salt treated (QM-HNTs) halloysite nanotubes were used. Both degree of crystallinity and crystallization temperature increase upon addition of halloysites into PP, thus indicating a potential nucleation effect induced by the nanotubes. An homogeneous distribution and dispersion of nanotubes was observed throughout the PP matrix, with a slightly better dispersion in the case of modified QM-HNTs compared to unmodified HNTs. Mechanical tests in tension, bending and notched impact demonstrated that strength and modulus of the nanocomposites significantly increase with addition of halloysites without significant loss of ductility. An halloysite content of 6 wt.% appears as an optimum. Modified halloysites (QM-HNTs) lead to globally better performances due to strong interfacial interaction between the polymer matrix and the nanotubes.

Abstract. Multi-wall carbon nanotubes (MWNTs) filled polypropylene (PP) nanocomposites were prepared through diluting a PP/MWNT masterbatch in a PP matrix by melt compounding with a twin screw extruder. Polypropylene grafted maleic anhydride (PP-g-MA) was used to promote the carbon nanotubes dispersion. The effect of PP-g-MA addition on the rheological, mechanical and morphological properties of the nanocomposites was assessed for different MWNTs loadings. Scanning electron microscopy (SEM) has shown that nanotubes are distributed reasonably uniformly. A better dispersion and good adhesion between the nanotubes and the PP matrix is caused by wrapping of PP-g-MA on MWNTs. When PP-g-MA is added, dynamic moduli and viscosity further increases compared to PP/MWNT nanocomposites. The rheological percolation threshold drops significantly. Tensile and flexural moduli and Charpy impact resistance of the nanocomposites also increases by the addition of PP-g-MA. The present study confirms that PP-g-MA is efficient to promote the dispersion of MWNTs in PP matrix and serves as an adhesive to increase their interfacial strength, hence greatly improving the rheological percolation threshold and mechanical properties of PP/MWNT nanocomposites.

This paper aims to identify the main parameters that improve the flexural properties of long glass fiber/polyamide 66 injection moulded parts. The mould geometry has been chosen so as to reproduce some geometrical accidents (e.g. sharp frontal and tangential steps) occurring on industrial moulds. A Taguchi design of experiments (DOE) has been used in order to quantify the effects of processing conditions on the flexural strength and modulus. Polymer melt temperature is the main parameter acting on the flexural properties, in both flow and transverse directions. The structure/process/flexural properties relationship has then been deduced from microstructure analysis (crystallinity, local residual fiber length and average orientation, interfacial quality). For optimized injection moulding conditions, leading to the highest flexural strength Correspondence

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The crystallization behavior and the crystalline structure of nylon6-clay nanocomposites are investigated with regard to the processing conditions and thermal treatment. Microextruded bulk samples as well as blown films are under concern. The often reported nucleating effect of the clay particles is shown to strongly depend on the processing parameters prior to the solidification step, namely, the shear intensity which promotes self-nucleation and the temperature of the melt which regulates the density of these unstable nuclei. The MMT content influences the crystallization kinetics and the crystalline structure via the shear amplification phenomenon which increases the densities of both the shear-induced and the MMT-induced nuclei. The MMT platelets also turned out to hinder the crystal growth. The cooling rate plays a major role on the final crystalline structure by shifting the crystallization temperature in the specific growth range of either the Ror the γ-crystal forms of the nylon6 matrix. Blown films corroborate the findings from microextruded samples regarding the competition between nucleation and growth in the resulting crystalline form of the nylon6 matrix. Besides, the strong texturing of the nanocomposite films provides information on the local arrangement of the chains and crystal unit cell on the MMT platelets.