The present work describes the preparation of polypropylene composites reinforced with cotton fibers, which were obtained from textile waste. The cellulosic fibers were bleached and then chemically modified on the surface using acetylation or silanization methods. Fourier transform infrared spectroscopy analysis and energy dispersive X‐ray spectroscopy confirmed the efficiency of both treatments. Results of thermal degradation by thermogravimetric analysis (TGA) of treated fibers indicated that the acetylated ones decreased thermal stability while the silanized fibers increased this property. The influence of the chemical modifications and fibers content in polypropylene‐based composites was studied by thermomechanical and mechanical properties (dynamic mechanical analysis and tensile tests) and thermal analyses (TGA and differential scanning calorimetry). The results showed that the addition of the obtained cellulose fibers in polypropylene caused increase of storage and Young's moduli, along with stress at break. Moreover, scanning electronic microscopy micrographs of cryofractured surfaces revealed stronger adhesion between fiber and matrix in the composites reinforced with the modified fibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45060.

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Graphite is a naturally abundant material that has been used as reinforcing filler to produce polymeric nanocomposites for various applications including automotive, aerospace and electric-electronic. The objective of this study was to develop methodologies of graphite nanosheets preparation and for incorporation into polymer matrices. By means of different chemical and physical treatments, natural graphite was modified and subsequently characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetry (TGA) and the particle size determination. The results obtained clearly show that after the treatments employed, polar chemical groups were inserted on the natural graphite surface. Nanosized graphite particles of high aspect ratio were obtained.

In the present study, a new polypropylene (PP)/multi-walled carbon nanotube (MWCNT) masterbatch is synthesized by in situ polymerization and compared with a masterbatch obtained by melt mixing. Both masterbatches are used for the realization of PP/MWCNT nanocomposites by mixing with a commercial PP in a laboratory extruder. It is shown that the use of masterbatch synthesized in situ allows providing additional enhanced thermal stability and mechanical properties. Samples are characterized according to their thermo dynamicmechanical properties, thermal stability, and degree of crystallinity, as well as by scanning electron microscopy. DMA analysis shows that there is a sharp increase in both storage and loss moduli of materials even with very low CNT content, in comparison with the neat PP. By means of thermogravimetric analysis, it is found that the thermal stability of nanocomposites is also increased. Furthermore, the degree of crystallinity of the materials containing CNTs is increased to higher value than that of neat PP, suggesting that the carbon nanotubes act as nucleating agent. A sharper increase of X c is observed in the composites with low CNT content prepared in the method using meltmasterbatch, suggesting that there are more agglomerations of CNTs in this material.

This study aims to incorporate LLDPE into HDPE in order to improve its processability, as well as to employ a nanoclay for maintaining the HDPE stiffness. Thermal, dynamic-mechanical and rheological properties of polyethylene composites were investigated. Muscovite mica was treated with lithium nitrate for seven cycles, followed by exchange with quaternary ammonium salt to produce organomica. Initially, organomica was added to HDPE at 2% wt. using a tweenscrew mini-extruder. The blend HDPE/LLDPE (1:1 by weight) was also evaluated at the same mica content, with and without the introduction of maleated polyethylene (PEMA) as compatibilizer in order to increase adhesion of polymers with the mineral clay. The samples were evaluated by thermogravimetry (TGA), while melting and crystallization temperatures, and the degree of crystallinity were measured by differential scanning calorimetry (DSC). Rheological properties were evaluated during blending using viscosity and torque curves as a function of processing time. The results showed that stability to thermal degradation of the polyethylene blend with mica increased with the addition of 2% wt. PEMA, where the temperature of maximum degradation rate overcame that of HDPE. The melting endotherm remained narrow in the mixture HDPE/LLDPE/mica, showing good miscibility of the polymer blend; and there was a slight decrease in the melting temperature. The reduction in viscosity during blending revealed improved processing conditions.