Abstract
The compatibilization of raw bentonite (bent) with a polymer matrix of polypropylene (PP) can improve the performance of the material in terms of thermal and mechanical properties. In this study, two kinds of untreated bentonite, bentonite-Maghnia (bent-m) and bentonite-Mostaganem (bent-M), that differ in the proportion of Al2O3 and in the particle size distribution were coupled to typical maleic anhydride grafted polypropylene PP-MA. Stearic Acid (SA) and L-leucine Amino Acid (AA) were selected as new coupling modifiers at a 5/5 ratio of bentonite/coupling agent. All PP/bent composites were prepared by melt mixing at 190°C. Morphological observation revealed a good dispersion of bentonite into the PP matrix in the presence of AA, SA, and PP-MA. Mechanical properties showed an increase in stiffness as bent-m or bent-M were associated with AA. For instance, PP/bent-m/AA composite underwent an improvement of about 13% in Young’s modulus as compared to neat PP. On the other hand, the addition of SA into bent-m maintained stiffness and tensile strength at an acceptable level. An increase of around 40°C and 37% in the decomposition temperature and elongation at break was respectively observed for the PP/bent-m/SA composite. All coupled composites showed high degradation temperatures.
Highlights
The development and characterization of polymer/clay nanocomposites has been the subject of increasing interest because these systems habitually show significant improvement in thermal, mechanical, and barrier properties when compared with virgin polymers or conventional micro or macro composites for the same amount of filler
It was observed that the addition of 5% of Amino Acid (AA) and polarity compared to maleic anhydride grafted polypropylene (PP-MA) to the polymer matrix loaded with 5% bent-m increased the torque values of the systems (31N.m, 25N.m), suggesting that the composites required more severe processing conditions in its presence
This was in agreement with the findings of the authors of [23], who reported that during the processing of the PP/modified bentonite composites, the stearic acid is acting as an interface modifier and lubricant and decreases the viscosity of the melt compound due to the free movement of the polymer chains
Summary
The development and characterization of polymer/clay nanocomposites has been the subject of increasing interest because these systems habitually show significant improvement in thermal, mechanical, and barrier properties when compared with virgin polymers or conventional micro or macro composites for the same amount of filler. Bentonite is used in diverse branches of industry for the fabrication of several ceramic products mainly due to its rheological properties. It is used as a component in dyes, pharmaceuticals, paper [12,13,14,15], and in polymer composites [16]. In [17], two different bentonite/PP composites were synthesized, with and without pore-enlarging treatment. These granular composite adsorbents were effective in eliminating Pb2+ in aqueous solutions
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