Mechanical and rheological properties of polypropylene/bentonite composites with stearic acid as an interface modifier

Abstract

In this study, we present a study of polypropylene/bentonite composites where stearic acid was used as both a surface and interface modifier during the compounding of composites. The concentration of bentonite was 1.5, 2.5, 5.0, and 10 parts per hundred. The composites were characterized by impact resistance and tensile tests, rheological analysis, the dispersion state of the filler observed by optical microscopy, and interaction between bentonite and stearic acid, as analyzed by Fourier transform infrared spectroscopy. No chemical interaction was found between bentonite and stearic acid. Composites with modified bentonite and stearic acid used as interface modifiers increased the elongation at break; these samples also showed better dispersion of the filler in comparison with the other compounds. In addition, stearic acid acted as a lubricant, favoring the interaction of the polymer with the filler and decreasing the viscosity of the compounds.

Preparation of Polypropylene/Bentonite Composites of Enhanced Thermal and Mechanical Properties using L-leucine and Stearic Acid as Coupling Agents

“…The enhancement of lubricity through the processing provided fine dispersion of the filler, and it was also in accord with the decrease in dimension and quantity of agglomerates showed by the SEM. 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 thus decreases the viscosity of the melt compound due to the free movement of the polymer chains. These effects enhanced the mechanical behavior by improving the elongation at break of the composite.…”

“…However, HDPE compatibilized with ethylene-acrylic acid copolymer (EAA) leads to poor dispersion due to its immiscibility with the HDPE matrix. Recently, authors in [23] confirmed that the composites containing modified bentonite in presence of stearic acid used as interface modifier induce a better dispersion of the filler, a decrease in viscosity and an increase in elongation at break of the composites based on PP matrix. Also, authors in [24] established that stearic acid favored the dispersion of PP/MMT nanocomposites when used as interface modifier and clay surface treatment.…”

“…The intense broad-band with the maximum at 1041cm -1 ranged at 1040-1080cm -1 corresponds to the Si-O-Si valence vibration of the SiO 4 . In addition, the narrow peak at 797cm -1 corresponds to the silanol group [41] and at around 600cm -1 corresponds to Si-O-Al [23]. The peak recorded at 1439cm -1 is associated with the presence of calcite in the sample [42].…”

Effects of Surface Modification with Stearic Acid on the Dispersion of Some Inorganic Fillers in PE Matrix

“…Zaharri N. et al also 2 of 9 reported that the mechanical properties of zeolite/propylene composite in the presence of stearic acid coupling agent was better than without stearic acid [14]. Angle et al found that the elongation at break of the composites containing modified bentonite increased, and the dispersion of bentonite was better in comparison with those containing unmodified bentonite [11]. Therefore, the aim of this study is to evaluate the dispersibility of stearic acid modified and unmodified inorganic fillers (bentonite, silica) in PE matrix.…”

“…However, due to the hydrophilic nature of these additives, it is necessary to treat their chemical surfaces before mixing them to increase their compatibility and dispersion into the PE matrix. To create the hydrophobic surface with the aim of increasing the compatibility of fillers with polymer molecules, fatty acids, such as oleic acid, stearic, palm oil [10][11][12] are often used. Stearic acid is most commonly used because of its advantages such as low cost and easy processing.…”