Effect of clay amount and reprocessing cycles on thermal, morphological, and mechanical properties of polypropylene/organovermiculite nanocomposites

Abstract

Nanocomposites of polypropylene (PP) and PP-grafted-maleic anhydride (PP-g-MA) with and without organophilic vermiculite (OVMT) (5-8%w/w) were evaluated. The nanocomposites and neat PP were submitted to extrusion reprocessing cycles. It was found that the presence of OVMT in PP/PP-g-MA was critical for maintaining thermal stability during reprocessing. The exfoliation/intercalation was confirmed, mainly, in the nanocomposite submitted to reprocessing cycles, by X-ray diffraction. The melt flow index (MFI) values for the 3× and 5× reprocessed PP increased by 40% and 70%, respectively, as compared to the neat PP. The MFI for the 3× and 5× reprocessed PP/PP-g-MA/OVMT decreased 26% and 17%, respectively, as compared to the decrease occurred in the 3× and 5× reprocessed PP, indicating that the presence of 5% (w/w) OVMT was sufficient to allow an increase in viscosity. The reprocessed nanocomposites exhibited values for tensile and flexural strengths and Izod impact, in general, greater than or near to those of PP with the same number of reprocessing cycles. The increase or maintenance of mechanical properties seems to depend on a balance between the extent of intercalation/exfoliation and dispersion of OVMT in the PP matrix, and the degree of degradation of the PP matrix. POLYM. ENG. SCI., 59:2110-2120

Degradation Behavior of Polypropylene during Reprocessing and Its Biocomposites: Thermal and Oxidative Degradation Kinetics

“…The molecular weight drop during the reprocessing of PP can be also accounted for by an increase in the melt flow index with the reprocessing cycles. Figure 1 b shows that the values of MFR for PP increased as a function of the number of reprocessing cycles, indicative of the molecular weight loss of the polymer matrix during reprocessing [ 34 ]. Research findings have shown an inverse relation between MFR and apparent viscosity, which directly relates to chain length [ 35 ].…”

“…number of reprocessing cycles, indicative of the molecular weight loss of the polymer matrix during reprocessing [34]. Research findings have shown an inverse relation between MFR and apparent viscosity, which directly relates to chain length [35].…”

Recycling effects on the bending, rheological, and structural properties of glass fiber-reinforced isotactic polypropylene composites

“…The increment of the MFI means a drop in the melt viscosity and consequently a negative change in the plastic's molecular weight as confirmed by the work of Araújo et al 69 They reported a polymer viscosity decrease caused by a reduction in intermolecular interactions and entanglements which leads to reductions in molecular weight and the length of the polymer chain. The MFI for the virgin PP was provided by the datasheet of the PP manufacturer and the glass fiber-reinforced PP had an increase of 57% after passing through the screws of the extruder in 10 runs from the first run.…”

Influence of nucleation and growth mechanisms on the heat deflection temperature of a reactively processed polypropylene nanocomposite

“…[ 1,4‐8 ] The effects of different types of nanoclays on the crystallization temperature of PP composites have also been studied in detail. [ 9‐11 ] However, correlations of crystallization, recrystallization, and crystal growth mechanisms with the obtained thermomechanical properties of the polymer nanocomposite have been rarely discussed. A recent study showed that the HDT of a PP/LLDPE (linear low‐density polyethylene) blend decreases in the presence of talc.…”