Radical scavenging capacity of lignin and its effect on processing stabilization of virgin and recycled polypropylene

Abstract

ABSTRACT:The radical scavenging capacity of lignin was determined using spectrophotometric method by means of scavenging of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH ) and compared with that of synthetic antioxidant Irganox 1010. Lignin reacted progressively with the DPPH reaching a steady state in 6 h, showing high antiradical activity with a stochiometry of 5.5 reduced DPPH molecules. Irganox 1010 showed lower antiradical activity reaching a steady state with DPPH after 13 h. Moreover, stabilization efficiency of lignin has been investigated in virgin and recycled polypropylene. The stabilization effect of lignin was evaluated by melt volume rate (MVR). The efficiency of lignin as processing stabilizer in both series polypropylene samples was compared with that of synthetic antioxidant Irganox 1010. The presence and behavior of free radicals in the lignin/polypropylene composites formed during processing was determined by electron paramagnetic resonance (EPR). It was observed that used lignin sample could stabilise both virgin and recycled polypropylene.

Potential of Lignins as Antioxidant Additive in Active Biodegradable Packaging Materials

“…In the field of material applications, the antioxidant activity has been investigated in the aim of using lignin as a natural substitute of synthetic antioxidants required for the formulation of polyolefins [22][23][24][25]. Pouteau et al [26] showed that the compatibility between lignin and polymer matrix could be successfully predicted using the solubility parameters calculated after the Small, Van Krevelen and Hoy method.…”

Effect of Reprocessing Cycles on the Morphology and Properties of Poly(propylene)/Wood Flour Composites Compatibilized with EBAGMA Terpolymer

“…One of them is related to the presence of lignocellulosic filler in the polymer matrix, which imparts stability to the composite materials by the presence of lignin acting as natural antioxidants. As a matter of fact, some authors [31] Effect of Reprocessing Cycles on the Morphology and . .…”

“…The results suggest that the PP material should not be recycled more than one time. According to the literature, [17,[29][30][31] behavior is due to degradation by chain scission giving rise to a significant decrease in molecular weight and subsequently to lower viscosity. The combination of high temperature, shear and the presence of oxygen and chromophoric species such as hydroperoxides, carbonyl groups and catalyst residues in the polymer matrix, could be the main factors promoting degradation.…”

Natural antioxidants as stabilizers for polymers

“…Most of the attempts proved the antioxidant effect of lignin. The antioxidant and stabilizing characteristics of lignin have been studied in several polymers, but mainly in PE [153][154][155][156], PP [153,[157][158][159][160][161][162][163][164], PLA [165,166], poly(3-hydroxybutyrate) (PHB) [167], PCL [168] and in natural rubber [169,170].…”