Thermal oxidation of clay-nanoreinforced polypropylene

Abstract

a b s t r a c tThe thermo-oxidation process at low temperatures for a montmorillonite-nanoreinforced polypropylene (PP) was studied. Experimental aging kinetic data at 100, 80 and 60 C have been obtained and compared with a computational simulation in which a kinetic model based on the closed loop approach was used. As a result, it has been found that the montmorillonite role is not limited to a role of inert filler in the polymer matrix but induces a slight catalytic effect leading to induction period reduction. This effect has been well simulated by increasing initial hydroperoxyde concentration. The consequences of kinetic control by oxygen diffusion have also been investigated by using micro ATR-FTIR mapping to assess concentration profiles of the oxidation products across the sample thickness. It has been found that the oxidized layer thickness is close to 17 mm for the pure polypropylene whereas it is around 10 mm for the nanocomposite at 100 C. These profile variations have been attributed to differences in oxygen diffusion coefficient values. Simulations based on the kinetic model including diffusion-reaction coupling describe these profiles well.

Co-oxidation kinetic model for the thermal oxidation of polyethylene-unsaturated substrate systems

“…It is well documented that oxidation can be favored by metallic impurities playing a catalytic (redox) role [7] or by species such as carboxylic acids capable of establishing strong hydrogen bonds with the polymeric ROOH groups [8]. These cases of assisted oxidation differ from the co-oxidation phenomena described in this current study.…”

Polypropylene stabilization by hindered phenols – Kinetic aspects

“…g COu k 1u ½POOH þg COb k 1b ½POOH 2 (10) g COu and g COb being the carbonyl yields of respectively uni-and bimolecular POOH decomposition taken equal to 1 from previous study [43]. (1 À x C ) term is included to take into account the fact that oxidation possibly occurs only in amorphous phase.…”

The synergistic mechanism of thermally reduced graphene oxide and antioxidant in improving the thermo-oxidative stability of polypropylene

“…These additives usually work as radical scavengers to capture peroxy radicals and to suppress the thermo-oxidative degradation of PP chains. Considering the crucial role of oxygen in the degradation process of PP chains, lamellar nanoparticles like layered silicates have also been used widely to suppress the degradation of PP by taking advantage of their excellent oxygen barrier performance [4].…”