Distribution of an antioxidant in polypropylene/ethylene-octene copolymer blends studied by atomic force microscopy-infrared

In this work, the microscopic distribution of antioxidant 1010 (AT1010) in blends of isotactic polypropylene (iPP) with an ethylene-octene copolymer (POE) was investigated in situ using the atomic force microscopy-infrared (AFM-IR) technique. Pellets of an iPP/POE blend containing AT1010 at a mass ratio of 79.5 : 20 : 0.5 were extruded at different screw speeds, and were then injection-molded into plates. The domain size of the POE disperse phase in the pellets was about 1 μm, regardless of the screw speed, and remained unchanged in the injection molding. AFM-IR analyses revealed that AT1010 preferred to stay in the POE disperse phase rather than in the iPP matrix, with a concentration ratio of ∼1.2 in the extruded pellets independent of the screw speed, which was further increased to ∼1.5 in the molded plates. The preferred concentration of AT1010 in the POE was in line with its higher solubility in rubber than in iPP, and the enhanced partition of AT1010 in the molded plates was attributed to a longer processing time in the molten state than that for the extruded pellets, which was verified by AFM-IR analyses of pellets extruded with different residence times.

Study on the Bleeding Mechanism of Slip Agents in a Polypropylene Film using Molecular Dynamics

The bleeding (internal transport) process of additives in a polypropylene film under atmospheric pressure was investigated. The experimental results were explained more precisely by a new model assuming the two-step transport between the amorphous and crystalline regions. The diffusion coefficient of a higher fatty acid such as behenic acid (docosanoic acid) in isotactic polypropylene film and that of higher fatty acid amides such as erucamaide (13-cis-docosenamide) in ethylene copolymerized polypropylene film were determined at 40 and 50°C respectively. The difference between the diffusion coefficients of three slip agents in a polypropylene film at 50°C was explained using a molecular dynamics simulation in which self-association of the slip agent molecules by hydrogen bonding was considered.