Loss of additives from polymers: A theoretical model

Abstract

SynopsisThe rate at which an additive is lost from the surface of its solution in a polymer is considered to depend upon three factors-the solubility of the additive, the rate at which it volatilizes from the polymer surface, and its diffusion coefficient within the bulk of the polymer. By adapting the mathematics of heat flow in a solid, the loss of additive from a polymer is mathematically modeled in terms of these three variables for bulk polymer and for film and fiber samples. Two cases are considered-loss of additive by volatilization or dissolution from the polymer surface and loss by precipitation on the surface from a supersaturated solution of the additive. The results are applied to a discussion of the relative importance of the three parameters under various conditions occurring or expected in practical application of additives as oxidation stabilizers for polyethylene and polypropylene.

Performance of PE pipes under extractive conditions: Effect of the additive package and processing

“…Gedde et al [18,19,24] divided the time dependence of stabilizer loss and chemical degradation into three stages: the precipitation and segregation of the additive, leaching, and the autoxidation of the polymer. Although segregation might occur indeed, Dörner et al [25] did not find a stepwise decrease in stabilizer content and OIT with time, and Billingham [26] could not prove the existence of additive droplets in the poly-4 mer. Nevertheless, it is clear that the hydrolytic and chemical stability, solubility and diffusion of additives are crucial factors determining the lifetime of polyolefin pipes especially when they are in contact with extractive media.…”

Kinetic modelling of phenols consumption during polyethylene thermal oxidation

“…Implementing the kinetic approach requires understanding the stabilizer physico-chemistry, which is very complex [7]:  Stabilizer can be consumed by chemical reaction or lost by evaporation or extraction [8].…”

Investigation of thermo-oxidative ageing effects on the fatigue design of automotive anti-vibration parts

“…Moreover the MATEC Web of Conferences 165, 08004 (2018) https://doi.org/10.1051/matecconf/201816508004 FATIGUE 2018 origins of the evolutions of mechanical properties both for stiffness, failure or fatigue still remain unclear. Several explanations could be suggested: plasticizers diffusionevaporation [22], sulfur network evolution [10,17], fillers network evolution [23] and/or evolution of the interface rubber/fillers [24]. The present paper aims providing an extensive comparison of the mechanical consequences of ageing under anaerobic and aerobic conditions, based on the results of monotonic tensile tests and fatigue tests.…”