Abstract
Data by dynamic differential thermal analysis are presented on a series of polyethylene samples containing known contents of two primary (phenol and amine) and two secondary (thioester and phosphite) antioxidants. A relationship between the oxidation temperature and the concentration of antioxidant is derived on the assumption that the antioxidant consumption follows zero-order kinetics and that the rate constant may de defined in accordance with the Arrhenius equation. This equation fits the presented experimental data for samples with intimately mixed antioxidant. Changes in polymer structure and antioxidant concentration have been systematically studied as a function of temperature, hoop stress, exposure time and location in pipe wall on pressure tested pipes of medium-density polyethylene and isotactic polybutene-1. Pipes, which have been exposed at elevated temperature, 105, 95 or 80 degrees C, to water as the internal and air or water as the external medium, have exhibited different failure mechanisms, referred to as stages 1,2 and 3. A numerical model, which describes the time evolution of antioxidant concentration profiles in the exposed material in terms of adjustable parameters, has been used to describe the rates of diffusion, evaporation, extraction, and chemical reaction of antioxidant. The results indicate that for polyethylene pipes in water/air
More>>
Citation Formats
Karlsson, Kjell.
Molecular structure, morphology and antioxidant consumption in polyolefin pipes in hot-water applications.
Sweden: N. p.,
1991.
Web.
Karlsson, Kjell.
Molecular structure, morphology and antioxidant consumption in polyolefin pipes in hot-water applications.
Sweden.
Karlsson, Kjell.
1991.
"Molecular structure, morphology and antioxidant consumption in polyolefin pipes in hot-water applications."
Sweden.
@misc{etde_10133875,
title = {Molecular structure, morphology and antioxidant consumption in polyolefin pipes in hot-water applications}
author = {Karlsson, Kjell}
abstractNote = {Data by dynamic differential thermal analysis are presented on a series of polyethylene samples containing known contents of two primary (phenol and amine) and two secondary (thioester and phosphite) antioxidants. A relationship between the oxidation temperature and the concentration of antioxidant is derived on the assumption that the antioxidant consumption follows zero-order kinetics and that the rate constant may de defined in accordance with the Arrhenius equation. This equation fits the presented experimental data for samples with intimately mixed antioxidant. Changes in polymer structure and antioxidant concentration have been systematically studied as a function of temperature, hoop stress, exposure time and location in pipe wall on pressure tested pipes of medium-density polyethylene and isotactic polybutene-1. Pipes, which have been exposed at elevated temperature, 105, 95 or 80 degrees C, to water as the internal and air or water as the external medium, have exhibited different failure mechanisms, referred to as stages 1,2 and 3. A numerical model, which describes the time evolution of antioxidant concentration profiles in the exposed material in terms of adjustable parameters, has been used to describe the rates of diffusion, evaporation, extraction, and chemical reaction of antioxidant. The results indicate that for polyethylene pipes in water/air exposure extraction by the water phase is the dominating loss mechanism. The model also shows that for polybutene-1 pipes the migration of antioxidant was the dominant loss mechanism, that the diffusion coefficient was constant through the pipe wall and that the evaporative loss to the external air was marginally greater than the loss to the internal water phase. For both the polyethylene and the polybtene-1 pipes the chemical consumption of the antioxidant was found to be negligible. (19 refs., 5 tabs., 22 figs.).}
place = {Sweden}
year = {1991}
month = {Dec}
}
title = {Molecular structure, morphology and antioxidant consumption in polyolefin pipes in hot-water applications}
author = {Karlsson, Kjell}
abstractNote = {Data by dynamic differential thermal analysis are presented on a series of polyethylene samples containing known contents of two primary (phenol and amine) and two secondary (thioester and phosphite) antioxidants. A relationship between the oxidation temperature and the concentration of antioxidant is derived on the assumption that the antioxidant consumption follows zero-order kinetics and that the rate constant may de defined in accordance with the Arrhenius equation. This equation fits the presented experimental data for samples with intimately mixed antioxidant. Changes in polymer structure and antioxidant concentration have been systematically studied as a function of temperature, hoop stress, exposure time and location in pipe wall on pressure tested pipes of medium-density polyethylene and isotactic polybutene-1. Pipes, which have been exposed at elevated temperature, 105, 95 or 80 degrees C, to water as the internal and air or water as the external medium, have exhibited different failure mechanisms, referred to as stages 1,2 and 3. A numerical model, which describes the time evolution of antioxidant concentration profiles in the exposed material in terms of adjustable parameters, has been used to describe the rates of diffusion, evaporation, extraction, and chemical reaction of antioxidant. The results indicate that for polyethylene pipes in water/air exposure extraction by the water phase is the dominating loss mechanism. The model also shows that for polybutene-1 pipes the migration of antioxidant was the dominant loss mechanism, that the diffusion coefficient was constant through the pipe wall and that the evaporative loss to the external air was marginally greater than the loss to the internal water phase. For both the polyethylene and the polybtene-1 pipes the chemical consumption of the antioxidant was found to be negligible. (19 refs., 5 tabs., 22 figs.).}
place = {Sweden}
year = {1991}
month = {Dec}
}