Induction Time Tests Research Articles

Polyurethane–zinc borate composites with high oxidative stability and flame retardancy

Novel polyurethane zinc borate composites were prepared with the main aim to increase the flame retardancy of the polyurethane. It was discovered that the zinc borate had very significant effects on the oxidative stability of the neat polymer which was first observed by oxygen induction time tests and supported with actual weathering chamber tests. The oxidative stability of zinc borate-filled polyurethane was compared with the polyurethane stabilized with a commercial light stabilizer, Tinuvin B75 from Ciba SC. The performance of zinc borate-filled polyurethane was much better, as shown by oxygen induction time and weathering chamber tests. Additionally the flame retardancy was measured and significant flame retardancy was achieved. Mechanical tests, thermogravimetric analysis and scanning electron microscope studies were performed to characterize the products.

Depletion of Antioxidants from a HDPE Geomembrane in a Composite Liner

The results of two series of accelerated aging tests are reported. Both series of tests were conducted at temperatures of 85, 70, 55, and 26°C over a period of about 3years. In the simulated liner series, the top of the geomembrane was covered with a geotextile (protection) layer that was exposed to simulated municipal solid waste (MSW) landfill leachate while the bottom of the geomembrane was in contact with a hydrated geosynthetic clay liner. In the immersion series, the geomembrane was immersed in the simulated MSW leachate, and hence, both sides were exposed to leachate. The results from oxidative induction time tests indicate that the antioxidant depletion is about 2.2–4.8 times faster for the leachate immersed geomembrane than for geomembrane in a composite liner. The higher rates are attributed to the higher extraction of antioxidants from two sides of the geomembrane immersed in leachate. The measured antioxidant depletion rates are extrapolated to a range of temperatures (0–60°C) using Arrhenius modeling. At a liner temperature of 35°C, the calculated time for the depletion of antioxidants is about 40years for a geomembrane in a composite liner compared to 10years if it is simply immersed in leachate. These tests suggest that to obtain realistic estimates of geomembrane service life one needs data from tests that simulate the expected field conditions and that prediction based on immersion tests may underestimate the service life.

Investigation of antioxidant and electron beam radiation effects on the thermal oxidation stability of low-density polyethylene

Effect of various antioxidants on the thermal oxidation stability of LDPE and X-LDPE has been investigated. To achieve this purpose, miscellaneous commercial grade antioxidants such as Irganox 1010, Irganox1076, Irgafos168, Irganox B225, and Chimassorb 944 were selected. Then, formulations based on different content of antioxidant were prepared. The samples were crosslinked by exposure to electron beam irradiation. To assess the thermal oxidation stability of samples, oxidation induction time (OIT) test was accomplished on both the irradiated and unirradiated specimens. Ageing tests were carried out in order to evaluate the thermal oxidation stability of irradiated X-LDPE. The results indicate that Irganox 1010 is the most effective antioxidant amongst the selected ones, concerning thermal oxidation stability of LDPE, before and after aging test.

Analysis of the degradation of poly(1‐butene) pipe through oxidation induction time tests

AbstractThe oxidation induction time (OIT) test is a powerful technique for evaluating the oxidative stability and/or degradation of polymers. It is especially effective in examining the relative utility of antioxidants on the stability of oxidizable polymers. It is also useful in determining whether or not antioxidants have been leached from the polymer, thus negating their effectiveness. In this study, the OIT test has been used to show the loss in effectiveness of antioxidant from the interior surface of poly(1‐butene) pipe used to convey potable water. The loss in antioxidant effectiveness was confirmed by significantly reduced OIT times. Confirmation of oxidation of the polymer was subsequently made by IR analysis. © 2005 Wiley Periodicals, Inc. Adv Polym Techn 24:215–225, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20045

Reinforcing Effect of Organo-modified Layered Silicates in High-Density Polyethylene

This study focuses on the understanding of the reinforcing effect given by organo-modified layered silicates to a high-density polyethylene and the influence on the crystallization properties of this polymer. The addition of organo-modified clay to high-density polyethylene resulted in an evident increase in the tensile and flexural Young's modulus of the material with respect to unfilled polymer. The morphology, crystallinity, and thermo-oxidative stability of such nanocomposites were investigated using X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, and oxidation induction time test. The materials obtained show tactoid as well as intercalated and exfoliated structures with different dominant states depending on the loading level and process conditions. It was observed that organic ions not only change mixing behavior but also influence material properties, including the degree of crystallinity and the stability to the thermo-oxidative phenomena.

Plasma carbon black—the new active additive for plastics

The paper presents the carbon black production by plasma method and the thermal–mechanical and oxidation induction time tests of LDPE and HDPE modified by changeable content of plasma carbon from 0.1 to 1.0% w/w. The investigations were based on SEM images, microscope images and XRD studies. Properties of plasma carbon black were measured by physical and chemical tests like BET adsorption, IA and DBF numbers, etc. The results of ageing tests showed the increased oxidation induction time, 57 min, for 0.5% w/w of plasma carbon black content in the composition.

Interlaboratory test on polymers: determination of oxidation induction time and oxidation induction temperature by differential scanning calorymetry

The results of the oxidation induction time (OIT) tests indicate that the determination of OIT involves a high degree of uncertainty in respect of the measured data, particularly for low OIT values. This would seem to show that OIT measurements have an extremely critical significance for quality control purposes or lifetime predictions of polyolefin parts. Determining oxidation induction temperature (OIT*) could therefore be a valuable alternative for less stabilized polyolefins (low OIT values) in particular. However, OIT* measurement clearly indicates that the ability to distinguish between different samples decreases drastically as OIT* data increase. Generally, the evaluated data can be used to estimate the results of in-house and external OIT/OIT* measurements and their compatibility. This report should therefore support day-to-day work in analytical laboratories where oxidation induction values are measured by DSC.

Mechanical properties and resistance to oxidation tests of cable polyethylene modified with plasma carbon black

The new kind of cable polyethylene was produced by modification with plasma carbon black, which can be use as an antioxidant and pigment. The paper presents mechanical and oxidation induction time tests of cable polyethylene modified with changeable content of plasma carbon black from 0.1 % to 1.0 wt. %. The mechanical tests enclose Brinell-Vickers hardness number, melt flow rate and static tensile strength. The results showed the increased oxidation induction time, 57 min, for 0.5 wt. % of plasma carbon black in the composition. The results were compared with those concerning commercial cable polyethylene modified by furnace carbon black.

The effect of silica and siloxane on thermo-oxidative degradation of hydrogen-bonded acidic fluorinated poly(amide-imide-silica) hybrids

The effect of silica and siloxane on thermo-oxidative degradation of a series of hydrogen-bonded acidic fluorinated poly(amide-imide-silica) hybrids was investigated by TGA, IR and OIT tests. Silica was proved to enhance the first stage thermo-oxidative decomposition of the hybrids without siloxane segments from the values of the first stage weight loss and activation energy. However, the effect of siloxane was more dominant than that of silica when a flexible siloxane segment was incorporated, proved by lower glass transition temperatures from DSC examination. Silica and siloxane effect were also confirmed by the difference of IR intensity ratios of the degraded hybrids. Moreover, the results of oxidative induction time (OIT) test were consistent with the sequence of the first stage activation energy.

Application of the oxidative induction test to depolymerizing systems

Since the development of the oxidative induction time (OIT) test by former Bell Telephone Laboratories researchers, there have been many studies to broaden its applicability to polymers beyond the original polyolefins. The basic premise in OIT studies is that a detectable oxidation onset is based on the differential reactivity between the polymer matrix and free radical scavenging antioxidants like hindered phenols. This situation does not exist in depolymerizing systems such as polymethylmethacrylates (PMMA), so many researchers concluded that a correlation did not exist for these systems. We will report on the observation of a clear cut, Arrhenius-like oxidative induction time behavior in a toughened PMMA system with high pressure DSC. The relationship between the observed OIT at elevated temperatures and high oxygen pressures with lower temperature oven aging studies will be presented.

Interactions between carbon black and stabilisers in LDPE thermal oxidation

The interactions between two commercial hindered piperidine compounds, three commercial antioxidants, a secondary antioxidant and two types of furnace carbon blacks (with a different surface area and surface chemistry) in the thermal oxidation of LDPE have been studied using the oxidation induction time test. During thermal degradation the interactions were variable, being both antagonistic and synergistic. Generally, for the primary antioxidants alone their thermal stabilising effects on the polymer were decisive and related to their chemical structure, with the main contribution being their synergism with HALS and a secondary antioxidant. Differences in the performance of the polymeric type of HALS were evidenced, as well as between the CB grades. Minor synergism and antagonism was found between HALS and CB depending on the chemical structure of the HALS. All the detected antagonisms were widely overcome by the synergistic interaction found in three- and four-additive formulations. Though the presence of CB (at the concentrations studied) was not a decisive factor in the LDPE thermal stability, its presence nevertheless showed a beneficial effect. The nature of the CB plays some role in controlling its performance as a stabilising agent alone, as well as its interactions with HALS and antioxidants, via adsorption-desorption processes as well as other chemical interactions as was evidenced by adsorption studies via flow microcalorimetry (FMC).

98/03816 Standardization of oxidation induction time testing used in life assessment of polymeric electric cables

98/03816 Standardization of oxidation induction time testing used in life assessment of polymeric electric cables

Antioxidant Depletion Lifetime in High Density Polyethylene Geomembranes

A major issue in the use of geomembranes for waste containment is an estimate of the material's durability (i.e., its lifetime) to various aging phenomena. For high density polyethylene geomembranes, which are the focus of this study, there are three stages in assessing lifetime: depletion of antioxidants, induction time, and time to reach half-life of a relevant engineering property. This paper addresses the first stage of these three sequential processes. Twenty laboratory incubation devices were made to simulate landfill conditions. Four sets of five columns were maintained at elevated temperatures of 85, 75, 65 and 55°C. Samples were retrieved at various intervals over a 24-month incubation period. Various physical, mechanical, and chemical properties were evaluated. The depletion of antioxidants in the incubated samples was monitored using both standard and high pressure oxidative induction time tests. Arrhenius modeling was used on the data to extrapolate the antioxidant lifetime to a typical landfill site temperature of 20°C. The resulting predicted time was 200 to 215 years. Also, it should be emphasized that within this period of time the physical and mechanical properties of the incubated samples remained unchanged.

Standardization of oxidation induction time testing used in life assessment of polymeric electric cables

Oxidation induction time (OIT) has been proven to be a useful diagnostic tool in assessing the extent of degradation in the polymer insulation of electric cable in nuclear power plants. Factors that influence OIT include test temperature, sample preparation, sample geometry, sample mass, particle size, thermogram interpretation, and shelf life. The effects of these parameters were investigated for ethylene propylene diene monomer (EPDM) and crosslinked polyethylene (XLPE) polymer cable insulations, which were aged in radiation and thermal environments. The results were then used to recommend standards for an OIT methodology suited for practical use in the nuclear power industry. Techniques to estimate error in thermogram interpretation and reproducibility were also developed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1691–1702, 1997

Standardization of oxidation induction time testing used in life assessment of polymeric electric cables

Oxidation induction time (OIT) has been proven to be a useful diagnostic tool in assessing the extent of degradation in the polymer insulation of electric cable in nuclear power plants. Factors that influence OIT include test temperature, sample preparation, sample geometry, sample mass, particle size, thermogram interpretation, and shelf life. The effects of these parameters were investigated for ethylene propylene diene monomer (EPDM) and crosslinked polyethylene (XLPE) polymer cable insulations, which were aged in radiation and thermal environments. The results were then used to recommend standards for an OIT methodology suited for practical use in the nuclear power industry. Techniques to estimate error in thermogram interpretation and reproducibility were also developed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1691–1702, 1997