Processing stability of high density polyethylene: effect of adsorbed and dissolved oxygen

Epacher, Edina; Tolvéth, János; Kröhnke, Christoph; Pukánszky, Béla

doi:10.1016/s0032-3861(00)00191-9

Cited by 35 publications

(11 citation statements)

References 23 publications

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“…The oxidation of the macroradicals formed as an effect of heat and shear cannot be hindered in the first extrusion of the polymer powder, as it contains absorbed oxygen at a relatively large concentration [35]. As a consequence, the reactions of the polymer are controlled primarily by the number of unsaturated groups and the efficiency of the hydroperoxide decomposing phosphorous secondary antioxidant [32,33].…”

Section: Discussionmentioning

confidence: 99%

Processing stabilisation of PE with a natural antioxidant, curcumin

Tátraaljai

Kirschweng

Kovács

et al. 2013

European Polymer Journal

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The potential use of natural antioxidants for polyolefin stabilisation came into the centre of attention because of some doubts about the effects of the reaction products of synthetic phenolic antioxidants on human health. The effect of curcumin on the melt stability of polyethylene was investigated in this paper with and without a phosphonite stabiliser by using multiple extrusions. Irganox 1010 was applied as reference phenolic antioxidant.Curcumin was characterised by FT-IR and UV-VIS spectroscopy, as well as by thermal analysis. Its stabilisation efficiency was determined by measuring the chemical structure, the rheological properties, the residual thermo-oxidative stability, and the colour of the polymer.The results reveal that the melt stabilising efficiency of curcumin is superior to that of the synthetic antioxidant investigated and is further enhanced by the addition of the phosphonite secondary antioxidant. The changes in the characteristics of the polymer indicate that besides the phenolic OH groups also the linear linkage between the two methoxyphenyl rings of curcumin participates in the stabilisation reactions.

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Section: Discussionmentioning

confidence: 99%

Processing stabilisation of PE with a natural antioxidant, curcumin

Tátraaljai

Kirschweng

Kovács

et al. 2013

European Polymer Journal

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“…Polyethylene is one of the important commodity polymers in the market, and it is therefore not surprising that many efforts were focused on understanding the thermooxidative degradation of polyethylene, since degradation is of crucial relevance for processing [Hinsken et al (1991); Johnston and Morrison (1996); Epacher et al (2000)], for performance under service conditions [Gijsman (2008)], and for recycling [Hakkarainen and Albertsson (2004); Roy et al (2011)]. Chain scission and cross-linking [Arnett and Stacy (1966); Meltzer and Supnik (1964)] as well as long-chain branching (LCB) [Holmstr€ om and S€ orvik (1974)] have been identified as the main structural modifications in polyethylene as a consequence of thermal degradation.…”

Section: Introductionmentioning

confidence: 99%

Increase of long-chain branching by thermo-oxidative treatment of LDPE: Chromatographic, spectroscopic, and rheological evidence

Rolón-Garrido¹,

Zatloukal²,

Wagner³

2013

Journal of Rheology

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SynopsisLow-density polyethylene was thermo-oxidatively degraded at 170 C, i.e., degraded in the presence of air, by a one thermal cycle (1C) treatment during times between 30 and 90 min, and by a two thermal cycles (2C) treatment, i.e., after storage at room temperature, an already previously degraded sample was further degraded during times between 15 and 45 min. Characterization methods include gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, as well as linear and nonlinear rheology. A reduction of molar mass was detected for all degraded samples by GPC, as well as an increase of the high molar mass fraction of the 1C sample degraded for the longest time. Intrinsic viscosity measurements indicate also a reduction of molar mass with increasing degradation times for both 1C and 2C samples. Thermo-oxidation is confirmed for 1C and 2C samples by analyzing specific indices in FTIR. Linear viscoelasticity seems to be in general only marginally affected by thermo-oxidative exposure, while the enhanced strain-hardening effect observed in uniaxial extension experiments presents a clear evidence for an increased long-chain branching (LCB) content in both 1C and 2C samples. Elongational viscosity data were analyzed by the molecular stress function (MSF) model as well as the Wagner-I model, and for both models, quantitative description of the experimental data for all samples was achieved by fit of only one nonlinear model parameter. Time-deformation separability was confirmed for all samples degraded, 1C as well as 2C, for cumulative degradation times of up to 90 min. The characterization by GPC was confronted with the characterization obtained from nonlinear rheology. It can be stated that elongational rheology is a powerful method to detect structural a) Author to whom correspondence should be addressed; electronic mail: victor.h.rolongarrido@tu-berlin.de

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“…However, it is possible that oxidation is concentrated in the black spots that were formed in the material (see Figure 8) and that could not be examined by color, UV-Vis, and FTIR measurements. The black spots are probably formed when catalyst residues from polymer synthesis, like titanium chloride (e.g., TiCl 3 ) and chromium (Cr) particles, react with the phenolic antioxidant to produce chromophoric species, such as titanium phenolates [34][35][36][37]. As these catalyst residues promote hydroperoxide decomposition [38], oxidation preferentially starts at the polymercatalyst interface.…”

Section: Ftir Spectroscopy Ftir Spectroscopy Results Are Shown Inmentioning

confidence: 99%

Discoloration Effects of High-Dose γ-Irradiation and Long-Term Thermal Aging of (U)HMW-PE

Kömmling

Chatzigiannakis

Beckmann

et al. 2017

International Journal of Polymer Science

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Two polyethylene types with ultra-high (UHMW-PE) and high molecular weight (HMW-PE) used as neutron radiation shielding materials in casks for radioactive waste were irradiated with doses up to 600 kGy using a 60 Co gamma source. Subsequently, thermal aging at 125∘ C was applied for up to one year. Degradation effects in the materials were characterized using colorimetry, UV-Vis spectroscopy, IR spectroscopy, and DSC. Both materials exhibited a yellowing upon irradiation. The discoloration of UHMW-PE disappeared again after thermal aging. Therefore, the yellowing is assumed to originate from annealable color centers in the form of free radicals that are trapped in the crystalline regions of the polymer and recombine at elevated temperatures. For the antioxidantcontaining HMW-PE, yellowing was observed after both irradiation and thermal aging. The color change was correlated mainly to decomposition products of the antioxidant in addition to trapped radicals as in UHMW-PE. Additionally, black spots appeared after thermal aging of HMW-PE.

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Processing stability of high density polyethylene: effect of adsorbed and dissolved oxygen

Cited by 35 publications

References 23 publications

Processing stabilisation of PE with a natural antioxidant, curcumin

Processing stabilisation of PE with a natural antioxidant, curcumin

Increase of long-chain branching by thermo-oxidative treatment of LDPE: Chromatographic, spectroscopic, and rheological evidence

Discoloration Effects of High-Dose γ-Irradiation and Long-Term Thermal Aging of (U)HMW-PE

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