Chemical reactions during the processing of stabilized PE: 1. Discolouration and stabilizer consumption

Epacher, Edina; Fekete, Erika; Gahleitner, Markus; Pukánszky, Béla

doi:10.1016/s0141-3910(98)00078-0

Cited by 25 publications

(21 citation statements)

References 25 publications

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“…(2), that is, c 0 exp(ϪkЈ 1 n), and the measured OIT values. 1 It was shown 1 that OIT 0 ϭ 0, showing that the neat polymer has a much lower stability than the stabilized samples.…”

Section: Stabilitymentioning

confidence: 99%

“…1,2 An analysis of the data and additional experiments indicated that all chemical reactions are related to each other. The reactions of the stabilizer lead to color development, [12][13][14][15][16][17] and that of the polymer leads to changes in its molecular structure, which, on the other hand, determine the rheological properties of the granulates 11,18,19 and the mechanical characteristics of the films blown from them.…”

Section: Introductionmentioning

confidence: 99%

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Two-step degradation of high-density polyethylene during multiple extrusion

Epacher

Tolvéth²,

Stoll³

et al. 1999

J. Appl. Polym. Sci.

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Ensuing our recent studies on polyethylene stabilization, 1,2 further multiple extrusion experiments were carried out with a high-density polyethylene (HDPE) polymer containing various amounts of a sterically hindered phenolic antioxidant. Discoloration, thermoxidative stability, and melt flow index (MFI) retention were measured by standard techniques; the functional group content of the polymer was determined by Fourier transform infrared (FTIR) spectroscopy, and rheological, as well as mechanical properties, were also measured. The results indicated that degradation and stabilization reactions take place according to two different mechanisms in the first and subsequent processing steps, respectively. Color development could be described well by the simple first-order overall reaction kinetics proposed earlier, and color change could be related to the stability of the polymer. The existence of general correlations among the properties proved that all chemical reactions are interrelated. The reactions of the stabilizer lead to color development, while those of the polymer to a modification of its molecular architecture, which determines the rheological and mechanical characteristics of the product.

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“…(2), that is, c 0 exp(ϪkЈ 1 n), and the measured OIT values. 1 It was shown 1 that OIT 0 ϭ 0, showing that the neat polymer has a much lower stability than the stabilized samples.…”

Section: Stabilitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Two-step degradation of high-density polyethylene during multiple extrusion

Epacher

Tolvéth²,

Stoll³

et al. 1999

J. Appl. Polym. Sci.

Self Cite

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“…A number of such transformation products, notably conjugated and nonconjugated quinoidal compounds, have been evaluated for their absorption characteristics in the visible spectrum [1][2][3][4][5][6]. Quinone methides (QM), are the final and oxidation-stable transformation products of mono-and polycyclic phenolic antioxidants that are substituted in positions 2 or 4 to a hydroxyl group with methyl, methylene or methine groups.…”

Section: Introductionmentioning

confidence: 99%

Color inhibition of phenolic antioxidants in Ziegler‐Natta polyethylene. I. In‐situ polymer studies

Allen

Liauw

Reyes

et al. 2009

Vinyl Additive Technology

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Although the level of transition-metal catalyst residues in polyethylene (PE) has been drastically reduced over the years, they can still give rise to discoloration, particularly when associated with other additives such as antioxidants. This first of this series of papers screens a variety of candidate color suppressants featuring a range of functional groups, including alcohols, amine/ sulfur compounds, and acid-containing species. These candidate color suppressants were melt-blended into a Ziegler-Natta linear low-density PE in combination with 2,2 0 -isobutylidenebis(4,6-dimethylphenol) (a highly discoloring hindered bisphenol antioxidant) and zinc stearate antacid. Yellowness index measurements made after multiple extruder passes indicated that dipentaerythritol (DPE) and triisopropylamine (TIPA) gave good color inhibition and, in some cases, outperformed established phosphites. The DPE and TIPA were found (via melt flow rate measurement) not to affect melt stability, and hydroperoxide determination revealed that DPE had no peroxide decomposition activity. The latter results indicate that the color-suppression mechanism of DPE and TIPA is different from that associated with phosphites.

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“…These alkyl radicals react with molecular oxygen forming oxidation products, and new alkyl radicals, which restart the oxidation cycle (Figure 1). In this way, during this cycle, the progressive polymer and polymer weight modifications by chain scission or crosslinking result finally in complete mechanical performance loss 9–13. It should be noted that the failure of the mechanical properties of polyethylene in the course of heat aging is also associated with crack formation on the surface and subsequent crack propagation under mechanical stress 13…”

Section: Introductionmentioning

confidence: 99%

“…In the presence of small amounts of oxygen these radicals cannot recombine, but form peroxy radicals (ROO • ) and hydroperoxides (ROOH). Depending on the polymer these chemical reactions result in molecular weight degradation or increase (branching, cross‐linking), and the plastic becomes unsuitable for its original use 9–12…”

Section: Introductionmentioning

confidence: 99%

Closed Loop Recycling of Bottle Crates Using the Restabilization Technique

Kartalis

Papaspyrides

Pfaendner³

et al. 2003

Macro Materials & Eng

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A remelting‐restabilization technique was applied for the recycling of post‐used, yellow pigmented high density polyethylene (HDPE) bottle crates. In order to evaluate the potential of the recyclate to be used in the original application, the most important parameters were investigated: processing stability, long‐term heat stability and light stability. A multiple extrusion cycles procedure at different reprocessing temperatures was performed for monitoring the processing stability of the restabilized and non‐restabilized material. Oven aging was applied for about 8 800 h (i.e., more than one year) to evaluate the long term thermal stability of the crate material, as manifested by melt flow rate, tensile impact strength, and time until embrittlement measurements. To evaluate the light stability of the recycled material artificial weathering was applied for about 8 000 h, whereas the tensile impact strength was monitored. The latter data were enriched with microphotographs of the specimens surface. Finally, repigmentation was used to investigate the role of new pigments on the final performance of the recycled product. The results illustrate that restabilization is mandatory for the quality improvement of post‐used crates ensuring its re‐use in the original application and thus making closed loop recycling possible.Autoxidation cycle of polymeric materials.magnified imageAutoxidation cycle of polymeric materials.

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Chemical reactions during the processing of stabilized PE: 1. Discolouration and stabilizer consumption

Cited by 25 publications

References 25 publications

Two-step degradation of high-density polyethylene during multiple extrusion

Two-step degradation of high-density polyethylene during multiple extrusion

Color inhibition of phenolic antioxidants in Ziegler‐Natta polyethylene. I. In‐situ polymer studies

Closed Loop Recycling of Bottle Crates Using the Restabilization Technique

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