Influence of low extents of degradation on the processing behaviour of high density polyethylene

Mantia, Francesco Paolo La; Città, V.; Valenza, A.; Roccasalvo, S.

doi:10.1016/0141-3910(89)90082-7

Cited by 19 publications

(7 citation statements)

References 8 publications

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“…For the lower shear rate 0.01 s À1 , where the viscosity is related to the microstructure of material, the viscosity of neat HDPE decreases from 33.8 Â 10 3 to 24.5 Â 10 3 Pa.s after five extrusions. This degradation can be explained by the decrease in molecular weight which is due to the scission of chains 4,5,18 with the number of extrusions as confirmed by DSC results.…”

Section: Rheological Resultsmentioning

confidence: 62%

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Recycling effect on mechanical behavior of HDPE/glass fibers at low concentrations

Ayadi

Kraiem

Bradaï

et al. 2011

Journal of Thermoplastic Composite Materials

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The present article investigates the recycling effect on properties of dilute suspension of HDPE reinforced by SGF without coupling agents. This dilute suspension at different proportions of SGF loading was produced by melt compounding cycles with a single screw extruder. The differential scanning calorimetry results have shown an increase in the crystallinity of HDPE with SGF proportion and the number of extrusions. The increase varies from 8.2% for neat HDPE 5 extrusions to 13.3% for HDPE 10% SGF 3 extrusions. Besides, rheological measurements have shown a decrease in the viscosity of neat matrix from 33,800 Pa.s to 24,500 Pa.s after 5 extrusions for 0.01 s À1 , while the opposite is observed for composites for which the highest viscosity is obtained with five cycles of extrusion. These results suggest a decrease in the molecular weight of the HDPE during reprocessing, but for composites a good dispersion of SGF matrix was obtained, increasing with the extrusion number. As for the mechanical properties, a substantial enhancement in ductility was observed, compared to neat recycled matrix, by adding small SGF concentrations. Thus, for 1.6% and 2.6% SGF the best enhancement of ductility was obtained with conservation of the fiber length and a good dispersion of fibers.

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Section: Rheological Resultsmentioning

confidence: 62%

“…However, the extent of thermal degradation and the properties of the recycled material are strongly dependent on the HDPE structure and processing conditions. 3,4 La Mantia et al 4 and Loultcheva et al 5 have shown that the HDPE polymer undergoes a little degradation after several reprocessing cycles in a single screw extruder.…”

Section: Introductionmentioning

confidence: 99%

Recycling effect on mechanical behavior of HDPE/glass fibers at low concentrations

Ayadi

Kraiem

Bradaï

et al. 2011

Journal of Thermoplastic Composite Materials

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“…The experimental data were analyzed in the framework of the molecular stress function (MSF) model for polydisperse branched polymer melts. To the best of our knowledge, there exists only one earlier report on enhanced strain hardening due to formation of branched molecules by thermo-mechanical degradation [La Mantia et al (1989)], but this concerns high density polyethylene.…”

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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“…The degradation behavior is also not identical in one polymer group, but depends on the polymer chain length, branching, possible crosslinking, blending, additives and stabilization of the plastic. [1,10,[40][41][42][43][44][45] Therefore, the degradation behavior of each plastic must be considered and investigated individually. With the method described, however, a plastic can be measured within one day's effort.…”

Section: Resultsmentioning

confidence: 99%

Measurement of material degradation in dependence of shear rate, temperature, and residence time

Schall

Schöppner

2022

Polymer Engineering & Sci

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During processing, plastics are frequently exposed to high stresses. These include, above all, shear and temperature within the scope of the residence time of the manufacturing process in order to achieve a homogeneous plastic melt for further processing. The stress of the manufacturing process can lead to molecular degradation, which can have a negative effect on the product properties. Since it makes sense to take molecular degradation into account for many processes, a test stand for material characterization was designed and a regression equation was derived for the mathematical description of the degradation behavior. With the help of this regression equation, a prediction of the expected material degradation can be made, provided that the shear rate, the temperature and the associated residence time are known.

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Influence of low extents of degradation on the processing behaviour of high density polyethylene

Cited by 19 publications

References 8 publications

Recycling effect on mechanical behavior of HDPE/glass fibers at low concentrations

Recycling effect on mechanical behavior of HDPE/glass fibers at low concentrations

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

Measurement of material degradation in dependence of shear rate, temperature, and residence time

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