The effect of thermal and thermo-oxidative degradation conditions on rheological, chemical and thermal properties of HDPE

Cuadri, A.A.; Martín‐Alfonso, J.E.

doi:10.1016/j.polymdegradstab.2017.05.005

Cited by 64 publications

(48 citation statements)

References 43 publications

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“…In this latter case, rheology measurements or differential scanning calorimetry (DSC) are suitable methods for detecting the effects of degradation. In the case of DSC, the effects are shown on melting and crystallisation, mainly by a delay in crystallisation and in the dimensions of obtained crystal structures [47]. However, in a previous work it was affirmed that for PEEK, DSC is not sensitive enough for characterising the first stages of degradation [46].…”

Section: Resultsmentioning

confidence: 96%

“…However, in a previous work it was affirmed that for PEEK, DSC is not sensitive enough for characterising the first stages of degradation [46]. On the other hand, rheological properties, such as complex viscosity, are quite sensitive to chain modifications (scission, branching, cross-linking) and are suitable parameters for monitoring thermal degradation [47][48][49].…”

Section: Resultsmentioning

confidence: 99%

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On the determination of thermal degradation effects and detection techniques for thermoplastic composites obtained by automatic lamination

Martı́n

Rodriguez-Lence

Güemes

et al. 2018

Composites Part A: Applied Science and Manufacturing

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Automatic lay-up and in-situ consolidation with thermoplastic composite materials is a technology under research for its expected use in the profitable manufacturing of structural aeronautical parts. This study is devoted to analysing the possible effects of thermal degradation produced by this manufacturing technique. Rheological measurements showed that there is negligible degradation in PEEK for the temperatures reached during the process. Thermogravimetric analysis under linear heating and constant rate conditions show that thermal degradation is a complex process with a number of overlapping steps. A general kinetic equation that describes the degradation of the material with temperature has been proposed and validated. Attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed that there is no remarkable degradation. The use of a combination of in-situ and ex-situ experimental techniques, including kinetic modelling, not only provides reliable information about degradation but also allows setting optimal processing conditions.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

On the determination of thermal degradation effects and detection techniques for thermoplastic composites obtained by automatic lamination

Martı́n

Rodriguez-Lence

Güemes

et al. 2018

Composites Part A: Applied Science and Manufacturing

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“…Some studies have suggested that oxygen increases the onset of PP and PE degradation. [34][35][36] However, it is important to note that these studies were performed at high temperatures using DSC and TGA, which essentially detects initiation of pyrolysis, rather than oxidative propagation. Oxygen diffusion in polymers is slow and it has thus been argued that most degradation actually occurs under inert conditions.…”

Section: Role Of Oxygenmentioning

confidence: 99%

The Fate of the Peroxyl Radical in Autoxidation: How Does Polymer Degradation Really Occur?

2018

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Bolland and Gee's basic autoxidation scheme (BAS) for lipids and rubbers has long been accepted as a general scheme for the autoxidation of all polymers. This scheme describes a chain process of initiation, propagation, and termination to describe the degradation of polymers in the presence of O. Central to this scheme is the conjecture that propagation of damage to the next polymer chain occurs via hydrogen atom transfer with a peroxyl radical. However, this reaction is strongly thermodynamically disfavored for all but unsaturated polymers, where the product allylic radical is resonance-stabilized. Paradoxically, there is no denying that the autocatalytic degradation and oxidation of saturated polymers still occurs. Critical analysis of the literature, described herein, has begun to unravel this mystery. One possibility is that the BAS still holds for saturated polymers but only at unsaturated defect sites, where H transfer is thermodynamically favorable. Another is that peroxyl termination rather than H transfer is dominant. If this were the case, tertiary peroxyl radicals (formed at quaternary centers or quaternary branching defects) may terminate to form alkoxy radicals, which can much more readily undergo chain transfer. This process would lead to the creation of hydroxy groups on the degraded polymer. On the other hand, primary and secondary peroxyl radicals would terminate to form nonradical products and halt further degradation. As a result, under this scenario the degree of branching and substitution would have a major effect on polymer stability. Herein we survey studies of polymer degradation products and of the effect of polymer structure on stability and show that indeed peroxyl termination is competitive with peroxyl transfer and possibly dominant under some conditions. It is also feasible that oxygen may not be the only reactive atmospheric species involved in catalyzing polymer degradation. Herein we outline plausible mechanisms involving ozone, hydroperoxyl radical, and hydroxyl radical that have all been suggested in the literature and can account for the experimentally observed formation of hydroperoxides without invoking peroxyl transfer. We also show that oxygen itself has even been reported to slow the degradation of poly(methyl methacrylate)s, which might be expected if peroxyl radicals are unreactive toward hydrogen transfer. Discrepancies between the rate of oxidation and the rate of degradation have been observed for polyolefins and also support the counterintuitive notion that oxygen stabilizes these polymers against degradation. We show that together these studies support alternative mechanisms for polymer degradation. A thorough assessment of kinetic studies reported in the literature indicates that they are limited by their propensity to use models based on the BAS, disregarding the chemical differences intrinsic to each class of polymer. Thus, we propose that further work must be done to fully grasp the complex mechanism of polymer degradation under ambient conditions. Nonetheless, ...

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“…Addition of Sio 2 nanoparticles in PP influences tensile strength, tensile toughness and impact strength of PP/Sio 2 nanocomposites [5]. Thermal and thermooxidative degradation conditions shift the characteristic temperature to lower values when exposed to different temperatures at different time periods [6]. Thermal cracking of HDPE has been investigated in the presence of solvents with different hydrogen-donating capabilities by D. P. Serrano et al [7], The presence of wood powder in PP/HDPE, and MAPP/HDPE thermoplastic polymers increases the thermal stability and stiffness of the composites but adversely tensile strength decrease with wood powder content [8].…”

Section: Introductionmentioning

confidence: 99%

Effect of Thermal Aging on Mechanical Properties and Fatigue Behavior of PP/HDPE Thermoplastic Polymer Nanoclay Composites

Pydi¹,

Tjprc²

2018

IJMPERD

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Thermoplastic polymers are gaining their importance in their usage and emerging into industrial applications. Material degradation and loss of its properties due to exposure to different environmental conditions restrict their usage in engineering applications. The inclusion of nanofillers in these polymers can enable their usage in engineering application by reducing the degradation of the material. In the present study two thermoplastic polymers, Polypropylene (PP) and High-Density Polyethylene (HDPE) are considered for fabrication of nanoclay included thermoplastic polymer clay nanocomposites by melt blend method. These composites are exposed to the higher temperature to study the effect of thermal aging on mechanical and fatigue properties of nanoclay included PP/HDPE thermoplastic polymer nanocomposites. Nanoclay inclusion reduces the decrease in these properties due to thermal aging.

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The effect of thermal and thermo-oxidative degradation conditions on rheological, chemical and thermal properties of HDPE

Cited by 64 publications

References 43 publications

On the determination of thermal degradation effects and detection techniques for thermoplastic composites obtained by automatic lamination

On the determination of thermal degradation effects and detection techniques for thermoplastic composites obtained by automatic lamination

The Fate of the Peroxyl Radical in Autoxidation: How Does Polymer Degradation Really Occur?

Effect of Thermal Aging on Mechanical Properties and Fatigue Behavior of PP/HDPE Thermoplastic Polymer Nanoclay Composites

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