The high temperature secondary crystallisation of aged isotactic polypropylene

Dudić, Duško; Djoković, Vladimir; Kostoski, D.

doi:10.1016/j.polymertesting.2004.01.015

Cited by 28 publications

(16 citation statements)

References 9 publications

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“…A common approach for characterizing aging response in a more practical time frame is to conduct accelerated aging tests at temperatures above the expected service limits. There are already ample reports of physical and chemical changes in polypropylene including secondary crystallization [1][2][3][4] and degradation due to oxidation [5][6][7][8] caused by the thermal aging process.…”

Section: Introductionmentioning

confidence: 99%

“…Most of the reported studies thermally age samples in an oven in air, with [2,7,8] or without ambient light (UV irradiation) [1,[3][4][5][6]8]. The temperature levels studied ranged from sub-freezing to room temperature and up to 1508C for different time periods.…”

Section: Introductionmentioning

confidence: 99%

“…With the expected service temperature limit of 808C, accelerated aging experiments were conducted at 90 and 1408C for 12 days. Although it is known that 1408C causes oxidation [3], this temperature was selected to allow comparison of our results with similar conditions in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Effects of thermal aging on isotactic polypropylene crystallinity

Law

Simon

Lee‐Sullivan

2008

Polymer Engineering & Sci

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The effects of elevated temperature aging on the microstructural changes of isotactic polypropylene matrix in a composite have been studied using wide-angle X-ray scattering (WAXS) and Fourier-transform infrared spectroscopy (FTIR). The objective was to quantify small and slow changes in crystallinity due to thermal aging. To minimize sample variability, polypropylene resin was extracted from the molded composite plaque. Changes in crystallinity level and crystalline form were detected using WAXS after prolonged aging at 90 and 1408C. FTIR was utilized to monitor in-situ crystallinity changes and to detect oxidation products due to thermal decomposition. The level of crystallinity was monitored by changes in the absorbance ratio of A 997 / A 973 and A 841 /A 973 ; the former ratio was found to be more sensitive for detecting crystallinity changes. Aging at 1408C resulted in oxidation. The kinetics of secondary crystallization for the aging conditions studied was characterized using Avrami plots. POLYM. ENG.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of thermal aging on isotactic polypropylene crystallinity

Law

Simon

Lee‐Sullivan

2008

Polymer Engineering & Sci

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“…Two basic parameters were studied: the amplitude of AC conductivity (Y) or AC resistivity (Z) and delay angle ($) (see Figure 2). The amplitudes (Y and Z) and delay angles (for both applied waveforms) were presented for four different values of R and C, but keeping their product constant in Figure 9 for parallel and in Figure 10 for serial RC circuits (RC(1), RC (2), RC (3) and RC(4) are presented in Table 3). As for a sinusoidal signal ( (Figure 9b) are almost inseparable at low frequencies (f << …”

Section: Appendixmentioning

confidence: 99%

“…The most common causes of changes in the properties of polymeric materials are: application of mechanical stress [1]; elevated temperature [2,3]; exposure to electromagnetic radiation of high energy [4,5]; presence of slowly varying electric fields [6]; contact with aggressive chemicals [7]. The changes in polymeric materials resulting from aforementioned factors can be classified into two groups.…”

Section: Introductionmentioning

confidence: 99%

The detection of the early stages of ageing in an LDPE+graphite composite by comparison of dielectric responses induced by sinusoidal and triangular signals

Petronijević¹,

Simonovic²,

Marinković³

et al. 2014

Express Polym. Lett.

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Abstract. This study describes the possibility of dielectric characterization of the initial stages of ageing in an low-density polyethylene (LDPE) + graphite composite, which is not possible using the standard method of dielectric spectroscopy. It is shown that the differences between the delay angles, #$ = $ TRI -%$ SIN , obtained using triangular and sinusoidal excitations on the composite samples, shows a maximum, and at the same time the position of this maximum shows more sensitivity to changes in the electrical properties of the material caused by ageing than other dielectric parameters. In order to clarify the applied methodology, a comparative analysis of the dielectric properties of other polymers poly(vinyl chloride) (PVC) and poly(vinyl alcohol) (PVA) and a conductive polymer composite (LDPE + carbon black) with respect to the application of sinusoidal and triangular electrical signals was carried out. Based on the presented results, we believe that the position of the peak in the frequency spectra of the difference between the delay angles obtained by using triangular and sinusoidal signals may be a suitable parameter for the dielectric characterization of polymeric materials.

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Mechanisms of Physical Aging in Polypropylene

Guero

Vu‐Khanh

2007

Particle and Continuum Aspects of Mesomechanics

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The high temperature secondary crystallisation of aged isotactic polypropylene

Cited by 28 publications

References 9 publications

Effects of thermal aging on isotactic polypropylene crystallinity

Effects of thermal aging on isotactic polypropylene crystallinity

The detection of the early stages of ageing in an LDPE+graphite composite by comparison of dielectric responses induced by sinusoidal and triangular signals

Mechanisms of Physical Aging in Polypropylene

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