Free volume and glass transition in ethylene/1-octene copolymers: positron lifetime studies and dynamic mechanical analysis

Kilburn, Duncan; Bamford, David; Lüpke, T.; Dlubek, G.; Menke, Tammo J.; Alam, M. A.

doi:10.1016/s0032-3861(02)00663-8

Cited by 49 publications

(61 citation statements)

References 63 publications

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“…As to pure POE, despite a broad halo at 2y % 19.58 attributed to the amorphous phase, two peaks (2y ¼ 20.88 and 2y ¼ 23.14 , respectively) coming from the (110) and (200) these reflections in the case of linear polyethylene, having the unit cell dimensions a ¼ 0.741 nm, b ¼ 0.494 nm, and c ¼ 0.255 nm. [27][28][29] In case of the POEg-MAH copolymers, the y 110 and y 200 peaks decrease in their intensity with increasing GD and disappear almost completely at a GD of 9.87%, which indicates that imperfection (paracrystalline distortion, size of crystallites, and lattice defects 30,31 ) of the crystalline phase increased with the increase of GD. It can also be seen from Figure 5 that the peak in the d amorphous , d 110 , and d 200 values increase with the rising GD, indicating the loose packing of the molecular chains in the orthorhombic unit cell.…”

Section: X-ray Analysesmentioning

confidence: 97%

Properties of poly(ethylene 1‐octene)‐g‐maleic anhydride copolymers prepared via solvothermal process

Liu

Wang

et al. 2008

J of Applied Polymer Sci

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The poly(ethylene 1-octene)-g-maleic anhydride copolymers (POE-g-MAH) with high grafting degree (GD) (>9%) have previously been obtained by a solvothermal method in our laboratory. It is found that the low GD (less than 2.5%) did not change the bulk properties of polyolefine elastomers (POE). Thereforefore, it is worth further understanding whether a high GD POE-g-MAH copolymer differs from the pure POE in its comprehensive properties and performance. In this article, POE-g-MAH with different GDs were synthesized and characterized by thermogravimetric analyze (TGA), differential scanning calorimetry (DSC), wide angle X-ray diffraction spectroscopy (WAXD), and dynamic rheological testing. The results show that the thermal decomposition temperature, melting points, the crystallization temperatures, and the crystallinities were decreased by the increasing GD. By WAXD, three peaks respectively, attributed to the amorphous phase, the (110) and (200) interferences of the orthorhombic unit cell were detected, and they also decreased by the increasing GD. And the POE-g-MAH copolymers had higher storage modulus (G 0 ), loss modulus (G 00 ), and complex viscosity (g*) than those of pure POE.

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Section: X-ray Analysesmentioning

confidence: 97%

Properties of poly(ethylene 1‐octene)‐g‐maleic anhydride copolymers prepared via solvothermal process

Liu

Wang

et al. 2008

J of Applied Polymer Sci

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“…The slight increase of the o-Ps hole volume, V h , with temperature below T g reflects the thermal expansion of the glass due to the anharmonicity of molecular vibrations and possibly local motion. During the transition through T g , the structural disorder within a polymer changes its character from static to a dynamic one with increasing segmental motion that result in a distinct increase of the hole size with increasing temperature [11]. The increase in the chain mobility with increasing temperature is associated with an increase in the mean local volume.…”

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confidence: 99%

Temperature dependence of the free volume holes in polyhydroxybutyrate biopolymer: A positron lifetime study

Abdel-Hady

Hamed

Fareed

2007

Phys. Status Solidi (c)

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The size of the free volume holes and their distributuion in polyhydroxybutyrate (PHB) biopolymer have been studied using positron annihilation lifetime spectroscopy (PALS). The measurements were performed as a function of the temperature from 243 to 363 K. The temperature dependence of the free volume hole shows a glass transition temperature, T g at 278 K. The free volume behaviour of PHB shows a small linear increase with temperature below T g and a steeper increase above T g . The thermal expansion coefficients of the free volume hole were determined to be 4.78 x 10 -3 and 12.5 x 10 -3 / K below and above T g , respectively. The free volume hole distribution shows a narrow distribution below T g . With increasing temperature, the maximum of the distributions of the free volume holes shifts to higher values. Meanwhile, widening of the distribution is smaller in lower temperature ranges and more pronounced at higher temperatures, especially above T g .1 Introduction Polymers contain local free volumes, these are cavities or holes of atomic and molecular dimensions that arise because of (1) irregular molecular packing in the amorphous phase (static and pre-existing holes) and (2) molecular relaxation of the polymer chains and terminal ends (dynamic and transient holes). Positron annihilation lifetime spectroscopy (PALS) has recently emerged as a unique nano-probe capable of measuring the free volume hole sizes in polymers [1][2][3][4]. When positrons are injected into materials, they lose their kinetic energy within a few picoseconds. After thermalization, a positron diffuses in the media, and annihilates with an electron from the surrounding emmiting two γ-rays. In polymers, a positron might annihilate from a positronium (Ps) state, a bound state of a positron and electron. A positronium has two spin states: a singlet state (para-Ps, p-Ps) and a triplet state (orthoPs, o-Ps).The most important component is the o-Ps lifetime, τ oPs which gives us information about the free volume holes in which annihilation of positrons takes place.Nowadays plastics and synthetic polymers are mainly produced using petrochemical materials that cannot be decomposed. Therefore they contribute to environmental pollution and are a danger to many animals. During the last decade, much attention has been focused on the production of bacterial polyesters. Different bacterial types [5] of microorganisms produce polyhydroxybutyrate (PHB) from renewable sources such as sugar and molasses as intracellular storage materials. The possible applications of PHB are in medicine, in pharmacology and in packaging for deep drawing articles in the food industry.Only one measurement was reported in the study of the properties of the free volume in PHB biopolymer [6]. The aim of this work is to invesigate the potential of PALS for studying the free volume properties of semicrystalline PHB bioolymer. This can be achieved via a systematic study of the temperature dependence of the mean size of local free volumes and their distributions.

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“…13,15,20 The leveling off of the o-Ps lifetime at the highest temperatures has been a subject of considerable debate. 1,6,12,17,[24][25][26] One suggestion has been that the leveling off is due to the increased amplitude of the molecular fluctuations, which results in an increased average overlap of the o-Ps with the electrons of the surrounding molecules and hence counteracts the effect of increasing free volume sizes with temperature. Another suggestion has been that the leveling off is due to the formation of equilibrium 'Ps bubbles', similar to Ps-bubbles in ordinary liquids.…”

Section: Introductionmentioning

confidence: 99%

Free volume dilatation in polymers by ortho-positronium

Winberg

Eldrup

Maurer

2012

The Journal of Chemical Physics

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The possibility of positronium induced free volume cavity expansion in some polymers above the glass transition temperature was investigated using experimental positron annihilation lifetime data from the literature for polydimethylsiloxane, polyisobutylene, and polybutadiene as function of temperature. The results suggest that free volume sites can expand towards an equilibrium size, determined as the equilibrium Ps-bubble size defined earlier for low-molecular-weight liquids. The expansion can be explained by the increase of molecular mobility and hence decrease of relaxation times, which at the higher temperatures approach the o-Ps lifetimes. Nanoscale viscosities were estimated using Navier-Stokes equation and were found to be several orders of magnitude lower than the macroscopic viscosity at the same temperature.

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Free volume and glass transition in ethylene/1-octene copolymers: positron lifetime studies and dynamic mechanical analysis

Cited by 49 publications

References 63 publications

Properties of poly(ethylene 1‐octene)‐g‐maleic anhydride copolymers prepared via solvothermal process

Properties of poly(ethylene 1‐octene)‐g‐maleic anhydride copolymers prepared via solvothermal process

Temperature dependence of the free volume holes in polyhydroxybutyrate biopolymer: A positron lifetime study

Free volume dilatation in polymers by ortho-positronium

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