Environmental degradation of isotactic polypropylene plates as studied by positron annihilation lifetime spectroscopy

Consolati, G.; Gallo, Raffaele; Quasso, F.; Severini, F.

doi:10.1016/s0032-3861(02)00904-7

Cited by 25 publications

(23 citation statements)

References 13 publications

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“…It could be connected with an increase in crystallinity [19,20]. However, decrease in the volume of the polymer amorphous regions should be also accompanied by decrease in the o-Ps intensity [20,21]. However, in our case the I 3 does not change significantly with the modification time.…”

Section: Discussionmentioning

confidence: 66%

Structural Changes in Surface-Modified Polymers for Medical Applications

Pamuła¹,

Dryzek

2008

Acta Phys. Pol. A

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Biological properties of synthetic polymers can be improved by surface modification with the use of liquid oxidizers. A resorbable biomedical polymer -poly(glycolide-co-ε-caprolactone) (PGCL) was incubated in 0.1 M NaOH for 2, 6, 16, and 24 h, followed by excessive washing and drying in vacuum. Surface properties of the materials before and after modification were evaluated: wettability by contact angle measurements, topography by atomic force microscopy, and chemical functions by infrared spectroscopy. Applied modification improved wettability of PGCL due to creation of chemical oxygenated functionalities, and resulted in a slight alternation of the surface topography and roughness. In order to determine whether NaOH incubation caused structural changes in bulk of PGCL, positron annihilation lifetime spectroscopy, differential scanning calorimetry and viscosity measurements were performed. It was found that the ortho-positronium lifetime in PGCL declines as a function of modification time. It suggests that NaOH incubation causes structural changes in PGCL not only on the surface but also in bulk.

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Section: Discussionmentioning

confidence: 66%

Structural Changes in Surface-Modified Polymers for Medical Applications

Pamuła¹,

Dryzek

2008

Acta Phys. Pol. A

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“…Such a phenomenon accompanied by reduction of the free volume hole size was observed in poly(ethylene terephtalate) as a result of hydrolysis [22] or photodegradation [23]. Nevertheless, in the case of poly(ethylene terephtalate) γ-irradiation [24] or isotactic polypropylene environmental degradation [16], positron lifetime measurements did not show a decrease in the o-Ps lifetime that could explain a reduction of the free volume size. In that case a drop of the o-Ps intensity was well correlated with an increase in crystallinity resulting from a decreased volume of amorphous regions without shrinking the free volume holes.…”

Section: Discussionmentioning

confidence: 87%

“…Changes in the free volume size in polymer structure have been often combined with an increase in crystallinity and decrease in molecular weight [16,[22][23][24]. During the process of polymer degradation, a reduction of molecular weight results in increase in molecular mobility which in turn allows for an easier arrangement of shorter polymer chains in crystalline structures.…”

Section: Discussionmentioning

confidence: 99%

“…permeability and diffusivity) are often correlated with the size of free volumes and free volume fraction [10][11][12][13]. Moreover, PALS was applied to study the structure of different polymers after γ irradiation [14], thermal [15] and outdoor degradation [16], because usually degradation influences the size and distribution of molecular level free volume holes. So far, PALS has not been used to analyze structural changes in aliphatic polyesters caused by hydrolytic degradation.…”

Section: Introductionmentioning

confidence: 99%

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Hydrolytic Degradation of Poly(L-Lactide-co-Glycolide) Studied by Positron Annihilation Lifetime Spectroscopy and Other Techniques

2006

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Changes of the poly(L-lactide-co-glycolide) structure as a function of degradation time in phosphate-buffered saline for 7 weeks were investigated by gel permeation chromatography, differential scanning calorimetry, nuclear magnetic resonance ( 1 H NMR), and positron annihilation lifetime spectroscopy. Surface properties as wettability by sessile drop and topography by atomic force microscopy were also characterized. Chain-scission of polyester bonds in hydrolysis reaction causes a quite uniform decrease in molecular weight, and finally results in an increase in semicrystallinity. Molecular composition of the copolymer and water contact angle do not change considerably during degradation time. Atomic force microscopy studies suggest that the copolymer degrades by "in bulk" mechanism. The average size of the molecular-level free volume holes declines considerably after one week of degradation and remains constant till the sixth week of degradation. The free volume fraction decreases as a function of degradation time.

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“…Therefore, PALS technique has been applied to investigate the free volume property of polymer materials after ageing for many years [14][15][16][17][18][19]. L. Brambilla et al [20] and R. Gallo et al [21] studied outdoor degradation of isotactic PP plates and ethylene-propylene copolymer sheets by PALS, respectively. They suggested that the more ordered disposal of molecules decreases the volume of the amorphous regions but the free volume sizes distribution does not display significant size variations with the weathering.…”

Section: Introductionmentioning

confidence: 99%

Microstructure studies of isotactic polypropylene under natural weathering by positron annihilation lifetime spectroscopy

Zhu

Liao

et al. 2015

J Polym Res

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The microstructure evolution of isotactic polypropylene (PP) exposed to subtropical humid climate of Guangzhou of China, were investigated by gel permeation chromatography, Fourier transform infrared spectroscopy, differential scanning calorimeter, dynamic mechanical analysis and positron annihilation lifetime spectroscopy. Positron data showed that the free volume of PP matrix decreased with involving a shrinking of the free volume hole sizes as the extent of weathering degradation of PP aggravated. The shrinkage of free volume hole sizes may be traced to the loss of mobility of molecules of PP matrix. The increase of the glass transition temperature substantiated undoubtedly the decrease of molecular mobility of PP chains. The increase in crystallinity might increase the amount of rigid amorphous fraction of PP matrix, which induced the loss of molecular mobility. Furthermore, the decrease of orthopositronium formation ought to be correlated to the increase in crystallinity and the increasing amount of scavenchers which were in this work represented by the carbonyl groups.

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Environmental degradation of isotactic polypropylene plates as studied by positron annihilation lifetime spectroscopy

Cited by 25 publications

References 13 publications

Structural Changes in Surface-Modified Polymers for Medical Applications

Structural Changes in Surface-Modified Polymers for Medical Applications

Hydrolytic Degradation of Poly(L-Lactide-co-Glycolide) Studied by Positron Annihilation Lifetime Spectroscopy and Other Techniques

Microstructure studies of isotactic polypropylene under natural weathering by positron annihilation lifetime spectroscopy

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