Kinetics and Mechanism of the Oxidation of Stressed Polymer

Rapoport, Natalya; Заиков, Г. Е.

doi:10.1007/978-94-009-4940-9_7

Cited by 16 publications

(4 citation statements)

References 29 publications

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“…Such changes could affect the chemical kinetics of polymer oxidation at all stages in various ways [52]. For elastomers such as PEUs, externally applied stress causes conformational rearrangements in the flexible polyether chains, followed by disruption in the hard segment domains, causing internal entropy stresses.…”

Section: Article In Pressmentioning

confidence: 99%

Analysis and evaluation of a biomedical polycarbonate urethane tested in an in vitro study and an ovine arthroplasty model. Part I: materials selection and evaluation

et al. 2005

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Section: Article In Pressmentioning

confidence: 99%

Analysis and evaluation of a biomedical polycarbonate urethane tested in an in vitro study and an ovine arthroplasty model. Part I: materials selection and evaluation

et al. 2005

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“…In crystallising polymers, chain scission releases molecular segments that were immobilised by entanglements and allows secondary crystallisation in a manner that can be even more pronounced than that discussed in Section 2. In this case the secondary crystallisation is often referred to as 'chemi-crystallisation' [88][89][90] or sometimes 'oxidative crystallisation' [91]. Crystallinity changes caused by photo-ageing a polypropylene copolymer are given in Fig.…”

Section: Weatheringmentioning

confidence: 99%

Polymer ageing: physics, chemistry or engineering? Time to reflect

White

2006

Comptes Rendus. Chimie

183

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Polymer ageing may involve physical ageing without chemical reaction occurring; chemical changes such as crosslinking during curing of a thermoset; thermal conditioning at elevated temperature; photochemical ageing, as occurs in weathering. This review concentrates on examples involving a combination of two or more of these effects, and with the consequential changes in engineering properties. Events on the molecular level lead to change in the morphology and macroscopic physical properties. For example, in a semi-crystalline polymer, chain scission caused by photo-oxidation, may lead to secondary crystallisation ('chemi-crystallisation'), increasing density, and causing an increase in Young's modulus and reducing ductility. Similar effects may be observed in glassy polymers, due to chain scission accelerating physical ageing. Such effects are particularly common when rapid cooling during moulding has left the polymer in a state far from equilibrium. A common symptom is a change in the residual stress distribution in polymer mouldings and this is discussed.

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“…In a series of previous works [86,92], the authors have reported that the stressed and elongated polymer chains are oxidized at the highest rate than the non-stressed ones. In the former case, the attack by ozone molecules impacts reactive polymeric centers (the ester functional groups) belonging to (a) the polymer loops that are suspended on the border between amorphous and crystalline phases, (b) the transitional polymer chains packed in the intercrystalline space, and (c) the polymer network formed by hydrogen bonds and covalent bridges at the participation of the new oxygen-contained functional groups having arisen due to ozonolysis.…”

Section: The Impact Of Ozonolysis On the Dynamics Of Radical Rotation...mentioning

confidence: 99%

Biocomposites Based on Electrospun Fibers of Poly(3-hydroxybutyrate) and Nanoplatelets of Graphene Oxide: Thermal Characteristics and Segmental Dynamics at Hydrothermal and Ozonation Impact

Karpova,

Olkhov,

Varyan

et al. 2023

Polymers

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In order to create new biodegradable nanocomposites for biomedicine, packaging, and environmentally effective adsorbents, ultra-thin composite fibers consisting of poly(3-hydroxybutyrate) (PHB) and graphene oxide (GO) were obtained by electrospinning. Comprehensive studies of ultrathin fibers combining thermal characteristics, dynamic electron paramagnetic resonance (ESR) probe measurements, and scanning electron microscopy (SEM) were carried out. It is shown that at the addition of 0.05, 0.1, 0.3, and 1% OG, the morphology and geometry of the fibers and their thermal and dynamic characteristics depend on the composite content. The features of the crystalline and amorphous structure of the PHB fibers were investigated by the ESR and DSC methods. For all compositions of PHB/GO, a nonlinear dependence of the correlation time of molecular mobility TEMPO probe (τ) and enthalpy of biopolyether melting (ΔH) is observed. The influence of external factors on the structural-dynamic properties of the composite fiber, such as hydrothermal exposure of samples in aqueous medium at 70 °C and ozonolysis, leads to extreme dependencies of τ and ΔH, which reflect two processes affecting the structure in opposite ways. The plasticizing effect of water leads to thermal destruction of the orientation of the pass-through chains in the amorphous regions of PHB and a subsequent decrease in the crystalline phase, and the aggregation of GO nanoplates into associates, reducing the number of GO-macromolecule contacts, thus increasing segmental mobility, as confirmed by decreasing τ values. The obtained PHB/GO fibrillar composites should find application in the future for the creation of new therapeutic and packaging systems with improved biocompatibility and high-barrier properties.

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Kinetics and Mechanism of the Oxidation of Stressed Polymer

Cited by 16 publications

References 29 publications

Analysis and evaluation of a biomedical polycarbonate urethane tested in an in vitro study and an ovine arthroplasty model. Part I: materials selection and evaluation

Analysis and evaluation of a biomedical polycarbonate urethane tested in an in vitro study and an ovine arthroplasty model. Part I: materials selection and evaluation

Polymer ageing: physics, chemistry or engineering? Time to reflect

Biocomposites Based on Electrospun Fibers of Poly(3-hydroxybutyrate) and Nanoplatelets of Graphene Oxide: Thermal Characteristics and Segmental Dynamics at Hydrothermal and Ozonation Impact

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