Polymer Degradation

Rizzarelli, Paola; Carroccio, Sabrina; Puglisi, Concetto

doi:10.1002/9783527641826.ch13

Cited by 3 publications

(6 citation statements)

References 78 publications

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“…The PA during thermal annealing at the melt state was a system with considerable complexity. Several reactions or changes have been reported correspondingly, such as cross-linking, gelation, and degradation. − The mechanism of cross-linking and gelation in PA 66 has been thoroughly discussed, and it is ascribed to the decarboxylation and dehydration of adipic acid and the formation of cyclopentanone. ,− As for PA 12, Stamhuis et al reported that annealing at the melt state under pressure leads to cross-linking. Cross-linking among macromolecules resulted in the change in chain structure which can be detected by FTIR and might also lead to the reduction of crystallinity and the increase in molecular weight.…”

Section: Resultsmentioning

confidence: 99%

“…The degradation modes include three main pathways: depolymerization, removal of side groups, and random chain scission, each with its own characteristics . Depolymerization is a reverse process of polymerization, creating monomers during degradation . The side group removal always occurs in macromolecules with the active side group and usually generates small molecules .…”

Section: Resultsmentioning

confidence: 99%

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Cell Structure Variation in Poly(ether-mb-amide) Copolymer Foams Induced by Chemi-Crystallization

Cao

Pang

Dong

et al. 2020

Ind. Eng. Chem. Res.

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The objective of this study was to clarify the cell structure variation of the poly(ether-mb-amide) (PEBA) copolymer with the chemi-crystallization induced via thermal treatment at the melt state. Thermal annealing was conducted using a compression molding machine at the melt state for various times (i.e., 3, 30, 60, 120, and 300 min) to promote chemi-crystallization. The chemical structure change was studied with Fourier transform infrared spectra, and the viscosity change was investigated using a rheometer. The crystallization behavior was studied with differential scanning calorimetry and X-ray diffraction. The PEBA samples were foamed using a two-step batch foaming process, and the cell structure was investigated with a scanning electron microscope. It was found that the chemical structure of PEBA was hardly changed during the thermal treatment, while the complex viscosity was decreased. It was speculated that degradation occurred probably via a random chain scission mode. Thus, the chemicrystallization was promoted for the crystalline segments because of the less suppression from the noncrystalline segments ascribed to the shorter chains. Consequently, three types of cell structures were observed in PEBA: uniform cell structure, bimodal cell structure, and micro/nanosized cells formed within the spherulites. A scheme was presented to interpret the relationship between the cell structure variation and the crystalline states in PEBA samples. The amorphous, partially melted, and unmelted regions were classified during foaming to interpret the formation of the three types of cell structures.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Cell Structure Variation in Poly(ether-mb-amide) Copolymer Foams Induced by Chemi-Crystallization

Cao

Pang

Dong

et al. 2020

Ind. Eng. Chem. Res.

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“…Remarkably, this scission mechanism is the same involved in the first stage of PA11 thermo-oxidation pathway a 215 • C, but in this case cross-linking phenomena triggered by organo-modified nanoparticles took place [24]. As indicated in the literature [36], the acceleration of such reaction is due to Hofmann elimination of quaternary ammonium salts occurring at temperature above 180 • C [35]. The produced α-olefins and aldehydes participate to the acceleration of the thermal-oxidation process, boosting up the insoluble gel formation [4,24].…”

Section: Maldi-tof Analysesmentioning

confidence: 68%

“…As evidenced also for other polymer matrices included PAs, degradation starts out with α-H abstraction mechanism as detected by MALDI analysis [30,31]. At prolonged exposure times, NORRISH I and NORRISH II photo cleavages turn out to be active, further promoting chain scission with the formation of peculiar end groups detectable from MS analysis [30,31,35].…”

Section: Introductionmentioning

confidence: 74%

“…Conversely, photo-exposure process performed at 60 • C was not able neither to induce gel formation or to trigger Hofmann elimination. As far as this point is concerned, it is reasonable to suppose that the acceleration of the photo-oxidation process is driven by the iron impurities into nanoclay structures [2,14,35], whose presence was confirmed by ICP-MS analyses (see Table 2). Further proof of the key role of iron impurities comes from the analysis of the MMT-based samples, which exhibit the same trend as the Cloisite ® 30B-filled samples sharing comparable iron content.…”

Section: Maldi-tof Analysesmentioning

confidence: 93%

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Role of Organo-Modifier and Metal Impurities of Commercial Nanoclays in the Photo- and Thermo-Oxidation of Polyamide 11 Nanocomposites

et al. 2020

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The photo-oxidative degradation processes of bio-based PA11 nanocomposites containing montmorillonite (MMT) and the organo-modified Cloisite®30B were investigated to discriminate the influence of organo-modified components on the polymer durability. Indeed, despite the extensive studies reported, there are still ambiguous points to be clarified from the chemical point of view. To this aim, UV-aged materials were analyzed by Size Exclusion Chromatography (SEC), Inductively Coupled Plasma–Mass Spectrometry (ICP-MS) and Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS). This enabled determining changes in both chemical structure and Molar Masses (MMs) induced by light, heat and oxygen exposure. The addition of organo-modified nanoclays strongly affected the PA11 light durability, triggering the macromolecular chains scission due to the typical αH, Norrish I and II mechanisms. However, the main contribution in boosting the photo-oxidative degradation is induced by iron impurities contained into the clays. Conversely, thermo-oxidation process performed at 215 °C was unambiguously affected by the presence of the organo-modifiers, whose presence determined an enhancement of crosslinking reactions.

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Mass spectrometry in bioresorbable polymer development, degradation and drug‐release tracking

Rizzarelli

Rapisarda

Valenti

2020

Rapid Comm Mass Spectrometry

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A detailed characterization of polymeric matrices and appropriate degradation monitoring techniques are required to sustain the development of new materials as well as to enlarge the applications of the old ones. In fact, polymer analysis is essential for the clarification of the intrinsic relationship between structure and properties that ascertains the industrial applications in diverse fields. In bioresorbable and biodegradable polymers, the role of analytical methods is dual since it is pointed both at the polymeric matrices and at degradation tracking. The structural architectures, the mechanical and morphological properties, and the degradation rate, are of outstanding importance for a specific application. In some cases, the complexity of the polymer structure, the processes of decomposition or the low concentration of the degradation products need the concurrent use of different complementary analytical techniques to give detailed information of the reactions taking place. Several analytical methods are used in bioresorbable polymer development and degradation tracking. Among them, mass spectrometry (MS) plays an essential role and it is used to refine polymer syntheses, for its high sensitivity, to highlight degradation mechanism by detecting compounds present in trace amounts, or to track the degradation product profile and to study drug release. In fact, elucidation of reaction mechanisms and polymer structure, attesting to the purity and detecting defects as well as residual catalysts, in biodegradable and bioresorbable polymers, requires sensitive analytical characterization methods that are essential in providing an assurance of safety, efficacy and quality. This review aims to provide an overview of the MS strategies used to support research and development of resorbable polymers as well as to investigate their degradation mechanisms. It is focused on the most significant studies concerning synthetic bioresorbable matrices (polylactide, polyglycolide and their copolymers, polyhydroxybutyrate, etc.), published in the last ten years.

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Polymer Degradation

Cited by 3 publications

References 78 publications

Cell Structure Variation in Poly(ether-mb-amide) Copolymer Foams Induced by Chemi-Crystallization

Cell Structure Variation in Poly(ether-mb-amide) Copolymer Foams Induced by Chemi-Crystallization

Role of Organo-Modifier and Metal Impurities of Commercial Nanoclays in the Photo- and Thermo-Oxidation of Polyamide 11 Nanocomposites

Mass spectrometry in bioresorbable polymer development, degradation and drug‐release tracking

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