Role of oxygen diffusion in polymer ageing: kinetic and mechanical aspects

Audouin, L.; Langlois, Valérie; Verdú, J.; Bruijn, J.C.M. de

doi:10.1007/bf00445968

Cited by 263 publications

(130 citation statements)

References 17 publications

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“…For x << 1/A, hydrolysis can be considered as a pseudo-first order process with rate constant k 1 = k u [e] 0 , and the degraded layer thickness h D can be approximated by (33) :…”

Section: Hydrolysis Kineticsmentioning

confidence: 99%

Crosslink Density Changes during the Hydrolysis of Tridimensional Polyesters

Richaud

Pierre

Coquillat

et al. 2014

Macro Theory & Simulations

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. The hydrolysis of almost ideal networks based on macrodiols (poly(adipate of ethylene glycol)) of average molar mass about 2 kg/mol, with L=18 ester groups per chain has been studied. Tensile testing was used to evaluate the crosslink density through the statistical theory of rubber elasticity at two temperatures and three values of relative humidity. A kinetic model for ester consumption including an autocatalysis term was proposed and combined with two original approaches for modeling the crosslink density changes. This allowed kinetic parameters of hydrolysis to be determined, and very good predictions were obtained for the variations of crosslink density (or elastic modulus) in the three aging conditions considered.The initial curvature of elastic modulus vs. time was predicted positive for weak autocatalysis and negative for strong autocatalysis. The obtained conversion ratio at degelation was found to decrease sharply with the number of esters per elastically active chain.

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“…For x << 1/A, hydrolysis can be considered as a pseudo-first order process with rate constant k 1 = k u [e] 0 , and the degraded layer thickness h D can be approximated by (33) :…”

Section: Hydrolysis Kineticsmentioning

confidence: 99%

Crosslink Density Changes during the Hydrolysis of Tridimensional Polyesters

Richaud

Pierre

Coquillat

et al. 2014

Macro Theory & Simulations

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“…As discussed above, the photochemical degradation pathways generally involve multiple steps, crosslinking, and side-reactions; these features make pinpointing the origin of stress-induced rate accelerations difficult. Another formidable complication is that, as discussed in the preceding section, oxygen diffusion is the rate-limiting step in many photo-oxidative degradations (77). This adds to the intricacy of the analysis because oxygen diffusion rates are frequently timedependent (78,79).…”

Section: Effect Of Stressmentioning

confidence: 99%

Photodegradable plastics: end-of-life design principles

Daglen

Tyler

2010

Green Chemistry Letters and Reviews

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Photochemically degradable polymers and plastics are reviewed with an emphasis on the environmental and molecular factors that control the onset of degradation and the rate of degradation. A number of principles are beginning to emerge for the design of viable photochemically degradable plastics. Among the principles discussed are those relating to the effects of chromophores, initiators, antioxidants, temperature, oxygen diffusion into the plastic, polymer crystallinity, tensile and compressive stress, and the absorbed light intensity on the plastic. To obtain a plastic with a controlled lifetime and a specific rate of degradation, many of these parameters can be controlled or adjusted in the design stage of the plastic.

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“…Esta premissa pode ser verdade no caso de filmes finos, onde a degradação é controlada pela cinética de reação e não pela difusão de oxigênio. No caso de peças espessas, como as empregadas neste estudo, a reação de oxidação autocatalítica é controlada por difusão 36 e, na ausência de oxigênio no local de reação, os radicais livres podem se recombinar, interrompendo as reações de propagação. Nestes casos a taxa de difusão de oxigênio deve afetar a foto-degradação.…”

Section: Influência Da Natureza Semi-cristalinaunclassified

“…Como mencionado acima, a foto-degradação do polipropileno em produtos espessos é um processo controlado por difusão 36,41 . Isto implica em uma grande heterogeneidade de degradação ao longo da espessura dos produtos.…”

Section: O Perfil De Degradaçãounclassified

Fotodegradação do polipropileno: Um processo essencialmente heterogêneo

Rabello

White

1997

Polímeros

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Este trabalho analisa alguns aspectos da fotodegradação heterogênea do polipropileno (PP) e compósitos de PP com talco. Amostras moldadas por compressão e por injeção foram expostas à radiação ultravioleta em laboratório por períodos de até 48 semanas. Procedimentos sistemáticos de exposição e coleta de material para análise foram adotados visando-se minimizar as variabilidades inerentes deste estudo. As amostras foram caracterizadas por cromatografia de permeação em gel, espectroscopia de infravermelho, calorimetria diferencial de varredura, difração de raios-X, comportamento mecânico e microscopia ótica e eletrônica. As heterogeneidades na fotodegradação do PP podem estar relacionadas com três principais aspectos: (i) natureza semi-cristalina do polímero; (ii) perfil de degradação; (iii) variações estruturais em diferentes posições nos corpos de prova. As consequências da fotodegradação heterogênea foram discutidas, enfatizando-se os efeitos nas propriedades físicas.

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Role of oxygen diffusion in polymer ageing: kinetic and mechanical aspects

Cited by 263 publications

References 17 publications

Crosslink Density Changes during the Hydrolysis of Tridimensional Polyesters

Crosslink Density Changes during the Hydrolysis of Tridimensional Polyesters

Photodegradable plastics: end-of-life design principles

Fotodegradação do polipropileno: Um processo essencialmente heterogêneo

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