Effects of High Energy Radiation on Polymers II. End-linking and Gel Fraction

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. AbstractThe thermo-oxidative degradation of polylactide (PLA) films was studied between 70 and 150°C. It was shown that the oxidative degradation of PLA leads to a random chain scission responsible for a reduction of the molar mass. These molar mass changes affect Tg and the degree of crystalllinity, and it was found that Tg decreases according to the Fox-Flory theory whereas the degree of crystalllinity increases due to a chemicrystallization process. A correlation between molar mass and strain at break during oxidation has been established:PLA displays a brittle behaviour when M n falls below 40 kg.mol -1 in agreement with relationships linking the critical value for embrittlement with the molar mass between entanglements.

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“…According to Saito [27], the number of chain scissions, s, given in mol/kg, can be expressed by the following equation:…”

Section: ) Ageing Conditionsmentioning

confidence: 99%

Oxidative degradation of polylactide (PLA) and its effects on physical and mechanical properties

Rasselet¹,

Ruellan²,

Guinault³

et al. 2014

European Polymer Journal

136

102

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“…Besides chain length, there are no differences in the chemical structures of the polymers, indicating that the efficiency of cross-linking should be identical for all series of polymers to a first approximation. The effects of the molecular weight distribution on the radiation-induced gelation of a real polymer system were considered by Saito 83 and Inokuti, 84 who traced the changes in distribution due to simultaneous reactions of main-chain scission and cross-linking analytically. However, in the present case, the molecular weight distributions of the target polymers are reasonably well controlled to be less than 1.2, and the initial distributions are predicted not to play a major role in gelation.…”

Section: Intrinsic Mobility Of Charge Carriers Along -Conjugated Chainsmentioning

confidence: 99%

Optoelectronic Properties and Nanostructure Formation of σ-Conjugated Polymers

Seki

Tagawa

2007

Polym J

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ABSTRACT:This paper reviews recent studies on the opto-electronic properties of -conjugated polymers as well as the nanostructure formation based on the polymeric materials by the single particle nanofabrication technique. The direct quantitative correlation has been found between backbone conformation of -conjugated polymers and delocalization of charge carriers along their conjugated backbones by transient spectroscopy of the ion radicals. The microwave conductivity measurement technique was applied to estimate the intra-chain mobility of the charge carriers, giving the value of isotropic mobility holes along the chains as ca.. This is suggestive that the potentials of rod-like conjugated backbones in polysilanes as 1-D semiconductor are competitive to those of amorphous silicon.Cross-linking reaction of the -conjugated polymers was firstly promoted by charged particle irradiation to the thin films in the present study. Non-homogeneous cross-linking reaction in the polymers gives clear nanowires whose sizes, length, and number density are fairly controlled by selecting particles, molecular weights, etc. We believe that the present technique is applicable to produce wire-like nanostructures based on a variety of polymeric materials via the simple cross-linking reaction schema.

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“…From figure 5, curvilinear relationship exists between number of scissions in the weathered PP and exposure time. Assuming that linear relationship that existed between the number of scissions and exposure time, it would have only been attributed to zero-order kinetics (Saito 1958b). However, in this study curvilinear relationship exists, therefore, it is suggested that stepwise degradation reaction occur in PP during WPC weathering.…”

Section: Molecular Weight Distributionmentioning

confidence: 55%

Degradation of polypropylene in naturally and artificially weathered plastic matrix composites

Fabiyi

McDonald

2014

Maderas, Cienc. tecnol.

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Effects of accelerated and natural weathering on the molecular weight distribution (MWD) and crystallinity of polypropylene (PP) in wood plastic composites (WPC) were investigated. The composites were produced from pine fibers (60%) and PP (40%). Prolonged weathering caused an increase in wood degradation and erosion thereby leaving cracks and ''pits'' on the surface. Pyrolysis gas chromatography-mass spectrometry (Py GC-MS) revealed that PP dominated the weathered surface due to wood degradation. For matrix analysis, PP was extracted using 1,2,4-trichlorobenzene. Crystallinity and molecular weight distribution of PP were monitored by differential scanning calorimetry (DSC) and gel permeation chromatography (GPC), respectively. PP's crystallinity increased upon longer exposure time. The weight and number average molecular weight (M w and M n ) decreased with an increase in weathering duration. An increased polydispersity (PD = M w /M n ) implies that a secondary cross-linking process occurred during weathering.

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Effects of High Energy Radiation on Polymers II. End-linking and Gel Fraction

Cited by 94 publications

References 1 publication

Oxidative degradation of polylactide (PLA) and its effects on physical and mechanical properties

Oxidative degradation of polylactide (PLA) and its effects on physical and mechanical properties

Optoelectronic Properties and Nanostructure Formation of σ-Conjugated Polymers

Degradation of polypropylene in naturally and artificially weathered plastic matrix composites

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