References of "Polymer Degradation & Stability"
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See detailInfluence of steam explosion on the thermal stability of cellulose fibres
Jacquet, Nicolas ULg; Quievy, Nicolas; Vanderghem, Caroline ULg et al

in Polymer Degradation & Stability (2011), 96

The aim of the present study was to compare the effect of different steam explosion treatments on the thermal degradation of a bleached cellulose. The intensity of a steam explosion treatment, which ... [more ▼]

The aim of the present study was to compare the effect of different steam explosion treatments on the thermal degradation of a bleached cellulose. The intensity of a steam explosion treatment, which allows breakdown of the structural lignocellulosic material was determined by a correlation between time and temperature of the process. Results of this study showed that thermal degradation of cellulose fibres was limited when the severity factor applied was below 4.0. For higher intensities, determination of the degradation products in the water-soluble extract showed an important increase of the 5-hydroxymethyl-furfural concentration with the temperature. When the severity factor reached 5.2., TGA analysis showed that the increase of degradation products was coupled to an increase of the char level meaning a strong degradation of the cellulose. dTGA behaviour also showed that thermal stability of the steam explosion samples decreased with the intensity of the treatment. To conclude, a theoretical diagram predicting the degradation of the cellulose during the steam explosion treatment was established. [less ▲]

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See detailImpact of formic/acetic acid and ammonia pre-treatments on chemical structure and physico-chemical properties of Miscanthus x giganteus lignins
Vanderghem, Caroline ULg; Richel, Aurore ULg; Jacquet, Nicolas ULg et al

in Polymer Degradation & Stability (2011), 96(10), 1761-1770

Miscanthus x giganteus was treated with formic acid/acetic acid/water (30/50/20 v/v) for 3 h at 107 C and 80° C, and soaking in aqueous ammonia (25% w/w) for 6 h at 60 C. The effects of these ... [more ▼]

Miscanthus x giganteus was treated with formic acid/acetic acid/water (30/50/20 v/v) for 3 h at 107 C and 80° C, and soaking in aqueous ammonia (25% w/w) for 6 h at 60 C. The effects of these fractionation processes on chemical structure, physico-chemical properties and antioxidant activity of extracted lignins were investigated. Lignins were characterized by their purity, carbohydrate composition, thermal stability, molecular weight and by Fourier transform infrared (FTIR), 1H and quantitative 13C nuclear magnetic resonance (NMR), adiabatic broadband {13C-1H} 2D heteronuclear (multiplicity edited) single quantum coherence (g-HSQCAD). The radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) was also investigated. Formic/acetic acid pretreatment performed in milder conditions (80° C for 3 h) gave a delignification percentage of 44.7% and soaking in aqueous ammonia 36.3%. Formic/acetic acid pretreatment performed in harsh conditions (107°C for 3 h) was more effective for extensive delignification (86.5%) and delivered the most pure lignin (80%). The three lignin fractions contained carbohydrate in different extent: 3% for the lignin obtained after the formic/acetic acid pretreatment performed at 107 C (FAL-107), 5.8% for the formic/acetic acid performed at 80°C (FAL-80) and 13.7% for the ammonia lignin (AL). The acid pretreatment in harsh conditions (FAL-107) resulted in cleavage of b-O-4' bonds and aromatic C-C. Repolymerisation was thought to originate from formation of new aromatic C-O linkages. Under milder conditions (FAL-80) less b-O-4' linkages were broken and repolymerisation took place to a lesser extent. Ammonia lignin was not degraded to a significant extent and resulted in the highest weight average 3140 g mol -1. Despite the fact of FAL-107 repolymerisation, significant phenolic hydroxyls remained free, explaining the greater antioxidant activity. [less ▲]

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See detailPoly(ethylene-co-vinyl acetate)/clay nanocomposites: Effect of clay nature and organic modifiers on morphology, mechanical and thermal properties
Peeterbroeck, Sophie; Alexandre, Michaël ULg; Jérôme, Robert ULg et al

in Polymer Degradation & Stability (2005), 90(2), 288-294

Nanocomposites based on an ethylene vinyl acetate copolymer (27 wt% vinyl acetate) and various (organo-modified) clays have been prepared by melt blending and their morphology, tensile and thermal ... [more ▼]

Nanocomposites based on an ethylene vinyl acetate copolymer (27 wt% vinyl acetate) and various (organo-modified) clays have been prepared by melt blending and their morphology, tensile and thermal degradation properties have been evaluated. Special attention has been paid to the influence of the clay nature and origin (montmorillonite or fluoromica) as well as on the nature of the ammonium cation organic modifier. It has been shown that nanostructure and tensile properties mainly depend on the nature of the organic modifier while the delay in thermal volatilisation of EVA during thermo-oxidation is mainly driven by the nature of the clay (mainly its aspect ratio), with no significant influence of the nanostructure of the nature of the organic modifier. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailBlock and random copolymers of ε-caprolactone
Duda, Andrzej; Biela, Tadeusz; Libiszowski, Jan et al

in Polymer Degradation & Stability (1998), 59(1-3), 215-222

Conditions of the living homopolymerization of epsilon-caprolactone (CL), lactides (LA), and of the homo-oligomerization of gamma-butyrolactone (BL) are briefly described. Then block and random ... [more ▼]

Conditions of the living homopolymerization of epsilon-caprolactone (CL), lactides (LA), and of the homo-oligomerization of gamma-butyrolactone (BL) are briefly described. Then block and random copolymerizations of CL with LA are shortly reviewed. The microstructure of the resulting copolyesters in relation to some peculiarities of these processes is discussed in more detail. It is also shown that the otherwise 'non-polymerizable' BL does form high molecular weight copolymers with CL, containing up to 50 mol% repeating units derived from BL. Their molecular weight is controlled by the concentrations of the consumed comonomers and the starting concentration of the initiator. NMR and DSC data indicate the random structure of copolymers. TGA traces of the BL/CL copolymers show that the presence of the gamma-oxybutyryl repeating units randomly distributed within the poly(CL) chains improves the thermal stability of the latter. [less ▲]

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