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1.
The thermal degradation of a highly chlorinated paraffin, (Cl 70% w/w)(CP), used as a fire retardant additive for polymers, has been studied by TG, DTA and TVA. The main volatile degradation product is HCl which is eliminated in two steps. To 60–70% dehydrochlorination an apparent zero order reaction occurs with a detectable rate from 250°C, probably initiated at labile chlorine atoms. The apparent activation energy of the process is 40 kcal/mole. A charred residue containing 35% chlorine is obtained. This residue undergoes nearly complete dehydrochlorination in the range 300–600°C. 相似文献
2.
Elisabeth Egholm JacobsenErik van Hellemond Anders Riise MoenLucia Camino Vazquez Prado Thorleif Anthonsen 《Tetrahedron letters》2003,44(46):8453-8455
In esterifications of secondary alcohols catalyzed by immobilized lipase B from Candida antarctica (Novozym 435) the E-values decreased during the reaction. Hydrolysis of the corresponding butanoates showed the opposite effect. When an enantiopure (R)-alcohol, related but different, was added to the transesterification reaction, the E-value was significantly enhanced. 相似文献
3.
Sergei V. Levchik Giovanni Camino Maria Paola Luda Luigi Costa Bruno Costes Yves Henry Emile Morel George Muller 《先进技术聚合物》1995,6(2):53-62
Tetraglycidyl 4,4′-diaminodiphenylmethane (TGDDM) undergoes homopolymerization on heating. Intramolecular reactions which compete with crosslinking favor the formation of cyclic structures with increasing thermal and fire resistance of the resin, whereas physical mechanical properties tend to decrease. The mechanism of thermal decomposition of TGDDM is studied by thermogravimetry, differential scanning calorimetry and thermal volatilization analysis with characterization of volatiles evolved and residue left. Thermal degradation of poly-(TGDDM) starts at 260°C with elimination of water from secondary alcoholic groups which is a typical pathway for epoxy resin degradation. Resulting unsaturations weaken bonds in the β-position and provoke the first chain breaking at allyl–amine and allyl–either bonds. With increasing temperature, saturated alkyl–ether bonds and alkyl carbon–carbon bonds are broken first, followed by the most stable alkyl–aryl bonds at T>365°C. The combustion performance of TGDDM is discussed on the basis of the thermal degradation behavior. 相似文献
4.
The thermal decomposition of 4,4′-diaminodiphenylsulphone (DDS) was studied by thermogravimetry, differential scanning calorimetry and thermal volatilisation analysis. Solid residues, high-boiling and gaseous products of degradation were collected at each step of thermal decomposition and analysed by infrared spectroscopy and gas chromatography/mass spectrometry.
On programmed heating at normal pressure, DDS starts to evaporate at 250°C. Thermal decomposition, which probably proceeds through homolytic scission of the S-C bond is simultaneously observed. The resulting sulphonyl radicals provoke polymerisation and cross-linking of the solid residue which undergoes a limited degradation at 350°C with elimination of heteroatoms N and S as volatile moieties. Above 400°C, the residue undergoes a complex charring process leading to an aromatic char typical of carbonised aromatic polymers. 相似文献
5.
Modifications in the thermal degradation mechanism of polypropylene caused by interactions between the degrading polymer, a chloroparaffin and bismuth carbonate (typical fire retardant additives) are studied.Preliminary TVA and pyrolysis-GLC results show that volatilisation of the polymer occurs at lower temperatures with production of a larger proportion of higher boiling chain fragments in the mixture than in the pure polymer.The products of a strongly exothermal reaction occurring when the two additives are heated together, as shown by DTA and TG, could play an important role in modifying the thermal degradation behaviour of polypropylene in the mixture. 相似文献
6.
The thermal degradation under vacuum of poly(2,6-dimethoxycarbonyl-1,6-heptadiene), a polymer which contains cyclic structural units, has been investigated. The analysis of the degradation products has shown that depolymerisation (depropagation along the polymer chain with formation of diene monomer) occurs extensively, together with other degradation reactions. A mechanism is proposed to account for the degradation products which have been identified. 相似文献
7.
The thermal degradation to 500°C of urea-formaldehyde polycondensate occurs in four successive steps. In each step, partial volatilisation takes place while the polymer undergoes chemical modification to give progressively more stable structures.Below 200°C methylene ether bridges are transformed into methylene bridges and branching and crosslinking reactions occur with maximum rates at 125°C and 165°C, respectively. Above 200°C radicals formed by chain scission induce the formation of cyclic structures in the polymer which undergoes extensive fragmentation above 300°C. Water, formaldehyde, carbon monoxide and dioxide, methane, ammonia, monomethylamine and trimethylamine are the gaseous products evolved.By combining data on the chemical modifications and gases evolved in each step, reaction mechanisms are proposed. 相似文献
8.
Dr. Camino Bartolomé Dr. Fernando Villafañe Dr. Jose M. Martín‐Alvarez Dr. Jesús M. Martínez‐Ilarduya Prof. Dr. Pablo Espinet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3702-3709
The X‐ray structure of the title compound [Pd(Fmes)2(tmeda)] (Fmes=2,4,6‐tris(trifluoromethyl)phenyl; tmeda=N,N,N′,N′‐tetramethylethylenediamine) shows the existence of uncommon C? H???F? C hydrogen‐bond interactions between methyl groups of the TMEDA ligand and ortho‐CF3 groups of the Fmes ligand. The 19F NMR spectra in CD2Cl2 at very low temperature (157 K) detect restricted rotation for the two ortho‐CF3 groups involved in hydrogen bonding, which might suggest that the hydrogen bond is responsible for this hindrance to rotation. However, a theoretical study of the hydrogen‐bond energy shows that it is too weak (about 7 kJ mol?1) to account for the rotational barrier observed (ΔH≠=26.8 kJ mol?1), and it is the steric hindrance associated with the puckering of the TMEDA ligand that should be held responsible for most of the rotational barrier. At higher temperatures the rotation becomes fast, which requires that the hydrogen bond is continuously being split up and restored and exists only intermittently, following the pulse of the conformational changes of TMEDA. 相似文献
9.
Sergio Bocchini Sandrine Morlat-Thérias Giovanni Camino 《Polymer Degradation and Stability》2007,92(10):1847-1856
Nanocomposites containing pure or organically modified nanoboehmites of different sizes were prepared by melt compounding with polypropylene. The samples were UV light irradiated in artificial accelerated conditions representative of solar irradiation (λ > 300 nm) at 60 °C in air. The chemical modifications resulting from photooxidation were followed by IR and UV-visible spectroscopies. The presence of pristine nanoboehmites was shown to change the rate of oxidation of polypropylene by reducing the oxidation induction period due to the presence of residual processing antioxidant. The differences of the oxidation induction periods between the nanocomposites and the pristine polymer disappear after solvent extraction of the antioxidant. The inefficiency of traditional antioxidant in retarding the photooxidation of polypropylene containing nanodispersed boehmite is proved. Antioxidant migration to the boehmite surface induced by the preferential interaction with the polar filler is proposed as an explanation. The oxidative behaviour of the organically modified boehmites was shown to depend on the type of organic substituent. p-Toluenesulfonate reduces the adsorption of antioxidants while the presence of a long-chain alkyl benzensulfonate increased the oxidation rate by generation of radical initiators. 相似文献
10.
The thermal decomposition of precursors of Li/MgO catalysts prepared from different Mg and Li compounds is reported. Dehydration and dehydroxylation is observed in both cases, in addition to decomposition of LiNO3, but not of Li2CO3. The properties of the solids are related to the melting and spreading of LiNO3 or Li2CO3 before or after Mg(OH)2 dehydroxylation.
Li/MgO, Mg Li. LiNO3, Li2CO3, . LiNO3 Li2CO3 Mg(OH)2.相似文献