Search Results
Abstract
Polyamide-6-block-polybutadiene copolymers have been prepared by the anionic polymerization of ɛ-caprolactam in presence of α,ω-dihydroxy terminated polybutadiene. TG, Hi-Res™ TGA, DSC, TMDSC and DMA techniques have been applied. The suitability of the methods used to determine the content, thermal stabilities and glass transition temperatures of the components constituting the block copolymer is discussed.
Abstract
The TG analyses are given for variously meta- and/or para-linked aromatic polyamides with various benzimidazolyl (BI)contents. The TG curves of the polymers were evaluated within 600C by use of an equation for multiple events. The TG curves of BI-substituted polymers are expressed for triple events, though the TG curves of unsubstituted polymer are expressed for double events. The amount of residue of BI-substituted polymers at 800C is larger than that of unsubstituted polymers, perhaps because moieties concerning BI degrade at higher temperatures.
Abstract
Thermogravimetric data and the kinetic interpretation of the curves of mass loss for ferrocene, ferrocenecarboxylic and ferrocenedicarboxylic acids and a series of ferrocene-containing polyamides are presented. The results indicate that the degradation process occurred with more than one stage of thermal degradation. The apparent activation energy values and the FTIR spectra of the degradation products suggest that the degradation mechanism occurred by either scission of weak links or by random scission of the chain. Apparently, the N-vicinal methylene group was the primary site of attack of oxygen on the polymer chain.
Abstract
The thermal stability of heat-stabilised polyamide 66 in an oxidative environment is evaluated by DSC. The oxidative stability of the polyamide decreases as a result of repeated injection moulding. The results also indicate that the presence of glass fibres in the polyamide has a negative influence on the oxidative stability. Both isothermal and dynamic DSC measurements seem to be useful tools for assessing the stability of polyamides and there is a relationship between data determined using both procedures.
The potential of polyamide as adsorbent for separation of nine compounds — (±)-catechin (DL-C), (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECg), (−)-epigallocatechin gallate (EGCg), theaflavin (TF1), theaflavin 3-gallate (TF2A), theaflavin 3′-gallate (TF2B), and theaflavin 3,3′-digallate (TF3) — was studied. Polyamide TLC plates dried with a hair dryer, application as bands, and development in a horizontal chamber gave the best results. Detection was performed using iron(III) chloride-ethanol reagent. Twofold development with chloroform-methanol 2:3 ( v/v ) as mobile phase resulted in the separation of TF1, TF2A, TF2B, and TF3 from all the other compounds. EGCg, ECg, and EGC were separated but EC and DL-C were not separated from each other. The best mobile phase for each of the compounds is reported. The best separation of the five main catechins (EC, DL-C, EGC, ECg, and EGCg) was achieved by use of n -butanol-acetone-acetic acid 5:5:3 ( v/v ). In addition, separation of the flavonols myricetin, quercetin, kaempferol, and rutin and the phenolic acids gallic acid, chlorogenic acid, and caffeic acid was achieved by twofold development with chloroform-methanol 2:3 ( v/v ). The applicability of the method was checked by screening of extracts of green, black, oolong, and pu-erh tea.
Antioxidants are added to the polymers to suppress oxidation during the service life. The paper deals with determination of stabilizer (VANOX-SKT) antioxidant in polyamides using a differential scanning calorimeter. Normally the amount of antioxidants is determined using HPLC method which takes more than 48 hours for sample preparation. A series of polyamide samples with known content of antioxidants (0.0–0.8%) are analysed using DSC form −50 to 350 °C in oxygen atmosphere keeping Al-crucibles open. For all the compositions a linear relationship was found forΔH (heat of degradation) and induction time under isothermal conditions at 220 °C which enables the antioxidant VANOX-SKT to be determined in unknown samples.
Abstract
The aim of this work was to obtain membranes from polyamide 6/montmorillonite clay nanocomposites through the phase inversion technique. The nanocomposites and membranes from polyamide 6/montmorillonite clay were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). Microporous and asymmetric membranes were successfully obtained from nanocomposites and the results showed that the salts were incorporated by intercalation between the organoclay layers and, apparently that the nanocomposites and membranes were thermally more stable than the pure polyamide.
Abstract
Aromatic polyamides find many applications in diverse and critical areas due to their high thermal stability coupled with high mechanical properties. However most of such aramides are difficult to fabricate because of their limited solubility and high melting temperature. Improvements in processability have been reported by incorporating bulky pendant groups and aliphatic spacer groups. Similarly to improve the solubility of polymers approaches of incorporating silicon in main polymer chain and co-polymerization techniques were useful. We report the synthesis and characterization of a series of phenylated silicon containing aromatic–aliphatic polyamides from a mixture of 2, 5-bis (4-carboxy methylene phenyl)-3, 4-diphenyl thiophene (CMPDT) and bis-(4-carboxy phenyl) dimethyl silane (BCPDS) in various mole proportions, with commercial aromatic diamine. Thus a series of novel co-polyamides having pendant phenyl groups, methylene spacer and silicon moiety was prepared by judicious combination of (CMPDT); BCPDS and aromatic diamine; bis-(4-aminophenyl) ether (ODA), by direct polycondensation using Yamazaki’s phosphorylation method. These high molecular mass polyamides were obtained in high (89–98%) yields and had viscosities in the range of 0.23–0.57 dL/g in DMAc. Polyamides showed improved solubility in polar aprotic solvents, like NMP, DMAc, DMSO and DMF; had high thermal stability; with no mass loss below 335 °C.
Aromatic polyamides
VIII. Kinetic analysis of the thermal- and thermo-oxidative degradation
Abstract
Polymer blends of poly(β-hydroxybutyrate-co-b-hydroxyvalerate) (Biopol) with polyamide 11, possessing copolyester continuous phase, were degraded during 25 weeks in compost. The biodegradation was followed by mass loss and melting enthalpy measurements. The degradability was primary dependent on the hydroxyvalerate content in the blend.
