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- Author or Editor: Sarfaraz Alam x
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Synthesis of silicon-containing bisnadiimide
Preparation and characterization of semi-interpenetrating network systems of silicon- and fluorine-containing polyimides
Abstract
Silicon-containing thermosetting bisnadiimide (BNI) was synthesized using Bis (amino propyl) tetramethyl disiloxane and nadic anhydride, and fluorine-containing thermoplastic polyamic acid (FPA) was synthesized from 4,4′-(hexafluoroisopropylidene) bis phenoxy dianiline and 4,4′-(hexafluoroisopropylidene) dipthalic anhydride [6-FDA]. The semi-interpenetrating network (s-IPN) systems in various ratios were prepared via solution casting of FAA and crosslinkable BNI, and then curing them up to 370 °C in order to achieve an optimum combination to be used for advanced high temperature composite applications. The polyimides and s-IPN were characterized using NMR and FTIR spectroscopy. The thermo-oxidative and water uptake properties of these polyimides and s-IPNs were investigated. The thermogravimetric analysis (TG) showed increase in thermal stability with the increase in thermoplastic polyimide proportion.
Synthesis and thermal studies of bisphenol-A based bismaleimide
Effect of nanoclays
Abstract
The compound 2,2-bis[4-(4-maleimidophenoxy phenyl)]propane was prepared by the imidization of bisamic acid of 2,2-bis(4-aminophenoxy phenyl)propane. Various nanoclays were blended with this bismaleimide and thermally cured. The structural characterization of the synthesized materials and the thermal properties of the bismaleimide and their blends were investigated through FTIR, 1H and 13C NMR, differential scanning calorimetry and thermo gravimetric analysis. Among the various clays investigated, Cloisite 15A shows strong influence on the cure exotherm of bismaleimide. Introduction of clay mineral into bismaleimide shifts the onset of curing exotherm to higher temperature and is nearly 40 °C. The thermal stability of the clay loaded cured bismaleimide increases and the presence of clay particles in the cured bismaleimide matrix enhances the char formation.
Abstract
Polyimides have aromatic moieties in the backbone structure which are responsible for their increased thermal stability. If phosphorus is introduced in the main chain structure of polyimides, there is further improvement in the thermal stability. This has been proved by the work carried out in our group. The polyimide having amine termination can be used for crosslinking of epoxy resins. In the present study amine terminated phosphorus containing nadicimide were taken as curing agent for DGEBA resins. The curing characteristics of DGEBA resin were studied by DSC using different amounts of nadic endcapped phosphorylated amines. DSC thermogram showed the heat of polymerization was lower as compared to system cured with aromatic amines.
The paper describes the co-curing studies of ethynyl and ethenyl end-capped imide resins. The effect of composition and chemical structure of ethenyl end-capped resins (nadicimides) on thermal behavior of ethynyl end-capped resins was evaluated using DSC and thermogravimetric analysis. An increase in char yield was observed on co-curing of few resin formulations. A mechanism has been proposed to account for this observation.
A simple and sensitive high-performance thin-layer chromatographic (HPTLC)-densitometric method was developed for the simultaneous quantification of two flavonoid compounds, persicogenin and homoeriodictyol, in the methanol extracts of the aerial parts of two species (Rhus retinorrhoea and Rhus tripartita) of the genus Rhus grown in the Kingdom of Saudi Arabia. Chromatography was performed on glass-backed silica gel 60 F254 HPTLC plates using toluene-ethyl acetate-methanol (8:2:0.5, v/v) as the mobile phase. Scanning and quantification were done at 293 nm. The system was found to give compact spot for homoeriodictyol and persicogenin at, R F = 0.30 ± 0.01 and 0.48 ± 0.01, respectively. The linearity ranges for homoeriodictyol and persicogenin were found to be the same (100–800 ng spot−1) with correlation coefficients (r 2 values) of 0.9989 and 0.9983, respectively. The limit of detection (LOD) for homoeriodictyol and persicogenin was found to be 26 and 31 ng band−1, respectively, while the limit of quantification (LOQ) was found to be 77 and 92 ng band−1, respectively. Homoeriodictyol (7.06%) and persicogenin (2.33%) were only found in R. retinorrhoea. The developed method was found to be accurate and precise; hence, it can be used as an important tool to assure the therapeutic dose of homoeriodictyol and persicogenin in herbal formulations as well as for the standardization and quality control of bulk drugs.