Showing papers in "High Performance Polymers in 1992"
TL;DR: In this paper, a Diels-Alder reaction of furfuralacetone (FAC) resin with various bismaleimides was carried out in tetrahydrofuran (THF) as solvent as well as in bulk.
Abstract: Polyimides were prepared by Diels-Alder (DA) reaction of furfuralacetone (FAC) resin [poly(4-furanyl-butan-2-one)] with various bismaleimides. The DA reaction was carried out in tetrahydrofuran (THF) as solvent as well as in bulk, followed by aromatization of the tetrahydrophthalimide intermediates in the presence of acetic anhydride. All the polyimides were characterized by elemental analysis, IR spectral studies and thermogravimetry. The results show that polyimides based on FAC resin exhibit good thermal stability. Preliminary tests for glass reinforcement of the polyimides indicate that laminates with good mechanical strength can be prepared.
25 citations
TL;DR: In this article, an Acrylonitrile (AN) was grafted onto sodium alginate (SA) using ceric salt as an initiator, and the optimized reaction conditions affording the maximum percentage of grafting were determined by varying the concentrations of nitric acid, ceric ammonium nitrate, SA and AN, and also temperature and time.
Abstract: Acrylonitrile (AN) was grafted onto sodium alginate (SA) using ceric salt as initiator. The optimized reaction conditions affording the maximum percentage of grafting are determined by varying the concentrations of nitric acid, ceric ammonium nitrate, SA and AN, and also temperature and time. The results are discussed and the efficiency of ceric salt is compared with that of Fenton's reagent.
22 citations
TL;DR: In this paper, two diamines containing aromatic diamines were synthesized by reaction of aminophenols with 2,5-bis(4-fluorophenyl)-4l3,4-oxadiazole in a polar aprotic solvent in the presence of potassium carbonate.
Abstract: Two oxadiazole containing aromatic diamines were synthesized. The diamines were prepared by reaction of aminophenols with 2,5-bis(4-fluorophenyl)-4l3,4-oxadiazole in a polar aprotic solvent in the presence of potassium carbonate. Reaction of the resulting 2,5-bis(4-(aminophenoxy)phenyl)-1,3,4-oxadiazoles with dianhydrides gave a series of polymeric amic acids. Thermal treatment yielded poly(imide ether oxadazole) films which displayed good thermal stability, flexibility, and glass transition temperatures ranging from 241 to 344C. The dielectric constants of the films were characterized as a function of relative humidity.
21 citations
TL;DR: In this article, a novel approach was used to develop a matrix resin for processable poiyimide-glass-fibre composites without the evolution oQf by-products.
Abstract: A novel approach was used to develop a matrix resin for processable poiyimide-glass-fibre composites. Furfural-acetone (FAC) resin, poly(4-Furanyl butan-2-one), and various bismaleimides were polymerized at 140 + 10 and 180+ 10+C by in situ Diels-Alder intermolecular reaction into moderately thermally stable and highly cross-linked polyimide-glass-fibre composites without the evolution oQf by-products. The fabricated composites (i.e. laminates) were characterized by their chemical resistance and mechanical properties
19 citations
TL;DR: In this paper, a Diels-Alder reaction of furfuryl-disulphide with various bismaleimides was carried out in xylene as solvent, as well as in bulk, followed by aromatization of terrahydrophthalimide intermediates.
Abstract: Poly (disulphido-imides) were prepared by Diels-Alder (DA) reaction of furfuryl-disulphide (FDS) with various bismaleimides. The DA reaction was carried out in xylene as solvent, as well as in bulk, followed by aromatization of terrahydrophthalimide intermediates in the presence of acetic anhydride. All the poly (disulphido-imide)s were characterized by elemental analyses, IR spectral data and thermogravimetry. The poly (disulphido-imide)s exhibit moderate thermal stability. Preliminary test for glass reinforcement of the poly (disulphido-imide) indicate that laminates with good mechanical strength can be obtained.
17 citations
TL;DR: A series of three polybenzazoles containing hexafluoroisopropylidene (HFIP-PBZs) were produced in order to study the effect of including the HFIP group into the rigid PBZ backbone.
Abstract: A series of three polybenzazoles containing hexafluoroisopropylidene (HFIP-PBZs) were produced in order to study the effect of including the HFIP group into the rigid PBZ backbone. The monomers, 2,5-diamino-1,4-benzenedithiol dihydro-chloride and 4,6-diamino-1,3-benzenediol dihydrochloride, were synthesized and puri-fied. The monomer 1,2,4,5-tetraaminobenzene tetrahydrochloride is commercially avail-able and was purified by recrystallization. These mononmers were polymerized with 2,2-his(4-carboxyphenyl)-I1,,1,3,3,3-hexafluoropropane (6F-diacid) by a polycondensation reaction in polyphosphoric acid employing the P205 adjustment method to give polymers in good yields with inherent viscosities ranging from 0.33 to 1.18 dl/g. These polymers show an increase in solubility over non-HFIlP containing PBZs and display excellent thermal stability by thermogravimetric analysis (540-568°C in argon). Isothermal aging in air of the polymers for 300 h afforded weight losses between 3.27 and 12.0%.
13 citations
TL;DR: In this article, a novel epoxy resins containing copper was synthesized by reacting copper acrylate with bisphenol A and excess epicholorohydrin, which improved electrical properties and excellent thermal and chemical resistance in comparison with the control resin.
Abstract: Novel epoxy resins containing copper have been synthesized by reacting copper acrylate with bisphenol A and excess epicholorohydrin. Values of as epoxy equivalent weight, hydroxyl content and hydrolyzable chlorine content have been estimated. The resins have been characterized by IR, 1H-NMR and 13C-NMR analysis. The cured resins were evaluated for thermal properties. The curing of resins has been carried out with polyamide at 30 °C and with phenacyl dimethyl sulfonium ylide mercuric chloride complex by heating at 150 °C for 8 h and at 180 °C for 3 h. The cured resins have improved electrical properties and excellent thermal and chemical resistance in comparison with the control resin. The reaction follows first-order kinetics with activation energies of 47 and 34 kJ/mol in the presence and absence, respectively, of copper actrylate. The copper forms a complex with bisphenol A, as indicated by spectroscopic studies, which increases the epoxidation rate.
12 citations
TL;DR: In this paper, 3,5-Bis(p-hydroxybenylidene)-isopropylpiperidinone (BHIP) and DVIP were used as starting materials for preparing new unsaturated polyesters.
Abstract: 3,5-Bis(p-hydroxybenylidene)-isopropylpiperidinone (BHIP) and 3,5-divanillylidene-isopropylpiperidinone (DVIP) were used as new starting materials for preparing new unsaturated polyesters. The polyesters were prepared by reacting BHIP or DVIP with adipoyl, sebacoyl, isophthaloyl or terephthaloyl dichlorides utilizing the interfacial polycondensation technique. In addition, the model compounds were synthesized by reacting BHIP or DVIP with benzoyl chloride. The model compounds were characterized by 'H-NMR, IR, and elemental analyses. The polyester samples have been characterized by elemental and spectral analyses. All the synthesized polymers readily dissolved at room temperature in dimethylsulphoxide or concentrated sulphuric acid. The thermal properties of the polymers were evaluated and correlated to their structural units by TGA measurements. X-ray analysis of the polymers showed that all the polyesters are amorphous.
11 citations
TL;DR: In this article, the formation of a short-lived Mn(VI) intermediate was confirmed during the oxidation of alginae polysaccharide by potassium permanganate in alkaline medium at pH> 12.
Abstract: Spectrophotometric evidence for the formation of a short-lived Mn(VI) intermediate has been confirmed during the oxidation of alginae polysaccharide by potassium permanganate in alkaline medium at pH> 12. This Mn(VI) intermediate was characterized by a band at a wavelength of 606 nm, an absorption maximum, with a molar extinction coefficient of 1200 + 50 dm3/mol/cm.
10 citations
TL;DR: In this paper, a series of semi-I tpe interpenetrating polymer networks (IPN) based on poly chromium acrylate and poly acrylonitrile crosslinked with divinyl benzene have been synthesized.
Abstract: A series of semi-I tpe interpenetrating polymer networks (IPN) based on poly chromium acrylate and poly acrylonitrile crosslinked with divinyl benzene have been synthesized. Synthetic details, including concentration of poly chromium acriylate (PCrA), acrylonitrile (AN) and divinyl benzene (DVB) and average molecular weight of PCrA were varied and their effect on the crosslink density of the network was studied by swelling experiments. High [PCrAJ and low [AN] increases swelling and thereby average molecular weight between crosslinks (M,). SEM micrographs and glass transition temperature show phase separation at high [PCrA] content.
9 citations
TL;DR: In this article, the adhesive bond performance of PEEK-graphite composites (APC-2/AS4) with melt fabricated films derived from either a novel thermoplastic poly(imide-30 wt% siloxane) segmented copolymer or a commercial thermopolymer polyetherimide (Ultem® 1000), has been studied as a function of surface modifications.
Abstract: The adhesive bond performance of PEEK®-graphite composites (APC-2/AS4) with melt fabricated films derived from either a novel thermoplastic poly(imide-30 wt% siloxane) segmented copolymer or commercial thermoplastic polyetherimide (Ultem® 1000), has been studied as a function of surface modifications. The latter included grit blasting and gas plasma etching treatments with oxygen, ammonia, nitrogen and argon. Adhesive bond strength was evaluated with single lap shear samples (SLSS) which were prepared from PEEKl-graphite composite adherends and compression molded thermoplastic poly(imide-30 wt% siloxane) segmented copolymer film adhesives. Greatly improved single lap shear strength values were obtained by several gas plasma treatments as well as by grit blasting. For example, SLSS values were increased from less than 1000 psi to approximately 5000 psi. The morphological and chemical changes of PEEKS-graphite composites with surface treatment were investigated by scanning electron microscopy (SEM), contact...
TL;DR: In this paper, the kinetics or chemical equilibria of exchange of Ca(II), Sr (II), Ba(I), Zn (I), Cd(II, Al(III), Fe(III, Se(IV), Ce(IV, and Th(IV) counter ions in alginate gel complexes by H+ ions were investigated titrimetrically and conductimetrically at a constant ionic strength of 0.1 mol/dm3.
Abstract: The kinetics or chemical equilibria of exchange of Ca(II), Sr(II), Ba(I), Zn(II), Cd(II), Al(III), Fe(III), Se(IV), Ce(IV) and Th(IV) counter ions in alginate gel complexes by H+ ions have been investigated titrimetrically and conductimetrically at a constant ionic strength of 0.1 mol/dm3. The thermodynamic parameters have been evaluated and are discussed in terms of ionic radii and polarizability of the metal ions, coordination geometry, and stability of the gel complexes.
TL;DR: In this paper, the separation of divalent metal ion mixtures was investigated chromatographically on columns of either gel or sol forms of alginate polyelectrolyte.
Abstract: The separation of divalent metal ion mixtures has been investigated chromatographically on columns of either gel or sol forms of alginate polyelectrolyte. Separation was obtained in the form of narrow sharp zones for the metal ions. Ion exchange selectivity indicated that Cu2+ ions were most strongly retained among the divalent metal ions studied. The factors which affect the ion exchange selectivity, such as the strength of chelation and the mobility and radii of the metal ions, are discussed. The selectivity coefficient for the separation of a mixture of Cu2+ and Co2+ ions on columns of calcium alginate gel or sodium alginate sol was determined and found to be 1.9 ± 0.1 in both ion exchangers at 25°C.
TL;DR: In this paper, it is found that fairly modest additions of the liquid crystalline polymer (LCP) lead to a pronounced improvement in barer properties, which is attributed to the formation of a thin surface layer of the LCP.
Abstract: Blends of polyethersulphone (PES) and a thermotropic copolyester based on hydroxynaphthoic acid and hydroxybenzoic acid residues have been examined. The permeability to oxygen of thin pressed films of a range of compositions has been studied. It is found that fairly modest additions of the liquid crystalline polymer (LCP) lead to a pronounced improvement in barer properties. This improvement is ascribed to the formation of a thin surface layer of the LCP. The existence of this LCP surface layer is supported by examination in the scanning electron microscope of dimethyl formamide etched samples: etching does not remove all the PES because it is protected from the etchant by the surface layer.
TL;DR: In this paper, the effect of the thermal history of the melt on the morphology and the mechanical properties of the surface of crystallized poly(aryl-ether-etherketone) (PEEK) films was followed by density measurements, X-ray diffraction, differential scanning calorimetry and microindentation.
Abstract: In this study, the effect of the thermal history of the melt on the morphology and the mechanical properties of the surface of crystallized poly(aryl-ether-ether-ketone) (PEEK) films was followed by density measurements, X-ray diffraction, differential scanning calorimetry and microindentation. The study has shown a decrease in microhardness of the polymer surface as the temperature at which the polymer is kept in the molten state increases and as the time spent in the molten state becomes longer. The study suggests that keeping PEEK for long periods of time in the molten state, in the presence of oxygen, results in chemical changes (presumably crosslinking involving oxygen atoms) which are responsible for drastic changes in the morphological characteristics of the samples and consequently on the mechanical properties of the surface of the solidified material. Above 400 °C, in air, a total change in surface morphology takes place and the mechanical properties of the surface are degraded. The study also su...
TL;DR: In this article, the CP/MAS 13C-NMR spectrum of bis(3,4-dicarboxyphenyl)-dimethylsilane dianhydride (SiDA) as well as the spectra of the N-methyl and N-n-propyl bisimides derived from SiDA derived from this dian hydride were used to confirm the occurrence of solid state charge transfer complex (CTC) formation.
Abstract: The CP/MAS 13C-NMR spectrum of bis(3,4-dicarboxyphenyl)-dimethylsilane dianhydride (SiDA) as well as the spectra of the N-methyl and N-n-propyl bisimides derived from this dianhydride confirm the occurrence of solid state charge transfer complex (CTC) formation in these compounds. The proposed solid state alignment for SiDA was confirmed by X-ray diffraction spectroscopy. These compounds are monomeric models for polyimides and CTC formation in them supports the probability that such complexes form in polyimides.
TL;DR: Differential scanning calorimetry was used to srudy the cure kinetics of three epoxy resin systems cured with two hardeners: diaminodiphenylmethane (DDM) and a poly (keto-amine) (PA).
Abstract: Differential scanning calorimetry was used to srudy the cure kinetics of three epoxy resin systems cured with two hardeners: diaminodiphenylmethane (DDM) and a poly (keto-amine) (PA). The results showed that the curing of the epoxy resins by PA Occurs at higher temperarures and the 'activation energy for PA curing was higher
compared with the DDM curing process, showing the lower reactivity of PA.
TL;DR: A high molecular weight copolymer of N-acryloyl-o-aminobenzoic acid (OAB) and styrene has been prepared by radical polymerization using benzoyl peroxide initiator in dioxane solvent.
Abstract: A high molecular weight copolymer of N-acryloyl-o-aminobenzoic acid (OAB) and styrene has been prepared by radical polymerization using benzoyl peroxide initiator in dioxane solvent. The copolymer has been fractionated by fractional precipitation and the fractions characterized by viscometry, vapour pressure osmometry and gel permeation chromatography. Mark-Houwink-Kuhn-Sakurada (MHKS) relationships are developed for three different solvents. Both the intrinsic viscosities and the viscosity constants of eight PO-PS fractions were obtained by the Huggins, Kraemer, Martin and Schulz-Blaschke methods in dimethyl formnamide, toluene and tetrahydrofuran solvents. It was concluded that the values obtained by these four methods are in close agreement.
TL;DR: In this article, a series of imide/arylene ether block and segmented copolymers were prepared and characterized, and the properties of the copolymer films were measured.
Abstract: As part of an effort to develop high performance structural resins for aerospace applications, work has continued on block copolymers containing imide and arylene ether segments. The arylene ether block used in this study contains a bulky fluorene group in the polymer backbone while the imide block contains an arylene ketone segment similar to that in the arylene ether block and has been named LaRC-ITPI. A series of imide/arylene ether block and segmented copolymers were prepared and characterized. Films were prepared from these copolymers and mechanical properties were measured.
TL;DR: In this paper, the non-isothermal decomposition of certain Iodo-organometallic arylidene polyesters and OCH3 groups was investigated with TGA measurements at atmospheric pressure.
Abstract: Studies of non-isothermal decomposition of certain iodo-organometallic arylidene polyesters and organometallic arylidene polyesters have been performed with TGA measurements at atmospheric pressure. The analysis of the non-isothermal TG and DTG curves of the samples under investigation revealed that their decomposition course proceeds via three stages. The kinetic parameters such as activation energy (E,), preexponential factor (A) and entropy of activation (AS*) for all polymers at different decomposition stages are determinedfrom an appropriate kinetic equation. More particularly, the data showed that the thermal stability of some of the polymers decreases with increasing ring size of arylidene moieties. Furthermore, the effect of absence of iodoand presence of-OCH3 groups upon the thermal properties of polymers was also evaluated.
TL;DR: In this article, copolymers were prepared by the condensation reaction of formaldehyde and 2,4-dihydroxy benzophenone, 2-hydroxy-4-methoxy benzphenone, and 2hydroxy 4-butoxy benzhenone, which were subjected to UV irradiation and then tested for any change in the carbonyl index, hydroxyl index, tensile strength, elongation at break and evaporation loss.
Abstract: Copolymers were prepared by the condensation reaction of formaldehyde and 2,4-dihydroxy benzophenone, 2-hydroxy-4-methoxy benzophenone and 2-hydroxy-4-butoxy benzophenone. The polystyrene films incorporated with these stabilizers were subjected to UV irradiation and then tested for any change in the carbonyl index, hydroxyl index, tensile strength, elongation at break and evaporation loss to evaluate the efficiency of the new stabilizers.
TL;DR: In this article, unsaturated polyamides were prepared by condensing /3(4-ethoxyphenyl) glutaconic acid with various aromatic diamines.
Abstract: Unsaturated polyamides were prepared by condensing /3(4-ethoxyphenyl) glutaconic acid with various aromatic diamines. The polycondensates were characterized by IR spectroscopy, vapor phase osmometry, thermogravimetric analysis, differential scanning calorimetry and elemental analysis. All resins were found to decompose in the range '-210-600 °C. The kinetics of decomposition were studied. The results indicated that the resins possess reasonably good thermal stability.
TL;DR: In this article, seven chlorine-terminated polyketones of low molecular weight were obtained from m-xylene, chloroacetyl chloride and ao-dichloroalkanes.
Abstract: Seven chlorine-terminated polyketones of low molecular weight were prepared from m-xylene, chloroacetyl chloride and ao-dichloroalkanes, i.e. dichloro-methane and 1,2-dichloroethane, by the Friedel...