Kinetic study of the thermal degradation of poly(aryl ether ketone)s containing 2,7‐naphthalene moieties

The degradation of poly(aryl ether ketone) containing 2,7‐naphthalene moieties was subjected to dynamic and isothermal thermogravimetry in nitrogen and air. The dynamic experiments showed that the initial degradation temperature, temperature for 5% weight loss, and temperature corresponding to the maximum degradation rate of poly(aryl ether ketone) containing 2,7‐naphthalene moieties were a little higher than those of poly(ether ether ketone) and almost independent of the 2,7‐naphthalene moiety content. The thermal stability of poly(aryl ether ketone) containing 2,7‐naphthalene moieties in air was substantially less than that in nitrogen, and the degradation mechanism was more complex. The results obtained under the isothermal conditions were in agreement with the corresponding results obtained in nitrogen and air under the dynamic conditions. In the dynamic experiments, the apparent activation energies for the degradation processes were 240 and 218 kJ/mol in nitrogen and air for the second reaction stage as the heating rate was higher than 5°C/min. In the isothermal experiments, the apparent activation energies for the degradation processes were 222 and 190 kJ/mol in nitrogen and air, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(aryl ether sulfide)s by sulfide-activated nucleophilic aromatic substitution polymerization

Poly(aryl ether sulfide)s have been produced by nucleophilic aromatic substitution with phenoxide nucleophiles bisphenol A and bisphenol AF, and the activated arylfluorides bis(4-fluorophenyl)sulfide and 2,7-difluorothianthrene. The resulting polymers are thermally stable, amorphous materials that have been characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). Moderate molecular weights have been achieved, representative of greater than 98% conversion of arylfluorides. The poly(aryl ether thianthrene)s are flame resistant and self extinguish within 0.2 s upon removal from a flame source. TGA of the poly(aryl ether thianthrene)s in an inert atmosphere result in a char yield greater than 50% at 750 °C. The flame resistant properties are more effectively modeled by TGA in an inert atmosphere as compared to TGA in an air atmosphere. The poly(aryl ether thianthrene)s are found to have high refractive index values, 1.61-1.70, depending on wavelength and bisphenol composition.     

车用燃料电池质子交换膜的制备及性能

合成了一系列具有不同支化度的磺化聚芳醚砜材料,并对其结构和性能进行了表征。所制备的磺化的支化聚芳醚砜材料的分子量可达7.00×105以上,并且分子量分布在1.17左右,拉伸强度可达20.55~28.81 MPa。随着聚合物支化度的增加,聚合物的热稳定性得到改善,在550℃下的热失重可降低至39%~45%。高支化的磺化聚芳醚砜薄膜的氧化稳定性也得到改善,80℃下的使用寿命可提高至7.25 h。支化的磺化聚芳醚砜薄膜的吸水率和质子传导率都较高。80℃下高支化度的聚芳醚砜薄膜的质子传导率可达0.33 S/cm。对其微观形貌进行观测发现,支化聚芳醚砜中的支化结构可对周围的亲水磺酸基团起支撑作用,促使其发生团聚而形成连续的质子通道。     

Synthesis and properties of a cyclic oligo(aryl ether ketone) based on bisphenol A and its polymerization

A cyclic oligo(aryl ether ketone) based on bisphenol A (CBAEK) was successfully synthesized via the nucleophilic substitution reaction of 4,4'-difluorobenzophenone and bisphenol A with the use of pseudo-high dilution condition. The structure of the cyclic oligomer was characterized by IR and NMR spectroscopy as well as matrix-assisted laser desorption ionization time-of-flight mass spectroscopy (MALDI-TOF-MS), in comparison with those of the corresponding fluorine- and hydroxy-terminated linear (aryl ether ketone) oligomers (BAEK-F and BAEK-OH). From differential scanning calorimetry and wide angle X-ray diffraction measurements it was revealed that CBAEK exhibits a high degree of crystallinity, while BAEK-F and BAEK-OH are amorphous. Ring-opening polymerization of CBAEK proceeded smoothly in the presence of potassium carbonate at 400°C to give a linear poly(aryl ether ketone).     

Synthesis, characterization, thermal and flame retardant properties of novel aryl phosphinate diglycidyl ether cured with anhydride

A novel aryl phosphinate diglycidyl ether, 10-(2′,5′-diglycidyl ether phenyl)-9,10-dihydro-9-oxa-l0-phosphaphenanthrene-10-oxide (DHQEP), was synthesized. The structure of the diglycidyl ether was characterized by elemental analysis, mass, FTIR, ¹H, ¹³C, ³¹P NMR spectroscopies and X-ray single crystal analysis. In addition, compositions of the diglycidyl ether with three curing agents, e.g. phthalic anhydride (PA), hexahydrophthalic anhydride (HHPA), and aryl phosphinate anhydride (DMSA), were used for making a comparison of its heat and flame retardancy with that of DER331 and DEN438. The resulting aryl phosphinate epoxy-resin composites demonstrated a higher limiting oxygen index (LOT) value as well as a higher char yield, confirming the effectiveness of aryl phosphinate epoxide as a flame retardant for epoxy resins.     

Photoinduzierte H-Abstraktionen an Benzylarylethern durch Benzophenon

Photoinduced H-Abstraction on Benzyl Aryl Ethers by Benzophenone The triplet state of benzophenone abstracts in benzene of benzyl aryl ether 6 hydrogen atom from the CH₂-group. The formed α-ether radicals 1 and diphenylhydroxymethyl radicals 8 react to form the three possible reaction products in statistical distribution. Benzaldehydes 2 and phenols 11 are formed in a side reaction. From quantum yield measurements of the benzophenone reduction in dependence upon the concentration of benzyl phenyl ether 6a follows a rate constant of the H-abstraction of 9.5 ·10⁵ M⁻¹s⁻¹ which is in good agreement with measurements in presence of naphthalene as a quencher. The quenching constant for benzophenone triplet by naphthalene is 2 · 10⁹ M⁻¹s⁻¹. For benzyl phenyl ethers substituted in the benzyl ring the reaction constant for the H-abstraction reaction was determined, ϱ = −0,68,     

Thermal alkylation of aromatic nucleus with aryl benzyl ethers

The introduction of the benzyl group into the aromatic nucleus is brought about by heating benzyl-α- and β-naphthyl ethers with the aromatic compounds, such as, naphthalene, 2-methylnaphthalene and isoquinoline. It has been concluded that the reaction depends initially on homolytic fission of the alkyl aryl ether into aryloxy and alkyl free radicals which are able to react with the aromatic nucleus. The homolytic mechanism of the alkylation studied and the isomer distribution in the alkylation products separated are discussed on bases of theories of free valency and atom localisation energy of aromatic compounds.     

Autoignition mechanism of dimethyl ether–air mixtures in the presence of atomic iron

The search for reactive additives capable of reducing the combustibility of dimethyl ether is an important problem due to the widening use of ether as an alternative environmentally friendly motor fuel. This paper presents a numerical study of the autoignition chemistry of mixtures of dimethyl ether with air in the presence of atomic iron. Atomic iron, which is an effective inhibitor of premixed laminar hydrocarbon flames, was found to shorten the induction period. However, the additive affects only the first stage of the induction period. The mechanism of promotion of the low-temperature oxidation of dimethyl ether–air mixtures by atomic iron is the formation of hydroxyls in reactions involving iron compounds. Since the additive hardly changes the duration of the second stage of the induction period, it can be suggested that OH radicals play an insignificant role in the low-temperature oxidation of dimethyl ether at this stage.     

The influence of stabilizers on mechanochemical processes in SBR rubbers

Mechanochemical processes in commercial and model SBR rubbers containing different stabilizers were investigated. The influence of chemical structure and concentration of stabilizers in the temperature range from 20–170°C and in the presence of air, i.e., under conditions similar to that in industrial processes, were studied. Stabilizers used were diaryl‐p‐phenylene‐diamine, alkyl‐aryl‐p‐phenylene diamine, polynuclear phenol, aryl‐alkyl phenol, and alkyl‐alkyl phenol. It was found that mechanochemical processes in SBR rubbers are less developed in the temperature region from 70–130°C, so the influence of stabilizer is less expressive. During increasing temperature (130–170°C) structure and concentration of stabilizers both show a strong influence on type and intensity of mechanochemical processes in SBR rubbers: p‐phenylene‐diamines favor processes of linear degradation, while phenol stabilizers direct them toward branching and crosslinking, which is more expressed in the presence of aryl‐substituted phenols than alkyl‐substituted phenols. This fact is based on the differences in stability of free stable radicals of p‐phenylene‐diamines, alkyl‐substituted phenols and aryl‐substituted phenols. The fact that phenol stabilizers are involved in chain degradation as well as in branching and crosslinking processes during rubber processing, can be of high practical importance. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 835–847, 1999     

The Characteristics and Reactivity of Acid-Labile Aryl Ether Units in Wood Lignin

Wood lignin contains significant amounts of acid-labile aryl ether units, which play a significant role in lignin modification or delignification processes. We have evaluated the rate and reaction kinetics on the acid-catalyzed cleavages of aryl ether structures for wood lignin in situ based on the formation of phenolic hydroxyl groups. The content of acid-labile aryl ether units was quite uniform for a variety of softwood wood lignins (～4% per C₉ unit) and it varied appreciably among hardwood species, ranging from 4% for aspen to 9% for beech wood lignin. These variations, however, appear to be related to the content of syringyl units in wood lignin. The reactivity of these reactive aryl ether structures was noticeably higher for the spruce than for the aspen wood lignin. This difference in reactivity, based on the behavior of lignin model compound reactions, can be attributed to the influence of syringyl moieties in aspen wood lignin. It appears that most of the acid-labile aryl ether units in hardwood were associated with the syringy moiety being present as a benzyl unit, which is much less reactive than the corresponding guaiacyl moiety.     

Effect of structure of aromatic diamines on curing characteristics,thermal stability,and mechanical properties of epoxy resins. I

The curing behavior of diglycidyl ether of bisphenol-A (DGEBA) with aromatic diamines having aryl–ether, aryl–ether–carbonyl, and aryl–ether–sulfone linkages was studied using differential scanning calorimetry (DSC). Aromatic diaminessuch as 1,3-bis(aminophenoxy)benzene (R), 1,4-bis(aminophenoxy)benzene (H),2,2′-bis[4-(4-aminophenoxy)phenyl]propane (B), 4,4′-bis(4-aminophenoxy)benzo-phenone (P), and bis[4-(4-aminophenoxy)phenyl]sulfone (S) were synthesized and characterized in the laboratory. Curing of DGEBA was done using both stoichiometric and nonstoichiometric amounts of diamines and the reaction was monitored using DSC. The reactivity of the diamines depended on the structure. The presence of electron withdrawing groups, even though significantly apart from the reaction site, reduced the nucleophilicity. No significant change was observed in the activation energy for curing, which was around 56 ± 2 kJ/mol. The glass transition temperature of the epoxy network depended on the structure and was higher when diamines P and S were used in comparison to diamines R, H, and B. The cured resins were stable up to 300°C, and maximum char yield (i.e., 32% at 600°C) was obtained in DGEBA cured with diamine P. The room temperature mechanical properties only changed marginally with the structure of the diamines. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1759–1766, 1998     

Novel polyarylates containing aryl ether units: synthesis,characterization and properties

To improve the processability of the poly(p‐hydroxybenzoic acid), copolyarylates containing m‐aryl ether units were synthesized using p‐acetoxybenzoic acid, 1,4‐diacetoxybenzene and 1,3‐bis(4'‐carboxyphenoxy)benzene by melt transesterification reaction. The structure and properties of these polyarylates were characterized using infrared spectra, differential scanning calorimetry, thermogravimetric analyses, wide‐angle X‐ray diffraction and polarized optical microscopy etc. The results showed that all polyarylates were semicrystalline materials and could form a thermotropic liquid crystalline intermediate state. As the content of aryl ether units increased, the crystallization and melting temperatures of the polyarylate decreased; meanwhile, the crystalline ability became lower. The introduction of the aryl ether could restrain the formation of a liquid crystalline structure and reduce the thermal stability to some extent. After solid state polymerization (SSP), the intrinsic viscosity, melting temperature, crystallinity and thermal stability of the polyarylate increased while the melting range narrowed. However, the SSP reaction might be accompanied by degradation and crosslinking.     

五元氮杂环苯丙烯酸及其类似物的合成

以芳酸酯为起始原料,经过一系列反应,合成了2个三氮唑芳酸醚类衍生物,2个咪唑芳酸醚衍生物,所合成的目标化合物未见文献报道,其结构均经1H-NMR、13C-NMR、MS确证,所设计的合成技术简单易行。     

Miscible blends of poly(aryl ether ketone)s and polyetherimides

A new class of high performance engineering resins, poly(aryl ether ketone)s, has emerged with a property balance not offered by existing polymeric materials. Blends of poly(aryl ether ketone)s with other polymers have not been described in the open literature, although several patents have revealed interesting and important properties of certain blend combinations. Ultem polyetherimide has been found to be miscible over the entire composition range and as a consequence is a very effective heat distortion temperature builder, particularly if the poly(aryl ether ketone) is allowed to crystallize. Crystallization kinetics and mechanical properties were studied as a function of blend composition and poly(aryl ether ketone) melting point. The blends exhibited a maximum in toughness at intermediate compositions along with an accompanying maximum in poly(aryl ether ketone) crystallinity. The chemical resistance of the polyetherimide is significantly improved with the addition of a poly(aryl ether ketone). In organic chemicals, the improvement was expected when tensile stress was plotted vs. log time to rupture. However, in aqueous bases, the resistance of the blends was much greater than anticipated. This property profile suggests that these blends will be useful as thermoplastic composite matrix resins.     

Novel aromatic macrocyclic oligomers: intermediates for the preparation of high-performance polymers

Recent studies aimed at the development of macrocyclic oligomers as the intermediates for the preparation of high-performance polymers are reviewed. Efficient methods for the preparation of a range of cyclic oligomers, such as aryl ether ketones, aryl ether phthalazines, aryl ether isoquinolines, aryl ether phthalazinones, and arylene sulfides, have been developed. Cyclization was achieved via a nucleophilic aromatic substitution reaction under high-dilution conditions. The cyclic aryl ether oligomers undergo a facile ring-opening polymerization to form high molecular weight polymer. Cyclic oligomers containing an aromatic sulfide linkage also undergo a facile free-radical ring-opening polymerization to form high molecular weight polymers which can be amorphous or crystalline. Due to their low molecular weights, these cyclic oligomers have very low melt viscosities which makes them attractive intermediates for a variety of applications for which the conventionally prepared high molecular weight polymers would not be suitable.     

Synthesis and curing behavior of macrocycle‐terminated poly(aryl ether ketone)s

BACKGROUND: The introduction of poly(ether ether ketone)‐based carbon‐fiber composites accelerated the application of poly(ether ether ketone)s in advanced composite materials. In order to improve the compatibility and processability with reinforced components, polymers with low melt viscosity are preferable. RESULTS: Novel fully aromatic macrocycle‐terminated poly(aryl ether ketone)s (MCPAEKs) were prepared by condensation of macrocyclic aryl ether ketone dimers containing hydroxyphenyl groups and fluorine end‐capped poly(aryl ether ketone) oligomers. Compared with liner poly(aryl ether ketone)s, MCPAEKs showed much lower melt viscosities at low temperature. In the presence of caesium fluoride, the crosslinking reaction of MCPAEKs afforded fully aromatic thermoset poly(aryl ether ketone)s by ring‐opening reaction. CONCLUSION: The MCPAEKs exhibited high thermal stability due to their wholly aromatic structures. After crosslinking, the glass transition temperatures and complex melt viscosities of the polymers were increased greatly. Although there was some residual cesium fluoride or phenoxides produced by ring‐opening reaction, the thermoset poly(aryl ether ketone)s obtained had good thermal stability with temperatures at 5% weight loss above 475 °C. Copyright © 2009 Society of Chemical Industry     

Adhesion characteristics of imide-aryl ether ether ketone block copolymers with poly(ether-imide)

Imide-aryl ether ether ketone block copolymers were prepared and the adhesion characteristics with poly(ether-imide) were investigated. The copolymers were prepared via the poly(amic alkyl ester) precursor to the polyimides which is hydrolytically stable and may be isolated and characterized prior to imidization. Solutions of the copolymers were cast and cured to effect the imidization, producing clear tough films which showed two transitions, indicative of a multiphase morphology. Mixtures of the copolymers with poly(ether-imide) also produced clear films, and the shift in the T_g of the aryl ether ether ketone component of the block copolymer indicated miscibility with the poly(ether-imide) within this phase. This miscibility of the poly(ether-imide) with the aryl ether ether ketone component of the block copolymer produced significant improvements in the adhesion of the thermoplastic poly(ether-imide) with the rigid polyimide copolymer.     

191不饱和聚酯胶粘剂的改性研究

不饱和聚酯在固化过程中，由于初级自由基与空气中的氧反应产生的新游离基不能引发聚合，故其表面发粘，为解决此问题，本文选用了烯丙基醚，液体石蜡和碱金属氧化物进行试验，结果表明，烯丙基醚可有效吸收氧气，从而消除氧的阻聚作用，加入了烯丙基醚的191不饱和聚酯，30min可完全固化，表面不发粘。     

Thermal crosslinking behavior of poly (aryl ether ketone) copolymers containing naphthalene moieties

A series of poly[(ether ether ketone)‐co‐(ether naphthalene ether ketone)] (P(EEK‐co‐ENEK)) copolymers were heated under a variety of conditions. The thermal crosslinking behavior was monitored by differential scanning calorimetry (DSC), electron spin resonance (ESR) and wide‐angle X‐ray diffraction (WAXD). The results indicate that under a non‐oxidative environment such as nitrogen P(EEK‐co‐ENEK) is more stable, while under oxidative conditions a crosslinking reaction takes place that causes a reduction in the crystallizability of the copolymers, and an increase in the concentration of free radicals on the copolymer. ESR results suggest that the crosslinking reaction proceeds via free radicals. Subsequently two kinds of free radicals were characterized: one is an RO^? type free radical and the other is a naphthalene ring free radical. Copyright © 2004 Society of Chemical Industry     

含氰侧基联苯型聚芳醚醚酮酮的合成及表征

通过一种反应条件较为温和的反应新工艺,合成联苯二甲酰氯,即4,4’-二氯甲酰基联苯(BC IBP)。然后,在无水A lC l3及N-甲基吡咯烷酮(NMP)/1,2-二氯乙烷(DCE)复合溶剂的存在下,将2,6-二苯氧基苯甲腈(DPOBN)与BC IBP进行低温缩聚反应,合成了一类新型含氰侧基联苯型聚芳醚醚酮酮。用IR,DSC,TG,WAXD及元素分析等方法对其结构和性能进行了表征。结果表明,所合成的聚合物具有预期结构且为非晶态聚合物;其玻璃化转变温度(Tg)为211℃,在氮气气氛中及在空气气氛中的热分解5%的温度(Td)分别为523℃及498℃,说明其具有突出的耐高温性能;聚合物除了能在浓H2SO4,CF3COOH/CHC l3等强质子性溶剂当中溶解外,对其他的溶剂均不溶解,说明聚合物具有优异的耐化学腐蚀性能。