Stabilisation of EPDM at high temperatures by polymer-bound antioxidants: Part 1—Air oven ageing: Stress relaxation and mechanical property change

EPDM modified by adduct formation using mercaptoacetamido diphenylamine (MADA) and mercaptopropionamido diphenylamine (MPDA) has been evaluated in a heat ageing (air oven) test at 150°C and 180°C by stress relaxation and physical property change. Both antioxidants were found to be more effective than conventional heat ageing antioxidants under these conditions and MADA-B is more effective at 1% than a commercial oligomeric arylamine (Flectol H) at 2%. Vulcanisation characteristics are also reported and it is concluded that by-products formed from MADA during binding interfere to some extent with the curing process and with antioxidant performance.     

一种新型硅藻土填充橡胶纳米复合材料研究

橡胶的填料问题一直是人们的研究热点,针对炭黑和白炭黑在橡胶生产中存在的污染问题,本文选用成分结构与白炭黑类似的硅藻土来填充各种橡胶。首先对硅藻土进行了改性,并对不同改性剂改性硅藻土用于填充橡胶进行了研究。结果表明2.5份偶联剂Si69的改性效果最佳。通过机械共混法制备了改性硅藻土/橡胶纳米复合材料,通过力学性能测试确定了比较适合硅藻土填充的橡胶是氟橡胶、三元乙丙橡胶和丙烯酸酯橡胶。绿色环保且价格低廉的硅藻土可以替代白炭黑增强填充氟橡胶、三元乙丙橡胶和丙烯酸酯橡胶。     

Thermal behavior of some polyurethanes reticulated by aminated maltose

Polymeric materials by polyaddition reaction between aminated maltose and methylene diisocyanate, in different molar ratio, were synthesized. Aminated maltose was obtained by functionalization at the reductive end with methylene dianiline, under soft reductive conditions. The addition reaction was certified by comparative FTIR and Raman spectra of reactants and obtained materials. The thermooxidative stability of these materials was established under non-isothermal conditions. The thermal stability decreases by increasing the isocyanate/aminated maltose molar ratio.     

Influence of cryogenic modification of silica on thermal properties and flammability of cross-linked nitrile rubber

The article presents the results of testing thermal properties and combustibility of butadieneacrylonitrile rubber with 18% contents of bounded acrylonitrile, NBR 18. Two types of silica, Zeosil 175C and Ultrasil VN-3, with different specific surfaces were used as filler. Zeosil 175C and Ultrasil VN-3 were modified via cryogenic dezaggregation method. The activity of unmodified and cryogenic modified silica toward butadiene-acrylonitrile rubber were investigated. The sulphur and peroxide vulcanizates contained 20, 30, 40, and 50 phr. of the filler were studied. The article discusses also the test results of thermal stability and flammability of NBR 18 containing silica prepared "in situ" from alkoxysilane precursor. The test results were obtained with the use of derivatograph, measurements of flammability by the method of oxygen index, and in air. The effect of the silica modification on the SEM and AFM was also examined. The method of cryogenic modification enables to achieve increase of mineral fillers activity towards elastomer and reduction in the flammability of NBR 18 vulcanizates. It has been found that the modification of the vulcanizates of NBR 18 with tetraethoxysilane that makes it possible to form silica "in situ" reduces the flammability of cross-linked rubbers.     

Influence of surface modification on thermal stability and flammability of cross-linked rubbers

The paper discusses the test results of thermal stability and flammability of cross-linked diene rubbers containing silica prepared “in situ” from alkoxysilane precursors. The effect of the surface modification of unfilled vulcanizates by means of aqueous solutions of halogens, boron and organo-phosphoric compounds on their flammability was also assessed. The thermal analysis has been performed in air with the use of derivatography. The flammability of vulcanizates has been determined by the method of oxygen index and in air. It has been found that the modification of the vulcanizates with tetraethoxysilane that makes it possible to form silica “in situ” considerably reduces the flammability of cross-linked rubbers. The surface modification of the vulcanizates with halide and organo-phosphoric compounds allows one to radically decrease their flammability. The boric flame-retardant agents are the most effective modifiers. The most beneficial results were obtained with the use of boric acid.     

Thermal, oxidative and radiation stability of polyimides. Part IV: Polyimides based on N-[4-benzoyl-2-(2,5-dioxo-2,5-dihydro-pyrrol-1-yl)-phenyl]-acetamide and different diamines

Polyimide resins were obtained from the reaction between N-[4-benzoyl-2-(2,5-dioxo-2,5-dihydro-pyrrol-1-yl)-phenyl]-acetamide and the following compounds with terminal amino groups: urea, 4-[(4-aminophenyl)sulfonyl]aniline, thiourea, 2-aminoethylamine, and 4,4′-diaminodiphenylmethane. The thermal and thermooxidative behaviour of the polyimide resins was studied by thermogravimetric measurements (TG) in oxygen and nitrogen. Polyimide resins have been irradiated (500 kGy) and their radiation stability evaluated on the basis of thermal and thermooxidative behaviour of irradiated samples.The thermal and oxidative degradation of the examined polyimides is complex and occurs in two phases. The first step occurs in both nitrogen and oxygen but it is somewhat less pronounced in oxygen due to oxidation and formation of more stable products. All samples showed very good radiation stability and there is almost no change in the first degradation step while the span of the peaks in the second step is narrowed and temperatures are slightly lower.     

Polymer blends based on an epoxy-amine thermoset and a thermoplastic

The effect of thermoplastic modification of an epoxy-amine system on the cure reaction, miscibility and thermal stability of the system was investigated. The cure kinetics showed an autocatalytic behavior. Modifier did not affect either the total reaction heat or the achieved maximum conversion but delayed the kinetics. The model of Horie-Kamal corrected by diffusion factor was used to adjust kinetics in the whole range of conversions. The modified systems showed two glass transitions indicating two separated phases, whose compositions were estimated using the Fox and Couchman equations. Modifier did not affect the thermal and thermooxidative stability of the system.     

Phthalocyanine polymers. I. Poly[2,2′-(4,4′,4″-,4‴-metal phthalocyanino)-5,5′-bibenzimidazoles] as new high temperature resistant polymers

A novel class of poly(metal phthalocyanino) benzimidazoles were prepared by the condensation reaction between metal (Cu, Co, and Zn), 4,4′,4″,4?-tetracarboxyphthalocyanine, and 3,3′-diaminobenzidine. The reaction was investigated by melt and solution condensation methods. These polymers showed excellent thermal and thermooxidative stability and are noteworthy for their high char yield (86–90%) at 800°C in an anerobic atmosphere. Elemental analyses, spectra, and TGA studies were used to characterize these materials. Isothermal gravimetric analyses were carried out to determine their long-term thermal stability.     

Preparation of Functional Long-Subchain Hyperbranched Polystyrenes via Post-polymerization Modification: Study on the Critical Role of Chemical Stability of Branching Linkage

Post-polymerization modification (PPM) is one of the most powerful strategy for preparing polymers with functional groups that cannot be synthesized by direct polymerization. So far, numerous experimental efforts have been devoted to the stability issue of monomer structures during the PPM process, but little attention was paid to chemical linkages. However, for hyperbranched polymers, a minor change of linkage unit could lead to a significant influence on the overall stability and performance of polymer materials. In this work, we investigated the chemical stability of long-subchain hyperbranched polystyrenes with ester, aryl ether, and carbon-carbon bonds as branching linkages under a few most popular PPM conditions, including NaOH hydrolysis reaction, TFA-promoted hydrolysis reaction, BBr₃-catalyzed methoxy-hydroxyl conversion reaction, and LiAlH₄ carbonyl reduction reaction. Related results are summarized into a synthetic route map that can provide practical and intuitive guidance for preparing functional long-subchain hyperbranched polystyrenes and other type of polymers by PPM for future applications.     

NBR/CuSO4混合物的非液相配位交联反应

采用示差扫描量热法(DSC),变温傅立叶转变红外光谱(FT-IR)和X射线光电子能谱(XPS)研究了丁腈橡胶/硫酸铜(NBR/CuSO4)混合物的非液相(聚合物熔融态)配位交联反应.DSC曲线上出现了多个放热峰,并随升温速率提高,峰值一致向高温方向移动;结合XPS和FT-IR的分析表明DSC曲线上的第一个放热峰对应于混合物中发生的铜离子与腈基的非液相配位反应;同时采用非等温法(Kissinger法)及Crane方程计算了NBR/CuSO4混合物非液相配位交联反应的表观活化能和反应级数.     

Thermal and environmental stability of poly(4-ethynyl-p-xylylene-co-p-xylylene) thin films

The aim of this paper was to test the thermal and environmental stability of poly(4-ethynyl-p-xylyleneco-p-xylylene) thin films prepared by chemical vapor deposition(CVD) and to optimize the reaction conditions of the polymer.Fourier transformed infrared spectroscopy(FTIR),thermogravimetric analysis(TGA) and fluorescence microscopy were employed to investigate the stability of the reactive polymer coatings in various environmental conditions.Chemical reactivity of the thin films were then tested by Huisgen 1,3-dipolar cycloaddition reaction(‘‘click' reaction).The alkyne functional groups on poly(4-ethynyl-p-xylylene-co-p-xylylene) thin films were found to be stable under ambient storage conditions and thermally stable up to 100 8C when annealed at 0.08 Torr in argon.We also optimized the click reaction conditions of azide-functionalized molecules with poly(4-ethynyl-p-xylylene-co-p-xylylene).The best reaction result was achieved,when copper concentration was 0.5 mmol/L,sodium ascorbate concentration to copper concentration was 5:1.In contrast,the azide concentration and temperature had no obvious effect on the surface reaction.     

Synthesis and Properties of Copolymers Having Polyconjugated Blocks in the Macromolecules. III Thermal Behavior of Polyisoprene-Containing Polyazophenylene Fragments in the Main Chains

The thermal and thermooxidative stability of polyisoprene containing polyazophenylene fragments of different composition was investigated. Elevated inhibiting activity of polyazophenylene -methane fragments was found to be caused by the intramolecular synergism due to the combination of the reaction of peroxy radicals with mobile hydrogen atoms of methylene bridge groups and decomposition of hydroperoxides under the influence of polyconjugated blocks.     

Synthesis and thermooxidative stability of poly[1,4-phenylene-4,4′-(2,2,2-trifluoro-1-phenylethylidene)bisphthalimide] and other fluorinated polyimides

The synthesis of a novel polyimide (3F-PDA) derived from 4,4′-(2,2,2-trifluoro-1-phenylethylidene]bisphthalic acid anhydride or its diethyl ester and p-phenylene diamine is described. This material shows unique thermooxidative stability compared with commercially available state-of-the-art polyimides. The optimum monomer stoichiometric ratios of diester to diamine to form a stable 3F-PDA polyimide were investigated. The studies revealed that diester/diamine ratios greater than 1.000 exhibited the greatest resistance to thermooxidative stability at 371°C in 1 atm of circulating air and at 371°C in 4 atm of flowing air. © 1993 John Wiley & Sons, Inc.     

The physicochemical properties of complexones,tetrapyridylporphin derivatives

We synthesized complexones based on tetrapyridylporphin (I), namely, tetra(pyridinium-4-N-carboxymethylene) porphin tetrachloride (II), tetra(pyridinium-4-N-carboxymethylene)porphin tetrabromide (III), complete ethyl ester of (pyridinium-4-N-carboxymethylene)porphin tetrachloride (IV), and tetra(pyridinium- 4-N-methyl)porphin tetraiodide (V). Data on the electronic absorption spectra of the compounds, the enthalpies of their solution in water, and the enthalpies of complex formation with copper(II) and zinc acetates were obtained, and the acid properties of the ligands and their stability under thermooxidative destruction conditions were studied. The conclusion was drawn that the enthalpy of solution of complexone-porphyrins in water was determined by the strength of their crystal lattices and, when different anions (Cl^?, Br^?, and I^?) were present, by the difference of the enthalpies of their hydration. As distinct from Cu²⁺, complex formation between Zn²⁺ and porphyrin ligands occurred with sensible energy expenditures likely caused by the electronic inconsistency between the zinc cation and porphyrin ligands. The stability of water-soluble porphyrins to thermooxidative destruction was limited by temperatures of 200–260°C.     

Multidimensional benzobisoxazole rigid-rod polymers. I. Preparation and characterization

Two- and three-dimensional rigid-rod polymers containing benzobisoxazole structures were prepared through the polycondensation in polyphosphoric acid of 4-[5-amino-6-hydroxybenzoxazol-2-yl]benzoic acid (ABA) with trimesic acid and 1,3,5,7-tetrakis(4-carboxylatophenyl)adamantane, respectively. Thermal properties of the polymers were determined by differential scanning calorimetry, thermogravimetric/mass spectral analysis, and isothermal aging studies. The multidimensional polymers exhibited lower solution viscosities and lower thermooxidative stabilities than the one-dimensional polymer generated by the homopolymerization of ABA under identical reaction conditions. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3451–3456, 1997     

Polyimides containing carbonyl and ether connecting groups. II

In a continuation of our effort on polyimides containing carbonyl and ether connecting groups between aromatic rings, several new polyimides were prepared and characterized. A few of these polymers were semi-crystalline. Glass transition temperatures ranged from 164 to 258°C and crystalline melt temperatures were observed between 350 and 424°C. The semi-crystalline polyimide from the reaction of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 1,3-bis(4-aminophenoxy-4′-benzoyl)benzene provided transparent orange films with excellent tensile properties, exceptional resistance to solvents and strong base, and high thermooxidative stability. In addition, this polyimide provided excellent adhesive strength for joining titanium (6A1–4V) to titanium.     

双烯烃橡胶复分解-加氢制备端羧基聚烯烃

采用烯烃复分解法,以双烯烃橡胶为原料,在Grubbs II代催化剂和链转移剂(马来酸)的作用下制得相应的端羧基聚二烯烃,通过对甲苯磺酰肼/三正丙胺试剂对其进一步加氢得到端羧基聚烯烃.主要研究了反应时间、反应温度、橡胶中双键/催化剂摩尔比、橡胶中双键/链转移剂摩尔比等因素对产物分子量及分子量分布的影响.通过核磁共振氢谱(1H-NMR)和碳谱(13C-NMR)、红外光谱(FTIR)、凝胶渗透色谱仪(GPC)、热重分析(TGA)和示差扫描量热分析(DSC)对产物的结构和性能进行了测试表征.结果表明,通过调整橡胶中双键/催化剂的摩尔比或橡胶中双键/链转移剂的摩尔比可以调控产物的分子量.另外,采用该方法制得的端羧基聚丁二烯具有较高的反式1,4-结构含量,与原料相比其顺式1,4-结构含量大幅下降,从而对产物的性能产生一定影响;而以异戊橡胶为原料时并没有观察到该现象.端羧基聚二烯烃经加氢反应后转变成端羧基聚烯烃,具有更好的热稳定性.该方法合成步骤简单,产物分子量可控,为功能材料的制备提供了新的可能.     

Thermal stability and combustibility of rubbers and sealing plates

The present paper describes the test results concerning the thermal properties and flammability of the selected sealing plates and rubbers that may become components of plates. The thermal analysis methods (DTA, DSC, TG, and DTG) and flammability methods (OI, rate of burning in air, and ignition temperature) were used in this study. The thermal analysis of plates was also performed under isothermal conditions. It was stated that investigated sealing plates belong to the group of flame-retardant materials and type of rubber included in plate influences its thermal stability and combustibility.     

Polyamides incorporating phosphine oxide groups. I. Wholly aromatic polymers

Five novel polyamides incorporating phosphine oxide groups have been synthesized by the condensation reaction of bis(4-carboxyphenyl)phenylphosphine oxide with a series of aromatic diamines. The thermal properties of these polymers were investigated by differential scanning calorimetry and thermogravimetric analysis. Glass transition temperatures in the 225–254°C range were recorded, together with good thermooxidative stability (5% weight loss occurring at >420°C) and high char yield upon prolonged heating at 650–800°C (24–50%). Also, good solubility in aprotic polar solvents was observed for all polyamides synthesized. © 1996 John Wiley & Sons, Inc.     

Thermooxidative decomposition of oil shales

The thermooxidative decomposition of four oil shale samples from Estonia, Jordan, Israel and Morocco and one sample of Estonian oil shale derivative, semicoke, was studied with the aim to determine the characteristics of the process and the differences of it related to the origin of oil shale. The experiments with a Setaram Setsys 1750 thermoanalyzer coupled to a Nicolet 380 FTIR Spectrometer were carried out under non-isothermal conditions up to 1000 °C at the heating rates of 1, 2, 5, 10 and 20 °C min⁻¹ in an oxidizing atmosphere. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman was used to calculate the kinetic parameters. The results of TG–DTA–FTIR analyses and the variation of activation energy E along the reaction progress α indicated the complex character of thermooxidative decomposition of oil shale and semicoke, being at that the most complicated for Estonian and Jordanian oil shale characterized by higher content of organic matter as compared to the other samples studied.