Effect of the fold surface of the lamellae on the behavior of the trapped radicals in irradiated polyamide-1010

Two types of macromolecular free radicals -CH2CONHCHCH2- (a) and -CH2C=O (b) trapped in irradiated Polyamide-1010 (PA1010) and PA1010 filled with neodymium oxide (Nd2O3) were characterized by an ESR approach. It was found out that a was mainly trapped in the fold surface of the lamellae and b in the amorphous phase. This result suggested that trapped radicals mainly existed in the noncrystalline phases. The effect of the fold surface area of the lamellae on the behavior of the trapped radicals are discussed in this article. Whether for the specimens with similar crystallinities but different crystallite sizes or for those with the same concentration of neodymium oxide but different crystallinities, radical a exists dominantly in a specimen with a larger fold surface area of the lamellae. Under a certain circumstance, radical a can transform into radical b for a specimen with a larger fold surface area of the lamellae. It means that the fold surface area of the lamellae plays an important role in the transformation of radical a to b. (C) 1998 John Wiley & Sons, Inc.

Preparation of methyl tert-butyl ether (MTBE) over heteropoly acids immobilized on activated carbon (HPA/C) in the vapor phase

Heteropolyacids (HPAs) supported on the activated carbon (SiW12/C and PW12/C) have been used to study the formation of methyl tert-butyl ether (MTBE). Compared to the conventional commercial catalysts, Amberlyst-15 resin and HZSM-5, HPAs supported catalysts have been proved to have much higher catalytic activity under lower temperature, especially selectivity to MTBE is up to 100%. It may be due to the high acid strength of HPAs as well as the specialty of heteropolyanion.

Poly(ethylene glycol) block poly(butyl acrylate) .1. Synthesis

Prepolymers of poly(ethylene oxide) (Pre-PEG) were synthesized by reacting azoisobutyronitrile (AIBN) with poly(ethylene glycol) (PEG), and their structures were characterized by IR and UV. The molecular weight of pre-PEG was related to the feed ratio and reaction time. These prepolymers can be used to prepare block copolymers - poly(ethylene oxide)-block-poly(butyl acrylate) (PEO-b-PBA) by radical polymerization in the presence of butyl acrylate (BA). Solution polymerization was a suitable technique for this step. The yield and the molecular weight of the product were related to the ratio of the prepolymer to BA, the reaction time, and temperature. GPC showed that the molecular weight increased with a higher ratio of BA to pre-PEO. The intrinsic viscosity of the copolymers was only slightly dependent on reaction time, but decreased at higher reaction temperatures, as did the amount of PEA homopolymer. (C) 1997 John Wiley & Sons, Inc.

ESR approach to free radicals trapped in irradiated polyamide-1010

Two types of macromolecular free radicals similar to CH2CONH(C) over dotHCH(2) similar to (a) and similar to CH2(C) over dot = O (b) trapped in irradiated polyamide-1010 (PA1010) and PA1010 filled with neodymium oxide (Nd2O3) were characterized by an ESR approach. It is found that (a) is prevailingly trapped in the fold surface of the lamellae and (b) in the amorphous phase. This result suggests that trapped radicals mainly exist in the non-crystalline phases. The effect of the fold surface area of the lamellae on the behavior of the trapped radicals is discussed in this paper. Whether for the specimens with similar crystallinities, but different crystallite sizes, or for those with the same concentration of neodymium oxide, but different crystallinities, radical (a) exists dominantly in the specimen with a larger fold surface area of the lamellae. Under certain circumstances, radical (a) can transform into radical (b), obviously for a specimen with a larger fold surface area of the lamellae. It means that the fold surface area of the lamellae plays an important role in the transformation of radical (a) to (b). (C) 1997 Elsevier Science Ltd.

An effective etching technique for polycarbonate/core-shell poly(butyl acrylate) poly(methyl methacrylate) blend

Two etching techniques are used to reveal the morphology of PC/PBA-cs-PMMA blend. One is based on acetic acid (CH3COOH) solutions, whereas the other uses CCl4/ C2H5OH (3/1 v/v). The latter approach shows to be more appropriate and successful for revealing the morphology of PC/PBA-cs-PMMA blend.

Dependence of decaying of trapped radicals on aggregates on polyamide 1010

The decaying of free radicals in the course of heating, trapped in irradiated polyamide 1010 with different crystallinities, were investigated using an ESR technique. The decaying temperature, at which all radicals decay completely, depends on the aggregation of polyamide 1010 prior to radiation. The higher the crystallinity, the higher the temperature at which the radicals disappear. Dynamically speaking, radicals in specimens with higher crystallinity take longer to decay. (C) 1997 Elsevier Science Ltd.

Preparation and characterization of ethylene-propylene copolymer grafted with acrylamido tertiary butyl sulfonic acid

Grafting of acrylamido tertiary butyl sulfonic acid (ATBS) onto ethylene-polypropylene copolymer (EPM) was carried out by using a reactive processing method. The grafting copolymer was characterized by means of WAXD, FT-IR, ESCA, and DSC. Improved thermal stability was observed for graft copolymer. Effects of the monomer and the initiator concentrations, reactive temperature, and time on grafting degree were investigated. (C) 1997 John Wiley & Sons, Inc.

An ESR study on (OH)-O-center dot-radical scavenging activity of water-soluble fullerenols

Water-soluble polyhydroxylated fullerene derivatives (fullerenol) were synthesized, and their scavenging ability for (OH)-O-.-radical was studied by the combination of ESR spectroscopy and spin-trapping technique with phenyl-t-butyl-nitrone. It was found that fullerenols showed an excellent efficiency in eliminating (OH)-O-. free radicals generated by UV photolysis of H2O2. At an applied fullerenol concentration of 0, 3 mg/mL in the final solution, a radical scavenging efficiency of approximate 95% was achieved, revealing the potential use of these compounds as novel potent free radical scavengers in biological systems.

POLYMERIZATION OF ACRYLONITRILE INITIATED BY DI(2,6-DI-TERT-BUTYL-4-METHYLPHENOXO) SAMARIUM COMPLEX

The polymerization of acrylonitrile initiated by organolanthanide complexes alone is studied for the first time. The effect df polymerization conditions on catalytic activity of the title complex and molecular weight of the polymers produced have been studied.

A BIS(2,6-DI-TERT-BUTYL-4-METHYLPHENOLATO)-SAMARIUM(II) COMPLEX, [SM(OAR)2(THF)3]-THF

The title complex, bis(2,6-di-tert-butyl-4-methyl-phenolato-O)tris(tetrahydrofuran-O)samarium tetrahydrofuran solvate, [Sm(C15H23O)2(C4H8O)3].C4H8O, has distorted trigonal bipyramidal geometry around the Sm(II) atom. The 0(2), 0(3) and 0(4) atoms of the

Synthesis and hydroxyl radicals scavenging activity of quaternized carboxymethyl chitosan

In order to determine the effect of the forms of the amido groups of chitosan on antioxidant activity, quaternized carboxymethyl chitosan (QCMC) derivatives were prepared with a degree of quaternization ranging from 34.3% to 59.5%. The antioxidant activity of QCMCs against hydroxyl radicals was assessed. The results indicated that QCMCs have better hydroxyl radicals scavenging activity than that of carboxymethyl chitosan, as a result of the positive charge of the quaternized chitosan. (C) 2007 Elsevier Ltd. All rights reserved.

Hydroxyl radicals scavenging activity of N-substituted chitosan and quaternized chitosan

N-substituted chitosan and quaternized chitosan were synthesized and their antioxidant activity against hydroxyl radicals was assessed, respectively. Compared with the antioxidant activity of chitosan, the results indicated that the two kinds of chitosan derivatives had different scavenging ability on hydroxyl radicals, which should be related to the form of amido in the two kinds of chitosan derivatives. (c) 2006 Elsevier Ltd. All rights reserved.

Shock tube study of JP-10 ignition delay time

JP-10 (exo-tetrahydrodicyclopentadiene, C10H16) ignition delay times were measured in a preheated shock tube. The vapor pressures of the JP-10 were measured directly by using a high-precision vacuum gauge, to remedy the difficulty in determining the gaseous concentrations of heavy hydrocarbon fuel arising from the adsorption on the wall in shock tube experiments. The whole variation of pressure and emission of the OH or CH radicals were observed in the ignition process by a pressure transducer and a photomultiplier with a monochromator. The emission of the OH or CH radicals was used to identify the time to ignition. Experiments were performed over the pressure range of 151-556 kPa, temperature range of 1000-2100 K, fuel concentrations of 0.1%-0.55% mole fraction, and stoichiometric ratios of 0.25, 0.5, 1.0 and 2.0. The experimental results show that for the lower and higher temperature ranges, there are different dependency relationships of the ignition time on the temperature and the concentrations of JP-10 and oxygen.

苯乙烯/丙烯酸正丁酯/丙烯酸共聚微球的制备及其性能表征

通过乳液聚合法和无皂乳液聚合法制备了苯乙烯/丙烯酸正丁酯/丙烯酸共聚微球.讨论了乳化剂用量、引发剂用量、功能单体、软硬单体用量比等对微球粒径和形态的影响.利用扫描电子显微镜(SEM)、傅立叶变换红外光谱仪(FTIR)对微球的粒径、形貌和表面基团进行分析.红外光谱表明,实验室所制备的苯乙烯/丙烯酸正丁酯/丙烯酸共聚微球表面存在丰富的羧基.利用竖片生长法得到自组装的多层胶体微球薄膜.通过对薄膜的反射光谱测量,发现随着湿度的增加,峰位会产生3nm左右的红移.