Compatibilizing effects and mechanism of compatibilization of LLDPE/PEO blends by EAA

The compatibilizing effects of the compatibilizer, ethylene-acrylic acid random copolymer (EAA), on linear low density polyethylene (LLDPE)/poly(ethylene oxide) (PEO) blends and the mechanism of compatibilization of the blends have been studied. Morphology and microstructures as characterized by SEM, DMA, DSC and IR show that EAA can act as an effective compatibilizer, and the mechanism of compatibilization is due to the compatibility of amorphous phases between EAA and LLDPE, and intermolecular interaction between the carboxylic groups in EAA. and the ethereal oxygens in PEG.

Deformation process and mechanism of HDPE/LDPE blends

Blends of HDPE in more LDPE, with appropriate heat treatment, produce a dispersion of separate entities of HDPE in a matrix of LDPE. The system offered an especially favourable means of studying the deformation of melt-crystallized lamellae. It has been found that sheaf-like spherulites are transformed under tensile deformation into hourglass shapes i.e. a double cone aligned along the drawing direction with origin in the center of the object. This is a consequence of different modes of deformation according to the relation of an individual lamella to the tensile axis. The work shows that the lamellae have not undergone melting and recrystallization in the deformation process at room temperature.

Investigation of mechanism of nephelauxetic effect

By using the chemical bond theory of dielectric description and electronic structure of 3d elements, the mechanism of nephelauxetic effect is studied, and the main factors responsible for this effect are identified. These are: the covalency of chemical bond, polarizabilities of ligand bond volume for the host and the valence and spin state of the center ion. Relationships between these factors are given, and the results are discussed. (C) 1996 Elsevier Science Ltd. All rights reserved.

Crystal structure and mechanism of (Z)-1-[2-(phenyl-bromide-chloride)vinyl]-1-cyclohexanol

The crystal structure and mechanism of the title molecule are described. This crystal is orthorhombic, belonging to space group PC21/B with a=1,002 1(2) nm, b=1.483 0(3) nm, c=2.173 6(4) nm, V=3.230 39(2) nm(3), Z=2, D-c=1.80 g/cm(3), R=0.069 3. The structure was solved by direct method. The tin atom of the title compound exists in two distorted-trigonal-bipyramidal geometry, defined by two carbon, one bromide, one chloride and one oxygen atoms leading to a five-membered chelate ring. In the structure, the five-membered ring containing the intermolecular O-->Sn has a half chair conformation.

Studies of catalyzed reaction mechanism between co-polyether (THF/EO) and N-100 by NMR - Interaction and complex formation between reactants and catalysts

To elucidate the mechanism of the catalyzed reaction of co-polyether (EO/THF) with N-100, the interaction and complex formation between reactants and catalysts were investigated by means of NMR spectroscopy. It is shown that the resonance peak of isocyanate carbon splits into two parts when the solutions of N-100 and co-polyether were mixed. The disappearing of proton resonance peak of hydroxyl group in NMR spectra when dibutyltin dilaurate(DBTDL) were added to the copolyether(THF/EO) solution indicates the complex formation, This interaction appears to be a bonding of tin to the oxygen of hydroxyl and make the hydrogen of the hydroxyl group very mobile and active, then exchange with other protons, In the case of triphenyl bismuth(TPB), the high field shift and intensity enhancement of proton peak were observed, which suggest a nucleophilic attack of the bismuth to the hydroxyl hydrogen.

Iron(II)-8-quinolinol/MCM-41-catalyzed phenol hydroxylation and reaction mechanism

Iron(II)-8-quinolino/MCM-41 is prepared. Its catalysis is studied in phenol hydroxylation using H2O2 (30%) as oxidant. The experiment shows that Iron(II)-8-quinolinol/MCM-41 has good catalytic activity and desired stability. Based on cyclic voltammetry, ESR, and UV-visible spectra studies of iron(II)-8-quinolinol complex in liquid phase, a radical substitution mechanism is proposed and used to demonstrate the experimental facts clearly. (C) 1997 Academic Press.

Study on the beta relaxation mechanism of thermosetting polyimide thermoplastic polyimide blends

The thermosetting polyimide PMR-I5 and its blends with thermoplastic polyimides have been studied by dynamic mechanical analysis. The results obtained indicate that the level of beta relaxations in PMR-15 are increased with an increase in cross-linking density. This phenomenon is interpreted as a change of chemical structure during the cross-linking process. Addition of thermoplastic polyimide makes the magnitude of beta relaxations increase when PMR-15 is the major component. This might be due to the strong intermolecular charge-transfer interaction between PI and PI or PMR-15 and PMR-15 molecular chains being partly replaced by the weak intermolecular interaction between PI and PMR-15 in PMR-15/PI blends, resulting in some phenylene rings or imide groups in PIs and PMR-15 chains being able to participate in beta relaxation. However, this increment in beta relaxation magnitude can be reduced by heat treatment of the sample, as a result of phase separation. Hence, it is concluded that the beta relaxation magnitude is determined by the number of groups which can participate in relaxation per unit length, i.e. the magnitude of beta relaxation increases with decreasing interaction between the molecular chains. Copyright (C) 1996 Elsevier Science Ltd

Phenol hydroxylation by iron(II) phenanthroline: The reaction mechanism

Phenol hydroxylation catalyzed by iron(II)-1,10-phenanthroline is investigated through kinetics, ESR, W-Vis as well as cyclic voltammogram studies. The optimum reaction conditions are obtained for diphenols production. Radical substitution mechanism is first proposed to explain the effects of pH, reaction medium and other factors on the phenol hydroxylation with H2O2 as oxidant, and found that the coexisting of iron(II)-1,10-phenanthroline and iron(III)-1,10-phenanthroline is the key for phenol hydroxylation to occur with H2O2 as oxygen donor.

Synthesis and thermo-decomposition mechanism of rare earth complexes with phenylacetic acid

Rare earth complexes with phenylacetic acid (LnL(3) . nH(2)O, Ln is Ce, Nd, Pr, Ho, Er, Yb and Y, L is phenylacetate, n = 1-2) were prepared and characterized by elemental analysis, IR spectroscopy, chemical analysis, and X-ray crystal structure. The mechanism of thermal decomposition of the complexes was studied by means of TG-DTG, DTA and DSC. The activation energy and enthalpy change for the dehydration and melting processes were determined.

Plastic zone in front of mode I crack in phenolphthalein polyether ketone

The plastic zone size and crack opening displacement of phenolphthalein polyether ketone (PEK-C) at various conditions were investigated. Both of them increase with increasing temperature (decreasing strain rate), i.e. yield stress steadily falls. Thus, the mechanism increasing the yield stress leads to increased constraint in the crack tip and a corresponding reduction in the crack opening displacement and the plastic deformation zone. The effect of the plastic deformation on the fracture toughness is also discussed.

Effect of physical aging on phenolphthalein polyethersulfone/poly(phenylene sulfide) blend .1. Mechanical properties

The effect of physical aging at 210 degrees C on the mechanical properties of phenolphthalein polyether sulfone (PES-C) and a PES-C/poly(phenylene sulfide) (PPS) blend, with 5% content of PPS, were studied using DMA, tensile experiments, an instrumented impact tester, and SEM observations. The blend shows good mechanical properties in comparison with the corresponding PES-C. The mechanical properties of both materials exhibit characteristics of physical aging, with only the aging rate of the blend relatively slower, which should be attributed to the constraint effect of PPS particles and the good interfacial adhesion. The morphology of the PPS phase in the blend did not change with aging time. The principal role of PPS particles is to induce crazes, which dissipate energy, under applied loading; thus, the blend shows good toughness. On the other hand, the multiple crazing mechanism depends on the molecular mobility or structural state of the matrix. (C) 1996 John Wiley & Sons, Inc.

MECHANISM OF IRON INHIBITION BY STEARIC-ACID LANGMUIR-BLODGETT MONOLAYERS

Using the Langmuir-Blodgett (LB) technique, stearic acid (SA) monolayers were deposited onto the surface of an iron (Fe) electrode to study the inhibition effect and the mechanism of SA in a neutral medium. Molecular orientation and the number of deposited monolayers of SA were shown to have marked effects on inhibition of Fe corrosion. The inhibition mechanism depended mainly on blocking.

FRACTURE-TOUGHNESS OF PHENOLPHTHALEIN POLYETHER KETONE

The static and impact fracture toughness of phenolphthalein polyether ketone (PEK-C) were studied at different temperatures. The static fracture toughness of PEK-C was evaluated via the linear elastic fracture mechanics (LEFM) and the J-integral analysis. Impact fracture toughness was also analyzed using the LEFM approach. Temperature and strain rate effects on the fracture toughness were also studied. The enhancement in static fracture toughness at 70 degrees C was thought to be caused by plastic crack tip blunting. The increase in impact fracture toughness with temperature was attributed two different mechanisms, namely, the relaxation process in a relatively low temperature and thermal blunting of the crack tip at higher temperature. The temperature-dependent fracture toughness data obtained in static tests could be horizontally shifted to match roughly the data for impact tests, indicating the existence of a time-temperature equivalence relationship. (C) 1995 John Wiley & Sons, Inc.

MECHANICAL-PROPERTIES OF PHENOLPHTHALEIN POLYETHER KETONE - YIELD STRESS, YOUNGS MODULUS, AND FRACTURE-TOUGHNESS

A series of tensile and three-point bending studies was conducted at various temperatures and loading rates using phenolphthalein polyether ketone (PEK-C). Yield stress, Young's modulus, fracture toughness, and crack opening displacement data were obtained for various conditions. In general, both yield stress and Young's modulus increase with decreasing temperature. However, the relationships between fracture toughness, loading rate, and temperature are very complex. This behavior is due to the simultaneous intersection of viscoelasticity and localized plastic deformation. The increased yield stress is the main factor contributing to the reduction in fracture toughness and crack opening displacement. The relationship between fracture toughness and yield stress are discussed. (C) 1995 John Wiley and Sons, Inc.