Some investigations on new polyphosphates by the anion-exchange method

The structure of the pentamer (a new P-P bonded phosphate) produced by the hydrolysis of dodecaoxohexaphosphoric(III) acid (ring hexamer) has been examined by an anion-exchange distribution method after complex formation with copper(II) and found to be HPO(OH)PO(OH)PO(OH)PO(OH)PO(OH)H. The hexamer and pentamer salts of these P-P bonded linear phosphorus anions have been prepared. The yield of each species was about 1 mole% of the parent material.     

Some rheological properties of molten polypropylene

The following measurements were carried out on the melts of two samples of polypropylene, one with a narrow and one with a broad molecular weight distribution: viscosity in steady shear flow, dynamic storage and loss moduli, total normal thrust in cone-and-plate apparatus, and flow birefringence. The validity of various theoretical interrelations between the measured quantities is checked. The influence of molecular weight distribution is qualitatively discussed.     

Some important factors which influence the photo-oxidation of polypropylene

The influence of bromination, treatment with sulphur dioxide and light filtration on the rate of photo-oxidation of unstabilised polypropylene film has been examined using infra-red and derivative ultraviolet-visible absorption spectroscopic techniques. Whilst bromination removes unsaturation and sensitises polymer photo-oxidation, sulphur dioxide treatment stabilises the polymer, probably by destroying hydroperoxides. Removal of infra-red radiation extends the induction period prior to carbonyl formation while removal of light wavelengths <370nm extends the induction period by a factor of at least 10. These results lead to some important conclusions about the mechanisms of polypropylene photo-oxidation.     

Some effects of melt-induced orientation on drawing of polypropylene monofilaments

Morphological changes accompanying the deformation of polypropylene filaments with varying degrees of melt-induced orientation are examined using wide-angle x-ray scattering (WAXS), small-angle x-ray scattering (SAXS), and electron microscopy, and their behavior is compared both to completely unoriented film samples and to very highly oriented, hard elastic filaments. Melt-oriented filaments are shown to deform predominantly by a voiding mechanism at low temperatures (<100°C), and destruction of the lamellas to produce fibrils occurs only after extensive drawing. The bimodal crystal texture of the filaments does not appear to greatly affect the low temperature deformation mechanism. High temperature (>100°C) drawing produces a fibrillar structure containing elongated voids.     

Some investigations on stability and precision of an HR-ICP-MS

Over a period of 4 months long- and short time stability (precision) of a high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) was investigated using an ELEMENT (Finnigan MAT, Germany) instrument. By using a special torch design, significant improvements could be achieved. Without changing any electrical parameters of the mass spectrometer, the long time stability over a time period of 4 months was measured as about ± 15% for ¹¹⁵In for all three steps of resolution (300, 3000, 7500). The short time stability over a period of 2–8 h was measured as about ± 10% (at maximum), also nearly independent of the resolution. The main result was the near independence of the stability from the mass-spectrometer itself, but a strong dependence on the sample introduction system, the ICP-torch and the cones. Received: 18 February 1997 / Revised: 16 June 1997 / Accepted: 19 June 1997     

Physico-chemical studies on the photostabilization of poly(1-butene) film

Thin films of poly(1-butene) with and withouto-phenanthroline bis(1,3-diphenyl triazine-1-oxide)-cobal(II) [I] in the temperature range of 233–333° K have been degraded in air from a UV light of 253.7 nm. The changes in weight average molecular weights, degree of degradation, quantum yields, enthalpy and free energy of activation, and carbonyl and hydroperoxide contents, were followed as a function of the time of irradiation. The inhibition effect ofI is discussed on the basis of the luminescence and UV spectral data. The chelateI behaves both as a thermal and UV stabilizer due to a combination of different kinds of activity in the same molecule.     

Some investigations into the coating of glass open-tube columns

Summary The etching of soda glass by hydrogen chloride has been studied by determining the weight of sodium chloride per unit area on single and double statically-etched glass. The influence of three coating solvents on the critical surface tension of etched and unetched glass has been determined by measuring the contact angles of a wide range of stationary phases. The dynamic coating procedure has been critically examined and certain aspects which lead to the production of improved columns are explored.     

Some investigations on the post radiation grafting of acrylamide onto polyethylene films

A study has been made on the post radiation grafting of aqueous acrylamide onto low density polyethylene film. It was found that the addition of 0.05 wt % Mohr's salt reduced effectively the homopolymerization of acrylamide and the grafting process was successfully achieved. The dependence of the grafting rate on the preirradiation dose and monomer concentration was found to be of 1.43 and 1.4 order, respectively. The overall activation energy for the graft polymerization was found to be 13.5 and 1.95 Kcal/mol below and above 45°C, respectively. Some properties of the graft copolymer such as swelling behaviour, electrical conductivity, and reverse osmosis desalination of saline water (water flux and salt rejection), were also investigated and the possibility of its uses in the practical applications was discussed.     

Some investigations of the MP2-R12 method

Summary The MP2-R12 method was introduced by Kutzelnigg and Klopper to overcome the problem caused by truncation of the one electron basis set in correlation energy calculations at the Møller-Plesset second order level of approximation. Here, we have evaluated the integrals required by their simplest scheme using the Rys-quadrature procedure. Results are presented for Ne, H₂O, and HF using largespdf gaussian basis sets.     

Heterocycles. LXXXII. Some investigations on 1,2,3-benzotriazines

Various 4-substituted 1,2,3-benzotriazines ( 2, 6, 7 ) have been prepared and of particular interest was the 4-azido derivative ( 11 ) as a potential azidotetrazolo tautomerism exhibiting compound. However, no such interconversion could be established and this compound exists exclusively in the azido form. 2,5-bis-(Arylamino)-1,3,4-thiadiazoles (9) have been found to result from the reaction between 4-hydrazino-1,2,3-benzotriazine and aryl isothiocyanates. In addition, a ring opening reaction between 4-hydrazino-1,2,3-benzotriazine gave 2-(tetrazol-5″-yl)-2′,4′-dihy-droxyazobenzene ( 10 ) and photochemical conversion of the 4-azido derivative gave s-tetrazino-[2,3-b:5,6-b′]diindazole(12).     

Some investigations of fusing and dissolving samples

When both Si-H and Si-vinyl are present, the sum of these groups can be determined bromometrically. For Si-H a gasvolumetric method is applied and Si-vinyl results from the difference. The bromometric determination is carried out by dissolving the sample in a mixture of carbon tetrachloride/acetic acid, addition of excess solution of bromine in acetic acid and back-titration of the unconsumed bromine. Mercuric chloride serves as a catalyst for the bromine addition. The Si-H determination is carried out by measuring the hydrogen gas evolved after hydrolysis of the sample in wet n-butanol in the presence of sodium n-butanolate. The bromometric method proved to be also useful for the rapid and sensitive determination of either Si-vinyl or Si-H. The time required is 45 min, the lower limit is 0.02 mmole per g.     

Mechanism of photostabilization of polystyrene film by dihydroxyphenyl-pirazoles

A new family of ultraviolet absorbers, the dihydroxyphenyl-pyrazoles, has shown to be able to act as photostabilizers of polymers. In the present work the efficiency of the derivative 2,5 bis(pyrazol-1′-yl)-1,4-dihydroxybenzene (BPHB) in preventing the photooxidative degradation of polystyrene films have been measured. The effect of light screening on polymer photostabilization was examined by using external filter solutions of BPHB and it was found that it does not function simply as a light screener. Phosphorescence quenching experiments show that BPHB behaves also as an efficient triplet-state quencher of the polymer in-chain carbonyl impurity groups, which play an important part in the overall mechanism of light stabilization.     

Dynamic mechanical investigations on drawn samples of isotactic polypropylene/EPM–Rubber blend

The physical behavior of isotropic and oriented samples of an isotactic polypropylene (iPP)/ethylene–propylene–copolymer (EPM) reactor blend was studied by performance of dynamic mechanical measurements over a wide temperature range (DMTA). The influence of thermal history and drawing procedure was examined. The results showed that with increasing draw ratio the uniaxial elastic modulus of the material was considerably enhanced, whereas the intensity and strength of the amorphous relaxations of both components were reduced. At a certain draw ratio, the glass transtions of iPP and EPM phenomenologically merged and appeared as a single relaxation. The crystalline relaxation of iPP emerged with increased draw ratio at higher temperatures and was better seperated and easier to detect. The effects observed were attributed to the orientation of the crystallites in a fibrillar structure and to the restricted molecular mobility in amorphous regions. Measurements by differential scanning calorimetry (DSC) and x-ray diffraction of several drawn samples were performed to determine the effects of drawing on the melting behavior and the crystal orientation in the semicrystalline polymer. For comparison, some results of analogous studies on neat isotactic PP are presented and discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1439–1448, 1997     

Some investigations of sea sands from the Black Sea coastline

Alpha to spontaneous fission branching ratios of heavy actinides such as²³⁸Pu and²⁴⁰Pu in solution have been determined by solid state nuclear track detectors (SSNTDs). The detectors used in the present studies are LR-115, CR-39 (DOP), Lexan polycarbonate and Tuffak polycarbonate. Before using Tuffak polycarbonate, a detailed and systematic study on the registration and chemical etching characteristics of fission fragment tracks in this detector was also carried out. The experimentally measured values of alpha to spontaneous fission ratios by this method are found to agree well with the expected values.     

The kinetics of photostabilization of cyanocobalamin in liposomal preparations

Cyanocobalamin (B₁₂) is a photosensitive vitamin, and its photodegradation to hydroxocobalamin (B_12b) in liposomes has been investigated. The values of apparent first-order rate constants (k_obs) for the photodegradation of B₁₂ in liposomes (nine preparations) are in the range of (0.52-2.24) × 10^–3 min^–1, compared to 3.21 × 10^–3 min^–1 for B₁₂ in aqueous solution (pH 5.0). The entrapment efficiency of B₁₂ in liposomes is 26.4-38.8%. The values of k_obs show a linear relation with phosphatidylcholine (PC) content in liposomes, indicating the influence of PC in inhibiting the rate of photolysis of B₁₂. The value of the bimolecular rate constant for photochemical interaction of B₁₂ and PC is 0.32 M^–1 min^–1, indicating the stabilizing effect of PC on the photolysis of B₁₂. The ratio of B₁₂ stabilization in liposomal preparations is in the range 2-6 compared to that of the unentrapped vitamin The stabilization of B₁₂ is mediated by a photoinduced charge-transfer B₁₂-PC complex that leads to the reduction of B₁₂ to B_12r, which is then oxidized to B_12b that has low susceptibility to photolysis. The extent of stabilization of B₁₂ probably depends on the degree of interaction between the two compounds under the reaction conditions, indicated by the loss of B₁₂ fluorescence.     

Chemiluminescence from oxidation of polypropylene: Some comments on a kinetic approach

We present a detailed criticism of the kinetic approach to the analysis of data obtained from measurements of the very weak chemiluminescence accompanying the oxidation of polypropylene. It is shown that a kinetic model proposed by other workers is based upon invalid assumptions, leads to kinetic parameters which are not sensible, and requires measurement of the properties which it claims to predict.     

Photodegradation and photostabilization of europium compounds in polyvinyl chloride

The photolysis kinetics was studied, and methods were suggested for photostabilization of complexes of europium with β-diketones and europium cinnamates and quinaldates in polyvinyl chloride.     

Recent developments in chemistry of sunscreens & their photostabilization

Excessive exposure of UV radiation from the sunlight to human skin is dangerous and causes various skin disorders including skin cancer. Dermatologists worldwide recommend use of skin creams/lotions containing UV-filters/sunscreens for protection from such harmful effects. There is continuous evolution and development of new organic, inorganic and hybrid sunscreens which are being used in such skin care preparations. In the recent past it has been seen that some of these materials are not stable to UV light and the sun protection offered by them decreases rapidly with time. Therefore, most of the formulators now prefer photostable sunscreens or the formulations are designed in such a way that they provide inherent photostability.In this review, we have covered the chemistry of synthesis of different organic sunscreens, issues related to photostability of some of them, and different approaches used to enhance their photostability.     

Some features of the kinetics and mechanism of polypropylene autoxidation under tensile stress

The influence of tensile stress on different stages of the chain oxidation of polypropylene (PP) has been studied. The degrees of oxidation at various sites of the stressed samples, oxidized up to failure, were determined by i.r. spectroscopy using a focussed beam; the scanning was performed along the samples from the fracture site to the clamps. The change in the mechanism of initiation of oxidation with increasing stress was shown to be accompanied by a decrease in the propagation rate and an increase in the termination rate (with the participation of quickly decaying terminal radicals) and this led to a sharp decrease in the oxidation chain length. Consequently, inhibitors of chain oxidation become ineffective under high stresses and therefore do not increase polymer durability. The oxidation of stressed PP is shown to be local in nature; a defect detection process in oxidizing stressed PP is proposed based on the differences in product composition and concentration in stressed sites (matrix) and relaxed sites (near the cracks).     

Some analytical investigations into the use of X-rays emitted during charged-particle irradiation

X-radiation emitted as a result of charged particle irradiation offers a means of extending the scope of analytical methods based on the measurement of prompt radiation. X-ray yields from a number of pure materials have been examined over a range of particle energies and X-ray measurement applied to the determination of a number of constituents in aluminium alloys. An examination of the distribution of silicon and germanium across an electronic component has been carried out using a small diameter incident ion beam.