bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of magnetic polymers in water treatment
Authors: Bolto B. A. , Dixon D. R. , Eldridge R. J. , Swinton E. A. , Weiss D. E. , Willis D. , Battaerd H. A. J. , Young P. H. 
Published: June 2010

AbstractMagnetic polymers, originally conceived in ion‐exchange form as a means of handling microbeads in a thermally regenerable desalination process, have now been prepared in a variety of configurations for use in a number of water purification procedures. Processes have been devised which employ magnetic polymers in filtration, in oil slick removal, and in the adsorption of metal ions.Suitably shaped particles, when magnetized, form a filter bed of high voidage volume. Tests have been run on a variety of turbid waters. The particles give considerably better performance as filter aids than the diatomaceous earth normally used. An extremely important advantage is that the magnetic filter aids can be recovered and reused after washing.Vesicular forms of magnetic hydrophobic polymers float on water and have application in the removal of oil spills from water surfaces. The oil becomes trapped in the voids between the particles; the resulting mass is readily removed from the water by magnetic means, after which the oil is separated from the particles simply by centrifugation. The particles and residual oil are then recycled.Magnetic ion exchangers, smaller in size than conventional resins, can be employed in continuous contacting systems, such as fluidized and semifluidized beds. When compared with normal continuous ion‐exchange systems, the same removal of ions can be accomplished using considerably less resin in a plant which is smaller, simpler, and much cheaper to construct.
The photodegradation of poly 2,2′–(m–phenylene)–5,5′–bibenzimidazole
Authors: Brown J. R. , Burchill P. J. , George G. A. , Power A. J. 
Published: June 2010

AbstractPoly(2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole) (PBI) shows outstanding properties of low flammability, good abrasion resistance, and high moisture regain; but it is susceptible to degradation by sunlight. The chain‐scission quantum yield of 10−5 indicates a fundamentally stable structure. Degradation is related to the very intense light absorption in the solar region. Results also show that the degradation route is one of photooxidation. Limitations of traditional methods for preventing photodegradation are discussed, and the possibility of stabilization by a protective coating is explored.
Chemical reactions for the investigation of structure and properties of macromolecules
Authors: Braun Dietrich 
Published: June 2010

AbstractChemical reactions are a useful tool in the investigation of structure and properties of macromolecules. They can be used to prove the tacticity of noncrystallizable polymers. The chain conformation of polymers and helix‐coil transformations in solution can be studied by spin labeling, introducing stable free radical groups into the polymers. Competition of inter‐ and intramolecular reactions of macromolecules gives information on interpenetration of coils. The structure of crosslinked polymers can be studied by chemical cleavage of the network.
Recent developments in alternating copolymerization
Authors: Furukawa Junji 
Published: June 2010

AbstractAlternating copolymers exhibit several characteristic types of behavior. Their glass points Tg are sometimes derived from the mean of two homopolymers. It was found that Tg of copolymers of different degree of alternation can be expressed as a molar mean of each diad involved in the copolymer. The melting points are not clear except for some polymers of extremely high degree of alternation. High orientation was observed on stretching and greatly enhanced tensile property is exhibited. Alternating copolymers constitute versatile material such as rubber, functional polymer. etc.There have been developed several methods for the preparation of alternating copolymers. For the copolymerization of olefin and diolefin a modified Ziegler catalyst was developed. By controlling the number of coordination sites of the catalyst, the alternating coordination of olefin and diolefin is. made possible. The polymerization mechanism was established by determining the polymer structure using ozonolysis.For the copolymerization of an electron‐donating monomer and an electron‐accepting monomer two mechanisms are considered, one involving the donor‐acceptor intermediate complex and the other without such complex. The discrimination of these mechanisms is very difficult because there is little difference in the stereoregularity as well as sequence regularity according to the mechanisms.In the copolymerization of butadiene and acrylic monomer complexed with EtA1Cl2 and VOC13, there exists a maximum rate of polymerization at a definite monomer composition which is not changed by the amount of EtA1Cl2. This fact can be explained only by the complex mechanism.Other interesting methods for the preparation of the alternating copolymer, such as copolymerization through a zwitterion intermediate and ring‐opening polymerization, are reviewed.
Structure and properties of pharmacologically active polymers
Authors: Ringsdorf Helmut 
Published: June 2010

AbstractAlthough the concept of using pharmacologically active macromolecular compounds as drugs is still regarded with much skepticism for both theoretical and practical reasons, interest in this field has grown in recent years because of the opportunity to take advantage of the specific properties of polymeric materials. For low molecular weight drugs, changes in structure often lead to a loss of specific activity. On the other hand, the properties of macromolecular drugs depend on the structure of the polymer used and this can be varied over a wide range by the incorporation of comonomer units, by the application of polymer‐analogous reactions, or by related structural changes. A new model is presented for pharmacologically active polymers which incorporates the possibility for continuous variation in (a) solubility and toxicity, (b) fixation and removal of active material, and (c) body distribution. Using the new model as a guide, examples of the synthesis and study of the biological activity of various macromolecular drugs are presented in order to emphasize the importance of this cooperative effort between polymer research and therapeutic problems.
Conditions of gelation in the anionic divinylbenzene‐styrene copolymerization
Authors: Eschwey Helmut , Burchard Walther 
Published: June 2010

AbstractThe anionic copolymerization of p‐ and m‐divinylbenzene (DVB) with varying amounts of styrene (St) was studied. The molecular weights of the samples before gelation and of the sol fraction were followed according to their dependence on the applied ratio R′ = [St] [DVB]. Gelation occurred at critical values of R′c = 2.08 for the p‐DVB/St and of R′c =2.80 for the p‐DVB/St copolymers. The results are tentatively interpreted using Stockmayer's theory of the crosslinking of chains. A good agreement between theory and experiment was obtained for the polymers in the pregel state. The molecular weights of the polymers in the sol of the gel can be described by an equation that is similar to the Stockmayer equation, except the crosslinking probability is multiplied by the extinction probability, v. As v is closely related to the sol fraction, this fraction can be calculated from the applied R′ values and the experimentally observed molecular weights of the products. The sol fraction thus obtained was compared with the experimentally observed sol fraction. The differences between both sol fractions are discussed in some detail.
Dependence of crystallization capability of polyurethanes upon the degree of cross‐linking
Authors: Slowikowska Irena , Daniewska Irena 
Published: June 2010

AbstractThe investigation of crystallization capability of polyurethanes has been carried out on two series of polyurethanes, in which the degree of crosslinking was systematically changed. These tests included the light depolarization method, optical microscopy, and differential thermal analysis. Accurate dependence of the crystallization capability of crosslinked polyurethanes on the degree of crosslinking was found.
Wood fiber‐synthetic polymer composites. I. Laminates of paper and polyethylene
Authors: Michell Anthony J. , Vaughan Janet E. , Willis Donald 
Published: June 2010

AbstractWood fiber‐synthetic polymer composites are being studied with a view to using, in building or packaging, residues from the production of sawlogs and wood resources which are unsuitable for timber, pulp, or paper production. The structure of wood fibers and the properties required in a fiber intended for use as a reinforcing agent are described briefly.Laminates comprising 67% by weight of cellulose fibers have been produced by hot‐pressing sheets of paper coated with low‐density polyethylene. Mechanical properties of the laminates have been studied with particular attention to the effects of exposure to moisture. The flexural properties of the laminates at low relative humidities compared favorably with those of glass‐filled high‐density polyethylene and of paper‐phenolic resin laminates but declined more at high relative humidities.
Cationic polymerization of N‐vinylcarbazole by triphenylmethyl hexafluoroantimonate
Authors: Rooney J. M. 
Published: June 2010

AbstractThe polymerization of N‐vinylcarbazole (NVC) in methylene dichloride initiated by triphenylmethyl hexafluoroantimonate has been studied at 0 and 20°C.Experiments in an adiabatic calorimeter showed the rates of polymerization to be rapid (t1/2 ∼ 3 sec at [M]0 = 0.050M and [I]0 = 10−6 M), attaining first‐order with respect to monomer concentration after 30–50% conversion. The observed rate constants of propagation decreased with increasing initiator concentration to a constant value after [I]0 ∼ 10−5 M, which was not further reduced by the presence of excess SbF6− anions [from PhCH2(CH3)3NSbF6]. This behavior suggests propagation by both unpaired and paired ions and permits estimates of kp+ = 6 × 105 M−1 sec−1 at 20°C; 4.5 × 105 M−1 sec−1 at 0°C; and kp± = 5 × 104 M−1 sec−1 at both temperatures.Molecular weights (Mn) ranged between 30,000 and 100,000 according to conditions. The degree of polymerization was always < [M]0/[I]0, indicating that transfer reactions govern this chain length. Excess common anion reduced the molecular weights.A stopped‐flow apparatus was employed to monitor initiator consumption and values of ki, estimated at 130 M−1 sec−1 at 20°C and 34 M−1 sec−1 at 0°C.
The nature of the double bond in low molecular weight polyisobutylenes and “polybutene” copolymers
Authors: Puskas Imre , Banas Emil M. , Nerheim A. Glenn 
Published: June 2010

AbstractOlefin types were quantitatively determined by PMR and infrared spectroscopic analyses in polyisobutylenes and commercial polybutenes of Mn ranging from 500 to 2000. The catalyst and the polymerization conditions were found to have a great influence on the olefin type produced. In polyisobutylenes produced with BF3, the terminal vinylidene formed initially can diminish under the isomerizing influence of the catalyst. In polyisobutylenes synthesized with AlCl3, the major olefin type is °C(R)=CH(CH3). Its formation is explained by a multistep termination which involves tail‐to‐tail coupling. Internal vinyl‐idenes were also identified in most of the samples. Their formation can be explained by a skeletal rearrangement either in the termination step, or during polymer double‐bond isomerizations. In most polymers, the spectroscopically measured unsaturation was lower than that determined by hydrogenation. The difference is attributed to the presence of tetrasubstituted olefins.
The thermal‐mechanical degradation of high density polyethylene
Authors: Rideal G. R. , Padget J. C. 
Published: June 2010

AbstractThe changes in molecular structure of high density polyethylene which can take place during processing have been studied using a nitrogen blanketed Brabender plastograph to simulate processing conditions. At high melt temperatures (> 290°C) decreases in melt viscosity and a narrowing of molecular weight distribution were observed, while at lower melt temperatures an increase in melt viscosity was observed. The increase in melt viscosity arises from a molecular enlargement reaction which is mainly attributable to the formation of long chain branches (LCB) which were detected using intrinsic viscosity measurements as well as by a novel method involving the measurement of melt elasticity on a Weissenberg rheogoniometer. The scission and enlargement reactions are not mutually exclusive but competitive, and a basic reaction scheme is proposed to explain the experimental results. The effect on this basic reaction scheme of mechanical shear, polymer unsaturation, and oxygen content has been investigated. The presence of excess oxygen promoted the scission reaction, the extent of molecular weight reduction increased with decreasing temperature as would be expected for a shear induced reaction. However, it was found that under nitrogen the effect of mechanical shear at low melt temperature (<290°C) was to increase the melt viscosity and extent of LCB when compared to the corresponding reactions performed at the same melt temperatures but in the absence of shear; an explanation of this effect which involves the breakdown by shear of a radical cage is proposed. The observation that polymers having a high vinyl content undergo extensive increases in melt viscosity and LCB at all melt temperatures and in the presence or absence of shear has also been explained on the basis of the proposed reaction scheme.
Simple kinetic model diffusion controlled decay of free radical in highly crystalline polyolefins
Authors: Kryszewski M. , Nadolski B. , Zujewicz M. 
Published: June 2010

AbstractA simple kinetic model for the diffusion controlled decay of radicals in two‐phase high crystalline polyolefins is proposed. The analysis of the kinetic system was carried out taking into consideration a structural unit model containing all the structural properties of the macroscopic system. Radical decay in the amorphous phase and on the surface of lamellae has been discussed taking into account Wait's theory of diffusion controlled reactions, radiation boundary conditions, and the flux of radicals through lamellae surfaces.A rough computer calculation using the derived equation and the experimental data of Kashiwabara on radical decay in γ‐irradiated polyethylene was carried out leading to DA values equal to 10−9 cm2/sec, which favors the interchain hydrogen atom “hopping” mechanism of radical migration.
Antioxidants and stabilizers. LXII. Transformations of antioxidants: Thermal properties of alkylperoxycyclohexadienones
Authors: Buben I. , Pospíšil J. 
Published: June 2010

AbstractThe behavior of a number of alkylperoxycyclohexadienones investigated by differential scanning calorimetry and thermal gravimetric analysis has been described. The relationship between thermal behavior and the participation in the autoxidation process has been discussed.
The effect of transition metal N,N‐diethyl diselenocarbamates on the photooxidation of polyethylene
Authors: Osawa Zenjiro , Nakano Kosaku 
Published: June 2010

AbstractThe effect of transition metal (Co, Ni, Cr, and Zn) N,N‐diethyl diselenocarbamates over the range of 0.01 to 1.0 part per hundred resin (abbreviated as phr) on the photooxidation of a high density polyethylene film was examined, particularly by changes in the carbonyl IR absorption of the samples.The photooxidation of the polymer was remarkably affected by the kind of metal and concentration of the carbamates, and by the wavelength of irradiated light. Zn and Cr carbamates behaved as oxidation accelerators at lower concentrations over the range of 0.01 to 0.1 phr and as oxidation retarders at concentrations above the range of 0.5 to 1.0 phr. Co and Ni carbamates merely enhanced oxidation and the effect of both these carbamates increased with increasing concentration.Neat polymer gave an emission spectrum at ca. 350 nm which gradually decayed, and a new emission appeared at 470 nm following photooxidation of the samples. The presence of metal carbamates remarkably changed the emission spectra of the polymers, e.g., the disappearance of emission at ca. 350 nm.The roles of these metal carbamates are discussed on the basis of the luminescence and ultraviolet spectral data.
Some aspects of the photolysis and photooxidation of polyethylene containing ketone groups
Authors: Sitek F. , Guillet J. E. , Heskins M. 
Published: June 2010

AbstractStudies of the photodegradation of polyethylene containing 2 wt % methyl vinyl ketone (MVK) and methyl isopropenyl ketone (MIPK) show that the relative quantum yields of Norrish type I and II photolysis are strongly dependent on the structure of the ketone carbonyl. The type 1 process, leading to free radical formation, is particularly efficient in the MIPK copolymer, somewhat less so in the MVK copolymer, and very low in ethylene‐carbon monoxide copolymers where the carbonyl group is in the chain backbone. In the presence of oxygen, this difference shows up strongly in the rate of photooxidation. Backbone carbonyl groups have very low efficiency in initiating photooxidation of solid polymer films, while the side chain ketone groups initiate rapid photooxidation.
The role of interfibrillar tie molecules in drawing of polymers
Authors: Marikhin V. A. , Myasnikova L. P. 
Published: June 2010

AbstractA structural‐mechanical study of the orientation process in some flexible‐chain semicrystalline polymers has been conducted. By their deformation properties, such polymers may be conditionally divided into two groups: the ultimate draw ratio is 20‐25 for the first group and 6‐10 for the second one, the transformation of the original structure into a microfibrillar one being completed at a draw ratio (λ) of 8‐10 in the polymers of the first type and at a draw ratio of 2‐4 in those of the second type. The low draw ratios characterizing the moment of a virgin neck propagation in the polymers of the second type are considered to be due to a large number of tie molecules in the original su‐permolecular structures. When microfibrils are formed, these molecules are supposed to be included between fibrils.It is shown that a further increase of λ results from the microfibrillar slip. In the polymers of the first type, the slip is, however, relatively easy and is not accompanied by significant changes in the internal structure of microfibrils, because the interfibrillar tie molecules are almost absent in them. In the polymers of the second type, a significant change in the internal cture of microfibrils, associated with a large number of interfibrillar tie molecules, is observed (obliquity of crystallites and an increase of the long period attributed to an increase in the length of the amorphous intrafi‐brjjlar layer).The microfibrillar slip leads to their more dense packing, which results in a sharp increase in the orientation load required for further drawing. This reduces significantly the lifetime of the specimens in high temperature drawing and leads to their fracture by a thermal fluctuation mechanism.
Drawing behavior and mechanical properties of highly oriented polycarbonate fibers
Authors: Falkai B. , Hinrichsen G. 
Published: June 2010

AbstractFibers from bisphenol‐A polycarbonate are typical representatives of the less crystallizing synthetic fibers. Because of the high glass transition temperature, textiles produced from these fibers have outstanding laundry‐resistance and noncreasing properties. Polycarbonate fibers can be produced both by the dry or wet‐spin and by the melt‐spin process. The stretching of the fibers is carried out in accordance with the proposed textile characteristics below or above the glass transition temperature or by a special swelling–drawing process, in the course of which fibers of particularly high tenacity and elastic modulus can be obtained. The fibers produced by the latter process were investigated by a number of physical measurements of their morphological structure (density, birefringence, X‐ray wide‐ and small‐angle scattering, differential calorimetry, thermo‐mechanical analysis). These measured values of density, birefringence, and heat of fusion show that these fibers have a higher degree of crystallinity than the fibers produced by a melt or dry spinning process. Whereas with dry‐spun fibers an increase in tenacity can be obtained by raising the molecular orientation up to a limited tenacity value, it is possible with fibers produced by the swelling‐drawing process to virtually double the tenacity due to the higher crystallinity and improved crystal structure (creation of a large number of physical linkages). By means of X‐ray small‐angle scattering on annealed swollen‐drawn polycarbonate fibers, we were able to detect, for the first time, a marked two‐phase structure consisting of crystalline and noncrystalline regions with a long‐period of about 120 Å. With other crystalline polymers, a period of this kind has been known for many years.
Natural and artificial heterogeneous nucleation in polymer crystallization
Authors: Binsbergen F. L. 
Published: June 2010

AbstractAn outline is given of heterogeneous nucleation as the main starting point for crystallization of unoriented polymer melts and solutions. The influence of temperature history on nucleation is discussed. As little is known about naturally occurring nucleants, the nature of several types of artificial nucleating agents is described. Potential mechanisms of heterogeneous nucleation are discussed against the background of various theoretical models. Experimental methods of measurement of nucleation density or of nucleation frequency may give some indication as to which mechanism is operative. The main conclusion is that heterogeneous nucleation is governed by “active sites” in the surface of the nucleants.
Dependence of oligomer–oligomer incompatibility on chain length and pressure. I. Oligo‐isobutene/oligo‐propylene glycol and oligo‐styrene/oligo‐ethylene glycol
Authors: Wolf B. A. , Blaum G. 
Published: June 2010

AbstractIn the systems oligo‐isobutene/oligo‐propylene glycol and oligo‐styrene/oligo‐ethylene glycol, which invariably exhibit low temperature demixing, the corresponding upper critical solution temperatures increase with the chain length of the nonpolar component, whereas they run through a minimum when that of the particular glycol is raised. In all cases the incompatibility is enhanced by pressure, i.e., the mixing volumes result positive. Although these findings can be well understood qualitatively, a quantitative theoretical description of the chain length dependencies turns out to be impossible on the basis of current theories, probably because of the polar nature of the glycols. A very helpful evaluation and interpretation of these experimental results can however be performed by means of the lattice theory; it yields an enthalpy parameter and allows the extrapolation of the critical temperatures to higher molecular weights. For the pressure influences a qualitative forecast is possible in most cases by means of the Prigogine‐Patterson theory, if one parameter is adjusted to the measurements at normal pressure. Mixing volumes can also be estimated from the above‐mentioned enthalpy parameter and the slope of the experimental critical lines.