bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface‐polymerization of tetrafluoroethylene on fluorine‐activated metal substrates
Authors: Toy Madeline S.
Published: June 2010

Metals form protective metal fluoride films upon exposure to fluorine. The utilization of the metal fluoride films as catalysts for surface polymerization of tetrafluoroethylene is described. The process consists of a two‐step synthesis: (1) gas phase fluorination of a metal sample to produce a fluoride film on the metal surface and, (2) gas phase polymerization to form a polymeric coating. The fluorocarbon films formed on the metal substrates by the Toy process are fairly adherent, continuous and flexible, except that it is somewhat porous depending on the conditions of fluorination, polymerization, metal compositions, and metal surface preparations. The possible mechanisms of surface‐polymerization are discussed.
Chemo‐rheology of curing in structural adhesives I: Epoxy‐phenolic systems
Authors: Kaelble D. H. , Cirlin E. H.
Published: June 2010

Thermosetting adhesives undergo a chemo‐rheological transition during cure which transforms the material from an initial compliant bonding state to a rigid high strength holding state. The results of combined application of differential scanning calorimetry (DSC) and Instron thermomechanical analysis (TMA) in a study of reaction kinetics and physical state changes in epoxy‐phenolic adhesives are reported. A special reduction of DSC data isolates the apparent heat of polymerization ΔHp and activation energy E* of curing. Analysis of a repetitive extension‐recovery cycle, at low strain amplitude, isolates the temperature‐time effects of curing upon the tensile modulus E, the work of deformation WT = WL + Ws, and the work ratio WP/Ws = work loss/work stored per cycle. Correlated results of DSC and TMA analysis of two epoxy‐phenolic adhesives isolates the effects of metal fillers upon both the curing kinetics and mechanical response of the cured material.
Chars produced from cellulose under various conditions of thermal decomposition
Authors: Miller Bernard , Gorrie Thomas M.
Published: June 2010

An experimental study has been performed to identify the controlling conditions when self‐generating flames move through and transform flame‐retardant treated and untreated cotton fabrics. The approach has been to compare the chars formed by flames with those produced by induced (nonflame) thermal decomposition under known conditions of temperature and environment. Char comparisons were made mainly through internal reflection infrared spectroscopy. Considerable variations were found among chars formed by flames moving in different directions in space, corresponding to differences in the maximum temperatures and degree of contact with oxygen experienced by the materials during burning.
The effect of liquid anhydrous ammonia in the structure and morphology of cotton cellulose
Authors: Lewin Menachem , Roldan Luis G.
Published: June 2010

The effect of liquid ammonia on cotton fabric was studied using x‐ray diffraction (XRD) and electron microscopy. A phase diagram is presented describing the relationship between disordered cellulose, cellulose I, and cellulose III. The transition from cellulose I to III proceeds through the liquid ammonia. Cellulose III is obtained upon drying the ammonia‐cellulose without the presence of water. Treatment of the cellulose III or of the ammonia‐cellulose with water brings about the formation of cellulose I. The degree of crystalline order achieved in water is enhanced by heating, which is consistent with a glass transition temperature between room temperature and 100°C. The cellulose III crystallites obtained are much smaller than those of cellulose I,16‐23Åas against 50‐80Å

The interaction of ammonia with cotton cellulose is faster than with other swelling agents, such as ethylamine. The penetration of ammonia into the secondary wall of the cotton fiber is not only along the concentrical rings, as is the case with water, but also radially across the rings.

Prolonged soaking in water increases the crystallite size with simultaneous rejection of swelling water.
Folding chain model and annealing of cellulose
Authors: Chang Martin
Published: June 2010

A folded chain model of cellulose fine structure has been developed, together with a new hypothesis on cellulose “weak links”. Essentially, single cellulose molecules are folded back and forth in the (101) plane to form “platellites” which are the smallest physical and structural unit of crystalline cellulose. The average fold length in the platellites corresponds to the levelling‐off DP. The glucosidic bonds at the folds are weak links due to a loop conformation of the chain.

The morphological transition of cellulose during mercerization has been examined with reference to the folding chain model. It is envisaged that the transition is the result of a partially restricted annealing of the cellulose crystals under the action of the swelling agent. Thus, low‐temperature annealing of cellulose shortens the fold length of the molecule and results in the well known mercerization process; high‐temperature annealing, on the other hand, generates at least a partial reversal of the mercerization. This hypothesis is found to agree very well with the known facts in the literature and is further supported by some experimental evidence.
Some properties of water‐soluble hydroxyalkyl celluloses and their derivatives
Authors: Klug E. D.
Published: June 2010

The effect of increasing the substitution of water‐soluble hydroxyethyl cellulose (HEC) and hydroxypropyl cellulose (HPC) is to decrease their affinities for water. This is consistent with data given on the cloud point, salt tolerance, surface tension of aqueous solutions, and solubility in organic solvents, all as functions of MS.

Ionizable substances have a great influence on temperature‐solubility behavior of the hydroxyalkyl celluloses. If the ions are present as inorganic salts in solution, they cause hydration of the polymer to decrease with some loss in solubility. In the case of HPC, ions derived from substituent groups, present in small amounts, improve hot water solubility and impart unusual viscosity‐temperature behavior.

Mechanical properties of HEC film and thermoplasticity of HPC are functions of the extent of substitution rather than the hydrophilicity.
Kinetics of crystallization of polyamide 6 from the glassy state
Authors: Kozlowski Wojciech
Published: June 2010

Glassy polyamide 6 was obtained by quenching the melt in liquid toluene at 210°K. On the DSC thermogram of such a polyamide a small endothermic peak of glass transition at 310°K, and an exothermic peak at 325°K of cold crystallization are observed (both temperatures were calculated by extrapolation to zero heating rate).

The kinetics of cold crystallization was investigated in the range 321‐339°K by DSC technique using three different methods of measurement: 1) standard isothermal, 2) isothermal by Miller, and 3) nonisothermal by Ozawa. The data obtained from 1 and 2 were analyzed by the simple Avrami equation, and from 3 by a modified equation. It was confirmed that the exponent n is not constant; in the range up to 328°K it has an average value of 2.2, and then varies with the rise in crystallization temperature. Unfortunately, the mechanism of the variation of n is not known and this prevents the calculation of the crystallization rate from the nonisothermal dynamic data.

Thus, an assumption was made that crystallization follows first‐order kinetics: K and t0.5 for different temperatures were calculated; the Arrhenius function was plotted; and from it the activation energy of 69.7 kcal/mole was estimated.
The structure of solutions and films of cellulose acetate
Authors: Buntjakov A. S. , Averyanova V. M.
Published: June 2010

The optical rotatory dispersion of solutions of cellulose acetates with different degrees of acetylation in a series of solvents is studied. Increasing the degree of esterification of the cellulose acetate results in a shift of the optical rotation to more negative values. These changes have been explained on the assumption of various contributions to the optical rotation from hydroxyl and acetate groups. The cellulose acetate solutions studied fall into two groups. Solutions in acetic acid, dimethylformamide, nitromethane, and acetone give anomalous curves, whereas in methylene chloride, chloroform, tetrachlorethane, and dioxane normal curves of rotatory dispersion are produced. Attempts to fit the results by calculations based on a one‐term Drude equation proved all the curves to be more complex. The influence of solute is probably due to specific interaction with hydroxyl and acetate groups and fixing of rotatory isomers of the side groups. A complex pattern of the rotatory dispersion curves is dictated by the contributions from asymmetric carbon atoms associated with hydroxyl and acetate groups having a different rotatory dispersion. Polymer‐solvent interaction affects the film structure. Crystalline films are obtained from cellulose acetate solutions (AcOH = 60.3%) with anomalous dispersion while solutions with a normal dispersion give amorphous firms.
Morphological changes in nylon 6 and effect on mechanical properties. II. Dynamic mechanical properties
Authors: Hoashi Koji , Andrews Rodney D.
Published: June 2010

Dynamic mechanical measurements were carried out on nylon 6 film treated with heat and swelling agents to produce changes in the crystalline morphology. The original smectic hexagonal crystal form was changed by heat treatment and phenol treatment to an unoriented and oriented α‐crystalline form, respectively, and by I2/KI treatment to a preferentially oriented γ‐crystalline form. The behavior of the αa mechanical loss peak located at about +70°C was investigated in most detail. This peak was independent of frequency on the low‐temperature side of the peak but markedly frequency‐dependent on the high‐temperature side. The low‐temperature side of the peak probably represents a thermodynamically controlled “melting” or bond‐breaking process which frees molecular units to participate in a viscoelastic relaxation process which is the controlling factor in the high‐temperature side of the peak. Frequency‐temperature superposition of data from the high‐temperature side of the peak gave shift factor values which showed two straight‐line regions in the Arrhenius plot for the specimens containing some smectic hexagonal form, and a single straight line in the other cases. Activation energy values obtained were 30–50 kcal. The αa peak split into two components with an increase in absorbed phenol, indicating that two loss mechanisms corresponding to two noncrystalline phases (one amorphous and one more highly ordered or hindered) are involved.
Triplet energy transfer in solid solutions and films of poly(vinyl carbazole)
Authors: Klöpffer Walter , Fischer Dieter
Published: June 2010

Monomeric carbazole derivatives show phosphorescence in the wavelength region between 400 and 500 nm. Poly(vinyl carbazole) (PVCA) in dilute frozen solutions also shows phosphorescence in this region and, in addition, delayed fluorescence owing to triplet‐triplet annihilation. The latter depends on the molecular weight of the polymer, high‐molecular weight samples showing very strong delayed fluorescence, whereas in low‐molecular weight products phosphorescence prevails.

The phosphorescence of solid PVCA is governed by traps. Comparison with low‐temperature fluorescence and measurement of decay times suggest that two traps are important for both singlet and triplet excitons. The excimer‐forming site is one of them. The maximum of triplet excimer emission is at about 500 nm, the decay time is 7.9 ± 1 sec (compared to 410 nm and 43 nsec in the singlet system). The second trap emits in the same wavelength region, decay time 1.4 sec, and corresponds to a second intrinsic singlet trap emitting at 380 nm (decay time 12 nsec). The range of the triplet exciton at 77°K is drastically reduced by these traps, as in the case of the singlet system.
Study of the reaction of oxyradicals with antioxidants on synthetic zeolites
Authors: Rychlý J. , Lazár M. , Pavlinec J.
Published: June 2010

The ESR method has been used for the study of the inhibition effect of some antioxidants on polymerization of methyl methacrylate proceeding in the surface of synthetic faujasite of the Na Y type. From equilibrium levels of trapped radicals the inhibitor efficiency has been elucidated as follows: hydroquinone > diphenylamine > 2, 6‐di‐tert‐butyl‐4‐methylphenol > pyrogallol > N‐phenyl‐2‐naphthylamine > 1‐naphthol.

Mechanism of hydroperoxides decomposition on zeolite surface has been discussed as well.
THE radical reactivity of some bisphenol antioxidants
Authors: Simonyi M. , Kardos J. , Tüdös F. , Pospíšil J.
Published: June 2010

4,4′‐isopropylidene‐bisphenol and some of its methyl and tert‐butyl derivatives were studied by inhibiting the radical polymerization of vinyl acetate. Alkyl groups in the bisphenol increase the radical reactivity. The substituent effect is significantly additive, i.e., the individual groups contribute independently to the reactivity. As a contrast, in the case of 2, 6‐tert‐Bu2 substitution a steric effect emerges. The analogy between the reactivities of phenols and bisphenols is remarkable.
Thermooxidative stability of copolymers having polyconjugated fragments in the main chain of macromolecules
Authors: Berlin A. A. , Gherassimov B. G. , Ivanov A. A.
Published: June 2010

Copolymers have been synthesized which consist of polyazophenylene (1‐50%) and polyisoprene (or polystyrene) fragments. Synthesized copolymers have some specific properties caused by intermolecular interaction of polyconjugated blocks. The inhibiting activity of polyazophenylene blocks of copolymers was ascertained considerably to surpass the inhibiting effect of polyazophenylene addition to corresponding homopolymers in the processes of thermal destruction and oxidation of polymers. This is reflected in the decreased rate of oxygen absorption at constant temperature, in the decreased rate of weight losses in isothermal conditions, and in the increased temperatures of 50% weight losses of copolymers by the dynamic thermogravimetric analysis. The increased inhibiting activity of polyconjugated blocks is explained by their improved compatibility and distribution in polymer substrate and by the increase of conjugation degree owing to intermolecular interaction of polyconjugated blocks.
The diffusion time lag in polymer membranes containing adsorptive fillers
Authors: Paul D. R. , Kemp D. R.
Published: June 2010

Immobilizing adsorption of diffusing penetrants is known to occur in a number of polymer membrane systems. It will cause very large increases in the diffusion time lag but will have only minor effects on the steady‐state permeation. This effect may be troublesome in that considerable errors may be incurred when the time lag method is used to analyze quantitatively the sorption and diffusion behavior in such systems. On the other hand, this effect can be utilized in a beneficial way to design very effective protective coatings, packaging materials, timed release mechanisms, etc. for special situations. The time lag in this case can be predicted very accurately from a theoretical result reported previously. This point is demonstrated here by comparing theoretical predictions with experimental time lag data obtained for various gases in a model membrane synthesized by dispersing highly adsorptive molecular sieves into silicone rubber. The agreement is excellent.
The effect of solutes on the pervaporation of water‐methanol mixtures through cellophane
Authors: Misra Ashok , Kroesser F. William , Shelden Ronald A.
Published: June 2010

The effects on permeation rate and permeate composition of the addition of sodium formate to mixtures of methanol and water pervaporating through cellophane have been examined. In general, the addition of the salt increased the water content of the permeate, but decreased the total rate of pervaporation and that of each of the components. The effect was greater in water‐poor feeds. The effect of the salt on the permeate composition was opposite to the expected effect on the relative volatility of the feed components. The possible causes of this “solute effect” are discussed.
Polymerization of capryllactam initiated with acids under anhydrous conditions
Authors: Puffr R. , Šebenda J.
Published: June 2010

An investigation was made of the kinetics of polymerization initiated with carboxylic acids of different acidity, namely, caprylic, p‐fluorobenzoic, and o‐chlorobenzoic acids at 220–280°C and also with capryllactam hydrochloride for comparison. The polymerization proceeds without an induction period, is little dependent on the acidity of the initiator, and can be expressed in terms of a simple kinetic equation: ‐dL/dt = k I0aL. If carboxylic acids are used for initiation, the exponent a is 0.82, the pre‐exponential factor and the activation energy of polymerization is 1.85 × 1012 and 30 kcal/mol respectively. In the discussion, the polymerization of capryllactam is compared with the polymerizations of caprolactam and laurolactam.
The free radical bulk polymerization of ethylene at low temperatures
Authors: van der Molen Th. J.
Published: June 2010

A method is presented to recover the polymer formed in the free radical bulk polymerization of ethylene as a powder rather than as a melt. The paper mentions several advantages of this new approach, which has been used in a study on the production of medium and high density polyethylene with the aid of radical initiators at temperatures below the melting point of polyethylene (suspension bulk polymerization). The method of preparing products with a very high stiffness comparable to that of homopolymers made by the Ziegler process is, in principle, also applicable at polymerization termperatures above the melting point of polyethylene, provided (meth) acrylamide is employed as a comonomer.
Anionic polymerization of caprolactam. XLVII. Effect of polymerization conditions upon the keto groups content in anionic polycaprolactam
Authors: Čefelín P. , Stehlíček J. , Šebenda J.
Published: June 2010

In the anionic polymerization of ε‐caprolactam, approximately 0.5–1 keto group is formed per one activator molecule very quickly at 250–280°C. The concentration of the keto groups in the polymerizate depends on the initial concentrations of the catalytic components, the temperature, and the polymerization time. At a low effective basicity, the majority of keto groups originates during the first minutes, whereas at higher basicities most of the keto groups are formed in the later stages of the process. In polymers prepared in the presence of sodium caprolactam and N‐benzoylcaprolactam there occurs transitional branching and the primary branched chains become linearized during extended heating.
On the polymerization of acetylenic derivatives. XIX. Synthesis of poly (α‐ethynyl naphtalene) and its electrophysical properties
Authors: Simionescu Cr. , Dumitrescu Sv. , Percec V. , Negulescu I. , Diaconu I.
Published: June 2010

The polymerization of α‐ethynyl naphtalene, (EN) with Ziegler soluble catalysts and tertiary phosphine‐transition metal complexes has been investigated.

The following catalysts, MeII(dmg)2. 2X/Al(R)2R′, (where MeII = Fe, Ni; dmg = dimethylglyoxime; X = pyridine, Py, or NH3; R = C2H5, i ‐ C4H9 and R′ = C2H5, i‐C4H9, Cl), specific to cis polymerization of acetylenic monomers and (PPh3)a. MeXb (where Ph = C6H5; a = 2,3; Me = transition metal of group VIII; X = Cl, Br, I, SCN and b = 2, 1) specific to trans polymerization of these monomers have been used.

The influence of some reaction parameters (i.e., polymerization temperature, temperature of the first catalyst‐monomer contact, catalyst nature and concentration, etc.) have been followed and two different mechanisms of EN with the said catalysts were proposed.

The obtained polymers were analysed from the point of view of their structural and electrophysical properties.
Polymerization by high electric fields: Field emission and field ionization
Authors: Schnabel Wolfram , Schmidt Werner F.
Published: June 2010

The polymerization of styrene (St) and α‐methylstyrene (α‐MSt), initiated by high electric fields, has been investigated by using an electrode assembly comprised of a tip (sharp edge) and a flat counter electrode. Maximum specific yields obtained under field ionization (FI) conditions amount to ca. 6000 kg/Faraday (St) and 3000/Faraday (α‐MSt), respectively, and are higher than under field emission (FE) conditions: 1500 kg/Faraday (St) and 100 kg/Faraday (α‐MSt), respectively. In the case of FE initiated polymerization polymer is formed via a cationic mechanism. Part of the polystyrene formed under FE conditions is generated via free radicals. Evidence is obtained by gel permeation chromatography and scavenger experiments. A mechanism via free cations could be established for the FI initiated polymerization.
Studies on polymerization of N‐vinylcarbazole in the presence of some hydrogen halides
Authors: Pielichowski Jan
Published: June 2010

Studies on N‐vinylcarbazole polymerization were carried out in the presence of HF, HCl, HBr, and HJ using a variety of solvents. It was found that in the CCl4 solvent, each of the hydrogen halides cause polymerization of N‐vinylcarbazole, the obtained polymer including equimolar proportions of hydrogen halide and of N‐vinylcarbazole.

To determine the influence of solvent polarity, some studies on the polymerization of N‐vinylcarbazole influenced by HCl were carried out in the following solvents: carbon tetrachloride, acetone, and methanol. A pronounced contribution of the solvent to the polymerization course was found. A polymerizate including a small proportion of the complex‐bonded HCl was obtained when using acetone or methanol solvent.

Irrespective of the nature of the solvent used, the appearance of a green color was observed in all instances; hereafter the solution turned brown accompanied by the polymer precipitation.

The polymerization proceeds without any disturbances in the presence of some species that capture the radicals, this being evidence for the ionic nature of the mechanism.

Based on the UV and ESR spectra analyses, it was found that some change‐transfer complexes are formed during polymerization. The result obtained make us accept the following mechanism of N‐vinylpolymerization in the presence of hydrogen halides, depending on the reaction medium.

Based on the results given, the following conclusions referring to the N‐vinylcarbazole polymerization process in the presence of some hydrogen halides can be drawn. In the early stage of polymerization of N‐vinylcarbazole, the initiation by means of HX occurs and hereafter the polymer is formed. Then, in a nonpolar medium, a charge‐transfer complex of the polymer with hydrogen halide is formed. On the other hand, in a polar medium, this complex cannot be formed.
Synthesis and characterization of poly (phenyl methacrylates)
Authors: Wesslén Bengt , Gunneby Gunilla , Hellström Gunnar , Svedling Per
Published: June 2010

Phenyl methacrylate (PMA), as well as its 2‐ and 4‐methoxy analogs (2‐MeOPMA and 4‐MeOPMA, respectively) were polymerized by free radical and anionic polymerization reactions. On anionic polymerization in toluene termination reactions occurred, and polymers were obtained only from PMA and 4‐MeOPMA. Polymers with relatively narrow molecular weight distributions were formed on anionic polymerization in tetrahydrofuran.

The steric structures of the polymers were determined from 100 MHz NMR spectra. Polymers obtained by free radical polymerization were found to be predominantly syndiotactic. Anionic polymerization in toluene produced highly isotactic polymers, while the use of tetrahydrofuran as a solvent gave syndiotactic polymers. Glass transition temperatures of the syndiotactic polymers were generally higher than those of the isotactic ones.
Adsorption of polymers on clays
Authors: Schamp N. , Huylebroeck J.
Published: June 2010

Adsorption of polyacrylamide with varying molecular weight on clays has been measured. Adsorption on peptized versus flocculated clays differs in amount, in kinetics, and in dependence on molecular weight and temperature. Therefore, distinction is made between surface adsorption and pore adsorption. Adsorption isotherms fit Langmuir equation but contain a minimum, which is explained by a kind of phase transition in polymer solution between an inhomogeneous system with separate polymer coils and a homogeneous system where all of the space is filled with coils.
Renforcement des elastomeres par des particules spheriques
Authors: Evrard G. , Nottin J. P.
Published: June 2010

In the course of a systematic investigation of reinforcement of elastomers, we studied the properties of model composites made of a rubbery matrix and spherical particles with several diameters and various level of adhesion to the matrix. Mechanical properties measured at very small strain are independant of particle size and adhesion, but under large extension reinforcement is more effective with smaller spheres and stronger adhesion. A partial correlation is found between dewetting of particles and loss of reinforcement efficiency.
Some peculiarities of relaxation and structure‐forming processes in polymer boundary layers
Authors: Malinsky Yu. M. , Prokopenko V. V. , Titova N. M. , Areshidze M. G. , Epelbaum I. V.
Published: June 2010

The relaxation processes are retarded when the polymer interlayer in adhesive joints is diminished to a few microns. This retardation shifts the maximum on the temperature vs strength curve of such joints (under considerable overstresses) toward higher temperatures, and secondly, reduces the effectiveness of “rest” responsible for the partial strength recovery of the specimen in which rupturing crack propagates.

In many systems the rate of polymer spherulite linear growth (G) diminishes with decreasing thickness of the polymer film (δ) from 15 to 30 μ. This was observed for isotactical polypropylene (PPr) and polystyrene, polyformaldehyde, cellulose tribenzoate, guttapercha, polypropyleneoxide (PPO), and polyethylenesebacynate (PES) on silica glass; PPr on copper, low‐melting metal alloys (in crystalline or liquid state), various crystallo‐graphic planes of NaCl, and planes (100) of CaF2 and LiF. The magnitude of G did not depend on δ in the crystallization of PPr, PPO, and PES on polyvinylacetate, polyvinylbutyral, crystalline and liquid low‐melting mixtures of inorganic salts. Inhibition of spherulites growth in polymer boundary layers is strongly influenced by the surface energy irrespective of the phase or aggregate state of the substrate. The retarded growth of spherulites is probably due to the reduced density and lower mobility of polymer in the boundary layers.
Effect of pressure on the crystallization of polyethylene
Authors: Kanetsuna H. , Mitsuhashi S. , Iguchi M. , Hatakeyama T. , Kyotani M. , Maeda Y.
Published: June 2010

Crystallization of polyethylene under pressure has been studied systematically with regard to the structure of the resultant crystal. It was found that in the isothermal crystallization under pressure, alteration of the form of the crystals from folded to extended occurred above certain pressures within a relatively narrow temperature range. The highest temperature that allows isothermal crystallization increases linearly with the pressure, while the lowest temperature to give the extended‐chain crystals increases rather slowly with pressure, widening the temperature range to give the extended‐chain crystals. The least pressure required was found between 2000 and 3000 kg/cm2 for the polymer studied in this work. It is considered that control by a particular nucleation or growth mechanism, different from the ordinary folded‐chain type crystallization and possibly the formation of bundle‐type nucleus is more likely than the effect of annealing or secondary growth of once folded molecules.
Diffusion of gas through polymer bulk: Computer simulation approach
Authors: Jagodic F. , Borštnik B. , Ažman A.
Published: June 2010

The diffusion of a gas through the polymer (polyethylene) bulk is calculated in two steps. In the first part, the amorphous phase of the polymer chains, at appropriate temperature and density, is generated using the Monte Carlo method on the tetrahedral lattice. The ground state is then obtained by the inclusion of the interchain forces. Using the energy surfaces from the first part, the energy barriers, modified by the interaction detween gas molecules (argon) and the polymer chains, are deduced. These values are the basis for the calculation of the diffusion coefficient.
Light scattering, turbidity, and conservative dichroism of suspensions of anisotropic particles in an electrical field
Authors: Ravey J. C.
Published: June 2010

Using the Rayleigh‐Gans approximation and expressions for the mean amplitudes (Evv,…,EHv) induced in rigid anisotropic particles which are arbitrarily oriented, one can calculate the four “components” of the light scattered in an arbitrary direction of space. Likewise, using these relations, the turbidity and the “conservative dichroism” of suspensions of anisotropic particles, partially of fully oriented, are studied, and in any case are calculated.
Thermal stability of melamine formal‐dehyde resins
Authors: Manley T. R. , Higgs D. A.
Published: June 2010

The temperatures given for the decomposition of melamine formaldehyde (MF) resins cover a wide range. An investigation of this decomposition using DTA, TG, EGD, and infrared techniques has shown that these variations are due to different criteria of stability and to errors in interpretation of thermoanalytical results.

There is considerable loss of formaldehyde at 200°C which makes this the maximum temperature for the use of MF resins in paints. Contrary to earlier results the triazine ring is not decomposed below 400°C and the main decomposition reaction is the breaking of methylene bridges around 380°. Under oxidative conditions the decomposition occurs at lower temperatures but the mechanism is not yet clear.
Study of destruction process of organotin derivatives of copolymers on basis vinyl‐chloride and unsaturated acids
Authors: Rzaev Z. M. , Mamedova S. G.
Published: June 2010

Radical copolymerization has been investigated between vinylchloride and organotin (lead) derivatives of unsaturated acids (bis‐triethyl‐stannylmaleate, β‐phenyl‐tri‐n‐butylstannylacrylate, and tri‐n‐butylstannylmethacrylate and their organic analogs (maleic anhydride andn‐butylmethacrylate). The esterification has been studied of copolymers of vinyl‐chloride and unsaturated acids by organic, organotin (lead) hydroxyl containing compounds and the latter dehydration productsbis‐trialkyltin oxides. The probabilities of forming various compositions (F(M)n, fM1‐M1, fM2‐M2fM1‐M2, or fM2‐M1) in copolymers have been calculated as well as probability of distributing monomer units along the macromolecular chain. Symbat relationship has been established between the probability of forming fM1‐M2and fM2‐M1compositions and thermo‐ and light‐stability of copolymers. The compositions of organotin comonomers and their copolymers with vinylchloride have been investigated. The stabilizing effect of organotin (lead) comonomers in their copolymers with vinylchloride has been revealed, consisting in coordinate interaction of metal atoms with chlorine substituents. The method has been worked out for examing light‐ and thermo‐stability of organotin (lead) copolymers. The stabilizing action of the side organotin (lead) groups on the starting temperature of copolymers, as well as on the induction period duration and the total rate of HCl isolation, has been determined. The occurrence of intermolecular coordinate bonds in the synthesized copolymer macromolecules has been revealed, this fact being the cause of a marked decrease in the copolymers dehydrochlorination rate.
Thermal relaxation and glass transition in polyethylene
Authors: Chang Shu‐Sing
Published: June 2010

Thermal relaxations in the glass transition region can be observed as spontaneous temperature drifts of the sample under adiabatic conditions. Upon the heating of a quenched glass, positive drifts are observed reaching a peak at some temperature just below its Tg. An annealed glass produces a peak in the negative drift at temperatures just above its Tg. Heat capacity measurements have been made on three linear polyethylene samples having 71 to 96% crystallinity and on one branched polyethylene sample, in an adiabatic calorimeter from 2 to 360 K. In all four samples, temperature drifts were detected with peaks occurring around 235–240 K. The temperature of the peaks is not significantly affected by the degree of crystallinity. However, the magnitude of the peaks decreases as the crystallinity is increased.
Experiments for teaching polymer characterization
Authors: Collins E. A. , Baresš J. , Billmeyer F. W.
Published: June 2010

A laboratory manual has been published containing over twenty experiments on polymer characterization, including measurement of molecular weight and distribution, thermal properties, morphology, and mechanical properties. Although written for immediate use in a polymer science laboratory course, the book should find wide use for the instruction of industrial laboratory assistants and by the chemist or engineer who wishes to familiarize himself in further detail with the field.

This paper will discuss both the philosophy of the book and the details of selected experiments, all of which have been tested in a graduate laboratory. The main text of the book provides background information on synthesis (experiments in synthesis are also included), a minimal scheme for the characterization of a new polymer, and equipment, theory, data treatment, and limitations for each characterization method for which there is an experiment. Wherever appropriate, a numerical data set is worked through in complete detail from instrument readings to final results. The format of the experiments proper, like those of ASTM and many industrial methods, is kept free of nonessential material and is written in simple stepwise form for direct reference during the experiment. Alternate procedures are included in some cases where more than one type of commercial equipment is in widespread use.
Effect of copolymers containing imidazole and mercaptan functions on ester hydrolyses
Authors: Overberger C. G. , Pacansky Thomas J. , Lee J. , St. Pierre T. , Yaroslavsky S.
Published: June 2010

Copolymers containing imidazole and mercaptan groups were investigated as possible synthetic models for the proteolytic enzymes, ficin and papain. Three different types of thiol‐protecting groups were screened to prepare the polymers containing free mercaptan functions: a base‐sensitive group (vinyl thiolacetate), an acid‐sensitive group (methoxy‐methyl vinyl sulfide), and a heat‐sensitive group (S‐vinyl‐O‐f‐butyl thiocarbonate). Removal of the acetyl group occurred in water at neutral pH, presumably due to some intramolecular imidazole catalysis. Similar deacylation steps might follow the acylation of the thiol groups for the copolymers containing imidazole and thiol functions during ester hydrolysis. Acylation rates (rates of ester hydrolysis) for poly(vinyl mercaptan) and several copolymers were studied as a function of pH and copolymer composition. Indications for cooperative effects and apolar binding effects are discussed.
Reactions of epoxide groups of glycidyl methacrylate copolymers
Authors: Kalal J. , Švec F. , Maroušek V.
Published: June 2010

An investigation was made of polymer‐analogous reactions of the epoxide ring bound to the polymer chain with a number of agents such as amines, diamines, hydroxyamines, carboxylic acids, phosphoric acid, phosphorus pentoxide, thiourea, etc. The polymers used were homogeneous or slightly reticular gels. All reactions were considerably affected by the type and thermodynamic quality of the solvent. Reactions with the amino compounds were greatly dependent on their basicity and on the size of the alkyl groups. By using diamines one can obtain a material containing free amino groups capable of further reactions. A sufficiently high conversion of the reaction of the epoxide group with carboxylic and mineral acids could be achieved only in an anhydrous medium. In other media acid‐catalyzed hydrolysis predominated, along with the required addition reaction. If the reaction mixture was treated with thiourea and then left to react with hydrogen sulphide, a polymer gel was formed containing two vicinal thio groups able to bind heavy metals.

The reactions described show that the epoxide group bound in the copolymer allows a number of reactions which lead to products with properties markedly different from the starting material.
Dynamic viscoelastic behavior of polybutadiene networks
Authors: Kraus Gerard , Rollmann Kent W.
Published: June 2010

Dynamic viscoelastic properties of polybutadiene networks, prepared by conventional sulfur vulcanization of polymers differing in primary molecular weight, molecular weight distribution, long‐chain branch content, and branching pattern, were measured in the region of the viscoelastic spectrum of principal interest in dynamic applications of rubbers. At lower frequencies, the storage compliance was found to correlate closely with the fraction of free (terminal) chains in the network, while the loss compliance could be correlated with either the free end fraction or with the fraction of chain entanglements not trapped into the network by primary valence crosslinks. At higher frequencies, approaching the plateau region of the viscoelastic spectrum, effects of network structural features diminished as contributions of untrapped entanglements became more pronounced. Networks prepared in presence of a diluent exhibited the same trends as pure gum vulcanizates. Carbon black produced a leveling effect, ascribed to a second entanglement entrapment mechanism by adsorption sites on the filler surface.
A collaborative study of capillary flow of a highly lubricated unplasticized poly (vinyl chloride)
Authors: Wales J. L. S.
Published: June 2010

Viscometric measurements carried out by ten members of the IUPAC Working Party “Structure and Properties of Commercial Polymers” is summarized and discussed. The participants in the study carried out steady flow measurements with capillary, slit, cone‐and‐plate and concentric cylinder apparatuses. Dynamic viscosities were determined with the Contraves Balance Rheometer.

In this study a highly lubricated material with a relatively low molecular weight was chosen: highly lubricated to aid slip, low molecular weight to obtain a thermal transition at a relatively low temperature.

The influence of capillary length and diameter on the flow curve has been the main subject of this study. Information supplementary to this was obtained with the other equipment.

Above 180°C it was found that the flow curves obtained by the participants were consistent when account was taken of the lengths and radii used by the respective participant. The reason for this seemed to lie in the effect of hydrostatic pressure on the viscosity. There was no evidence at these temperatures of slip at the capillary wall. A change in the radius of the capillary did not alter the measured flow curve except at high shear rates when the effect of shear heating could be seen.

Below 180°C there were indications that wall slippage or other, possibly structural, changes were taking place. However, strong evidence for this was not found by all participants and in some cases the findings were even contradictory.
Recent advances in ziegler polyolefin processes
Authors: Weissermel K. , Cherdron H. , Berthold J. , Diedrich B. , Keil K. D. , Rust K. , Strametz H. , Toth T.
Published: June 2010

The present status and future aspects of polymerization of ethylene and of propylene are reviewed. Main emphasis is directed towards catalyst development, but the general features of some new polymerization processes are also described.
Étude Spectroscopique De La Formation De Complexes Par Liaison Hydrogène Entre La Polyvinylpyrrolidone Et Des Acides Carboxyliques Perfluorés
Authors: Léty‐Sistel Chantal , Sébille Bernard , Quivoron Claude
Published: June 2010

Nous avons étudié par spectroscopie infra‐rouge, la formation de complexes par liaison hydorgène entre la polyvinylpyrrolidone et les acides trifluoroacétique, perfluoropropionique et perfluorobutyrique en solution dans des solvants halogénés. L'association est quantitative et aboutit à la formation de complexe 1:1 dans tous les cas. L'augmentation du nombre d'atomes de fluor tend à favoriser l'etablissement d'une structure particulière du complexe.
Curing of epoxy resins. I. Statistics of curing of diepoxides with diamines
Authors: Dušek K. , Ilavský M. , Luňak S.
Published: June 2010

The curing of epoxy resins with amine curing agents has been statistically treated as irreversible alternating polyaddition with the aid of the theory of cascade processes for cases when the polymerization of epoxy groups and cyclization are negligible. The coefficients of vectorial generating functions are obtained by solving kinetic differential equations. The solution has been carried out for the reaction of diepoxide with diamine with an independent reactivity of epoxy groups in diepoxide and amino groups in diamine, but with a different reactivity of hydrogen atoms in the primary and secondary amino group. Relationships have been derived for changes in the molecular weight averages, in the sol and gel fractions and their composition, and in the concentration of elastically active network chains as a function of conversion. The conditions for the gel point have been determined. The structural parameters depend on the ratio of the rate constants of hydrogen atoms in the primary and secondary amino group, k2/k1 = r, and on the stoichiometric ratio of functionalities. In a stoichiometrically equivalent system the critical conversion at the gel point increases from 1/2 for r → oo up to (1/2) (51/2 – 1) for r → 0. The critical stoichiometric ratio for gel formation at full conversion of (epoxide) functionalities in deficiency is < 3 or > 3 for r < 1 or r > 1, respectively.
Cyclization in crosslinking polymerization. I. Chain polymerization of a bis unsaturated monomer (monodisperse case)
Authors: Dušek K. , Ilavský M.
Published: June 2010

Cyclization in the chain polymerization of bis unsaturated monomers has been treated by cascade formalism based on primary chains for a kinetically controlled reaction. The primary chains consist of repeat units bearing an unreacted (pendent) double bond and units engaged in effective branchings (crosslinks), or cycles. Calculation of the participation of the units of individual types is based on the probability for growing macroradicals of different lengths to react with double bonds of the monomer, or attached to other (branched) macromolecules, or with double bonds on the same growing macroradical and on primary chains already attached to it (multiple crosslinking). The cyclization probability is controlled by the conformational statistics of the linear sequence of bonds between the reacting functionalities. Correlations due to already existing cycles are not considered. Differential increments of units of different types are integrated. Relationships have been derived which characterize the degree of unsaturation, cyclization, and effective branching as a function of the degree of polymerization of the primary chains, chain flexibility, dilution, and conversion up to the gel point, and conditions for the gel point. In this part, systems with monodisperse primary chains have been treated, two variants for the calculation of the cyclization probability based on the average and variable composition of the growing macroradical have been discussed, and the effect of multiple crosslinking has been evaluated.
Calculation of the copolymerization parameters in the ternary copolymerization system of styrene/m‐divinyl‐benzene/p‐divinylbenzene
Authors: Schwachula G.
Published: June 2010

The r‐values of styrene with p‐divinylbenzene or m‐divinylbenzene (DVB), respectively, as determined by several authors, deviate strongly from the ideal straight line in the binary polymerization diagram. In an attempt to convert the various r‐values into coincident e‐and q‐values according to the equations of Schwan and Price. log r1 = (1 T) [6.79 (q1 ‐ q2) ‐ 3.63 1( 1 – 2)] and log r2 = (‐ 1 T) [6.79 (q1 ‐ q2) + 3.63 2 ( 1 ‐ 2)] good agreement was found for several r‐values, while others gave results that could not be evaluated. From a couple of ‐ and q‐values of p‐divinylbenzene and m‐divinylbenzene, the unmeasured r‐values between p‐divinylbenzene and m‐divinylbenzene were computed according to Schwan and Price. Using these r‐values, the ternary, copolymerization system of styrene m‐divinylbenzene/p‐divinylbenzene was computed approximately for various molar ratios of p‐divinylbenzene to m‐divinylbenzene (2:1 1:4) according to Alfrey and Goldfinger. It was shown that p‐divinylbenzene has an essential influence on heterogeneity in a ternary system, too.
Functional monomers and polymers containing nucleic acid bases
Authors: Takemoto Kiichi
Published: June 2010

In order to prepare simply designed, nucleic acid analogs, a series of monomeric compounds containing purine and pyrimidine bases, such as vinyl, epoxy, dicarboxylic acid, propanediol and amino acid types, were synthesized. By polymerizing and polycondensing these monomers, different types of synthetic polymers with functional side groups were successfully obtained. As for the properties of the polymers prepared, base‐base interactions were studied in detail by measuring ultraviolet, NMR, and emission spectra. By utilizing these specific absorption characteristics, application for separating special base from base mixtures by chromatographic techniques is possible. High polymers with stereoregular structures were prepared which could be used as matrices for template polymerization using special base‐base interaction, as observed widely in the natural nucleic acid molecules. Further problems are considered and discussed.
Temperature dependence of the structure‐forming processes in gelatin films
Authors: Coopes I. H.
Published: June 2010

The development of structural order in gelatin films dried at various temperatures is studied by means of optical rotation and lateral swell measurements. The films, which are very thin and are dried quite rapidly, have a comparatively low proportion of helical content. A certain degree of orientation of amino acid units in the nonhelical segments is suggested. The variation of rate of helix formation with temperature is found to follow a modified Flory‐Weaver equation. This relationship is confirmed by lateral swell data.
Spectroscopic observation of the propagating species in the cationic polymerization of vinyl monomers
Authors: Kunitake Toyoki , Takarabe Kunihide
Published: June 2010

The reaction of several vinyl aromatic monomers with CF3SO3H and H2SO4 was carried out in di‐chloroethane at 30°C. The rapid formation of the cationic species was followed by the stopped‐flow method, and the transient species were identified by rapid‐scan spectra and rapid quenching of the reaction mixture. The monomeric cation was formed predominantly in the reaction of 1,1‐diphenylethylene and excess CF3SO3H; however, an indanic dimer was formed in the presence of excess diphenylethylene. The rate constant for the formation of the cationic species was (3∼4) × 103 M−1.sec−1. On the other hand, the reaction of diphenylethylene and H2SO4 produced two short‐lived species: the monomeric cation and, probably, a monomeric radical cation. The transient species (lifetime ∼50 msec) were similarly observed in the reaction of CF3SO3H with styrene, methylstyrenes, and indene.