Showing papers in "Journal of Polymer Science Part C: Polymer Symposia in 1968"
TL;DR: Oligomeric oligoaniline derivatives of diethyl Δ1,4-dihydroterephthalate (V-VIb-d) of diethryl terephthalates (VIIb-D) and linear oligoaniliines (Ib−d) were synthesized and their electric and magnetic properties were studied as mentioned in this paper.
Abstract: Oligomeric oligoaniline derivatives of diethyl Δ1,4-dihydroterephthalate (V–VIb–d) of diethyl terephthalate (VIIb–d) and linear oligoanilines (Ib–d) were synthesized. Ultraviolet spectra and polarographic half-wave potentials corresponding to the first degree of oxidation of linear oligoanilines of type (I) were studied, their iodine complexes prepared, and their electric and magnetic properties studied. Increase of chain length of the base causes increase of λmax of ultraviolet bands, decrease of ionization potential, and increase of electric conductivity of iodine complexes in solid state. The properties of the five-membered oligomer (Ic) differ only slightly from analogous properties of the seven-membered oligomer (Id); the same holds in the case of their iodine complexes. Such substances may be regarded as in some respects models of a linear polyaniline polymer or its complexes.
39 citations
TL;DR: In this paper, the constancy of width divided by polydispersity, W/d, is used to demonstrate a very simple method of determining the poly dispersity of a sample.
Abstract: Formulas are developed for describing resolution in gel permeation chromatography (GPC) in polymer analysis. Simple caluclations permit easy determination of the effect of variables on the resolution. Through the use of two characterized polymer samples the specific resolution Rs can be calculated. From the specific resolution the percent of fractionation between any two or more populations can be predicted or, conversely, a GPC curve can be analyzed for the component molecular weights and molecular weight distributions MWD and then the per cent fractionation between the components calculated. This is especially useful in preparatory scale separations and purifications. The principle of the constancy of width divided by polydispersity, W/d is developed and used to demonstrate a very simple method of determining the polydispersity of a sample.
27 citations
TL;DR: In this article, a computer program has been written that utilizes one of the integrated forms of the copolymer equation and thereby includes the conversion corrections in the treatment of the data, with less direct computational effort on the part of the investigator.
Abstract: The classical methods of determining relative reactivities of monomers to free-radical polymerization, namely polymerization to low conversion of several initial monomer compositions, purification of the polymers formed, compositional analysis, and fitting of the data to the differential form of the copolymer equation by any of several techniques, suffer from several problems. In particular, the various methods of treating the data assume no change in monomer composition at low conversion. This is a reasonable approximation when the reactivities are similar, but when they are grossly different (e.g., r1/r2 > 100), even 2 to 3% conversion can cause highly significant shifts in the monomer composition, particularly for those points where the more reactive monomer is present in relatively small amounts. Illustrations of the potential magnitude of these errors are provided. A computer program has been written that utilizes one of the integrated forms of the copolymer equation and thereby includes the conversion corrections in the treatment of the data. This procedure should yield more precise r1 and r2 values than the classical techniques, with less direct computational effort on the part of the investigator.
18 citations
TL;DR: In this paper, the authors measured the dielectric properties of polytetrafluoroethylene and copolymers with a temperature range of −40 to +180°C at frequencies of 10 Hz to 300 kHz.
Abstract: Precision measurements of dielectric properties of polytetrafluoroethylene and copolymers of tetrafluoroethylene and hexafluoropropylene were made over a temperature range of –40 to +180°C. at frequencies of 10 Hz to 300 kHz. Polytetrafluoroethylene exhibited the typical dielectric behavior of a nonpolar substance: no dielectric loss peak was found over the experimental range of temperature and frequency. The dissipation factor remained constant, being about 2 × 10−5. Copolymers of tetrafluoroethylene and hexafluoropropylene showed two dielectric loss peaks: one occurred at about 100°C. and the other at about −20°C. There was a break point, or an abrupt bend, near 60°C. in the curve of dielectric constant versus temperature, indicating the existence of a transition point. The high- and low-temperature loss peaks correspond to the α and γ relaxations, respectively, which have been found for the mechanical behavior of this copolymer. The dielectric relaxation in the copolymer was attributed to the slightly polar nature of the perfluoromethyl side groups. The activation enthalpy and entropy are 80 kcal./mole and 180 eu for the α relaxation and 12 kcal./mole and 15 eu for the γ relaxation, respectively. The σ and γ relaxations are discussed in connection with the molecular motion of the copolymer chain.
18 citations
Abstract: Gel permeation chromatography (GPC) applied to solutions of cellulose trinitrate in tetrahydrofuran (THF) has shown very promising results. Cellulose trinitrate was selected as the most suitable derivative for use in GPC because of several factors. The so-called “solvent impurity” peak found in the chromatograms was shown to arise from dissolved air; the broadening of the peak observed with sample solutions was found to arise from other solvents and moisture. Indications are that THF does not rapidly degrade the dissolved trinitrate if the solution is stored with reasonable care. Nor did the dry trinitrate stored in a desiccator with exclusion of light degrade appreciably. Four cottons (one unpurified and three purified), two hardwood pulps, and two blends of hardwood and softwood were studied. Curves for the cottons indicated fairly broad, unimodal distributions. These were broadened considerably by acid hydrolysis. The degrees of polymerization (DP), although high, reflected the treatment applied. Wood pulps showed distributions broader than cotton, with much lower DP material, but also some material of even higher DP. A possible source of the latter is discussed. The distributions for the wood pulps were similar within the pairs but markedly different between the pairs. Some correlations were noted between GPC and pulp analytical data. Factors in the GPC technique itself, which may bear on the magnitude of the computed DP's, are pointed out and discussed.
16 citations
TL;DR: In this article, fluid polystyrene samples are converted into the glassy state at 20°C and 1 atm. pressure by two different routes: (a) by cooling at 1.5 atm and 1.6 atm pressure, and (b) by heating at 1250 atm, and then decompressing.
Abstract: Samples of fluid polystyrene are converted into the glassy state at 20°C. and 1 atm. pressure by two different routes: (a) by cooling at 1 atm. pressure and (b) by cooling at 1250 atm. and then decompressing. The heats of solution of the samples are determined in toluene at 30°C. The samples are found to have similar enthalpies, although their densities are different. An attempt is made to explain the results in terms of freezing of rotational isomerism at the glass transition temperature.
15 citations
TL;DR: In this paper, the simulation of steady-state styrene polymerization in a single, continuous, stirred-tank reactor (CSTR) at high viscosity, a train of three CSTR's with and without recycle, and a single imperfectly mixed CSTR.
Abstract: This paper reports the simulation of steady-state styrene polymerization in a single, continuous, stirred-tank reactor (CSTR) at high viscosity, a train of three CSTR's with and without recycle, and a single, imperfectly mixed CSTR. Monomer conversion and polymer molecular weight distribution (MWD), measured experimentally by gel permeation chromatography, were used as criteria of simulation. Earlier results for the single CSTR were used to modify the catalyst efficiency f and termination rate constant kt, to account for the effect of viscosity, μ. The regression equations obtained were log μ = −1.06 −0.522 log (S + 1) −8.34 log (1 − PF) + 0.565 logrw, log (f/fi) = 0.022 log (1 + μ) −0.0285 [log (1 + μ)]2, and log (kt/kti) = 0.060 log (1 + μ) −0.0934 [log (1 + μ]2, where μ is reactor viscosity in centipoise, S is solvent concentration in g-mole/1., PF is polymer weight fraction, rW is weight-average chain length, and fi and kti are values at zero conversion. The theoretical models for the single CSTR and train of CSTR's simulated the behavior of the real, bench-scale CSTR's over a range of experimental conditions. The model for the CSTR system was applied to a theoretical mixing model made up of perfectly mixed CSTR's.
15 citations
TL;DR: In this paper, the authors compared the data from the gel permeation chromatograph with the data obtained from absolute measurements for calculating Q, the constant used for converting Aw and An to the corresponding Mw and Mn values.
Abstract: The Gel Permeation Chromatograph has been used for obtaining values of weight-average and number-average molecular sizes Aw and An and the heterogeneity indices Aw/An for a series of polypropylenes. Absolute values of Mw and Mn, the weight-average and number-average molecular weights, have also been obtained from the same samples with light-scattering and osmotic pressure methods. Comparisons of the data from the gel permeation chromatograph with the data from the absolute measurements have been used for calculating Q, the constant used for converting Aw and An to the corresponding Mw and Mn values. Other correlations of interest, such as intrinsic viscosity versus weight-average molecular weight and melt flow, and Newtonian viscosity versus weight-average molecular weight, are also given.
15 citations
TL;DR: In this article, Copolymerization of N-carboxy-γ-benzyl-D- and L-glutamate anhydride was examined in N,N-dimethylformamide with n-hexylamine as initiator.
Abstract: Copolymerization of N-carboxy-γ-benzyl-D- and L-glutamate anhydride was examined in N,N-dimethylformamide with n-hexylamine as initiator. Rate increase was observed in the initial stage of polymerization of monomers with 55% and 87% L composition. The occurrence of asymmetric selection of monomer antipode was confirmed by optical-rotation measurement of the polymers in trifluoroacetic acid as well as by optical rotatory-dispersion measurement. Observed asymmetric selection and rate increase were discussed in relation to stereoregularity and to helix content of the polymer.
14 citations
TL;DR: In this paper, low-frequency dynamic viscoelastic measurements have been made on solutions of four polystyrenes with nearly uniform molecular weights (M) ranging from 19,800 to 860,000, in three chlorinated diphenyls covering a wide range of viscosities, at concentrations (c) up to 0.35 g/ml.
Abstract: Low-frequency dynamic viscoelastic measurements have been made on solutions of four polystyrenes with nearly uniform molecular weights (M) ranging from 19,800 to 860,000, in three chlorinated diphenyls covering a wide range of viscosities, at concentrations (c) up to 0.35 g./ml. The steady-state compliances (Je), derived from these measurements, are proportional to M/c for M ≥ 82,000 and c ≥ 0.08 g./ml., and their magnitudes agree with the prediction of the Rouse theory. For M = 19,800, Je is abnormally small, and the frequency dependence of the viscoelastic properties also deviates from both Rouse and Zimm theories, suggesting that the molecular length is too small for applicability of the Rouse-Zimm model. At decreasing concentrations deviations from M/c proportionality occur for two reasons: the magnitude of Je shifts from the Rouse prediction to the Zimm prediction, and the concentration dependence shifts from inversely proportional to directly proportional. Both changes are attributed to the disappearance of coil interpenetration with decreasing concentration, and in qualitative agreement with this interpretation they appear to be correlated with the product of concentration and intrinsic viscosity when data for different molecular weights are compared.
12 citations
TL;DR: In this article, a survey of these anomalies is given, followed by an attempt to explain them from a unitary viewpoint, most of which can be attributed to the enhanced crystallization capability of syndiotactic sequences in the chain.
Abstract: Dilute poly(vinyl chloride) solutions exhibit a number of anomalies, such as dependence of solution properties on polymerization conditions, strong aggregation in some solvents, low solubility of the fraction with the highest molecular weight, and considerable polydispersity of fractions with higher molecular weights. On the basis of the authors' work and the literature data a survey of these anomalies is given, followed by an attempt to explain them from a unitary viewpoint. Most of the phenomena mentioned can be ascribed to the enhanced crystallization capability of syndiotactic sequences in the chain.
TL;DR: In this article, the root-mean-square radius of gyration of polystyrene sample was measured in ten critical consolute mixtures encompassing solubility parameters ranging from 8.1 to 11.4 (cal/cm).
Abstract: The unperturbed root-mean-square radius of gyration of a polystyrene sample was measured in ten critical consolute mixtures encompassing solubility parameters ranging from 8.1 to 11.4 (cal./cm.3)1/2. The values of the intrinsic viscosity and coil size were found to reach a maximum in the vicinity of δp, the polymer solubility parameter. Preferential adsorption of the solvent component in the mixture, by polystyrene, was observed in each of the ternary systems examined. The variations in coil size and intrinsic viscosity were found to be mainly a function of solvent polarity and were not caused primarily by preferential adsorption, which was comparatively small in most of the mixtures.
TL;DR: In this paper, it was shown that poly(alkyl acrylates) and poly(vinyl esters) crystallize as hexagonal cells, regardless of the stereoregularity of the backbone chains.
Abstract: Stereoregular and irregular long-side-chain poly(alkyl acrylates) and poly(vinyl esters) have been obtained. A study of the structure these polymers showed that their crystallization took place as hexagonal cells, regardless of the stereoregularity. Studies of the effect of polymer branching length on supermolecular structure have shown that the minimal length of side chain required for crystallization probably is 10 carbon atoms, regardless of the stereoregularity of the backbone chains.
TL;DR: The mechanism of enzymic film formation of Japanese lacquer via o-quinone derived from urushiol is revealed by the spectral and molecular-weight changes of the substrate under mildenzymic oxidation as well as by the laccase-catalyzed aqueous reaction of urUSHiol homologues.
Abstract: The mechanism of enzymic film formation of Japanese lacquer via o-quinone derived from urushiol is revealed by the spectral and molecular-weight changes of the substrate under mild enzymic oxidation as well as by the laccase-catalyzed aqueous reaction of urushiol homologues.
TL;DR: In this article, it was shown that some catalytic species are able to yield high molecular weight polymers containing selectively two of the several possible geometric isomers; moreover, the two isomers involved are present in equimolecular amounts in a nonsequential arrangement.
Abstract: During an investigation of some structural features in the stereospecific polymerization of conjugated diolefins evidence was obtained that some catalytic species are able to yield high molecular weight polymers containing selectively two of the several possible geometric isomers; moreover, the two isomers involved are present in equimolecular amounts, in a nonsequential arrangement. Up to now equimolecular (cis-1,4-3,4)-polyisoprene, (1,2-3,4)-polyisoprene, and (cis-1,4-trans-1,4)-polybutadiene were obtained with different catalytic systems (among which, monometallic complexes). The preliminary results suggest an alternating propagation mechanism, similar to the one already proposed by several authors for Ziegler-type catalysts. Further work is in progress to prepare new binary polymers of this type, with different microstructures.
TL;DR: In this paper, the ability of cavitation resulting from intense ultrasonic energy selectively to degrade polymers by fracturing longer chains at a faster rate than shorter chains is investigated as a means of sharpening molecular weight distributions.
Abstract: Methods of producing selected monodispersed samples of addition polymers have gained importance in many phases of polymer research. The ability of cavitation resulting from intense ultrasonic energy selectively to degrade polymers by fracturing longer chains at a faster rate than shorter chains is investigated as a means of sharpening molecular weight distributions. Conflicting degradation theories and experimental findings are reviewed, and new degradation models based on reasonable degradation mechanisms are developed. An IBM 7040–1401 computer was used to simulate degradation for these models. The solutions show in detail how molecular weight distributions are shifted and altered, depending on the kinetic expression used. In all the cases investigated monodispersity is first seen to decrease and then increase as a function of time.
TL;DR: In this article, a new mechanism of initiation by complex compounds was proposed for isobutylene catalyzed by AlBr3 in the presence of some Friedel-Crafts halogenides (TiCl4, TiBr4, and SnCl4) in nonpolar medium and in the absence of H2O.
Abstract: The rate of polymerization of isobutylene catalyzed by AlBr3 in the presence of some Friedel-Crafts halogenides (TiCl4, TiBr4, and SnCl4) in nonpolar medium and in the absence of H2O is much higher than in polymerization catalyzed by AlBr3 alone. The catalytic activity increment decreases in the order TiCl4, SnCl4, and TiBr4. In the system AlBr3TiCl4 the conversion is dependent only on the concentration of AlBr3. A new mechanism of initiation by complex compounds is proposed.
TL;DR: In this paper, the influence of the chemical nature of the solvent on the viscosity of the solution appeared stronger in the higher regions of shear stress and shear rate.
Abstract: By means of capillary and rotational viscometers flow curves of concentrated polystyrene solutions were obtained. The measurements were carried out at concentrations of 0.184–0.573 volume fraction of polymer, shear stresses of 3 × 101−3 × 106 dyne/cm.2, shear rates of 1 × 10−6 to 1 × 106 sec.−1, and temperatures of 15–120°C. It was shown that both the deterioration of quality of solvent and the decrease of temperature increase the initial Newtonian viscosity and facilitates attainment of the upper Newtonian viscosity. The influence of the chemical nature of the solvent on the viscosity of the solution appeared stronger in the higher regions of shear stress and shear rate, that is, at the transition from the initial Newtonian viscosity to the upper Newtonian viscosity. This regularity was explained by the presence of two kinds of structural formation in concentrated polymer solutions: bundles of polymer chains and fluctuational networks composed of the bundles. The bundles can be dissociated in different degrees by good and poor solvents. The paper considers the application of some of the reduction methods to the experimental data.
TL;DR: The early history of the origin and development of gel permeation chromatography is described in this article, where the author's contributions to the origin of gel chromatography are described and the early problems involved the control of gel structure and particle size.
Abstract: The early history of the author's contributions to the origin and development of gel permeation chromatography is recounted. Previous experiences with chromatography and with polymer characterization were of value at the inception. Early problems involved the control of gel structure and particle size, column-packing techniques, design, and test methods for the instrumentation. Aid from co-workers is acknowledged.
TL;DR: In this article, a mixture of l- and dl-menthyl methacrylates were polymerized with phenylmagnesium bromide coordinated with l-MENTHyl ethyl ether, and l-and dl -amyl-magnesium-bromide as catalysts.
Abstract: Mixtures of l- and dl-menthyl methacrylates were polymerized with phenylmagnesium bromide coordinated with l-menthyl ethyl ether, and l- and dl-amylmagnesium bromide as catalysts. The isotacticity of the polymers was decreased by the addition of dl-monomer into l-monomer. From the relationship between the decrease of isotacticity and the increase of heterotacticity and syndiotacticity it is deduced that the isotactic sequences in the polymers are composed of either D or L configurations and not mixtures of D and L sequences. The optical activity of the monomer recovered and that of the polymers showed that the preference of one of the enantiomeric monomers over the other in the polymerization did not occur. The polymers prepared with l- and dl-amylmagnesium bromide had the same stereoregularity.
TL;DR: In this paper, four kinds of aminophenylbenzimidazoles were synthesized by reacting 3,3′-diaminobenzidine and 1,2,4,5-tetraaminobenzene with p- and m-aminobenzoic acid.
Abstract: Four kinds of aminophenylbenzimidazoles were synthesized by reacting 3,3′-diaminobenzidine and 1,2,4,5-tetraaminobenzene with p- and m-aminobenzoic acid. These four diamines were polymerized with pyromellitic anhydride and 3,3′,4,4′-benzophenone-tetracarboxylic anhydride. Polymers of highest intrinsic viscosities were obtained by adding the powdered anhydrides to dimethylsulfoxide solutions of the amines. Permutation of the above monomers yielded eight different benzimidazole–aromatic imide copolymers which were cast from solutions and cured at 280°C. to 300°C. in air. The polymer films show excellent thermal stability.
TL;DR: In this paper, N-Benzoylated poly-2-ethylethylenimines of different stereoregularities were prepared, and their optical rotatory dispersions (ORD) were measured in various solvents.
Abstract: N-Benzoylated poly-2-ethylethylenimines of different stereoregularities were prepared, and their optical rotatory dispersions (ORD) were measured in various solvents. The ORD behavior of the regular polymer in cyclic ethers was anomalous, and that of the irregular one changed to a simple dispersion. The result and general optical rotatory properties suggest that the regular polymer exists in a specific conformation, perhaps as a helix, in the solvents.
TL;DR: In this article, the polymerization of 4-vinylpyridine (4VP) in an electrochemical cell in liquid NH3 solutions was studied, and it was concluded that the initiation step consists of electron transfer between the cathode and the monomer.
Abstract: The polymerization of 4-vinylpyridine (4VP) in an electrochemical cell in liquid NH3 solutions was studied. With monomer concentrations of 5 to 25 vol.-% in the temperature range −33 to −78°C. rapid polymerization takes place when current is passed through the cell. Polymer yields of 80 to 90% are easily obtained in a few hours with NaN3 or NaCl as electrolyte and smooth Pt electrodes in a stirred three-compartment cell. Current densities of 1 × 10−2 to 10 ma./cm.2 and applied voltages of 2.5 to 50 v. were employed. Different anodic materials were used, including Pt and pyrolitic graphite. The electrochemical yield is about 1 mole of polymer per faraday for current densities of ⩽ 1 × 10−2 ma./cm.2, and it becomes 0.5 and lower at higher current densities. The rate of polymerization was found to increase, and the molecular weight of the polymer to decrease, with increasing current density. It is concluded that the initiation step consists of electron transfer between the cathode and the monomer. Depending on the amount of polymer deposited on the cathode and on the current density, initiation may occur on the cathode surface or within the polymer deposit on the cathode or in the free liquid solvent. The consequence of the electron transfer to monomer is the formation of radical anions. Electrochemical yields of about 1.0 mole of polymer per faraday suggest that radical anion dimerization does not take place extensively, while dimerization may predominate when electrochemical yields are about 0.5. Subsequent chain growth occurs through an anionic mechanism, as evidenced by the nonterminating nature of the polymerization, the presistent red color of the polymer formed, and the sensitivity of the polymerization to the addition of protic substances. Polymer molecular weights were in the range of 10,000 to 360,000. Molecular weight distributions with Mw/Mn ratios of 1.21 or larger were found. Softening points, solubility characteristics, and infrared spectra of the electrochemical polymer are presented and discussed in comparison with those of poly(4-vinylpyridine) prepared with chemical initiators.
TL;DR: In this article, the ESR spectra of polypropylene were examined in conjunction with the stereospecificities and regularities of the polymers, and it was concluded that the radical species at room temperature are identical in IPP and SPP except for their steric conformations, and the coupling constants of protons of the radical of SPP were determined in comparison with those reported for IPP.
Abstract: Isotactic (IPP), syndiotactic (SPP) and atactic (APP) polypropylene were irradiated by gamma-rays of 60Co at −196°C., and ESR spectra were subsequently examined in conjunction with the stereospecificities and regularities of the polymers. All the polymers showed similar broad spectra at −196°C. APP gave a well-resolved sextet spectrum above −40°C., which vanishes at about −10°C., owing mainly to its glass transition. IPP and SPP showed different spectra characteristic of their stereospecificities in the crystalline phase above room temperature. It was concluded that the radical species at room temperature are identical in IPP and SPP except for their steric conformations. The coupling constants of protons of the radical of SPP were determined in comparison with those reported for IPP, assuming the allyl-type radical CH(CH3)CHCH(CH3)CHCH(CH3)2. The decay process of the radicals was found to be a second-order reaction. The study shows that only the spectrum of IPP exhibits a singlet when the sample is kept at room temperature in vacuum. The spectrum of SPP is easily saturated compared with that of IPP when the power of the oscillating magnetic field is increased.
TL;DR: In this article, complete hydrogenation of cis-polyisoprene has been effected at 240°C and 3,600 psi of hydrogen pressure over Raney nickel for 48 hours.
Abstract: Complete hydrogenation of cis-polyisoprene has been effected at 240°C. and 3,600 psi of hydrogen pressure over Raney nickel for 48 hr. Only a moderate amount of polymer breakdown occurred. High molecular weight hydrogenated polyisoprene was obtained by fractionating the hydrogenated polymer. Under similar conditions trans-polyisoprene, poly-2-ethylbutadiene, poly-2-n-propylbutadiene, poly-2-n-pentylbutadiene and poly-2-(2-methyl-2-penten-5-yl) butadiene were completely hydrogenated. No rearrangement of the polybutadienes as a result of hydrogenation was observed.
TL;DR: In this article, the polymerization of various monomers in the glassy state was investigated at low temperatures and compared with polymerization in the crystalline state, and it was found that acrylonitrile can polymerize in 2-methyltetrahydrofuran via an anionic mechanism, and the rate of polymerization is much faster than in the crystal state.
Abstract: The polymerization of various monomers in the glassy state was investigated at low temperatures and compared with polymerization in the crystalline state. It was found that acrylonitrile can polymerize in the glassy state in 2-methyltetrahydrofuran via an anionic mechanism, and the rate of polymerization is much faster in the glassy state than in the crystalline. On the other hand, it was observed that acrylonitrile can be copolymerized with vinyl acetate in glassy mixtures of the two monomers over a wide range of monomer concentrations at low temperatures, below about −160°C. From the monomer reactivity ratio of two monomers in the two component system the polymerization is believed to proceed via a radical mechanism. It was also found that propylene oxide can polymerize only in the glassy state, and the rate of polymerization is quite rapid in matrices of methylene chloride. It was suggested from the effect of various additives on the polymerization that the polymerization proceeds via a cationic mechanism.
TL;DR: In this paper, a series of condensations of polycarbonates was carried out, starting with 2,2-di(p-hydroxyphenyl) propane (bisphenol A) and its dichloroformate in two different solvents, for preparation of polymers under equilibrium conditions and under conditions of equilibrium disturbance by an addition of nonsolvent.
Abstract: It has been suggested, on the basis of theoretical considerations, that a polycondensation process in solution can be performed with a shifting of the equilibrium by precipitation of the highest fractions of polymer. A series of condensations of polycarbonates was carried out, starting with 2,2-di(p-hydroxyphenyl) propane (bisphenol A) and its dichloroformate in two different solvents, for preparation of polymers under equilibrium conditions and under conditions of equilibrium disturbance by an addition of nonsolvent. The molecular weights and distribution functions of both products were determined. It was found that the products obtained by this precipitation polycondensation, in agreement with the theoretical assumptions, have considerably higher molecular weights and molecular homogeneity.
TL;DR: In this paper, the stress-strain distributions in the test specimens of various transparent rubber vulcanizates were measured by photoelastic and microscopical techniques, which were of the size specified in JIS-K-6301-b, which was identical with ASTMD-624-54C and DIN 53515.
Abstract: Stress-strain distributions in the test specimens of various transparent rubber vulcanizates were measured by photoelastic and microscopical techniques. The test specimens were of the size specified in JIS-K-6301-b, which was identical with ASTMD-624-54-C and DIN 53515. The tear resistances of the vulcanizates were calculated by a semitheoretical equation derived by taking the measured strain distributions into consideration. The values thus calculated were found to agree with the experimental data obtained for various vulcanizates except for some of natural rubber compounds.
TL;DR: In this paper, the thermal degradation of bisphenol-A and three kinds of epoxy resins cured with aromatic amines were studied, and the aromatic amine curing agents were m-phenyl-enediamine, p,p′-diaminodiphenylmethane and p, p′-sulfone sulfone.
Abstract: The thermal degradation of bisphenol-A and three kinds of epoxy resins cured with aromatic amines were studied. The aromatic amine curing agents were m-phenyl-enediamine, p,p′-diaminodiphenylmethane and p,p′-diaminodiphenyl sulfone. As epoxy resin Epon 828 was used. The sample was pyrolyzed at 500°C. in an electric furnace, and pyrolyzate was examined by gas chromatography and infrared spectroscopy.