bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the orientation phenomena by fiber formation from polymer melts. Part I. Preliminary investigations on polycapronamide
Authors: Ziabicki Andrzej , Kedzierska Krystyna
Published: April 2003

The problem of the mechanism of macromolecule orientation occurring in the formation of fibers from polymer melts has been qualitatively analyzed. As a result of birefringence, x‐ray, and spinning stress investigations carried out on polycapronamide fibers, the main parameters determining orientation have been established. They are the parallel velocity gradient along the spinning length, G = dV/dl, and the relaxation factors. The deformation ratio S (the ratio of final to original linear velocity), analogous to the draw ratio λ = 1/10 in the cold‐drawing process, has no influence on the degree of orientation. The orientation by spinning is not accompanied by any such structural transformations as occur through cold‐drawing. The fibers spun at high velocity gradients consist of well‐oriented β‐polycapronamide. It is thus assumed that the orientation proceeds in the region of the liquid melt‐stream as a result of simultaneous action of velocity gradient and thermal relaxation. This mechanism, analogous to that causing the familiar streaming orientation of polymer solutions in capillaries or in a Couette apparatus, is different in principle from that of the cold‐drawing process.
The dynamic mechanical properties of nylons
Authors: Kawaguchi T.
Published: April 2003

A study of the dynamic mechanical properties of a series of polyamide polymers and some related polymers has been made over a wide temperature range at about 100 cycles/sec. by means of a vibrating reed method. The character of the β dispersion of the polyamides occurring at about −40°C. is discussed in relation to the chemical structure of the polymers particularly to the amide groups. It is shown that the β dispersion of the linear condensation polymers of this type is influenced by the properties of the polar groups in the molecular chains. The data supports the view recently postulated by Woodward and his co‐workers that the β peak in the polyamides is due to a segmental motion involving nonhydrogen‐bonded amide groups. Finally the correlation between the γ process occurring at about −120°C. and molecular structure is discussed.
Crystallization and orientation of isotactic polypropylene film by stretching
Authors: Sobue Hiroshi , Tabata Yoneho
Published: April 2003

Crystallization and orientation of isotactic polypropylene film by stretching were investigated. The specimen used was a film of thickness 0.03 mm. and had ca. 30% crystallinity in the initial state. It was observed both by x‐ray examination and measurement of density that the crystallization of the stretched film increased proportionally to the stretching ratio. And it was confirmed that a quasi‐crystalline structure was already developed in the low stretching ratio coexisting with the ordinary stable crystalline structures. This quasi‐crystal structure can be easily transformed into the ordinary stable state at above 100°C., as well as the quasi‐crystal structure in melt spinning filament, as described in a previous paper. It was also confirmed that the ordinary stable crystalline part was biaxially oriented by high stretching at room temperature, that is, (110) plane of the crystallite was preferentially oriented perpendicular to the surface plane of the film in the cross section perpendicular to the stretching axis. This phenomenon was elucidated from both the cohesive interactions between lattice planes and the compressive stress in the stretching process.
Effects of gamma radiation on some physical properties of polytetrafluoroethylene resin
Authors: Nishioka Atsuo , Matsumae Kazuyoshi , Watanabe Muneo , Tajima Moritaka , Owaki Masakazu
Published: April 2003

Effects of gamma radiation on the properties, such as melt viscosity, elastic modulus above the melting point, creep fracture time above the melting point, density, and the degree of crystallinity by x‐ray diffraction, of polytetrafluoroethylene resin were studied. When exposed to the radiation from a Co60 gamma source, the melt viscosity falls rapidly with increasing radiation dose above 104 roentgens, and the rubber elasticity above the melting point decreases with increasing irradiation. Also, Zero Strength Time (a creep fracture time test) above the melting point decreases rapidly with irradiation above 103 roentgens; this behavior is attributable to the chain scission and the accompanying decrease in average molecular weight. Density was found to increase with radiation dose at doses higher than 104 roentgens; also, at 2θ = 18° peak in the X‐ray diffraction pattern, which is indicative of crystallinity, increases slightly in sharpness with irradiation.

These facts suggest that gamma irradiation of this polymer produces chain scission and decreases the average molecular weight, and also causes partial crystallization followed by an increase in the density in the amorphous region. Therefore, crosslinking would probably be negligible in this polymer.
Photosensitive polymers. I. Cinnamate esters of poly(vinyl alcohol) and cellulose
Authors: Minsk L. M. , Smith J. G. , van Deusen W. P. , Wright J. F.
Published: April 2003

Cinnamic acid esters of poly(vinyl alcohol) and of cellulose are insolubilized by ultraviolet radiation. This response may be increased by the inclusion of simple organic compounds such as Crystal Violet carbinol and Michler's ketone. A method of measuring this response (in terms of a sensitivity value, S) based upon photographic sensitometry has been devised. Preliminary study indicates that an increase in S is accompanied by an increase in response to the longer wavelengths of light.
Radiation crosslinking of rubber. IV. Ultraviolet and infrared absorption spectra
Authors: Evans M. B. , Higgins G. M. C. , Turner D. T.
Published: April 2003

When purified rubber is exposed in vacuo to high energy radiation, very few conjugated triene groups are formed relative to the number of molecules of hydrogen evolved. This indicates that less than 4% of the hydrogen is evolved from adjacent carbon atoms in the same molecule, a reaction which would have no immediate crosslinking potential. Rather more conjugated diene groups have been detected, but when these are compared together with triene groups relative to the yield of chemical crosslinks it can be calculated that less than 10% of the allylic radical precursors disproportionate. Infrared absorption spectra do not indicate the marked decrease in unsaturation reported by some previous workers. Slight changes in the infared spectra may indicate some cis‐trans isomerization. There is qualitative evidence for a small increase in vinylidene unsaturation.
Estimation of isotacticity in semicrystalline polymers
Authors: Nielsen Lawrence E.
Published: April 2003

A new method is suggested for estimating the degree of isotacticity and the distribution of block lengths in semicrystalline polymers. The method is based upon the maximum attainable crystallinity and its dependence upon temperature. An alternate approach is based upon the dynamic shear modulus and its temperature dependence above the glass temperature.
Failure of foamed elastic materials
Authors: Gent A. N. , Thomas A. G.
Published: April 2003

A theoretical treatment is given which predicts the tear strength of a foamed elastic material. The energy required to break a test‐piece in simple extension is also calculated, on the assumption that tensile failure occurs by catastrophic tearing from a small nick of a similar size to the largest pore present in the test‐piece. The behavior is given in terms of the strength of the matrix, the density of the foam, and the pore size. Measurements of the tear strength, tensile strength, and elongation at break are described for natural rubber foams prepared from latex. A wide range of density is covered (0.09–0.5) giving a variation in tear strength of 9 : 1 and in work‐to‐break of 24 : 1. Satisfactory agreement with theory is found in both cases, indicating that the basic concepts of the modes of failure are correct. It is concluded that uniformity of pore size is required for maximum strength, and a large average pore size for high tear resistance.
Poly(vinyl‐trans‐benzalacetophenone)
Authors: Unruh C. C.
Published: April 2003

Polystyrene has been partially or completely modified to contain varying amounts of vinyl‐trans‐benzalacetophenone units in the polymer chain. Acetylation of polystyrene gave a pure poly(vinylacetophenone) which, when condensed with benzaldehyde, produced varying proportions of vinyl‐trans‐benzalacetophenone in the polymer. These styryl ketone polymers are very sensitive to ultraviolet radiation, thin layers becoming insoluble on brief exposure, yet can be stored in the dark for years without change.
Factors affecting viscose ripening
Authors: Easterwood Marie , Mueller W. A.
Published: April 2003

Ripening of spinnable viscoses has shown dexanthation rates to be constant for sulfate pulps; however, sulfite pulps appeared to ripen slightly faster than the sulfate pulps. The rate of dexanthation was unaffected by changes in alkalinity over relatively narrow ranges, and slightly affected by sulfur and cellulose content. Dilution of the viscose increased the dexanthation rate. A molar activation energy of 23 kcal. was calculated from a study of temperature effects on dexanthation of a high alpha sulfate pine pulp. Changes in salt index with respect to degree of substitution for all viscoses xanthated and dissolved at 25°C. followed the same linear function. For viscoses prepared at lower xanthation and/or dissolving temperatures, the ripening curves exhibited an initial rise suggesting two simultaneous changes: dexanthation and a randomizing of substitution. Split xanthation (the final xanthation step under essentially homogeneous conditions) yielded viscose having random substitution and exceptionally high salt index. As this solution ripened the salt index decreased linearly with respect to degree of substitution and eventually followed the same function as normally xanthated viscose, indicating that the final internal structures of the two solutions are similar.
Flexural deformation temperature of amine‐cured polyglycidyl and poly‐2,3‐epoxybutyl derivatives of phenol
Authors: Aelony David
Published: April 2003

A number of polyglycidyl and poly‐2,3‐epoxybutyl derivatives of phenols were prepared. An attempt was made to correlate the flexural deformation temperatures of the amine cured polyepoxies with the following structural characteristics of the epoxy compounds: per cent oxirane, functionality, ring substituents other than epoxy (such as alkyl, alkenyl, aryl), and substitution of 2,3‐epoxybutyl for glycidyl group.
Polymer–diluent interactions. I. A new micromethod for determining polyvinyl chloride‐diluent interactions
Authors: Anagnostopoulos C. E. , Coran A. Y. , Gamrath H. R.
Published: April 2003

The changes that are observed under magnification when a single polyvinyl chloride particle is immersed in a drop of diluent and slowly heated have been explained on the basis of a three‐dimensional network system in which the polymer crystallites act as junction points for the network. The existence of a temperature at which a sharp gel‐to‐sol transformation is observed has been attributed to the melting of the polymer crystallites. The temperature at which this transformation occurs was found to be rate‐independent, reproducible, and characteristic for each polyvinyl chloride–diluent system. At this apparent melting temperature, the volume fraction of the diluent in the swollen particle was shown to approach unity. These findings made it possible, for the first time, to apply to polyvinyl chloride–diluent systems Flory's treatment of the effect of diluents on the crystal melting temperature of semicrystalline polymers. The apparent melting temperatures of polyvinyl chloride with 27 diluents were determined by the above method. The interaction parameter χ for each of the diluents used had been previously reported by Doty and Zable. A linear relationship was obtained when the reciprocal melting temperature was plotted against (1–χ)/V1 for all of the above polyvinyl chloride–diluent systems (V1 is the molar volume of the diluent at the melting temperature). From this plot the values for the extrapolated melting temperature of pure polyvinyl chloride and for the average heat of fusion were calculated and found to be 176°C. and 656 cal./mole, respectively. Based on these findings a micromethod has been developed which can be used to determine the parameter χ of a diluent with polyvinyl chloride from a single determination of this apparent melting temperature. This method also yields the value for the energy of interaction parameter B.
Polymerizable derivatives of long‐chain alcohols. II. Reactivity ratios for the copolymerization of some alkyl acrylates
Authors: Jordan Edmund F. , Doughty Kay M. , Port William S.
Published: April 2003

Monomer reactivity ratios were determined for the copolymerization of some alkyl acrylate esters and, respectively, acrylonitrile and vinylidene chloride. For acrylonitrile (M1), the values found were: for butyl acrylate, r1 = 1.52 ± 0.03, r2 = 0.75 ± 0.18; for octyl acrylate, r1 = 1.93 ± 0.08, r2 = 0.83 ± 0.23; for octadecyl acrylate, r1 = 1.74 ± 0.04, r2 = 0.68 ± 0.18. If it is assumed that there is no change in the magnitude of the kinetic constants with chain length, a value for the generalized alkyl acrylate and acrylonitrile may be calculated and r1 = 1.61 ± 0.04, r2 = 0.50 ± 0.19. Values found with vinylidene chloride (M1) were: for butyl acrylate, r1 = 0.88 ± 0.10, r2 = 0.83 ± 0.02; for octyl acrylate, r1 = 0.87 ± 0.02, r2 = 0.70 ± 0.01; for octadecyl acrylate, r1 = 0.91 ± 0.05, r2 = 1.01 ± 0.01. For the generalized alkyl acrylate, the calculated values were r1 = 0.88 ± 0.04, r2 = 0.84 ± 0.01.
Problems in strain measurement in impact tests on textile materials
Authors: Backer Stanley , Krizik Jan G.
Published: April 2003

The limitations of conventional methods of measuring strain are discussed in light of the structural composition of textile materials. The difficulties introduced in static and impact testing by stress concentration and strain inhomogeneity are considered. The need for two‐point strain measurement in regions of homogeneous strain is emphasized. A low inertia strain‐measuring system utilizing magnetic tape is described as applied to tensile tests at jaw speeds of 1 to 100 ft./sec.
Tensile testing of elastomers at ultra‐high strain rates
Authors: Jones J. W.
Published: April 2003

A tensile and compressive test apparatus actuated by smokeless powder with a test speed capability in the 105 in./min. range is described. Preliminary tensile property data for cast polyurethan elastomer is discussed.
New high‐speed tensile tester for polymer films
Authors: Patterson Gordon D. , Miller Wilfred H.
Published: April 2003

Design characteristics are described of a rotating‐wheel tensile tester suitable for stressing a vertical specimen with a force of 115 kg. through a distance of 15 cm. in a velocity range of 10 to 730 m./min. with no more than 1% loss in velocity, thereby assuring constant speed of grip separation. Provision is made for specimens up to 7.5 cm. width in order to achieve multiaxial distributions of stresses which are important in bag failure and leading to the determination of critical strain rates. Instrumentation provides reliable triggering of stress and strain traces on a double‐beam oscilloscope. Straight‐line travel of the moveable specimen grip is assured by the use of tracks which restrain horizontal motions without hindering the desired vertical motion.
Use of the HLB system in selecting emulsifiers for emulsion polymerization
Authors: Greth Gerald G. , Wilson Joseph E.
Published: April 2003

In the present work a wide variety of nonionic emulsifiers and anionic/nonionic blends of emulsifiers were evaluated in the emulsion polymerization of vinyl acetate and styrene. It was found that the emulsion stability and other polymer emulsion properties are often dependent upon a certain property of the emulsifier known as the HLB value. It has been shown elsewhere that the HLB value can be correlated with a fundamental physical property of the system oil–water–emulsifier, namely, the spreading coefficient of the internal phase liquid on the surface of a 1% solution of the emulsifier in the external phase. In the emulsion polymerization of styrene, good emulsion stability coupled with adequate conversion rate was obtained in an emulsifier HLB range of 13 to 16. For certain emulsifier blends it was found that emulsion viscosity and emulsion particle size were strongly dependent on the HLB of the emulsifier. Similar comments apply to vinyl acetate polymerization, except that the most stable emulsions were obtained with emulsifiers in an HLB range from 14.5 to 17.5. These observations on preferred HLB range apply only to nonionic emulsifiers and anionic/nonionic emulsifier blends, which were the emulsifier types screened in the present investigation. For both styrene and vinyl acetate the most generally satisfactory emulsion properties were obtained in the present work by the use of an anionic/nonionic emulsifier blend (G‐3300/G‐3920).
A new synthetic elastomer based on a chlorophosphonated polyolefin
Authors: Leonard E. C. , Loeb W. E. , Mason J. H. , Wheelwright W. L.
Published: April 2003

A new synthetic elastomer has been obtained based on an ethylene‐propylene copolymer prepared using an organometallic catalyst system. Reactive sites (phosphonyl dichloride groups) are placed on the copolymer chain by treating the polymer with phosphorus trichloride and oxygen. After hydrolysis or alcoholysis of the phosphonyl dichloride groups to phosphonic acid or phosphonic acid esters, vulcanization may be carried out by reaction with metallic oxides, particularly lead oxide. Vulcanizates of the polyolefin elastomer have outstanding resistance to heat, ozone, and oxygen, and have excellent electrical properties. This combination suggests the use of this material in high temperature electrical applications.
Changes in fine structure and mechanical properties induced by cyanoethylation of cotton yarns. II. Reacted without longitudinal shrinkage
Authors: Conrad Carl M. , Stanonis D. J. , Creely J. J. , Harbrink Pieter
Published: April 2003

The cellulose of cotton yarns was reacted with acrylonitrile under conditions preventing their longitudinal contraction. Changes taking place in the fine structure of the fiber were studied by means of optical microscopy, density measurements, x‐ray diffraction, and thermal stress behavior measurements. The results indicate that in spite of the strong tensions developed in the yarns, the reaction proceeds in both the accessible and the crystalline regions with considerable volume expansion and eventual disappearance of crystalline structure. Suggestions of a glass transition temperature appear at substitutions slightly above D.S. = 1. Annealing becomes possible at substitutions above D.S. = 2 with the development of the cyanoethyl cellulose crystal structure and over 40% increase in tensile strength. Changes in tenacity, ultimate elongation, energy of rupture, and immediate elastic recovery were also observed.
Radiation effects in polystyrene
Authors: Kline Donald E.
Published: April 2003

Amorphous polystyrene was subjected to nuclear radiation in doses ranging from 1.2 × 1010 to 3.8 × 1011 ergs per gram. At low temperatures the internal friction of the highly irradiated polystyrene was greater than that of the unirradiated material, and beyond the glass transition, which begins near 370°K., the irradiated sample remained a solid and the internal friction decreased. Below 370°K. the dynamic modulus of the highly irradiated material scarcely differed from that of the unirradiated sample, while beyond 500°K. it was rather high (near 105 psi). At low irradiation doses crosslinking occurred sufficient for the formation of a nonliquefying, three‐dimensional network in the polystyrene, but no changes in the dynamic mechanical properties attributable to irradiation could be detected.
Properties of homopolymers of 2‐methyl‐5‐vinylpyridine
Authors: Gechele Giovanni B. , Convalle Giovanni
Published: April 2003

The physical and technological properties of the homopolymers of 2‐methyl‐5‐vinylpyridine (MVP) are reported. PMVP is rather similar in many mechanical and electrical properties to polystyrene. In addition, the pyridine nucleus imparts to the polymer a strong tendency to absorb water and great ease of quaternization with acids, halides, etc. This suggests applications of PMVP as a polyelectrolyte, a viscosity‐improving agent in aqueous acidic media, etc. However, the water absorption characteristic leads to poor outdoor durability and rapid deterioration of many properties after prolonged exposure to humidity.
Diisocyanate‐linked polymers. III. Relationships between the composition and ultimate tensile properties of some polyurethane elastomers
Authors: Smith Thor L. , Magnusson Alan B.
Published: April 2003

The ultimate tensile properties (tensile strength and elongation at rupture) of various series of polyurethane elastomers which apparently do not crystallize were studied. Elastomers which contained 0–20% isodecyl pelargonate were prepared from polyoxypropylene glycol 2025 (PPG), dipropylene glycol (DPG), trimethylolpropane (TMP), and toluene 2,4‐diisocyanate (TDI); the ratios of ingredients were varied so that all clastomers had approximately the same number of chains per unit volume v and tho same concentration of urethane groups [U]. Unplasticized elastomers were also prepared that were similar except that they were linked by hexamethylene 1,6‐diisocyanate, TDI, m‐phenylene diisocyanate, and naphthalene 1,5‐diisocyanate. Over a wide temperature range, the ultimate proper‐ ties of elastomers in both series were identical at equal values of T − Tg,. Series of elastomers were also preparcd from TMP, TDI, triethylme glycol, and two polyester diols: a 50/50 and an 80/20 copolymer of ε‐caprolactone and methyl ε‐caprolactone. In these series, v was held constant and [U] was varied. Within each series, the ultimate properties were identical at equal values of T − Tg, although the ultimate properties depended on the nature of the polyester diol and were different from those of similar elastomers prepared from PPG. To study the effect of the crosslinker type and the concentration, elastomers having a constant [U] were prepared from PPG, DPG, TUI, and six crosslinkers, three being trihydroxy and three being tetrahydroxy materials. At a given temperature, the tensile strength and ultimate elongation appeared to be inde‐ pendent of the crosslinker type and proportional to ve½ and 1/ve, respectively, the proportionality constants being temperature‐dependent. On these elastomers, equilibrium swelling ratios in benzene and rough values of the per cent sol were also measured and certain relations among these and the mechanical properties were observed.
The strain dependence of rubber viscoelasticity. Part III. Natural and butyl rubber at high extensions
Authors: Mason P.
Published: April 2003

Dynamic Young's moduli are derived from observations of wave propagation in stretched filaments of natural and butyl rubbers. Extensions up to about 700% are studied within a temperature range of −45 to +50°C. and a frequency range of 0.2 to 20 kycles/sec. At constant temperature and frequency both the real (E') and imaginary (E″) components increase with increasing extension. The loss factor (E″/E') decreases with increasing extension, but the decrease is more pronounced for the butyl rubber so that the large difference in damping between the two polymers in the unstrained state is greatly reduced at high extensions. Approximate relaxation spectra are derived for the strained materials on the basis of several assumptions regarding the applicability of the WLF equation. It is found that the spectra are displaced in the direction of longer times by increasing extension; this is equivalent to an increase in the monomeric friction coefficient with extension. The effect is more pronounced for the natural rubber than for the butyl, and consequently the ratio of the friction coefficients (butyl:natural) falls from several hundred unstrained state to approximately 3 at 550% extension.
Viscoelastic properties of the phenolic resin–polyvinyl butyral system
Authors: Takahashi Yūzō
Published: April 2003

The viscoelastic properties of the phenolic resin–polyvinyl butyral system were studied over a wide range of temperature by means of the vibrating reed method, at about 50 cycles/sec., and dielectrically, at 60 cycles/sec. Two mechanical loss peaks due to polyvinyl butyral in the mixed system, occurring at about 100 and 160°C., were readily observed. These peaks are influenced by the curing temperatures, being readily detected in specimens cured in the range 180–200°C. but not in those cured below 170°C. The effect of cure temperature on the appearance of a dielectric loss peak at about 100°C. for the system agrees in trend with the effect of cure temperature on the mechanical loss peak in the same temperature range. This result may lend some support to the hypothesis that the polar functional groups of the system play some important role in the appearance of a loss peak. The loss peak at about 100°C. coincides approximately with the maximum loss peak for polyvinyl butyral in the mixed system, and hence this peak may be due to the second‐order transition of the polyvinyl butyral which seems to be in a heterogeneous state in the specimen. Another peak, found at about 160°C., may be attributed to grafting or crosslinking between the phenolic resin and the polyvinyl butyral, resulting from chemical reaction between the two materials during the curing process, as was shown by results for the mixtures of the phenolic resin with PVB and with two PVB derivatives. A model of the state of dispersion of the two constituents in the system is proposed on the basis of these results. Finally, the loss peak occurring at about −42°C. for the system is clearly attributable to the phenolic resin alone. The molecular mechanism for this dispersion, on the basis of results of viscoelastic and dielectric measurements, may be the local movement of side chains, especially unreacted methylol and amino groups on the phenolic resin molecules, although there is no additional clear support for this conclusion.
Solution properties of diethylacetamide cellulose xanthate in dimethyl sulfoxide
Authors: Cornell R. H. , Swenson H. A.
Published: April 2003

Light‐scattering and viscosity measurements were obtained for seven fractions of the diethylacetamide derivative of cellulose xanthate (DAX) in 90% dimethyl sulfoxide. The degree of substitution (D.S.) range represented by the samples was 0.4 to 1.22; the molecular weight range was 112,000 to 446,000. The following empirical equation between the intrinsic viscosity and D.P.w was found: [η] = (5.63 – 3.35 D.S.) × 10−3 D.P.w. As reflected by the km– D.S. plot, the Martin constants, and the configuration parameters, it was apparent that the low D.S. derivatives are considerably more extended in solution than high D.S. derivatives of the same chain length. Under such conditions, it is apparent that solvent‐polymer interaction has assumed an important role in determining the polymer configuration. The behavior of the DAX molecule in solution was found to be strikingly similar to that of other cellulose derivatives. Hydrodynamic considerations revealed that the behavior in solution appears to approach that of the more flexible synthetic polymers at D.S. levels above 0.9 and molecular weights above 400,000.
Viscoelastic properties of regenerated cellulose sheet
Authors: Wellisch Eric , Marker Leon , Sweeting Orville J.
Published: April 2003

The viscoelastic properties of regenerated cellulose containing several different softeners or water only were investigated. Measurements of creep and Young's modulus were made on the Instron tensile tester, and the creep curves were fitted to a mechanical model consisting of Voigt and Maxwell elements of springs and dashpots in series. The elastic and viscous parameters were determined for the various softened films and compared with each other and with measurements of Young's modulus. It was found that the elastic modulus is a function of the effective molar concentration of the softener in the film which is related to its ability to break hydrogen bonds. The inelastic deformation was found to be a linear function of the heat of vaporization of softener (including water) in the film which is related to hydrogen‐bonding energy. Thus, inelastic deformation requires breaking of interchain hydrogen bonds in contrast to pure elastic deformation which involves stretching of hydrogen bonds. A relationship of the Voigt unit and of the Maxwell unit on the composition of the cellulose‐softener system and on cellulose‐softener interaction has been demonstrated.
Inter‐ and intramolecular order in regenerated cellulose
Authors: Pennings A. J. , Prins W. , Hale R. D. , Rårnby B. G.
Published: April 2003

Cellulose was regenerated from technical viscose as bulk gels and thin films (never dried) and then conditioned by repeated swelling with sodium hydroxide solutions and steam treatments. These extraction and conditioning treatments of the gels increased the crystallinity and decreased the accessibility to water as measured by x‐ray, infrared, and density measurements. The density of the gels increased more during these treatments than one would expect from the increase in crystallinity as measured from x‐ray diffraction. Supported by the combined density, infrared, and D2O‐exchange data, this was taken as evidence that the conditioning also gives a closer packing or an increased order in the so‐called amorphous regions. Both steam‐conditioning and drying decreased the accessibility of thin films as measured by a combination of infrared analysis and swelling with sodium deuteroxide solutions in heavy water (NaOD in D2O). Reports in the literature that regenerated cellulose is completely accessible in dilute aqueous alkali solutions (about 1%) have not been verified. The intensity ratios of the different infrared absorption bands were measured during the gradual swelling and exchange with NaOD of increasing concentrations from 1 to 16% in D2O. The few data available now seem to indicate that hydroxyl groups assigned to intrachain hydrogen bonds in crystalline regions are more resistant to deuterium exchange than hydroxyl groups assigned to interchain hydrogen bonds. Based on these studies the concepts of crystallinity, order, and accessibility to water and swelling agents for regenerated cellulose are discussed.
Sur la dégradation thermique du chlorure de polyvinyle. I. Méthodes expérimentales d'etude cinétique
Authors: Guyot Alain , Benevise Jean‐Paul
Published: April 2003

An apparatus for polyvinyl chloride thermal degradation under isothermal conditions and in a controlled atmosphere is described with precision. Continuous measurement of loss of weight of the sample under degradation and, at the same time, continuous titration of hydrochloric acid evolved, can be carried out. The apparatus consists essentially of a magnetically equilibrated Ugine‐Eyraud balance, in which runs a purified gas stream that picks up volatile products in an argentimetric titration cell, coupled to a titrimeter and recorder. Total precision of simultaneous measurements is 1%. An example of the experimental results is given.
Adherend surface preparation
Authors: Thelen Edmund
Published: April 2003

If an adhesive joint is to be strong and permanent its adherend surfaces must be treated at least to remove oil, dirt, and dust. In addition, control of surface roughness, oxide formations, and sometimes adsorbed water is required. Deposition of chromium atoms or TiO2 is indicated for electron donor metals surfaces, and treatments may be useful to protect the adhesive from the adherend or vice versa, or to make their structures more congenial.
Potential of adhesives for the future
Authors: Epstein George
Published: April 2003

Rapid technological advancements have contributed to the increasing application of adhesives. Because of these accomplishments, because of continuing materials research and process development activities, and because of their inherent advantages, adhesives have a great potential for the future. Requirements for the future impose a severe challenge on developmental capabilities. More severe structural requirements and environmental conditions may be expected. Because of increasing complexity and costs, there are requirements for significantly higher orders of reliability and lower fabrication costs. Improvements in bonding processes and development of comparatively new techniques are desirable. Test methods require further development and standardization—especially nondestructive methods. Continuing work in collecting and reporting pertinent information, especially on properties and design parameters for adhesive bonding is helping to advance the utilization of adhesives. Current trends indicate that adhesives are progressing from the realm of “art” to science, a factor which should substantially aid in advancing the future potential for adhesives.
A flywheel impact test for measuring physical properties of tire cords
Authors: Parker J. P. , Kemic C. S.
Published: April 2003

The development and operation of a dynamic tire cord testing apparatus is described. The apparatus consists of a rotating wheel which applies a transverse load to a tire cord and carries it to break. It can be operated at speeds which impact tire cord at velocities of from 10 to 80 ft./sec. The techniques used for detecting, recording, and calculating energy load‐elongation characteristics and time to break are described. Some data showing the effect of impact velocity on the physical properties of nylon, rayon, and polyester tire cords are presented.
The viscoelastic behavior of isotactic polypropylene fibers
Authors: Laible Roy C. , Morgan Henry M.
Published: April 2003

The stress‐strain properties of isotactic polypropylene yarn have been studied over a wide range of strain rates up to 2,000,000% per minute. The testing equipment used included the Instron, three pneumatic and pneumatichydraulic type of high speed testers, the falling weight method, the rotating disc longitudinal impact and ballistic techniques. Evaluation of the behavior of polypropylene at strains of 2, 6, 12, and 16% shows the existence of two relaxation peaks, one at τ = 10−2 sec. and the other at about 102 sec. with a plateau of little time dependency in between. The data, especially at the shorter testing times, can be well represented by a single mechanical model composed of two Maxwell units in parallel. Information concerning the ultimate properties of isotactic polypropylene yarn was also obtained. The work‐to‐rupture values for polypropylene at most strain rates exceed those characteristic of any other available textile material.
Investigations of the phenomena of coacervation. Part III. Phase equilibrium in the three‐component system toluene–ethanol–polystyrene
Authors: Utracki Lechoslaw
Published: April 2003

The goal of this work was to prove that the phenomenon of cacervation was one of the phenomena of phase separation determined by the general laws of thermodynamic phase equilibrium. In this connection, the toluene–ethanol–polystyrene system, known from the literature to be capable of forming coacervates: was studied, and the binodial curve as well as a number of semiempirical coefficients necessary for its theoretical determination established experimentally. For the latter purpose use was made of a generalized form of Maron's equation for the thermodynamic potential of mixing. The experimental and theoretical data showed good agreement. It was therefore concluded that systems capable of forming coacervates are subject to the general laws of thermodynamic equilibrium, and formation of coacervates is a phenomenon within the limits of a simple phase separation.
Polyspiroacetal resins. Part I. Initial preparation and characterization
Authors: Cohen Saul M. , Lavin Edward
Published: April 2003

The reaction of various dialdehydes and one diketone with pentaerythritol or pentaerythritol–dipentaerythritol mixtures, has produced a series of thermoplastic, Polyspiroacetal resins. These possess molecular weights up to 10,000, solubility in a limited range of solvents, and high melting points. Some of these, with an optimum amount of crosslinking, have produced transparent, tough, flexible films.
Rheological properties of viscose
Authors: Hopkins T. E. , Whatley J. W.
Published: April 2003

The steady‐state flow of viscose in a capillary tube viscometer was investigated to determine the rheological properties of this fluid as a function of cellulose concentration and molecular weight. It was found that the flow consistency index increased with increasing cellulose content at constant molecular weight. The flow behavior index was not affected under these conditions. At constant cellulose content, the flow behavior index was found to decrease as the molecular weight of the cellulose molecule was increased. Steady‐state velocity profiles for viscose flowing in a round tube under laminar conditions are also presented as a function of the flow behavior index.
Energy deposition in polymers by reactor radiation
Authors: Jacobs A. , Kline D. E.
Published: April 2003

The temperature distribution in small polymer samples has been used to determine the rate of energy deposition by nuclear reactor radiation as a function of distance from the reactor core. Polyethylene, polystyrene, poly(hexamethylene adipamide), polytetrafluoroethylene, and polymerized epoxy resin were employed as specimen materials. The results for some of these are compared to calculated values based on a simplified radiation spectrum. The values are in good agreement, and it is thus suggested that the calculational method is valid for estimating the integral epithermal neutron flux and the relative energy deposition in different polymers.
Mechanism of discoloration of irradiated polyvinyl chloride
Authors: Ohnishi Shun‐Ichi , Nakajima Yoshiharu , Nitta Isamu
Published: April 2003

The radiation chemical process in polyvinyl chloride has been studied by means of electron spin resonance, optical spectroscopy, and measurement of gas evolution. The chief technique was to irradiate samples at −196°C. and then follow the change or changes with rising temperature. Resonance results showed that, on irradiation, several primary radicals, such as CH2ĊHCH2, CHClĊHCHCl, etc., were produced. Among them some CH2ĊHCH2 radicals could recombine to form crosslinks during irradiation even at −196°C. A mechanism for the discoloration of PVC, based upon results obtained by these three different methods, has been postulated. Discoloration is caused by the formation of polyenyl radicals or polyene molecules of considerable conjugation lengths, some as long as 9 conjugated double bonds. Polyenyl radicals are produced as a result of a thermally induced secondary reaction of the CHClĊHCHCl radical, above −70°C., thereby accompanied by hydrogen chloride detachment following the so‐called “zipper” mechanism. An equation relating the pressure of evolved HCl to the reaction temperature has been derived by a simple kinetic treatment of the zipper reaction. Some effect of heat treatment and increasing dose on discoloration was discussed.
Studies in hard rubber reaction. Part I. Heat of hard rubber reaction
Authors: Bhaumik M. L. , Banerjee D. , Sircar Anil K.
Published: April 2003

A method for the determination of heat of hard‐rubber reaction by the application of differential thermal analysis is reported. The heat of reaction was determined with stocks containing different rubber/sulfur ratios and also with a 68/32 stock, preheated to contain different amounts of combined sulfur. Heat evolution is observed first with samples containing about 7% sulfur and therefrom the amount of heat evolved shows a nearly linear increase up to 30% sulfur. With increasing combined sulfur in the 68/32 stock, the quantity of exothermic heat gradually diminishes; so also does the temperature of initiation, i.e., the temperature at which heat evolution appears to begin. Initiation of exothermic reaction appears to be a function of composition and temperature of the mass. An increase in the rate of reaction was observed when the composition reached 0.5 g.‐atom of sulfur per isoprene unit. An endothermic dehydrogenation reaction is observed at the end of the hard‐rubber reaction. This, however; does not affect the determination of exothermic heat, because there is similar dehydrogenation taking place in the reference material (ebonite) which almost balances this heat loss. The final product has a lower sulfur content due to loss of sulfur as hydrogen sulfide.
Oxidation of rubber vulcanized with a sulfenamide accelerator
Authors: Bevilacqua E. M.
Published: April 2003

The solubility and the volatile product yields after oxidation from rubber vulcanized, with sulfur accelerated with an MBT‐selfenamide have been compared with the same quantities for peroxide and TMTD vulcanizates. No significant difference was found. It is concluded that the chain scission mechanism is independent of the nature of the crosslinking.
High‐shear capillary viscosity studies on concentrated copolymer solutions
Authors: Chinai Suresh N. , Schneider William C.
Published: April 2003

Flow behavior of ten copolymer solutions of polyacrylonitrile and polymethyl methacrylate in concentrations up to 16% was studied at 30°C. with the use of capillaries of constant diameter but different lengths. The shear rate and shear stress range covered were up to 200,000 sec.−1 and 800,000 dynes/cm.2, respectively. A rheological model of the form log D = A0 + A1 (log τ)β + A11 (log τ)2β was employed in determining the inflection point of the flow curve by computer analysis. A marked dependence of the flow curve upon the lenght‐to‐diameter ratio was observed when l/d ratio decreased to below 300. At shear rates above 50,000 sec.−1 the capillary “end effect” corrections and the kinetic energy corrections were found to be large for the concentrated and dilute solutions, respectively. The flow curves were characterized in terms of the inflection point in accordance with the treatment of Schurz. An upper Newtonian viscosity η* was observed at shear rates above 150,000 sec.−1. Up to a concentration of about 1%, the value of the upper Newtonian viscosity was such that the calculated ηsp/C was essentially independent of C and equal to [η*] obtained by extrapolation to infinite dilution. The values of the heat of activation for viscous flow were found to be dependent upon the applied shear stress.
Kinetics of plasticizer migration between nitrocellulose and ethylcellulose in double‐base propellant systems
Authors: Kaufman Martin H. , Ernsberger Fred M.
Published: April 2003

Recent experimental and theoretical work on the concentration‐dependent diffusion of solvents in polymers has led to a reasonably detailed understanding of the processes involved. The possibility exists of supplementing standard but costly surveillance testing with rapid laboratory‐scale measurements of plasticizer migration. Many solvent‐polymer systems conform rather closely to the assumption that the amount of material transferred by diffusion is a function of the composite variable t1/2/l. This means that any scale factor applied to the diffusion path length, in a one‐dimensional system, may be compensated for by applying the square of this factor to the time. It has been shown that this assumption can apply with reasonable accuracy to plasticizer diffusion in the propellant‐inhibitor systems. By approximating a particular 2 in. rocket charge with a one‐dimensional model, it is possible to predict the time required for the unit's inhibitor to reach specified levels of plasticizer migration at any storage temperature of interest. A large temperature coefficient appears to be associated with the equilibrium plasticizer migration in the system chosen for experiment, as well as with the rate. Unless suitable allowance is made, this can lead to serious misinterpretation of the results of the surveillance that has been accelerated by raising the storage temperature.
Electrical conductivity of polypropylene
Authors: Foss Richard A. , Dannhauser Walter
Published: April 2003

The steady‐state (d.c.) electrical conductivity of polypropylene has been measured as a function of temperature (25–150°C.) and field strength (0–94 kv./cm.). The temperature coefficient of the conductivity is 34.6 kcal./mole expressed as an activation energy. This is much larger than the activation energy for diffusion of small molecules in the same polymer. Thus, ionization rather than diffusion appears to be the primary activation process. The conductivity is nonohmic; the conductance quotient is a linear function of field strength but is larger than predicted by Onsager's theory. The ion “jump distance” as evaluated from the isothermal field dependence, is the same order of magnitude as the diffusional mean free path estimated from diffusion studies in other polymers. The conductivity, conduction activation energy, and field dependence appear to be relatively insensitive to polymer crystallinity.
Effect of atmosphere on radiation‐induced crosslinking of polyethylene. Part III. Effect of various gases and effect of electric field
Authors: Okada Yoichi
Published: April 2003

Polyethylene film was irradiated in various atmospheres, i.e., He, Ne, Ar, Kr, Xe, N2, NO, NO2, HO2, CO, CO2, CH4, C2H6, C3H8, and C4H10 by γ‐rays from a Co60 source. Xe, Kr, CO, and H2O (vapor) accelerate the radiation‐induced crosslinking as recently shown in case of N2O. In addition, saturated hydrocarbon gases seem to be accelerative. NO depresses the crosslinking markedly and CO2, mildly. On the other hand, NO2 decomposes the polyethylene molecule without irradiation. Every other gas appears to be inactive. In relation to the effect of gas atmospheres, we examined their solubilities in polyethylene. N2O is one of the most soluble of the inorganic gases. An electric field was applied to polyethylene film during irradiation. The degree of crosslinking evidently decreases with applied field, whether the atmosphere is N2O or Ar.
Strength of filled rubbers: Temperature, rate, and oxygen effects
Authors: Bueche F.
Published: April 2003

The time taken to break under fixed load has been measured for three SBR–filler systems. Two SBR–HAF black systems were used, one vulcanized with sulfur and the other with dicumyl peroxide; the third system was an SBR–silica formulation. Measurements at several temperatures between 30 and 100°C. allowed the computation of an activation energy for the breaking process: 45 kcal./mole for all three systems. By measuring the tensile strength of the filled stock in air and vacuum at various temperatures, it was shown that the presence of oxygen seriously decreases the strength of the filled stock at high temperatures, an effect not present in the gum stock or in silicasilicone stocks.