bluuebunny/crossref_metadata_2025 huggingface dataset:
Nylon 7, a fiber forning polyamide
Authors: Horn C. F. , Freure B. T. , Vineyard H. , Decker H. J.
Published: April 2003

Eight esters of 7‐aminoheptanoic acid were prepared as monomers for nylon 7 (polyheptanamide). They were made from ε‐caprolactone via the route; 6‐chlorohexanoic acid, alkyl‐6‐chlorohexanoate, alkyl‐6‐cyanohexanoate, alkyl‐7‐aminoheptanoate. The stability of these esters against polymer formation during distillation and at room temperature increased with the number of C atoms in the alcohol. When the esters were heated at 270°C. to form the polyamide, the same trend in stability was observed; the polyamides obtained were of too low molecular weight for melt spinning. Upon heating ethyl‐7‐aminoheptanoate with water (mole ratio 1 to > 3) at 100°C., a mixture of 7‐aminoheptanoic acid with mainly dimeric acid and ester was obtained. This product (“precursor”) was a stable solid at room temperature which could readily be converted at atmospheric pressure within 2 hr. to high molecular weight, spinning grade nylon 7. The melting point, density, moisture regain, and sticking temperature of nylon 7 were compared with those of nylons 6, 8, 9, 10 and 11. Nylon 7 was melt spun into high tenacity yarn and its textile properties were discussed in comparison with those of nylons 6 and 66. The low oligomer content of nylon 7 (1.5%) made extraction of the resin before spinning unnecessary.
Polystyrene modifications. II. Ring‐substituted polystyrenes
Authors: Dunham K. R. , Faber J. W. H. , Vandenberghe J. , Fowler W. F.
Published: April 2003

Ring‐substituted styrenes were prepared and polymerized. They usually had higher glass transition temperatures than polystyrene. In some disubstituted systems the Tg was an additive function of the individual groups. Crystallinities of methyl‐substituted polymers varied, depending upon the ring positions involved. Crazing tendencies were equivalent to those in polystyrene.
The use of sol‐gel analysis to estimate chain scission during vulcanization. Part I. Peroxide vulcanization of natural rubber
Authors: Bristow G. M.
Published: April 2003

Sol‐gel analysis, that is, the measurement of the fraction of rubber remaining unconnected to the network as a function of the degree of cure, has been used to estimate the extent of chain scission in the vulcanization of natural rubber with dicumyl peroxide at 130°C. For peroxide concentrations in the range 1–5% and masticated rubbers of M̄n = 0.84–2.67 × 105 there are only 1–3 sites of scission per 100 crosslinked isoprene units.
A study of the oxidative degradation of furfuryl alcohol polycondensates by infrared spectroscopy
Authors: Conley Robert T. , Metil Ignatius
Published: April 2003

The oxidative curing and oxidative degradation of cured furfuryl alcohol polycondensates was examined, with infrared spectroscopy, by following the functional group changes occurring in the solid phase of the resin. It has been found that the oxidative degradation of nitrogen‐cured resins initially proceeds through the oxidation of methylene linkages to bifuryl ketonic species activated by adjacent furan rings. The second stage of oxidation is the scission of the bifuryl ketonic chain positions to produce substituted furoic acids. The process is postulated to proceed in a manner analogous to that observed in phenolic resin systems. The curing of furfuryl alcohol resin in air is shown to be a multistep process in which the initial oxidation of methylol groups to carboxylic acids is competitive with further polymerization through methylol condensation at adjacent furan ring alpha hydrogen positions. In addition, the oxidation of already formed methylene linkages to the bifuryl ketones is a competitive process removing methylene linkages after they are produced during further condensation (curing reactions). These routes of degradation are in good agreement with observed oxidations of furfuryl alcohol resins under more drastic conditions and offer a reasonable mechanism for resin degradation consistent with observations in analogous polymer systems.
The fine structure of fibers and crystalline polymers. I. Fringed fibril structure
Authors: Hearle J. W. S.
Published: April 2003

The inadequacy of the fringed micelle concept of the structure of crystalline polymers has led to the suggestion of a fringed fibril structure. Single crystal, spherulitic forms of bulk polymer, and oriented fibres are considered, and a modified fringed fibril structure, which will account for long periodicities, is proposed. The fringed micelle structure is viewed as a limiting case of fringed fibril structure. The evidence for and against the fringed fibril structure is discussed. The paper concludes with a survey of structures of different types of polymer and fibers.
Dyeing of polyacrylonitrile fibers: I. Rates of diffusion with malachite green and diffusion model
Authors: Rosenbaum S.
Published: April 2003

Diffusion of the cationic (basic) dye, Malachite Green, into polyacrylonitrile fibers is shown to take place from a saturated surface layer even with relatively low solution concentrations. This makes possible a simple determination of the integral diffusion coefficient from one sorption‐time curve. In place of the commonly accepted model of dye diffusion, in which the fiber elements play a passive role, it is proposed that the motion in the polymer molecules constituting the fiber is the main factor governing the diffusion process at normal dyeing temperatures. In support, data are shown on the temperature dependence of the diffusion coefficient and its relation to fiber composition and mechanical behavior.
Post extrusion swelling of polyethylene
Authors: Bagley E. B. , Storey S. H. , West D. C.
Published: April 2003

When polymers are extruded from a reservoir through a capillary the extrudate diameter is generally greater than the capillary diameter. Experiments with polyethylene show that the extent of this extrudate swelling depends, at constant shear stress, on the length‐to‐radius ratio of the capillary even though the viscosity does not. Consideration of this result at various shear stresses indicates that the degree of swelling depends on the total shear strain imposed on the melt. The same factor also governs the amount of extrudate distortion observed when melt fracture occurs.
Diffusibility and solubility of gases in ethylcellulose and nitrocellulose
Authors: Hsieh Paul Y.
Published: April 2003

Permeability of ethylcellulose and nitrocellulose films to thirteen different gases and vapors was determined. The solubility of these gases and vapors in ethylcellulose and nitrocellulose was also measured by gravimetric and volumetric methods of equilibrium sorption. From these data for permeability and solubility, diffusion coefficients of the gases and vapors in the polymeric films were calculated by means of the relation, P = DS, in which P and S are the permeability and solubility constants, respectively. It was found that the diffusion coefficient D decreased linearly with an increase of molecular weight; however, the shape factor of the molecules played an important role in the diffusion process. The solubility constants increased linearly with an increase of the Lennard‐Jones force constants ϵ/k when solubility was expressed on a weight basis rather than a volume basis. Both ethylcellulose and nitrocellulose are noncrystalline. Higher solubility, diffusibility, and permeability of ethylcellulose than that of nitrocellulose are considered to be due to the molecular packing in the films.
Moisture and ion sorption in cellulose acetate
Authors: Thomas Charles R. , Barker R. E.
Published: April 2003

Measurements described in this paper show that the effective water permeation coefficients of silver paste electrodes on polymers such as cellulose acetate are of about the same magnitude as those of the polymer itself and, therefore, that such electrodes will have negligible effect on moisture penetration when conditioning periods of several hours or longer are used. X‐ray emission spectrography with Kα radiation from chlorine and potassium was employed to determine the salt content of 0.267‐mm. cellulose acetate films (about 100 acetyl groups per polymer molecule = 40% acetyl), which were soaked for 48 hr. in aqueous solutions ranging up to 1M in concentration of the alkali chlorides or potassium halides. Typically, the salt contents are about 100 ppm or 3 μmole/g. of cellulose acetate. The actual salt contents are discussed in relation to ionic hydration, and Stokes' radii via the differential hydration energy concept of Samoilov and the phenomenological developments of Nightingale. The evidence suggests that ionic motion in moisture‐swollen cellulose acetate is quite similar to that in aqueous solution.
Performance of a versatile variable‐volume permeability cell. Comparison of gas permeability measurements by the variable‐volume and variable‐pressure methods
Authors: Stern S. A. , Gareis P. J. , Sinclair T. F. , Mohr P. H.
Published: April 2003

An improved cell which permits the measurement of permeabilities of membranes to gases over a wide range of temperatures and gas pressures is described. The measurements are made by the variable volume method, under constant pressure differential across the membrane. The cell lends itself particularly well to routine tests, because it does not require calibration or the use of vacuum techniques. The performance of the cell is discussed, and typical experimental results are presented. A modified permeability cell of the same type for high‐pressure studies is also described. Measurements with this apparatus show that the rate of gas permeation obeys, in some cases, a single from of Fick's law, even under pressure differentials across the membrane as high as 800 psi (54 atm.). The paper also compares permeability data obtained by the variable volume and the variable pressure methods. The permeability of 0.002 in.‐thick Alathon 15 polyethylene to oxygen and nitrogen was determined between 0 and 50°C. by the two methods, using the same sample of membrane in situ, and the measurements were found to agree within experimental error. Permeabilites of 0.010 in.‐thick samples of Alathon 15 polyethylene to nitrogen, oxygen, helium, and carbon dioxide obtained in the same temperature range by the variable volume method were 15–30% higher than the corresponding data determined by the variable pressure method. This discrepancy could be due to the fact that the variable pressure measurements with the thicker membrances may not have been made under true steady‐state conditions, although permeabilities were determined from apparently linear sections of permeated gas pressure vs. time curves. A critical re‐examination of the methods used to determine permeability constants is suggested.
Polyhydroxyethers. I. Effect of structure on properties of high molecular weight polymers from dihydric phenols and epichlorohydrin
Authors: Reinking N. H. , Barnabeo A. E. , Hale W. F.
Published: April 2003

An interesting series of high molecular weight thermoplastic polymers, based on dihydric phenols and epichlorohydrin, have been prepared. The polymers have, in common, a structure which can be represented by the general repeating unit
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where E is a radical residuum from a dihydric phenol. Certain properties appear characteristic of this class of polymers. All contain some chain branching through the secondary hydroxyl group. They are amorphous, noncrystallizable, transparent, tough, and thermally stable. They show two glassy state transitions, a minor transition at about −70°C. and a major transition at a considerably higher temperature. This family of polymers provides an excellent means for studying structure–property correlations. Data are reported showing the effect of the structure of the dihydric phenol moiety (E) on the major glass transition temperature and on certain barrier properties of a series of these polymers. The polymer prepared from 2,2‐bis(4‐hydroxyphenyl) propane, bisphenol A, is considered typical of this series; its mechanical and physical properties are described in somewhat more detail and compared with properties of certain commercial polymers.
Infrared spectra of irradiated polyethylene
Authors: Luongo J. P. , Salovey R.
Published: April 2003

The irradiation of polyethylene causes a number of molecular rearrangements in the chemical structure of polyethylene. In addition to the significant changes in the type and distribution of unsaturated groups, an infrared comparison of the radiation induced chemical changes that occur in air and in a vacuum showed that the presence of oxygen has a marked influence on the structural rearrangements that occur on irradiation. The infrared spectra of irradiated single crystals prepared by two different means indicated the location of vinyl groups in the crystals and their protection from radiation by aromatic structures. From these data, a number of reaction mechanisms are postulated which can contribute to our understanding of irradiation effects on polyethylene.
Detective work with high speed testing: The location of a phase change area
Authors: Goldblum K. B.
Published: April 2003

High speed tensile tests on Lexan polycarbonate resin were carried out on three grades of material at four test speeds from 200 to 15,000 in./min. and at five temperatures from −30 to +140°C. A consideration of the results of these tests led to a number of interesting conclusions. Among these conclusions was the identification of a plateau in the plots of some of the variables vs temperature in the 125° to 140°C. range. A more complete study of the variation in the tensile yield values of one of the grades of Lexan resin at 2 and 20 in./min. testing speed over the temperature range, and some‐what beyond, has been made to define this unusual effect.
Slip deformation in drawn polyethylene films
Authors: Kurokawa Masataka , Ban Tetuo
Published: April 2003

When well oriented and crystallized high density polyethylene film was redrawn, slip deformation and twin deformation, the mode of which depends upon the redrawing angle to the original drawn structure, could be observed. When the redrawing angle is very small, single slips, the direction of which is [001] to the original drawn structure, and homogeneous deformation bands attached to them are usually observed. The [001] directions of slipped and unslipped regions are slightly at an angle to each other. As the redrawing angle approaches a right angle, kink bands can be observed. From these results we may conclude that the structure of this drawn polyethylene film is very similar to that of a single crystal or metal.
Mechanism of polyethylene oxidation
Authors: Bevilacqua E. M. , English E. S. , Gall J. S.
Published: April 2003

Acetic and formic acids and acetone are products of the oxidation of propylene and ethylene polymers and copolymers. The two‐ and three‐carbon products can be accounted for as the result of intramolecular attack by radicals, leading to β‐oxidation. A high proportion of scissions in polypropylene involves multiple intramolecular attack.
Gelatin coatings and tensile strength of gelatin films
Authors: Norris T. O. , McGraw John
Published: April 2003

Strips of gelatin film were prepared from three commercial gelations and tested for tensile strength on an Instron universal tester. Some of the strips were made from plain gelatin and others from gelatin which had been deionized, treated with formaldehyde, chrome alum, or acetic acid. Strips were also prepared at 10 and 55°C. The results showed the greatest deviation for the acetic acid‐ and heat‐treated gelatins. An attempt is made to account for the results.
Generalized model representation relating the degree of mixing to the rheological behavior of a mechanical mixture of two polymer components
Authors: Fujino Kiyohisa , Ogawa Yasuo , Kawai Hiromichi
Published: April 2003

On assuming that the two polymer components are poorly compatible or incompatible and from semimicro heterogeneous systems composed of homogeneous phases of each component, two kinds of generalized models which relate the degree of mixing of the two phases to the mechanical behavior of the systems were proposed. In this phenomenological theory, the chemical interaction between the two polymer components was negelcted, and the stress or strain distribution along the boundaries between the two phases was much simplified. This might give serious error when the mixed phases become small and the surface effect, instead of volume effect, becomes significant. The mechanical mixtures can be classified by the manner of mixing of the two phases of A and B components as follows: A islands in B matrix, B islands in A matrix, A matrix‐B matrix, and A islands‐B islands mixing. The mechanical properties of the mixed systems are affected not only by those of each component and their volume fraction in bulk, but strongly by the manner of mixing. The terminology used here, as the degree of mixing, is one of the representations of the manner of mixing in terms of distribution function of partial volume fractions of each component in the mixed system.

The analysis of some mixed systems of two polymer components gave the following results. The mixed systems cast from acetone solution of poly(vinyl acetate) and poly(methyl methacrylate) give mechanical mixtures of the islands‐in‐matrix type mixing. A phase conversion from PMMA islands in PVAc matrix to PVAc islands in PMMA matrix occurs at about 70% volume fraction of PMMA due to the hexagonal close packing of PMMA islands in PVAc matrix with increase of volume fraction of PMMA On the other hand, the systems cast from mixtures of acetone solution of PVAc and lightly crosslinked PMMA fine particles give mechanical mixtures of the matrix‐matrix type mixing. The mixed systems of polystyrene and 30/70 butadiene–styrene copolymer, which have been classified by Tobolsky as polyblends, might also be a type of mechanical mixture classifiable as matrix‐matrix mixing. However, the manner of mixing should be much modified by the chemical interaction between the two components.
Ion‐exchange membranes by sulfonation of poly(vinylidene fluoride) films
Authors: Richards G. N.
Published: April 2003

Attempted sulfonation of poly(vinylidene fluoride) film results predominantly in reaction at the surface of the film owing to lack of penetration by the reagents. When the film is pre‐swollen with a wide range of liquids, however, sulfonation with oleum proceeds smoothly through the body of the film, and a flexible membrane of low electrical resistance is produced. The more important variables in the swelling and sulfonation steps have been investigated. Side reactions during the sulfonation lead to the introduction of carbonyl and ethylenic groupings into the polymer molecule. The latter grouping is assumed to be responsible for the lack of stability of the membrane towards oxidants.
Dynamics of viscoelastic fluids, melt fracture, and the rheology of fiber spinning
Authors: White James Lindsay
Published: April 2003

The hydrodynamic theory for the flow of nonlinear viscoelastic fluids is developed. Two new dimensionless groups must be introduced into the complete second‐order correction of viscoelastic flow. These groups are called the Weissenberg and viscoelastic ratio numbers. Applications to industrially important problems are discussed. It is argued that the Weissenberg number determines the onset of melt fracture.
Production of super‐tenacity polypropylene filaments
Authors: Sheehan W. C. , Cole T. B.
Published: April 2003

The effects of the conditions fiber formation on structural parameters and tensile properties of melt‐spun, highly isotactic polypropylene filaments were investigated to determine the feasibility of producing supertenacity polypropylene filaments. Meltspun polypropylene monofilaments were prepared from five highly isotactic polymers (94% or more by extraction), under different conditions of extrusion, quenching, drawing, and annealing. The molecular weight, molecular weight distribution, crystalline structure, crystallinity, crystallite orientation, and total molecular orientation (as expressed by total draw ratio) of the experimental filaments were determined, and the relationships between these structural parameters and the tensile properties of the filaments are discussed in the paper. Several of the experimental polypropylene filaments produced had tenacities greater than 12 g./den. and one of them had a tenacity of 13 g./den. Polypropylene filaments having tenacities greater than 13 g./den. appear feasible. To produce the super‐tenacity polypropylene filaments, a polymer with a weight‐average molecular weight of about 470,000 was melt spun into undrawn filaments having the paracrystalline structure, and the filaments were drawn to a maximum and annealed. The tenacity of the polypropylene filaments increased with increasing fiber molecular weight. A narrow molecular weight distribution was beneficial, but was not necessary for obtaining high tenacities. High draw after spinning was important in producing high tenacity. The maximum amount that a fiber could be drawn depended upon its molecular weight, the amount of stretch introduced during spinning, and the drawing time and temperature (filament temperature). Filaments having the paracrystalline structure, which was obtained with proper extrusion and quenching conditions, could be drawn more easily than filaments having the crystalline structure, and hence, under equivalent conditions, the former could be drawn more. The more the filaments were stretched during spinning, the lower were their tenacities. The relationship between crystallite orientation and the tensile properties of drawn and annealed filaments stretched during spinning was different from the relationship for drawn and annealed filaments that were not stretched during spinning. The highly drawn filaments contained voids, but they could be removed by proper annealing conditions, which also increased the tenacity of the filaments.
Block polymers of styrene and acrylonitrile
Authors: Perry Eli
Published: April 2003

One‐to‐one block polymers of styrene and acrylonitrile were prepared by a two step process: (1) styrene was polymerized in the presence of a dialkylphosphine and (2) the polystyrene was used to initiate the polymerization of acrylonitrile. The blocks contained 14–76% acrylonitrile and were 60–100% pure as judged by extraction with toluene at 110°C. Phase and electron microscopy showed that the block polymers consisted of a continuous polystyrene phase when the acrylonitrile content was less than 70% by weight and of a continuous acrylonitrile phase when the acrylonitrile content was above 70% by weight. The polyacrylonitrile dispersed phase was regular and almost spherical. Its measured size equaled the calculated size, assuming that the spheres had a diameter of twice the length of the fully extended polyacrylonitrile chains. Polyblends of homopolymers were similar to the block polymers in structure, except that the dispersed phase was very irregular in size and shape. The physical properties of blocks and polyblends were similar and were inferior to those of polystyrene homopolymers and styrene–acrylonitrile random copolymer except for modulus and for maintenance of modulus over a temperature range. The random copolymer had the highest strength properties, which fact was attributed to the absence of a two phase system and the presence of psuedo‐crosslinks. The relatively poor properties of the blocks and polyblends were ascribed to the inability of bulk polyacrylonitrile to absorb energy and to the buildup of stress concentrations at the phase boundaries.
Carbon black–polymer interaction: A measure of reinforcement
Authors: Brennan J. J. , Jermyn T. E. , Boonstra B. B.
Published: April 2003

The interaction of carbon blacks with high polymers during the mixing process was studied by using fillers having a wide range of surface characteristics. Glass beads, Graphon, high‐structure blacks, and heat‐treated blacks were mixed with elastomers in the Brabender Plasticorder. With the use as a rubber matrix of a high polymer that did not materially change during the mixing process in molecular weight or viscosity, excellent correlation was found between final torque required for mixing and black structure and between peak torque and bound rubber. Increasing interaction was shown to lead to increased mixing torque, increased Mooney viscosity, increased modulus, and higher state of cure, as measured by swelling. If the high polymer matrix breaks down during the mixing process these influences of interaction are mostly obscured by diminishing molecular weight.
Structural turbulence in polymer solutions
Authors: Ram A. , Tamir A.
Published: April 2003

The appearance of structural turbulence in polyisobutylene solutions at low Reynolds numbers has been detected and analyzed. This type of turbulence is characterized by a critical shear stress rather than a critical Reynolds number. The critical shear stress decreases with increasing molecular weights of dilution. The role of deformability of the polymer chains under shear flow is found to be significant.
Cure rates of phenolic resins by differential thermal analysis
Authors: White R. H. , Rust Thomas F.
Published: April 2003

A method has been developed to show the effect of temperature, catalyst level, resin advancement, and water content on the cure rate of phenolic resins by DTA. This DTA procedure allows for quantitative measurement of the phenolic resins cure exotherm.
Elastic modulus of Mylar sheet
Authors: Becker Herbert
Published: April 2003

High precision stress–strain curves were determined from representative Type A Mylar sheets in several commercially available thicknesses. A representative value for Young's modulus was found to be 0.76 × 106 psi. Measured values were from 0.60 to nearly 0.78 × 106 psi with the maximum value occurring at 0.005‐in. thickness.
The photooxidation of polymers. II. Photolysis of polystyrene
Authors: Grassie N. , Weir N. A.
Published: April 2003

In the vacuum photolysis of polystyrene films at 28°C. under 2537 A. radiation the only gaseous product is hydrogen. At the same time the polymer becomes insoluble and discolors. The intensity exponent of the reaction is unity, the quantum yield of hydrogen is 4.3 × 10−2, the overall energy of activation is 2.9 kcal./mole, and the rate of photolysis is independent of molecular weight. No hydrogen is produced when 3650 A. radiation is used. These observations can be interpreted in terms of a simple reaction scheme in which the primary effect of the 2537 A. radiation is to liberate hydrogen atoms. The subsequent reaction of these and the polystyryl radicals simultaneously formed in a number of competing steps results in the appearance of hydrogen, the occurrence of crosslinking, and the production of carbon–carbon unsaturation in the main chain which ultimately leads to conjugation and color. These theories are supported by infrared and ultraviolet spectral measurements and by the observation that the rate of photolysis is accelerated by nitrogen.
Oxidative degradation of polybenzyl
Authors: Conley Robert T.
Published: April 2003

The primary steps involved in the degradation of polybenzyl at temperatures between 140 and 220°C. in the presence of air or pure oxygen has been found to be an attack at the methylene linkages to give benzhydrol and benzophenone linkages. Kinetic evaluation of the rate of benzophenone‐type carbonyl ingrowth indicated an apparent initial activation energy for the oxidation process of 14.5 ± 3.5 kcal. Vapor‐phase chromatographic analysis of the volatile products of the reaction indicate that the formation of benzoic acid and benzophenone are the major products of oxidation, along with smaller amounts of benzene, toluene, water, and carbon dioxide. It must be concluded that the initial oxidation of polybenzyl closely parallels the oxidation of phenolic resins and other closely related activated methylene polymers. Secondary degradation reactions which produce chain scission are generally equitable to further oxidation at both the benzhydrol and benzophenone linkages. The appearance and spectral substantiation of the formation of benzoic anhydride linkages from thermal dehydration of benzoic acid most adequately accounts for the formation of the secondary reaction products giving new but minor infrared bands in the early and intermediate stages of the degradation.
Role of ozone in dynamic cut growth of rubber
Authors: Lake G. J. , Lindley P. B.
Published: April 2003

The effect of ozone on the growth of cuts in rubber strips subjected to repeated tensile deformations has been investigated. At tearing energies below a critical value ozone accounts for all the cut growth, and in this region the rate of growth also occurs due to mechanico‐oxidative rupture, the rate of this type of growth increasing rapidly with increasing tearing energy so that the effects of ozone are normally slight. For vulcanizates of natural rubber and SBR unprotected by antiozonant, the characteristics of dynamic ozone cut growth can be deduced from static measurements. If a natural rubber test piece is not allowed to relax to zero strain on each cycle, the effects of ozone are important over a wider range of tearing energy.
DTA study of heterogeneous nucleation of crystallization in polypropylene
Authors: Beck H. N. , Ledbetter H. D.
Published: April 2003

The effect of cooling, nucleation, and spherulitic growth rates on the properties of polypropylene is discussed briefly. A differential thermal analysis technique is described for evaluating the relative extent of heterogeneous nucleation that occurs in a particular polypropylene composition. The method is based upon a nucleating agent's ability to reduce the relatively large amount of supercooling that occurs upon crystallization of polypropylene. Compounds are shown to vary widely in their effectiveness as heterogeneous nucleating agents in polypropylene. The relationships between the degree of supercooling of a particular polypropylene composition and its relative clarity, tensile properties, density, and morphology are shown.
Studies on the drawing of polyamide fibers. IV. Effect of drawing on the degree of longitudinal swelling
Authors: Takagi Yasuo , Hattori Hiroshi
Published: April 2003

The longitudinal dimensional change of dried nylon 6 monofilaments of various draw ratios swollen in the atmosphere of 24°C. and 100% R.H. was studied. The degree of longitudinal swelling in equilibrium changes with the conditions of drawing and the draw ratio of the sample; for the samples drawn immediately after spinning, it increases, passes through a maximum near a draw ratio of 2, and gradually decreases as the draw ratio increases; for the samples drawn many days after spinning the maximum point is at a draw ratio near 2.8, while for the samples drawn after heat‐treatment the degree of longitudinal swelling does not change appreciably with the draw ratio of the sample. The rate of longitudinal swelling remains nearly constant or increases slightly in the range of draw ratios of 1–3. It then decreases with the draw ratio at draw ratios higher than 3.
Recrystallization of amorphous cellulose
Authors: Wadehra I. L. , Manley R. St. John
Published: April 2003

Recrystallization of amorphous cellulose prepared by saponification of cellulose triacetate in an non‐aqueous medium was found to occur only at very high relative humidities, i.e., near 100%. At lower relative humidities the amount of recrystallization occurring was slight though significant. Correspondingly, the accessibility decreased from 90% (for amorphous cellulose) to a minimum of 79%, the same as that for cellulose II. The mechanism of recrystallization is discussed in terms of the surface tension, plasticizing action, and the hydrogen bonding ability of the solvent used for bringing about the recrystallization.
Characterization of block and random ethylene–propylene copolymers by differential thermal analysis
Authors: Barrall Edward M. , Porter Roger S. , Johnson Julian F.
Published: April 2003

A group of C14‐tagged ethylene and propylene polymers consisting of physical mixtures of homopolymers, block copolymers made up of two homopolymer sequences, and block copolymers made up of several homopolymer segments has been studied by differential thermal analysis (DTA). The effect of randomness in copolymers has also been studied in this set of systems, which contains 0–51 wt.‐% ethylene. Block copolymers and physical mixtures have been found to have thermograms with endothermal minima at approximately 138 and 163°C. The ratio of heights of the two minima has been found to be a function of the ethylene and propylene content for mixtures of homopolymers and for block copolymers without randomness. DTA thus provides an analysis for monomer ratios in physical mixtures and in block copolymers of ethylene and propylene. The cooling thermograms of block copolymers have been demonstrated to have two exotherms in all cases where the block ethylene content exceeded 10%; the propylene limit was not fixed. Mixed homopolymers do not exhibit two freezing exotherms. The total heat of fusion of the polymer has been found to be a usable measure of chain randomness and block nature. The conditions for observation of single and multiple transitions have been extended.
Glyceryl methacrylate hydrogels
Authors: Refojo Miguel F.
Published: April 2003

Hydrophilic three‐dimensional polymer networks (hydrogels) were prepared from glyceryl methacrylate (2,3‐dihydroxypropyl methacrylate). The solubility of poly(glyceryl methacrylate) in water permits the preparation of transparent hydrogels containing variable amounts of water at the equilibrium stage. This is accomplished by varying the degree of swelling at the time of network formation, and by varying the density of crosslinks. The temperature dependence of swelling of the hydrogels in water and in 0.9% sodium chloride solution, was determined. There exists a linear relationship between the refractive index and the per cent of water in the hydrogel. These hydrogels are potentially useful in ophthalmology.
Studies on the drawing of polyamide fibers. VI. Effect of drawing on the dye diffusion parallel to the fiber axis
Authors: Takagi Y.
Published: April 2003

The diffusion rate of an acidic dye (vylene Fast Blue 2P) into polycaproamide fibers along the direction parallel to the fiber axis (longitudinal diffusion rate) was obtained by measuring the dye penetration distance from a cross section of the sample fiber embedded in an acrylic resin. The following results were obtained. The longitudinal diffusion constant decreases monotonically with increasing draw ratio. The difference between the lateral dye diffusion constant and the longitudinal dye diffusion constant passes through a maximum near a draw ratio of 2. The activation energy for the longitudinal dye diffusion increases monotonically with draw ratio.
Effect of impurities on the polymerization of vinylcarbazole by azobisisobutyronitrile
Authors: Ellinger L. P.
Published: April 2003

Polymerization of vinylcarbazole by free‐radical initiators, especially azobisisobutyronitrile, yields polymer of higher molecular weight and better appearance than can be made by thermal polymerization. The polymerization is retarded and the molecular weight of the polymer lowered by amounts of anthracene comparable to or somewhat larger than the initiator concentration, but these effects soon show saturation at higher anthracene concentrations. Phenanthrene has a slight inhibiting effect which increases with concentration, the polymerization being almost completely inhibited at very high phenanthrene concentrations. The results are discussed in terms of the formation of an intermediate complex between the aromatic hydrocarbon and the growing polymer chain.
Correlation and prediction of polyamide glass transitions
Authors: Beaman Ralph G.
Published: April 2003

A simple scheme for the prediction of glass transition temperatures based on diamine and diacid component part contributions is applied to data for 19 interrelated polyamides. The new results, in conjunction with many prior determinations, lead to the assignment of 65 ± 20°C. for the glass transition of 6‐6 polyamide, contrary to published suggestions that the value might well be −65°C.
Dynamic mechanical behavior of poly(2‐hydroxyethyl methacrylate)–glass beads composites
Authors: Kolařík J. , Janáček J. , Nicolais L.
Published: April 2003

The dynamic relaxation behavior of a model two‐phase system, poly(2‐hydroxyethyl methacrylate)–glass beads, was studied by means of a freely oscillating torsional pendulum. The effect of the filler content on the storage and loss moduli of the composites could be described in terms of the modified Kerner equation in complex form. At temperatures below the glass transition temperature of the matrix, the agreement between experimental and theoretical data was satisfactory after correction for thermally induced stress due to different thermal expansion coefficients of matrix and filler. In the presence of filler, the capacity of the matrix to store and dissipate energy increases, but the character of molecular motions underlying the dispersions observed is preserved because the temperature of the dispersions remains unchanged. The effect of water on the dynamic relaxation behavior of composites is primarily reflected in changes in the shape of the temperature dependence of the dissipating capacity of the matrix. The data allow the conclusion to be drawn that the chain mobility at the interphase boundary does not decrease and that no additional frictional mechanisms appear.
Transitions and relaxations of linear polyesters related to poly(ethylene terephthalate). II. Glassy and gamma
Authors: Yip Harry K. , Williams H. Leverne
Published: April 2003

The β‐relaxation at Tg of the terephthalate and isophthalate series is due to molecular motions of the backbone chains in the amorphous region, but differs for the isophthalate series in that the p‐phenylene group does not exhibit the free rotation possible for the m‐phenylene group. Consequently, the relaxation times of the terephthalate series are longer than for the isophthalate series. The γ‐relaxation (Tγ) for the higher homologues of the terephthalate series cannot be explained in terms of the poly(ethylene terephthalate) analogy. For poly(ethylene terephthalate) and poly(tetramethylene terephthalate), an induced cooperative type of motion of all the moieties is possible, whereby overlapping processes caused by “rocking vibrations” are observed as one γ‐peak. The resolution of the γ‐loss peaks for the above‐mentioned polyesters into components is not possible at the experimental frequency of 110 Hz. For poly(hexamethylene terephthalate) and poly(decamethylene terephthalate), the “rocking vibrations” between the moieties of the skeletal chain are reduced so that even at a test frequency of 110 Hz, the γ‐loss peaks could be resolved into two or three components. In the case of poly(decamethylene terephthalate), three components are resolved; the lowest temperature peak γ1 is attributed to hindered motions of the methylene portions, the γ2 peak is attributed to motions of the carbonyl group in the gauche conformation, and the γ3 peak is attributed to the carbonyl group in the trans conformation of the skeletal chain in the amorphous region. The general observations obtained by other techniques were confirmed by the forced vibration analyses. As the length of the methylene chain increased, Tg decreased. As crystallinity increased, the β‐relaxation moved to higher temperatures and the damping peak was smaller and broader. The damping peak moved to lower temperatures and increased in size as the length of the methylene chain increased. The damping peak was larger for the isophthalate homologue than for the corresponding terephthalate polyester.
Polymer composites containing plasma‐treated mica. II. Dielectric properties
Authors: Wertheimer M. R. , Paquin L. , Schreiber H. P.
Published: April 2003

The complex relative premittivity K*(ω) of polymer–mica composites has been studied in the frequency range extending from about 10−2 to 107 Hz. Microwave plasma treatment in ethylene of the mica flakes leads to significant alterations of K*(ω) for the matrix polymers used—polyethylene, polystyrene, and a mixture of these two polymers. The origins of the dispersion characteristics were investigated using a series of polyethylene samples containing up to 50 wt‐% of untreated mica. Comparing experimental results with theoretical analyses of the Maxwell‐Wagner‐Debye‐like interfacial polarization effect, it is possible to identify two major contributions to K*(ω): a Debye‐like dispersion centered near 102 Hz and a charge‐diffusion mechanism which contributes primarily at low frequencies (≲10 Hz).
Water‐soluble polymers as retention aids in a model papermaking system. I. Polyacrylamides
Authors: Howard G. J. , Hudson F. Lyth , West Jeremy
Published: April 2003

A series of polyacrylamides covering a wide molecular weight range were synthesized and employed as retention aids in a model papermaking system of cellulose fibers and titanium dioxide. The ability of the polymer to increase the proportion of added titanium dioxide that is retained in the formed paper sheet is strongly dependent on molecular weight, but not on pH. Adsorption isotherms on both pigment and fibers are strongly molecular weight dependent. Polyacrylamides have no more than a weak flocculating effect on fiber suspensions and stabilize dispersions of titanium dioxide. However, with mixed dispersions of fibers and pigment, in the same ratio (10:1) as in paper formation, strong coflocculation is evidenced by the higher molecular weight polyacrylamides. In this model system pigment retention is a consequence of a heteroflocculation by adsorbed polymer bridging between the particles of titanium dioxide and cellulose fibers, possibly augmented by improved filtration in the forming sheet. Electrostatic effects appear to be unimportant in the system under study.
Polysulfone hollow fibers. II. Morphology
Authors: Cabasso Israel , Klein Elias , Smith James K.
Published: April 2003

The morphology of porous polysulfone hollow fibers which were spun by the dry–wet spinning process is discussed. It was demonstrated that a relatively moderate quenching medium should be employed in the bore of the nascent fiber in order to produce an isotropic fiber free of macrovoids and intrusion cells. A rather delicate quantitative balance between the internal precipitant and the spinning solution has to be maintained, especially when low‐viscosity polymeric solutions are employed. Scanning electron micrographs of fiber cross sections display highly porous, spongestructured walls which in some instances exhibit a rather dense interface skin. However, control of the extrusion/coagulation procedure allows the formation of skinned, porous skinned, and nonskinned fibers.
Acoustic relaxation and infrared spectroscopic measurements of the plasticization of poly(methyl methacrylate) by water
Authors: Gilbert A. S. , Pethrick R. A. , Phillips D. W.
Published: April 2003

Measurements are reported on the acoustic attenuation and velocity of dry and wet samples of poly(methyl methacrylate) over a temperature range of 5° to 70°C and over a frequency range of 5 to 35 MHz. Lowering of the glass transition temperature with increase in water content was reflected in an increase in the acoustic attenuation and a lowering of the velocity at high temperature. Comparison of the infrared spectra of wet and dry thin films indicates that water exhibits spectroscopic characteristics of isolated rather than highly clustered molecules. A study of the temperature dependence of the diffusion coefficient of water into the polymer matrix provided an activation energy for the migration process. The data suggest that water plasticizes poly(methyl methacrylate) via specific local interactions with the backbone.
The determination of moisture transitions in cellulosic materials using differential scanning calorimetry
Authors: Nelson Robert A.
Published: April 2003

The association of water with cellulose is of significant technological importance. It forms the basis for the manufacturability of paper and ultimately controls, either directly or indirectly, mechanical, electrical, thermal, and optical properties. Differential scanning calorimetry has been used to characterize moisture transitions in these materials. Total bound water contents have been determined. Specific transitions for the model system, cotton linters, have been identified including free water incorporation point (0.05 g/g), total bound water (0.18 g/g), and fiber saturation point (0.05 g/g). Results are compared to those found in a pulsed nuclear magnetic resonance study in which a moisture distribution model was generated; free water point (0.046 g/g) and total bound water (0.19 g/g). The differential scanning calorimetry technique can provide a more readily available, less expensive, and simpler technique for paper/cellulose characterization and study.
Studies in the molecular weight distribution of epoxide resins. IV. Molecular weight distributions of epoxide resins made from bisphenol a and epichlorohydrin
Authors: Batzer H. , Zahir S. A.
Published: April 2003

The molecular weight distribution of epoxide resins made from bisphenol A and epichlorohydrin at high ratios of epichlorohydrin to bisphenol A are compared with the theoretically predicted distributions for two theoretical models: the “taffy” process A, the direct reaction of epichlorohydrin with bisphenol A; and the “taffy” process B, the self‐polymerization of a monoglycidyl ether of bisphenol A followed by postglycidylation. At high ratios of epichlorohydrin to bisphenol A, process B is shown to give more low molecular weight products than process A. Deviations of the experimentally measured distributions from the theoretically predicted distributions for high epichlorohydrin/bisphenol ratios are attributed to the higher reactivity of epichlorohydrin to the phenolic compared with the aryl glycidyl ether functional group. Preliminary kinetic data are presented using a modified gel chromatographic method which enables the separation of most of the intermediates formed in this reaction.
Porosity and pore size determination in polysulfone hollow fibers
Authors: Cabasso I. , Robert K. Q. , Klein E. , Smith J. K.
Published: April 2003

Average pore sizes and effective porosity of microporous polysulfone hollow fibers were determined by the gas permeability method. Surface structure and porosity were determined by scanning electron microscopy. The values of effective porosity ε/q2 (porosity/tortuosity factor) are approximately one order of magnitude lower than those reported previously for flat sheet porous membrane. These lower values are a direct outcome of a higher polymer concentration in the spinning dope. Correlations between the wall void volume, equivalent pore size, and hydraulic permeabilities of the hollow fibers have been determined. Rather low values of ε/q2 have been calculated compared to those of the void volume; these effective porosity values indicate either a very high tortuosity factor or a large number of “dead end” pores. Exposure of the fibers to elevated temperature (110°C) for a short period of time drastically reduces the surface pore size and narrows the pore size distributions, whereas overall fiber dimensions are reduced only by 1%, and 85% of the fiber's hydraulic permeability is retained. The scanning electron microscopy study reveals the formation of a relatively dense skin in some spun fibers. For such “skinned” fibers, kinetic (permeability) evaluation of static structure such as mean pore size is not realistic and is further generalized to the term “equivalent pore size.”