bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric behavior of some polar high polymers at ultra‐high frequencies (microwaves)
Authors: Frosini Vittorio , Butta Enzo , Calamia Mario
Published: April 2003

The dielectric behavior of different polar high polymers at ultra‐high frequencies has been investigated by means of a dielectrometer, suitably modified to permit measurements at different temperatures. Experimental measurements were made at about 9 × 109 cps over the temperature range of −150 to 200°C. for polyoxymethylene, polythiomethylene, poly(3,3′‐chloromethyl)oxetane (Penton), polycarbonate of 4,4′‐dioxydiphenyl‐2,2′‐propane (Makrolon), poly(vinyl alcohol), poly(vinyl acetate), poly(vinyl chloride), vinyl chloride–vinyl acetate copolymer, and two ABS plastics, type B (blend) and type G (graft). On comparing the dielectric behavior of the examined materials at ultra‐high frequencies with the corresponding ones determined at low or at radiofrequencies, it is observed that, in the microwave region, all relaxation peaks, either connected with cooperative motions in main chain (primary processes) or with local motions in the backbone or in side chains (secondary processes), usually observed at lower frequencies, tend to disappear; the corresponding relaxation effects, however, manifest themselves through a progressive increase of losses with increasing temperature, which is particularly marked above the glass transition temperature Tg. The latter transition, in spite of the very high frequency, is easily distinguished, in most cases, by the sudden change of slope in the tan δ versus temperature curve which accompanies its onset. This is explained on the basis of the very wide distribution times of molecular relaxation processes in polymers and the increase in strength of the secondary relaxation effects, which is verified at Tg, as a consequence of the increased kinetic energy of macromolecules and of the larger free volume for orientation of side chains. Each case is discussed separately and the experimental results interpreted on the basis of the molecular structure and chain mobility of the examined polymers.
Kinetic study on the alkaline degradation of cotton hydrocellulose
Authors: Haas Donald W. , Hrutfiord Bjorn F. , Sarkanen K. V.
Published: April 2003

The kinetics of alkaline degradation of cotton hydrocellulose were determined in 5% NaOH at various temperatures. An activation energy of 24 kcal./mole was found for the endwise degradation reaction, while that of termination to a stable m‐saccharinic acid endunit is 32 kcal./mole. Consequently, the DPn of the degradable chain length is highly dependent on the reaction temperature, being 1000 at 65°C. and 140 at 132°C. At lower temperatures, the majority of degrading chains terminate to a normal reducing endgroup at the crystalline–amorphous transition region. From the data, the DPn of cellulose chain segments participating in the amorphous regions of the original cotton fibril was calculated to be 143. This result strongly supports the classical micellar fibril structure over the folded model proposed by Manley.
Preparation and fabrication of aromatic polyimides
Authors: Dine‐Hart R. A. , Wright W. W.
Published: April 2003

Aromatic polyimides were prepared from pyromellitic dianhydride and a number of aromatic diamines. The effect of certain variables on the polymerization to, and the degradation of, the intermediate polypyromellitamic acids was studied, and a previously unrecorded reaction intermediate was isolated and identified. From these studies the conditions necessary to obtain high molecular weights were defined. Techniques were developed for the fabrication of satisfactory films and moldings.
Function of sheets of cellulose chains in swelling reactions on cellulose
Authors: Warwicker J. O. , Wright Ann C.
Published: April 2003

An x‐ray investigation of the products formed by the action of caustic soda on different samples of cellulose and those formed on the decomposition of these products by aqueous reagents and alchols shows that the fundamental reacting unit is a sheet of cellulose chains, and not individual cellulose chains. Although the caustic soda can affect the relative dispositions of the chains within these sheets to some extent, it cannot separate the chains, and the products then depend on the aggregation of the cellulose sheets with or without other molecules between them. Such aggregation leads to variables products whose x‐ray diagrams can, however, show distinct reflections and be mistaken for those from more precise crystal structures. It is, therefore, important in swelling reactions to take into account the ability of the swelling agent to modify the cellulose sheets and the mode of decomposition of the complexes formed on swelling. Thus swelling with caustic soda cannot be taken as typical of all aqueous swelling reagents in its reaction towards cellulose, and the possibility with other reagents of finding cellulose I, instead of cellulose II, after a series of swelling reactions must be taken into consideration.
Heterogeneous nucleating agents for polypropylene crystallization
Authors: Beck H. N.
Published: April 2003

A model nucleating agent for polypropylene crystallization is described. A series of compounds consisting mainly of organocarboxylic acid salts is evaluated as heterogeneous nucleating agent for polypropylene crystallization by measuring their effect upon the polymer supercooling. Sodium benzoate and basic aluminium dibenzoate were among the best nucleating agents found. The nucleating abilities of the various compounds are discussed in terms of their structural features.
Oscillating flow behavior of high‐density polyethylene melts
Authors: Myerholtz R. W.
Published: April 2003

The oscillating flow behavior of a variety of high‐density polyethylene and copolymer samples was studied in a constant displacement rate rheometer. At any plunger velocity, the period of the oscillations decreases linearly with melt depth, suggesting a resonance phenomenon. As plunger velocity is increased, the load waveform changes in a regular manner that indicates a progressive increases in the proportion of each cycle spent on the right‐hand branch of the flow curve. Little difference was found in the shear stress at which oscillating flow began for samples differing in molecular weight, molecular weight distribution, and manufacturing process. However, the shear rate at which oscillating flow begins depends, strongly on both molecular weight and distribution. Oscillating flow is shifted to higher shear rates by broadening distribution, reducing molecular weight, increasing temperature, or decreasing the L/D ratio of the capillary.
Estimation of kinetic parameters during Teflon degradation from linearized differential TGA traces
Authors: Reich Leo
Published: April 2003

In a recent communication,1 mathematical expressions were derived for obtaining kinetic parameters during polymer pyrolyses from linearized DTA traces. The approximate method developed is now extended to differential TGA traces in this paper and is applied to polytetrafluorethylene (Teflon). The results obtained are compared with those obtained from more elaborate procedures.
Molecular weight changes in irradiated polypropylene
Authors: Marans N. S. , Zapas L. J.
Published: April 2003

We have shown by two separate measurements that polypropylene when melted after irradiation undergoes crosslinking from the inception of irradiation. The first proof was an immediate increase in the solution viscosity of a narrow molecular weight fraction of polypropylene. The second proof was the marked change in melt‐flow properties on irradiation of a broad molecular weight distribution polypropylene. These findings tend to support one of the two currently held views on the action of radiation on polypropylene. In addition we have confirmed previous reports that melting after irradiation contributes to the overall crosslinking reaction.
Elastic behavior of concentrated solutions of acrylonitrile copolymers
Authors: Hayahara Takuro , Takao Seiji
Published: April 2003

The elastic behavior of concentrated solution of acrylonitrile copolymer was investigated by the capillary end correction method. The results were as follows. (1) The shear stress is proportional to recoverable shear strain in accordance with Hooke's law below critical concentration; above a critical concentration, however, the shear modulus depends on shear stress. (2) The log–log plots of zero shear modulus against polymer concentration and molecular weight fall on two straight lines with different slopes. The intersection of lines is considered to be the onset of elastically deformable entanglement network. We denote this inflection point as (Cc)e or (Mc)e. (3) The log–log plot of viscosity against polymer concentration does not show a change of slope at the critical concentration (Cc)e. (4) By the application of the kinetic theory of rubberlike elasticity to the pseudo‐network structure of concentrated polymer solution, in the range of Cc < C < (Cc)e or Mc < M < (Mc)e, the number of chain entanglement per molecule is kept one; moreover, in the range of C > (Cc)e, or M > (Mc)e, the number of chain entanglement increases to three.
Derivation and correction of polyethylene melt strength equation
Authors: Combs R. L. , Slonaker D. F. , Coover H. W.
Published: April 2003

The following equation for the determination of polyethylene melt strength (MS) has been derived:

where Δl is the length (inches) of extruded polymer cord required for 50% decrease in diameter of the cord, r0 is the radius (inches) of the molten polymer cord as it first emerges from the melt indexer die, and MF is melt flow rate in grams/10 min. The required measurements are made on the initially extruded 0.5‐in. portion of the polymer cord from a conventional melt indexer using the standard 0.0825‐in.‐diameter die and 2160‐g. load and a temperature of 230°C. This melt strength equation was derived by using the assumption that the melt strength can be expressed as melt viscosity at low shear rates. Melt strengths of polyethylenes having similar melt indices have been shown to have over a 37‐fold difference.
Ionic graft copolymerization. I. Homopolymerization of β‐propiolactone by sodium acetate catalyst
Authors: Shiota Tetsuya , Goto Yutaka , Hayashi Koichiro
Published: April 2003

The polymerization of β‐propiolactone (βPL) by sodium acetate catalyst has been investigated. The polymerization behavior with monomer purified with calcium chloride was found to be a little different from that previously reported for this monomer. That is, poly‐β‐propiolactone (PβPL) obtained from βPL dried with CaCl2 has a higher degree of polymerization than that obtained from conventionally treated βPL, and its infrared spectrum shows type II configuration, which differs from that reported in previous papers. Some chain transfer reaction is observed even for the polymerization of the CaCl2–dried βPL; however, this is less important in toluene. The electronegativity of the anion or cation in catalyst greatly influences the rate of polymerization.
Ionic graft copolymerization. III. Graft copolymerization of β‐propiolactone onto polyacrylonitrile containing diketene units
Authors: Shiota Tetsuya , Goto Yutaka , Hayashi Koichiro , Okamura Seizo
Published: April 2003

Polyacrylonitrile (PAN)–β‐propiolactone (βPL) graft copolymer was synthesized by means of the ionic polymerization of βPL in the presence of polyacrylonitrile containing diketene units by using basic catalysts. A graft copolymer was produced by the copolymerization of βPL with the lactone ring in the trunk polymer. In this graft copolymerization method, the grafting efficiency was low. However, grafting efficiency increased with the mole ratio of polymeric lactone to βPL; also higher molecular weight of PβPL favored higher grafting efficiency. The reactivity ratio of polymeric lactone to βPL was estimated to be in the range of 0.1–0.3.
Certain fine structure and thermal properties of benzhydrylated cotton cellulose
Authors: Stanonis D. J. , King Walter D. , Harbrink Pieter , Conrad Carl M.
Published: April 2003

The present paper describes the results of a preliminary study of certain physical and thermal properties of benzhydrylated cotton yarns. The 200‐yd. lengths of 7/2 yarn consisting of purified mercerized cellulose were reacted in a special reactor to various degrees of substitution from DS 0.31 to DS 1.22 with benzhydryl bromide in a mixture of equal volumes of 2,6‐lutidine and dimethylformamide. The products were examined for tensile strength at break, which decreased only slightly with substitution; ultimate elongation, which was relatively uniform at 60–70% of the control yarn; and tenacity, which decreased with substitution largely due to added weight. The energy of rupture remained relatively constant at about 50% above the control. Tensile stiffness decreased progressively with substitution to about 25% of the control. Density decreased 10–11% with substitution. Crystallinity of the cellulose largely disappeared with substitutions above DS 1, and the lattice of benzhydryl cellulose began to appear. Stiffness, elastic recovery and work recovery were measured on 5‐in. specimens of the yarn in an oven while they were subjected to repeated extension to about 1–2% and relaxed as the temperature was raised twice to 200°C. and lowered. During the heating phase of the first cycle the yarn underwent considerable heat adaptation. However, during the cooling phase and during both heating and cooling phases of the second cycle, the yarns showed generally favorable behavior. Attempts are made to interpret the results in terms of molecular modifications.
Membrane potentials of thin nitrocellulose membranes
Authors: Carnell Paul H. , McGunegle Daniel E.
Published: April 2003

The membrane potentials of thin (300–1300 A.) nitrocellulose (Parlodion) membranes have been investigated. Measurements were made in a Lucite cell by use of calomel electrodes with 0.05N KCl and 0.1N KCl. Variables having an influence on membrane structure, such as solvent polarity, temperature, and thickness, have been studied in relation to membrane potential. The range of potentials observed for Parlodion (2.1–9.2 mv.) is believed to be the result of differences in the orientation of the nitrocellulose molecules (and their accompanying electrochemically active carboxyl groups) in the membrane structure.
Radiation‐induced reactions with cellulose. II. The Trommsdorff effect: Dose and dose rate studies involving copolymerization with monomers in methanol
Authors: Dilli S. , Garnett J. L.
Published: April 2003

The radiation‐induced grafting to cellulose of styrene, methyl methacrylate, vinyl acetate, 2‐vinylpyridine, and 4‐vinylpyridine in methanol has been studied. All monomers exhibit appreciable grafting at room temperature in either vacuum or air for total doses up to 10 Mrad and at dose rates as high as 1.4 Mrad/hr. in a spent fuel or 60Co facility. The magnitude of the grafting depends upon both the total dose and dose rate. Under certain experimental conditions, the grafting experiences a maximum which has been attributed to the Trommsdorff effect. A novel mechanism involving charge‐transfer bond formation is proposed to account for the observed data in the grafting reactions.
Radiation‐induced reactions with cellulose. III. Kinetics of styrene copolymerization in methanol
Authors: Dilli S. , Garnett J. L.
Published: April 2003

The kinetics of the radiation‐induced grafting of styrene to cellulose in methanol have been studied in air at dose rates of 0.007, 0.014, and 0.078 Mrad/hr. in 60Co and spent fuel element facilities. The variables affecting rate of grafting include monomer concentration, radiation dose rate, and total dose. Grafting reaches a maximum at 60–70% by volume methanol in styrene. The results have been interpreted in terms of possible grafting mechanisms, including charge‐transfer intermediates; however, a complete mathematical treatment of the data is not possible at present because of the absence of appropriate swelling data for cellulose in mixtures of styrene and methanol. Poor grafting observed in solutions of up to 10% monomer is attributed to radical scavenging (predominantly from the solvent) by the monomer leading to the formation of scavenged products including homopolymer. Rate of grafting falls off for solutions above 80–90% monomer concentration and radical scavenging by monomer radicals is again postulated to account for the observed behavior.
Étude de l'étirage à froid des fibres de polymères synthétiques dans les agents organiques
Authors: Grellier M. R.
Published: April 2003

The cold drawing of synthetic polymers is generally carried out through necking at a short collar between the drawn part and the undrawn part of the fiber; if the drawing is carried out in certain organic liquids, the lengthening is realized through thousands of simultaneous necks which permit the fiber to be penetrated by a dye dissolved in the liquid. The stress–strain curves for the drawing in liquid show an important decrease in the force at the time the multiple necking are produced. This decrease is the result of an increase in the mobility of the macromolecular chains through the penetration of the organic liquid to the level of the shoulder of the necks. A morphological study has been carried out through the observation of cuts by optical microscopy, along with a utilization of the techniques of x‐ray diffraction, IR spectroscopy, and electron microscopy. It was found that the liquid penetrates t̀he fiber to the level of the necking via a rupture of the interchain bonds which takes place during the change of structural following the drawing. The bonds are maintained ruptured as long as the liquid is not squeezed out by the aligning of the chains; they reform later to produce a new highly crystalline structure.
Simple microtome for sectioning cellular foam
Authors: Hannah R. E. , Bond R. H.
Published: April 2003

A simple, inexpensive microtome was developed for sectioning polystyrene foam prepuff. The cell structure is well defined and wall thicknesses can be measured easily from photomicrographs prepared with the microtome.
Delayed yielding of epoxy resin under tension, compression, and flexure. I. Behavior under constant strain rate
Authors: Ishai Ori
Published: April 2003

Series of loading tests were carried out on epoxy resin specimens, at varying constant strain rates, under tension, compression, and flexure. The stress–strain relationship revealed a distinct yielding stage followed shortly by a post‐yielding region of decreasing load. In all cases, results indicate linearity between yield stress and log strain rate, in accordance with Eyring's theory of viscous flow. For specimens unloaded close to the yield point, photoelastic observations revealed a residual pattern parallel to the theoretical principal shear stresses. These results, supported by additional data from other works, indicate a viscoplastic deviatoric stress‐biased diffusional mechanism as the dominant factor in the yielding of an amorphous crosslinked epoxy system.
Mode of failure in structural adhesive bonds
Authors: Delollis N. J. , Montoya O.
Published: April 2003

This paper attempts to prove the possibility of adhesive failure by preferential adsorption and adhesive displacement at the adherend surface. Data are presented to demonstrate different modes of failure that are possible after initial cohesive failure.
A generalized equation of state for polymers
Authors: Whitaker Herbert L. , Griskey Richard G.
Published: April 2003

A simple, generalized equation of state has been developed that describes the pressure–volume–temperature behavior of both addition and condensation polymers. Use of the equation requires only that the polymer's glass temperature and density at 25°C. and one atmosphere be known. The equation applies to both amorphous and crystalline polymers for pressures up to 10,000 atm. It also appears to hold for copolymers. Polymer glass temperatures can also be estimated with the equation.
Fiber structures: A fresh look from metallography
Authors: Viswanathan A.
Published: April 2003

The parallel between fibers and metals is discussed in terms of their behavior upon heat treatment, crystallite size and orientation, and diffusion of atoms and molecules. It is pointed out that the degree of crystallinity employed to interpret the x‐ray diffraction patterns of fibers is not an important physical parameter. The need for critical study of the mechanism of the growth of primary and secondary walls is stressed for a better understanding of the physical properties of fibers. Reference is made to Hosemann's theory of paracrystals which will help to resolve the “open” problems in polymer physics.
A generalized flow theory
Authors: Lenk R. S.
Published: April 2003

A generalized flow theory is put forward which is derived from a review of accepted types of stress–response curves. The theory is summarized in a single flow curve of universal shape from which all types of liquid flow can be interpreted. This “generalized flow curve” can be applied to polymer melts in particular, but there is no reason why it should not equally apply to solutions, dispersions, suspensions, emulsions, or pure liquids. The generalized flow curve is exactly analogous to the typical fully developed load–deformation curve which applies to tough plastics in the solid state. A molecular interpretation of the processes involved in producing the flow phenomena implicit in the various portions of the generalized flow curve is put forward. The evidence on which the theory is based is reviewed. Some fundamental implications are discussed.
Effect of carbon black on time dependence of the melt flow index
Authors: Schreiber H. P. , Rudin A.
Published: April 2003

Time dependence in the melt indexing of polyolefins stabilized against thermally induced changes is well known, the prevalent effect being an increase in melt index toward a steady‐state value. The melt index of polyethylenes compounded with carbon black has been found to decrease, in some cases radically, although oxygen uptake data show no evidence of thermal instability. The melt index–time plot can be restored to its normal shape by adding excess quantities of a standard thioether antioxidant. Data are rationalized by assuming that polyethylene adsorbs on the available pigment surface, forming a crosslink network. The thioether antioxidant, however, may adsorb preferentially, thereby restoring the normal response of the polymer to forces resulting in its capillary extrusion. The results emphasize the contribution of chain orientation effects to the time dependence of melt index.
Infrared study of the cure of unsaturated polyester
Authors: Imai T.
Published: April 2003

The infrared spectra of unsaturated polyesters in process of cure have been taken of samples free from unreacted protion. Styrene and polyester fractions in the curing polyester films were assessed from comparison of the band intensities at 695 and 740 cm.−1. The styrene fraction in curing films was found to increase as cure proceeded, and the delayed curing was seen to be accompanied by a build‐up of films of lower styrene content. The differences between samples observed in the mechanical behavior were considered attributable for the most part to the difference in styrene content.
Radiation‐induced changes in the index of refraction, density, and dielectric constant of poly(methyl methacrylate)
Authors: Gardner Donald G. , Toosi Mohammad T. A.
Published: April 2003

Samples of commercially prepared poly(methyl methacrylate) (Lucite) were irradiated with 13‐M.e.v. electrons in the dose range 0–11 Mrad, and the induced changes in the index of refraction, density, and dielectric constant were observed. An attempt is made to interrelate the observed changes theoretically.
Experimental determination of ultrasonic wave velocities in plastics as functions of temperature. IV. Shear velocities in common plastics
Authors: Asay James R. , Guenther Arthur H.
Published: April 2003

The temperature dependence of acoustic shear velocities are reported for Poly‐Penco nylon, type G Plexiglass [poly(methyl methacrylate)], TFE Teflon (tetrafluoroethylene), low‐ and high‐density polyethylene, Lexan (polycarbonate), and Delrin Acetal (nylon). Most of the data were obtained at a frequency of 1 Mc./sec. over the temperature range of 25–100°C. In addition, previously unreported longitudinal velocities to ∼125°C. are reported for Lexan and Delrin Acetal.
Radiation‐induced solid‐state polymerization in binary systems. V. Polymerization in binary systems containing long chain compounds
Authors: Kaetsu Isao , Hayashi Koichiro , Okamura Seizo
Published: April 2003

Radiation‐induced solid‐state polymerization in binary systems containing long‐chain compounds has been investigated. Butyl stearate–methyl methacrylate and stearyl alcohol–methyl methacrylate systems have been studied in detail. In these systems insource polymerization does not occur but a remarkable post‐polymerization takes place on warming after irradiation at low temperature. The limiting conversion characteristics of this post‐polymerization depend greatly on the nature and the concentration of the long‐chain compounds. The post‐polymerization is observed to be more marked in the butyl stearate–methyl methacrylate system than in the stearyl alcohol–methyl methacrylate system, and it increases with increasing concentration of the long‐chain component. An optimum warming rate and warming temperature exists for the maximum saturated conversion. Irradiation in air causes some decrease of conversion compared to irradiation in vacuo. The possible mechanism is that monomer diffuses into the crystals of the long‐chain compound after melting at the eutectic temperature. The polymerization may be initiated by trapped radicals of the long‐chain compound and carried out in the crystal of the long‐chain compound with a smaller possibility of termination. In binary systems containing long‐chain compounds, lowering of the melting point is slight, and the eutectic composition exists at the richer composition of monomer, so almost all the long‐chain substance remains as excess crystals, which are suitable for holding trapped radicals. The crystal lattices of long‐chain compounds may be softer than those of compounds of small molecular size. This fact is favorable for monomer diffusion. This explains why such a post‐polymerization takes place only in systems containing long‐chain molecules.
Radiation‐induced solid‐state polymerization of vinyl compounds in binary systems
Authors: Nishii Masanobu , Tsukamoto Hiroshi , Hayashi Koichiro , Okamura Seizo
Published: April 2003

The radiation‐induced solid‐state polymerization in the binary systems such as acryl‐amide–methacrylamide and acrylamide–acenaphthylene was studied. The former system forms a solid solution, and the latter one forms a eutectic mixture. In the solid solution, the polymerization proceeds homogeneously and copolymer is formed, while in the eutectic mixture, it proceeds heterogeneously, forming only homopolymer. The post‐polymerization of the same binary systems was also studied. Linearity between the conversion and the logarithm of the post‐polymerization time was found for the various monomer compositions at various temperatures. This relationship satisfied the kinetic equation presented by Morawetz et al. for the post‐polymerization of acrylamide. The kinetics of the binary systems might be considered similarly to the single system, considering that the crystalline state of the system is changed by the monomer compositions.
Effect of aromatic groups on localization of high energy in cellulose
Authors: Arthur Jett C. , Stanonis David J. , Mares Trinidad , Hinojosa Oscar
Published: April 2003

When γ‐radiation from 60Co interacted with fibrous cotton cellulose, the localization of at least part of the high energy resulted in cellulosic chain cleavage and loss in breaking strength of the irradiated fibers. The substitution of aromatic groups on the cotton cellulose molecule affected this localization of energy and decreased the radiation degradation of the fiber. The nature of the linkage of the aromatic group to the cellulose molecule was not as important as the radiation stability of the linkage. For example, if localization of energy occurred which cleaved the aromatic group from the cellulose molecule, the radioprotection of the cellulosic molecular chain by the aromatic group was not effective. If the aromatic group was so modified that the effective number of π‐electrons was decreased, the radioprotection of the cellulosic chain was also decreased. The radioprotection of the cellulosic molecular chain by benzhydryl, trityl, benzoyl, and cinnamoyl groups was effective over distances equivalent to several cellobiose units. The radioprotection of the cellulosic chain by naphthoyl groups was significant but not as effective as the listed groups. Due to the sharing of π‐electrons in the naphthoyl group, the effective number of π‐electrons was reduced, and consequently the radioprotective effect of the group was also reduced. Benzyl groups were cleaved from the cellulose molecule on irradiation and offered no radioprotection to the cellulosic chain, at least at the high radiation dosages used. The ESR spectra of the irradiated celluloses, both substituted and unsubstituted, were similar. This indicated that the presence of aromatic groups did not change the nature of the long‐lived free radicals induced in cellulose on irradiation. It was suggested that selective energy absorption by the aromatic group from the spur of high‐energy electrons produced on interaction of γ‐radiation with the cellulose molecule could account for the radioprotection of the cellulosic molecular chain.
ESR study of post‐irradiation reactions of cellulose and acrylonitrile
Authors: Baugh Peter J. , Hinojosa Oscar , Arthur Jett C.
Published: April 2003

An ESR study of the free‐radical mechanisms of the post‐irradiation reactions of cotton cellulose with acrylonitrile is reported. The effects of atmosphere, moisture content, and solutions of acrylonitrile on the yield and stability of free‐radical sites in irradiated cellulose were determined. On interaction of γ‐radiation from a 60Co source with cotton cellulose, long‐lived free‐radical sites were found within the molecular lattice. Short‐lived free‐radical sites were apparently also formed on chain cleavage, gave strong singlet spectra, and were readily accessible to interaction with water. Other free‐radical sites were formed within regions of the cellulosic fiber which were inaccessible to moisture or aqueous solutions even after contact times as long as three days. It was suggested that long‐lived free‐radical sites in cellulose I (containing regain moisture) resulted from dehydrogenation at C5, and in cellulose II (containing regain moisture) resulted from dehydrogenation at C5 and dehydrogenation of the OH group or dehydroxylation at C6. When irradiated cellulose was contacted with a solution of acrylonitrile (15%) in 75% aqueous zinc chloride, the initial rate of decrease in spin concentration was higher than the rate of decrease as the time of contact increased. The ESR spectrum of the reacted cellulose, observed at −100°C., as compared with the spectrum for the irradiated cellulose, had decreased in signal strength with increase in time of contact and changed from a three‐line spectrum to an ill‐defined spectrum. The free radical being observed was probably due to unreacted sites in the cellulose. The extent of the graft copolymerization reaction was directly related to the initial spin concentration in the irradiated cellulose.
Diethylaminoethyl cellulose–epoxide reactions
Authors: Soignet Donald M. , Benerito Ruth R. , McKelvey John B.
Published: April 2003

Reactions of various monoepoxides and diepoxides with diethylaminoethyl (DEAE) cellulose in the absence and presence of external catalysts have been studied. In the absence of additional catalysts, many epoxides which did not react with the unmodified cotton reacted with DEAE‐cotton. Others, which reacted with unmodified cotton in the presence of external bases, imparted different properties when catalyzed by the builtin tertiary amino groups of DEAE‐cotton. For example, epichlorohydrin reacted with DEAE‐cotton to produce a fabric with excellent conditioned recovery, good wet recovery, and strong‐base anion exchange properties. The same epoxide imparted only wet crease recovery to cotton when the reaction was catalyzed by external bases. Phenyl glycidyl ether and styrene oxide reacted with DEAE‐cotton to produce a fabric with twentyfold improvement in resistance to flex abrasion. With 8% aqueous NaOH as an external catalyst, the DEAE‐cotton displayed greater reactivity with all epoxides than did the unmodified fabric. DEAE‐cotton–diepoxide reactions with added base catalyst generally resulted in a decrease in the conditioned recovery angle and an increase in the wet recovery angle. When Zn(BF4)2 was used as an additional catalyst, again the DEAE fabrics displayed the greater reactivity toward the monoepoxides; but the unmodified cotton was more reactive toward the diepoxides than was the DEAE‐cotton. The Zn (BF4)2–monoepoxide‐treated DEAE fabrics had higher wet recovery angles but lower dry recovery angles than the corresponding epoxide‐finished control cottons. Butadiene diepoxide was the only diepoxide investigated which imparted higher dry recovery angles to the DEAE‐cotton than to the unmodified cotton control in the presence of Zn(BF4)2. Tertiary amino groups in DEAE‐cottons act as an internal catalyst for the opening of the oxirane rings, direct the site for reaction in the absence of additional catalysts, and react with some epoxides to form quaternary nitrogen groups.
DTA evidence for physical orientation (crystallinity) in PVC
Authors: McKinney Paul V. , Foltz Carl R.
Published: April 2003

A difference has been observed in the DTA and DSC curves for the glass transition of both PVC homopolymer and acetate copolymer, depending on the rate of quenching or annealing below the glass transition temperature. The difference has the appearance of an endothermal peak added to the glass transition curve and is attributed to an alignment of stereoregular chain segments of adjacent polymer molecules. The lengths of chain segments are assumed to be so short that no x‐ray evidence of crystallinity was obtained. The orientation process involved has an activation energy of 47.8 kcal./mole in the homopolymer and 43.6 kcal./mole in the copolymer. The measured rate of the process agrees with the principle of time–temperature superposition, the rates becoming equal for homopolymer and copolymer at equal temperatures below their glass transition temperatures.
Sorption of water vapor by B pattern starch
Authors: Morsi M. K. S. , Sterling C. , Volman D. H.
Published: April 2003

Water vapor sorption isotherms of cotton cellulose and B pattern starch preparations, potato starch, corn amylose, amylomaize, and retrograded potato starch, were determined at 5 and 25°C. The crystallinity fraction of these materials equilibrated with water vapor at various partial pressures was determined by x‐ray diffraction. The thermodynamic functions of adsorption were calculated, and B.E.T. constants were determined.
The effect of humidity on the tensile properties of TiO2‐filled poly(vinyl acetate)
Authors: Galperin I. , Arnheim W.
Published: April 2003

The tensile properties of TiO2‐filled poly(vinyl acetate) were studied at strain rates of 100%/min. to 5,000%/min. at 25°C. after exposure to relative humidities of 10, 25, 51, 70, and 90% for 160 hr. Filler concentrations studied were 0, 10, 20, 30, and 40 wt.‐% TiO2. The change in tensile properties with greater humidity was dependent on filler content. As the filler content increased, strength was lowered, elongation increased, and stiffness decreased with greater humidity. Generally, changes in tensile properties with humidity were less pronounced at higher strain rates. A mechanism is proposed where H2O alters the packing of polymer chains and affects the interaction of filler with polymer.
Polyolefin waxes
Authors: Coover H. W. , Combs R. L. , Guillet J. E. , Weemes D. A.
Published: April 2003

The properties of polylefin waxes derived from polypropylene, polybutene, and their copolymers are described, with particular references to those which are useful as coatings and barrier materials. These products can be applied with conventional melt‐ and curtain‐coating machines on paper and other substrates to give coatings with properties comparable to those of extrusion‐coated, plastic‐grade polyolefins. Because of their low melt viscosity and consequent ease of application, they should find wide application in the packaging industry.
Crosslinking of starch by alkaline roasting
Authors: Martin Irving
Published: April 2003

Dry mixtures of starch with various bases were roasted in air. The effects of roasting were determined by a viscosity method. The results suggest that roasting at alkaline pH's produces covalent crosslinks. The author speculates that the crosslinks result from a combination of autoxidation and aldolization.
Oxidative aging of natural rubber vulcanizates. Part I. The scission of peroxide vulcanizates
Authors: Bell C. L. M. , Tiller R.
Published: April 2003

A new method has been developed for measuring the number of molecules of oxygen required (ϵ) to cause a main chain scission in peroxide vulcanizates of natural rubber. This method is based on experimentally derived relationships and is not dependent on statistical theories of rubber elasticity. The value ϵ is only slightly temperature dependent, ranging from 28 at 65°C. to 22 at 100°C. The effects of several types of antioxidant have been examined, in all cases ϵ was greatly reduced. The effect of antioxidant 2246 has been studied in more detail and the results indicate that there is a high probability of scission occurring at the termination step in the oxidation chain.
A microscopic study of fracture in regenerated cellulose film
Authors: Hilyard N. C.
Published: April 2003

The fracture edge of a strip of regenerated cellulose film broken under tension can usually be divided into three regions: (A) the site of the initial failure, (B) the slow‐tear region, and (C) the fast‐tear region. Photomicrographs showing these regions are presented and discussed. Three different types of initial failure are described and some data presented relating the breaking strain to the type of initial failure.
Aliphatic heterocyclic polymers
Authors: Trischler Floyd D. , Kjoller Kendall J. , Levine Harold H.
Published: April 2003

Aliphatic polybenzoxazoles, polybenzothiazoles, and polybenzimidazoles have been prepared by three methods: in poly(phosphoric acid), by the polyamide precursor, and by melt polymerization. The melt polymerization method was found to be the most satisfactory. All of the aliphatic heterocyclic polymers had excellent thermal stability, resistance to alkaline hydrolysis, high glass transition temperatures, and a high degree of flexibility. The only class of polymer found having any degree of solubility, however, was the polybenzimidazoles. Aliphatic polybenzimidazole films were prepared by solution casting. These films were found to be extremely flexible at ambient and cryogenic temperatures. The films were unaffected by alkaline hydrolysis, even in an oxidizing medium. A molding prepared from the aliphatic polybenzimidazole had excellent physical properties at both cryogenic and room temperature.
Practical applications of GPC of interest to the polymer chemist
Authors: Harmon Dale J.
Published: April 2003

Five examples are discussed showing how gel permeation chromatography was applied to studies of polymer systems. The calculation of molecular weights from the curves was not pertinent to the studies. The only requirement was that the seperation be a size separation and the results be reproducible.
Kinetics of heterogeneous cellulose reactions. II. Reaction with propionyl chloride
Authors: Chatterjee Pronoy K. , Conrad Carl M.
Published: April 2003

A heterogeneous cellulose reaction was studied by reacting cotton fiber in pyridine medium with propionyl chloride at different initial molar concentrations and at different temperatures. It has been observed that the kinetics of reaction does not follow Sakurada's diffusion equation closely, and the deviation is more noticeable at lower initial concentrations of the reagent and at lower temperatures. A non‐uniform reaction rate is also evident from the time–substitution curve. The rate of substitution changes twice during the reaction, the latter change being associated with the loss of cellulose I crystal structure. In an attempt to treat the data according to simple chemical kinetics, the order has been found to decrease continuously from the beginning, suggesting thereby an autocatalytic type of behavior. However, at the finàl stages of the reaction, when the cellulose I structure was completely lost, the reaction behaved as a pseudo first‐order type. The x‐ray diffractograms of the reacted samples indicate that cellulose I crystallinity decreases from the beginning of the reaction and that a new crystalline lattice develops gradually. The formation of this new crystal lattice is hindered in the cellulose crystalline region due to the lack of freedom of the chains. The diffusion equation has been modified by substituting a crystallinity index for the rate of diffusion of solvent in a solvent–gel system and thus extending Sakurada's equation. A new mechanism has been proposed considering the simultaneous reactions in the amorphous and crystalline regions. This mechanism can explain the deviation of Sakurada's equation. The kinetics expressions are derived, based on the proposed mechanism. The kinetics of decrystallization of cellulose I is also presented. A satisfactory theoretical explanation is given for the fact that the fall of reaction rate occurs at the conclusion of decrystallization of the cellulose I structure.
Practical evaluation of the [η]–M relationship. II. Estimation of Kθ values of polymer solutions
Authors: Van Krevelen D. W. , Hoftyzer P. J.
Published: April 2003

A method is proposed for the prediction of the intrinsic viscosity of θ solutions, based upon the constitution of the dissolved polymer. The method makes use of additive values for constitutional groups to calculate a quantity that represents the specific chain stiffness per main chain atom.
Basic gel‐permeation chromatography studies. I. Polymer degradation
Authors: Hendrickson J. G.
Published: April 2003

Polymer degradation has been studied by using gel‐permeation chromatography (GPC) to measure the product distribution. The method is rapid and has a good accuracy that permits one to see most of the degradation products, as they elute at a point different from the starting material. In the cases studied, polystyrene cleavage has the result of random cleavage, as judged by the product distribution. A GPC curve to be expected from random cleavage has been put together to aid in the evaluation. Both wide and narrow molecular weight distribution polystyrenes have been studied after degradation. The narrow distribution products were degraded by peroxides, irradiation, and weathering. With the latter, the combination of simple fragments to form the starting portions of cromslinking were measured in small amounts. In none of the cases studied did degradation in solution produce crosslinked products. Kinetic rate studies were made that concerned the action of peroxides and inhibitors.
Phosphorus derivatives of methyl 2‐(chloromethyl)acrylate
Authors: Sherr Allan E. , Klein Harvey G.
Published: April 2003

Several phosphorus derivatives of methyl 2‐(chloromethyl)acrylate, including three phosphonium salts and one phosphonate ester have been prepared. A brief study was made of their polymerization characteristics under free‐radical conditions. Several factors were noted which prevented the synthesis of methyl 2‐[(diethoxyphosphinyl)‐methyl]acrylate in high yields in initial experiments. Homopolymerization of these phosphorus derivatives does not take place readily in the presence of free‐radical initiators.
Surface treatment of polymers for adhesive bonding
Authors: Schonhorn H. , Hansen R. H.
Published: April 2003

Further studies of a new and highly effective method for the surface treatment of low surface energy polymers for adhesive bonding are reported. Mechanisms are suggested for the increase in the cohesive strength in the surface region of polyethylene when it is exposed to activated species of inert gases. The technique is unique because, in contrast with results obtained with other methods, bulk properties of the polymer such as color or tensile strength and elongation are unaffected and surface properties such as wettability and dielectric properties such as surface conductivity are essentially unchanged.
Effect of water on the mechanism of deformation of nylon 6
Authors: Boukal Ivo
Published: April 2003

Lattice spacings perpendicular to the molecular chain axes and crystallite orientation of dried and moist (boiled in water) bulk nylon 6 were determined by x‐ray diffraction under tension of 30–300 kg./cm.2. The deformation of the specimen was also measured. The lattice spacings are changed reversibly by the presence of water in nylon 6, but the elastic moduli of the lattice are not affected. The lattice elastic modulus in the direction of the hydrogen bonds is approximately double its value in the direction normal to the hydrogen bonds. The elastic modulus of the dried nylon 6 approaches the value of the lattice elastic modulus in the direction normal to the molecular axes, while the modulus of the moist nylon 6 is several times lower. From these facts, and especially from the relations between the lattice deformation, crystallite orientation, and specimen deformation, the principal differences in the deformation mechanism of dried and moist nylon 6 were deduced. The results obtained have also made possible some general conclusions about the crystalline structure of nylon 6 and the deformation mechanism of linear polymers.
Graft copolymerization onto protein by the ceric ion method. Studies on grafting site
Authors: Imai Yohji , Iwakura Yoshio
Published: April 2003

Graft copolymerization of methyl methacrylate and acrylamide onto ovalbumin was carried out with redox system with ceric ion. Initiation of grafting occurred very rapidly, and the number of grafting sites reached a maximum after about 2 min. regardless of initial ceric ion concentration. The grafted polymer chains were separated by selective hydrolysis of the protein backbone with hydrochloric acid or protease in order to characterize the graft copolymers. The grafted polyacrylamide separated by the proteolytic digestion contained a carbohydrate residue at the end of the polymer molecule. The problem of grafting sites on ovalbumin is discussed.
Bonding polyethylene to metals
Authors: Vincent G. G.
Published: April 2003

A process for adhering polyethylene to aluminum was developed which involves treating the aluminium substrate successively with chromic acid and then a selected organic acid. Certain organic acids utilized in this process appeared to produce a synergistic effect on the adhesion. This process, which required no modification or treatment of the polymer, resulted in peel strengths forty times greater than that obtained on untreated aluminum. Tensile shear values for the polyethylene–aluminum bond were greater than 2800 psi. The materials used for treating the metal in this system produced a maximum in the obtainable peel strength. Furthermore, minor changes in the etching acids resulted in drastic changes in the adhesion values.