bluuebunny/crossref_metadata_2025 huggingface dataset:
The chemistry of sulfur curing. Part I. Kinetics of vulcanization of an EPDM elastomer accelerated by zinc dimethyldithiocarbamate
Authors: Wolfe James R.
Published: April 2003

The maximum cure rates of an EPDM rubber were determined by using the Monsanto oscillating disk rheometer and correlated against the initial concentrations of curing ingredients. Unaccelerated and ZnDMDC‐accelerated sulfur curing systems were used. The results were interpreted to indicate that both unaccelerated and ZnDMDC‐accelerated curing reactions proceed simultaneously in ZnDMDC‐accelerated stocks. The maximum cure rates of the ZnDMDC‐accelerated crosslinking reactions were found to be first‐order in initial ZnDMDC concentration, second‐order in initial cure site concentration, variable fractional order in initial sulfur concentration, and approximately zero‐order in initial zinc oxide concentration. The maximum cure rates of the ZnDMDC‐accelerated reaction were shown to be limited by the low solubility of ZnDMDC in the polymer. The maximum cure rates of the unaccelerated crosslinking reaction were found to be 0.6‐order in initial sulfur concentration, 1.2‐order in initial cure site concentration, and of a positive variable order in initial zinc oxide concentration.
Aging of polyblends
Authors: Boyle D. J. , Gesner B. D.
Published: April 2003

Methyl methacrylate–styrene–acrylonitrile copolymers, alone and with polybutadiene modification, were examined for changes in impact strength and yellowness after thermal and light aging. The copolymer displayed no change in strength or clarity, while the butadiene‐modified material showed increase in yellowness and loss in impact resistance. It is apparent that these changes are primarily due to the decomposition of the butadiene phase in the impact material, and this conclusion might be applied to diene‐containing blends in general.
Thermal and photo‐oxidation of polysulfone
Authors: Gesner B. D. , Kelleher P. G.
Published: April 2003

Prolonged heating at temperatures below 140°C. causes only slight changes in the properties of polysulfone. Exposure to ultraviolet light, however, results in substantial changes as evidenced by broad absorption in both the hydroxyl and carbonyl regions of the infrared spectrum, evolution of carbon monoxide and dioxide, decrease in polymer elongation and intrinsic viscosity, and pronounced yellowing. A free‐radical mechanism is proposed in which chain scission occurs with the formation of low molecular weight, oxidized fragments as the predominant oxidation products.
Elastomers based on cellulose fibers. II. Ethyl acrylate grafting onto disulfide‐crosslinked cellulose
Authors: Negishi Michiharu , Nakamura Yoshio , Hosoi Masahiro
Published: April 2003

Partially disulfide‐crosslinked viscose rayon fibers (SS 2.3 mole/104 g. cellulose) were prepared by means of mercaptoethylation and successive oxidation and then grafted to the extent of 200–1200% graft‐on of ethyl acrylate with or without preswelling by zinc chloride, by using the ceric ion method. The tensile strength, breaking elongation, initial modulus, elastic recovery, and extension energy loss of the modified fibers were measured. In the disulfide‐crosslinked, about 1000% ethyl acrylate‐grafted fibers with preswelling, typical rubber elasticity was found. The disulfide crosslinkage in the grafted fibers was found generally to be capable of cleaving and re‐forming by the reduction and successive oxidation treatments, and the properties were also well reversible. Therefrom, it was confirmed that intermolecular crosslinking between cellulose molecules plays an important role for developing of elastomeric properties, as was found for the methylene‐crosslinked and grafted fiber reported previously. Most of elastomeric properties in our grafted fibers seem to be essentially attributable to the random conformation of the decrystallized, disoriented, and weakly crosslinked cellulose chains which are embedded in a matrix of flexible graft polymers.
Effects of substitution of triphenylmethyl groups into cellulose on the fine structure and thermal properties of the products
Authors: Conrad C. M. , Stanonis D. J. , King W. D. , Harbrink P.
Published: April 2003

Mercerized cellulose in the form of 7/2 yarn was reactivated with 17.5% sodium hydroxide and then heated at 100°C. with 5 moles of trityl chloride, in pyridine, per anhydroglucose unit. The time of reaction was varied, giving ether derivatives of the cellulose containing 0.31–0.79 triphenylmethyl groups (DS) per anhydroglucose unit. Controls consisted of (1) the untreated cellulose yarn and (2) a portion subjected to all the reaction conditions except the reactant. The density of the product decreased hyperbolically with increasing substitution. The mixed x‐ray pattern of the untreated control cellulose (35% cellulose I, 43% cellulose II) was largely converted by the activation treatment (10% cellulose I, 53% cellulose II). As reaction proceeded the crystal structure largely disappeared. The assumption is that substitution was confined almost exclusively to the primary hydroxyl position. The behavior of tensile stiffness, elastic recovery, and work recovery was explored at temperatures from about 25 to 225°C. Considerable improvement, which generally increased with increasing substitution, was observed in both elastic and work recovery at all temperatures studied.
Surface treatment of polymers. II. Effectiveness of fluorination as a surface treatment for polyethylene
Authors: Schonhorn H. , Hansen R. H.
Published: April 2003

An effective surface treatment for adhesive bonding of polyethylene has been developed. It involves exposing the polymer to an environment of elemental fluorine or fluorine diluted in argon. By this treatment, extensive fluorination of the surface region is effected. The fluorinated surface permits formation of strong adhesive joints by conventional adhesive bonding techniques even though the wettability of the new surface is similar to polytetrafluoroethylene. We believe that treatment of the polymer with elemental fluorine effectively eliminates the weak boundary layer associated with polyethylene by either crosslinking or by increasing the molecular weight in the surface region.
Solution polymerizations of epoxytetrahydrophthalic anhydride and its utilization in various epoxy systems
Authors: Cassidy P. E. , McCarthy D. K.
Published: April 2003

Solution polymerization of epoxytetrahydrophthalic anhydride (ETHPA) has been thoroughly studied by using numerous solvents and catalysts. Products have been obtained in high yields, particularly when triethanolamine was the catalyst. This suggests that this catalyst should be considered for further applications utilizing ETHPA. However, the solution polymerization method cannot be used alone to define the effects of various catalysts on standard nonsolvated resin systems, because polymerization is greatly affected not only by the addition of solvent but also by the type of solvent. In addition, the action of the catalyst seems to depend greatly upon what solvent is employed. The reason for this dependence has not been established. The effects of the addition and reaction of ETHPA with commercial epoxy resin formulations have been investigated by means of heat distortion tests and differential thermal analyses. In most cases, although a moderate improvement was found in the thermal properties of the resins, occasional excellent results were obtained. A 10°C. increase in HDT is observed with a 2 wt.‐% addition of ETHPA for bisphenol A epoxy resin–bicyclic anhydride mixture. The degree of elevation of Tg and HDT with the addition of ETHPA obviously depends not only on the composition of the resin system but also on its cure temperature. A good correlation occurs between heat‐distortion temperatures and glass transition temperatures. Some few anomalous data, however, are found which point to the fact that further investigation is required before HDT and Tg can be interchanged without prior evidence of a definite relationship.
Reactions catalyzed by minerals. Part III. The mechanism of spontaneous interlamellar polymerizations in aluminosilicates
Authors: Solomon D. H. , Loft B. C.
Published: April 2003

The spontaneous polymerization of hydroxymethacrylate monomers by the layer aluminosilicate montmorillonite is reported. Saturation of montmorillonite by acrylic monomers gives interlayer complexes of three types, only one of which is susceptible to spontaneous polymerization. Electron‐donating sites situated within the silicate lamellae initiate the spontaneous polymerization which it is suggested proceeds by a mechanism involving radical‐anions. The results of this study together with those reported previously are used to explain the variety of effects noted when aluminosilicates are added to or heated with vinyl or acrylic monomers.
Epoxy polymers. II. Macrostructure
Authors: Cuthrell R. E.
Published: April 2003

A variety of measurements indicate that thermosetting epoxy polymers contain closely packed floccules and an interstitial liquid similar to the starting materials. The fioccules are thought to be of colloidal origin and appear to be ordered with respect to each other in a three‐dimensional array.
Stabilization of high‐density polyethylene
Authors: Rothstein Edwin C.
Published: April 2003

Several types of antioxidants are evaluated in high‐density polyethylene for color and physical property stabilization during processing and thermal aging. A wide variety of evaluation tests are used and discussed. Heat‐ and light‐induced oxidation mechanisms are reviewed. Antioxidants such as octadecyl‐3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate and tetrakis[methylene 3‐(3′,5′‐di‐tert‐butyl‐4′‐hydroxy phenyl) propionate] methane were found to provide very high retention of physical properties, excellent initial color and color retention. Combinations of antioxidant‐ and ultraviolet light absorbers were evaluated for stabilizing high density polyethylene exposed to artificial light and outdoor weathering. The combination of octadecyl‐3‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl) propionate and 2‐(2′‐5′‐di‐tert‐butyl‐2′‐hydroxy‐phenyl)‐5‐chlorobenzotriazole was found to be a very efficient stabilizer system. Polymer containing this stabilizer combination had excellent color stability and minimum crosslinking and embrittlement after Arizona weathering.
Diffusion of additives in polyolefins
Authors: Jackson R. A. , Oldland S. R. D. , Pajaczkowski A.
Published: April 2003

A simple radio‐tracer method based on 14C is described for determining the diffusion coefficient of an additive in a polymer. Two theoretical models representing extreme cases for the diffusion system are discussed and shown to yield the same solution to within 10%. The diffusion coefficients of didodecyl 3,3′‐thiodipropionate, N‐octadecyldiethanolamine, and 1,1,3‐tri(2‐methyl‐4‐hydroxy‐5‐tert‐butylphenyl)butane migrating in polyethylene, polypropylene, and poly‐4‐methylpentene‐1 have been measured over temperature ranges of 50–80°C., within the range 20–200°C. In each case the variation of the diffusion coefficient D with temperature T can be represented by an Arrhenius equation D = D0 exp {‐E/RT}, where the activation energy E is virtually independent of the size and shape of the diffusing molecule. The activation energy depends upon the polymer and is about 12.5, 21, and 14.5 kcal./mole for polyethylene, polypropylene, and poly‐4‐methylpentene‐1, respectively.
Ceric ion‐induced redox polymerization of acrylonitrile on cellulose
Authors: Kulkarni A. Y. , Mehta P. C.
Published: April 2003

The ceric ion‐cellulose redox system has been studied for grafting acrylonitrile on cotton fibers. Grafting yields are very high as compared to the persulfate‐thiosulfate redox system reported earlier. Traces of copper sulfate in the reaction mixture do not increase grafting yields, unlike the persulfate‐thiosulfate system. The high polymerization rate on cotton fibers is shown to be due to the reducing action of cellulose and not to the large surface area of cotton fibers. The Ce+4 consumption during grafting is higher than during oxidation of cellulose, indicating formation of homopolymer during the grafting reaction. Studies on the consumption of Ce+4 by model compounds such as D‐glucose and α‐methyl‐D‐glucoside show that the hemiacetal group in D‐glucose is responsible for a faster rate of Ce+4 consumption. Formation of a Ce+4‐alcohol complex also contributes to the initial fast rate of Ce+4 consumption. Studies on the oxidation of cellulose by Ce+4 indicate that the initial oxidative attack occurs on carbon atom 2, with the formation of a >CO group. On further oxidation, cleavage of the C2‐C3 bond occurs as shown by the presence of glycol aldehyde determined chromatographically. Cellulose‐polyacrylonitrile grafts have been isolated by an acetolysis treatment followed by extraction with dimethylformamide. Number‐average molecular weights of the isolated fractions are approximately 50,000–55,000. A theoretical method to calculate the number‐average molecular weights, based on the PAN and the COOH contents of the grafted cellulose, is described.
Some viscoelastic properties of ABS polymer
Authors: Scalco E. , Huseby T. W. , Blyler L. L.
Published: April 2003

The discrete relaxation spectrum of an ABS (acrylonitrile–butadiene–styrene) polymer at 190°C. was calculated by using results from tensile relaxation moduli and the principle of reduced variables. The shift factor was found to conform well to the WLF equation, and the free volume fraction at Tg was calculated to be 0.026 in good agreement with the universal value. The values of the thermal expansion coefficient of free volume were calculated to be 9.8 X 10‐4 deg.−1 and 7.0 × 10−4 deg.−1, respectively, from the WLF coefficients and from dilatometric results. The width of the entanglement plateau of the relaxation spectrum was observed to be a factor of approximately 2 larger than that calculated from molecular weights between entanglement couplings determined either from rubber elasticity theory or from an assumed molecular model which discounts the presence of the butadiene in the ABS system. By using Pao's theory, flow curves at 190°C. were calculated both from the discrete relaxation spectrum and from the dynamic modulus. These curves were essentially identical. However, the stress values of these curves were found to be about a decade higher than those experimentally determined from capillary flow measurements. Nevertheless, the shapes of the curves are in good agreement, and an explanation is suggested for existing discrepancies. Flow instability, processing variables, and residual strains are discussed in light of the flow curves and the calculated recoverable shear strains.
Study of a heat‐resistant plastic laminate from the standpoint of a mechanical–chemical equation of state
Authors: Goldfein S.
Published: April 2003

The object of this study was to analyze the complex degradation history of a heat‐resistant epoxy resin laminate using the mechanical–chemical equation of state. A further object was to determine if weight‐loss measurements at elevated temperatures could be used to predict long‐term rupture strength. Master rupture curves drawn by using a second‐order parametric form of the equation of state largely clarified the anomalous behavior of the laminate. It was not found possible to predict the longterm mechanical properties from weight‐loss data although there was evidence of some correlation.
Equation of consumption rate of free‐radical vinyl polymerization. II
Authors: Sasaki Hideki
Published: April 2003

The vinyl polymerization reaction is a two‐molecule reaction. However, it is more convenient to use a specially defined rate constant than to use the general constant, because a new radical is formed instantaneously in the same radical compound when one monomer combines with an existing radical in a living polymer or an initiator radical. This special rate constant is named the propagation constant and is proportional to the concentration of monomer when the polymer is formed from a unit mole concentration of the initiator radical. The specific propagation constant is related to the concentration of monomers which react in unit time and unit concentration of monomer and radical. Arnett's experiments are discussed in terms of the equation formulated. The value of Δ[M]/([M]0·t) is found not to be a reaction rate but a value of ln [M]0/[M] when [M]0 – [M] is very small. Autoacceleration of the polymerization is found with high concentrations of monomer which yield an increase in the velocity of propagation and also at low concentrations of initiator, which cause prolongation of the propagation stage. When the concentration of initiator is high, this phenomenon does not take place until enough initiator is consumed and the necessary low initiator level is reached. The time required is called the induction period. The larger the polymer molecule is, the higher the viscosity becomes.
Factors affecting the strength of a polyhydroxy ether
Authors: Golden J. H. , Hazell E. A. , Wright H.
Published: April 2003

The effects of moisture content, aging, annealing, irradiation, temperature, and rate of testing on the tensile yield strength of the polyhydroxy ether derived from bisphenol A and epichlorohydrin are described and discussed. In particular, annealing at temperatures below Tg is shown to cause significant increases in strength which are associated with an endothermal process in the glass transition region having an activation energy of 32.8 kcal./mole. The nature of this process and its occurrence in other polymers is discussed. Annealed and unannealed specimens are shown to obey the previously proposed empirical relationship, 1/σ = a + m log t, where σ is the tensile yield strength, t is the time to yield. The values of the constants a and m have been derived.
Torsional braid analysis of antioxidant activity in elastomer systems. I. Initial studies
Authors: Williams Bernard L. , Weissbein Leonard
Published: April 2003

The torsional braid apparatus as originally described by Lewis and Gillham has been explored as a means of providing a quantitative measure of antioxidant activity of selected compounds when formulated with certain elastomer systems prone to oxidative crosslinking on heat aging. With this technique the time dependence of the sharp torsional modulus increase, corresponding to a change from a rubbery to a highly crosslinked state, is determined. This time dependence is taken as a measure of the rate of oxidative crosslinking in heat‐aged elastomer films coated on a fiber‐glass braid. In this manner an assessment of the activity of antioxidants can be made. To illustrate the application of this technique, two initial studies will be cited. In one study the relative protective effect on a carboxylated styrene‐butadiene latex system of a series of antioxidants was found to be in the following order: α, α′‐2,6‐bis(2‐hydroxy‐3‐tert‐butyl‐5‐methylphenyl)xylenol > the reaction product of nonylated paraethylphenol and formaldehyde > crude 2,2′‐methylene bis(6‐nonylparacresol). In another study, with cis‐polybutadiene as the elastomer, the effectiveness of a series of antioxidants was found to be in the following order: 2,2′‐methylene bis(6‐tert‐butyl paracresol) > 1,3,3,5‐tetramethyl‐1‐m‐tolylindane‐4′,6‐diol > 4,4′‐methylene bis(2,6‐di‐tert‐butylphenol). In addition, the effect of concentration and temperature was studied with the most efficient antioxidant in this last series.
Acrylate monomers from olefins via tertiary butyl hypochlorite
Authors: Nevin C. S.
Published: April 2003

A variety of olefins were readily converted to acrylate monomers by combining them with t‐butyl hypochlorite and acrylic or methacrylic acid at 25–65°C. The predominate product was the vicinal acyloxychloro derivative formed by addition at the olefinic double bond. By‐products were the vicinal butoxychloro derivative and the still unsaturated chlorinated olefin. The main reaction was shown to occur by an ionic mechanism. 2‐Chloro‐1‐methyl propyl methacrylate was isolated and identified as the main product of the reaction of 2‐butene, methacrylic acid, and t‐butyl hypochlorite. The crude olefin products readily homopolymerized and copolymerized with other vinyl monomers by incorporating free‐radical initiators.
Time‐dependent capillary flow of polyethylene melt
Authors: Kataoka Tadao , Ueda Shigeyuki
Published: April 2003

The variation of output rate with extrusion time is examined experimentally for capillary flow of high density polyethylene melt. The increase in output rate is divided into two parts. One of these is due to the decrease in the amount of the material in the reservoir and is well interpreted from the consideration of the so‐called reservoir effect. The other part is mainly attributed to the disentanglement or orientation of polymer chain during flow in the reservoir.
Diffusion, membrane selectivity, and nonequilibrium effects in rapid membrane osmometry
Authors: Ghosh Kalyan K. , Swenson Harold A.
Published: April 2003

Rapid membrane osmometry, narrow distribution polystyrenes in the range 4000–700,000, and three membrane types of different porosity were used to study the effects of diffusion and of Staverman membrane selection in osmometry. It was found that equilibrium was not obtained in the rapid measurement with the two densest membranes which led to grossly low values for the high molecular weight sample but had small effect at low molecular weights. Because of membrane selectivity effects at lower, and of nonequilibrium effects at higher molecular weights, the effective range was about 4000–350,000 for the densest membrane, 90,000–500,000 for the medium porosity membrane and from 145,000 to an unrestricted upper limit for the grossest membrane. A unique characteristic of the Mechrolab 501 instrument used in the study is the small constant volume on the solvent side of the membrane which allows determination of the osmotic pressure of the diffused material and its concentration when the molecular weight is known. Diffusion can be avoided if the pressure reading is taken quickly enough but membrane selectivity effects cannot be avoided if diffusible solute is present. Enormous selectivity effects were found when mixtures of diffusible and nondiffusible molecules were measured. Experimental values of the selectivity coefficient Sn of the mixtures were found to agree closely with those calculated from the Staverman equations. Estimates of the coil size of the polymers are given to provide an estimate of the effective porosities of the membranes.
Ultraviolet irradiation of poly(vinyl chlorides). Part I. Effect of substituents on radiation parameters
Authors: Kwei Kwri‐Ping Shen
Published: April 2003

The crosslinking and main‐chain scission of PVC and its derivatives by ultraviolet radiation at 2537 A. were investigated. Examination of the relationship between gel fraction and radiation dose showed that the number of crosslinks formed in pure PVC per 100 e.v., Gc., was 0.29 and did not vary greatly from pure PVC to commercial PVC. However, the efficiency of scission was lowest (Gs = 0.06) for purified PVC, increased to 0.23–0.26 for commercial PVC, and increased further when chelates were substituted on PVC at C1 atoms. Gs for PVC with opper thalocyanine was 0.62, with copper salicylate was 1.38, and was 6.20 with ferrocene. Gc values also increased in the same order, from 0.40 to 3.10. The ratio of main‐chain fractures to number of crosslinks formed (β/α) increased again in this order from 0.1 for purified PVC to 1.0 for PVC–ferrocene. For purified PVC, β/α increased after 36 hr. of ultraviolet irradiations. In the presence of copper salicylate and ferrocene, ion‐radical reactions probably contribute towards the high β/α ratio. Ability of the aromatic substituents to enter chain–transfer reactions with polymeric radicals followed by coupling reactions may contribute partly towards crosslinking in PVC.
Irradiation of poly(vinyl chlorides). Part II. Effect of dynamic mechanical properties
Authors: Kwei K.‐P. S. , Kwei T. K.
Published: April 2003

The dynamic Young moduli of purified PVC and PVC derivatives were measured at room temperature during the course of irradiation by ultraviolet light at 2537 A. wave‐length. The PVC derivatives with copper salicylate, ferrocene, or copper phthalocyanine were prepared by Friedel‐Crafts reaction as described in the previous paper. The loss tangent decreased monotonically with irradiation time, while the dynamic modulus appeared to pass through a maximum. More pronounced variations in both E and tan 6 were observed for the PVC derivatives than for the purified PVC, owing to enhanced crosslinking and scission in the presence of the substituents. The gel permeation chromatograms of irradiated PVC samples have been observed to skew to the left, where low molecular weight material occurs. The decrease in E after long exposure was discussed in terms of molecular polydispersity of the soluble fractions of PVC.
Dye‐sensitized photopolymerizations of acrylic monomers in the presence of fibrous proteins
Authors: Needles H. L.
Published: April 2003

Dye‐sensitized photopolymerizations of low concentrations (1–5%) of acrylic monomers proceed at 40°C., if fibrous proteins (keratin, fibroin or collagen) are suspended in solution. In the absence of dye (riboflavin or fluorescein) or fibrous protein no appreciable photopolymerization of monomer is observed at the short irradiation times (120 min.). Graft products containing 0.5–23% polymer are found. The quantity of grafted polymer introduced into the protein depends on the chemical nature and concentration of monomer, dye, and fibrous protein. Homopolymerization of monomer is observed to some extent in each graft polymerization. In the presence of oxygen an induction period ia found, but removal of oxygen from solution greatly retards these photo‐polymerizations. Chemical and physical characterization of the protein–polymer products suggests that only a small number of initiation and grafting sites are present in the protein and that the grafted polymer partially resides within the protein matrix. We believe these photopolymerizations proceed via a free‐radical pathway involving radicalabstraction of hydrogen from the protein by dye intermediates.
Instability and failure phenomena in polymer processing with application to elastomer mill behavior
Authors: White James L. , Tokita Noboru
Published: April 2003

The mill behavior of different elastomers is discussed in some detail and contrasted with melt fracture in extrusion. The mill characteristics of elastomers are discussed, with special emphasis on effect of roll speeds and nip and on molecular structure of elastomer. Theories of failure mechanics in polymer processing are contrasted, and a theory of a viscoelastic material that exhibits rupture above a critical recoverable energy is analyzed. Mixing with carbon black is briefly discussed.
The thermal degradation of an amine‐cured epoxide resin at temperatures between 200°C. and 310°C.
Authors: Patterson‐Jones J. C. , Smith D. A.
Published: April 2003

This paper describes the nonoxidative thermal degradation of an epoxide resin based on the diglycidyl ether of bisphenol A crosslinked with p,p′‐diaminodiphenyl methane. Temperatures of degradation lay between 200 and 310°C. and the process was followed concurrently by three means: changes in dielectric properties, changes in infrared spectra, and weight loss. Dielectric properties support the contention that there is a dehydration step during degradation. It is proposed that vacuum curing at high temperature can produce optimum crosslinking. Evidence of phenol and N‐methyl aniline as degradation products is advanced, and possible degradation mechanisms are discussed.
Cerium‐initiated grafting of acrylonitrile onto cellulosic materials
Authors: Hebeish A. , Mehta P. C.
Published: April 2003

Grafting of acrylonitrile onto native cotton, swollen cotton, viscose, ramie, and hydrocellulose was studied with tetravalent cerium as initiator. The effect of temperature on the graft yields is examined. With ceric ammonium nitrate the grafting yields are found to be higher at 20 and 40 than at 60°C. Ceric ammonium sulfate, on the other hand, produces more grafting at 60 than at 20 and 40°C. The consumption of ceric ions is less, whereas the per cent graft yields are higher for the swollen cottons and viscose than for native cotton. Graft yields are shown to be related to substrate accessibility if the grafting reaction is carried out under conditions that suppress homopolymerization. Oxidation of these celluloses with CeIV has also been studied. It is found that more CeIV is consumed during grafting than during oxidation of cellulose under identical reaction conditions. Excess CeIV consumed in the grafting reaction has been shown to be directly related to extent of homopolymerization, which accompanies grafting. Some data on the storage stability of the free‐radical activity produced by oxidation of cellulose with CeIV are also reported. It is observed that the cerium‐oxidized samples can initiate graft poly merization even after 4–5 hr. if stored in nitrogen.
Note on the iterative calculation of relaxation spectra
Authors: Tanner R. I.
Published: April 2003

The use of exact numerical methods for calculating spectra from dynamic moduli is shown to lead to acceptable results when a modified numerical method is employed. The modification avoids the wild oscillations encountered with existing methods when difficult experimental data containing sudden spectral cutoffs must be analyzed.
The modulus and yield stress of glassy poly(methyl methacrylate) at strain rates up to 103 inch/inch/second
Authors: Holt David L.
Published: April 2003

Specimens of poly(methyl methacrylate) (PMMA) were compressed at nominally constant strain rates ranging from 10−5 to 103 in./in./sec. at 0, 22, 50, and 115°C. A plot of stress at a small fixed strain (2%) and constant temperature versus logarithm of strain rate is sigmoidal in shape and, furthermore, time‐temperature superposition could be used to construct a master curve of stress versus temperature‐compensated strain rate. It is suggested that the sigmoidal curve is a manifestation of the β transition in PMMA, and this is supported by the measured value of activation energy and the strain rate value at the point of inflection on the curve. By contrast, yield stress varies linearly with log \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm \varepsilon }\limits^{\rm.} $\end{document}. Time‐temperature superposition could not be applied. Rationalizing on the basis of the high stress form of the Eyring equation, yielding is by a yet unspecified molecular mechanism in which activation volume has the order of magnitude of a monomer unit but increases with increasing temperature.
An investigation of the polymerization of furfuryl alcohol with gel permeation chromatography
Authors: Wewerka E. M.
Published: April 2003

Several series of furfuryl alcohol resins, made by the polymerization of furfuryl alcoho with a variety of catalysts and having viscosities as high as 7 × 106 cpoise, were characterized by gel permeation chromatography (GPC). A series‐by‐series comparison of the GPC curves of the resins was made, to determine the effects of catalyst type and concentration on resin molecular structure as elucidated by GPC. Furfuryl alcohol resins were produced not only by thermal polymerization but also by catalysis with Imaleic anhydride, 86% phosphoric acid, γ alumina, and anhydrous magnesium sulfate. The gel permeation chromatograms of the resins made by catalysis with maleic anhydride were found to be nearly identical with those catalyzed with 86% phosphoric acid. Moreover, catalyst concentration did not affect the GPC curves of the resins catalyzed by maleic anhydride. These observations are consistant with an initial reaction mechanism, of which the rate‐controlling step is a function of pH. The chromatograms of the resins made by catalysis with γ alumina showed a shift of the peak maximums of the lower molecular weight species to lower elution volumes, indicating that esterification of the free hydroxyl groups with levulinic acid and other related acids may have taken place. The resins polymerized by thermal catalysis and by catalysis with anhydrous magnesium sulfate exhibited GPC curves that fell between those of the resins catalyzed by acids and those of the resins made by catalysis with γ alumina.
The determination of reactive‐group functionality from gel point measurements
Authors: Strecker Ruediger A. H. , French David M.
Published: April 2003

The usual method of calculating functionality is to divide the molecular weight by the equivalent weight. Because of the uncertainty of molecular weight determinations in the range 1000–20,000 a more precise method is needed. Several authors have published work concerning the determination of the extent of reaction at the gel point through the functionalities of the reactants. It occurred to us that this method could be reversed. We chose Stockmayer's treatment, with some changes, to calculate the average functionality of carboxyl‐terminated polybutadiene (CTPB): (PAPB)gel = (fE − 1)−1 (gE − 1)− where fE and gE are the weighted average functionalities of all molecules bearing the reactive groups A and B, and PA and PB are the fractions of initially present groups that have reacted. Two systems with an epoxide and glycerol as curing agents were investigated. The influence of dilution was investigated. Nonfunctional polybutadiene did not interfere with the accuracy of the determination of carboxyl functionality. By changing the ratio of epoxide to COOH groups from 0.6 to 1.4 it was shown that the calculated functionality remained constant. Weight‐average molecular weights for three CTPB samples were calculated from the functionality and the equivalent weight. They were compared with those obtained from intrinsic‐viscosity measurements. The precision of the functionality numbers is believed to be ±1%.
Polymerization of aromatic nuclei. XIII. X‐ray analysis and properties of poly(p‐phenylene) pellets
Authors: Kovacic Peter , Feldman Michael B. , Kovacic Jan P. , Lando Jerome B.
Published: April 2003

X‐ray diffraction experiments with poly(p‐phenylene) pellets demonstrated an increase in crystallinity with increase in molding temperature or annealing temperature. The increase in crystallinity may be attributed to annealing effects and loss of chlorine under severe conditions. Lattice constants for the crystalline polymer are presented, and the crystallographic data are compared with those of the lower oligomers. Poly(p‐phenylene) was investigated also in relation to oxidative thermal stability, chemical and solvent resistance, and the effect of temperature and variation in molding conditions on fracture strength. The decrease in strength at elevated temperatures appears to be related to the increase in crystallinity.
Elastic behavior of concentrated solutions of acrylonitrile copolymers. II. The shear‐stress dependence of the shear modulus of a pseudo network in concentrated solutions
Authors: Hayahaila Takuro , Takao Seiji
Published: April 2003

The shear‐stress dependence of the shear modulus in concentrated solutions of acrylonitrile copolymer was investigated by the capillary end‐correction method. The shear modulus decreases with an increase of shear stress above a critical polymer concentration at ti higher shear rate than that at which the decrease of the viscosity begins to occur. The non‐Hookian behavior of the concentrated solutions may be considered to arise from the breakdown of the tangled network structure, namely elastically deformable pseudo network.
The effect of surfactant and copolymer polarity on the film‐formation temperatures of some vinylidene chloride copolymers
Authors: Powell E. , Clay M. J. , Sauntson B. J.
Published: April 2003

The minimum temperature required for a copolymer emulsion to form a continuous film Tmf, and the glass transition temperature Tg of the copolymer were studied for vinylidene chloride‐acrylate copolymers and vinylidene chloride‐acrylonitrile copolymers. The Tmf and Tg were studied as a function of the nature of the surfactant used in the preparation of the emulsion. The Tmf was found to deviate markedly from the Tg for most compositions and the Tmf‐composition curves were found to be similar in shape to the Tg‐composition curves, exhibiting a maximum in the case of the acrylate copolymers. The quantity Tmf—Tg changes from negative to positive with decreasing polar character of the methyl and ethyl acrylate copolymers. This is especially obvious in the ethyl acrylate copolymer. The high Tmf values for copolymers containing acrylonitrile is attributed to strong interchain forces, which orientate the neighboring segments in a latex particle unfavorably for interpenetration with other particles. The nature of the surfactant used in the preparation of the emulsion was found to affect the Tmf. Emulsions of nonpolar, hydrophobic copolymers containing a blend of anionic and nonionic surfactants have a higher Tmf than those containing only anionic surfactant; however, with an increase in the amount of hydrophilic units in the copolymer the converse is true, except in the case of the highly polar copolymers of vinylidene chloride‐methyl acrylate, in which the Tmf's for both surfactant systems are similar.
Turbidimetric determinations of theta compositions
Authors: Suh K. W. , Clarke D. H.
Published: April 2003

The turbidimetric titration method of determining theta conditions developed by Elias and modified by Cornet and van Ballegooijen has been extended and generalized for different types of polymer–solvent–nonsolvent systems. The modified procedures for the determination of theta compositions have been verified with the following systems: polystyrene–cyclohexane–n‐hexane, polystyrene–cyclohexane–n‐butanol, and polystyrene–toluene–nonsolvent.
Radiation chemical studies of protein reactions: Effect of protectors against radiation
Authors: Nisizawa Mizuho
Published: April 2003

Sodium glutamate and sodium benzoate were found to protect protein reactions from radiation damage. The behavior of the viscosity changes was determined. The experimental equation for the protective effect is given by ηred(∞) = a(log X)2 + b(log X) + c, where ηred(∞) is the reduced viscosity of the solution at infinite time X is the concentration of the radiation protectors, and a, b, and c are adjustable constants.
Pyrolysis of phenolic resins. IV.
Authors: Learmonth G. S. , Osborn P.
Published: April 2003

Thermoset resins were made from benzene, naphthalene, phenanthrene, anthracene, or pyrene by condensation with p‐xylylene dichloride in presence of stannic chloride. The extent of reaction, consequently the crosslink density, was controlled by measurement of the HCl evolved. The absence of oxidation was confirmed by infrared spectroscopy. On pyrolysis at 500, 1000, and 1200°C. in vacuo (after Madorsky) it was found that the yield of char was directly related to the number fraction of carbon atoms in the aromatic nucleus used. Benzene was anomalous, and all resins gave lower char yields than standard phenol formaldehyde resins.
Mechanism of photostabilization of polypropylene by nickel oxime chelates
Authors: Briggs P. J. , McKellar J. F.
Published: April 2003

Recent work has shown that certain nickel oxime chelates act as effective light stabilizers for polypropylene. The mechanism of their protective action was examined by spectrophosphorimetry and flash photolysis. Examination of the phosphorescence from the commercial polymer shows that it is due to aldehydic carbonyl groups. From flash photolysis observations of the triplet quenching action of a range of nickel chelates it is suggested that stabilization by the oxime chelates is achieved by a mechanism of efficient energy transfer from the photoreactive carbonyl group to the chelate, where the energy is harmlessly dissipated. The efficiency of this quenching action is primarily dependent on the spatial configuration of the ligand around the central metal atom in the chelate.
Radical bulk polymerization of N‐vinylcaprolactam
Authors: Solomon O. F. , Corciovei M. , Boghin˘ C.
Published: April 2003

Bulk radical polymerization of N‐vinylcaprolactam was studied at temperatures between 60 and 120°C. with different initiators. Satisfactory results were obtained with azobisisobutyronitrile, tert‐butyl perbenzoate, and tert‐butyl peroxide as initiators. The polymerization reaction of N‐vinylcaprolactam with these initiators is first order with respect to the monomer and 0.5 order with respect to the initiator. A linearity of the kinetic curves up to high conversions was observed. The cause of this behavior is a feeble gel effect, which also induces an increase of the molecular weight during polymerization.
Environmental stability of ethylene–acrylic acid adhesive copolymers bonded to metal substrates
Authors: Wargotz B.
Published: April 2003

A study was conducted on the influence of high humidity and temperature on aluminum and copper sheet coated with ethylene–acrylic acid or ethylene–methacrylic acid copolymers. Infrared spectrometric and differential thermal analysis data indicate that a contributing cause to failure of the bond between the acrylic acid copolymers and copper is the solubilization of an underlying weak oxide layer under conditions of the test. No significant weakening of the bond of aluminum–adhesive copolymer was observed under high humidity. From oxygen uptake studies, thermogravimetric analysis in air, and infrared spectra of polymer bonded to metals, a general understanding of the thermal‐oxidative stability of the ethylene–acrylic and ethylene–methacrylic copolymers has emerged. The acrylic acid copolymers are less stable in an oxidative environment than ethylene homopolymers and the ethylene–alkyl acrylate copolymers.
Effects of thermal history on isotactic polypropylene
Authors: Pae K. D. , Sauer J. A.
Published: April 2003

The effect of past thermal history on the melting behavior of isotactic polypropylene is investigated in some detail. It is shown that a series of stepwise annealing treatments at steadily increasing temperatures will raise the final melting point and will result in a double endothermic peak if the final anneal temperature is at or close to 160°C. It is also shown that a series of stepwise annealing treatments at steadily decreasing temperature will lead to multiple DSC peaks. The number of such separate peaks is equal to or greater than the number of annealing steps. Even low‐temperature anneals (100–130°C) affect the melting endotherm, while high‐temperature anneals have a marked effect on both the degree of crystallinity of the sample and the final melting temperature. For a 3‐min anneal, the highest degree of crystallinity is produced by an anneal temperature of 155°C. The highest melting temperature (∼182°C) is produced by a 30‐min, or longer, anneal at about 160°C. The implications of these results in terms of crystal thickening and perfection are discussed.
Effects of thermal history on polypropylene fractions
Authors: Sauer J. A. , Pae K. D.
Published: April 2003

The effects of thermal history on the melting behavior of several polypropylene fractions have been studied. The specific fractions investigated include one that has crystallized in the triclinic modification, one that has crystallized in the monoclinic modification, and a third that contained a combination of the two types of crystals. Thermal histories given to these specimens included a series of stepwise annealings at steadily decreasing temperatures, a series of annealings for various times at a given elevated temperature, and a series of stepwise annealings at a set of steadily increasing temperatures. The melting behavior was investigated by means of a differential scanning calorimeter and various DSC peaks are presented. The nature of multiple peaks produced by the different treatments is discussed, and the results are compared with similar data obtained on whole polymer.
Crosslinking efficiency of gelatin hardeners
Authors: Tabor B. E.
Published: April 2003

By using the criteria of melting point and sol fraction, a study has been made of the stoichiometric efficiencies of hardeners for gelatin, as distinct from their rates of reaction. The factors which affect these measurements were investigated. Both melting point and sol fraction distinguish gelatins in respect of molecular weight and origin. Sol fraction measurements give evidence of molecular weight distribution. Various hardeners have a wide range of molecular efficiencies, and these do not correlate with rates of reaction as judged from solution viscosity rise methods. Sol fraction measurements can separate hardeners which would have been considered similar from melting point behavior.
Molecular weight changes during polyolefin autoxidation
Authors: Reich Leo , Stivala S. S.
Published: April 2003

Expressions were derived relating changes of intrinsic viscosity to reaction time, based on a scheme previously presented for the uncatalyzed, uninhibited thermal oxidation of polyolefins. A value of the kinetic parameter A may be obtained from these expressions by using an iterative type of procedure and employing data presented by other workers for the oxidation of atactic polybutene‐1. This value of A was compared with the corresponding value obtained by the authors from rate of carbonyl formation studies in oxidation of atactic polybutene‐1 by means of infrared absorption spectroscopy methods. The good agreement between the values of A obtained from the two different experimental techniques employed lends further support to the validity of the scheme used and the expressions derived therefrom.
Analysis of bisphenol A sulfonate–carboxylate polymer
Authors: Forrette John E. , Burroughs James E. , Booker Christine C.
Published: April 2003

The method of analysis for a polycondensation polymer containing the carboxylate and sulfonate functional groups has been devised. A combination of infrared spectroscopy and combustion analysis provides a simple and accurate determination of the monomeric units and their molar distribution in the polymer.
Studies on polymer blends. III. Butadiene–acrylonitrile copolymer and polybutadiene–polyacrylonitrile blend
Authors: Shundo Minoru , Komuro Keiji , Goto Kunio , Imoto Minoru , Minoura Yuji
Published: April 2003

The properties of butadiene–acrylonitrile copolymers were compared with those of polybutadiene–polyacrylonitrile blends. Also, the properties of copolymers having an acrylonitrile unit content of about 30% were compared with those of polymer blends having the same acrylonitrile unit content, i.e., NBR–NBR, polybutadiene–NBR, and polyacrylonitrile–NBR, having different acrylonitrile unit contents. These blends were prepared by roll blending and the vulcanizates were prepared by sulfur cure. The properties of the copolymers were markedly different from those of the blends, that is, in the blends the properties showed a linear relationship with their blending ratios, while in the copolymers the properties showed a curvilinear relationship. In the cases of the polymer blends having a constant acrylonitrile unit content, those blends which were prepared by blending two polymers having similar acrylonitrile unit contents showed better properties than the ones having very different acrylonitrile unit contents.