bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of aging on some anionic initiators
Authors: Ladacki Michael
Published: April 2003

The effects of aging on sodium naphthalene and sodium α‐methylstyrene initiators, prepared in 1957, were investigated. The green sodium naphthalene had turned brown and faded; the aged sample failed to initiate the polymerization of α‐methylstyrene at low temperature. Naphthalene had been completely converted into dihydronaphthalene; the retention of the brown color reflected a relative stability of anions of the latter. The freshly prepared brown sodium‐dihydronaphthalene complex was also ineffective for polymerization of α‐methylstyrene. No evidence for the cleavage of the ether solvent (tetrahydrofuran) on aging was obtained. The aged sodium α‐methylstyrene initiator retained its vivid red color and effectiveness in the polymerization of α‐methylstyrene. The inherent better stability of dianions than of radical anions was thus confirmed. Since the sodium α‐methylstyrene initiator was actually a low molecular weight “living” polymer, the 7‐yr. aging test demonstrated, in effect, the “longevity” of living polymers. The structure of the “living tetramer” of α‐methylstyrene was discussed in the light of previous studies and present results. Apparent discrepancies were pointed out, and the necessity of more comprehensive studies was indicated.
Variable retention of water by dry wood
Authors: Hergt H. F. A. , Christensen G. N.
Published: April 2003

When small wood (or cellulose) samples are vacuum‐dried at room temperature, their final weight is found to vary according to their previous sorption history. The weight variations, of up to 1%, are shown to be due to strongly retained water. A minimum weight is obtained reproducibly (± 0.01%) only when the wood is dried rapidly from the wetted state. When wood thus dried is exposed to water vapor and redried, water is retained even after drying for long periods or at higher temperatures (65°C.) and is removed only by again wetting and redrying the wood. The quantity of water retained is greatest after exposure to relative vapor pressures of approximately 0.5 and increases linearly with the square root of time of exposure up to at least 1000 hr. As some of these phenomena have been reported for the wool–water system also, it is possible that other polymers, particularly those which swell in water, may behave similarly. The significance of these results for the experimental determination of moisture content and the study of water sorption is discussed.
Intramolecular transfer of high energy in cellulose
Authors: Arthur Jett C. , Mares Trinidad
Published: April 2003

The intramolecular transfer of high energy in purified cotton cellulose has been demonstrated to occur over distances several times greater than the length of the b axis of a cellobiose unit. The electron spin resonance spectra of fibrous benzoylated cotton cellulose have shown that the concentrations of free radicals initiated in the cellulosic molecule by γ‐radiation from Co60 are decreased by the presence of substituted benzoyl groups spaced at least as far apart as 70–80 A. The retention of the breaking strength of fibrous cotton cellulose on exposure to γ‐radiation is increased by substitution of benzoyl groups on the cellulose molecule. The substitution of benzoyl groups, spaced at least as far apart as 10–20 A., results in about 80% retention of the initial strength of the fibrous cellulose at dosages as high as 1.3 × 1021 e.v./g. cellulose, as compared with about 20% retention of the initial strength of unsubstituted cellulose at the same dosage. Based on the breaking strengths of the irradiated fibrous celluloses, at a dosage of 1.3 × 1021 e.v./g. cellulose, the average calculated distances between molecular cleavages are increased from about 500 A. for unsubstituted cellulose to about 3000 A. for benzoylated cellulose (degree of substitution 2.0). These energy transfer effects in cellulose of high molecular weight indicate that polymeric carbohydrates can be radioprotected.
Crystallinity of ethylene–vinyl acetate copolymers
Authors: Kamath Pandurang M. , Wakefield Robert W.
Published: April 2003

Determination of crystallinity of ethylene–vinyl acetate copolymers according to the usual x‐ray diffraction method employed for polyethylene is very much hampered by the fact that these copolymers are usually largely amorphous and the Bragg reflections in their diffraction diagrams which are therefore broad and weak are drowned by the strong and dominant amorphous halo. As a consequence it is virtually impossible to carry out a realistic resolution of the total diffraction diagram into the individual Bragg reflections in the halo. In the method described in this paper this difficulty is successfully surmounted by taking advantage of the unique shape and placement of the amorphous halo with respect to the Bragg reflections in the diffraction diagrams of these copolymers. This rather fortunate situation permits a direct determination of amorphous content without having to take recourse to the cumbersome resolution of the Bragg reflections and hence one can obtain crystallinity indirectly.
Effect of zinc oxide concentration on the course of thiuram‐accelerated sulfur vulcanization
Authors: Ducháček Vratislav
Published: April 2003

Tetramethylthiuram disulfide‐accelerated sulfur vulcanization of natural rubber has been investigated. Continuous measurements in a Vuremo curemeter at 145°C were used to estimate the effects of zinc oxide concentration on the induction periods, on the first‐order rate constants, and on the ultimate extents of crosslinking, on the extents of degradation reaction (reversion), and on the extents of relaxation of vulcanizates at the cure temperature. The concentration of zinc oxide has practically no influence on the rate of thiuram‐accelerated sulfur cure. The values of the ultimate extents of crosslinking increase with increasing the zinc oxide content in the rubber compound up to a certain limit corresponding to the theoretical amount of zinc oxide which is necessary for the formation of zinc dimethyldithiocarbamate from tetramethylthiuram disulfide and zinc oxide during the vulcanization reaction. From the point of view of the reversion, however, this limit value of zinc oxide concentration is not sufficient. The relaxation measurements provide the same results. On the basis of these, for thiuram‐accelerated sulfur vulcanizations, the optimum zinc oxide content in the rubber mix of 2.5 phr has been calculated. This value is in very good agreement with the optimum value of zinc oxide concentration found for both sulfenamides and thiazoles‐accelerated sulfur cures.
The effect of competitive adsorption on the rate of diffusion
Authors: Hemming David F. , Collins John D. , Datyner Arved
Published: April 2003

Evidence is presented that the apparent diffusion coefficient of one penetrant can be increased by competition from another penetrant for the same adsorption sites in polyester. The competition is governed by the relative diffusivities of the penetrants and their affinities for the adsorption sites.
Thermal degradation of polymers. XII. Synthesis, polymerization and thermal characterization of polymers of m‐N,N‐dimethylaminostyrene in nitrogen
Authors: Opera S. , Still R. H.
Published: April 2003

The monomer m‐N,N‐dimethylaminostyrene has been synthesized from acetophenone and homopolymerized and copolymerized with styrene, using 2,2′‐azobisisobutyronitrile as free‐radical initiator. The polymers have been characterized by thermal analysis (DTA, DSC, and TG). Glass transition temperatures have been measured and activation energies for degradation in nitrogen have been established by a variety of methods for comparative purposes.
The photochemistry of 1‐benzoyl‐2‐naphthol and 6‐hydroxybenzanthrone and their effect on the rate of photo‐oxidation of polypropylene
Authors: Bentley P. , McKellar J. F.
Published: April 2003

A comparison of the effect of two structurally similar additives, 1‐benzoyl‐2‐naphthol and 6‐hydroxybenzanthrone, on the rate of photo‐oxidation of polypropylene under conditions of simulated daylight shows that while 6‐hydroxybenzanthrone acts as a prodegradant, 1‐benzoyl‐2‐naphthol is a light stabilizer. Examination of the spectroscopic and photochemical properties of 1‐benzoyl‐2‐naphthol indicates that in fluid solution the photoexcited stabilizer is probably deactivated within the singlet manifold. In glassy solvents at 77°K, on the other hand, triplet formation does occur, but only in molecules in which the intermolecular hydrogen bond of the 1‐benzoyl‐2‐naphthol is disrupted.
Effect of four neighboring groups in kinetics of polymer reactions
Authors: Krishnaswami P. , Yadav D. P.
Published: April 2003

Assuming that the rate of reaction of an unreacted site in polymer reactions depends upon whether the two immediate neighboring sites on either side (four neighboring sites in all) are reacted or unreacted, differential equations were obtained giving the rate of change of Nn with time (where Nn is the number of sequences of n consecutive unreacted sites with a reacted site at both ends) and solved numerically with the help of a computer. Nn was obtained as a function of time and also as a function of M, the total number of unreacted sites. Three sets of values of k were tried, one of these relating to autocatalytic reaction, one to autoretarding reaction, and one to the null case in which the reaction rates do not depend upon the neighbors.
Transitions and relaxations of linear polyesters related to poly(ethylene terephthalate). I. Melting
Authors: Yip Harry K. , Williams H. Leverne
Published: April 2003

Observations obtained by other techniques were confirmed by DSC analyses. As the length of the methylene chain increased, Tm decreased, and crystallinity, heat capacity, and heat of fusion increased. The Tm and crystallinity of the isophthalate esters were lower than for the corresponding terephthalate esters. The values for an odd‐numbered methylene sequence were lower than for the adjacent even‐numbered members. A model was used to calculate the heat of fusion of theoretically 100% crystalline poly(hexamethylene isophthalate) and poly(decamethylene isophthalate).
The Tll (>Tg) transition of atactic polystyrene
Authors: Stadnicki S. J. , Gillham J. K. , Boyer R. F.
Published: April 2003

Torsional braid analysis (TBA) (∼0.3 Hz) and differential thermal analysis (DTA) data are presented for the temperature for the region 0–200°C for two series of atactic polystyrenes with narrow molecular weight distributions: (a) anionic series, M̄n = 600–2×106, M̄w/M̄n ≃ 1.1; (b) fractionated thermal series, M̄n = 2,000–1.1×105, M̄w/M̄n < 1.25. Preliminary results on bimodal blends are also reported. Heating and cooling cycles were employed with TBA; only the heating mode was used with DTA. In addition to a dynamic mechanical loss peak at Tg, a higher temperature loss peak was also found. Designated the Tll or liquid–liquid transition (relaxation), its temperature is 1.1 to 1.2 Tg (°K) for polymers with molecular weight below the critical molecular weight (Mc) for chain entanglements. Above Mc ≃ 35,000, it rises steeply, being ≃200°C for M̄n = 110,000. The common dependence of Tg and Tll on M̄n−1 below Mc suggests a common molecular origin. The two facts, (a) that Tll > Tg and (b) that Tll reflects chain entanglements, further suggest that Tll involves a longer chain segment length and possibly the entire molecule. Comparison of Tll versus log M plots with T versus log M isoviscous state plots based on zero‐shear melt viscosity data from the literature implies that Tll measured by the TBA technique corresponds to an isoviscous state of 104–105 poises. The employment of narrow molecular weight polymers is presumably responsible for both the linear variation of the Tll transition with M̄n−1 (which suggests a free volume basis for the relaxation) and the form of the variation of the Tll transition with log M (which suggests an isoviscous basis for the relaxation). The sharpness of the Tll loss peak by TBA decreases with increasing molecular weight and dispersity. The DTA endothermic event corresponding to Tll is clearly related to the occurrence of flow since the fused films which result from heating granules to 200°C and cooling to R.T. do not reveal a Tll on reheating. If a fused film is crushed, a Tll event is observed on heating. For bimodal blends with M̄n < Mc for both components, the Tll transition was averaged; with one component less than and one greater than Mc, the Tll transitions of the components appeared to occur independently at temperatures corresponding to those of the isolated components. In accordance with Ueberreiter and Orthmann, Tg appears to separate a glassy state from a fixed liquid state, whereas Tll separates the fixed liquid from a true liquid state. Possible molecular interpretations for the Tll process are discussed. Systematic bodies of data from the literature which indicate the presence of the Tll process in other polymers are summarized.
Photopolymerization of methyl methacrylate in the presence of saccharide
Authors: Kubota Hitoshi , Ogiwara Yoshitaka , Matsuzaki Kei
Published: April 2003

Photopolymerization of methyl methacrylate (MMA) in aqueous solution of saccharide was investigated. Glucose, cellobiose, maltose, and fructose accelerated the photopolymerization in the hard glass system, but α‐methyl‐d‐glucoside was inactive. On the other hand, on remarkable effect of saccharide except fructose was observed in the quartz glass system. A conversion in the hard glass system increased with irradiation time and with concentration of saccharide, which showed the effect in the order of ketose > aldose > nonreducing saccharide. Scission of glucosidic bonds and decomposition of reducing groups of saccharide molecule took place in the quartz glass system, but there was no reduction in the reducing power of saccharide in the hard glass system. By studying the ESR of the photoirradiated system containing saccharide, MMA, and water, no radical of saccharide was found in hard glass systems, but an increase in growing radical of MMA was clearly observed in systems with the coexistence of ketose and aldose, while α‐methyl‐d‐glucoside was inactive. It is believed, therefore, that both ketose and aldose contribute effectively to initiate the photopolymerization without any change in their own structures. On the other hand, reducing groups of saccharide play a very important role in the sensitizing action of the initiation.
Deuteration of cotton fibers. I. Partially decrystallized celluloses
Authors: Lokhande H. T.
Published: April 2003

Deuteration of cellulose in the fiber form has been studied by the new technique developed recently. Infrared spectra in the 3‐μ region were recorded to obtain four well‐resolved bands due to H‐bonded hydroxyl groups in the ordered regions. The peaks at 3298 and 3400 cm−1 were assigned to cellulose I, while those at 3445 and 3493 cm−1 were assigned to the cellulose II lattice structure. Cotton fibers containing both cellulose I and cellulose II lattice structures (50:50%) gave six bands in the 3‐μ region at 3230, 3298, 3350, 3400, 3445, and 3493 cm−1. Deuteration of swollen and decrystallized cotton fibers revealed that ethylenediamine brings about partial conversion of cellolose I lattice structure to cellulose II lattice structure, giving the characteristic cellulose II band at 3493 cm−1. Swelling mechanism with ethylenediamine to account for formation of cellulose II in cotton fibers has been put forward. Zinc chloride was found to retain the cellulose I structure intact. In both the decrystallized celluloses, the band at 3400 cm−1 has been found to be completely wiped out. This band has been assigned to the group of H bonds mainly lying in rather imperfectly ordered crystalline regions in the fiber structure, which are attacked first during swelling treatment by both the swelling agents irrespective of their different mechanisms of swelling.
Polyimide model compounds
Authors: Hodgkin J. H.
Published: April 2003

Pyromellitic dianhydride was reacted with various substituted aryl amines, under conditions similar to those used for polyimide formation. Yields of model imides have been greatly improved over those found in previous studies. The work has shown that the major impurities formed when the reactions were performed in solutions of N,N‐dimethylformamide or N,N‐dimethylacetamide were adducts containing chemically bound solvent residues.
Electroinitiated polymerization of methyl methacrylate in aqueous sulfuric acid
Authors: Pistoia Gianfranco , Ricci Alessandro , Voso Maria Antonietta
Published: April 2003

The polymerization of methyl methacrylate electroinitiated at the cathode was examined in concentrated solutions of the monomer containing aqueous sulfuric acid. The initiating reaction is not due to the formation of hydrogen atoms, as demonstrated by varying the nature of the cathode and of the acid, but involves the participation of the polymeric peroxide contained in the monomer. The cathodic material greatly affects the molecular weights and the yields, as does the composition of the solutions. Lead cathodes, which proved to be particularly efficient, showed phenomena of adsorption of both monomer and polymer. Kinetic curves are similar to those obtained in conventional radical polymerizations of MMA; a marked gel effect, limiting the termination reaction and leading to very high molecular weights, was observed.
Kinetics of the acid‐catalyzed phenol–formaldehyde reaction
Authors: Malhotra H. C. , Avinash
Published: April 2003

A kinetic study of the reaction of phenol with formaldehyde has been carried out at temperatures of 65° ± 0.05°C, 70° ± 0.05°C, 75° ± 0.05°C, and 80° ± 0.05°C using hydrochloric acid as catalyst. The pH maintained was 1.14, 1.32, 2.20, and 3.00. The reaction follows a second‐order rate law. The rate is found to increase with decrease in pH. The overall rate constants are resolved into step rate constants. The values of the Arrhenius parameters and the entropy of activation for the overall reaction as well as for the step reactions have been calculated. A mechanism conforming to the energies and entropies of activation of the reaction has also been suggested.
Conversion factors in dilatometric data of polymerization reactions
Authors: Adicoff A. , Yee R.
Published: April 2003

Various factors in the conversion of dilatometric data to the extent of polymerization have been considered. These factors are volume additivity, density additivity, difference between the thermal coefficients of monomer and polymer, molecular weight, and degree of crosslinkage. Equations relating the dilatometric readings to the extent of polymerization have been derived. These equations can be used for reactions where the polymerization may be stopped short of complete polymerization. They can also be used for polymerization where the initial portion of the reaction is difficult to record.
Plumbite‐treated cotton in formation of glassy materials
Authors: Ward Truman L. , Benerito Ruth R.
Published: April 2003

Glass‐like materials containing carbon were produced by heating plumbite‐treated cotton fabrics in a limited oxygen atmosphere while in contact with a surface having a high silica content. Although the new materials were changed to a clear glassy state, they retained the design and shape of the fabric weave and were hard, brittle, acid resistant, and alkali resistant. Surface smoothness of the new materials and release from the high silicon‐content materials on which they were made depended on lead content of the plumbite‐treated cotton fabric. High lead contents produced smoother surfaces and better release. This information was applied in producing glass‐like write‐on labels for laboratory glassware or individual flakes of the new material. Direct heat from a Bunsen‐type burner caused the new glass‐like materials to become metallic gold in color without altering other properties. Indirect heat reversed the color to the original. ESCA and x‐ray fluorescence examinations showed the atom ratio of lead to silicon to be 2.5:1 for those made from high lead‐content fabric. Substantial carbon was present in all lead levels.
A model relating the elastic properties of high‐density polyethylene melts to the molecular weight distribution
Authors: Bersted B. H.
Published: April 2003

An earlier model relating the variation of the steady‐shear melt viscosity of high‐density polyethylene to the molecular weight distribution is applied toward predicting the steady‐shear elastic compliance, the first normal stress difference, and relaxation spectrum as a function of shear rate from the molecular weight distribution. The model envisions the cutting off of longer relaxation times as the shear rate is raised such that at any shear rate ${\rm \dot \gamma }$ the molecular weights and their corresponding maximum relaxation times τm are partitioned into two classes; the relaxation times are partitioned into operative and inoperative states, depending on whether they are less than or greater than τc, the maximum relaxation time allowed at ${\rm \dot \gamma }$. Equations relating molecular weight and relaxation time to the steady‐shear elastic compliance and viscosity are assumed valid at nonzero shear rates, except for the partitioning effect of shear rate. The shear rate dependence of the first normal stress difference and the steady‐shear viscosity for polyethylene melts is successfully predicted over the range covered by the cone‐and‐plate viscometer. The assumed proportionality constant between τc and 1/${\rm \dot \gamma }$ was determined to be 1.7. Using this relation, the maximum relaxation time at 190°C for a polyethylene molecule of molecular weight M is given by τm = 1.4 × 10−19 (M)3.33. Reasonable agreement has been obtained between the experimentally determined relaxation spectrum of a polyethylene melt and that predicted from the molecular weight distribution. The agreement is best at the longest relaxation times.
Internal stresses and activation volumes from the stress relaxation behavior of polyethylene at low deformations
Authors: Kubát J. , Rigdahl M. , Seldén R.
Published: April 2003

Internal stress levels and values of the activation volume have been evaluated from the kinetics of stress relaxation in annealed samples of LD and HD polyethylene. The initial deformation of the samples was varied, the maximum values amounting to ca. 1%. The temperature of the experiments was 24°C for LDPE, and 24°, 50°, and 69°C for HDPE. The internal stress level was found to be approximately proportional to the initial deformation and independent of the temperature used. Such internal stresses appear to be introduced upon deformation, since permanent stresses had been removed by careful annealing. The activation volume (v) was found to satisfy the relation vσ* ≈ 10kT, where σ* is the effective stress, i.e., the difference between the applied and internal stress, k is Boltzmann's constant, and T is the absolute temperature. This is in good agreement with results reported elsewhere for a wide variety of materials. This relation applies primarily to the exponential flow portion of the relaxation curves, but by a simple transformation the power‐law region can also be encompassed.
Synthesis of high molecular weight polyacrylamide flocculant by radiation polymerization
Authors: Wada Takeshi , Sekiya Hiroshi , Machi Sueo
Published: April 2003

The radiation‐induced polymerization of acrylamide was studied to prepare a high molecular weight and highly effective polyacrylamide flocculant. Among various solvents, mixtures of water–tert‐butyl alcohol and water–acetone were found to be suitable for the synthesis of the high molecular weight polyacrylamide. For polymerization in acetone–water mixtures, the molecular weight of polymer increases with monomer concentration; but at the high concentration, intermolecular imidation of amide groups tends to take place during the polymerization to from crosslinked and water‐insoluble polymer. The water‐soluble polymer with the largest molecular weight of 6.7 × 106 is produced in the polymerization with monomer concentration of 2.91 moles/1. at 0°C at a dose rate of 6.2 × 102 rad/hr in acetone–water mixture containing 60 vol‐% water. The crosslinking of polymer of the formation of water‐insoluble polymer could be avoided by the addition of K2CO3 or NaOH to raise the pH of the reaction mixture above 6.5. The flocculation effects were evaluated from sedimentation speed of kaolin suspension and transparency of the separated water. The sedimentation speed is proportional to the intrissic viscosity of the polymer in the range of 4 to 23 dl/g. The polymers prepared in this study show much higher sedimentation speed than commercial polyacrylamide flocculants. The transparency of the separated water is higher than 93%, similar to the results with commercial flocculants.
Analysis of the types and amounts of carbonyl species present in oxidized polyethylene
Authors: Benham John V. , Pullukat Thomas J.
Published: April 2003

The carbonyl species present in oxidized polyethylene are qualitatively and quantitatively determined through the use of infrared measurements on the polymer. The method described makes use of a carbon monoxide/ethylene copolymer wedge in the reference beam of the infrared spectro photometer to compensate the large 1720 cm−1 ketone absorbance. This allows one to observe the 1710 cm−1 and 1735 cm−1 carbonyl absorbances as distinct peaks rather than as shoulders on the 1720 cm−1 peak. This is a significant advantage over other published infrared methods for this analysis. The absorbances obtained at 1710 cm−1 and 1735 −1 are then used in an equation to calculate the absorbance at 1720 cm−1 due to ketonic carbonyl only. Our results confirm Cooper and Prober's assignment of both the 1710 cm−1 and 1735 cm−1 absorbances in the infrared spectra of oxidized polyethylene to acid functionality. Our quantitative results are comparable to those reported by Cooper and Prober, and our method represents a significant reduction in the time required for the analysis (1.5 hr vs. ∼45 days). The carbonyl distribution in a commercially oxidized polyethylene wax was determined as being ∼11.0 ketone CO/2000 C and ∼21.7 acid CO/2000 C (with a σ of 1.8 CO/2000 C and 3.0 CO/2000, respectively). A high‐density polyethylene, oxidized with air in the laboratory, contained ∼1.91 ketone CO/2000 C and 2.19 acid CO/2000 C (with a σ of 0.08 CO/2000 C and 0.16 CO/2000 C, respectively).
Thermal behavior of cotton grafted with vinyl monomers individually and in mixture compositions
Authors: Sharma V. N. , Daruwalla E. H.
Published: April 2003

Thermal analysis of cotton samples grafted with acrylamide, acrylonitrile, methyl acrylate, and methyl methacrylate individually and in mixture compositions has been carried out. Additional endothermic peaks in the DTA curves characteristic of the polymers grafted were observed. Graft copolymerization of acrylamide and acrylonitrile makes cotton thermally more stable, while in the case of methyl acrylate‐and methyl methacrylate‐grafted cottons, the initial decomposition starts at higher temperatures, but subsequent decomposition is faster and the overall thermal stability is lowered. In the case of binary mixtures of acrylamide and acrylonitrile, inception of decomposition starts earlier, but subsequent decomposition takes place at much higher temperatures than for individual monomer‐grafted cottons. Interaction between monomers during grafting is indicated. When fabric samples containing polyacrylamide grafts are methylolated and subsequently cross‐linked, there is a reduction in the thermal stability of the treated cotton.
Thermomechanical studies of semicrystalline polyether–ester copolymers. Effect of thermal, mechanical, and solvent treatment
Authors: Kalfoglou Nikos K.
Published: April 2003

The thermomechanical spectra of a series of elastoplastic polyether–ester copolymers were determined at 110 Hz and between −120°C and 200°C at five compositions. Emphasis was given to samples containing an increasing amount of poly(tetramethylene terephthalate) constituting the hard segment in these copolymers. The effects of thermal history, uniaxial drawing, and solvent absorption were examined. Specimens cut from injection‐molded slabs were also included in the study. Thermal and mechanical treatment had an important effect on the dynamic mechanical properties. The relaxation spectra do not indicate distinct phase separation, but rather a structure of closely interacting hard and soft segments. The molecular origin of the various relaxations was characterized, and it is shown that as the amount of the hard component increases, features in the relaxation spectrum characteristic of poly(tetramethylene terephthalate) become prominent.
Diffusion of radioactively tagged penetrants through rubbery polymers. II. Dependence on molecular length of penetrant
Authors: Rhee Chong‐Kon , Ferry John D. , Fetters L. J.
Published: April 2003

The diffusion of radioactively tagged n‐hexadecane, n‐dotriacontane, and a polybutadiene oligomer with molecular weight 1600 has been studied in 12 rubbery polymers. Diffusion coefficients were obtained from the theory for the thin smear method: for n‐hexadecane and for n‐dotriacontane (with one exception), in the form appropriate for a completely miscible polymer–penetrant pair, and for the oligomer in the form appropriate for slow entry of the penetrant across the penetrant–polymer interface. For the four flexible linear penetrants, n‐dodecane, n‐hexadecane, n‐dotriacontane, and oligomer, the ratios of diffusion coefficients (or translational friction coefficients) are nearly the same in every polymer. It is concluded that these penetrants travel with similar segmentwise motions, although that is not the case with bulkier, more rigid penetrants. For the three normal paraffins, the friction coefficient is approximately proportional to molecular weight, but that for the oligomer is smaller than would be predicted on this basis.
A gel permeation chromatography calibration method for a broad molecular weight distribution polymer
Authors: Mahabadi H. K. , O'Driscoll K. F.
Published: April 2003

A novel, precise, and simple method is described for developing a GPC calibration curve for a polymer where only broad molecular weight distribution samples are available. The method demands a GPC calibration curve for another polymer (e.g., polystyrene) and measurement of the intrinsic viscosity and an average molecular weight for each of several samples of the broad molecular weight distribution polymer in addition to GPC measurements on those samples. Results of applying the procedure to poly(n‐lauryl methacrylate) are presented.
Polyurethane interpenetrating polymer networks. V. Engineering properties of polyurethane–poly(methyl methacrylate) IPN's
Authors: Kim S. C. , Klempner D. , Frisch K. C. , Frisch H. L.
Published: April 2003

The engineering properties of polyurethane–poly(methyl methacrylate) simultaneous interpenetrating networks (SIN's) were evaluated. The hardness behavior reflected the observed phase inversion in the electron‐microscopic studies. The maximum ultimate tensile strength was observed at 85% polyurethane–15% poly(methyl methacrylate) IPN and was due to the filler‐reinforcing effect of the rigid poly(methyl methacrylate) phase. The ultimate tensile strenght of the 75/25 polyurethane–poly(methyl methacrylate) IPN was higher than that of the corresponding pseudo‐IPN's (only one network crosslinked) and the linear blend. The leathery and glassy compositions did not show any reinforcement in the ultimate tensile strength. This indicated that the reinforcement in the ultimate tensile strength was not directly related to interpenetration (by increased physical entanglement crosslinks), but indirectly related by reducing the rigid phase domain sizes and increasing the adhesion between the two phases, thus enhancing the filler‐reinforcing effect similar to that observed in a carbon black‐filled rubber. The tear strengths of the polyurethane‐rich IPN's pseudo‐IPN's, and linear blends were found to be higher than that of the pure polyurethane as a combined result of increased modulus and tensile strength. The weight retentions in the thermal decomposition of the IPN's, pseudo‐IPN's, and linear blends were higher than the proportional average of the component networks. The results seemed to indicate that this enhancement was related to the presence of the unzipped methyl methacrylate monomer. It was suggested that the monomers acted as radical scavengers in the polyurethane degradation, thus delaying the further reaction of the polyurethane radicals into volatile amines, isocyanates, alcohols, olefins, and carbon dioxide.
Calibration and molecular weight calculations in GPC using a new practical method for dispersion correction—GPCV2
Authors: Yau W. W. , Stoklosa H. J. , Bly D. D.
Published: April 2003

The method of Balke, Hamielec, LeClair, and Pearce for GPC calibration and molecular weight computation is reviewed and evaluated. A new method, called GPCV2, is proposed which uses the single broad molecular weight distribution (MWD) standard for calibration developed by those workers, but which also incorporates the chromatographic dispersion σ to make the method more accurate in general use. Equations are presented for computing the relationship between actual MW and retention volume VR under the chromatographically broadened curves. This relationship is then compared to those obtained by using the Balke et al. method and the peak position method.
Studies on soluble fraction of glow‐discharge polysilazane formed from hexamethylcyclotrisilazane
Authors: Gazicki M. , Wróbel A. M. , Kryszewski M.
Published: April 2003

The soluble part of glow discharge polysilazane prepared from hexamethylcyclotrisilazane was studied. The composition of the soluble fraction was examined by gas chromatography and mass spectrometry. It was found that the fraction contained five main components, and two of them, identified by mass spectrometry, were octamethylcyclotetrasilazane and bicyclic silazane dimer. A reaction mechanism leading to dimer formation from hexamethylcyclotrisilazane in glow discharge was proposed.
Melt‐spinning dynamics and rheological properties of nylon 6
Authors: Bankar Vilas G. , Spruiell Joseph E. , White James L.
Published: April 2003

Basic studies of the melt‐spinning dynamics and rheological properties of a nylon 6 polymer are described. The magnitude of the force components on the spinline has been analyzed with special reference to the drag and rheological forces. Spinline deformation has been investigated for spinning through ambient air and through an isothermal chamber. Both sets of experiments are interpreted using an elongational viscosity. Non‐Newtonian viscosity was measured at 230°, 250°, and 270°C in a Weissenberg rheogoniometer and an Instron capillary rheometer. The principal normal stress difference was measured in the former instrument. The rheological properties are interpreted in terms of the theory of viscoelastic fluid behavior. The isothermal melt‐spinning experiments were also interpreted in terms of the theory of viscoelastic fluids, and attempts were made to understand the spinning results in terms of basic rheological properties.
Thermo‐optical analysis of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/triblock styrene–butadiene–styrene copolymer blends
Authors: Shultz A. R. , Beach B. M.
Published: April 2003

Blending of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO resin) with a triblock butadiene–styrene–butadiene copolymer (Kraton 101) monotonically increases the softening temperature of the latter as measured by TOA. The TOA transition temperatures of the styrene/PPO resin phases closely approximate those of polystyrene/PPO resin blends having the same styrene/aromatic ether unit compositions. Uniform mixtures of the styrene blocks with the poly(2,6‐dimethyl‐1,4‐phenylene oxide) molecules is inferred.
Use of auger and x‐ray photoelectron spectroscopy to study the locus of failure of structural adhesive joints
Authors: Gettings M. , Baker F. S. , Kinloch A. J.
Published: April 2003

The techniques of Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS) have been used to study the locus of failure of epoxy resin joints. The effects of a long water immersion and the application of a silane‐based primer have also been studied. Results indicated that for dry joints fracture occurred near an epoxy resin/metal interface while with water‐soaked unprimed joints, fracture occurred interfacially between the adhesive and iron oxide. The application of the primer to the metal surface prior to bonding prevented the formation of a water‐formed oxide although fracture was then found to occur through the primer.
The dielectric behavior of the natural resin manila copal
Authors: Goswami Dipendra N. , Bhattacharya Promode R.
Published: April 2003

The dielectric relaxation data of the natural resin Manila copal, obtained by Bhattacharya,1 has been analyzed by the Cole–Cole method at temperatures from 30° to 150°C. Two distinct relaxation processes were found for temperatures of 70°, 80°, and 90°C as opposed to only one as observed by Bhattacharya.1 The relaxation at 100°C and at higher temperatures could be represented by the typical Cole–Cole patterns. The variation by temperature of the static dielectric constant (ε0) exhibited three distinct slopes, which indicated the different phases of the resin during thermal transformation. Two “transformation points”, around 70° and 100°C, were found instead of only one at 105°C as observed by Bhattacharya.1 The static dielectric constant, the dielectric increment, the Cole–Cole distribution parameter, and the relaxation time decreased markedly owing to the increase of temperature from 100° to 150°C. These indicated some changes in conformation of the resin molecules during transition from the solid to the liquid state.
A kinetic and surface study of the thermal decomposition of cellulose powder in inert and oxidizing atmospheres
Authors: Fairbridge C. , Ross R. A. , Sood S. P.
Published: April 2003

The thermal decomposition of fibrous cellulose powder from 275° to 340°C has been studied by thermogravimetry, scanning electron microscopy, krypton adsorption, and gas‐chromatographic analysis of the gaseous products arising from pyrolysis in various oxidizing and inert atmospheres. The reaction kinetics fit a phase boundary model where the rate is controlled by the movement of an interface through a cylindrical particle and the principal kinetic parameters fit a compensation curve described previously for the decomposition of wood products. An explanation of the physical mechanism of pyrolysis is proposed which is consistent with the observed rate data and the structural changes observed by scanning electron microscopy.
Application of instrumented impact test in polymer testing
Authors: Radon J. C.
Published: April 2003

Advanced methods of conducting and analyzing instrumented Charpy impact tests are described and used in measuring the initiation fracture toughness K1c at a range of impact velocities and temperatures. Improvements developed in the impact testing of metals are discussed and applied in the toughness evaluation of polymers. In lower‐speed impact tests where load–displacement records are nearly linear, the maximum recorded load may be used to evaluate K1c by stress analysis K calibration formula. In high‐speed impact tests, where the load trace is highly oscillatory, the fracture load to be used in the calculation must be derived indirectly. The indirect derivation of fracture load for this purpose from a “low blow” stiffness measurement and specimen deflection has been studied in detail, and the use of the periodic time of the “low blow” test has been found to offer a reliable method of calculating the system stiffness.
Polyimides from diisocyanates, dianhydrides, and their dialkyl esters
Authors: Alvino William M. , Edelman Leonard E.
Published: April 2003

High molecular weight polyimide polymers have been prepared by the reaction of dissocyanates and a mixture of dianhydrides and their dialkyl esters in aprotic solvents. No catalyst is necessary, but high polymer formation is affected by the anhydride/ester ratio and temperature. Dianhydrides such as PMDA, BTDA, TMA, and their esters have been used successfully. Mixtures of these materials have also been used. Tough, flexible films can be obtained from these polymers.
X‐ray diffraction orientation studies on blown polyethylene films. I. Preliminary measurements
Authors: Maddams W. F. , Preedy J. E.
Published: April 2003

X‐Ray diffraction pole figure measurements have been made on six films blown from high‐density polyethylene. Five were prepared on an experimental unit; the sixth, blown on commercial equipment, had a higher degree of overall orientation thus enabling more extensive results for the a‐, b‐, and c‐axis distributions to be obtained. The results provide information on the orientation present, how it may be related to the stress crystallization process of Keller and Machin, and the dependence of the tear strengths in the machine and transverse directions on the orientation. The typical behavior, with the a and c axes at 90° and both at an angle to the plane of the film, is shown to be the result of a composite process involving several types of stress during the blowing operation and a partial relaxation arising at one or possibly two stages of the process. The predicted relative tear strengths, obtained from the concentration of c axes inclined towards the machine direction, are in line with the experimental values. There is some evidence that transcrystallization in the surface layers of the films may lead to a better balance of the tear strengths in the machine and transverse directions.
Limits of the chemical composition heterogeneity of random copolymers
Authors: Stejskal Jaroslav , Kratochvíl Pavel
Published: April 2003

One of the characteristic features of copolymers is their chemical heterogeneity. Examples are given of the dependence of conversion heterogeneity in the chemical composition of random copolymers on the initial composition of the monomer mixture, along with typical examples of the differential distribution functions of chemical composition. The maximum attainable values of the conversion heterogeneity parameter have been calculated depending on the copolymerization parameters. The conditions are discussed under which copolymers may acquire chemical heterogeneities high enough to be perceived or determined by fractionation or light scattering. Limits are estimated beyond which the chemical heterogeneity becomes undetectably low and the copolymers can be regarded as chemically homogeneous.
A study on distension index and distribution of crosslinks in formaldehyde‐crosslinked cotton
Authors: Pandey S. N. , Nair Prema
Published: April 2003

A study on distension index (DI) and distribution of crosslinks is reported for cotton cellulose treated with selected swelling reagents and crosslinked by different processes with formaldehyde. Details of estimation of the distension index are also described. Distribution of crosslinks under different conditions of crosslinking has also been shown by electron microscopy. Marked differences in DI values and distribution of crosslinks in cellulose samples crosslinked under different conditions of treatments are discussed. The results of these analysis provide quantitative information on the gross uniformity of distribution of crosslinkages in the fiber structure of cotton celluloses.
Photodegradation of polypropylene in the presence of ferric chloride
Authors: Negishi Akio , Ogiwara Yoshitaka , Osawa Zenjiro
Published: April 2003

The effect of ferric chloride (FeCl3) on photodegradation of isotactic polypropylene (PP) was investigated using mainly ESR spectrometry. PP powder, its oxidized samples, and FeCl3‐adsorbing PP samples were irradiated under a nitrogen atmosphere at 77°K with ultraviolet light from a high‐pressure mercury lamp and a superhigh‐pressure mercury lamp modified by various filters. Methyl, polymerci alkyl, and peroxy radicals were observed in the ESR spectra of the irradiated samples, and it was found that FeCl3 depresses the formation of alkyl radicals and accelerates the formation of peroxy radicals catalyzing the reaction. From infrared study of UV‐irradiated film samples, it was also inferred that FeCl3 accelerates the photodegradation the hydroperoxide and carbonyl groups.
Hercosett‐57 resin deposition on wool and modified wools
Authors: Asquith R. S. , Gardner K. L. , McGarel W. S. , Otterburn M. S.
Published: April 2003

A study has been made of the uptake of a commercial polyaminoamide resin (Hercosett‐57) by wool fibers. The effect of various chemical pretreatments on the uptake of the resin was monitored in order to investigate the mechanism of bonding of the polymer with the wool. From the results obtained it would appear that the deposition of the resin is not controlled by simple chemical reaction with the fiber. Surface treatments to the wool fibers and adhesion play a more important part in the resin‐bonding process. Insoluble chlorinating agents such as DCCA and Chloramine T proved more effective in bringing about resin deposition than did the more widely used acid chlorination treatments, which use free chlorine in solution.
Radical formation and graft copolymerization on photo‐irradiated aldehyde cellulose
Authors: Ogiwara Yoshitaka , Hayase Koji , Kubota Hitoshi
Published: April 2003

The relationship between the activity to initiate graft copolymerization under photo‐irradiation and the photo‐induced radicals of periodic acid‐oxidized cellulose (aldehyde cellulose) was investigated. Aldehyde cellulose proved to have a high activity to initiate graft copolymerization under photo‐irradiation, and the effect was profound, especially for hydrophilic vinyl monomers such as acrylic acid and acrylamide. By studying the ESR spectrum of photo‐irradiated aldehyde cellulose, the formation of a radical giving a singlet spectrum with linewidth of 14–15 G and a g value of 2.001 was observed. This was assigned to an acyl radical orginating in the aldehyde group of the sample. Employing low molecular weight aldehydes, it was confirmed that an acyl radical formed on aldehyde compounds by photo‐irradiation has a function sufficient to initiate the graft copolymerization of vinyl monomers. It was concluded that the high activity needed to induce the graft copolymerization of aldehyde cellulose under photo‐irradiation was based on an acyl radical which originated in the aldehyde group of the sample.
Reverse osmosis separations of polyethylene glycols in dilute aqueous solutions using porous cellulose acetate membranes
Authors: Hsieh Fu‐Hung , Matsuura Takeshi , Sourirajan S.
Published: April 2003

Reverse osmosis separations of eight polyethylene glycol (PEG) solutes in the average molecular weight range of 200 to 6750 in single‐solute dilute aqueous solutions have been studied using porous cellulose acetate membranes at the operating pressures of 50, 75, and 100 psig. Diffusivity data for the above PEG solutes have also been obtained from experimental data on intrinsic viscosities. From an analysis of all experimental data, numerical values for the parameters representing the polar (−ΔΔG/RT), steric (δ*ΣEs), and nonpolar (ω*Σs*) forces governing reverse osmosis separations of PEG solutes have been generated. These numerical values are useful for precise characterization of cellulose acetate membranes for whose specifications sodium chloride is not the appropriate reference solute because of its low or practically negligible separation under reverse osmosis operating conditions. This work also illustrates that solute separation in reverse osmosis can predictably increase or decrease with increase in operating pressure depending on experimental conditions.