bluuebunny/crossref_metadata_2025 huggingface dataset:
Aminobutadienes. XII. A method for modification of polypropylene fiber by graft copolymerization with 1‐phthalimido‐1,3‐butadiene by thermal mastication
Authors: Terada Akira
Published: April 2003

The high reactivity of 1‐phthalimido‐1,3‐butadiene for either homopolymerization or copolymerization was applied to prepare a graft copolymer with isotactic polypropylene using a roll mill. Five reaction systems containing the monomer 0, 1, 3, 5 and 10% in polypropylene were allowed to react at 175°C. under atmospheric pressure for 10 min. to give the graft copolymers. The resulting resin, tough and rigid, was melt‐spun to give a single filament. This filament was extracted with 1,2‐dichloroethane to remove the remaining monomer and homopolymer. The percentage of the grafted monomer against the feed was determined by ultraviolet spectroscopy. This modified method did not result in gel formation or decreased viscosity. Accordingly, spinning could be easily carried out. After fivefold stretching of the filament in hot water of 95°C., the tensile strength was almost identical to that of a sample obtained from the original polypropylene. However, a considerable decrease in elongation was observed. The filament can be dyed uniformly with some basic dyes at a rate proportional to the imidobutadiene contents. After hydrazinolysis, the filament acts as an anion‐exchange fiber and imbibes acid dyes homogeneously throughout.
Intrinsic viscosity of polymer solutions at high shear rates
Authors: Ram A. , Siegman A.
Published: April 2003

Although low‐shear intrinsic viscosity is a well‐accepted tool for polymer characterization, it often happens (particularly with increasing molecular weights) that it is easier to detect the high‐shear (second) Newtonian viscosity η2 rather than its low shear counterpart. It has also been predicted that because of a higher degree of order, due to disentanglement and orientation, high‐shear viscosity data should simplify the prevailing correlations. The possibility of using high‐shear viscometric data for polymer characterization was examined by determining intrinsic viscosities for several polyisobutylene samples through extrapolation of the high‐shear ultimate viscosity numbers, UVN, to zero concentration: [η]2 = lim UVNC → 0 = limC → 0 (η2–ηs)/ηsC where ηs is the viscosity of the pure solvent. Five samples of unfractionated polyisobutylene (molecular weights of 1.1 × 106–6.6 × 106) in toluene, kerosene, decalin, and gas oil at concentrations of 0.05–2.4 g./dl. were studied. Higher dilution was avoided because of the problem of onset of turbulence. The absence of shear degradation was ascertained by measuring low‐shear intrinsic viscosity data before and after the polymer was exposed to high‐shear conditions. The data show two types of behavior: for the lower molecular weight samples in the low‐viscosity solvents the UVN decreases linearly with dilution, and for the higher molecular weights and higher solvent viscosities the UVN increases with high dilution, i.e., shows an upturn effect. The first type of data can be successfully correlated with appropriate molecular weights by using a typical Mark‐Houwink equation. The exponents in these relationships are in the range of 0.28–0.64, increasing systematically with decrease of solvent viscosity and independent of the “goodness” of the latter. The data that show an upturn effect are not currently amenable to reliable extrapolation techniques. The upturn, however, predicts the conformation of very flexible, isolated polymer chains in viscous solvents under conditions of high shear.
Location of some typical vinyl polymers within radiation‐grafted cotton fibers: An electron microscopical survey
Authors: Rollins M. L. , Cannizzaro A. M. , Blouin F. A. , Arthur J. C.
Published: April 2003

Electron microscopical observations of radiation‐induced rayon–styrene graft copolymers were published by Kaeppner and Huang in 1965. The present paper reports electron microscopical investigations on the relationship of the structure of vinyl–cotton graft polymers to the original morphology of the cotton fiber and into the distribution of the grafted vinyl polymer in the cotton fiber structure. The grafted vinyl monomers investigated in this study were acrylonitrile, styrene, methyl methacrylate, and vinyl acetate. Two radiation‐induced procedures were used: simultaneous irradiation grafting and post‐irradiation grafting. Ceric ion grafting of acrylonitrile to cotton was included for purposes of comparison. Distribution of the vinyl polymer within the cotton fiber is illustrated by a series of electron micrographs, selected as typical of the particular grafted species under consideration. Results indicate that the diffusion rate of monomer into the cellulose fiber plays an important role in the final distribution of polyacrylonitrile grafts within the fiber. Uniform distribution of polyacrylonitrile in the fiber was achieved by simultaneous irradiation grafting of acrylonitrile on a highly substituted cyanoethylated cotton. In samples of low degree of cyanoethylation the distribution of graft polymer was non‐uniform. In grafting initiated by ceric ion the acrylonitrile graft polymer was evenly distributed. Polystyrene–cotton copolymers from grafts, made by simultaneous irradiation of cotton in methanol solutions of the styrene monomer, were uniform throughout the fiber but showed opening of structure associated with the amount of graft formed. Grafting of methyl methacrylate occurred only in the peripheral regions of the fiber; by contrast, grafting of vinyl acetate was uniform throughout the fiber wall. Important factors governing the successful irradiation grafting in cotton fibers are choice of solvent, ratio of monomer to cellulose, nature of prior chemical modification of the cellulose, and total irradiation dosage.
Some thiol‐terminated polyethers
Authors: Arnold H. B. , Floyd D. E.
Published: April 2003

Thiol‐terminated polyethers were prepared by two different routes, the starting materials being commercially available polyether polyols and epoxy resins. The products were pale colored liquids and were found to be very stable on storage at room temperature. Thiol‐terminated polyethers of functionality from 2 to 4 were prepared. They are interesting building blocks for polymers through oxidation of the terminal SH groups or through coreaction with epoxy resins.
Microscopic determination of degree of nitration of nitrocellulose with dispersion staining
Authors: Kohlbeck J. A. , Bolleter W. T.
Published: April 2003

A microscopical method with dispersion staining has been developed for determining the degree of nitration of nitrocellulose (NC). In the method the per cent nitrogen in unknown samples is obtained by matching the colors of dispersed refracted light between an oil of known refractive index and films of the unknown and an NC standard. Agreement with standard Du Pont Nitrometer results were excellent. Color differences were detected as the nitrogen content of the NC ranged between 12.55 and 13.5% with central screening and the polarizer. The sensitivity was found to be increased by crossing the analyzer with the polarizer and observing the phase differences resolved in the analyzer.
Effect of acid acceptor concentration on the interfacial polycondensation of nylon 610
Authors: Kispert Robert C. , Foote Seward R. , Griskey Richard G.
Published: April 2003

The effect of acid acceptor level (sodium hydroxide) in the interfacial polycondensation of nylon 610 has been studied. It was found that increased acceptor levels shifted the curves of intrinsic viscosity versus sebacoyl chloride concentration to the right. It was also found that peak intrinsic viscosity values first decreased and then increased with increasing acid acceptor levels. The experimental results were shown to relate to balance of reactants and character of polycondensation zone.
Imidazole catalysis in the curing of epoxy resins
Authors: Farkas Adalbert , Strohm Paul F.
Published: April 2003

The high catalytic activity of imidazoles and particularly of 2‐ethyl‐4‐methylimidazole (EMI) for the curing of epoxy resins and the properties of the resulting resins prompted this study concerned with the nature of the curing reaction. Epon 828 epoxy resin and the model compound phenyl glycidyl ether were used as starting materials with EMI, 2‐methylimidazole, and dimethylbenzylamine as catalysts. During the curing of the resin at 50°C., the decrease in the infrared absorption of the epoxy band with time is accompanied by a decrease in the intensity of the imine band of the imidazole moiety, indicating its reaction with the epoxy group and its incorporation into the resin. The measurement of the residual epoxy content after curing for 24 hr. at 50 and 140°C. showed that the imidazoles were not more efficient in completing the epoxy reaction than dimethylbenzylamine. In the experiments with phenyl glycidyl ether the rate of reaction of the epoxy group with EMI was faster than the rate of polymerization, proving that the imidazole becomes permanently attached to the polymer chain. These results also suggest that the true catalytic species is not EMI but some addition product thereof. In comparative rate measurements the compound formed from equimolar quantities of EMI and phenyl glycidyl ether was found to be an excellent catalyst. The NMR analysis of the 1:1 and 1:2 adducts of EMI and phenyl glycidyl ether has shown that the second mole of phenyl glycidyl ether reacts with the ring nitrogen in the 3 position and not with the hydroxyl group of the mono adduct. By forming the bis adduct in this way the imidazole molecule acts as a crosslinking agent and at the same time introduces an alkoxide ion which can initiate further polymerization. It is very likely that this crosslinking is the process that leads to the superior physical and chemical properties (high heat deflection temperature, resistance to chemicals and oxidation) of the resins prepared with imidazoles as catalysts.
N‐methylaniline formaldehyde: Its synthesis and use as an epoxy curing agent
Authors: Bilow Norman
Published: April 2003

A series of poly‐secondary aromatic amines was prepared by the acid‐catalyzed condensation of N‐methylaniline with formaldehyde. These condensation products were evaluated as curing agents for a standard epoxy prepolymer, namely bis(2,3‐epoxypropoxyphenyl)propane. Various molar ratios of N‐methylaniline to formaldehyde were used to produce polyamine condensation products with varying degrees of polymerization. These molar ratios ranged from 1.60 to 1.30. Dielectric properties of the cured epoxy resins at temperatures above 100°C. were highly dependent upon these ratios. Lower‐ratio condensation products produced resins with optimum dielectric properties at the higher temperature and also with good physical properties.
Calendering thermoplastic materials
Authors: Chong J. S.
Published: April 2003

A general equation for the true shear rate encountered in calendering non‐Newtonian fluids is derived. Based on several constitutive equations (for a power‐law, a three‐constant Oldroyd, and a modified second‐order Rivlin‐Ericksen fluid), calendering is analyzed from the hydrodynamic point of view. The significance of dimensionless groups (the Deborah number, the Weisenberg numbers, and the viscoelastic ratio number), consisting of rheological and kinematic parameters, is discussed for scaling from prototype to production calendering. Correlation of experimental data obtained by using laboratory and production calenders is presented, and the scaling criteria obtained from the theory are examined. The onset of unstable flow, which causes non‐uniform internal strain patterns (nerve) in calendered sheeting, is discussed in terms of the Weisenberg number. Good and poor calendering regions for a polymer are discussed qualitatively by using a dynamic response diagram, and the importance of the overall calendering conditions on the final sheeting quality is discussed.
Anomalous freezing point depression of swollen gels
Authors: Boonstra B. B. , Heckman F. A. , Taylor G. L.
Published: April 2003

The anomalous freezing point depression, ΔT, of benzene‐swollen vulcanizates has previously been attributed to the limitation of (benzene) crystallite size by the polymer network. This study was initiated to determine the benzene crystallite size in a number of rubber and benzene systems. A special low‐temperature specimen holder was designed and constructed in the Cambridge Laboratories for running diffraction patterns at temperatures near −30°C. X‐ray line broadening techniques were used to study a series of filled and unfilled vulcanizates of varying crosslink density. The results indicate that crystallite size is not depressed to the degree predicted by freezing‐point measurements. Benzene crystallite sizes were similar in all rubber benzene systems, regardless of degree of crosslinking or benzene fraction, although carbon black loading appears to increase crystallite size. This effect may be attributed to lesser depth of penetration of the x‐rays due to greater density as carbon black loading increases. Additional studies measuring the ΔT for solutions and similar vulcanizates of NR and SBR over a wide range of rubber concentrations showed that at the same rubber in benzene fraction, crosslinking increases ΔT but the addition of carbon black reduces ΔT. An explanation for the observed phenomena is advanced.
Studies of the water‐soluble polymers. XVI. Azo dyes of poly‐N‐vinylimidazole
Authors: Machida Seishi , Araki Mikio , Matsuo Keizo
Published: April 2003

Homopolymer of 2‐methyl‐N‐vinylimidazole and copolymer of the monomer with acrylamide were coupled with some aromatic diazonium compounds to give polymeric azo dyes. The dyestuff prepared from the homopolymer was soluble in water only when it was coupled with diazonium component containing sulfonic acid group, but the dyestuffs prepared from the copolymer were soluble. The reactivity, chemical structure, color, and dyeability of the polymeric dyes are discussed by comparing them with those of the corresponding monomeric dyes. The color fastness of the polymeric dyes was found to be in a high class; the rubbing and dry‐cleaning fastness were especially excellent.
The connection number of polymers with particular reference to carbon polymers
Authors: Holliday L.
Published: April 2003

The use of a connection number is proposed for the simple topological analysis of random networks. This is illustrated with some carbon polymers.
Fine structure of cellophane–acrylamide graft copolymer by the ceric ion method
Authors: Hori Yasuhiko , Takahashi Toru , Nagata Masanori , Sato Ichiro , Okamura Seizo
Published: April 2003

The relationship between the grafting yield and the structure of graft copolymer is studied by measuring the branched chain lengths, the number of branches, the crystallinities, and the diffraction intensities of the (101) and (101) + (002) planes determined by x‐ray diffraction, and the distribution of branched polymers, observed by interferometry. Over a relatively wide range of grafting yield the number of initiating sites is almost constant and about 1–2 per 2 moles of cellulose chain. Therefore, the increase of grafting yield seems to be due mainly to the propagation of branched polymers. Branched polymers are assumed to be formed in cellulose crystallites both on the normal (101) planes and in the amorphous regions of cellulose. It is found that branched polymers grow from the outer layer into the inner part of the film as the grafting yield increases. At more than 250% of grafting yield, however, branched polymers are uniformly formed throughout the layer of film in which the crystalline regions of cellulose are gradually destroyed. This result agrees with the dimensional change of gel film during the reaction. The temperature dependence of tensile strength and elongation and the wet strength of graft copolymer are also investigated. At higher grafting yields, such as 250%, the crystalline structure of cellulose is disturbed by the formation of branched polymer, and no improvement in waterproofness can be expected from grafting; the secondary bonding between branched polymers may be presumed to be same as those among cellulose. In addition, the fine cracking of the film in the burst state is found to appear more easily as the grafting yield increases, in which the aggregating state of cellulose is recognized to be changed by the formation of branched polymer.
Correlation of capillary entrance pressure drops with normal stress data
Authors: La Nieve H. L. , Bogue D. C.
Published: April 2003

The pressure loss at the entrance of a capillary tube was studied as a means of characterizing viscoelastic fluids. Measurements of four polymer solutions were made and correlated with an equation of the form

where D is the shear rate and where Hch and λch are a characteristic stress and a characteristic time, respectively, determined independently from viscosity and normal stress measurements. Various theoretical analyses of capillary entrance flow are also compared.
Diffusion during the coagulation step of wet‐spinning
Authors: Paul D. R.
Published: April 2003

The coagulation of viscous polymer solutions by diffusional interchange with a liquid bath is the key step to fiber formation by wet‐spinning. Model experiments were performed on gelled solutions of an acrylic polymer in dimethylacetamide, to determine the mass‐transfer rates of solvent and nonsolvent (water) during coagulation, the rate of movement of a boundary associated with coagulation, and the final equilibrium between the coagulated phase and the bath. Each is given as a function of bath composition and temperature. The data are analyzed by means of various diffusion models, one of them giving quite good agreement. The data and the models are used in conjunction with each other for the elucidation of the mechanism of the processes involved in coagulation.
Cure of polyester resins. I
Authors: Learmonth G. S. , Tomlinson F. M. , Czerski J.
Published: April 2003

The application of physical test methods to studying the crosslinking of unsaturated polyesters is reviewed. Experimental work on changes of hardness and electrical resistivity is described and it is shown that these are not mutually related, due to continual mobility of ionic conditions after the resin network is immobilized by gelation.
Studies on the stretching of polypropylene film. II. Polyaxial stretching
Authors: Okajima Saburo , Homma Keisuke
Published: April 2003

Polypropylene film was stretched polyaxially at 100–160°C., and the orientation behavior was studied by means of optical and x‐ray method. The molecular chains oriented progressively to the film surface with an increase in stretching area vA in the range 1–16, and the (040) selective uniplanar orientation developed at the extreme stretching. The plot of orientation versus vA was less steep when the stretching was carried out at higher temperature, but the final degree of orientation was independent of the temperature, because the final vA increased with temperature. At 160°C. premelting occured to such a degree that the high stretching and, consequently, the high orientation could not be obtained. The orientation of the amorphous chains was always behind that of the crystalline region. In the initial stage the polyaxial stretching was not as effective in attaining high biaxial orientation as the two‐step biaxial stretching, but the final orientation was the same in both types of stretching because vA reached a value of 16 in the polyaxial stretching while it was only 2 in biaxial stretching.
Studies in the reactivities of isocyanates
Authors: Ghatge N. D. , Yadav S. D. , Ranade A. C.
Published: April 2003

Disubstituted monoisocyanates were synthesized and their reactivities studied by the spectroscopic method.
Cohesive energy density of polytetrahydrofuran
Authors: Huglin M. B. , Pass D. J.
Published: April 2003

Measurements have been conducted on radiation‐crosslinked polytetrahydrofuran (PTHF) of stress‐strain and of swelling coefficients in simple esters. For the linear polymer, measurements have been made of density and intrinsic viscosities in the esters. [η] was also determined under the θ conditions of 33.5°C. in diethyl malonate. The results have been incorporated into several (sometimes interdependent) approaches towards the evaluation of the solubility parameter δp of PTHF. The mean of the nine values obtained is 8.55 (cal./cc.)1/2, whence the cohesive energy density is 5.17 kcal./mole. Seventeen experimental values of the Flory interaction parameter χ are also reported.
Elution column fractionation of branched polyethylene
Authors: Traskos R. T. , Schneider N. S. , Hoffman A. S.
Published: April 2003

In a systematic study of the elution column fractionation of a well characterized branched polyethylene sample it was found that one of the most important factors contributing to the efficiency was the composition selected for the p‐xylene‐butyl cellosolve eluting mixture. With a mixture representing the critical solvent composition at 126°C., as determined by cloud point measurements, and deposition to an amorphous phase on a fine sand support, viscosity–distribution curves were obtained which were highly reproducible and completely free of any reversal. No further improvement was gained by using an elution temperature other than 126°C. or by the substitution of tetralin or mesitylene for p‐xylene. Precipitation down a temperature gradient to produce a physical separation of species provided enhanced fractionation but is of doubtful practical interest. Fractionation was readily scaled up from 2g. to 4 or 6g., merely by increasing the mixing vessel size from 500 cc. to 1000 cc. There was no loss of efficiency, and fractions with M̄w = 8 × 106, more than twentyfold higher than the sample value, were obtained despite eluted polymer concentrations exceeding 0.2%. There is evidence that many of the expected differences in the fractionation behavior of linear and branched polyethylene are erased when a solvent mixture is used which has been adjusted to the appropriate critical composition.
Effects of molecular weight and strain rate on the flexural properties of polycarbonate
Authors: Golden J. H. , Hammant B. L. , Hazell E. A.
Published: April 2003

The effects of changes in molecular weight (7000 to 22,000) and strain rate (0.0001 to 4 min.−1) on the flexural properties of polycarbonate have been examined in detail with the use of speciments of different molecular weight prepared by high‐energy electron irradiation. The results have been plotted as surfaces which show the dependence of both stress and strain on molecular weight and strain rate, and these surfaces have been described in terms of brittle, transitional, and ductile regions. The relationships between stress or strain and molecular weight in the brittle region have been shown to be hyperbolic. A single failure locus has been found to include all the corresponding stress and strain data obtained at the various molecular weights and strain rates. In the low strength region this locus exhibits a proportionality between stress and strain, while at high strength values, strain becomes a logarithmic function of stress. Stress–molecular weight data obtained at the various rates have been superimposed to form a single composite curve, and the corresponding crossplots of stress–log rate have been treated similarly. It is concluded from these superpositions that an equivalence exists between changes in both molecular weight and strain rate such that a tenfold change in strain rate corresponds approximately to a change of 1000 in molecular weight. Strain‐strain rate data obtained at the various molecular weights have also been superimposed in a similar manner. Modulus is shown to increase slowly with decrease in molecular weight and appears to be relatively insensitive to changes in strain rate.
Examination of the temperature coefficient of polystyrene. Effect of solvent, temperature, and molecular weight
Authors: Cerny L. C. , James H. , Stasiw D. , Willcox H.
Published: April 2003

The temperature coefficient of polystyrene was examined in three θ solvents by several different methods. Four homogeneous samples were employed, having molecular weights of 51,000, 97,200, 160,000, and 392,000. It was found that the linear expansion factor α and the temperature coefficient were dependent upon the solvent, temperature range and molecular weight of the polymer.
Dynamic mechanical behavior of a polyimide
Authors: Bernier G. A. , Kline D. E.
Published: April 2003

The dynamic mechanical properties of a polyimide (poly‐4,4′‐oxydiphenylene pyromellitimide) were studied from about 4 to 800°K. at audio frequencies. A prominent relaxation associated with absorbed water content occurs near 230°K. Below 270°K., the modulus undergoes a corresponding increase in value with increasing water content. Above 550°K. the onset of a major relaxation process is observed in the modulus data, and a maximum in the internal friction is observed at about 675°K. Minor relaxation peaks are also noted throughout the temperature range. Relatively minor differences are noted in the mechanical relaxation spectra for the polyimide when treated (after drying) with dimethylformamide, dimethylacetamide, and dimethylsulfoxide, whereas the treatment with water after drying has a marked effect on the relaxation behavior. A reactor radiation dose of 3000 Mrad also causes only minor alterations in the dynamic mechanical spectra.
Cure of polyester resins. II
Authors: Learmonth G. S. , Pritchard G. , Reinhardt J.
Published: April 2003

The copolymerization reaction between unsaturated polyesters and styrene has been studied by a torsional pendulum. The accuracy of the dynamic‐mechanical measurements obtained is discussed briefly, and the results are compared with those of previous work on the change of hardness during cure.
Relation between nylon fiber mechanical properties and dye diffusion behavior
Authors: Bell James P.
Published: April 2003

The mobility of polymer chain segments is shown to play a major role in the diffusion of dyes in nylon 66. The rate of dye diffusion has been related to the time‐dependent mechanical properties, such as creep and stress relaxation, which are controlled by the mobility of the chain segments. The theoretical relations derived by Fujita et al. relating the diffusion of small molecules in amorphous polymers to other properties are shown to be applicable for the dyeing of semicrystalline nylon. Data showing the effects of surface area, temperature, and the amount of dye absorbed at saturation on the dyeing rate are presented and discussed.
The mechanism of oxidative degradation of ABS resin. Part I. The mechanism of thermooxidative degradation
Authors: Shimada Junichi , Kabuki Kimiaki
Published: April 2003

In this work the early stages of the thermal oxidation of ABS resin films for commercial utilization and purified samples were studied by means of infrared spectroscopy. The film samples were submitted to thermal oxidation in a Gear oven at 70–90°C. During the aging in the Gear oven the nitrile and phenyl absorbance did not change, but oxidative products containing hydroxyl or carbonyl groups were produced rapidly, and the butadiene content decreased gradually. Two parts of the oxidative reaction were easily distinguished by analysis of the degradation procedure in the differential method and in the half‐time method. An activation energy of 10 kcal./mole or less was obtained for the initiation process, involving mainly the formation of hydroperoxides induced by radical formation, which was apparent in the commercial samples, whereas a value of 10–20 kcal./mole was obtained for the subsequent process, initiated by the decomposition of the hydroperoxides, which induces chain‐carrier reactions. A reaction scheme is proposed, and kinetic expressions are developed therefrom. These expressions explain the experimental results very well.
The mechanism of oxidative degradation of ABS resin. Part II. The mechanism of photooxidative degradation
Authors: Shimada Junichi , Kabuki Kimiaki
Published: April 2003

The mechanism of oxidative degradation of ABS resin under ultraviolet irradiation, especially with respect to the wavelength dependencies of the photooxidative rate, has been examined by a spectroweather tester and infrared spectroscopy. The irradiation wave region was 290–800 mμ, and the region was divided into six parts. The changes in each part were examined by infrared spectroscopy. The absorption bands belonging to nitrile and phenyl groups showed no changes, but bands belonging to carbonyl and hydroxyl groups changed markedly, much as in the thermooxidative degradation described in a previous paper. There was a distinct gap between the third and fourth regions, which corresponded to 350 mμ. The graph of the normalized absorbance ratio and the logarithm of the wavelength gave a straight line, and it indicated that the rate of oxidation is proportional to the light intensity and the logarithm of the wavenumber.
Reversible crosslinks in cotton modified with N‐hydroxymethylacetylthioacetamide
Authors: Tesoro G. C. , Sello S. B. , Willard J. J.
Published: April 2003

The reaction of cotton fabric with N‐hydroxymethylacetylthioacetamide (HOCH2‐NHCOCH2SCOCH3) yields acetylthioacetamidomethylcellulose, which can be saponified under mild conditions to the corresponding thiol derivative, mercaptoacetamidomethylcellulose. Some reactions of the thiol group are discussed, including oxidation to disulfide, repeated reduction‐oxidation cycles, and blocking with alkyl halides. Chemical methods were used in establishing the occurrence and extent of the predicted reactions and their dependence on specific variables in the system. Changes in the crease recovery and tensile strength of the cotton derivative obtained in the reactions were found to be qualitatively consistent with the expected structures. The results of this work show that crosslinks can be obtained reversibly in cotton by this sequence of reactions. Intervening side reactions produce a gradual decrease in the yield of the desired products, however, as the number of cycles increases. Mercaptoacetamidomethylcellulose provides a limited but useful model for the investigation of reversible crosslinks in cellulose.
Epoxy resins from dinaphthols
Authors: Burnop V. C. E.
Published: April 2003

Epoxy resins were prepared from di‐α‐naphthol(4,4′‐dihydroxy‐1,1′‐dinaphthyl) and di‐β‐naphthol(2,2′‐dihydroxy‐1,1′‐dinaphthyl). The resins consisted mainly of the reaction product of 1 mole of dinaphthol with 2 moles of epichlorhydrin. They contained chlorine, however, and were correspondingly deficient in diepoxide functionality. The resins from di‐α‐naphthol were crystalline, had m.p. 200°C., and were not miscible with conventional curing agents. Di‐β‐naphthol gave resins with softening points in the range 50–70°C., which cured with diethylenetriamine or the anhydrides of dibasic acids, giving hard but brittle products. The brittleness was not removed by curing with plasticizing curing agents, such as tetrapropenyl succinic anhydride. The cured di‐β‐naphthol‐based resins had thermal stabilities similar to analogous epoxy resins based on bisphenol A.
The effect of strain rate on the stress–strain curve of oriented polymers. I. Presentation of experimental results
Authors: Hall I. H.
Published: April 2003

The stress‐strain curves of viscose, nylon 6.6, poly(ethylene terephthalate), polyacrylonitrile, and polypropylene have been determined at a large number of different strain rates between 10−4 and 330 sec.−1. The shape of these stress‐strain curves and its change with strain rate is shown to depend upon whether the material is tested above or below its glass temperature. The stress‐strain curves of materials tested below their glass temperature consists of an initial straight portion followed by a yield point at a few per cent strain. The breaking strain is only slightly affected by strain rate, and the energy to rupture increases with increasing rate. For materials tested above their glass temperature the initial portion of the stress‐strain curves in nonlinear, and the yield strain is much higher than for the other materials. There is a small range of strain rate, in which the breaking strain falls sharply to the yield strain with increasing rate, and the energy to rupture also decreases. Outside this range the energy to rupture increases with increasing rate.
Adiabatic compressibility of polyelectrolytes in aqueous solutions: Poly(methacrylic acid)
Authors: Roy‐Chowdhury Phanibhusan
Published: April 2003

The adiabatic compressibility of dilute aqueous solutions of methacrylic acid, poly‐(methacrylic acid), and three poly(sodium methacrylates) obtained by neutralizing the polyacid with sodium hydroxide to different extents were determined from soundvelocity and density data. The ultrasonic velocity at 25°C. was measured by employing a precision ultrasonic interferometer, and the density was measured with Ostwald‐type pycnometers. The plots of the decrease of compressibility per unit concentration, (β1 − β)/c versus c shows that there is a marked difference between the curves of monomer and of polymer solutions. In case of the monomer there is a proportional decrease with increase in concentration, whereas in polymer in the dilute region (0.1−0.5g./dl.) the curve rises sharply, then shows down, and finally approaches a constant value at comparatively higher concentrations. The nature and number of the free counterions and the shape and the concentration of the polymer molecules are responsible for the compressibility of polymer solutions. However, the contribution of the size and shape and concentration of the polymer seem to be less than that of the nature and number of the counterions. The apparent molal volume ΦV2 and apparent molal compressibility ΦK2 for polymer repeat units show a sharp decrease with increase in concentration and finally attain a constant value at higher concentrations; this has been explained by the fact that in the dilute region the polymer, being extended by coulombic repulsion between similar charges situated on the side chain, enhances the formation of water clusters around it, and the free counterions are solvated, leading to a decrease to these values. The number of free counterions proportionately increases with concentration, causing a proportional decrease of the ΦV2 and ΦK2 values, until the concentration reaches a definite stage, above which the so‐called condensation of ions occurs, and the number of free counterions does not increase further at higher concentrations.
Hysteresis and strength of rubbers
Authors: Harwood J. A. C. , Payne A. R.
Published: April 2003

A criterion of tensile failure in terms of energy density and energy loss at break has been developed for several gum rubbers over a wide range of test temperature. A similar description of failure in filled rubbers is related to the gum criterion by a simple elastic interaction term. The upper and lower limits of the failure equation are considered in detail, and the relationships of energy density at break with temperature and ultimate strain are also discussed.
Flow properties of polyethylene melt
Authors: Kataoka Tadao , Ueda Shigeyuki
Published: April 2003

Flow properties for low‐density and high‐density polyethylene over a broad range of shear stress are described. Flow equations presented in literatures are tested from the point of view of the extrapolating method for evaluating the zero shear viscosity. It is shown that the method based on the equation of Cross gives relatively good results. The recoverable shear strain calculated from the capillary end correction is practically equal to that determined from the creep experiment at the same shear stress. The effect of shear stress on the elastic property is examined.
Epoxy polymers. III. Factors affecting the cure
Authors: Cuthrell R. E.
Published: April 2003

The rate of cure of epoxy polymers appears to be diffusion‐controlled, and after gelation is dependent upon the capillary dimensions in a floccular matrix. The floccule dimensions and packing determine the size of the interfloccular capillaries and are inversely related to the cure temperature. The degree of cure is inversely related to the pregelation cure temperature (thermal history, including preheat) and directly related to the total cure time.
Studies on polymer blends. II. Butadiene–styrene copolymers and polybutadiene–polystyrene blends
Authors: Shundo Minoru , Hidaka Takashi , Goto Kunio , Imoto Minoru , Minoura Yuji
Published: April 2003

The properties of butadiene–styrene copolymers and of polybutadiene–polystyrene blends were compared. Polybutadiene, polystyrene, and four copolymers having styrene contents of 20, 40, 60, and 80% were prepared. The copolymers were compared with blends having various styrene contents and prepared by means of latex blending and roll blending. Vulcanizates were prepared by three different curing methods, i.e., sulfur cure, peroxide cure, and radiation cure. The results of the benzene extraction of three vulcanizates showed that the polystyrene blended was not cured by any of the curing methods used. The properties of the vulcanizates of the copolymers were markedly different from those of the blends, i.e., in the case of the blends the properties showed a linear relationship with their blending ratio, while in the copolymers the properties showed a curvilinear relationship which had an inflection point at a styrene content of about 60%. From this phenomenon of the copolymers, it was proposed that the second‐order transition point of styrene is the cause of the properties showing this peculiar point. From the results, it was found that the behavior of styrene in copolymers is essentially different from that in blends.
Controllably crazed polystyrene: Morphology and permeability
Authors: Michaels Alan S. , Bixler Harris J. , Hopfenberg Harold B.
Published: April 2003

The effects of n‐heptane and heat treatment on the structural and transport properties of polystyrene films (biaxially oriented and unoriented) were studied to determine whether these treatments improve the film as selective barriers for separation of molecules differing only slightly in size and shape. n‐Heptane treatment of biaxially oriented polystyrene produces a sandwich structure composed of expanded, crazed, surface layers surrounding an apparently unaffected central core. The crazed layers contain a continuous network of interconnected channels. The core provides the total resistance to gas permeation, hence, the overall effect of n‐heptane treatment is fabrication of a thinner more permeable membrane. By restricting the stress‐cracking treatment to one face of the film, it should be possible to make high flux, anisotropic membranes—a type of membrane which is required for successful development of membrane separation processes. n‐Heptane treatment of cast, annealed polystyrene results also in a crazed polymer, but the crazing is in the form of spherical voids, and the films, even with a residual uncrazed core, are too weak to be useful as separation membranes. The crazing process in both types of polymer specimens is characteristic of case II non‐Fickian diffusion in which the kinetics are apparently controlled by polymer relaxation processes. Sorption of isopentane into cast, annealed polystyrene does not cause visible crazing but the kinetics are again non‐Fickian. Desorption of isopentane into n‐heptane‐treated polystyrene releases the appreciable residual n‐heptane in the film which could not be removed by long‐term exposure to vacuum. Analysis of D(0) values for isopentane in n‐heptane treated films indicates that the polymer surrounding the visible voids in the film is essentially unaltered polystyrene with only a small fraction of the voids being interconnected by open channels.
Creep behavior of polyethylene melts
Authors: Kataoka Tadao
Published: April 2003

Creep behavior of branched polyethylene melts with various molecular weight distributions are examined experimentally. The order of the steady‐state compliance is in accord with the prediction from the molecular weight distribution. The shear rate dependence of viscosity and steady‐state compliance are analyzed according to Pao's theory.
Sorption and diffusion in asymmetric membranes
Authors: Sternberg S. , Rogers C. E.
Published: April 2003

Polyethylene membranes with nearly linear gradients of grafted poly(vinyl acetate) from one surface to the other have been prepared by radiation‐initiated polymerization of sorbed vinyl acetate monomer. Transport of methanol through the modified membrane proceeds at different rates, depending on the direction of flow relative to the gradient of grafted PVAc. A mathematical model has been derived, which gives a quantitative description of the directional transport process. The relationship can be used to predict the transport behavior for single penetrants through asymmetric membranes from knowledge of the properties of the individual components.
Modification of butadiene–acrylonitrile and styrene–acrylonitrile copolymerizations in emulsion systems
Authors: Uraneck C. A. , Burleigh J. E.
Published: April 2003

Modification of acrylonitrile in copolymerizations with butadiene and with styrene in hot and cold emulsion recipes has been studied. Series of primary, secondary, and tertiary mercaptans in addition to several miscellaneous modifiers were tested. Kinetically the rate data for the monomer pairs containing acrylonitrile better fit first‐order plots than the curves obtained for an ideal emulsion polymerization. In this study all modifier depletions in nitrile systems were plotted as log mercaptan versus log conversion and the slope of the curve was taken as the transfer constant. Normal mercaptans were inefficient modifiers in nitrile systems as determined in polymerization and depletion experiments. Secondary mercaptans, 2‐nonyl, 2‐decyl, and mixtures in this molecular weight range, were promising modifiers for low temperature (5°C.) nitrile systems. 2‐Nonyl mercaptan gave enhanced modification by incremental addition of the modifier indicating this procedure could be used to advantage in preparing nitrile rubbers. The series of tertiary mercaptans from C13 to C7 showed an improvement in modification of low temperature nitrile systems as the molecular weight decreased. A plot of the data on a molar basis shows that the optimum modifier falls in the C9–C8 range. The optimum transfer constant for the most efficient modification of 70/30 and of 80/20 butadiene–acrylonitrile polymerizations at 5°C. terminated at 60% conversion is 2. Depletion data show that the transfer constant for a mercaptan decreases as the nitrile content in mixtures with butadiene increases. The properties of the vulcanizates of the 70/30 and 80/20 butadiene–acrylonitrile polymers prepared in the presence of low molecular weight mercaptans were equivalent to or better than those of the controls. These data show that nitrile polymers could be modified with a lower molecule weight mercaptan with no loss of properties but with a considerable saving in amount of modifier. Mercaptans are essential for the initiation of butadiene–acrylonitrile in the presence of persulfate at 50°C. For the hot nitrile rubber preparations, the series of mercaptan from t‐C10 to t‐C7 are efficient modifiers. However, the heptyl and octyl mercaptans are retarders, and the t‐C9 and t‐C10 are the preferred modifiers for efficiency and unretarded polymerization. The modification with a series of mercaptans ranging from t‐C13.2 to t‐C8 of 75/25 styreneacrylonitrile at 50°C. in presence of persulfate–bisulfite showed a consistent behavior. The transfer constant decreased in a regular manner as the molecular weight of the mercaptan increased, and for the series of tertiary modifiers the t‐C10 mercaptan was the most efficient as judged by a melt flow test.
Aluminum reinforcement of some polyethylenes
Authors: Böhme R. D.
Published: April 2003

Filler reinforcement by aluminum powder was correlated to filler–matrix adhesion and was found to be a simple exponential function of the volume fraction for a series of polyethylenes.
Influence of molecular weight on some properties of poly(vinyl chloride)
Authors: Pezzin Giovanni , Zinelli Giuseppe
Published: April 2003

Several fractions obtained from a large‐scale fractionation and several unfractionated PVC polymers and blends have been processed both as rigid and plasticized compounds. The latter have been studied by stress–strain, creep, and recovery tests. The recoverable character of the creep results show that a relatively stable network must be present in the samples. The crosslink density is little influenced by molecular weight, as shown by the modulus and compliance results. On the contrary, the ultimate tensile properties depend strongly on molecular weight, which is interpreted as evidence that the stability of the crosslinks increases with increasing chain length of the polymers.
Thermal degradation studies of several pyrrone films
Authors: Jewell Robert A.
Published: April 2003

The thermal degradation of several polyimidazopyrrolone (pyrrone) films was studied in air and in vacuum over the range of 100–1000°C. by thermogravimetric analysis (TGA), with the use of both isothermal heating and programmed heating rates of 2, 3, 5, and 7.5°C./min. At pressures of 10−6 torr or less, maximum weight losses average 30% at 800°C. Rates of volatilization and activation energies were derived to provide comparison between these ladder‐type polymers. Mass spectrometric analysis of the pyrolysis gases evolved under vacuum conditions showed that CO, CO2, and H2O were the primary volatile products and that they were formed throughout the period of weight loss. Approximate correlation between changes in weight and changes in the total pressure for the vacuum tests indicates that mass spectrometric results could provide quantitative as well as qualitative data. The importance of sample history prior to heating and of sample geometry in developing meaningful and reproducible TGA results is aptly demonstrated. The ability of these materials to absorb readily 5–7 wt.‐% of water under ambient conditions and the effect of this property upon weight loss measurements are shown.
Single specimen determination of Young's and bulk moduli
Authors: Warfield Robert W. , Cuevas Joseph E. , Barnet F. Robert
Published: April 2003

A new method is presented for the rapid and consecutive determination of the Young's and bulk moduli of polymeric materials. Usually these properties are determined by separate measurements. However, by using an undersized specimen in a standard compressibility device it has been found possible consecutively to determine both moduli on the same specimen in a single test procedure. The initial loading of the undersized specimen results in a decrease in length and an increased diameter. From these changes Young's modulus may be calculated. Once the bore of the tester is filled, the application of additional pressure results in a decrease in the volume of the polymer, from which the bulk modulus may be calculated. Both of these determinations may be made within minutes, and the values of the moduli are in agreement with published values.