bluuebunny/crossref_metadata_2025 huggingface dataset:
Branching by copolymerization of monovinyl and divinyl monomers in continuous‐flow stirred reactors
Authors: Strate G. Ver , Cozewith C. , Graessley W. W.
Published: April 2003

The effect on molecular weight distribution of copolymerization with divinyl monomers, which leads to branch points in an otherwise linear polymer, is calculated for a continuous‐flow stirred reactor. It is found that steady state operation of the reactor becomes impossible at a degree of branching equal to only half that which causes gellation in a batch reactor. In steady state operation the ratio of weight to number average degree of polymerization cannot exceed 7, this ratio being 2 in the absence of branching. The classical result that the fraction of mers coupled at the gel point is 1/(D̄Pw)o, where (D̄Pw)o is the weight‐average degree of polymerization without branching, does not apply in a CFSR at any steady state conversion. Such deviations appear in batch reactions only when gelation occurs at high conversions.
Shear degradation of poly(vinyl acetate) in toluene solutions by high‐speed stirring
Authors: Agarwal S. H. , Porter Roger S.
Published: April 2003

A poly(vinyl acetate) (PVAc) of M̄w 750,000 and M̄w/M̄n 5.10 in toluene solution was sheared in a Virtis‐60 homogenizer. The polymer concentration was 3.0 to 12.0 g/100ml, and test temperature was 10 ± 0.5°C. The extent of degradation was measured by gel permeation chromatography (GPC). It was concluded that on shearing (i) the molecular weight decreases rapidly at the beginning of shearing and thereafter decreases ever more slowly toward a limiting value, (ii) the molecular weight distribution is narrowed, (iii) no degradation occurs up to 5000 rpm and thereafter increases with stirring speed, (iv) degradation is more at lower concentrations but concentration is not a sensitive variable, and (v) the chain scission occurs randomly. The Mark‐Houwing relationship for PVAc in THF at 25°C was derived as [η] = 2.47 × 10−4 × M̄v0.644.
Pyrolysis and combustion of cellulose. VII. Thermal analysis of the phosphorylation of cellulose and model carbohydrates during pyrolsis in the presence of aromatic phosphates and phosphoramides
Authors: Langley J. T. , Drews M. J. , Barker R. H.
Published: April 2003

Thermal gravimetric analysis, differential scanning calorimetry, and derivative thermal gravimetric analysis were utilized to characterize the thermal interactions between cellulose, 1‐6, anhydro β‐D‐glucopyranoside, and D‐glucose and model phosphate and phosphoramide flame retardants. The phosphoramides induced higher char yields than the phosphates during the pyrolysis of the mixtures of carbohydrates and organophosphorus compounds. Exothermic reactions attributed to phosphorylation and char formation were observed with each of the phosphoramide/carbohydrate mixtures and were absent with the phosphates. The individual phosphorus compounds studied showed similar thermal behavior with each of the carbohydrates indicating that the mode of interaction for these mixtures was similar. Isothermal gravimetric analysis of the organophosphorus/carbohydrate mixtures was used to measure the rate of decomposition weight loss from isothermal conditions. This weight loss was used as an indication of rate of fuel formation. The kinetics observed for these measurements indicated that the phosphoramide mixtures underwent a rapid weight loss to a final char with an effective Eact of about 55 kcal/mol while the phosphate mixtures exhibited effective Eact′s for decomposition lower than those observed for the pure carbohydrates. Mixtures of glucose with selcted arylphosphoramide esters were pyrolysed in order to determine the effect of lability of the leaving group on char formation. Gas chromatographic analysis of the pyrolysis products indicated that phenol was the favored leaving group in comparison with aniline units, but char promotion appeared to be dependent on the number of P‐N bonds present in the original phosphoramide. Electron spectroscopy for chemical analysis indicated that chemically similar chars were obtained from the different organophosphorus/carbohydrate combinations.
Radiation‐induced graft copolymerization of methyl methacrylate on natural and modified wool. V. Crystalline and morphological structure
Authors: Varma D. S. , Sadhir R. K.
Published: April 2003

X‐ray diffraction patterns of the α‐ and β‐crystalline phases of natural, chemically modified, and MMA‐grafted wool fibers were investigated. In the grafted fibers variation of the equatorial and meridional scattering intensity during the α–β transformation was inhibited. This indicated that the grafting had stabilized the structure to the α–β transformation. The average crystallite size was found to increase with the extent of grafting, and the degree of orientation appeared to decrease with percent graft‐on. SEM studies revealed little damage to the surface topography of wool fibers after chemical treatments. Graft copolymerization with MMA made the fiber surface regular and smooth, mainly because of deposition of polymer in the escarpment, thus reducing the sharpness of the scaly structure. Scanning electron micrographs of the peeled‐off surface and cross sections of the grafted fibers indicated that a significant amount of polymer was deposited in the medullae of the fibers.
Shear flow rheological properties, fiber damage, and mastication characteristics of aramid‐, glass‐, and cellulose‐fiber‐reinforced polystyrene melts
Authors: Czarnecki Lech , White James L.
Published: April 2003

An experimental study of the viscosity and principal normal stress difference of a polystyrene melt filled with aramid (Kevlar), glass, and cellulose fibers is reported. The influence of loading level and mastication on the rheological properties is discussed. The effects of mixing and mastication on fiber damage are considered. Glass fibers break down rapidly to very small aspect ratios, while aramid shows a “kinked” structure, with kinks occurring every 100 μm. A mechanism is proposed for fiber breakage based on buckling during rotation in shear flow. It is found that addition of fibers increases the viscosity in the same manner as a reduction in temperature, and data may be superposed by reduced plotting. This indicates that the viscosity increase is due solely to enhanced viscous dissipation in the matrix and not to interparticle forces as is the case with smaller particles. The principal normal stress difference increases at fixed shear stress with fiber loading. The extent of increase depends upon fiber loading, aspect ratio, and modulus.
Polymerization from the vapor phase. I. Poly(p‐phenyleneterephthalamide) gas barrier coatings
Authors: Ikeda R. M. , Angelo R. J. , Boettcher F. P. , Blomberg R. N. , Samuels M. R.
Published: April 2003

An atmospheric‐pressure, vapor‐phase polymerization technique was used to deposit thin(1–10 μm) poly(p‐phenyleneterephthalamide) coatings onto polyester film and other sheet substrates. A minimum deposition temperature of 170°C, was found to be critical. When substrate temperatures were below 170°C, coatings were loosely adhered, powdery, and of low molecular weight; above 170°C, coherent, well‐adhered, high molecular weight coatings were obtained. These vapor‐deposited coatings exhibited exceptionally good oxygen barrier properties and were found to consist of fused 0.1‐μm particulates. Scanning electron microscopy (SEM) of the top surfaces of these coatings clearly revealed their particulate origin. Similar evidence was also obtained from SEM examination of fracture surfaces and transmission electron microscopy of microtomed sections. The coalescence of these coatings was demonstrated by SEM of plasma‐etched surfaces and oxygen permeability information. The uniplanar orientation of the polymer crystals in these multiparticulate coatings was strong evidence for the epitaxial growth of the crystals.
Relation between intrinsic viscosity and molecular weight
Authors: Quackenbos H. M.
Published: April 2003

The connection between intrinsic viscosity and number‐average and weight‐average molecular weight has been revealed by calculations from distribution curves. Log‐normal distributions, and moderate variations thereon, were chosen as typical for polystyrene and other thermoplastics. Intrinsic viscosity and number‐average molecular weight are unlikely to be related because of the highly disturbing effect of small variations in molecular weight distribution. Conversely, intrinsic viscosity is a good practical measure of weight‐average molecular weight up to a ratio of 10 for weight‐to‐number average.
Improvement of flame‐retardant properties of insulated wires by radiation crosslinking
Authors: Hagiwara Miyuki , Sohara Masayoshi , Araki Kunio , Kagiya Tsutomu
Published: April 2003

Electric wires coated with polyethylene insulation crosslinked by a chemical method (gel fraction = 80%) and a jacket of self‐extinguishing resin were produced. The jacket was crosslinked by irradiation with γ rays or accelerated electrons. Flame retardant properties of the wire improved by γ‐ray induced crosslinking up to ∼60% gel fraction in the jacket. Beyond this point, however, the flame resistance rapidly decreased with increasing gel fraction. The flame resistance was also improved by irradiation with electrons, but the extent of the improvement was strongly dependent on the energy of incident electrons. This fact was attributed to the difference in the distribution of energy dissipation, i.e., crosslinks formed in the jacket. By introducing a double layer structure to the jacket, in which the inner layer adjacent to the polyethylene insulation was crosslinked more densely than the outer layer, the wires were markedly improved in resistance to flame and heat deformation.
Tensile properties and morphology of blends of polyethylene and polypropylene
Authors: Lovinger Andrew J. , Williams M. L.
Published: April 2003

The tensile behavior of blends of linear polyethylene (PE) and isotactic polypropylene (PP) was examined in relation to their morphology. Yield stress increases monotonically with increasing PP content, while true ultimate strength is much lower in all blends than in the pure polymers as a result of early fracture. The blends fail at low elongation because of their two‐phase structure, consisting of interpenetrating networks or of islands of PE in a PP matrix, as shown by scanning electron microscopy of fracture surfaces and transmission electron microscopy of thin films. While spherulites in PP are very large (∼100 μm in diameter), addition of 10% or more of PE drastically reduces their average size. This, together with the profusion of intercrystalline links introduced by PE, may be associated with maximization of tensile modulus in blends containing ∼80% PP. Introduction of special nucleating agents to PP reduces average spherulite size and is accompanied by slight improvements in modulus. Thin films of blends strained in the electron microscope neck and fibrillate in their PE regions, but fracture cleanly with little fibrillation in areas of PP.
Quantitative analysis of polymer blends using breadths of overlapping x‐ray diffraction lines
Authors: Chidambareswaran P. K. , Sreenivasan S. , Patil N. B. , Sundaram V.
Published: April 2003

A method is developed to estimate the composition of a powder mixture using breadths of over‐lapping x‐ray diffraction (XRD) lines. The application of the method is illustrated for analyzing blends of cotton and jute.
Graft copolymerization of styrene onto cellulose acetate p‐nitrobenzoate by chain transfer reaction
Authors: Nakamura Shigeo , Yoshikawa Eimei , Matsuzaki Kei
Published: April 2003

Styrene was grafted onto cellulose acetate p‐nitrobenzoate (CANB) by chain transfer reaction of growing polymer radicals to the pendant nitro groups of CANB. A copolymer with a branch for every 17.2 nitro groups was obtained. This result indicates that the pendant aromatic nitro group is more effective in obtaining a graft copolymer by radical mechanism than pendant double bond on the trunk polymer previously reported, where graft copolymers with a branch for several hundred of double bonds are produced.
Rheological and mechanical properties of polyurethane modified by BHET
Authors: Lin Chen‐Chong , Yang Bin‐Zw
Published: April 2003

The chemical structure of polyurethane modified by BHET is correlated with its mechanical and dynamic mechanical properties. Evaluation of this amorphous elastomer by means of stress–strain tests and transition temperature measurements reveals that incorporation of the BHET structure into the soft polyester segment affects the domain structure and, in turn, the entire mechanical behavior of polyurethane. It is also shown that polyurethane has a wide range of Tg and secondary transition temperature by varying the ratio of BHET to EG as well as the ratio of TDI to polyester polyol.
Crosslinking of partially neutralized carboxyl‐terminated liquid rubbers with bisepoxide and anhydride
Authors: Matsuda Hideaki
Published: April 2003

Crosslinking of partially neutralized carboxyl‐terminated liquid rubbers (PNCTLR) with bisepoxide and anhydride was investigated by the PNCTLR–bisepoxide–anhydride reactions. The PNCTLR were prepared, by the partial neutralization with MgO and CaO, from a polymer of butadiene (Hycar CTB 2000X162) and a copolymer of butadiene–acrylonitrile (Hycaṙ CTBN 1300X8). As the bisepoxide, bisphenol‐A diglycidyl ether was used, and hexahydrophthalic anhydride was the anhydride used. It was found that the metal carboxylate groups of PNCTLR catalyze the crosslinking reactions, and, further, the Mg carboxylate group showed higher catalytic activities than the Ca carboxylate group. As for the physical properties of the cured rubbers obtained, the rubbers containing Mg showed higher tensile strength and Shore A hardness than those containing Ca. In addition, the CTBN‐series cured rubbers showed better physical properties than those of the CTB‐series, because of a polarity effect of nitrile groups in the former rubbers. Resistances to water and chemical attack, thermal behavior, and stress relaxation are also discussed.
Dyeing of cotton fibers decrystallized by alkali swelling and partial substitution
Authors: Iyer P. Bhama , Iyer K. R. Krishna , Patil N. B. , Bhatt Indira G.
Published: April 2003

This report summarizes the observations made on the dyeing behavior of highly decrystallized cotton fibers obtained by partial acethylation and cyanoethylation of NaOH swollen fibers. The dyeing studies were also carried out after crosslinking these decrystallized samples. A purified direct dyeing Chlorazol Sky‐Blue FF, has been used for the studies. It is observed that partially cyanoethylated and acetylated celluloses show a dye uptake of more than twice that of the corresponding swollen controls even for low degrees of substitution such as about 5.0% acetyl content for the acetylated fibers and 1.0% nitrogen content for the cyanoethylated fiber. On crosslinking also the trend in the dye uptake pattern remained the same, thought the actual amount of dye the fibers could adsorb was markedly reduced. The swollen, substituted, and crosslinked fibers showed a better uniformity of appearance than the swollen and crosslinked fibers.
Structural transformations during chloromethylation of flexible polystyrene networks
Authors: Belfer Sofia , Glozman Raya , Deshe Abraham , Warshawsky Abraham
Published: April 2003

Strong morphologic variations were noted in the chloromethylation of styrene copolymers incorporating TAT or DVB as crosslinking agents. In the first case control over the chloromethylation conditoins (solvent, temperature, time) can be applied in order to mold the final porous structure of the chloromethylated polymer. In the case of XE‐305 containing higher concentration of crosslinking agent, the chloromethylation conditions have a less, but still significant, effect on the structure and functional group distribution of the product. Under conditions of low ratios of chloromethylating agent (CME) or catalyst (SnCl4), the chlorine incorporation figures are medium, but chlorine distribution through the cross section of the bead is more or less homogeneous. Increase in the above ratios results in increased chlorine concentrations, but also in higher degree of secondary crosslinking and uneven chlorine distribution profiles. Preselection of the experimental conditions enables calculated introduction of functional groups. In the case of TAT–styrene copolymers, controlled experimental conditions are used to form a porous structure with low and high chlorine distribution. Such a porous polymer can then be functionalized by other reactions. Under certain chloromethylation conditions, the chloromethylated TAT–styrene copolymer is aminated to produce anion exchange resins, without further morphological changes.
Investigation of the dependence of the infrared absorptivity of a functional moiety on the molecular weight of a homopolymer
Authors: Mirabella Francis M.
Published: April 2003

The subject of this investigation was the determination of the effect of molecular weight (MW) on the infrared absorptivity of a functional moiety in polystyrene homopolymer. It was found that no consistent dependence of infrared absorptivity on MW was found for two sharp absorptions of polystyrene across the MW range from 600 to 2 × 106. It was shown that end group effects for the very‐low‐molecular‐weight polymer fraction may be subtle and should be accounted for when using homopolymer calibration standrads in the study of the dependence of copolymer composition on MW.
Flame‐resistant cotton textiles by a continuous photocuring process
Authors: Harris James A. , Keating Esmond J. , Goynes Wilton R.
Published: April 2003

A continuous process for the photoinitiated copolymerization of vinyl phosphonate oligomer (MW 0.5–1.0 kg) and N‐methylolacrylamide from aqueous solutions with cotton printcloth and a sateen fabric was investigated. The free radical reactions, initiated on the cellulose molecules by exposure of the padded cotton fabric to UV radiation gave a flame‐resistant (DOC FF 3‐71 test) textile product. The effects of several variables on the efficiency of oligomer and monomer conversion to polymer add‐on were determined, with maximum efficiencies being 75–85%. Variables were fabric speed through the reactor (0.006–0.039 m/sec), light transmission through Pyrex or quartz windows in the tunnel, four sets of interchangeable tri‐power UV lamps having different spectral distributions and relative intensities, and heat buildup within the reactor. Selected samples of these modified cotton fabrics were evaluated for flame resistance, some textile properties, and elemental phosphorus and nitrogen analysis. Copolymer and phosphorus distribution within and between the cotton fibers were illustrated by transmission electron microscopy and by energy dispersive x‐ray analysis.
Crosslinking of partially neutralized liquid rubbers containing terminal and pendent carboxyl groups with anhydride and bisepoxide
Authors: Matsuda Hideaki
Published: April 2003

Crosslinking of partially neutralized liquid rubbers containing terminal and pendent carboxyl groups with anhydride, and bisepoxide was investigated by the carboxyl–anhydride‐epoxide reaction. The partially neturalized liquid rubbers were prepared by the partial neutralization with MgO and CaO from a butadiene (BD)–acrylonitrile (AN) copolymer (Hycar CTBNX 1300X9) with the functionality of 2.4. Bisphenol‐A diglycidyl ether (BADG) was the bisepoxide used, and hexahydropthalic anhydride (HPA) was the anhydride used. The metal carboxylate groups in the system catalyzed the curing reaction. The metal‐containing cured rubbers obtained showed considerably higher tensile strength than the previously reported metal‐containing cured rubbers based on CTBN 1300XB (BD–AN copolymer) with the lower functionality of 1.8. In addition, the cured rubbers generally showed higher water resistance, and lower weight gains in benzene, dioxane, and n‐hexane than the CTBN‐series ones. Thermal behavior and stress relaxation are also discussed.
Photochemical reactions of polyene sequences produced during the degradation of poly(vinyl chloride)
Authors: Owen Eryl D. , Pasha Ishrat
Published: April 2003

Photosensitized reactions of tetrahydrofuran (THF) and dichloromethane (DCM) solutions of polyene sequences introduced into poly(vinyl chloride) molecules by chemical degradation have been investigated. The distribution of polyenes produced following further thermal degradation in DCM were shifted toward longer sequences than were observed for the same reaction in THF. Benzophenone‐sensitized bleaching of the polyene absorption in aerated THF solutions was characterized by induction periods, but the presence of oxygen had little effect on the same reaction in DCM. The bleaching process seems to involve reaction of the polyenes with the tetrahydrofuranyl radical formed by abstraction of the α‐hydrogen from THF by triplet benzophenone. No induction periods were observed for benzoin‐sensitized reactions, but the rate of reaction was faster in DCM than in THF. The differences are discussed in terms of the difference in reactivity of the alkyl and alkoxy radicals.
Investigation of urea–formaldehyde polymer cure by infrared
Authors: Myers George E.
Published: April 2003

An examination has been made of the capability of conventional infrared analysis to define the structure of urea–formaldehyde (UF) polymers in the cured, crosslinked state. Proton NMR and infrared measurements of model compounds and uncured UF polymers were combined with infrared observations during polymer cure. The existing interpretation of UF polymer infrared spectra was clarified and a partial confirmation of the UF polymer cure mechanism obtained. However, it was concluded that conventional infrared possesses distinct limitations for defining the UF cure process in great detail, and it is hoped that the new solid‐sample NMR methods will prove capable of the desired structural determination in the cured state.
Limiting oxygen indices of silicone block polymer
Authors: Kambour R. P. , Klopfer H. J. , Smith S. A.
Published: April 2003

The limiting oxygen index (LOI) has been determined for each of a large number of silicone‐containing resins, principally dimethylsiloxane (DMS) block polymers varying widely in DMS content and hard block type. A synergistic enhancement in LOI of varying strength is seen in several families of resins. For the major families explored, the synergism varies with hard block type in roughly the following order: bisphenol‐A carbonate and bisphenol fluorenone carbonate > styrene and 2,6‐diphenyl‐1,4‐phenylene oxide > bisphenol chloral polycarbonate > methyl methacrylate and phenolphthalein carbonate, the enhancement being nil in the last case. Strength of the synergism is discussed in terms of DMS degree of dispersion, char‐forming tendencies, melt viscosity, and other factors.
High‐performance column adsorption chromatography of random copolymers styrene–acrylics
Authors: Danielewicz M. , Kubín M.
Published: April 2003

Random copolymers of styrene with acrylics can be separated according to their chemical composition by gradient column adsorption chromatography on silica. The composition of the mobile phase that can displace a given copolymer from the silica surface is independent of the shape of the solvent strength gradient and also above the sample molecular weight of ca. M = 100,000.
Synthesis and properties of polyesterimides and their isomers
Authors: Maiti Sukumar , Das Sajal
Published: April 2003

A new type of polyesterimide has been synthesized by polycondensation of a dicarboxylic acid containing an internal imide group with ethylene glycol. The dicarboxylic acid was synthesized by reacting aminobenzoic acid with trimellitic acid anhydride in N, N‐dimethylformamide solution. Three isomeric (ortho, meta, and para) polyesterimides were prepared from the respective isomer of the dicarboxylic acid. The solubility characteristics, solubility parameters, solution viscosity behavior, density, crystallinity, and thermal properties of these three isomeric polyesterimides were discussed. Some generalizations about structure–property relationship in polyesterimides were also made. It was found that while the ortho and meta isomers of the polyesterimide are amorphous, the para isomer tends to be somewhat crystalline and consequently less soluble, even in polar solvents. The thermal behavior of the meta isomer resembles closely that of the para isomer. The thermal stability of these isomers follows the order para ≥ meta > ortho.
Wet poly(vinyl chloride) membrane
Authors: Hirose Sachio , Yasukawa Eiki , Nose Takuhei
Published: April 2003

Wet, porous, and semipermeable poly(vinyl chloride) (PVC) membrane prepared from a binary system, PVC and dimethylformamide, by immersing in alcohols or ethers was studied. The pore dimensions of the wet PVC membrane were from 0.01 to 0.05 μm, calculated from hydrodynamic permeability by using experimental values such as water flux and water content. They agreed reasonably well with the dimension of the pores which prevented the protein passing through the membrane, observed by SEM photographs. Formation of the wet PVC membrane can be explained by slow phase separation and slow leaching of the casting solution immersed in alcohols and ethers such as methanol and ethylene glycol monomethyl ether.
Simulation model for the emulsion copolymerization of acrylonitrile and styrene in azeotropic composition
Authors: Lin Chen‐Chong , Ku Hwar‐Ching , Chiu Wen‐Yen
Published: April 2003

A simulation model based on the “unit segment” concept which provides prediction of conversion and molecular weight of product, is proposed for the emulsion polymerization of AN and St in azeotropic composition. Effects of initiator concentration and emulsifier concentration on conversion and molecular weight were studied experimentally and theoretically. It is found that the desorption of AN radicals should be taken into account, and the number of radicals per particle is always less than 0.5. The concentration of polymer particles is proportional to the 0.58 power in respect of the emulsifier concentration and to the 0.35 power in respect of the initiator concentration. The auto‐acceleration effect becomes significant when both initial emulsifier concentration and initiator concentration decrease, which influences the average molecular weight of the products. The azeotropic composition of AN–St is 28.5:71.5 by weight for this system at 60°C reaction temperature.
Gradient interpenetrating polymer networks. I. Poly(ether urethane) and polyacrylamide IPN
Authors: Dror M. , Elsabee M. Z. , Berry G. C.
Published: April 2003

The swelling properties of poly(ether urethane)s and the preparation of interpenetrating polymer networks (IPNs) from a poly(ether urethane) thermoplastic elastomer and hydrogel forming polyacrylamide have been studied. The acrylamide monomer was polymerized with simultaneous crosslink formation, in the presence of the swollen thermoplastic elastomer. Upon removal of the swelling solvent, an IPN was obtained which absorbed water in the manner of a hydrogel but had mechanical properties superior to a hydrogel.
Hydrolysis of polycarbonate to yield BPA
Authors: Bair H. E. , Falcone D. R. , Hellman M. Y. , Johnson G. E. , Kelleher P. G.
Published: April 2003

Elevated temperatures and high humidity decrease the molecular weight and impact strength of polycarbonate. Hydrolysis of injection molded polycarbonate (PC) bars stored in glass containers at 85°C and 96% relative humidity (RH) produced brown surface crystals within 30 days. Aging of PC bars at 96% RH and temperatures of 70°C and lower for longer periods of time formed a brown liquid coating on the PC. X‐ray, DSC, and GPC measurements indicated that about 70 wt% of the surface crystals were bisphenol A (BPA). The remaining portion of hydrolysis products appeared to be higher molecular weight oligomers of BPA. The brown liquid was composed of supercooled liquid BPA, BPA oligomers, and water. Initial growth of BPA on the surface of a PC bar took place at the interface between the PC and the glass wall of the container. Apparently a water soluble extract from the glass container accelerated the hydrolytic degradation of PC; nevertheless, hydrolysis of PC occurred in the absence of glass—although at a slower rate. Hydrolysis studies were carried out on several commercial PC formulations. The PC resin containing only a heat stabilizer was least affected. Of the fiame retardant grades, the brominated PC hydrolyzed less rapidly than these particular compositions containing alkali metal sulfonic acid salts. A glass fiber reinforced PC was less stable than its unfilled parent compound. A hydrolytic stabilizer was ineffective against the attack of water under these conditions.
The effect of heat setting on the structure and mechanical properties of poly(ethylene terephthalate) fiber. IV. Tensile properties other than modulus and their dependence on structure
Authors: Gupta V. B. , Kumar Satish
Published: April 2003

The stress‐strain characteristics of poly(ethylene terephthalate) fibers, heat set under different conditions have been studied under tension, and mechanical properties such as tenacity, yield point, elongation at break, and work of rupture are presented and discussed. An attempt has been made to correlate these mechanical properties with structural parameters. The orientation of the molecules in the fiber and the size and distribution of the crystallites emerge as important factors controlling the tensile properties.
Plasma etching durability of poly(methyl methacrylate)
Authors: Harada Katsuhiro
Published: April 2003

The decomposition of poly(methyl methacrylate) (PMMA), as a positive resist, in CF4/O2 plasma etching has been studied in the thin film state in order to clarify the factors influencing the dry etching durability of resists. It becomes clear that the major PMMA decomposition in CF4/O2 plasma etching proceeds by the mechanism of random chain scission because very small kinetic chain lengths are estimated from the gel permeation chromatography data. The Arrhenius plots for the plasma etching rate of PMMA bend above about the glass transition temperature (Tg), where rapid increase of the etching rate and remarkable pattern deformation are observed. Activation energy of the PMMA etching rate which is changed by oxygen concentration and rf power indicates various values from 3.1 to 6.5 kcal/mol below about Tg. The result of molecular weight variation in the cross section of the film suggests that the active species permeate into the film with fairly large speed and the PMMA decomposition occurs not only at the film surface but also at deep layer of the film.
Surface property modification of aromatic polyamides by microwave plasmas
Authors: Wertheimer M. R. , Schreiber H. P.
Published: April 2003

Various microwave plasma treatments were applied to Kevlar in the form of multifilament fabric and single fiber. Plasma‐modified fabrics were used to construct two‐ply laminates using a triazine resin adhesive. Very significant increases in the bond strength of laminates may be attributed to the plasma treatments; the effectiveness of plasma treatment is best utilized by reducing to a minimum the time interval between plasma exposure and contact of treated substrate with impregnating (adhesive) fluid. Mechanical properties of single Kevlar fibers seem to deteriorate somewhat on plasma exposure, but the cohesive strength of multifilament cloth is enhanced by the same treatments.
Simultaneous diffusion of benzyl alcohol into plasticized poly(vinyl chloride) and of plasticizer from polymer into liquid
Authors: Messadi D. , Vergnaud J. M.
Published: April 2003

The diffusion of benzyl alcohol and plasticizer in compression‐molded sheets of plasticized poly(vinyl chloride) was studied over the temperature range 30–55°C. A simultaneous diffusion occurred for benzyl alcohol into polymer and for dioctyl phthalate as plasticizer from polymer into liquid when the polymer was soaked in benzyl alcohol. The concentration of benzyl alcohol in polymer increased, rose to a maximum, and then decreased. Diffusion coefficients were measured by considering a nonsteady‐state phenomenon for plasticizer concentration of 25, 38, and 50 wt %, both for dioctyl phthalate and benzyl alcohol. Plasticizer concentration and temperature were found to play an important role.
Physical aging studies of semicrystalline poly(ethylene terephthalate)
Authors: Tant Martin R. , Wilkes Garth L.
Published: April 2003

Physical aging of semicrystalline poly(ethylene terephthalate) has been investigated as a function of crystalline content. Stress–strain, stress relaxation, and differential scanning calorimetry experiments were used to monitor the physical aging process. Both the overall extent and the rate of physical aging in this material decrease with increasing crystallinity. Several possible reasons for this behavior are advanced and discussed. It was also found that the drawing behavior of amorphous PET changes significantly as physical aging progresses. Specifically, for samples aged and then elongated, the extent of localized deformation (necking) and associated strain‐induced crystallization was greater for samples aged for longer periods of time.
Structure–property relationships of a new series of segmented polyether–polyester copolymers
Authors: Mody P. C. , Wilkes G. L. , Wagener K. B.
Published: April 2003

The work reported focuses on the structure–property relationships of a new series of segmented polyether–polyester copolymers. Poly(ethylene oxide‐hydantoin) is the soft segment, while poly(tetramethylene terephthalate) is the hard block and is suceptible to crystallization. The structure–property relationships have been addressed under three different subdivisions: (1) mechanical properties, (2) orientation effects and phase separation, and (3) morphology and superstructure. Where possible, a correlation has been made between these three categories.
Characterization by tin‐specific size exclusion chromatography of the free radical copolymerization of tributyltin methacrylate and methyl methacrylate
Authors: Parks E. J. , Brinckman F. E. , Mullin C. E. , Andersen D. M. , Castelli V. J.
Published: April 2003

Copolymers of tributyltin methacrylate (TBTM) and methyl methacrylate (MMA) comprise an important class of biocidal slow‐release organometallic polymers (OMPs). Little is known of the kinetics and mechanism of copolymerization. TBTM and MMA were copolymerized in the presence of a free radical initiator (benzoyl peroxide) at 80.1°C. Aliquots, taken at preselected intervals from 0 to 1440 min, were fractionated by size exclusion chromatography (SEC) coupled with ultraviolet (UV) and tin‐specific graphite furnace atomic absorption (GFAA) detectors. A UV absorbance observed at 254 nm was associated with low‐molecular‐weight species, decreasing in concentration continuously with time of reaction. Tin‐specific GFAA indicated a decrease in low‐molecular‐weight species (ca. 350 daltons) with concurrent increases in high‐molecular‐weight species (ca. 40,000 daltons). The fraction of high molecular‐weight increased as a linear function of the logarithm of the time of reaction. SEC–UV–GFAA thus provides a tool of major importance for characterizing the time dependence and continuity of the process by which monomers of TBTM are converted to a useful bioactive slow‐release coating material.
Radiation grafting of acrylic acid onto fluorine‐containing polymers. I. Kinetic study of preirradiation grafting onto poly(tetrafluoroethylene)
Authors: Hegazy El‐Sayed A. , Ishigaki Isao , Okamoto Jiro
Published: April 2003

Preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene) film was studied. The trapped radicals formed upon irradiation are able to induce graft polymerization under appropriate conditions. The influence of the grafting conditions were analyzed kinetically. The grafting reaction begins close to the film surface and proceeds into the center with progressive monomer diffusion through the grafted layer. The dependences of the grafting rate on preirradiation dose and monomer concentration were found to be 0.2 and 1.1 order, respectively. The overall activation energies for this grafting were calculated to be 15.2 and 4.8 kcal/mol below and above 35°C, respectively. The relationship between the grafting rate and film thickness gave a negative first‐order dependence.
Flows of dilute hydrolyzed polyacrylamide solutions in porous media under various solvent conditions
Authors: Durst F. , Haas R. , Kaczmar B. U.
Published: April 2003

Experimental results on pressure losses of flows of dilute polymer solutions through porous media are summarized. The polymer products employed in this study consisted of partially hydrolyzed polyacrylamides (HPAM) with different degrees of hydrolysis. The effect of the hydrolysis on the pressure drop is investigated in a porous media test section designed to minimize polymer degradation. The investigations were carried out for various solvent conditions, and it is shown that the maximum increase in pressure drop is mainly dependent on the molecular weight of the polymers. The onset of the polymer action is measured for various fluid and solvent properties. Particular attention is given to measurements near θ‐conditions. The results stress the importance of the solvent properties on the actions of the polymers and on the resultant pressure drop for porous media flows. The addition of salt ions to solutions of partially hydrolyzed polyacrylamides yields onset behavior previously observed for nonionic polymers. The differences measured between various solvent properties can be explained by the actual hydrodynamic molecule dimensions for a given molecular weight and polymer concentration. To quantify the influences of the solvent properties on the polymers, measurements were carried out in aqueous solutions for various pH values and therefore at various degrees of dissociation. The importance of separating polymer effects caused by their linear dimension in the solution from those that are introduced by and increase in solvent viscosity is shown. Measurements were performed to quantify the effects of solvent viscosity on the polymer action and to separate these effects from those due to changes in molecule dimensions. The implications of the present results are stressed in connection with applications of polymer solutions in tertiary oil recovery, and the positive features of the molecule actions on flow in such applications are described.
Reactive polymers. XXXIII. The influence of the suspension stabilizer on the morphology of a suspension polymer
Authors: Horák D. , Pelzbauer Z. , Ŝvec F. , Kálal J.
Published: April 2003

Sorbents based on glycidyl methacrylate were used in an investigation of the effect of the type of the suspension stabilizer and of its concentration on the shape, size, and morphology of beads consisting of submicroscopic particles (globules). Of many stabilizers used, only poly(vinyl pyrro‐lidone) and poly(vinyl alcohol) led to the formation of regular spherical beads with a surface shell. As expected, beads obtained using a stabilizer producing higher interfacial tension poly(vinyl pyrrolidone)‐K 90 were much larger. A similar effect may be reached by lowering the concentration of poly(vinyl alcohol), if this lowering is accompanied by a rise in the interfacial tension. Despite this, however, the surface shell was not compact in this relatively narrow range of interfacial ten‐sions.
Binary and ternary blends of poly(vinyl chloride), hytrel, and a polyurethane
Authors: Hourston D. J. , Hughes I. D.
Published: April 2003

Binary blends of poly(vinyl chloride) and a poly(ether urethane) containing 20 and 40 weight percent, respectively, of poly(vinyl chloride) have been prepared by solution blending from tetrahydrofuran and their degree of mixing investigated using dynamic mechanical analysis. In the polyurethane, transitions were found at −19°C and −119°C. The former was attributed to the glass transition and the latter to a Schatzki type of motion of the polyether sequences. This latter transition occurred at a temperature which is higher than the literature value for the low temperature transition in poly(tetrahydrofuran), which is equivalent to the polyether sequence in the polyurethane. This discrepancy is attributed to the influence of neighboring hard segments present because of incomplete segmental phase separation of the polyurethane. For the blends only one very broad transition was observed, indicating that there was substantial mixing of these two polymers. Three ternary blends were prepared, also by solution blending, containing poly(vinyl chloride), Hytrel, and the polyurethane in the ratios 1:1:1, 1:2:1, and 2:1:1, respectively. In the first two blends there was clear evidence of phase separation. It was only in the 2:1:1 blend that an apparently significantly compatible material resulted.
Axial dispersion in laminar flow of polymer solutions through coiled tubes
Authors: Saxena Alok K. , Nigam K. D. P.
Published: April 2003

The results of an experimental study on axial dispersion in laminar flow of non‐Newtonian fluids through helical coils are reported. The ranges of variables covered are 10.5 ≤ λ ≤ 220, 0.6 ≤ n ≤ 1.0, 0.1 < NRegn < 140, and 0.04 < τ > 2.2. The condition for the applicability of Taylor's dispersion model is also reported. It is found that coiling results in a dispersion reduced over that in a straight tube.
Natural and accelerated weathering of some polyblends
Authors: Feldman D.
Published: April 2003

A weathering study has been carried out on a polyurethane elastomeric adhesive and its polyblends with the following vinyl polymers: poly(vinyl chloride), poly(vinyl alcohol), poly(vinyl acetate), and vinyl acetate—vinyl chloride copolymer. Stress‐strain measurements were done on an Instron model 1125 testing machine after aging at normal room conditions, outside, and in an artificial weathering chamber. The observed modifications of the mechanical properties can be attributed to a decrease of the molecular weight of the polymers involved during the cryolysis process; this process is less significant for natural weathering than for artificial weathering. Results are discussed and conclusions drawn.
Catalyzed polymerization of cycloolefins
Authors: Tsonis C. P.
Published: April 2003

The catalyzed polymerization of cycloolefins may lead to a ring retention polymer product or to a polyalkenamer. The homogeneous catalysts, derived from V, W, Mo, and Re transition metal complexes, normally require the synergistic use of an alkylaluminum cocatalyst. Trans‐1, 5‐poly‐alkenamers exhibit elastomeric properties and might be suitable for tire manufacture.
A new epoxy resin/hardener system with variable processing and end properties
Authors: Eldin Sameer H. , Stockinger Friedrich , Lohse Friedrich , Rihs Grety
Published: April 2003

A combination of a standard bisphenol‐A liquid epoxy resin and a zinc–pyrrolidone–carboxylate complex with a long chain poly(oxypropylene diamine) (Jeffamine D 2000) has been found to give variable processing and end properties over a very wide range, e.g., pot life < 1–70 days, Martens Heat‐Distortion Temperature < 25–124°C and elongation at break 35–1%. The variation in properties is achieved simply by changing the epoxy/complex ratio. The very reactive high elongation formulation is thought to be the result of a very fast zinc catalyzed amine/epoxy polyaddition reaction and the low reactivity rigid formulation to be due to zinc‐complex initiated anionic homopolymerization of the epoxy resin. The borderline concentrations are approximately 200 and 10 phr of the complex, respectively.
Impact testing of a thermosetting polymer (allyl diglyol carbonate–CR39)®
Authors: Howes V. R. , Goldsmid J. M. , Silk R. K. , Were A. V.
Published: April 2003

Allyl diglycol carbonate (CR39)® is a thermosetting polymer of interest both as an ophthalmic material and as a material intermediate between brittle and ductile solids. The response to impact in the crack‐threshold range has been studied and compared to that of glass. The energy absorbed upon impact, the plastic deformation, and the crack resistance are all found to be greater for CR39, and the relationships between these factors are discussed. The developments of impact response for CR39 with increasing temperature and increasing impact energy beyond the crack‐threshold range have also been studied.
Plasma polymerized protective films for plated magnetic disks
Authors: Harada Katsuhiro
Published: April 2003

Plasma polymerized protective films (PPP films) for magnetic disks have been investigated in order to improve weak durability of plated disk media to head friction and clash. The thickness heterogeneity of PPP films within 5% was realized around the all surface of 140 mmϕ model substrates, determining the best discharge condition and apparatus geometry, which did not exert and aggravating influence upon head floating. The friction coefficients of PPP films to a ferrite slider of 0.3 ∼ 0.4 were obtained in the thickness of above near 1500 Å, although PPP films are composed of hydrocarbon or fluorocarbon. As the results of contact start/stop cycle tests by a floating head, plasma polymerized toluene‐2,4‐diisocyanate films show good abrasive durability because of its superior adhesiveness to metal substrates, and PPP films in small thickness near 1000 Å give good protective films. The result of read/write tests indicated that the magnetic deterioration and instability of plated disk media did not occur by the process of plasma polymerization.
Stochastic modeling of polymerization in a continuous flow reactor
Authors: Nassar R. , Too J. R. , Fan L. T.
Published: April 2003

A stochastic approach, namely, a continuous time Markov chain (Markov process), is employed to analyze and model, in a unified fashion, both polymerization and dispersive mixing in a continuous flow reactor. Results include the distribution of numbers of active and dead polymers with chain length j both inside the reactor and at the exit. This approach can be extended to the determination of the degree of polymerization of a copolymer. Expressions are derived for the mean and variance of the number of monomers of a given type in a copolymer chain. The model can be applied to both the time homogeneous and heterogeneous processes.
Effect of fillers on the viscoelastic behavior of rubbers
Authors: Stenberg B. , Jansson J. F.
Published: April 2003

The different reinforcing effects of carbon blacks are determined by measurements of the linear and nonlinear viscoelastic behavior of natural rubber samples subjected to prestrains at different levels. The transition from linear to nonlinear viscoelastic behavior occurs at lower strains as the carbon black content is increased. At a given filler concentration, the limiting strain is highest for the most reinforcing carbon black. Prestraining increases the limiting strain. The reinforcing effect of carbon black can be estimated by determining the extent to which prestraining influences the linear viscoelastic properties of vulcanizates.
Grafting onto wool. XI. Graft copolymerization of poly(vinyl acetate) and poly(methyl acrylate) onto reduced wool in presence of potassium persulfate–ferrous ammonium sulfate (KPS—FAS) system as redox initiator
Authors: Misra B. N. , Dogra R. , Mehta I. K. , Gill Kiran Dip
Published: April 2003

In an attempt to ascertain the role of—SH groups of Himachali wool during graft copolymerization, poly(viny acetate) (PVAc) and poly(methyl acrylate) (PMA) were graft copolymerized onto reduced wool by using potassium persulfate—ferrous ammonium sulfate (KPS—FAS) redox pair in aqueous medium. Reduction of wool was carried out by sodium bisulfite solution of varying concentrations for different reaction periods. Concentration of reducing agent and the extent of reduction were found to influence grafting of vinyl monomers. Maximum grafting of methyl acrylate (MA) and vinyl acetate (VAc) occurred when wool was reduced by 1% and 0.5% NaHSO3 solution, respectively, for 24 h. Increase in percent grafting of MA onto reduced wool compared to that of unreduced wool has been ascribed to the production of more—SH groups by reduction of—SS—groups of wool fiber.