bluuebunny/crossref_metadata_2025 huggingface dataset:
On the crystal structure of nylon 6
Authors: Parker James P. , Lindenmeyer Paul H.
Published: April 2003

Nylon 6 can exist in either of two stable crystal structures, the α crystal with hydrogen bonds between antiparallel chains or the γ crystal with hydrogen bonds between parallel chains. Both structures have been observed in the same highly annealed fiber, suggesting that the polymer should not be regarded as a pure compound but a multicomponent mixture. Nylon 6 can also exist in a series of metastable crystal structures which vary continuously in size, perfection, and structural parameters from a pseudohexagonal structure to either of the two stable forms. A single equatorial reflection in the wide‐angle x‐ray pattern (i.e., pseudohexagonal structure) will not distinguish which of the two stable forms will result upon annealing. Measurement of the 0,14,0 reflection in oriented fibers will distinguish the major trend, but it is still uncertain to what extent annealing conditions can favor one stable form over the other. The variation in the unit cell parameters as a function of annealing has been accurately measured, and the observed phenomena can be qualitatively described by postulating various balances between the basic forces which hold the crystal together (i.e., hydrogen bonding, dipole–dipole interaction, van der Waals attraction, and covalent bonding).
On the relationship between K and a and between Kθ and the molecular weight per chain atom
Authors: Aharoni Shaul M.
Published: April 2003

It is shown that in [η] = KMa there exists a relationship between K and a of the form log K = C − Ba. The parameters C and B are typical of each polymer and, under θ conditions, define a characteristic Kθ for the polymer. When plotted against m0/z, the molecular weight per backbone atom, the values of log Kθ cluster along three distinct lines. In a fashion similar to the observed dependence of number of atoms between chain entanglements on m0/z, the lines are associated with highly flexible polymers, intermediate flexibility polymers, and stiff chain polymers. Deviations from the intermediate flexibility line are explained on the basis of changes in the distribution of mass in the plane perpendicular to the overall direction of the backbone chain.
Melt spinning of nylon 6: Structure development and mechanical properties of as‐spun filaments
Authors: Bankar Vilas G. , Spruiell Joseph E. , White James L.
Published: April 2003

The structure of melt‐spun nylon 6 filaments was studied using on‐line x‐ray diffraction and birefringence measurements. Measurements were also made on as‐spun and treated filaments. On‐line wide‐angle x‐ray scattering measurements indicated that crystallization did not occur on the nylon 6 spinline at spinning rates up to 1000 m/min when spinning was done into either ambient air of 60% relative humidity or into wet saturated air. The filaments did crystalline gradually on the bobbin to a paracrystalline pseudohexagonal (γ) form. The rate of crystallization was dependent on the molecular orientation developed in the spun filaments. Crystalline orientation factors based on hexagonal symmetry were computed as a function of take‐up velocity for fibers which were conditioned 24 hr in air at 65% relative humidity. Annealing in air or treatment in water or 20% formic acid solution causes a transformation from the pseudohexagonal form to the α monoclinic form. The tangent modulus of elasticity and tensile strength of spun and conditioned filaments increase with increasing take‐up velocity and spinline stress, while elongation to break decreases with these variables.
Physical properties and structure of silk. III. The glass transition and conformational changes of tussah silk fibroin
Authors: Magoshi Jun , Magoshi Yoshiko , Nakamura Shigeo
Published: April 2003

The glass transition, crystallization, and α–β transition of the Tussah silk fibroin were studied by means of DSC (differential scanning calorimetry) and infrared spectroscopy. The endothermic shift due to the glass transition was observed at 162°C. The endothermic peak at 220°C was attributed to the α–β conformational transition from the infrared spectra. The exothermic peak due to the crystallization occurred at 230°C.
Melting of hydrogels containing ammonium nitrate
Authors: Ahad Elie
Published: April 2003

The fusion of hydrogels containing ammonium nitrate (AN) has been investigated by differential scanning calorimetry (DSC). The polymers used were guar and xanthan gums as well as synthetic polyacrylamide polymers. Water in hydrogels could be classified into three types labeled as ordinary water (hump of the melting peak), intermediate water (broad component of the peak), and bound nonfreezing water (without any phase transition). The temperature of fusion of intermediate water was about 10° to 35°C lower than that of ordinary water. Intermediate and bound water was found in all the gels studied, whereas ordinary water existed mainly in mixtures with total water content higher than 62%. The presence, type, and concentration of a crosslinker had no effect on the amount of bound water in hydrogels containing AN. In such mixtures the amount of nonfreezing water increased with the polymer concentration as well with the AN proportion relative to water and represented in some cases up to 27% of the gel. Cold‐crystallization was observed in all cases (except xanthan) and was probably initiated by AN or the crosslinking agent.
Wood fiber–synthetic polymer composites. II. Laminates of treated fibers and polyolefins
Authors: Michell Anthony J. , Vaughan Janet E. , Willis Donald
Published: April 2003

Flexural properties of laminates prepared by hot pressing commercial papers and laboratory handsheets with films of polyolefins were measured following exposure to different levels of moisture. Prior to their incorporation in the laminates, the fibers, either individually or as preformed paper, were acetylated or crosslinked with formaldehyde to reduce their sensitivity to moisture. The results are compared with earlier measurements which showed that the properties of laminates based on paper precoated with polyethylene declined sharply at high relative humidities. For laminates comprising laboratory handsheets made from acetylated fibers, the decline in properties is less but the initial values under dry conditions are lower also. However, acetvlation or crosslinking of preformed paper improves up to threefold the retention of flexural modulus by the laminates under the wettest conditions with no concurrent loss in this property under dry conditions, although some embrittlement of the component paper sheets is observed. Enhanced fiber alignment or the addition of 5% glass fibers to the paper does not arrest the decline in flexural properties of the laminates with increasing relative humidity. This decline differs little when other polyolefins are used but is accentuated when ethylene–vinyl acetate copolymer is the binder.
Studies on heating and cooling of synthetic fibers, yarns, and fabrics. I. Properties of nylon and polyester filament yarns on heat setting in silicone oil
Authors: Venkatesh G. M. , Bose P. J. , Shah Rekha V. , Dweltz N. E.
Published: April 2003

Nylon 6, nylon 66, and polyester [poly(ethylene terephthalate)] filament yarns were heat set at different temperatures in oil under a variety of experimental conditions. The effect of time of heat setting, tension on the yarn during heat setting, as well as the effect of the initial tenacity and extension on subsequent changes in the mechanical properties of the heat‐set yarns have been studied. The breaking strength, elongation at break, and work of rupture have been found to be different for samples heat set while slack and at constant length. The breaking strength remains more or less constant over a wide range of heat setting temperatures up to 240°C in the case of nylon 66 and polyester, and up to 200°C in the case of nylon 6, contrary to the observations of Dumbleton et al. When treated in the slack condition, the breaking extension increases by about 1–2.5 times the control value, while heat setting at constant length produces a decrease in the case of nylon 66 and a marginal increase in the case of nylon 6 and polyester. The initial modulus decreases irrespective of the conditions under which the filaments are heat set. From measurements of the shrinkage and the residual shrinkage in boiling water it appears that dimensional stability can be achieved by heat setting even at constant length. Heat setting produces significant improvement in the crease recovery and resiliency of the fibers. Heat setting has also been found to significantly increase the overall crystallinity of the fibers as determined by critical dissolution time and parallel and perpendicular refractive indices. The overall orientation of the polymer chains, as determined from sonic velocity measurements, decreases on heat setting in the slack condition. Heat setting at constant length produces a marginal improvement in the overall orientation only in the case of nylon 66 yarns. Shrinkage occurs instantaneously. Crystallinity, on the other hand, improves with increasing time of heat setting.
Rheology of high solid coatings. I. Analysis of sagging and slumping
Authors: Wu Souheng
Published: April 2003

The rheology of sagging and slumping of high solid coatings on vertical surfaces is analyzed in terms of a non‐Newtonian power‐law model. The results indicate that, in order to have good sag control and good sprayability at the same time, high solid coatings should be pseudoplastics with a power constant of about 0.6 and a viscosity at 1 sec‐1 of about 25 poise at the temperature of interest. This theoretical prediction is confirmed experimentally.
Plasma‐deposited polymer films. II. Transmission and scanning electron microscopy
Authors: Havens M. R. , Mayhan K. G. , James W. J.
Published: April 2003

A transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study of plasma‐formed polyethylene and polystyrene is reported. A two‐phase structure of spheres embedded in a polymer binder is evident, supporting the predictions of earlier low‐angle x‐ray scattering data taken of these two plasma‐deposited polymers.
Bromostyrene crosslinked polyesters. IV. The effects of the CBr bond strength and of synergists on fire retardancy
Authors: Alsheh D. , Marom G.
Published: April 2003

The present study compares the effect of ortho‐bromostyrene to that of para‐bromostyrene on fire retardancy of polyesters at low and high flame temperatures. It is shown that the first isomer is more effective at the lower temperature and vice versa at the higher temperature. Thermoanalysis results partly explain this difference as well as the effect of additives such as Sb2O3 and bis(2‐chloroethyl) vinylphosphate.
2,2′,6,6′‐Tetrabromo‐3,3′,5,5′‐tetramethyl‐4,4′‐biphenol (TTB)–flame retardant copolycarbonates and copolyesters
Authors: Kinson P. L. , Orlando C. M.
Published: April 2003

2,2′,6,6′‐Tetrabromo‐3,3′,5,5′‐tetramethyl‐4,4′‐biphenol (TTB) is a new flame retardant monomer possessing a high degree of chemical and thermal stability. This brominated biphenol can be directly incorporated as a comonomer in condensation polymerizations. An example is the preparation of copolycarbonates of TTB and 2,2‐(4‐hydroxyphenyl)propane (BPA) via the aqueous caustic phosgenation method. The reaction of TTB with either ethylene oxide or ethylene chlorohydrin affords 4,4′‐bis(2‐hydroxyethoxy)‐2,2′,6,6′‐tetrabromo‐3,3′,5,5′‐tetramethylbiphenyl (TTB‐Diol). This diol is melt polymerized into a series of terephthalate copolymers with 1,4 butanediol. The above copolymers possess flame retardancy, thermal stability, and good mechanical properties. These high‐bromine‐content copolymers are blended with nonhalogen‐containing polymers to afford blends with specific degrees of flame resistance.
Phase equilibra of polystyrene/polybutadiene/tetrahydrofuran using gel permeation chromatography
Authors: Narasimhan Venkataraman , Lloyd Douglas R. , Burns Charles M.
Published: April 2003

Gel permeation chromatography using sequential differential refractive index and ultraviolet detectors has been successfully used to give the compositional analysis of conjugate phases in the incompatible system of polystyrene and polybutadiene with tetrahydrofuran as solvent. Application of this method to equilibrated samples yields tie lines, binodal curves, and plait points. The effects of molecular weights and molecular weight ratios on the slopes of the tie lines, the location of the binodal curve, and the depletion of second polymers from phases are discussed.
Formation of peroxide on aldehyde cellulose and its ability to initiate graft copolymerization
Authors: Ogiwara Yoshitaka , Umasaka Tatsuo , Kubota Hitoshi
Published: April 2003

Cellulose peroxide formed by the treatment of aldehyde cellulose with hydrogen peroxide (H2O2) was investigated with respect to formation and decomposition conditions and with respect to graft initiation. Periodic acid‐oxidized cellulose was proved to produce the peroxide group on the substrate by subsequent treatment with H2O2, whereas no peroxide was produced with unoxidized cellulose. Since the peroxide content of oxidized cellulose increased with increasing carbonyl content of the sample, the peroxide was presumed to be introduced at the site of the aldehyde group of the sample. The peroxide groups formed were proved to revert to aldehyde groups by decomposition upon heating with water to nearly the same level as the original. The structure of the peroxide group was believed therefore to be an α‐hydroxy hydroperoxide type. The cellulose peroxide was found to initiate graft copolymerization of methyl methacrylate very easily in thermal initiation and photoinitiation systems.
Copolymerization of styrene–m‐divinylbenzene in the presence of poly(vinyl chloride)
Authors: Kagiyama Yasuhiro , Shikata Kazuo , Mizutani Yukio
Published: April 2003

The crosslinking copolymerization of styrene (St)‐m‐divinylbenzene (m‐DVB) in the presence of poly(vinyl chloride) (PVC) was studied. The rate of the copolymerization decreased with the addition of PVC powder, because of the depressing of the diffusion of the monomers to the polymerizing center and the difficulty in the transfer of the polymer radicals in the swelled PVC powder. The exponential value of the benzoyl peroxide concentration and the activation energy of the copolymerization were obtained as 0.67 and 17.4 kcal/mol, respectively. The monomer reactivity ratios of St and m‐DVB were determined as r1 = 0.25 and r2 = 1.42 (M1: St, M2: m‐DVB). From the extraction of the resultant polymer composite with THF, both the grafting of the St‐m‐DVB copolymer onto PVC and the entanglement of PVC with St‐m‐DVB copolymer seems to occur in the St‐m‐DVB‐PVC system.
Novel binary chlorides containing TiCl3 as components of coordination catalysts for ethylene polymerization. I. Synthesis and characterization of the solid solutions obtained
Authors: Greco A. , Perego G. , Cesari M. , Cesca S.
Published: April 2003

New binary chlorides have been obtained by reacting TiCl4 with V(CO)6, Cr(CO)6, Mn2(CO)10, Mn(CO)5Cl, Ni(CO)4, Co2(CO)8, Fe(CO)5, or Mo(CO)6. The reactions yield quantitatively mixed chlorides having the general formula MCln·n TiCl3, where n = 2 or 3 and M is a divalent or trivalent transition metal cation. MCln is generally isomorphous with the α‐ or γ‐modification of TiCl3. X‐Ray and spectroscopic investigations indicate that the mixed chlorides obtained are solid solutions. High surface area values are associated with the adducts displaying lower crystallinity. Catalyst efficiencies two or three times higher than that of AlCl3·3TiCl3 were observed in the low‐pressure polymerization of ethylene (HDPE) when some binary chloride was associated with Al(i‐C4H9)3. These results allow treating the obtained solid solutions as reference systems of high‐yield catalysts for HDPE synthesis.
Composite hollow fiber membranes
Authors: Cabasso Israel , Tamvakis Anthony P.
Published: April 2003

Composite polysulfone hollow fibers consisting of a polysulfone porous substrate coated with crosslinked polyethyleneimine (PEI) or furan resin are reported. These composite hollow fibers are analogous to the flat‐sheet composite membranes known as NS‐100 and NS‐200. The surface structure of the porous substrate was rigorously studied before and after coating. Scanning electron microscope observations and reverse osmosis transport studies showed that the support fiber must have surface pore diameters of less than 0.2 μm to obtain a durable composite hollow fiber membrane. The curing process would normally follow in situ condensation of the PEI or the cationic polymerization of the furfuryl alcohol. However, since both the dense layer and surface of the porous substrate contract when exposed to the curing temperature (110–150°C), it was found to be profitable to cure the hollow fiber before applying the coating. When tested in a reverse osmosis rig, PEI/TDI‐coated polysulfone hollow fiber bundles displayed 98% salt rejection and a flux of 5–7 gfd for a feed solution of 10,000 ppm NaCl at a hydraulic pressure of 400 psi. A new method of depositing furan resin on the polysulfone hollow fiber is described. The furfuryl alcohol is instantaneously polymerized by exposing the alcohol‐soaked fiber to a 60% solution of concentrated sulfuric acid. It has been demonstrated that in such a polymerization procedure a dense, semipermeable layer is formed on top of the porous substrate; the resulting composite hollow fiber membrane yields salt rejections higher than 98% when tested under the above reverse osmosis conditions.
Aspects of the thermal and dynamic mechanical behavior of EPDM rubbers
Authors: Byrne L. F. , Hourston D. J.
Published: April 2003

The influence of both ethylene content and the degree of crystallinity on the thermal and dynamic mechanical properties of certain commercial EPDM rubbers were investigated using the TMA, DSC, and Rheovibron techniques. The six materials chosen for this study were Nordel 1560, Intolan 260, Royalene 1812, Vistolan 3708, Intolan 255, and Keltan 778.
Morphology studies of the liquid‐induced crystallization of poly(ethylene terephthalate): Effects of polymer blending, nucleating agents, and molecular weight
Authors: Makarewicz P. J. , Wilkes G. L.
Published: April 2003

The morphology associated with the liquid‐induced crystallization of poly(ethylene terephthalate) (PET) blended either with poly(tetramethylene terephthalate) (PTMT), atactic polystyrene (APS), or polycarbonate of bisphenol A (PC) was studied, along with the effects of nucleating agents and polymer molecular weight on this type of crystallization in PET. It was found that melt‐mixed blends of PET and either PTMT or PC led to an apparent well‐mixed, two‐component material in which some copolymer formation may be in evidence judging from the material superstructure. Blending PET with APS appeared to produce distinctly phase‐separated materials in which PET could be crystallized and APS dissolved out of the structure as a result of treatment of the blend with certain types of liquid. The incorporation of nucleating agents into PET was shown to measurably influence the spherulitic character of the subsequently liquid‐induced crystallized polymer. Finally, it was determined that liquid‐induced crystallized PET samples with number‐average molecular weights of 18,000 and 30,000 had identical characteristic morphology and apparent crystallization kinetics.
Fine structure investigation of Sansevieria roxburghi fiber by small‐angle x‐ray methods
Authors: Ratho Sabita
Published: April 2003

Small‐angle x‐ray methods were used to evaluate macromolecular parameters such as specific inner surface of the dispersed phase; transversal lengths such as length of inhomogeneity and length of coherence; and the air fraction of the scattering particles in Sansevieria roxburghi; these parameters were found to be 12.76 × 10−6 Å−1, 549.9 Å, 15.21 Å, and 0.17%, respectively. A small‐angle Kratky camera was used for the experimental measurements, and the theories of Kratky and Kratky and Porod were utilized to evaluate these parameters. The sample under investigation is treated as a densely packed colloidal system belonging to general micelle systems.
Temperature dependence of impact fracture energies of short glass fiber–epoxy and unsaturated polyester composites
Authors: Miwa Minoru , Ohsawa Tadashi , Tsuji Naoki
Published: April 2003

The temperature dependence of the impact fracture energies of composites reinforced with random‐planar orientation of short fibers was studied theoretically and experimentally. The theoretical values of the impact fracture energy of these composites is described by the sum of the fracture energy of the matrix and the fibers and the energy necessary to pull out the fibers on the crack surface, taking into consideration the temperature dependence of the critical fiber length and the breaking probability of fibers. The impact fracture energies were studied experimentally for epoxy and unsaturated polyester resins reinforced with random‐planar orientation of short glass fibers. The theoretical values of the impact fracture energy were in good agreement with the experimental values. It was found that in any composite, the impact fracture energy of the fibers in a composite mainly contributes to the impact fracture energy of the composite at room temperature. At higher temperatures, fiber pull‐out energy is more significant.
The effect of chemical structure of derivatives of 1,1‐bis(4‐hydroxyphenyl)‐2,2‐propane on the antiplasticization of polycarbonate
Authors: Makaruk Leszek , Polańska Hanna , Mizerski Tadeusz
Published: April 2003

The antiplasticizing effect of ester derivatives of bisphenol A: 1,1‐bis(4‐hydroxyphenyl)‐2,2‐propane diacetate (DAPP), 1,1‐bis(4‐hydroxy‐3,5‐dichlorophenyl)‐2,2‐propane diacetate (DACPP), 1,1‐bis(4‐hydroxy‐3,5‐dibromophenyl)‐2,2‐propane diacetate (DABPP), 1,1‐bis(4‐hydroxy‐3,5‐dichlorophenyl)‐2,2‐propane dibenzoate (DBCPP), 1,1‐bis(4‐hydroxy‐3,5‐dichlorophenyl)‐2,2‐propane di‐2,4‐dichlorobenzoate (DCBCPP) on polycarbonate was investigated. Obtained results indicate that antiplasticizing abilities of these compounds depend on the number of polar groups in the molecule, as well as on the possibility of tight filling the free volume by the molecules in polymer–antiplasticizer system.
Reinforcement of siloxane elastomers by silica. Interactions between an oligomer of poly(dimethylsiloxane) and a fumed silica
Authors: Berrod G. , Vidal A. , Papirer E. , Donnet J. B.
Published: April 2003

The study of the adsorption of an organosiloxane onto a fumed silica was undertaken in order to improve our knowledge of the reinforcement of silicon rubbers by silica. IR and gas‐phase chromatography techniques were used to characterize the adsorption of octamethyltetracyclosiloxane. At room temperature, the occurrence of hydrogen bonding between the solute and the adsorbent was shown. The amount of material adsorbed according to this mechanism was shown to be strongly dependent on temperature. The heats of adsorption at various covering ratios were calculated from the isotherms measured at temperatures close to 150°C.
Transparent fluorocarbon‐based semi‐II IPN elastomers by high‐energy radiation methods
Authors: Lipko J. D. , George H. F. , Thomas D. A. , Hargest S. C. , Sperling L. H.
Published: April 2003

Semi‐II interpenetrating polymer network fluorocarbon elastomers were prepared by the addition of small amounts of a multifunctional monomer to the linear fluorocarbon polymer, followed by radiation polymerization in situ. The linear fluorocarbon is physically bound up with crosslinked network II, producing a semi‐IPN of the second kind. Due to the high‐energy radiation attack on the fluorocarbon backbone, a significant amount of graft copolymer forms which improves compatibility and yields clear, transparent elastomers. High‐energy β and γ radiation produce very similar semi‐IPN elastomers. Low‐energy UV, which does not promote grafting, produces poorer quality elastomers which show significantly less optical clarity, much lower strength, and higher creep. High‐energy radiation also appears to destroy possible incipient crystallinity thought to be present in the linear fluorocarbon material.
The effect of transition metal stearates on the photodegradation of polyethylene
Authors: Osawa Zenjiro , Kurisu Norio , Nagashima Kosaku , Nakano Kosaku
Published: April 2003

The effect of a series of transition metal (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) stearates on the photodegradation of a high‐density polyethylene was examined mainly by changes in the carbonyl IR absorption of the sample films. Electron spin resonance (ESR) and luminescence spectra of the samples containing the copper stearate were measured. The photochemical reaction of the copper stearate was examined by IR and UV‐visible spectroscopies. The iron stearate was the most effective at an early stage of the photodegradation of the polymer, and vanadium and manganese stearates accelerated it, while the copper stearate retarded it. The other metal stearates showed no applicable effect on the photodegradation. The relative intensity of the ESR spectra of the photoirradiated samples and that of the emission spectra of the unirradiated samples at ca. 350 nm decreased with increasing concentration of the copper stearate. An absorption peak at 1580 cm−1 decayed, and a new peak at 1740 cm−1 appeared with photoirradiation of the copper stearate. Absorption peaks of the copper stearate at 252 and 665 nm decayed also rapidly with photoirradiation of the copper stearate in THF solution. The results suggest that one of the main retardative functions of the copper stearate in the photodegradation of polyethylene was an ultraviolet absorber.
Grafting starch xanthate with vinyl monomers and hydrogen peroxide in foam rubber production
Authors: Maher G. G.
Published: April 2003

Starch xanthate with degrees of substitution (D.S.) ranging from 0.12 to 0.56 reacted with vinyl monomers (acrolein, acrylamide, acrylic acid, acrylonitrile, methyl acrylate, or styrene) and hydrogen peroxide to form aqueous gels of starch–polyvinyl monomer graft copolymer. The same reactions conducted in a rubber latex medium resulted in a self‐acidifying, self‐heating, and self‐foaming coagulation to give a foam rubber. Such products were formed from several synthetic latices (NBR, SBR, polyisoprene, and polychloroprene types) and natural rubber latex; noted for each were the effects of the D.S., of monomer and peroxide concentrations, and of starch:elastomer ratios. The dried foams were evaluated by standard strength tests. Foam rubber of acceptable extensibility and enhanced tensile strength (up to 110 psi) was obtained with 0.12–0.15 D.S. xanthate and with proper balance of vinyl monomer, peroxide, and starch:elastomer ratio. Resilience was fair to good, but compression set was rather poor compared to most foam rubbers of general use.
Flywheel‐type tensile impact tester with a new load cell for polymer sheet and film
Authors: Yokouchi Mitsuru , Kobayashi Yasuji
Published: April 2003

A new load cell for flywheel‐type impact tensile testing was designed and fabricated for specimens of polymer sheet and film. The cell employs a piezoelectric ceramic oscillator (toric in shape) as a load sensor, which has a high natural frequency (1800 kHz) and high sensitivity (ca. 0.1 V/N without amplification). The time constant for the electric circuit was improved substantially by the introduction of a voltage follower using an operational amplifier with excellent performance (common mode voltage ±120 V and slew rate 100 V/μsec). The positioning of the load sensor and the shape of specimen clamps are important design features, especially the halved Morse‐type taper pins in the structure of the specimen clamps. Signals of impact, passing through the piezoelectric oscillator and the voltage follower, are recorded by a transient time converter. The converter is equipped with a memorization system, an automatic pretrigger circuit, and a facility for reproduction under a slow time base, thus eliminating the need for troublesome photographing. For performance testing of the impact tester, oriented poly(ethylene terephthalate) sheets were used and good results were obtained.
D2‐m‐carboranesiloxanes. VIII. Preparation and characterization of carboranesiloxane/polysulfone alternating block copolymer
Authors: Stewart D. D. , Peters E. N. , Beard C. D. , Moffitt R. B. , Kwiatkowski G. T. , Bohan J. J. , Hedaya E.
Published: April 2003

A D2‐m‐dodecacarboranesiloxane containing alternating block copolymer \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--}[{\rm A}\hbox{---}{\rm B}\rlap{--}]_n$\end{document} was prepared by the reaction of a ureidosilane‐terminated polysulfone hard block with a carboranesilanol‐terminated carboranesiloxane oligomer. The resulting block copolymer exhibited thermoplastic elastomeric behavior. This unique polymer had excellent thermal stability up to 400°C.
Degradation of polymers subjected to radio‐frequency discharges in SF6
Authors: Gilbert Roland , Castonguay Jacques , Théorêt Antoine
Published: April 2003

Studies were conducted on the degradation reaction of polyethylene, poly(tetrafluoroethylene), and an expoxy resin resulting from the action of a 13.56‐MHz radio‐frequency (rf) discharge in SF6. The curves showing the temperature variations of the samples during the experiment suggest that this degradation process occurs in two distinct stages: in the first, the heat released by the electric discharge causes the thermal degradation of the polymers, whereas in the second, the volatile degradation products react in the gas phase with the excited SF6. Analysis of the reaction products shows consistency with this two‐step degradation model. The main degradation products have been identified as C2H2, C2H4, SOF2, and CS2 in the case of polyethylene; as CF4, C2F4, and SOF2 in the case of poly(tetrafluorethylene); and finally as CO2 and SOF2 in the case of the epoxy resin. Furthermore, it is interesting to note the formation of polymers of the di(trifluoromethyl) polysulfane type, CF3‐Sn‐CF3, among the reaction products. The more volatile members, n = 2, 3, and 4, were identified by mass spectrometry, whereas the heavier members, identified by infrared spectrophotometry, often took the form of a whitish powder deposited on the walls of the reactor.
Reactivity of N‐methylolacrylamide in treatment of cotton under ultraviolet light
Authors: Reinhardt Robert M. , Arthur Jett C.
Published: April 2003

N‐Methylolacrylamide (NMA) and cotton react readily under ultraviolet light when the treatment is carried out in an atmosphere of nitrogen. Reaction is almost completely inhibited by the oxygen in air. Polymerization inhibitors such as the methyl ether of hydroquinone (MEHQ) retard, but do not prevent, reaction. Longer radiation times, i.e., higher radiation doses, overcome the inhibitory effect of MEHQ. A photosensitizer such as biacetyl can increase the rate and efficiency of NMA‐cotton treatments, especially with short radiation times (low radiation doses). Relatively low ratios of photosensitizer to monomer produce such effects.
Cast and mold polymerization of organic glass by irradiation from fluid and soft gel prepolymers
Authors: Okubo Hiroshi , Yoshii Fumio , Nishiyama Sigeru , Yoshida Kenzo , Kaetsu Isao
Published: April 2003

Casting and mold polymerization processes were investigated by means of γ‐irradiation of methyl methacrylate prepolymer systems containing some quantity of polyfunctional monomers. Some physical properties, such as supercooling tendency and temperature dependence of viscosity and relaxation time in fluid prepolymers, were measured and related to cast polymerization at low temperatures. It was found that free‐state casting with no frame or mold was possible using viscous states of prepolymer in the supercooled state. Furthermore, efficient mold polymerization using soft gel prepolymer was studied. That is, plastic soft gel prepolymer was prepared conveniently by irradiation of fluid prepolymer, then molded into spherical or nonspherical curved surface shapes, and curved by reirradiation. Polymerization and gelation behavior of soft gel prepolymer and penetration degree of prepolymer as a measure of plasticity of gel were studied in relation to prepolymer composition and irradiation condition.
The kinetics of hydrolytic polymerization of ϵ‐caprolactam
Authors: Tai Kazuo , Teranishi Hiroichi , Arai Yoshihiro , Tagawa Takashi
Published: April 2003

A method to determine the concentration of ϵ‐aminocaproic acid (ACA) in poly‐ϵ‐caprolactam by high‐pressure liquid chromatography is established. The polymerizations for initial water concentrations of 0.42, 0.82, and 1.18 mol/kg and temperatures of 230, 240, 250, 260, 270, and 280°C were performed and concentration‐versus‐time curves were obtained for ACA, ϵ‐caprolactam (CL), and endgroups (EG). Each curve for ACA and EG has a maximum which increases monotonically in its value and shifts from right to left in position with increasing either the temperature or the initial water concentration. The reaction rates of CL, EG, and ACA were also evaluated numerically from the concentration data. The observed kinetic data were compared with those obtained by the numerical solution of the rate equations with Reimschuessel's kinetic constants. Good agreement is found in CL and EG concentrations but discrepancies in ACA concentration and rates are considerable, particularly in the early stage of the polymerization.
Permeabilität galvanisch beschichteter Polymerfolien. I. Methode zur Messung der Gaspermeabilität
Authors: Springer Jurgen , Brito Heide
Published: April 2003

The construction and function of an apparatus for the determination of gas permeability through metallized polymer films is described. The test gases N2, O2, and CO2 penetrate under pressure differences from 100 torr to 20 bar through galvanized ABS films (acrylonitrile–butadiene–styrene copolymer). The metallic layers consists of chemically deposited Ni and a galvanic deposited Cu having a thickness of 2–30 μm. The quantity of permeated gases is determined by gas chromatography. The lowest permeability coefficient obtained is 10−17 (cm3 cm/cm2 sec torr). Leak effects can be measured quantitatively. The permeability of gas mixtures (i.e., air) can also be investigated. The apparatus allows the determination of extremely low permeability rates as well as those for conventional polymer systems.
Dyeing of chemically modified cellulose. IV. Dyeing of oxidized celluloses with some reactive and direct dyes
Authors: Hebeish A. , Moursi A. Z. , Waly A. , El‐Rafie M. H.
Published: April 2003

Oxidation of cotton cellulose with potassium periodate, potassium dichromate‐sulfuric acid, and potassium dichromate‐oxalic acid results in creation of variable amounts of acidic and reducing groups along the cellulose molecule, being dependent upon the type of oxidizing agent used. Such groups were found to have a profound effect on the acceptability of cellulose for reactive and direct dyes. The rate and extent of dye uptake for the oxidized celluloses were significantly lower than those of the unoxidized cellulose. While presence of the acidic groups in cellulose molecules induces a negative environment thereby making approach of the dye anions to the cellulose difficult, presence of the reducing groups lowers the magnitude of cellulose reactivity as well as decreasing its adsorptive power. Further modification of the oxidized celluloses via either borohydride or chlorous acid treatment brought about modified celluloses the dyeability of which confirms the inhibiting effect of the acidic and reducing groups of those oxidized celluloses on the rate and extent of dyeing with reactive and direct dyes.
Degradation of polystyrene by gamma irradiation: Effect of air on the radiation‐induced changes in mechanical and molecular properties
Authors: Bowmer T. N. , Cowen L. K. , O'Donnell J. H. , Winzor D. J.
Published: April 2003

Irradiation of 3 mm polystyrene sheet in air at 30°C with γ rays caused a rapid decrease in the tensile and flexural strengths and strains to fracture. These properties were decreased to 50% of their initial values after ca. 80 Mrads and to 25% after ca. 200 Mrads, beyond which dose the rate of change was relatively small. These results contrast with the negligible changes that are observed after 600 Mrads in vacuum. The effect of irradiation in air has been correlated with decreasing molecular weight at the surface, even though crosslinking predominated over the complete sample so that a gel point was reached at a dose slightly in excess of 100 Mrads. Scission and crosslinking yields, G(S) and G(X), were determined as a function of depth by gel permeation chromatography of layers removed progressively from the surface. G(S) decreased and G(X) increased with depth, in accord with the concepts of increased scission by reaction with oxygen and a diffusion effect. Unusual transverse cracking to a limited depth occurred during tensile measurements, a phenomenon that is attributed to the nonuniform molecular weight profile.
Effect of fillers on kinetics of epoxy cure
Authors: Dutta A. , Ryan M. E.
Published: April 2003

The effect of fillers on the reaction of liquid epoxy systems cured with m‐phenylenediamine has been studied within the temperature range 70–170°C using a Perkin–Elmer differential scanning calorimeter. Quantitative studies have been made with regard to the effect of filler on the kinetics of cure. Mathematical expressions have been devised to describe the curing reaction as a function of time, temperature, and filler content. These kinetic expressions were found to yield results which were in good agreement with the experimental data for the two fillers studied.
Thermodynamics of gas solubilities in molten polymers
Authors: Liu D. D. , Prausnitz J. M.
Published: April 2003

Perturbed‐hard‐chain theory is extended to mixtures of polymers and volatile fluids, including supercritical gases. This extension is used to derive an expression for Henry's constant for a solute in a molten polymer. Theoretical calculations and data reduction are reported for a variety of solutes in polyethylene, polyisobutylene, and poly(dimethyl siloxane) in the temperature region 25–300°C. Calculated Henry's constants and their temperature dependence are generally in good agreement with the limited experimental data now available.
Mechanical and optical characterization of a photoviscoplastic material
Authors: Doyle James F.
Published: April 2003

The mechanical and optical properties of a polyester blend over a wide range of strain rates has been investigated for loading and unloading. The mechanical behavior, while being complex, was modeled adequately with a generalization of the four‐parameter viscoelastic model. The optical behavior has at least a three‐phenomenological coefficient dependence on the mechanical variables. Further, the stress birefringence is of opposite sign to that of the deformation.
A VSE equation of state for liquids. V. Poly(tetrafluoroethylene), 600–725 K
Authors: Doolittle Arthur K.
Published: April 2003

Our volume–entropy–energy (VSE) equation of state for liquids, first proposed in 1973 for use with low molecular weight homogeneous liquids, is here applied for the first time to a high molecular weight liquid that is heterogeneous in molecular weight, namely, a molten polymer. Four thermo‐dynamic quantities, T, s, cp, and ε are calculated over the range of 600–725 K at ambient pressure and are compared with experimental values, with excellent results. The grand average of the standard percentage errors (S.P.E.) for the 24 points is 0.1100%.
Mechanics of the extension of cotton fibers. I. Experimental studies of the effect of convolutions
Authors: Hearle J. W. S. , Sparrow J. T.
Published: April 2003

Cotton fibers have structure at many levels. This paper is concerned with the effect of gross convolutions on tensile properties. Experiments with rubber tubes show that convolutions result from the collapse of a twisted hollow tube. In cotton, the convolutions will reverse at the helix reversals. Extension of cotton fibers and of nylon models shows that the initial easy extension is due to the untwisting of convolutions. If the amounts of S‐ and Z‐twist are different, the lesser part will become completely untwisted. Fibers stretched in water and then dried are without convolutions and are stiffer. Optical and SEM observations illustrate the behavior.
Dynamic mechanical behavior of chlorosubstituted derivatives of poly(ethyl methacrylate) and poly(ethyl acrylate)
Authors: Kolařík Jan
Published: April 2003

A freely oscillating torsional pendulum was used in the investigation of the influence of trichloroethyl, tetrachloroethyl, trichloromethoxyethyl, and trichloroethoxyethyl side groups on the molecular mobility in the glassy state and on the glass transition temperature of poly(meth)acrylates. All the polymers under study, which may be used as fire retardants, exhibit a simple relaxation behavior. While the parameters of the low‐temperature and secondary relaxation process in the glassy state are not noticeably affected by the substituents used, the glass transition temperature Tg, increases with rising polarity and volume of side chains. The increase is larger in the series of polyacrylates, so that differences in the softening temperatures of polymethacrylates and polyacrylates having the same side chains decrease considerably with growing substitution.
Diffusion with simultaneous reaction of reactive dyes in cellulose. II. Effect of hydrolysis
Authors: Motomura Hiromi , Morita Zenzo
Published: April 2003

Theoretical equations that describe the concentration profiles of immobilized and active species for reactive dyes were derived from the diffusion equation accompanied by the reaction with cellulose and water in the substrate. The diffusion coefficient D and the rate constant of the reaction with cellulose, kcell, and that with water in cellulose, kw, were estimated by using the theoretical equations and the cylindrical film roll method. The theory predicted that the apparent diffusion coefficients decreased with the hydrolysis of active species in cellulose. Results from diffusion experiments with C.I. Reactive Yellow 4 and Orange 1 show that the ratio P of kw to kcell for Orange 1 increased with increase in pH to about pH 13 and that the P for Yellow 4 was smaller than unity. Using an alternative experiment to diffusion, P of Orange 1 was measured to be 1.0–1.5, and that of Yellow 4 was smaller than unity at pH 11.6 at 30°C. It was therefore concluded that the D of active species was constant to a highly alkaline region and that the decrease in the apparent diffusion coefficient of Orange 1 was mainly due to the hydrolysis of active species in cellulose.
A study of PVC stabilization with epoxides using dynamic pH determinations
Authors: Gonzalez‐Gonzalez V.
Published: April 2003

The activation energy (Ea) for the dehydrochlorination of PVC and PVC stabilized with an epoxide was determined by a method involving dynamic pH measurements. The Ea increase was 5 kcal/mole between unformulated PVC (Ea = 22.6 kcal/mole) and any of the other formulations (Ea = 27.7–28.6 kcal/mole). On the basis of this and data contained in the literature, research alternatives for the stabilization mechanism are proposed using model compounds.
Synthesis, photodegradation, and energy transfer in a series of poly(ethylene terephthalate–co–2,6‐naphthalenedicarboxylate) copolymers
Authors: Cheung Ping‐Sun R. , Roberts Carleton W. , Wagener Kenneth B.
Published: April 2003

Triplet–triplet energy transfer has been shown to occur from poly(ethylene terephthalate) (PET) units to the 2,6‐naphthalenedicarboxylate (2,6‐ND) monomer units in a series of poly(ethylene terephthalate–co–2,6‐naphthalenedicarboxylate) (PET–2,6‐ND) copolymers, as filament yarns, by an exchange mechanism at 77°K. The radius of the “quenching sphere” has been calculated to be 19.7 Å, indicating the presence of triplet energy migration. Photostabilization was observed in the copolymer yarns with the concentration of the monomer dimethyl 2,6‐naphthalenedicarboxylate (2,6‐DMN) at or above 2 mol %; the rate of phototendering in an air atmosphere was shown to decrease from 2.0 × 10−19% breaking strength loss/quantum absorbed/cm2 in the homopolymer PET to 0.7 × 10−19% breaking strength loss/quantum absorbed/cm2 in the copolymer yarns. The photophysical processes in the monomers, dimethyl terephthalate and 2,6‐DMN, were examined by absorption and luminescence studies. The lowest excited singlet and triplet in both monomers were identified to be the 1(π, π*) and 3(π, π*) states, respectively. The phosphorescence of PET was shown to originate from a 3(π, π*) state, while the complex fluorescence spectrum may arise from some oriented aggregates in the polymer matrix. In copolymer yarns, only the fluorescence emission from the 2,6‐ND monomer units at 380 nm was observed. The phosphorescence spectra of the copolymer yarns showed phosphorescence emissions from the PET and 2,6‐ND monomer units; in addition, delayed fluorescence from the 2,6‐ND monomer was also observed.
Solubility and diffusivity of bis‐(2‐chloroethyl)‐sulfide in polypropylene
Authors: Hjermstad Hans P.
Published: April 2003

Solubility and diffusivity have been determined for bis‐(2‐chloroethyl)sulfide in isotactic polypropylene at temperatures from 15 to 40°C and relative pressures from 0.34 to 1.00. While the solubility in films annealed above 90°C followed the normal variation with the amorphous content, the quenched film had a significantly lower amorphous volume fraction than determined from its density, 46 instead of 60%. The diffusion behavior in the film was found to be invariably Fickian and not dependent on the amorphous volume fraction of the polymer between 0.34 and 0.46. The solubility was found to be independent of the temperature over the range 15–40°C, but dependent on the diffusant concentration. The isotherms were well represented by the Flory‐Huggins relation for crosslinked polymers, and values for the interaction constant and the average molecular weight between crystallites have been obtained. The value of the interaction constant, μ = 1.13, is an expression of the low affinity bis‐(2‐chloroethyl)sulfide has for polypropylene. The intrinsic diffusivity was only weakly dependent on the diffusant concentration. The results were found to be in agreement with Fujita's free‐volume theory. The apparent activation energy for the diffusion of bis(2‐chloroethyl)sulfide in isotactic polypropylene was found to be 22.5 kcal/mol.
Stability of continuous emulsion polymer reactors
Authors: Chiang Anthony S. T. , Thompson Robert W.
Published: April 2003

The stability of continuous emulsion polymer reactors having steady feed streams was studied. Analysis of a population balance model supported the notion of micelle deprivation as the chief cause of reactor instabilities. Analysis of the moments of the distribution indicated that the system may be uniquely stable in one case. Only one steady‐state operating point was predicted for the case where the decrease in the termination rate constant due to the gel effect was neglected.
Statistical study of the application of the huggins equation to measure intrinsic viscosity
Authors: Reilly Park M. , Van Der Hoff B. M. E. , Ziogas M.
Published: April 2003

Intrinsic viscosities of polymers are most often estimated using the Huggins equation, which relates the quotient ηsp/c to intrinsic viscosity and concentration c. It is shown that when this method is used, the error structure is distorted by the presence of concentration in the quotient. The result is that when dilution series experiments are analyzed, the estimates are ordinarily poorer the more dilutions are made. A rearrangement of the Huggins equation is introduced which allows precise estimation from any experiment. It is also shown that dilution series experiments with more than three different concentrations including that of the pure solvent are inefficient by any method of analysis, and convenient experiments which may be considered practical optima are described. When they are used the conventional analysis is restored to full efficiency. Design and analysis of experiments where there is important uncertainty in polymer concentration are also studied.