bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of sorbed penetrants on the aging of previously dilated glassy polymer powders. II. n‐propane sorption in polystyrene
Authors: Stewart M. E. , Hopfenberg H. B. , Koros W. J. , McCoy N. R. 
Published: April 2003

AbstractBoth the rate and apparent equilibrium of propane sorption in glassy polystyrene were increased after swelling the polymer by exposure to a highly sorbing vapor. Cyclic sorption experiments revealed that the increase in rate and apparent equilibrium of sorption due to the preswelling treatment decayed only during vacuum aging. The presence of low levels of propane in the polymer during aging, however, appeared to arrest the decay in sorption capacity. These composite results, taken in conjunction with the results of previous work in our laboratory, suggest that the component of the total sorption which resides in nonequilibrium, distended interchain gaps retards the chain motions which otherwise lead to consolidation of the dilated glass.
Thermal behavior, morphology, and the determination of the Flory–Huggins interaction parameter of polycarbonate–polystyrene blends
Authors: Kim Woo Nyon , Burns Charles M. 
Published: April 2003

AbstractBlends of bisphenol‐A polycarbonate (PC) and polystyrene (PS) prepared by screw extrusion and solution casting have been investigated with weight fractions of PC in the blends varying from 0.95 to 0.05. From the measured glass transition temperatures (Tg) and specific heat increments (ΔCp) at the Tg, the polystyrene appears to dissolve more in the PC phase than does the PC in the PS phase. The blend appears to be near eqilibrium under extrusion conditions so that the polymer–polymer interaction parameter of PC/PS blends was calculated and found to be 0.038±0.004 for extruded blends at 250°C. Scanning electron microscopy supports the conclusion that the compatibility increases more in the region of PS‐rich compositions than in the regions of PC‐rich compositions of the PC/PS blends.
Gas permeation in miscible homopolymer–copolymer blends. I. Poly(methyl methacrylate) and styrene/acrylonitrile copolymers
Authors: Chiou J. S. , Paul D. R. 
Published: April 2003

AbstractGas transport properties in homogeneous blends of PMMA with each of two SAN random copolymers, containing 13.5 and 28% by weight of acrylonitrile respectively, have been measured at 35°C for He, H2, O2, N2, Ar, CH4, and CO2. For all cases, the permeability and diffusion coefficients are higher than that expected from the semilogarthmic additivity rule. On the other hand, the solubility coefficients and the ideal gas separation factors follow this rule well. These results for PMMA/SAN blends differ from those observed recently for other miscible blend systems; however, they agree well with recent theories proposed to describe gas sorption and permeation behavior in polymer mixtures. The composition dependence of gas transport properties observed in PMMA/SAN blends is attributed to the very weak net interactions between PMMA and SAN produced by repulsions between styrene and acrylonitrile units in the SAN random copolymers. Gas transport properties in phase‐separated PMMA/SAN blends have also been studied. The phase‐separated blends show sorption and permeation properties very similar to the corresponding homogeneous blends which can be explained by an isotropic, interconnected, two‐phase model proposed by Kraus and Rollmann. Gas permeabilities for the solution cast PMMA films used here are compared with melt‐extruded specimens used previously, and the differences are attributed to molecular orientation.
Strain birefringence of Kevlar aramid fibers
Authors: Yang H. H. , Chouinard M. P. , Lingg W. J. 
Published: April 2003

AbstractWe have measured the strain birefringence of Kevlar aramid fibers under static loading via a spectrophotometric method. At very low strain rates, the birefringence of Kevlar fibers increases markedly with increasing strain. On initial straining, the birefringence increases even at relatively constant modulus. This is attributed to the orientation of macroscopic species in the fiber which were observed by visible light microscopy. Such behavior is supported by the experimental observation of laser diffraction patterns and optical transmission images of Kevlar fibers under load. In the final stage of straining where the fiber modulus increases rapidly, the birefringence increase is attributable to crystalline orientation. The spectrophotometric method is useful for the simultaneous measurement of stress, strain, and birefringence of highly oriented, highly crystalline fibers such as Kevlar aramid. It is particularly useful to study the morphological inhomogeneity of a fiber which is undetectable by the conventional tensile test.
Influence of emulsifiers on film formation from cellulose acetate latexes experimental study of phase separation phenomena due to sodium dodecyl sulfate. I
Authors: Bindschaedler C. , Gurny R. , Doelker E. 
Published: April 2003

AbstractCellulose acetate membranes prepared from latexes containing sodium dodecyl sulfate as a stabilizer were found to undergo phase separation. This phenomenon was studied by different techniques including autoradiography, optical and scanning electron microscopy, mechanical testing, and liquid water permeation. The concentration of sodium dodecyl sulfate in the dry membranes was found essential in controlling their structure and properties, as well as the nature and amount of plasticizer incorporated in the latex system. The method of preparation and the drying duration were also relevant. Depending on whether films were produced by casting or spraying, tensile and permeation values exhibited quite different responses to variations of the sodium dodecyl sulfate content. In Paper II, a thermodynamic framework is proposed that accounts for the redistribution of sodium dodecyl sulfate into small islets, and thus for phase separation.
Crystallization behavior of polybutene‐1 in the anisotropic system blended with polypropylene
Authors: Takahashi T. , Nishio Y. , Mizuno H. 
Published: April 2003

AbstractDevelopment of supermolecular structure in drawn polypropylene (PP)/polybutene‐1 (PB‐1) blends was studied. PP (matrix)/PB‐1 (70/30) blend films were drawn and heat‐treated at fixed length or free ends at temperatures above the melting point of PB‐1. It was found that a long axis of the PB‐1 lamella is aligned perpendicular to the draw direction, and the c‐axis of the PB‐1 crystal is oriented perpendicular both to the draw direction and the plane of the surface of the blend film. Drawn, then heat‐treated PP/PB‐1 blend films gave a SAX pattern having a cross type scattering maximum on the meridian. It was confirmed that vertical scattering originates from the PB‐1 crystal developed during melt recrystallization. It was proposed that the structural development of PB‐1 in drawn PP/PB‐1 film can be explained on the basis of transcrystallization of PB‐1 in the confined 2‐dimensional space in the PP matrix. The kinetics of isothermal crystallization of PB‐1 was examined by use of a DSC technique. The result supports the conclusion that the heterogeneous nucleation of PB‐1 followed by 2‐dimensional crystal growth prevailed in oriented PP/PB‐1 blend film.
Influence of molecular weight distribution on the linear viscoelastic properties of polymer blends
Authors: Han Chang Dae 
Published: April 2003

AbstractLiterature data for the dynamic viscoelastic properties of binary blends of nearly monodisperse polybutadienes, polystyrenes, and poly(methyl methacrylate)s was analyzed using logarithmic plots of dynamic storage modulus G′ versus loss modulus G″, based on a recent theoretical study by Han and John.28 It has been found that for binary blends of monodisperse polymers with molecular weights M much greater than the entanglement molecular weight Me, the value of G′ in log G′ − log G″ plots becomes independent of molecular weight, increases sharply as small amounts of a high‐molecular‐weight component are added to a low‐molecular‐weight component, and passes through a maximum G′max at a critical blend composition (ϕ2)max, and that G′max becomes larger and (ϕ2)max becomes smaller as the ratio of component molecular weights increases. However, as the molecular weight distribution of the constituent components becomes broader, the effect of blend composition on G′ in log G′ − log G″ plots becomes less pronounced. This observation has enabled us to explain why log G′ − log G″ plots of binary blends of commercial polymers, namely, blends of two low‐density polyethylenes, blends of poly(ϵ‐caprolactone) and poly(styrene‐co‐acrylonitrile), and blends of poly(methyl methacrylate) and poly(vinylidene fluoride), all having broad molecular weight distributions, give rise to values of G′ between those of the constituent components. When one of the constituent components has molecular weight smaller than Me, while the other has molecular weight larger, and as small amounts of the high‐molecular‐weight component are added to the low‐molecular‐weight component, log G′ − log G″ plots of binary blends give rise to values of G′ larger than those of the constituent components at low values of G″, but approaches the value of G′ for the low‐molecular‐weight component as the value of G″ is increased. However as the amount of the high‐molecular‐weight component is increased above a certain critical composition, binary blends give rise to values of G′ close to that of the high‐molecular‐weight component at all values of G″. The experimentally observed dependence of G′ on blend composition in log G′ − log G″ plots is favorably compared to the theoretical prediction of a blending law proposed by Montfort and co‐workers.14,15
Polymer compatibility and interpolymer association in the poly(acrylic acid)–polyacrylamide–water ternary system
Authors: Eustace D. J. , Siano D. B. , Drake E. N. 
Published: April 2003

AbstractPolyacrylamide and poly(acrylic acid) form a water‐insoluble phase when solutions of the two having concentrations that are not too low are mixed. The insoluble complex contains nearly stoichiometric 1 : 1 ratios of acrylamide and acrylic acid. The phase behavior of the ternary system was studied as a function of the degree of neutralization, α, of poly(acrylic acid). The complex is not formed when α is high. The formation of the complex was studied by measurement of pH increases observed when poly(acrylic acid) was titrated with polyacrylamide to infer a degree of linkage, θ, between the two polymers. A Hill plot of the data showed that the association was cooperative when the molecular weight was high.
Quantitative size exclusion chromatography of polypropylene I: Method development
Authors: Lew R. , Suwanda D. , Balke S. T. 
Published: April 2003

AbstractPolypropylene was analyzed by size exclusion chromatography (SEC) at 145°C using a single‐differential refractometer detector. The objective was to provide data for characterization of polypropylene degradation during a reactive extrusion process. Two antioxidants [tetrakis(methylene(3,5‐di‐tert‐butyl‐4‐hydroxyhydrocinnamate)) methane (I) and octadecyl 3,5‐di‐tert‐butyl‐4‐hydroxyhydro cinnamate (II)] were tested for their ability to prevent thermal degradation of the polypropylene during sample preparation. The use of 0.20 wt% of (I) was effective during the 36–48 h required to completely dissolve the samples in trichlorobenzene for SEC analysis. “Reshaping” of the chromatograms by resolution correction demonstrated that, while the molecular weight averages were changed by 8% because of axial dispersion, most of the individual heights of the distributions were changed by less then 2%. Tail heights of the distributions were more affected but were also shown to be highly imprecise. Selecting individual heights of the distributions rather than molecular weight averages therefore minimized axial dispersion error and also circumvented errors in molecular weight averages originating from dilution of distribution tails below detector sensitivity limits. Various forms of distributions were examined and the equations linking the chain length distribution predicted by polymerization kinetic models to the SEC chromatogram are presented. The analytical method developed provided precise data for kinetic modeling. However, absolute accuracy requires further assessment.
New model for the high modulus and strength performance of ultradrawn polyethylenes
Authors: Zachariades Anagnostis E. , Kanamoto Tetsuo 
Published: April 2003

AbstractA new morphological model is discussed which is based on the relation of tensile modulus and strength to the macrofibrillar dimensions (aspect ratio) and the shear modulus of ultrahigh molecular weight polyethylene fibrillar structures of draw ratio DR ≤ 200–300. Such structures were obtained by solid state deformation of the as‐received powder and solution grown crystals using an extrusion‐drawing process. According to this model, the highest tensile modulus and tensile strength values that can be obtained are 212 GPa and 13.3 GPa, i.e., significantly close to the theoretically calculated values.
Thermal and dynamic mechanical properties of polyurethaneureas
Authors: Hartmann Bruce , Duffy James V. , Lee Gilbert F. , Balizer Edward 
Published: April 2003

AbstractMeasurements were made of the thermal and dynamic mechanical properties of 22 polyurethaneureas of varying diol molecular weight, type of aromatic chain extender, diol molecular weight distribution, and chain extender stoichiometry. The dynamic mechanical data, obtained as a function of temperature and frequency (in the kHz region), were used to construct master curves of shear modulus and loss factor over a wide range of reduced frequencies. Based on these master curves, interpreted in conjunction with the thermal analysis results, it was found that: Soft segment crystallization occurs at the higher diol molecular weights, dynamic mechanical properties are well correlated with the soft segment glass transition, diol molecular weight influences dynamic mechanical properties by affecting the degree of phase separation and hence glass transition temperature, and neither diol molecular weight distribution nor chain extender stoichiometry have a significant effect, in the ranges studied, on transition temperatures or dynamic mechanical properties.
Charged ultrafiltration membrane for permeation of proteins
Authors: Miyama Hajime , Tanaka Kouichi , Nosaka Yoshio , Fujii Nobuyuki , Tanzawa Hiroshi , Nagaoka Shoji 
Published: April 2003

AbstractPolyacrylonitrile‐g‐poly(N,N‐dimethylaminoethyl methacrylate) was synthesized photochemically and quaternized. The positively charged membranes made from the quaternized graftcopolymer showed high ultrafiltration rate for water by adding poly(vinyl alcohol) to casting solution and washing it out after the casting. In buffered saline solution, the permeability of the membranes was very small at pH below isoelectric point of albumin but increased markedly at higher pH. On the other hand, the permeability for γ‐globulin was very small and did not show any pH dependence.
Studies on the solvent exchange technique for making dry cellulose acetate membranes for the separation of gaseous mixtures
Authors: Lui A. , Talbot F. D. F. , Fouda A. , Matsuura T. , Sourirajan S. 
Published: April 2003

AbstractThe effect of the pore size on the surface of the water‐wet reverse osmosis membrane and the solvents used in the solvent exchange process on the pore size of the resulting dry cellulose acetate membrane was studied with respect to the separation of a CO2/CH4 mixture. It has been found that there is a critical pore size on the surface of wet membrane that results in the smallest pore size on the dry membrane and, consequently, in the highest separation factor. Such critical pore sizes become greater when the boiling point of the second solvent is increased.
Diffusion of organic penetrants through low density polyethylene (LDPE) films: Effect of size and shape of the penetrant molecules
Authors: Saleem M. , Asfour Abdul‐Fattah A. , De Kee D. , Harrison Brian 
Published: April 2003

AbstractThe diffusion coefficient at zero penetrant concentration D0 of dichloromethane, chloroform, carbon tetrachloride, cyclohexane, benzene, o‐xylene, m‐xylene, and p‐xylene, and n‐hexane in LDPE were measured at 25°C, using the desorption method. The D0 values obtained in this way are correlated with the size, shape, and chemical nature of the penetrant molecules. The temperature dependence of the diffusion coefficients of toluene and n‐hexane in LDPE are also reported in the limited temperature range of 25–45°C. It indicates that, in spite of a size larger than that of toluene, n‐hexane has a lower activation energy of diffusion.
Acrylic nonaqueous dispersion using butylated melamine‐formaldehyde resin as dispersant
Authors: Miyauchi Noriyuki , Kusahara Masataka , Motomura Toshiro , Akashi Mitsuru 
Published: April 2003

AbstractA series of acrylic nonaqueous dispersions were prepared by using various kinds of butylated melamine–formaldehyde (BMF) resins as dispersant. The functional group composition of BMF to form stable dispersion was butoxy group more than 13 mol/BMF 1 mol, and methylol group ranged from 1 to 2.5 mol/BMF 1 mol. It is concluded that the anchoring of BMF to acrylic copolymer was due to the formation of covalent bond between methylol group in BMF and hydroxy group in acrylic copolymer.
The effects of annealing and aging in water on the properties of an amorphous copolyester
Authors: Golovoy A. , Cheung M. F. 
Published: April 2003

AbstractThe influence of annealing in a dry oven and aging in water bath at 98°C on the thermal and mechanical properties of an amorphous poly(1,4‐cyclohexandimethylene/ethylene terephthalate) was studied up to 21 days. Oven annealing brought about crystallization, an increase in the tensile modulus and yield strength, and a decrease in elongation and Izod impact strength. The intrinsic viscosity, however, did not change. The samples that were immersed in water embrittled at a faster rate as a result of the combined adverse effects of hydrolysis and crystallization. The intrinsic viscosity decreased from 0.71 to 0.53 after 21 days. Within the limits of this study, the hydrolysis was found to be a zero‐order process with respect to molecular weight. A transition from ductile (> 8% elongation) to brittle failure in tension was observed between 3 and 5 days.
Liquid crystalline acrylic copolymers for high‐solids enamel coatings
Authors: Chen Der‐Shyang , Jones Frank N. 
Published: April 2003

AbstractCarboxyl functional liquid crystalline (LC) acrylic copolymers were synthesized and were compared with carboxyl functional control copolymers of M̄n about 5000–15,000. Both types were crosslinked with a hexakismethoxymethyl melamine (HMMM) resin at 150°C, a temperature below the clearing points of the LC copolymers. Birefringent phases were visible in the crosslinked films made from LC polymers. FT‐IR indicated the presence of unreacted COOH in all crosslinked materials. Unreacted COOH groups in crosslinked LC copolymers appeared only slightly higher than those in crosslinked amorphous copolymers. The potential utility of these LC copolymers as binders for thermosetting coatings was assessed. Variables studied were HMMM content, the length of PHBA grafts, Tg and M̄n of the acrylic copolymer backbone, and functionality. Optimum LC copolymers have low backbone Tg (<O°C) and low functionality (< 7.5 mol %). Cured films of such copolymers have both high hardness (> 35 KHN), high impact resistance (> 80 in. ib), excellent adhesion, and good solvent resistance.
Functional group efficiency in adhesion between polyethylene and aluminum
Authors: Hjertberg T. , Lakso J.‐E. 
Published: April 2003

AbstractThe effect of different functional groups on the adhesion between polyethylene and aluminum has been studied. Poly(ethylene‐co‐butyl acrylate) (EBA) and poly(ethylene‐co‐vinyl acetate) (EVA) were used as such and provided polyethylene surfaces with two different kinds of ester groups, butyl ester and acetate, respectively. By alkaline hydrolysis in an organic solvent the surface functionality could be changed to carboxylate and hydroxyl, respectively. Finally, acid washing converted the carboxylate groups into carboxylic acid. The effect of the surface treatments were followed by reflection IR. T‐peel tests of laminates made of the original, as well as the surface‐treated polymers, and aluminum allowed an evaluation of the specific contribution to the adhesion for the groups in question. The peel strength increased linearily with the bulk concentration of comonomer in the original EBA and EVA samples. The values increased from about 100 N/m for polyethylene up to 2500 N/m in the case of 3.7 mol % of carboxylic acid. The efficiency of the investigated functional groups increased in the following order: H<OCOCH3 <COOC4H9 <COONa∼OH<COOH.
Structural features of poly(alkylene ether carbonate) diols and intermediates formed during their preparation
Authors: Harris Robert F. , McDonald Lynn A. 
Published: April 2003

AbstractCapillary vapor‐phase chromatography and carbon‐13 nuclear magnetic resonance (NMR) have been used to elucidate the structure of poly(ethylene ether carbonate) diols and certain intermediates produced by the oligomerization of ethylene carbonate (EC) using monoethylene glycol (MEG) or diethylene glycol (DEG) as initiator and catalyzed by sodium stannate trihydrate. These diols are alternating copolymers of carbon dioxide and DEG which also contain smaller amounts of higher glycols as determined by comparing their 13C NMR spectra to the spectra of model compounds. Diethylene glycol is an important reaction intermediate and is present in steady‐state concentrations. Although both 2‐hydroxyethyl carbonate and 2‐hydroxyethyl ether end groups are present at an intermediate stage in the reaction, only 2‐hydroxyethyl ether end groups are present at high EC conversion. Molecular weight builds as a smooth function of conversion and time.
Preparation of block copolyetheramides and their properties as hot melt adhesives
Authors: Hu Andrew Teh , Tsai Ruey‐Shi , Lee Yu‐Der 
Published: April 2003

AbstractBlock copolyetheramides were prepared by incorporating polyether into polyamide through melt polycondensation of polyetherdiamine, piperazine, dimer acid, and ε‐caprolactam. Bulk properties of block copolyetheramide, such as tensile strength, tensile modulus, elongation at break, hardness, and impact strength, were evaluated with respect to composition. Investigation on the lap shear strength and T‐peel strength of block copolyetheramide hot melt adhesive showed that the lap shear strength was more composition‐dependent. Moisture and elevating test temperature also reduced the lap shear strength significantly.
Pyrolysis‐field ionization mass spectrometry of polyamide copolymers and blends
Authors: Plage Bernd , Schulten Hans‐Rolf 
Published: April 2003

AbstractNylon foils of PA 6, PA 66, PA 69, PA 12, the copolymer PA 666, and nine blends based on these polymides have been investigated by in‐source pyrolysis (Py)–field ionization mass spectrometry (FIMS). These polymers and blends can be distinguished by characteristic molecular ions of oligomers, protonated amines and nitriles, and products terminated by olefinic end groups. Series of ions are formed differing in the number of additional monomeric units. Thus, polymers containing different chemical subunits were easily distinguished from each other in the spectra of the blends. Mass signals, only expected for copolymers, were found in the integrated blend spectra, indicating that amide exchange reactions occur under the experimental conditions employed. This observation was confirmed by pyrolysis of mixtures of pure polymers in the same crucible and under the same experimental conditions. Hence, the distinction by Py–MS alone between blends and copolymers with an identical averaged number of identical chemical subunits is not possible.