bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution of some physical properties in injection‐molded thermoplastic parts
Authors: Bakerdjian Z. , Kamal Musa R. 
Published: December 2004

AbstractDuring the injection molding process, moldings undergo shear and elongational stresses. They are also exposed to thermal gradients of varying intensity. Invariably, molded parts, or at least some sections thereof, freeze before the polymer chains can relax to a random, non‐oriented configuration. As a result, injection molded parts contain frozen strains and exhibit anisotropic physical properties. In the present work, a variety of experimental techniques have been employed to determine the three‐dimensional variation of the following properties of injection‐molded, thermoplastic, rectangular parts: density, heat shrinkage, birefringence, and tensile strength.
Parameters, affecting the sensitivity of poly(methyl methacrylate) as a positive lithographic resist
Authors: Gipstein Edward , Ouano Augustus C. , Johnson Duane E. , Need Omar U. 
Published: December 2004

AbstractThe contribution of parameters such as molecular weight, molecular weight distribution and stereochemistry to electron beam sensitivity of poly(methyl methacrylate), PMMA, has been investigated. The sensitivity is interpreted here as the minimum radiation dose required to obtain a predetermined solubility rate ratio, S/So = SR, of the exposed, S, and unexposed, So, material. The G‐value was foam be independent of molecular weight, molecular weight distribution, and stereochemistry. Data indicate that the weight average molecular weight ratio correlates better with SR than the number average molecular weight ratio. The tacticity of the resist and the developer solvent molecular weight or size have a large effect on solubility rate. Although the solubility rate pf isotactic PMMA is much greater than the syndiotactic and heterotactic stereoforms, the sensitivity appears to be independent of tacticity. In a homologous series of n‐alkyl acetate developer solvents, the molecular size of the solvent has a greater effect on the solubility rate than the molecular weight of the resist. A developer solvent has been selected from the n‐alkyl acetates which enhanced the sensitivity of PMMA.
The synthesis, characterization, evaluation, and processing of selected cyclo‐olefin sulfone copolymers as electron beam resists
Authors: Himics R. J. , Kaplan M. , Desai N. V. , Poliniak E. S. 
Published: December 2004

AbstractThe potential usefulness of electron beam sensitive polymers depends to a large extent on a variety of polymer characteristics such as solubility, sensitivity, and processability which are, in turn, required by the application. This paper details results obtained for methylcyclopentene sulfone copolymers as electron beam recording media. The determination of physical properties and the optimization of processing conditions are reported.
Thermally‐reacted poly(methacrylamide) as a positive electron beam resist
Authors: Matsuda S. , Tsuchiya S. , Honma M. , Hasegawa K. , Nagamatsu G. , Asano T. 
Published: December 2004

AbstractThermally‐reacted poly(methacrylamide) degrades under high‐energy irradiation. It has a sensitivity of 2‐3 × 10−7 C/cm2 when exposed to 10 KV electrons. The resist is thermally stable to 330°C and has a high glass transition temperature, 180 200°C. It may be used for the lift‐off process and ion‐milling.
Limiting surface tension by gas chromatography
Authors: Braun J.‐M. , Guillet J. E. 
Published: December 2004

AbstractThe change in retention mechanism at the glass transition temperature (Tg) of a polymer stationary phase from surface adsorption below Tg to bulk sorption above Tg allows for a separate determination of the magnitude of the solute interaction with both the bulk and the surface of the polymer. As a result, the limiting surface tension of the polymer‐probe solution can be obtained from the corresponding partition coefficients. Examples of such determinations are given for several polymer‐solute systems.
Diffusion and solution of gases and vapors in styrene‐butadiene block copolymers
Authors: Odani Hisashi , Taira Kazuo , Nemoto Norio , Kurata Michio 
Published: December 2004

AbstractThe diffusion, solution, and permeation behavior of a series of inert gases (helium, argon, nitrogen, krypton, and xenon) in S‐B block copolymer films was studied by transient permeability measurements and by the equilibrium desorption method. The morphologies of most of the samples used in the measurements were (a) polystyrene rods dispersed in a polybutadiene matrix and (b) alternating lamellae of styrene and butadiene components. It was indicated, as far as the kinetic nature at lower temperatures is concerned, that the diffusion and permeation processes of gases, except for helium, are governed primarily by behavior in the polybutadiene matrix. At lower temperatures, it was shown that the transient method counts only the mobile penetrant in the polybutadiene matrix, while the equilibrium method counts less diffusive species in the polystyrene domains as well. The diffusion behavior in the copolymer films was compared with that in homopolybutadiene and discussed in terms of two impedance factors: the tortuosity and the chain immobilization factors. From the homopolymer‐block copolymer comparison along with results obtained from diffusion experiments using n‐hexane as the penetrant, it was indicated that segmental motions in the polybutadiene phase in the copolymers are restricted relative to motions in homopolybutadiene. Also, from data on gas sorption in samples of various styrene contents, involving both S‐B block copolymers and binary mixtures with homopolystyrene, it was suggested that the partial mixing of component block chains occurs at the interface between the domains, resulting in rather diffuse domain boundaries.
Glass bead‐filled polypropylene part I: Rheological and mechanical properties
Authors: Faulkner D. L. , Schmidt L. R. 
Published: December 2004

AbstractFive glass bead‐filled polypropylene composites were rheologically characterized at 240°C using two rotational rheometers to obtain low shear‐rate data and a capillary rheometer to obtain high shear‐rate data. Both steady and dynamic properties were measured at low shear rates. Each composite was also injection molded into tensile and flexural test bars for a mechanical properties profile at 25°C. The tensile modulus was determined from a simple extensional deformation whereas the flexural modulus was determined from a three‐point‐bend test.The relative shear viscosity and relative loss modulus are different nonlinear functions of the volume fraction of beads at a constant shear rate, while the relative storage modulus appears to be a linear function of bead fraction. The relative viscosity decreases with increasing shear rate and the zero shear‐rate data are in very good agreement with the Guth‐Gold equation.The relative tensile modulus and relative flexural modulus are each linear functions of bead fraction over the entire range of filler concentration, 0‐29 vol percent. From these data it is concluded that a simple correspondence between slow viscous flow and small strain elasticity does not exist for these composites.
A study of the effect of pressure, time, and temperature on high‐pressure powder molding
Authors: Bigg D. M. 
Published: December 2004

AbstractHigh pressure room temperature molding of polymeric powders has been found to be a useful technique for producing parts from certain hard‐to‐process polymers and certain common polymers. Polymeric powders of less than 175μ were compacted at pressures up to 0.689 GPa. Subsequent heat treating of the compacted samples improves the mechanical properties of the samples to levels comparable to those attained by other techniques. Thermosetting or reactive polymers which do not evolve vapors during curing are readily processed by this technique. Semicrystalline polymers which are molded above their Tg are also easily processed by this method. Glassy polymers, in general, have not been found to be processable. The important process variables are molding pressure, molding time and heat treating temperature and time. The process relies on particle‐to‐particle fusion by either chemical reaction or localized melt fusion. For semicrystalline polymers, the annealing temperature is within the melting endotherm. Reactive polymers cure at their optimum curing temperature.
Olefin‐SO2 copolymers as biomaterials
Authors: Gray D. N. 
Published: December 2004

AbstractThe series of olefin‐SO2 copolymers prepared from the C8‐C18 even‐numbered carbon series of alpha‐olefins and sulfur dioxide have been studied. The C16 polymer especially has high gas permeability, good biocompatibility, low, toxicity, low thrombogenicity, ease of fabrication and potential low cost. Maximum permeabilities, maximum percent elongation at the yield point and minimum density are obtained with the C16 based polymer. An explanation is proposed involving a competitive plasticizing/side chain crystallization effect.
On the effect of mechanical energy on the degradation of polyethylene in the solid state and in the melt
Authors: Holmström Arne , Andersson Arne , Sörvik Erling M. 
Published: December 2004

AbstractThe influence of mechanical forces on structural changes in commercial grades of high and low density polyethylenes was investigated by using extremely high shear rates (>2 × 104S−1) during processing in a special injection molding machine and by long‐term loading at ambient temperature. Changes in molecular weight distribution (MWD) and the degree of long‐chain branching (LCB) were followed by gel permeation chromatography and viscometry. No effect of the mechanical forces was observed either in the long‐term loading or in the processing. At temperatures exceeding 280°C the small changes noted in MWD and LCB wrere found to be entirely due to thermal de radation.
Effects of post‐curing of unsaturated polyester resins in various media
Authors: Chen Show‐An , Tsai Pai‐Kuen 
Published: December 2004

AbstractExperimental studies were performed on the effects of postcuring of' styrenated, unsaturated polyesters in nitrogen gas, water or its vapor, hexane vapor, dimethyl sulfoxide (DMSO), and dirnethyl formamide (DMF) all at 100°C It was found that, nitrogen gas and water are inactive, hexane acts as a chain transfer agent, and DMF and DMSO behave as solvents which extract residual styrene monomer and anhydrides from the resins. Post‐treatment in inert media can result in further reaction leading to more complete cure as free radicals and residual monomer continue to react. The post‐curing reaction is a radical copolymerization. Further condepgation polymerisation does not occur. Post‐curing in, hexane vapor1eads to a transfer of the active sites from the radicals to the hexane and to no further radical polymerization.
Light stabilization of flame retardant impact polystyrene
Authors: Bradley Richard , Farber Joseph , Testa Lawrence 
Published: December 2004

AbstractThis paper presents the results of a study onn the effectiveness of ultraviolet absorbers and light stabilizers in preventing the discoloration of flame retardant impact polystyrene. The deleterious effect of certain flame retardants, i.e., aromatic or aliphatic halogenated compounds, on the light stability of this polymer is shown. Light stabilizer systems resulting in substantially improved color stability during light exposure are presented. The beneficial effect df co‐additives, including antioxidants, acid acceptors, epoxies, phosphites, and thiosynergists, on light stability is also discussed.
Cobalticenium‐Bridged polybenzazoles. Part II: High‐temperature. Solution polymerization in ethylated polyphosphoric acid
Authors: Neuse Eberhard W. , Horlbeck Gernot 
Published: December 2004

AbstractThe polycondensation of 1,1′‐diearboxycobalticenium hexafluorophosphate with 3,3′‐diaminobenzidine in ethylated poly phosphoric acid at 100‐240°C furnishes linear, soluble polymeric intermediates for the most part composed of cobalticenium‐1,1′‐diyl and bibenzimidazoline‐2,2′‐diyl units alternating along the chain. Heating of the primary products in the solid state at 300°C results in aromatization, giving polyheterocyclics essentially composed of alternating cobalticenium‐1,1′‐diyl and bibenzimidazole‐2,2′‐diyl units. The analogous reaction of the cobalticenium salt with 3,3′dimercaptobenzidine produces primary polymers containing benzothiazoline in lieu of benzimidazoline ring systems, which, by a heat treatment as before, convert to the corresponding polymeric benzothiazoles. The primary condensation products of both reaction types are of low molecular mass (ηinh, 5‐13 ml/g) vlien prepared at temperatures not exceeding 150°C. The degree of polymerization increases (ηinh, 20‐60 ml/g) at temperatures in the 200‐250°C range; however, Lewis acid‐induced cobalt‐ring bond cleavage proceeds as a significant side reaction under these conditions, leading to random chain scission and alteration of the polymer structure by alicvclic hydrocarbon groups. In addition, the benzimidazole polymers are to a variable extent contaminated with phosphate groups stemming from the medium. These structural defects, paired with distinct reactivity of the PF6‐ anion at higher temperatures, result in a thermogravimetric analysis performance not quite equal to that of common phenylene‐bridged Polybinzazoles.
Influence of melt deformation history on orientation in vitrified polymers
Authors: Oda Kunio , White James L. , Clark Edward S. 
Published: December 2004

AbstractAn experimental study of the development of orientation in polystyrene melts during flow and its retention in vitrified parts is described. It is shown on the basis of elongational and shear flow experiments that orientation in vitrified polystyrenes may be predicted from a knowledge of the stress field at the time of vitrification and application of stress‐optical laws. More generally a relationship between birefringence and principal stress difference is found which correlates (1) on‐line isothermal shear flow, (2) on‐line non‐isothermal elongational flow (melt spinning), and (3) vitrified samples formed in both shear and elongational flow. It is further proposed that orientation in polymer chains in deforming melts is uniquely dependent on stress—specifically, that the ratio of the stress‐optical constant C to the intrinsic birefringence Δ° is approximately a constant.
Flammability characteristics of fiber reinforced organic matrix composites
Authors: Silvergleit M. , Morris J. G. , Larosa C. N. 
Published: December 2004

AbstractThe effect of resin, fiber, and fire retardant additives on flammability characteristics of organic matrix composites was evaluated. Information is presented on the flame spread index, determined by the radiant panel test, the amount of smoke generated, and products of combustion, using the National Bureau of Standards Smoke Density Apparatus, and the amount of oxygen required to support combustion using the Oxygen Index method. These methods were effective in screening the flammability characteristics of organic matrix composites. Of the materials evaluated the polyimide composites were the most resistant to flame spread, exhibited the lowest evolution of smoke and toxic products and had the highest oxygen index. No differences in flame spread and oxygen index were observed for the polyester epoxy glass‐cloth laminates. Addition of antimony trioxide and hydrated alumina to the polyester and epoxy resin systems significantly decreased the flame spread index and increased the oxygen index, but showed a marked increase in smoke evolution. Smoke properties depended on resin content whereas the type of reinforcement did not appear to affect flame spread index or smoke properties. The use of protective barriers in selected shipboard areas can reduce flame spread and lengthen the lime for generation of smoke.
Static behavior and the effects of thermal cycling in hybrid laminates
Authors: Liber T. , Daniel I. M. , Chamis C. C. 
Published: December 2004

AbstractThe influence of hybridization with stacking sequence variation on static stiffness, strength, ultimate strain and residual properties after thermal cycling of graphite/Kevlar 49/ epoxy and graphite/S‐glass/epoxy angle‐ply laminates was investigated. Tensile stress‐strain curves to failure and uniaxial tensile properties were determined for all laminates. Theoretical predictions of modulus, Poisson's ratio and ultimate strain were made, based on linear lamination theory, constituent ply properties and measured strength. Reasonably good agreement was found. Stacking sequence variation showed no significant systematic influence on the measured results. Specimens containing only two 0‐degree Kevlar or S‐glass plies behaved linearly to failure. Specimens containing four 0‐degree Kevlar or S‐glass plies displayed characteristic non‐linearity. One group of laminates was subjected to a tensile load and to 100 thermal cycles between room temperature and 280°F, and another group to a tensile load and 100 thermal cycles between room temperature and −100°F. All surviving specimens were tested statically to failure to determine residual properties which were compared with the properties of uncycled specimens. Specimens containing two Kevlar or two S‐glass plies behaved linearly to failure. Residual moduli in these specimens were lower than for uncycled specimens but residual strengths and ultimate strains were higher. Specimens with four Kevlar or four S‐glass plies showed some nonlinear behavior. No significant differences were found between residual and uncycled values for modulus and strength.
Crystal nucleation in sheared polymer melts
Authors: Andersen P. G. , Carr S. H. 
Published: December 2004

AbstractA semiquantitative procedure has been developed for analyzing crystal nucleation in undercooled polymer melts that are undergoing flow. This analysis was applied to the specific ease of molten high density polyethylene experiencing low levels of shearing flow. A custom‐made concentric cylinder viscometer, which could be operated by the Rheometrics mechanical spectrometer instrument, was used to make simultaneous measurements of transmitted torque and optical anisotropy in isothermal melts, The result of the analytical procedure developed here was molecular Size‐dependence of chain distensions caused by prevailing shear. This distribution function was verified by testing against experimentally obtained values of birefringence. Total entropy reduction resulting from this distorted state was then calculated, and the corresponding increase in free energy was found to be at least enough to account for comparable crystal nucleation rates in flowing melts at higher temperatures and in quiescent melts at lower temperatures.
The effect of annealing on the mechanical anisotropy of cold rolled polyoxymethylene
Authors: Bahadur Shyam 
Published: December 2004

AbstractThe effect of cold rolling and subsequent annealing on the anisotropy of tensile properties has been studied by annealing 33 percent cold rolled polyoxymethylene at 70, 120 and 170°C and measuring the properties at 0, 45 and 90° from the rolling direction. The mechanical and thermal treatments exhibit a significant effect on the directional nature of the properties. The changes in mechanical properties have been accounted for in terms of the changes in morphology, fracture behavior and orientation as studied by a differential thermal analyzer, electron microscopy and wide‐angle X‐ray diffraction.
The effect of extrusion on the mechanical properties of polytetrafluoroethylene paste
Authors: Coleman C. J. 
Published: December 2004

AbstractWe consider the connection between viscous effects experienced by polytetrafluoroethylene paste during extrusion, and the final strength of the extrudate. It is shown that by reducing the viscous contribution to the pressure drop across the extruder die, we not only save on extrusion pressure, but also increase the strength of the extrudate. The shape of die that gives the minimum pressure drop is derived.
Influence of glass fibers on the extrusion and injection molding characteristics of polyethylene and polystyrene melts
Authors: Chan Yu , White James L. , Oyanagi Yasushi 
Published: December 2004

AbstractA basic study is reported of extrusion and injection molding for melts of polyethylene and polystyrene filled with glass fibers. It is shown that glass fibers cause large increases in end pressure losses and decreases in extrudate swell. Flow visualization of injection molding studies indicates that polymer melts containing high loadings of glass fibers exhibit jetting in end gated molds. This is attributed to the reduction in extrudate swell. To avoid jetting, special care is required in design of gating.
Factors influencing the impact strength of high impact polystyrene
Authors: Pi Chang Eng , Takahashi Akio 
Published: December 2004

AbstractThe relationship between synthesis factors and the impact resistance of high impact polystyrene (HIPS) is investigated in the light of its morphology and dynamic mechanical properties. A decrease in polymerization temperature results in an increase in Tg, melt viscosity and molecular weight of the continuous polystyrene phase as characterized by gel permeation chromatography. The separated, occluded polystyrene phase however shows an invariant Tg suggesting that the grafting and/or crosslinking effect overweighs the molecular weight effect. The observed high impact strength has been correlated with the homogeneous 1‐2 μ rubber particle size distribution, a comparatively sharp rubber Tg transition at lower temperature, and a much lower occluded polystyrene content in the dispersed phase.
Vinyl chloride formation from the thermal degradation of poly(vinyl chloride)
Authors: Wakeman I. B. , Johnson H. R. 
Published: December 2004

AbstractThe volatile products from the thermal degradation of poly(vinyl chloride) (PVC) resins and compounds are shown to contain trace amounts of vinyl chloride. Data presented show the effect of temperature and resin type on the amount of vinyl chloride formed. At the maximum temperatures involved in PVC processing which may reach 210°C., vinyl chloride monomer (VCM) evolution amounts to less than 1 ppm (resin basis). A technique employing a thermogravimetric balance and charcoal adsorption of volatiles is described for studying thermal degradation of PVC. The volatiles are analyzed for vinyl chloride by gas chromatography. Peak identity was confirmed by mass spectrometry.
Tensile deformation of nylon 6 fibers
Authors: Oilman T. H. , Resetarits M. R. , Crist B. 
Published: December 2004

AbstractNylon 6 fibers which had been relaxed to different extents by annealing were examined at fixed strains by small angle and wide angle X‐ray techniques. It was found that the strain of the long period of the semicrystalline microfibrils is identical to the macroscopic fiber strain. Approximately 1/3 of the tensile deformation results from molecular shear of imperfectly oriented crystalline chains. Virtually no evidence for intercrystalline slip is found; the orientation of the intercrystalline amorphous regions results in a low compliance for the shear of crystals past one another. The majority of the microfibril deformation occurs by stretching these intercrystalline amorphous regions, accompanied by the flow of extrafibrillar amorphous material to maintain constant volume. In highly annealed fibers this “filling” mechanism is less efficient, as the amount of extrafibrillar material has been reduced during shrinkage. This effect leads to a decrease in Poisson's ratio after increasingly severe annealing. A related result of annealing is the dehomogenization of the microstructure, leading to the presence of more stress‐induced “microcracks” during the stretching of annealed fibers.