bluuebunny/crossref_metadata_2025_split huggingface dataset:
The coupled relaxation model for toner melt rheology
Authors: Karis T. E. , Seymour C. M. , Jhon M. S. 
Published: May 2005

AbstractProcess changes aimed at improving printer engine performance must take into consideration not only the process variables (such as nip temperature and pressure and process time to), but also the melt rheological variables (such as the characteristic time scale of the toner Tc). The melt rheology relevant to the electrophotographic toner fusing process is discussed. One criterion for toner quality can be conveniently measured through the Deborah number De, which is the ratio of Tc to to. Modification of the melt rheology by matrix polymer composition and carbon black size and concentration has previously been explored. Here, the melt rheology of toners with a range of gel content was studied using a step shear test. The coupled relaxation model was employed to fit the stress relaxation data. The viscoelastic properties were calculated from the melt data with this model. These properties were then used to estimate the strain deformation of the toner as it passes through the nip with arbitrary residence time and nip pressure as a function of gel content. This method can be used to match the toner melt properties with the processing conditions.
Rubber toughening of poly(methyl methacrylate). Part I: Effect of the size and hard layer composition of the rubber particles
Authors: Wrotecki C. , Heim P. , Gaillard P. 
Published: May 2005

AbstractPoly(methyl methacrylate) (PMMA) is a brittle material which can be reinforced by the incorporation of acrylic particles, which do not spoil the transparency but which considerably increase the toughness of the material. In that study, we have varied the particle size and the outer layer for anchoring with the matrix. The proportion of reinforcing material is kept constant and the particles have an elastomeric core structure and a hard outer layer of PMMA. Monitoring of the two parameters, the critical stress intensity factor KIC and the critical energy release rate GIC, which are given by the fracture mechanics under static and dynamic (impact) loading, has made it possible to establish an optimum size of the reinforcement of the order of 200 to 250 nanometers. This optimum size can be explained as being the best compromise between the initiation of the damage and the control of its propagation, and that makes it possible to avoid a premature catastrophic failure. It also appears that a higher degree of grafting and a higher molecular mass of the hard layer result in an improved toughness.
Rubber toughening of poly(methyl methacrylate). Part II: Effect of a twin population of particle size
Authors: Wrotecki C. , Heim P. , Gaillard P. 
Published: May 2005

AbstractRubber toughened poly(methyl methacrylate) (PMMA) is reinforced efficiently by particles of a size of the order of 200 to 250 nm in the case of acrylic particles of core‐shell structure. In this study we have attempted to detect a possible synergy effect related to the presence of a twin population of particle sizes, as has already been observed, for example in high impact polystyrene. Two pairs of particle sizes were studied: (82,203) and (130,520) nm. The determination of the fracture mechanics parameters KIC and GIC under static and dynamic loading has enabled us to demonstrate a synergy effect in the case of the critical energy release rate GIC at a proportion of 50/50. Furthermore, this effect is verified in the case of the two pairs of particle sizes and in the case of the two speeds of loading. Nevertheless, this effect remains smaller than those observed in the case of materials which deform by crazing (HIPS, ABS). The rubber toughened PMMA deforms by shear bands and this mode of deformation seems to be less adapted to promote a synergy effect due to a twin distribution of particle sizes.
Measurement of the equibiaxial elongational viscosity of polystyrene using lubricated squeezing
Authors: Hsu T. C. , Harrison I. R. 
Published: May 2005

AbstractThe equibiaxial elongational viscosity of polystyrene was determined using a lubricated squeezing technique. Constant strain rates up to Hencky strains of 4.5 could be maintained by a newly constructed instrument. Test results from controlled stress and controlled strain rate measurement were consistent and yielded well‐defined steady‐state viscosities. Measurements appeared to be unaffected by sample geometry, although proper lubrication is important in achieving steady state. The measured biaxial viscosity appeared to be strain rate thinning above a biaxial strain rate of ≈ 0.01 s−1 at 160°C. As anticipated in the Newtonian region, biaxial elongational viscosity was approximately six times the shear viscosity. Thinning indices of both shear and biaxial elongational viscosities were 0.75. Data obtained at various temperatures were shifted following the timetemperature superposition principle. The resulting master curve could be fitted by a Carreau model with n ≈ 0.3 and a time constant of 110 s.
Effect of talc surface treatment on the mechanical properties of composites based on PP/LDPE blend matrices
Authors: Ramos M. Arroyo , Berna M. Sanchez , Matheu J. P. Vigo 
Published: May 2005

AbstractA study has been made of property optimization of a composite based on low density polyethylene and polypropylene (PP) blend matrices with talc modified by a titanate coupling agent. Analysis shows that the flexural properties improve with increasing content of both talc and polypropylene. However, the tensile moduli show a different behavior. Tensile strength is hardly affected by the filler content at PP percentages in the matrix above 50 percent. The surface modified talc gives rise to higher mechanical properties than the unmodified talc. This improvement is more noticeable as talc and PP percentages in the composite is increased. Scanning electron microscopy has shown the effect of the coupling agent at the filler/polymer matrix interphase and the greater affinity between talc and polypropylene.
Dynamic mechanical analysis of polymeric systems in liquid environments
Authors: Dillman S. H. , Seferis J. C. 
Published: May 2005

AbstractDynamic mechanical properties of polymer systems immersed in liquid environments have the potential of providing a wealth of characterization information relating to durability and performance characteristics of the material. However, when oscillatory experiments are performed in liquids, the effect of fluid drag on the sample and/or clamps must be subtracted from the data if the true material properties of the polymer are to be measured. Using classic dimensional analysis, a correlation was developed for calculating the friction of a sample/clamps combination in different liquids In relation to a Reynolds number defined for the immersed system. The methodology was adapted to the DuPont DMA using a poly(tetrafluoroethylene) (PTFE) polymer sheet to avoid any liquid sorption by the sample. It was found that storage and loss friction parameters could be determined and subtracted from the measured data to provide fluid‐independent dynamic mechanical properties for the sample.
The low temperature response of slit‐seals in low density polyethylene thin films
Authors: Simpson Michael , Bowman Jeremy 
Published: May 2005

AbstractThe low temperature mechanical strength and the modes of failure of low density polyethylene (LDPE) films and hot air slit‐seals have been assessed. Seven different LDPEs were blown into thin films (∼30μm) and slit‐sealed on‐line, both the extrusion and sealing being undertaken using commercial equipment. When pulled in tension transverse to the extrusion direction, both the films and the slit‐seals exhibited a ductile response at the higher temperatures, while at lower temperatures brittle failures were seen. The ductile‐to‐brittle transition temperatures were reasonably well defined with the slit‐seal embrittling at significantly higher temperatures. The low temperature mechanical performance of LDPE films containing slit‐seals is thus controlled by the seal. However, by using seven different LDPE resins with a range of melt flow rates, it was seen, that the low temperature response was enhanced with the low melt flow rate resins. Informed materials selection can therefore enable manufacturers to produce LDPE products containing slit‐seals with good low temperature strength.
Structure and mechanical properties of optimized extrusion welds
Authors: Gehde Michael , Ehrenstein Gottfried W. 
Published: May 2005

AbstractA knowledge of how welding parameters affect the mechanical properties of welds is important. However, the mechanical properties of welds cannot be characterized by nondestructive testing methods. Because of its sensitivity to process conditions, extrusion welding of polypropylene‐homopolymer (PP‐H) was used to investigate the effects of welding parameters on the resulting mechanical properties of welds. Overall optimization of the welding process to obtain stable conditions during welding, which required a redesign of the welding shoe and the welding geometry, resulted in improved weld properties through better build‐up of critical weld areas and suppression of void formation. Investigation of material heating characteristics led to a new air nozzle design. The effect of air temperature and welding velocity on the temperature and thickness of the molten layer was determined. The effects of individual process parameters on the structure and mechanical behavior of welds were established, thereby making it possible to specify narrow limits on the values of the weld parameters for producing high‐quality welds. The quality of these joints cannot be determined by short‐time tests because, even with severe testing conditions, cracks occur in the bulk material. Polarized optical microscopy was used to correlate crack behavior with the build‐up of a specific multilayer structure in the weld area. Long‐term tests demonstrated that, in both the time‐to‐crack and crack behavior, the joining area is not the weakest link in an extrusion weld when the welding parameters are chosen correctly.
Strength model of adhesive bonded composite pipe joints under tension
Authors: Griffin S. A. , Pang S. S. , Yang C. 
Published: May 2005

AbstractA theoretical model is developed to predict the strain of the pipe, coupling, and adhesive under tensile loading of an adhesive bonded joint. The model is found to be within 10 percent of the experimental pipe and coupling strain. Based on the model, several failure modes and their locations are defined and related to the measured data. In this investigation, delamination is the dominating mode of failure. The delamination stress for each test sample is within 7 percent of the average theoretical delamination stress. In addition, the effect of the coupling length, coupling Young's modulus, adhesive shear modulus, and adhesive thickness on the delamination failure are investigated. The model shows that decreasing the modulus of the coupling improves the delamination failure load; however, the coupling strain at the middle of the joint is increased by this variation. Increasing the shear modulus of the adhesive provides the most significant improvement of the joint delamination failure load. Two geometric factors, the joint length and the adhesive thickness also affect the joint failure load. The joint delamination failure load can only be significantly improved by increasing the bonding length up to a certain limit. Increasing the adhesive thickness increases the delamination failure load, however, a large gap between the pipe and coupling may contribute to misalignment during installation which may result in imposed moments under tensile loading. This study can supply the manufacturers with the appropriate design parameters to improve the joint performance significantly under tensile loading.
Characterization of agglomerate dispersion by erosion in simple shear flows
Authors: Rwei S. P. , Manas‐Zloczower I. , Feke D. L. 
Published: May 2005

AbstractThe extent of dispersion of solid agglomerates in hydrodynamic flow fields is believed to depend on the material properties as well as flow conditions. The purpose of this study has been to investigate the mechanism of agglomerate breakup in simple shear flows and to correlate the various parameters affecting the dispersion process. Experiments were performed in a transparent cone and plate device. Two distinct breakup mechanisms, denoted as “rupture” and “erosion”, were observed. The rupture process is characterized by an abrupt breakage of the agglomerate into a few large pieces. The erosion process is more gradual and initiates at lower applied shear stresses than rupture. The erosion process is characterized by the detachment of small fragments from the outer surface of the agglomerate. For the erosion of carbon black agglomerates suspended in Newtonian fluids, it was found that the kinetics of the process follows a first order rate equation and the size of the eroded fragments obeys a normal distribution. The strength of the flow field does affect the kinetics of the dispersion process, and a parameter α, scaling the applied shear stress with the cohesive strength of the agglomerate, is characteristic for the erosion process.
Polymerization of methacrylic acid and acrylonitrile by p‐nitrobenzyl triphenyl phosphonium ylide
Authors: Vasishtha Rita , Srivastava A. K. 
Published: May 2005

AbstractRadical polymerization of methacrylic acid (MAA) and acrylonitrile (AN) in the presence of p‐nitrobenzyl triphenyl phosphonium ylide (p‐NBTPy) in dimethyl sulphoxide at 65 ± 0.1°C under inert atmosphere was investigated by dilatometry. The ylide failed to initiate the polymerization, but significantly accelerated the rate of polymerization. An interesting feature is that the average polymer molecular weight (M̄v) is a direct function of [p‐NBTPy]. The radical polymerization of MAA follows ideal kinetics since calculated monomer and initiator (AIBN) exponents are unity and 0.5, respectively. However, the AN system follows non‐ideal kinetics due primarily to radical termination and transfer reactions. The energy of activation, in the presence of p‐NBTPy, is low. The accelerating effect of p‐NBTPy has been attributed to decreased termination because the ylide did not affect the rate of decomposition of AIBN, as well as form a complex with monomer(s).
Instrumented dart impact evaluation of linear low density polyethylene at controlled impact energy
Authors: Liu T. M. , Baker W. E. 
Published: May 2005

AbstractInstrumented impact testing of linear low density polyethylene (LLDPE I) (ethylene and 1‐octene copolymer) was carried out using a Rheometrics Drop‐Weight Tester (RDT‐5000). A method of partial penetration at controlled impact energy was used and developed. The set impact speed was raised step by step in small intervals of 0.25 m/s over a range of 0.76 m/s to 9.14 m/s. The impact deformation profiles of LLDPE I were obtained for a series of specimens impacted at different speeds. The stress states of the LLDPE I during the corresponding impact events were obtained with the instrumented impact tup. By comparing the observed impact profile with the force‐displacement trace, the yield point and the initial failure point of LLDPE I were assessed. The point of 100 percent of the maximum load on the force‐displacement trace of a total penetration impact was shown to be the yield point. On the basis of the determination of the yield point, a parameter, ductile ratio (D.R.), was redefined to characterize the ductility of polymers. The initial break point of LLDPE I was determined. The effect of specimen thickness and test temperature on the impact properties was investigated.
Flamesprayed thermoplastic powder coatings
Authors: George Eric R. , Reimer James 
Published: May 2005

AbstractThe effects of flamespray coating conditions on two ethylene‐carboxylic acid copolymers (Primacor 1420 and Nucrel 535) and a polyether block amide (Pebax 5533) on crystallinity and mechanical properties were investigated by differential scanning calorimetry (DSC), Gardner impact resistance, and conical mandrel bend tests. Plastic flamespray provides a means to apply thermoplastic powder coatings in the field with a wide range of properties to meet specific application requirements. The flamespray process did not significantly affect the crystallinity in the polymers studied, however, polymers possessing functional groups in the backbone such as the polyether block amide may experience some reduction in physical properties during the flamespray coating process. We have also successfully applied some high temperature thermoplastics (such as liquid crystal polymers) providing for coatings, with outstanding temperature and chemical resistance.
Critical ion concentrations for clusters in sodium sulfonated polystyrene lonomers
Authors: Park Jung‐Ki , Park Byung‐Kyu , Ryoo Ryong 
Published: May 2005

AbstractThe critical ion concentration of sodium sulfonated polystyrene ionomer has been investigated by glass transition, NMR and viscosity measurements. It was found that the critical ion concentration was affected by the molecular weight. The critical ion concentration could be explained by using the linewidths and chemical shifts of 23Na+ NMR spectra. The 23Na+ linewidths of the ionomer solution increased with ion concentration, which could be explained in terms of a shift in the association‐dissociation equilibrium between the Na+ and the counter‐ion group of the polymer side chain. The reduced viscosity behavior also showed a consistent critical ion concentration.
Incorporation of surface‐modified UHMWPE powders and fibers in tough polyurethane composites
Authors: Williams M. A. , Bauman B. D. , Thomas D. A. 
Published: May 2005

AbstractUltrahigh molecular weight polyethylene (UHMWPE) powder (60 micron diameter) and chopped fiber (6.5 mm length) were surface treated with a blend of reactive gases (fluorine and oxygen.) These powders and fibers were then compounded into a thermoset polyurethane matrix. Surface‐treated and control reinforcements are compared at a 10 vol.% loading level. Tensile testing indicates improved stress transfer with surface treatment. Stress transfer is also improved with fibers versus powders. Fracture toughness is characterized by measuring the essential work of fracture, we. Surface‐treated fiber composites exhibit work of fracture values almost three times the unfilled polyurethane values. Abrasion resistance was also measured. Surface treatment was found to significantly lower wear rates of powder composites. Fiber composites had lower wear rates than powder composites, although surface treatment had little effect. An approximate inverse relationship was found between wear rate and essential work of fracture.
Integrated simulation to predict warpage of injection molded parts
Authors: Matsuoka Takaaki , Takabatake Jun‐Ichi , Koiwai Akihiko , Inoue Yoshinori , Yamamoto Satoru , Takahashi Hideroh 
Published: May 2005

AbstractInjection molding analysis programs were developed for CAE (Computer Aided Engineering) in injection molding of thermoplastics. The programs consist of mold cooling, polymer filling‐packing‐cooling, fiber orientation, material properties and stress analyses. These programs are integrated to predict warpage of molded parts by using a common geometric model of three dimensional thinwalled molded parts. The warpage is predicted from temperature difference between upper and lower surfaces, temperature distribution, flow induced shear stress, shrinkage, and anisotropic mechanical properties caused by fiber orientation in the integrated simulation. The integrated simulation was applied to predicting warpage of a 4‐ribbed square plate of glass fiber reinforced polypropylene for examination of its validity. Predicted saddle‐like warpage was in good agreement with experimental one.
Advanced process control for injection molding
Authors: Smud Silvia M. , Harper Dean O. , Deshpande Pradeep B. , Leffew Kenneth W. 
Published: May 2005

AbstractThis paper deals with the application of advanced control strategies to an injection molding process. Of particular interest is the control of one variable during the cooling phase of the molding process. Due to the cyclic dynamic nature of injection molding, the controlled variable must be regulated over a short cycle; the full process is completed within 10 seconds. Therefore, a key control objective is rapid setpoint regulation. A closed‐loop strategy has been implemented for the regulation of pressure within the mold during the cooling cycle. First order plus dead time models of the process have been identified from plant step responses. The performance of several control algorithms for this process are compared in simulation studies. These algorithms have given comparable regulatory and servo responses. Finally, the effectiveness of the closed loop controi system has been demonstrated experimentally using the PI algorithm. Simulated and experimental results are in excellent agreement.
Effect of crystallization conditions on the morphological structure of ethylene‐1‐butene copolymers obtained by different ziegler‐natta catalyst systems
Authors: Pérez E. , Benavente R. , Bello A. , Pereña J. M. , Aguilar C. , Martínez M. C. 
Published: May 2005

AbstractFour ethylene‐ 1 ‐butene copolymers of about the same comonomer content but obtained with different supported Ziegler‐Natta catalyst systems have been studied. The effects of the catalyst and the crystallization conditions on the morphological structure have been analyzed. These two factors'clearly affect the melting endotherms and the most probable crystallite thickness of the copolymers, although no important differences were found in the crystalline contents. The catalyst system influences the melting pattern due to changes in the chemical composition distribution, i.e., variations in the comonomer content between chains of different molecular weight.
Phase morphology characterization and ultimate mechanical properties of 60/40 PC/SAN blend: Influence of the acrylonitrile content of SAN
Authors: Quintens D. , Groeninckx G. , Guest M. , Aerts L. 
Published: May 2005

AbstractThe tensile stress‐strain properties of blends having a 60/40 weight ratio of polycarbonate of bisphenol‐A (PC) and styrene‐acrylonitrile copolymers (SAN) have been investigated for a range of SAN copolymers with different AN levels. It is clearly demonstrated that the phase morphology of these, blends and the acrylonitrile (AN) content of the SAN component are important factors with respect to the ultimate mechanical properties (tensile strength and elongation at fracture). Following injection molding, a very fine phase distribution is observed for blends with SAN components containing 15 to 29% AN. By annealing of the blends at 200°C, i.e. above Tg(PC), it has been possible to obtain different degrees of domain sizes. From this range of morphologies, quite similar phase structures can selected differing only in AN‐content of the SAN blend components. This allows a systematic investigation of the effect of the AN‐content on the tensile stress‐strain. Properties of PC/SAN blends. The elongation at fracture exhibits an optimum for blends with SAN containing 24% AN. A coarsening of the phase morphology only results in a decrease of the ductility and not in a shift of the optimum. The maximum tensile stress exhibits a sigmoidal trend as a function of the AN‐content. This parameter remains constant for a typical ‐PC/SAN blend with different morphologies.