bluuebunny/crossref_metadata_2025 huggingface dataset:
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

A 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

Dynamic 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

The 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

A 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

A 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

The 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

Radical 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

Instrumented 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

The 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

The 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

Ultrahigh 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

Injection 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

This 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

Four 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

The 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.
Nylon/Kevlar composites. II: Investigation of interfaces
Authors: Yu Z. , Ait‐Kadi A. , Brisson J.
Published: May 2005

The aim of this article was the investigation of the fiber‐matrix interface of nylon/Kevlar composites. Both washed fibers and chemically treated fibers were used as reinforcements for nylon‐6 and nylon‐l1. Improvements of the mechanical properties were related to the increase in the nucleating abilities of the fibers, which was modified considerably by chemical treatments. Differential Scanning Calorimetry (DSC), X‐Ray diffraction, optical microscopy, and scanning electron microscopy were used to investigate the interface between the matrix and the fibers. The chemical treatments performed on the Kevlar fibers were found to affect the size of the transcrystalline zone and its crystal structure.
Morphology and mechanical performance of polyphenylenesulfide carbon fiber composite
Authors: Caramaro L. , Chabert B. , Chauchard J. , Vu‐Khanh T.
Published: May 2005

This paper presents the influence of fibers on crystallization kinetics and on matrix morphology for poly(phenylene sulfide)/carbon composite. The following parameters were also considered: thermal stability, fusion/crystallization conditions and surface treatment of carbon fibers. In order to correlate these results with mechanical properties, composite samples were prepared and tested in both static and dynamic modes. The delamination resistance of the composite in shear Mode II is also discussed.
Impact damage resistance of graphite/epoxy laminated composites
Authors: Choi Hyung Yun , Chang Fu‐Kuo
Published: May 2005

Damage in graphite/epoxy laminated composites resulting from low‐velocity impact was studied. The impact damage mechanisms and mechanics were first investigated by adopting the impactors with a line‐nosed head from which the damage was simplified from a complicated three‐dimensional pattern to a two‐dimensional one. Based on the results of the line‐loading impact study, a model was developed for predicting the impact damage in the materials resulting from point‐loading impact. The model consists of a stress analysis for calculating transient dynamic stresses during impact and a failure analysis for predicting the extent of delaminations resulting from the impact. A computer code, “3DIMPACT”, was developed based on the model during the investigation. The predictions from the code agreed fairly well with the test data.
Fluorescence monitoring of twin screw extrusion
Authors: Bur Anthony J. , Gallant F. Mitchell
Published: May 2005

An optical fiber probe has been constructed in order to obtain real‐time measurements of fluorescence radiation during twin screw mixing and extrusion of plasticized polybutadiene and calcium carbonate particulate. The probe consists of an optical fiber bundle which was inserted along the axis of a half‐inch sensor bolt, and it was used to transmit optical excitation energy to the processed material and to detect the subsequent fluorescence. The source of fluorescence radiation was a fluorescent dye which was doped into the processed ingredients at very low concentrations. Although most of our measurements were taken with the probe positioned close to the exit die, the sensor bolt can be placed in any instrumentation port along the extruder line. Experiments were carried out to measure residence time distribution, quality‐of‐mix, and mix concentrations as a function of processing conditions. Product mix changes in response to variations in material feed rates and screw RPM were also observed. Values of residence time were obtained by measuring the transit times for the dye to travel from an upstream injection port to the measurement probe, a distance of 63 cm. Flow instabilities, such as mat formation of the solids, were observed by noting the abrupt changes and discontinuities in the fluorescence signal.
Parametric study of a 2‐d model of the nip region in a counter‐rotating, non‐intermeshing twin screw extruder
Authors: Bigio David , Zerafati Saeid
Published: May 2005

Within the polymer processing industry, the demand for more efficient mixing within the existing mixer geometries and keeping a tighter control over increasingly difficult applications calls for a quantitative understanding of the role of the mixer geometry on the mixing performance. An important extruder geometry to consider is the Counter‐Rotating, Non‐Intermeshing Twin Screw Extruder (CRTSE). Recent studies suggest that the greater than linear mixing performance in this geometry may be attributed to the flow in the nip region. Solution of the fluid dynamic equations for a 2‐D model of the nip region was found in order to quantify mixing using a FEM software called FIDAP which was available to us on the CRAY X‐MP supercomputer at San Diego Supercomputer Center. In order to study the effects of design parameters in the nip region, an arbitrary interface was placed in the entrance of the region. A program called “LINE” tracks the path and growth of the interface through the region. Measures of mixing are computed and compared. Effect of several design parameters on mixing performance are studied. Conclusions are presented as to the relative effect of various design parameters. Discussions regarding the measures of mixing and mixing efficiency are presented.
Isothermal and dynamic reaction kinetics of high performance epoxy matrices
Authors: Kenny J. M. , Trivisano A.
Published: May 2005

The reaction kinetics of the epoxy matrix of a commercial prepreg for high performance composites, based on tetraglycidyl diamino diphenyl methanediamino diphenyl sulfone (TGDDM‐DDS) formulation, has been characterized by differential scanning calorimetry (DSC). A phenomenological kinetic model, able to describe the behavior of the system during normal processing operations has been formulated. The diffusion control phenomena, related to the evolution of the glass transition temperature as a function of the degree of polymerization, has been considered in the formulation of the kinetic model. Isothermal and dynamic tests have been used to calculate the model parameters and to verify the proposed model. The model is able to describe incomplete reactions in isothermal tests and heating rate dependence of dynamic test thermograms, and it has been also successfully applied to DSC experiments performed with complex thermal conditions commonly used in the processing of high performance composites.
Effects of thermoplastic additives on the cure of unsaturated polyester resins
Authors: Hsu C. P. , Kinkelaar M. , Hu P. , Lee L. James
Published: May 2005

Thermoplastic additives tend to promote the phase separation during the reaction of unsaturated polyester resins. Consequently, they reduce the amount of shrinkage during curing. Several thermoplastic additives which resulted in significant different microstructure of cured resins were investigated. The effects of microstr acture formation on the sol‐gel transition, reaction kinetics, and gelation time were studied. The mechanism of microstructure formation and causes of macro‐gelation were explained by the influence of thermoplastic additives on the particle formation rate and inter‐particle reaction rate during curing.
Application of compensation phenomena to the thermal analysis characterization of polymers: Introducing the degree of disorder (DOD) number:
Authors: Ibar J. P.
Published: May 2005

The objective of this article is to show that a deconvolution of the globalTgrelaxation peak obtained by thermal stimulated current characterization technique leads to a better understanding of the coupling characteristics between the relaxation modes. The degree of coordination, i.e., coupling, is function of the state of the system and is revealed by the compensation phenomenon characteristics. In a compensation phenomenon, Arrhenius lines gather into packs of lines which converge to a single point, “the compensation point”. The coordinates of the compensation point are dependent on the actual state of the glass. We find that plots of the thermo‐kinetic variables against the polarization temperatureTp, whenTpvaries, leads to characteristic results of the Relaxation Map:Tgis characterized by a maximum of the Entropy of activation (and of the enthalpy of activation), and also by the existence of two compensation lines, one positive one negative, which intercept forTp=Tg. The relaxation map looks like a “Z” acrossTg, as the Arrhenius relaxation lines gather into either a positive or negative compensation. We introduce a new method to characterizeTg, and to determine, from theZ‐structure, the activation entropy ΔSg, and the activation enthalpy ΔHgatTg.
Effects of polymer structure on the onset of processing defects in linear low density polyethylenes
Authors: Karbashewski E. , Rudin A. , Kale L. , Tchir W. J. , Schreiber H. P.
Published: May 2005

Linear low density polyethylenes are manufactured by copolymerizing ethylene with 1‐alkenes, yielding a linear polyethylene backbone with short side chains. Due to the nature of the catalyst used in the polymerizaton, multimodal branching distributions are typically obtained. In this report, we have investigated the processability of four 1‐octene linear low density polyethylenes as a function of the short chain branching distribution. Analytical techniques such as 13C nuclear resonance spectroscopy, size exclusion chromatography, differential scanning calorimetry, and temperature rising elution fractionation, in particular were used to elucidate the molecular structure. Processability measurements were made using various extrusion techniques and dynamic mechanical analyses.It was determined that in the absence of any variations in molecular weight, the polymers with the higher proportions of linear polyethylene showed inferior processability In terms of onset of surface imperfections at lower extrusion rates. Polymers with worse processability characteristics also exhibited higher zero shear viscosities.
Shear and elongational viscosities of a thermotropic liquid crystalline polymer and its blend with polycarbonate
Authors: Beery D. , Kenig S. , Siegmann A. , Narkis M.
Published: May 2005

The shear and elongational viscosities of a thermotropic liquid crystalline polymer (LCP), polycarbonate (PC), and their 20%LCP/80%PC blend, were studied using a capillary rheometer. The investigation focused on experimental studies using two sets of capillaries. The first set comprised capillaries having a converging entrance followed by a cylindrical section. The second set, “zero length” set, included capillaries having only the converging section. In the two sets various entrance angles were used. Experimental results have shown that shear viscosities and entrance pressures are practically independent of the entrance angles. The entrance pressure drop was small in the case of PC and reached 50% of the total pressure drop for LCP. The elongational viscosities of the LCP were found to be higher than those of the PC in the elongational‐rate range studies, while shear viscosities of the LCP were higher in the lower shear rate region and lower in the higher shear rate region compared to those of PC. This was attributed to the orientability of LCP in elongational and shear flows.
Reduction in domain size in polymer mixtures via charge transfer interactions
Authors: Clark J. N. , Higgins J. S. , Peiffer D. G.
Published: May 2005

Blends of zinc neutralized sulfonated ethylene‐propylene‐diene elastomer (ZnS‐EPDM) with poly(styrene‐co‐vinyl pyridine) have been compared with mixtures of the unfunctionalized rubber with the same copolymer. These binary component blends contain relatively low levels of interacting groups, which are, however, sufficient for the formation of intermolecular complexes. As a result of these interactions, marked enhancement in properties have been observed. In this study, small angle neutron scattering (SANS) is used to determine domain dimensions. The SANS experiments clearly show a decrease in domain size by three orders of magnitude when compatibilization via the sulfonate groups takes place. This reduction correlates with large changes in mechanical properties.
The effect of reactive monomers and functional polymers on the mechanical properties of an unsaturated polyester resin
Authors: Rodriguez Ernesto L.
Published: May 2005

A general‐purpose unsaturated polyester resin with 2:1 mol ratio of styrene to polyester unsaturation was modified with three vinyl monomers and two hydroxyl terminated polybutadienes. Tensile, flexural, and puncture impact properties were examined. The three acrylate monomers were tetraethylene glycol dimethylacrylate, 1,3 butylene glycol dimethacrylate, and trimethylpropane trimethylacrylate with weight percents of 2.5, 5, 15, and 30. Two hydroxyl terminated polybutadienes with slightly different contents of hydroxyl functionality were also employed in the weight percents of 2.5, 5.0, and 10.0. Results showed that an increase in the number of crosslinks and crosslink density resulted in a deterioration in the mechanical properties. The addition of an immiscible polybutadiene polymer to the polyester resin also showed a decrease in the mechanical performance of the resulting thermoset materials.
Computational study of chaotic mixing in co‐rotating two‐tipped kneading paddles: Two‐dimensional approach
Authors: Lawal Adeniyi , Kalyon Dilhan M. , Ji Zhenghua
Published: May 2005

This study attempts to investigate the kinematics of the mixing occurring in the lenticular kneading disc section of the co‐rotating twin screw extruder, employing the tools of dynamics. The Eulerian velocity field distributions, generated by a two‐dimensional isothermal and creeping flow of Newtonian fluid under the periodic co‐rotation of the kneading discs, were obtained by Finite Element Method. A simple and novel particle tracking technique based on the FEM solution of the velocity field was employed to follow individual particles, and to produce the Poincare section mapping. Furthermore, fingerprints of chaotic motion were revealed essentially through the Lyapunov exponents, which were positive. The results suggest that the dynamics in the two‐dimensional kneading disc section of the twin screw extruder can be characterized as capable of imparting chaotic motion. The tools developed in this study should facilitate a better understanding of the mixing capabilities of the twin screw extrusion process.
Processing of thermotropic liquid crystalline polymers and their blends—analysis of melt‐spinning TLCP fibers
Authors: Lee Wan‐Chung , Dibenedetto Anthony T. , Gromek Jack M. , Nobile M. R. , Acierno D.
Published: May 2005

Isothermal melt‐spinning of two thermotropic liquid crystalline polymers (TLCPs), a wholly aromatic copolyester KU‐9211 (also named K161 from Bayer AG) and an aliphatic containing TLCP, PET/PHB60 (Tennessee Eastman), was studied to analyze the effect of processing conditions on fiber properties. Fibers were melt‐spun from a capillary rheometer equipped with an isothermal chamber in which cross‐flowed air was used as the cooling medium. The processing variables studied included the extrusion temperature, the extrusion rate, the cooling conditions, and the draw ratio. As‐spun fibers were characterized by measuring storage moduli and molecular orientation parameters as a function of draw ratio under various processing conditions. Among the processing variables studied, the draw ratio was the primary factor in determining both the fiber modulus and the molecular orientation. The extrusion rate did not appear to affect the fiber properties within the range studied. The properties of K161 fibers were also dependent on the extrusion and cooling temperatures, while PET/PHB60 fibers were rather insensitive to the processing temperatures within data scatter and temperatures studied. A composite model based on a rigid‐rod rotation mechanism and the deformation of nematic domains in an elongational flow field was used to model the experimental results and was compared with other theories available. Conformance of data to the composite model was obtained by use of a single temperature dependent parameter n, suggesting that the rigid‐rod rotation mechanism could be used to predict the orientation development of TLCPs. The Halpin‐Tsai equations and the orthotropic equation for angular dependence were used to describe the elastic properties of the TLCP fibers.
Reactive processing of polymer blends: Analysis of the change in morphological and interfacial parameters with processing
Authors: Okamoto Masami , Inoue Takashi
Published: May 2005

The change in morphology and interface quantities have been analyzed for an immiscible polymer blend during reactive processing. A model polymer/polymer combination, hydroxy‐terminated poly(ε‐caprolactone)/liquid rubber with α, ω‐carboxy groups, was employed. The blend was subjected to light scattering measurements, ellipsometry, and gel permeation chromatography (GPC). Size reduction of the dispersed phase during processing was followed by a systematic decrease in the correlation distance ζ and an increase in the specific interfacial area Ssp, both by the Debye‐Bueche plot of light scattering profiles. Also observed was the time variation of the volume fraction of interface Vλ estimated as a product of the Ssp and the interfacial thickness by ellipsometry. The changes in ζ, Ssp, and Vλ with processing were accelerated when a coupling agent,γ‐aminopropyltriethoxysilane (APS), was added. The amount of block copolymer formed in‐situ in the APS‐loaded system was estimated by GPC with RI and UV detectors. For the size reduction kinetics in both APS‐loaded and ‐unloaded systems, Rittinger's law was found to be applicable.
Development of high performance, waterborne coatings. Part II: Factors affecting adhesion performance
Authors: Kojima Shunji , Moriga Toshinori
Published: May 2005

A new manufacturing process for high performance, waterborne coatings for can coating application was developed, which includes emulsification of an epoxy resin with or without a hardener by incorporation of an acrylic resin. It is possible by this new process to emulsify a variety of resins with minimum effects of the surfactant. (acrylic resin). The effects of surfactant and neutralizer on adhesion performance were studied. It was found that the effects of the acrylic resin amount were relatively small, and that the effects of the neutralizer were significant. It was confirmed that the usage of ammonia or amines with a branched alkyl group is required to achieve balanced dry and wet adhesion.
Development of high performance, waterborne coatings. Part III: Characterization of coatings and cured film
Authors: Kojima Shunji , Moriga Toshinori
Published: May 2005

High performance waterborne coatings were developed which could be utilized as an adhesive primer for sideseam bonded cans. The manufacturing process is unique; blending an epoxy / phenolic solution and an acrylic resin solution and dispersing the mixture in an aqueous medium by the phase transition method. The epoxy resins are neither chemically modified by grafting nor esterified by acrylic resin, which is thought to develop the excellent performance of epoxy / phenolic coatings. The morphology of the coatings and cured film was characterized and found to be quite different from the conventional waterborne coatings, i.e., the acrylic‐modified epoxy resin systems. It was confirmed that acrylics and epoxy / phenolic resins exist in separate phases in the cured film, and that the epoxy / phenolic resin constitutes the continuous phase.
Instrumented charpy impact test of epoxy resin filled with irregular‐shaped silica particles
Authors: Nakamura Yoshinobu , Yamaguchi Miho , Okubo Masayoshi
Published: May 2005

The effect of particle size on the impact properties of an epoxy resin has been studied. This resin was filled with irregular‐shaped silica particles prepared by crushing fused natural raw quartz. These particles were sorted into six groups of different mean sizes ranging from 2 to 47 μm. The impact properties were measured by an instrumented Charpy type impact tested, which can record a load‐displacement curve during impact fracture. The impact absorbed energy (U) was measured using specimens having a U‐shaped blunt notch, and the impact fracture toughness (KCI) was measured using specimens having a sharp crack introduced by a fresh razor blade. As the particle size decreased. U increased and KCI decreased. The fractured surfaces and crack tip regions were observed using a scanning electron microscope to clarify the above phenomena.
The effect of processing on rheological and molecular characteristics of a low density polyethylene
Authors: Baker W. E. , Rudin A. , Schreiber H. P. , El‐Kindi M.
Published: May 2005

The viscoelastic responses of some molten polymers, and particularly of low density polyethylene (LDPE), are known to vary with processing history. Reasons for the variations include the effects of shear history on morphological states of the polymer, or on its molecular weight parameters. A typical low density polyethylene has been used to test the shear‐history dependence concept following a variety of processing steps. The polymer was sheared in single‐screw and twin‐screw extruders, and in a high speed melter / mixer (Gelimat). Samples also were precipitated from very dilute solutions in trichlorobenzene and in p‐xylene. GPC analyses showed that, in general, these procedures did not affect the various moments of molecular weight. An exception was the Gelimat‐mixed sample, for which mild reductions in Mn and Mw were noted. In contrast, melt viscosity and elasticity readings, the former from low shear evaluations and the latter from extrudate swelling, were affected by the various procedures. A drop in melt viscosity and in elasticity was observed, being most pronounced for precipitated and twin‐screw extruded versions of the LDPE. Reductions also were observed in the specimen sheared in the Gelimat instrument. Following conditioning at the test extrusion temperature (170°C), viscous and elastic responses tended to revert to those of the unsheared control sample, the exception again being the sample sheared in the Gelimat melter / mixer. Of the various mechanisms proposed in the literature to account for transient property changes such as those reported, temporary changes in the degree of chain entanglement appear the most satisfactory explanation. Irreversible alterations in viscoelastic properties may be associated with changes in molecular weights due to processing at high shear.
Combined reactive extrusion–orientation of polyethylene
Authors: Suwanda D. , Balke S. T.
Published: May 2005

The objective of this work is to combine reaction, extrusion, and orientation together in a process so as to provide product in a form which is not limited to fiber or film. Three coupled problems form the focus of the work: (i) devising a practical, continuous extrusion‐orientation method; (ii) generating low concentrations of free radicals in the polymer to tailor molecular weight distribution before orientation; (iii) generating high concentrations of free radicals in the polymer to form a network in the oriented polymer without destroying its superior properties after orientation. A continuous extrusion method for orienting polymer in forms other than fibers and films was devised based upon two melt pullers. Operation of a prototype of the equipment showed it capable of providing draw ratios of greater than ten. Injection of low initiator concentrations during extrusion (i.e., before orientation) directed at solving the second problem had an effect which depended upon the degree of branching, the molecular weight, and the degree of unsaturation of the polyethylene. Large increases in molecular weight could be obtained. However, in agreement with previous work, formation of branched molecules drastically limited draw ratios attainable by the extrusion‐orientation process. To obtain high concentrations of free radicals, bench scale experiments demonstrated that a recently published method involving the use of a UV sensitizer and crosslinker followed by irradiation was directly adaptable to this process (with the irradiation applied after orientation) and provided significant improvements in creep resistance. Various attempts involving die design to obtain orientation and high initiator concentrations as well as gamma radiation to induce crosslinking after orientation were attempted and appear far less promising than the above methods.
Influence of processing conditions on shrinkage behavior of low profile unsaturated polyester resins. I: Systems without fillers
Authors: Ruffier M. , Merle G. , Pascault J. P.
Published: May 2005

Blends of unsaturated polyester resin and polyvinylacetate (PVAc) were molded with a new instrument called the Plastoreactomat (PRM). The shrinkage and exothermic peak of polymerization were recorded during moding, and the influence of the processing conditions (pressure and temperature) on these phenomena and on the morphology was investigated for various PVAc contents. Within the limits of this study, it was found that shrinkage increases as the temperature and pressure increase. These results are discussed in terms of a competition between the phase separation and the reaction rates. In addition, it was verified that a co‐continuous two‐phase system consisting of the PVAc and the polyester network enhances the low‐profile behavior.
Modeling viscoelastic behavior of glasses during physical aging
Authors: Espinoza Abel , Aklonis J. J.
Published: May 2005

The generalization of a multiordering parameter model to treat physical aging in polymeric glasses is more fully explored. In the past, this model has successfully rationalized most aspects of time dependent volume and enthalpy behavior; however, only qualitative agreement between predictions of the generalized model and experiment were previously achieved for physical aging. Now, by paying strict attention to the specific analytical form of the shift factor expression, quantitative predictions have been realized for physical aging behavior based on evaluations of the shift factor parameters using volumetric data. The model also reproduces the observed behavior of glasses subjected to more complex thermal treatment such as those which evoke “memory” in glasses, e.g., shift reversal and nonmonotonic variations of the steepness of relaxation curves in the primary transition region.
The cook‐gordon mechanism in polymeric materials
Authors: Raab Miroslav , Schulz Eckhard , Sova Miloš
Published: May 2005

This review article, supported by some original experimental results, explains the nature of the Cook‐Gordon (C‐G) mechanism of crack blunting. Examples are given of how the C‐G mechanism influences the toughness of several anisotropic materials: fibrillated polymeric films, composites based on oriented polymers, and beech and spruce woods. Moreover, the C‐G mechanism can explain the effects of orientation on anisotropic photo‐oxidative degradation of semicrystalline polymers, and also the sudden embrittlement of polymeric films exposed to UV light under stress.
Distortion of nylon 6,6 moldings caused by asymmetric water absorption
Authors: Paterson M. W. A. , White J. R.
Published: May 2005

Distortion of nylon 6,6 molded bars caused by one‐sided absorption of water has been investigated experimentally and the results have been compared with the predictions of an analysis based on data measured on dry bars or bars that were immersed completely in water. Account is taken of swelling, secondary crystallization, variations in Young's modulus, and the original residual stress distribution prior to the absorption of water. The major influences on distortion are (i) swelling and (ii) secondary crystallization. A much smaller effect is caused by the change in the residual stress distribution resulting from the change in the distribution of Young's modulus that develops when water is absorbed. The two major effects normally act in opposite directions, and may sometimes balance out. Differences in distortion obtained when moldings that had different aging histories were exposed to water absorption from one surface only are discussed.
Solid state extrusion of vinylidene fluoride (VF2)/vinylidene trifluoride (VF3) copolymers. I: Dynamics of solid state extrusion
Authors: Lee J. S. , Cakmak M.
Published: May 2005

Solid state extrusion dynamics of poly(vinylidene fluoride) and its copolymers have been studied using an Instron capillary rheometer with specially designed die set. At and above the Curie transition temperatures, the copolymers rapidly soften while preserving the semicrystalline structure. This allows them to be solid state extruded between this temperature and melting temperature. The processing windows within which high quality extrudates can be obtained were established for two copolymer compositions and they were found to be much wider than those typically observed in semicrystalline homopolymers such as polyethylene and polypropylene. Extrudate swell under all solid state extrusion condition remains constant and is always less than 1 and it was found to increase above this value as the extrusion temperature increased through the melting region which is typical of melt extrusion of these polymers.