bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrostatically extruded glass‐fiber‐reinforced polyoxymethylene. I: The development of fiber and matrix orientation
Authors: Hine P. J. , Davidson N. , Duckett R. A. , Clarke A. R. , Ward I. M. 
Published: April 2004

AbstractThis paper describes the determination of fiber and matrix orientation in oriented short‐glass‐fiber‐reinforced polyoxymethylene (POM) composites produced by hydrostatic extrusion. The starting material was random glass fibers (25 wt% and average length 150 μm) in an isotropic POM matrix, and the oriented composites were produced by extrusion through a reducing conical die at 15°C below the polymer melting point: after extrusion the average fiber length was reduced slightly to 133 μm. Fiber orientations were measured using an image analysis method developed at Leeds University, and the matrix orientation was determined using wide angle X‐ray diffraction. The development of fiber orientation with extrusion ratio was found to be close to that predicted by the pseudo‐affine deformation scheme although the fiber orientation was greater than that predicted by the model at low draw ratios and slightly less at the highest draw ratio. The development of the orientation of the crystalline portion of the matrix was found to be always significantly greater than that predicted by the pseudo‐affine scheme.
Dielectric studies of phase separation induced by chemical reaction in thermoplastic modified epoxy
Authors: Vinh‐tung C. , Boiteux G. , Seytre G. , Lachenal G. , Chabert B. 
Published: April 2004

AbstractDielectric measurements were performed in real time to follow the reaction of polymerization in thermoplastic (TP) modified epoxy‐amine (EA) blends. This epoxy system exhibits a phase separation induced by the reaction in the liquid stage of the resin. It results in 3 different types of morphology, made of a TP‐rich phase and an EA‐rich phase. In an electrically stimulated sample, the phase separation results in an interfacial polarization seen by dielectric spectroscopy. This paper shows the possibility of monitoring both the phase separation and the vitrification of each phase. The gelation of the resin is not detected by this technique. By correlating morphological observations with characteristic dielectric responses, the type of morphology can be identified from the permittivity during the phase separation.
Bubble transport through constricted capillary tubes with application to resin transfer molding
Authors: Lundström T. Staffan 
Published: April 2004

AbstractThis paper describes and expounds a theoretical and experimental study of bubble motion through constricted capillary tubes. In the experiment, two liquidfilled capillaries are used. They have unequal radii and are glued together. Gas bubbles are injected into the larger capillary. Then the pressure required to force the bubbles through the constriction is measured for various liquids, bubble lengths, capillary radii and constriction geometry. It appears that the pressure directly follows Young's‐Laplace law for capillary pressure. The results of the study are used to understand the bubble transport through fiber reinforcements, which generally takes place during the manufacturing of composites. The bubbles are carried if: (i) the pressure gradient is high enough, (ii) the surface tension of the liquid is low enough, (iii) the cross‐sectional area of the channels in the reinforcement is sufficiently uniform. The theory reveals that the bubbles are more likely to be trapped on a small scale, i.e. within fiber bundles rather than on a large scale, i.e. between the bundles. It is also concluded that, if the bubbles are trapped at the resin flow front, a converging flow is better for the transport of the voids than a diverging flow.
Snagging resistance of sparsely reinforced flexible elastomer sheets
Authors: Pan Rong , Watt Daniel F. 
Published: April 2004

AbstractOne objective of the work discussed in this paper is to develop a material with high snag resistance, where snagging is the glancing penetration of a composite sheet by sharp objects. The best material of those tested to date is a soft polyure‐thane sheet reinforced sparsely with a web of extruded polyurethane fiber. Stiff carbon fibers sparsely distributed also give good snagging resistance, but closely spaced stiff fibers do not perform well in the ASTM Standard test for snag resistance.
Highly filled thermoplastic composites. II: Effects of particle size distribution on some properties
Authors: Kauly T. , Keren B. , Siegmann A. , Narkis M. 
Published: April 2004

AbstractThe effect of irregularly shaped glass particle size and size distribution on the packing density and flexural mechanical properties of highly‐filled composites with a rubbery thermoplastic matrix was studied. Increasing the particle's median size and size distribution width significantly increases the packing density of the composites. Compression molding causes the glass particles to fracture at a decreasing level with an increasing distribution width. Particle median size, rather than size distribution, affects the mechanical properties; The flexural modulus and strength increase and the ultimate deflection in flexure decreases with a decreasing median size. A “glass network” is formed in the compression molded composites because of the mechanical interlocking of particles. The nature of this continuous glass phase predominates the composites mechanical behavior. The particle's size and shape determine the nature of the glass network and, thus, have a dominating effect on the mechanical properties. The latter are significantly affected by the particle's surface properties. A specific silane treatment of the glass particles acts to reduce the particle/particle friction, resulting in a higher packing density. The treatment also acts as a cohesive liquid to increase the strength of the glass network, and to increase the particle/polymer adhesion, increasing the composites' strength and ductility.
Reprocessing of fiberglass reinforced polyamide 66: Influence on short term properties
Authors: Eriksson P.‐A. , Albertsson A.‐C. , Boydell P. , Eriksson K. , Månson J.‐A. E. 
Published: April 2004

AbstractThe fiber length distribution was found to control the overall short term performance of reprocessed heat‐stabilized short fiberglass reinforced polyamide 66. Length changes, and matrix and interface degradation were studied. Fiber shortening dominates during compounding and during the first injection molding cycle. Further regrinding and remolding has a lesser effect. The short term mechanical strength decreased for reprocessed samples. Using a modified Kelly‐Tyson model, the lower tensile strength of reprocessed samples, compared with virgin samples, can be explained by fiber shortening. Reprocessing had a negligible effect on the strength for both the fiber matrix interface and the matrix of this system. Studies on unreinforced samples confirmed that thermal degradation of the matrix during reprocessing had a negligible effect on short term mechanical performance.
Prediction of mechanical properties of recycled fiberglass reinforced polyamide 66
Authors: Eriksson P.‐A. , Albertsson A.‐C. , Boydell P. , Prautzsch G. , Månson J.‐A. E. 
Published: April 2004

AbstractAn experimental study of the mechanical performance of in‐plant recycled fiberglass reinforced polyamide 66 is reported. The fiber length distributions were used to investigate and to predict the influence of process induced fiber shortening on the short term performance of recycled samples compared to that of virgin samples. The results indicate that fiber shortening has a strong influence on strength. Applying a modified Kelly‐Tyson model to the fiber length distribution gave excellent agreement with measured strength. There was no need to vary interface or matrix properties in the theoretical analysis. The effect of reprocessing on these factors does not appear to influence strength within the bounds of the model. The decrease in strength during a continuous in‐plant recycling process is small at a 30 wt% regrind level. Indeed, below 50 wt% regrind, the strength remains within design limits. The impact strength of dry unnotched samples indicated that the resistance is related to the reciprocal fiber length.
Extrudate swell behavior of glass fiber filled polyamide 6
Authors: Wagner Alan , Yazici Rahmi , Kalyon Dilhan M. 
Published: April 2004

AbstractThis paper discusses the extrudate swell behavior of glass‐filled polyamide 6. The key features of the experiments were the facility to extrude directly into a density matched oil kept at extrusion temperature and thus, the ability to measure the diameter of the extrudate of the glass‐filled polyamide immediately upon exit from the die, without the extrudate contacting air and as a function of time in a chamber under isothermal and neutrally‐buoyant conditions. The concentration and orientation of the fibers of the extrudates were also studied using X‐ray radiography in a post‐mortem fashion. A skin/core morphology, where uniaxially aligned fibers constitute the skin zone and the core contains a reduced concentration of fibers, was observed.
Needle‐Punched hybrid nonwovens of flax and ppfibers—textile semiproducts for manufacturing of fiber composites
Authors: Mieck K.‐P. , Lützkendorf R. , Reussmann T. 
Published: April 2004

AbstractFlax‐nonwoven reinforced polypropylene has become a competitor to textile glass fabric reinforced polypropylene because of its economic and ecological advantages. Suitable application forms are needle‐punched 100% flax or hybrid fabrics of flax/polypropylene manufactured of rough and fine decorticated flax. The construction of the nonwoven influences the strength, handle, matrix compatibility, and flow of the fabric. In this way, composite properties may be tailored to each end‐use. The main application fields are subassemblies exposed to a medium range of stress. The method of hybrid‐nonwoven manufacturing represents a technological alternative to the existing film‐stacking method. Produced with lower technology, the parameters of composites of hybrid‐nonwovens are comparable to properties of composites manufactured by the film‐stacking method. Adhesion characteristics may be improved by addition of compatibilizers. The compatibilizers may be added to the flax‐fiber surface or may be inserted into the polypropylene. All these methods lead to comparable mechanical parameters for the fiber composites.
Process‐induced effects in thin‐film bonding of PEKEKK in metal‐polymer joints
Authors: Ramani Karthik , Tagle John 
Published: April 2004

AbstractIn this work, poly ether ketone ether ketone ketone (PEKEKK) was used as a thermoplastic adhesive for joining metals. Titanium and cobalt chromium alloys were joined to form tensile butt joints. These tensile specimens were used to evaluate bond performance. A controlled thermal processing cycle was used to modify and enhance the polymer crystallinity during bonding. The resulting effects on bond performance were examined. The process window for a thermal bonding process was identified. Factorial experiments were conducted to determine the effects of modifications to adhesive and adherend material, and bonding pressure on bond performance. A titanium alloy and a cobalt chromium alloy were used as the adherends. Understanding changes in the thermoplastic adhesive joint with the variation of process parameters will allow for proper application and processing of thermoplastic structural adhesives.
Influence of fiber surface treatment on the properties of sisal‐polyester composites
Authors: Singh B. , Gupta M. , Verma Anchal 
Published: April 2004

AbstractThe effect of several chemical treatments, viz. organotitanate, zirconate, silane, and N‐substituted methacrylamide, on the properties of sisal fibers used as reinforcement in unsaturated polyester resin (∼50 vol%) was investigated. An improvement in the properties was observed when sisal fibers were modified with surface treatments. Under humid conditions, a decrease of 30 to 44% in tensile and 50 to 70% in flexural strength has been noted. The strength retention of surface‐treated composites (except silane) is high compared with untreated composites. It is observed that N‐substituted methacrylamide‐treated sisal composites exhibited better properties under dry as well as wet conditions. Fractographic evidence such as fiber breakage/splitting and matrix adherence on the pulled‐out fiber surface explains such behavior.
Fatigue behavior of neat and long glass fiber (LGF) reinforced blends of nylon 66 and isotactic PP
Authors: Harmia T. 
Published: April 2004

AbstractThis paper focuses on the study of the fatigue behavior of neat and long glass fiber (LGF) reinforced nylon 66/PP‐blends. The fatigue was characterized using Parislaw plots in the stable crack growth acceleration range. The fatigue crack propagation (FCP) is presented as a function of the crack growth per cycle (da/dN), the amplitude of the stress intensity factor ΔK, and of the strain energy release rate ΔG. It was also of interest to compare the order of performance found in fatigue to that in the static fracture test. The fracture surfaces were characterized with SEM to determine the failure mechanisms. Further, thermographic camera recordings were used to study the size of a “heated” area (ΔT = 2°C) that developed around the crack tip during the cyclic loading of LGF‐PP with different amounts of maleic anhydride grafted PP (PP‐g‐MAH). For the neat materials, a different order of performance was detected under static and cyclic loading. This was explained by the different failure mechanisms observed after static and cyclic fracture that were related to different stress states of the specimens during the fracture process. On the other hand, the LGF‐blends showed a similar order of performance during the static and the fatigue test. This was explained by the observation that similar fiber related failure mechanisms occurred in the composite, both after failure caused by the static and cyclic loading, respectively. For the LGF‐PPs with varying PP‐g‐MAH content, the order of performance in fatigue did not correspond to the size of the “heated area” around the crack tip. This was caused by a change in the composite failure mechanisms, which contributed differently to the size of the “heated area” and to the fatigue performance.
Fracture failure processes in polymers. II: Fractographic evidence
Authors: Liu K. , Piggott M. R. 
Published: April 2004

AbstractTensile fracture and punch shear failure surfaces have been observed in a scanning electron microscope. In most cases tensile cracks were visible in the shear fracture surfaces and crack initiation points could be found in the tensile fracture surfaces. The punch test imposes very large shear strains on the materials (many thousand percent) and this appears to reorient the chains so that, so long as the chain length is great enough (>4000 repeat units for polyethylene), chain scission is observed, and the failure process at the molecular level is tensile rather than shear. The exceptions are the shorter chain polyethylenes and polypropylene, which are probably truly liquid‐like, with little or no chain scission being involved in tension or shear.
Effect of humidity on the time to breakdown of polymers subject to partial discharges
Authors: Guastavino F. , Tiemblo P. 
Published: April 2004

AbstractThree polymers, polyethylene terephthalate, a polyimide, and polyamide‐6, were subjected to surface partial discharges up to electrical breakdown under varying ambient humidity conditions. It was found that increasing humidity increases lifetime of the samples until a critical value of relative humidity is attained, after which the polymers' lifetime dramatically decreases. This critical value depends on the hydrophylicity of the polymer and is lower as the ability of the polymer to absorb water increases. The evolution of the electrical time to breakdown with the relative humidity is explained in terms of changes in surface conductivity following variations in the ambient humidity.
Fusion bonding of maleated polyethylene blends to polyamide 6
Authors: Sánchez‐Valdes S. , Yañez‐Flores I. , De Valle L. F. Ramos , Rodriguez‐Fernandez O. S. , Orona‐Villarreal F. , Lopez‐Quintanilla M. 
Published: April 2004

AbstractBlends of linear low‐density polyethylene (LLDPE) and linear low‐density polyethylene–grafted maleic anhydride (LLDPE‐gMA) were used to promote the adhesion to polyamide 6 (PA) in a three‐layer coextruded film without using an additional adhesive or tie layer. The effect of bonding time and molecular weight (MW) of different maleated polyethylenes on the peel strength of the joints was analyzed. Direct evidence of a copolymer formed in‐situ at the interfaces is also considered. The peel strength of fusion bonded layers of LLDPE/LLDPE‐gMA blends with PA strongly depends on bonding time and molecular weight of the maleated polymer. Tensile properties of three‐layer films, made up of PA as the central layer and LLDPE/LLDPE‐gMA blends as the two external layers, are improved with increases in the maleic anhydride (MA) content in the blend. The in‐situ formation of a copolymer between the MA in the blend and the terminal amine groups of the PA was confirmed by the Molau test, infrared (IR) spectroscopy, and thermal analysis (DSC).
Development of heat‐activated joining technology for composite‐to‐composite pipe using prepreg fabric
Authors: Stubblefield Michael A. , Yang Chihdar , Pang Su‐Seng , Lea Richard H. 
Published: April 2004

AbstractOwing to the lack of reliable and cost‐effective joining methods, composite materials have not yet achieved their full market potential. The use of heat‐activated thermal couplings offers a quick and cost‐effective method for joining composite‐to‐composite pipe. In this study, a prepreg laminate containing thermoset resins and fiberglass reinforcements is wrapped around the ends of the components to be joined. A shrink tape, constructed of an oriented polyester film, is placed over the prepreg laminate. When heat is applied to the thermal coupling for curing, the shrink tape shrinks and compresses the prepreg to improve adhesion. Tests of the heat‐activated thermal coupling in bending shows an increase of 29% over the currently used butt‐weld method. A finite element model has been developed to assist in determining the most appropriate cure cycle required for different joint configurations. This reduces the need for experimentation when a variable has been changed. Based on the tested prepreg material properties and model, the FEA temperature distribution differs less than 10% from that of experimental results.
Fiber reinforcement and fracture resistance of PC/PBT/LCP ternary in situ composite
Authors: Wong Shing‐Chung , Mai Yiu‐Wing , Leng Yang 
Published: April 2004

AbstractThe microstructures, mechanical properties, and fracture toughness of LCP (Vectra B950) reinforced PC/PBT blend with a 60/40 weight ratio have been studied. LCP of varying concentrations were investigated as rigid fillers in matrices of multiphase polymer blends. In this study, differences in microstructures and morphology between samples of two thicknesses (4 mm thick and 6 mm thick) and two geometries (dumbbell and rectangular) were compared using scanning electron microscopy (SEM). Given identical processing conditions, fibrous LCP structures were evident in the 4‐mm‐thick injection molded, dumbbell‐shaped samples, whereas the 6‐mm‐thick rectangular samples displayed spherical dispersion of LCP aggregates that embrittled the preblended ductile matrix. Tensile properties of the dumbbell specimens showed superior strengthening and stiffening whereby the tensile strength increased twofold and the modulus increased fourfold. Plane strain fracture toughness was slightly enhanced as the LCP content increased because of the fiber strengthening effect but the overall fracture performance of the in situ composites was relatively poor compared with PC/PBT. Experimental results were compared with those predicted in composite theory. Simplified micromechanics equations were developed to describe the tensile moduli of injection molded LCP reinforced blends that exhibited a strong skin‐core morphology.
Plastification or melting: A critical process for free radical grafting in screw extruders
Authors: Cartier Hervé , Hu Guo‐Hua 
Published: April 2004

AbstractThis paper shows for the first time that when a monomer is to be grafted onto a polymer backbone by a free radical mechanism in a twin screw extruder, the grafting process occurs mainly, if not exclusively, in the plastification (melting) zone. For this purpose, the free radical grafting of glycidyl methacrylate (GMA) onto polypropylene (PP) and polyethylene (PE) was chosen as model systems. A co‐rotating self‐wiping twin screw extruder of type Werner Pfleiderer ZSK‐30 (L = 42D) was used to process the grafting. Owing to its modular character in terms of barrel arrangement, screw element combination and barrel temperature, the position and length of the plastification zone can be adjusted virtually at will. This allowed us to follow up the grafting not only at the die exit, but also in the plastification zone under different grafting conditions. Our results clearly show that it is in the plastification (melting) zone that the entire grafting process occurs. This length is usually very short in a co‐rotating twin screw extruder like ours. Under the grafting conditions, it varied from 1D to 5D. Thus, any relevant analysis or model of a free radical grafting process carried out in a screw extruder must be based on detailed information generated not only at the die exit, but also and most importantly in the plastification zone. Otherwise, it may lead to incomplete and/or wrong conclusions.
Fluorescence based measurement of temperature profiles during polymer processing
Authors: Migler Kalman B. , Bur Anthony J. 
Published: April 2004

AbstractWe describe a novel noninvasive method to measure temperature profiles during processing. A key feature is the use of a temperature‐sensitive fluorescent dye that is incorporated into the polymer resin at dopant levels. By monitoring spectral features of this dye, we can effectively measure its temperature. A focusing technique that we call “confocal fluorescent optics” then allows us to measure the temperature as a function of position into the resin. We present results of critical tests of the device. Namely we test the spatial resolution and its ability to measure a linear temperature profile in a quiescent polymer. Finally, we present the first on‐line temperature profile measurements, carried out in a circular die at the exit of a twin screw extruder. Temperature gradients on the order of 5°C/mm in a polyethylene resin are observed between the outer wall and the center of the die.
DSC studies on the crystallization characteristics of poly(ethylene terephthalate) for blow molding applications
Authors: Fann Daw‐Ming , Huang Steve K. , Lee Jiunn‐Yih 
Published: April 2004

AbstractThe crystallization behavior of blow‐molded PET bottles, which helps determine the product's transparency, was investigated by DSC dynamic cooling experiments that simulated the cooling that occurs in the injection blow‐molding manufacturing process. Dynamic cooling crystallization of PET optimized the conditions for keeping crystallinity to a minimum during the production of PET bottles. The kinetic parameters of non‐isothermal crystallization behavior were determined, which indicate that the competing processes of nucleation and the growth of PET spherulites during the cooling process are the controlling factors for the degree of crystallinity in the final product. In addition, DSC measurements were employed to obtain information on related aspects, such as the ease of crystallization from glassy and molten states and the crystallinity in the products. An Avrami equation was used for the calculations of the crystallization kinetic parameters.