The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Rajeev L. Gorowara, Roy L. McCullough, Steven H. McKnight, May 2000
Model multi-component glass fiber sizings, with formulations based upon current patent disclosures, were prepared to model the full coating packages used in commercial glass fiber manufacture. The sizings consisted of silane coupling agent, film former, and emulsifying surfactant in water, and were applied to glass fibers prepared directly from molten glass. Sizing formulations were extended to vary component reactivity and molecular weight. Unidirectional multi-fiber composites were prepared with Dow Derakane 411-C-50, a vinyl ester / styrene resin system. Interphase durability was characterized by measuring interlaminar shear strength (ILSS), before and after hygrothermal exposure.
A novel ionomer is being developed to modify nylon for blow-molding applications. The new ionomer that contains reactive functional groups attains excellent compatibility with nylon by a combination of physical and chemical interaction. The modifier can be dispersed in small particle size as low as 50 nm in nylon 6. This report discusses the melt rheology, blow-molding evaluation and weldline strength of the nylon modified with the novel ionomer. The particle size of the ionomer dispersed in nylon is discussed to explain the unique properties of the new modifier. For comparison, a maleated ethylene polymer (EP) and a conventional ionomer are included in the study.
Polystyrene was blended with small quantities of PP, HDPE, and LDPE and foamed using carbon dioxide as a blowing agent in a twin screw extruder to obtain low density foams. The effectiveness of these additives on the bubble nucleation, density and mechanical properties of the foams was studied. The results show that addition of PP in small quantity improves density, cell size, and surface properties of the foam drastically. The improvement is attributed to crystallization of PP before foam cell expansion; this results in bubble nucleation from the formed crystal sites that also act as gas barrier for individual cells.
Ultrasonic techniques are recognised as powerful sources of process information. Transducers are applied directly, are non-invasive, yet interrogate the entire melt cross-section, while data are available real-time. During injection moulding, two zones are considered: nozzle and cavity. In the nozzle, ultrasonic velocity measurement provides temperature and pressure information. Mean temperatures not observed by other techniques are detected. Previous extrusion based experience is used to address issues of high temperature transducer operation. In the cavity, changes in reflection coefficient and ultrasonic velocity provide information on mould filling and part cooling. Various mould geometries are monitored using a number of ultrasonic transducers.
DSC analysis is conducted to obtain kinetic information of the chain addition copolymerization in bulk of a quad-monomer acrylic system. The experimental variables include reaction temperature, type of peroxide and peroxide concentration. By assuming that the copolymerization is a simple reaction, the approximate apparent order of the reaction can be identified; and along with the heat of reaction information, it is demonstrated that the DSC analysis is very useful in facilitating the parametric design process of a continuous stirred tank reactor (CSTR) operation. Selected results of conversion and cumulative copolymer composition of the CSTR samples are included. A more rigorous approach of analyzing the reaction kinetics of the copolymerization is also briefly addressed.
The quality of the mixing of different raw materials, i.e. the uniformity of the mixture, is a key issue that will determine the morphology and the specific product properties of the resulting compound [1, 2]. Numerical simulation of flow in extruder components provides a new insight, both qualitative and quantitative, into those features. 3-D transient numerical simulations of twin screw extruder (TSE) configurations are presented. A special method, the mesh superposition technique (MST), has been introduced to provide a convenient way to model intermeshing TSEs without involving any remeshing complexity . It has been validated in previous work for isothermal cases . To account for the important non-isothermal effects, the method is compared against numerical and experimental results for additional, non-isothermal validation . We present an analysis of different non-isothermal features that characterize the flow induced by a co-rotating as well as a contra-rotating configuration. Both cases are compared in terms of pressure profiles, temperature fields, resulting torque imposed on the screws and from a mixing point of view to illustrate a typical analysis of different TSEs and provide objective information to select the most appropriate configuration for specific process requirements.
D.W. Yu, S.K. Dey, F. Pringgosusanto, M. Xanthos, May 2000
Melt strength of polymers is one of the primary criteria for the success of low-density extrusion foaming and thermoforming processes. In this paper, branching of PP using polyfunctional monomer was studied in a batch mixer and a small scale co-rotating twin screw extruder as a function of modifier concentration and process conditions. Melt viscoelastic properties of the products, related to melt strength/elasticity, including die swell and recoil, were investigated to examine the degree of long chain branching, which could lead to improve foaming and thermoforming processability. The melt strength of those materials was compared with that of a commercial high melt strength PP and an unmodified general purpose PP.
Zhiyong Xia, Hung-Jue Sue, Thomas Rieker, May 2000
Semi-crystalline poly(ethylene terephthalate) (PET) was shear orientated by the novel Equal Channel Angular Extrusion (ECAE) process. Small angle X-ray scattering indicates that extrusion induces preferred orientation of the lamellar structure. Before passing the shear plane, the material has a weak orientation. But after passing the shear plane two preferred orientations are formed in the extruded region; one perpendicular to the shear plane; the other 45° from the shear plane. The physical and mechanical properties of the extruded PET were also investigated and found to correlate well with the ECAE-induced shear orientation.
The correlation between structure development during injection molding, and the tensile modulus of injection molded PET/LCP blends were studied, through experimentation and numerical simulation. Process parameters were varied to determine their effects on the tensile modulus and structure development of the blends. A combined numerical simulation and analytical calculations, has been used to model the experimental results. A model that establishes the relationship between the aspect ratio of LCP fiber, the elongational strain, and the tensile modulus, enables us to predict the processing dependent morphology and tensile modulus of injection molded blends.
Rich Farrell, Steve Goodwin, Carl Wirsen, Jeanne Lucciarini, Mathew Martinez, Jo Ann Ratto, May 2000
Nanocomposites containing biodegradable polymers and clays were investigated to improve biodegradable properties. Polycaprolactone (PCL) (83,000 and 43,000 g/mol molecular weight) was mixed with additions of either 2 or 5% of synthetically modified montmorillonite clay. A twin screw extruder was used to produce the pellets. The pellets were then co-extruded with multilayering technology to produce 15-inch wide films from a 256 and 1024 layer die multiplier configuration. This study focuses on the biodegradation studies in compost, soil, and marine environment with results showing improved biodegradation rates in selective nanocomposites and environments.
Flow-induced migration of polyethylene-co-maleic anhydride (PE-co-MA) additives in a polyethylene (PE) melt is investigated using long-chain branched polyethylene covering a range of melt index. Attenuated total reflection infrared (ATR FTIR) spectroscopy and interfacial tension measurements were used to characterize surface composition of copolymer additives processed by a melt extrusion. Experiments covering a range of shear rates, die length/diameter and extrusion temperatures are described. The surface concentration of copolymer additives were changed from the bulk to the surface of extrude depending on the shear rate and temperature due to the shear-induced diffusion of macromolecules. A mechanism based on stress-induced diffusion is proposed to explain the observed surface migration phenomena.
By the year 2010, HCFC 142b will be banned for use as a foaming agent for extruded polystyrene (PS) foam in North America. Many blends of foaming agents have been patented as replacements to expand PS. In this study the optimal concentration of a previously unexplored blend of CO2 and 2-ethyl hexanol (2-EH) is shown to allow the production of PS foam of 30 kg/m3 density. The glass transition temperature reduction of the PS, due to the incorporation of 2-EH, is believed to be an important contributor to the success of this foaming agent blend. In long-term use of the foams, the 2-EH does not measurably diffuse out of the PS whereas the half-life of CO2 diffusion out of the foam is measured in weeks.
Louis E. Daigneault, Fadéla Ouraghi, Nicole Côté, May 2000
Medium and high density polystyrene foam moldings were produced by compression and injection molding. Polystyrene (PS) was first impregnated with HCFC 141b and pelletized. These impregnated pellets became the feedstock in injection and compression molding, with cycles typically lasting between 1 and 30 minutes in duration. The compression molding cycles were studied to optimize the mold release method and the cycle times ascribed to heating, pressure release and sample cooling. The lowest foam density reached was 196 kg/m3. While residual foaming agent in the matrix negatively impacts on the mechanical properties of the foam, the results of this work demonstrate that a physical foaming agent is feasible for compression molding and short-shot injection molding of PS. It should however be pointed out that HCFC 141b will be banned for use in the U.S. by the year 2003 and in Canada by 2010.
The fracture toughness, defined as Kc, of injection molded long fiber reinforced polypropylene with 50% E-glass and its variations is investigated. Rectangular plaques of different thicknesses at various sets of processing conditions have been fabricated. In order to assess the spatial variation of the fracture toughness, specimens aligned in the direction of the injection molding flow and perpendicular to it, have been obtained and tested at pre-selected locations. The morphology of the samples consisting of flow induced through-thickness layers was also evaluated experimentally and related to the fracture toughness, thus showing the effect of the part morphology on such mechanical property.
Liyong Yu, Yi-JeJuang, Kurt W. Koelling, L. James Lee, May 2000
Thin-wall injection molding is a key technology allowing the low-cost mass production of microstuctures, such as devices with surface-relief microcomponents widely applied in micro-optics, micro-fluidics, medical and biotechnology. Research was performed in order to gain better understanding of important parameters in injection molding of thin-wall microstructures. A series of injection molding experiments were conducted with PC and PMMA, which are common materials in bio-MEMS (Micro Electro Mechanical System) applications. The rheological properties were characterized through dynamic, and transient shear viscosity measurement using a Rheometrics Mechanical Spectrometer. Micro-channels of different lateral and depth dimensions were obtained on thin wall substrates. The Scanning Electronic Microscope (SEM) photos were used to measure the fidelity and roughness of the replicated plastics. Birefringence was used to qualitatively examine the amount of residual stresses in the molded parts.
Fundamental scratch damage behavior in polymers was studied through investigation of a series of polycarbonate and polystyrene samples with different molecular weights. The constant load scratch test, based on a spherical indenter, was employed. Scanning electron microscopy and transmitted optical microscopy were performed to examine surface and subsurface damage during scratch. The plastic flow scratch pattern and the fracture scratch pattern are the two typical scratch patterns found in polymers. It is shown that shear yielding is the main mechanism for the plastic flow scratch pattern, while tensile-tear induced fracture on the surface and shear-induced fracture on the subsurface are the main damage mechanisms found in the fracture scratch pattern. The relationship between scratch resistance and material property relationship in polymers is discussed.
Everyone - color concentrate manufacturer, resin producer, compounder, molder, or extruder - understands delivering the right color the first time is crucial to customer satisfaction. Today, digital color communication technology ensures color specifications across approval points and within an increasingly complex cycle of tighter manufacturing tolerances and requirements, global competition, and just-in-time scheduling. By replacing physical sampling with digital, adjustments and approvals are made on screen, eliminating time, cost, and frustration among all points in the supply chain. This paper explores the profound implications this new technology has on the entire color cycle- from design to compounder to finished product.
Pierre Moulinié, Louis E. Daigneault, Caroline Woelfle, Richard Gendron, May 2000
Low density poly(ethylene-co-octene) foams were produced by injection molding compounded formulations consisting of resin, chemical foaming agent, activators, cross-linking agent and nucleating agent. The effect of the formulation on the foam density and morphology was examined for one set of processing conditions. The concentration of cross-linking agent must be geared to the initial resin viscosity to allow proper bubble growth. The foam will otherwise collapse or show little expansion. The results show that an optimized formulation along with proper processing conditions yield fine-cell foam of low density.
O.S. Rodríguez-Fernandez, P. Sifuentes, L.F. Ramos de Valle, J. Matutes-Aquino, O. Ayala-Valenzuela, D. Rios-Jara, May 2000
In this paper the mechanical, magnetical and rheological properties are analyzed. The influence of different magnetic powders onto a plasticized polvinyl chloride) were studied. The magnetic characterization of isotropic plastic bonded magnets, based on strontium ferrite (SrFe12O19) and plasticized polyvinyl chloride, as a function of composition was analyzed in a magnetometer at room temperature. In order to explain the dependence of the volumetric density and the saturation magnetization with composition, an additive model for these properties is considered. The intrinsic coercivity shows a decrease with increasing strontium ferrite content, which is due to the increasing interaction between the magnetic particles. The maximum energy product is lower than 1 MGOe and increases with the second power of the strontium ferrite content. The rheological properties were studied in a capillary rheometer; it was found that viscosity increased as the magnetic powder concentration increased in the composite.
Rigoberto Ibarra-Gómez, Oliverio S. Rodríguez-Fernández, Luis Francisco Ramos-Devalle, May 2000
Important appliances have arised from the study of polymer composites containing conductive particles (e.g., EMI shielding, antistatics, wire coatings for overcurrent prevention). The present work is concerned with dynamic properties related to the microstructural arrangements, as observed by Transmission Electron Microscopy (TEM), in an elastomeric blend system consisting of Polybutadiene (BR), EPDM and Carbon Black (CB). Based on changes in the viscous component signals of BR and from micrographs of samples stained with osmium tetroxide it was found that the CB was located mainly in the BR phase. Final behavior of the conductivity was found to have great dependece on this fact.
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