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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Coextruded Flow in Partially Miscible Systems
Coextrusion technology for solid rocket motors, is proposed to be improved to widen the limits on the range of property variation in functionally graded materials and reduce the associated disparities in processing characteristics. Helical coordinate system is suggested to model the coextruded flow and calculation of interlayer adhesive strength. The design aspects for the material components selected for the coextrusion system is revisited. A finite difference scheme is proposed for the numerical study. The interdiffusion term is proposed to be simulated by considering the concentration independent Diffusion term in Fick's's law of diffusion. A suitable theory for the diffusion in polymer polymer system is needed. Newton-Raphson method is applied for the iterative solution of the algebraic equations. Polymer polymer miscibility and phase behavior is a salient consideration. Marangoni effect can be used to improve interfacial mixing in coextrusion of bifunctional partially miscible and miscible polymer polymer systems. A temperature gradient imposed in addition to the density gradient by arranging the n-layers in certain order of densities leads to a interfacial tension gradient giving rise to the thermocapillary stress and cause flow at the interface. Asymptotic analysis was used at small and large Peclet numbers. This leads to the coupling of momentum and energy equations where convective transport is not negligible. Disturbance flow created by this mechanism has interesting features that are not present in the corresponding problem wherein the motion occurs due to a body force. The implications on the thermocapillary instability by the blend miscibility is discussed.
Continuous Copolymerization of ?-Methylstyrene-Acrylonitrile, ?-Methylstyrene-Acrylonitrile
Two different approaches are proposed to calculate the chain sequence distribution in ?-methyl styreneacrylonitrile copolymer and AMS-AN-S (?-Methylstyrene-acrylonitrile-styrene) terpolymer, ?-methylstyrene-acrylonitrile copolymer and BMS-AN-S (?-methylstyrene-acrylonitrile-styrene) terpolymer. Tube polymerization studies on the terpolymerization of AMS-AN-S using thermal initiation showed that molecular weight can be built at reasonable kinetic rates. One of the approaches is by using the probability model and expressing the results as geometric distribution neglecting effects due to Markov Statistics. The second approach is to use Monte Carlo simulations to calculate the chain sequence distribution.
Constitutive Relationship for Electrorheological Fluids
The Winslow effect in smart-fluids is used in the design of automatic transmission fluid. A configurational distribution function is written and mesoscopic simulations are used to derive the constitutive relation for the stress tensor. The polymer molecule is modeled as an elastic dumbbell connected by a linear spring. Microscopic phenomena and macroscopic behavior are interrelated. Preliminary results reveal that the Bingham or yield stress behavior can be predicted from the first principles. Particle-Particle interactions, Brownian motion induced effect, self-assembly, Marongoni mechanism for particle clustering and their roles in durability, dispersion stability, redispersability and fluidity are explored.
Influence of Mixing Conditions and Composition on the Phase Structure and Properties of Thermoplastic Olefin Blends
Morphology and mechanical properties of blends of polypropylene/ ethyelene-propylene-diene terpolymer (PP/EPDM) were studied in relation to mixing conditions, and blend composition. The number average diameter (Dm) of dispersed elastomer was found to depend not only on the blend composition but also on the mixing temperature and effective shear rate. The number average diameter increased with the increase in viscosity ratio, ?EPDM/?PP. Mixing temperature was found to be an over riding determinant of flow properties and morphology. All key properties including impact strength, flex modulus, weld line strength, and paint adhesion were influenced both by the composition and morphology. It is demonstrated that good dispersion in blends with mismatched viscosities can be achieved by simultaneous increase in temperature and speed.
An Innovative Approach to Computer Controlled Continuous Injection Molding
Modern polymers are continually finding increased application in many diverse products once dominated by metals. They provide an economically viable alternative to traditionally costly metals in many applications where strength to weight ratio, economics, specific mechanical properties and corrosion resistance are required. Injection molding machines are necessary to produce these geometrically complex components now expected of industry. Because many existing molding machines are cyclic they possess an inherent economic loss due to dwell (idle) time. This paper presents some observations obtained from the design of a prototype continuous cyclic injection molding machine together with some preliminary results from investigations into working of the injection molding machine.
Atmospheric Process for Polar Olefin Copolymers and Terpolymers by Single Site Catalysts
Synthetic resins are broadly grouped according to properties such as crystalline vs. amorphous, plastic vs elastic, thermoset vs thermoplastic, insulating vs conductive, polar vs nonpolar, etc. Copolymers of ethylene and polar comonomer possesses very useful properties. They are currently manufactured using free radical initiators at elevated temperature and pressure. These plants are very expensive to construct, so there is urgent need for more economical atmospheric process to replace the aging existing plants. Ziegler catalyst is the most versatile and high performance system to polymerize ethylene and ?-olefins. However, its group IVB organometallic catalytic species are easily poisoned by ? or ? Lewis basic moiety of a polar monomer. Several approaches have been developed to overcome this limitation. They are the use of functional derivative of polar monomer,2-4 generate polar functionality by reaction with vinyl groups,5-8 or develop new catalysts based on late transition metal complexes.9 These methods suffer from either being specific to a single type of polar functionality, or low in productivity. The catalyst cost can be prohibitively high as in the case of Pd catalysts.9 We have developed a general method to polymerize at ambient temperature and pressure any common polar monomer using either group IVB or VIIIB precursor of single-site Ziegler catalyst. The results are presented here.
Surface Modification of Conducting Polymer Films
Thin films of polyaniline, polypyrrole, polythiophene and poly(ethylenedioxythiophene) are electrochemically grown on indium-tin oxide-coated glass plates. The samples are then exposed to dodecanethiol or 1H, 1H, 2H, 2H-perfluorooctanethiol. These nucleophiles react with the surface to give near-monolayers of the thiols. Contact angle analysis and AFM studies reveal that significant changes result from these treatments, altering the surface energies of the materials. A method for quantifying the alteration in the surface properties and for examining the homogeneity of the coverage is detailed. This involves the modification of the AFM tip by attaching a 20 µM sphere and making force-distance measurements of the surface under a layer of distilled water.
Foaming of PS/Wood-Fiber Composites in Extrusion Using Moisture as a Blowing Agent
This paper presents an experimental study on foam processing of PS and HIPS/wood-fiber composites in extrusion using moisture as a blowing agent. Wood-fiber inherently contains moisture that can potentially be used as a blowing agent. Undried wood-fiber was processed together with PS and HIPS materials in extrusion and wood-fiber composite foams were produced. The cellular morphology and volume expansion ratios of the foamed composites were characterized. Because of the high stiffness of styrenic materials, moisture condensation during cooling after expansion at high temperature did not cause much contraction of the foamed composite and a high volume expansion ratio up to 20 was successfully obtained. The experimental results showed that the expansion ratio could be controlled by varying the processing temperature and the moisture content in the wood-fiber. The effects of a small amount of a chemical blowing agent and mineral oil on the cell morphologies of plastic/wood-fiber composite foams were also investigated.
Employee Non-Compete Contracts: Where Is the Value?
This paper will discuss the reason for non-compete contracts coming about and the benefits and problems associated with this non-compete for both the employee and the employer. General interviews with employers that have non-compete contracts for the staff verses employers that do not. Also interviews with employees that have non-compete contracts and those that do not. There will be discussions with employers and employees who had problems and/or discussions about their contracts involving lawyers. Many employers feel that if an employee does not have a non-compete contract then there can not be any consequences of hiring this person even if he/she has competitive information. This is incorrect as will be discussed later. The conclusion should be that the individual should decide if he or she should have a non-compete contract with their employer and what information the employee gives to the new employer, should be at the ethical determination of the employee.
Deposition of Conducting Polymers into Porous Semiconductors and Properties of Semiconductor/Polymer Composites
The work reviews the state-of-the-art in the deposition of different types of conducting polymers (CP) into porous semiconductor (PS) matrices. Deposition processes range from electrochemical and chemical polymerisation of monomers to vacuum deposition of oligomers. Special emphasis is made on the problem of preserving the semiconductor material properties intact during the polymer deposition. Optical (luminescence, absorption) and electrical (dc conductivity and ac electrical impedance) properties of CP/SP matrices are studied and their comparison with those of non-capped porous semiconductors and bulk conducting polymers is given.
Why It Is Difficult to Mold Parts within Tolerance in Pattern Based Injection Mold Tooling
Over the last few years, a tremendous amount of work has been done to develop alternatives to conventional machining methods of creating injection mold tooling. Because such alternative methods offer the potential to create injection mold tooling for prototype purposes faster or less expensively than conventional machined tooling, there has been a great deal of interest in alternative tooling. A number of older tooling creating methods have been revived and several new methods have been developed and reported on. Most involve creating a pattern against which the tool is formed, usually by casting a tooling material against the pattern or a copy of the pattern. In general the tooling created by these methods can be referred to as pattern-based tooling. In October, 1997, Dr. Paul Jacobs delivered a paper which defined the relationship between dimensional variation in a cast tool resulting from variations in shrink and the mean shrink level of the tooling material(1). This groundbreaking work provided fundamental information on tolerances in alternative tooling processes. In addition it clearly identified the role shrink in the tooling material plays in determining the ability of any particular tooling process to hold tolerances. Specifically, Jacobs showed that shrink is not uniform; it is in effect a random variable distributed normally around a mean. Furthermore, he showed that the standard deviation of that distribution is proportional to the mean shrink rate. With that information, it is possible to predict the range of dimensional errors in a tool, or tolerance, that result from variations in the shrink rate of the tooling material. As valuable as that work is, its use is limited because it only includes the effects of shrinkage in the tooling material. Other factors such as the accuracy of the pattern building process, any errors introduced in finishing the pattern and variations in shrinkage of the molded part will contribute additional error and make the toler
Opportunities for Solid Freeform Fabrication in Prototyping and Manufacturing
Solid Freeform Fabrication (SFF) of parts and components is an area of active development and tremendous potential. SFF is a layered manufacturing technique in which the required component/part is built from a CAD model. This model is mathematically sectioned into a number of layers and a material deposition or tool path is generated for each layer. A fabricator uses this tool path information to build the part, layer by layer. This family of manufacturing techniques offers several advantages over traditional routes, such as: no part specific tooling, fabrication of complex geometries to net shape, and greater design flexibility. There is also a significant potential for lowering cost of prototyping as well as small-scale manufacturing. Many of the SFF routes that are currently available are for fabrication of plastic, ceramic and metal parts. Some of these SFF techniques are, Stereolithography (SLA) Laminated Object Manufacturing (LOM) or Computer-Aided Manufacturing of Laminated Engineering Materials (CAM-LEM), 3D Printing (3DP)/Sander Prototyping (SP)/Droplet Deposition, and Selective Laser Sintering (SLS). Most of the SFF routes are similar in concept, i.e., model generation, followed by mathematical sectioning and layerwise building, and differ only in the method of layer fabrication. In order to manufacture ceramics and metals, the polymer based SFF methods have been adapted using powders as a second phase in a base polymer or fluid. Parts can then be made directly or indirectly. In the direct route, a green ceramic part is directly manufactured to shape. Alternately, in the indirect process, parts are made by infiltrating a ceramic or metal slurry into a polymer or metal mold made by SFF. Subsequent processing of these green parts (i.e., debinding/drying and sintering) is similar to that of traditionally manufactured components and results in a near net shape sintered part.
Time to Market & Rapid Tooling an OEM Prospective
Time to market is the item that is critical to survival in the international and domestic markets. Considering that almost all products today have some plastics compounds or are entirely produced in plastics, plastics engineering becomes a critical path technology. In the plastics industry there is one item that drives time to market and that is tooling. How a company approaches rapid tooling will directly affect time to market and can severely affect product release. The machine tool suppliers recognized these issues several years ago. Toolmakers now have machining centers that can reduce chip-cutting time by 40-50%. This shortens tool fabrication time dramatically. We should get our tool in 6-8 weeks instead of 14-16 weeks. However it doesn’t happen that way in real life. Tool fabrication accounts for less that 40% of the tool build time. Design and design modifications have a stronger impact on tooling deliveries. What will make the greatest impact in reducing product development time for OEMs is defining product requirements up front and concurrently deciding on the best approach in rapid tooling. This presentation will review how the injection molder and the OEM can utilize these assets and engineering personnel to achieve the best rapid tooling technology to meet design requirements. Rapid tooling will not satisfy the customer’s needs if it does not work!
The Development of Medium to Long Run Tooling with a View to Rapid Manufacturing
As emerging technologies develop and existing technologies mature, rapid manufacturing of plastic injection molds has become a reality. Molded plastic parts out of the desired material in days, not weeks was once a dream. With the advances in both mold manufacturing materials and rapid prototyping equipment this is now a reality. Using non-traditional manufacturing methods to produce traditional injection molds, product development cycles can be drastically reduced. With the recent development of materials for rapid prototyping machines, manufacturing molds is now possible using current technology. Using materials for short run tooling, tools can be manufactured in 3 to 7 days that are capable of producing 50 to 250 parts. Long run materials like stainless steel are capable of 100,000 plus shots and can be produced in 5 to 15 days. The technology used to produce these molds is selective laser sintering (SLS). A solid model is produced of the cavity and core and using a laser the mold is produced layer by layer. A heat treat furnace is required to harden the inserts and infiltrate to full density. Very detailed part geometry's are possible. Mold details can be incorporated into the solid model and manufactured into the inserts. Cooling lines both conformal and traditional, ejector pin holes, runner and gates, SPRUE and SPRUE pullers can all be incorporated. The inserts can be polished to a diamond finish, textured using traditional methods, welded, and machined using conventional machining equipment and techniques. These molds are capable of molding both thermoplastic and thermoset materials. Normal pressures and molding cycles are possible. Research and development underway promises to push the envelope of this technology even further. Advances in new materials, techniques and equipment will enhance or obsolete current technology. This technology has the potential to significantly impact the plastics industry.
Development of Structural Hierarchy in Injection Molded Dynamically Vulcanized PP/EPDM Blends
When injection molded, the polymers exhibit complex structural hierarchy from angstrom size levels up to optical. This is particularly true when the polymers have multiple phases such as in the case of polymer blends. It is as a result of a complex thermal -deformation history that this process imparts on the flowing fluid as it subjects it to severe thermal deformation gradients during the course of its formation. This dependence results in a three dimensionally varying structure and corresponding properties1,23. This complexity further increases with a composition as a variable in a multiphase blends systems as in the case of dynamically vulcanized PP/EPDM blends. In order to understand the details of the spatially varying structural hierarchy, one needs to investigate it using a variety of characterization tools that allows the observation of the localized structure at different size levels. For this purpose, we developed a unique microbeam WAXS instrument that allow us to probe the spatial variation crystalline regions for their order and orientation quantitatively. In this research, the effect of blend composition and processing conditions on the development of structural hierarchy in injection molded parts were studied through optical microscopy and matrixing microbeam X-ray diffraction technique and thermal analysis techniques.
Effect of Pulling Speed on the Sizes of the Liquid, Gel and Solid Zone during Thermoset Pultrusion
The temperature and the degree of cure distributions inside a thermoset composite profile during the pultrusion process are calculated numerically using the finite difference method. The degrees of cure at the beginning of the gel and the solid zones i.e ?GL and ?GS are determined using appropriate experimental techniques. These results enabled us to predict the location and the size of the liquid, gel and solid zones inside a pultrusion die. It is found that the pulling speed affects the size and the position of each zone considerably. The relationships between the sizes of these zones and the pull-force is discussed.
Banning Heavy Metal Pigments in Minnesota - The Next Iceberg?
For several years the Minnesota Legislature, guided by the MPCA (Minnesota Pollution Control Agency), has been evolving a law to significantly reduce heavy metal pigment use in the state. The finalized law takes CONEG (Coalition of Northeastern Governor's) guidelines to a higher level. CONEG was intended to reduce the amount of heavy metals in the consumer waste stream by limiting their use in disposable packaging materials. The Minnesota law applies CONEG limits of lead, cadmium, mercury and hexavalent chromium to all pigments, including plastic colorants. This paper will review the evolution of this law. What could this mean to the plastics industry if similar events occur in other states?
Numerical Investigation on Mixing in a Pin Mixing Section for Screw Extruders
Non-Newtonian, non-isothermal, 3D finite element simulation of mixing performance in a pin mixing section with different axial gap of pins has been carried out according to their realistic configurations. To learn and to compare the local mixing performance in a standard screw and a pin mixing section, the local mixing efficiency distribution proposed by J. M. Ottino was calculated. Also RTDs of these mixers were calculated to try to measure mixing. Then, the integration of above parameters, which was referred as integral mixing efficiency, gave a quantitative judgement of total mixing ability of the mixer. The calculated result showed a non-linear dependence of mixing ability of a pin mixing section on the axial gap of pins. Finally, the calculation result was compared with the experimental one obtained in our previous study.
Chromatography-Infrared Spectroscopy Characterization of Polymers
Polymer systems demonstrate simultaneous multivariate distribution of properties (molecular weight, composition, chain configuration). These molecular properties directly effect the physical properties of the polymer system. The polymer engineer typically adjusts these molecular properties in an attempt to optimize the end-use properties of a polymer. The characterization of the distributed molecular properties and their relationship to end-use physical properties is thus a key to the tailoring and optimization of a polymer product. Polymer analysis methods can be divided into three categories: methods that measure fundamental molecular properties, methods that fractionate a polymer, and physical test methods. Table 1. illustrates some of the principal techniques in each category. Molecular composition and configuration frequently varies across the molecular weight distribution of a polymer. As a result, a spectrum of an whole polymer sample provides at best a limited characterization of the polymer. This paper describes a technique whereby infrared spectroscopy is combined with one of the fractionation methods to obtain a more insightful characterization of a complex polymer system.
Thermal Stabilization of Polymers Containing Residual Catalysts
Residual polymerization catalysts are known to promote degradation reactions in many polymeric materials. Such reactions were studied in poly(methyl methacrylate) (PMMA) doped with a typical catalyst at temperatures slightly above Tg using thermogravimetric analysis. Several novel approaches to minimizing the adverse effects of residual catalyst on thermal stability were investigated. Extraction of residual catalyst using liquid CO2 and a fluorinated chelating agent was shown to significantly improve the stability of PMMA film. Encapsulation of the residual catalyst using strongly a binding chelating agent, an azo-derivative of a crown ether, is also shown to enhance thermal stability.
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