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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Fundamentals of the Tenter Frame Process for Biaxially Oriented Film Manufacturing as Applied to Polypropylene Polyester and High Density Polyethylene
Biaxially oriented films of polypropylene (PP), polyester (PET) and high density polyethylene (HDPE) can be made in several different processes. The tenter process will first be shown in overview to describe the function of each of the primary manufacturing steps (coextrusion, casting, machine direction stretching, transverse direction stretching, surface treatment and winding). Next the primary stretching steps and equipment configurations will be defined and characterized in terms of process and material variables and the film properties produced. From a processing focus, the primary process steps may be considered and evaluated as some form of rheometer, either for melt or solid, and these ideas will be introduced and evaluated as a means of understanding the process / film property interactions.
Experimental Study and Model Predictions of Rheological Behavior of Short Fiber Composites
A set of experimental data is carried out on short fiber suspensions in viscoelastic fluids. Parameters such as fiber volume fraction, fiber length and pre-shearing are studied. Transient tests on pre-sheared samples showed that fiber orientation depends on both the strain and the rate-of-strain tensors. Increasing fiber concentration and aspect ratio increases rheological material functions in the low shear rate region. In the high shear rate region, the effect is less pronounced. The experimental data are compared to a rheological model based on the modified Jeffrey equation. The theoretical results are found to be in good agreement with most experimental data. Further changes to the original model were necessary to be able to predict the rate-of-strain-dependent fiber orientation and the observed behavior of the considered material functions.
Fast Fourier Transform Analysis of Melt Fractured Extrudate
The phenomena of extrudate swell and associated instabilities have received substantial attention, yet they are still the cause of considerable debate1-9. Laser micrometers are used routinely to measure extrudate swell in capillary rheometers as well as critical profiles like catheter tubing. The speed of typical laser devices was on the order of 200 samples per second. The commercial availability of newer laser technology allows measurement on the order of 700+ samples per second with accuracy’s in the 2.75 micron range. Using these high speed laser micrometers it seemed feasible that the analysis of various types of gross melt fracture and sharkskin might become more quantitative if viewed in the frequency domain i.e. amplitude of diameter variation as a function of frequency in time. Similarly the frequency of the diameter variation can also be viewed as a function of linear distance on the extrudate. The finger print of the amplitude spectrum rather than still photography or nebulous descriptive terminology might be used to characterize the phenomena and, perhaps, give some insight into it’s origin. This paper is our scouting work on this idea.
Recycling of Xerographic Toners
The objective of this research is to find ecologically and economically acceptable routes to utilize excess xerographic toner from manufacturing and returned toner cartridges. This black toner is a polymer composite comprised of a styrene-based copolymer, carbon black and other additives. The mechanical properties of toners are specifically designed to allow attrition to 10-20 µm particles. Thus the bulk mechanical properties are not desirable for load bearing applications typical of consumer plastics. Reactive and non-reactive blending of toner with other polymers have been used to enhance the mechanical properties. The blends and alloys produced exhibit a transition from brittle to ductile behavior as exhibited by impact energy data. Thus a family of polymeric systems of variable properties versus cost compromise can be created.
Effect of Grafting Monomer on the Performance of Thermoplastic Vulcanizate of Polypropylene/Polystyrenic Block Copolymer/Polyester Elastomer
The effect of grafting monomer on the performance of thermoplastic vulcanizates (TPVs) of polypropylene (PP) / styrene-ethylene-propylene-styrene copolymer (SEPS) / polyester thermoplastic elastomer (TPEE) has been studied. Glycidyl methacrylate (GMA) and maleic anhydride (MAH) were selected as grafting monomer. MAH grafted sample was observed to give excellent mechanical properties and have higher gel ratio which was determined as insoluble portion after extracted in 60°C acetone and subsequently in 65°C chloroform.
Integrating Thin Wall Molder's Needs into Polymer Manufacturing
Polyethylene (PE) injection molded rigid containers are widely used for food packaging and promotional drink cups. Molders of these containers have well-defined processing needs and molded part requirements. Likewise, the polymer manufacturer has well-defined manufacturing and analytical methods for characterizing resin properties. This paper presents a unique method of translating the molder's needs back to polymer melt index and molecular weight distribution. The introduction of an Isometric Spiral Flow Chart" provides the basis for this new approach. A nomogram for optimizing injection melt temperatures when transitioning from lot-to-lot is also presented. Utilizing this information injection molders can maximize their production."
Maximize Barrier Performance of Reduced-Gauge HDPE Films
Multi-layer high-density polyethylene (HDPE) films are used for numerous food-packaging applications because of their superior water vapor transmission rate (WVTR). Economic factors have caused film converters to produce thinner-gauge films to reduce raw material costs. At thinner gauges, WVTR's can increase faster than the expected inverse relationship with thickness. This paper presents laboratory data that expand on an ineffective film thickness concept first discussed by Talwar . Correlation's showing the effect of resin properties on this ineffective film thickness are presented. Utilizing this information, the barrier performance of multi-layer film structures can be maximized.
Development of a Twin Screw Injection Molding Extruder
This paper documents the development of a novel injection molding machine, the Twin-screw Injection Molding Extruder (TIME). A reduction of capital equipment and thermal degradation is achieved by combining the compounding ability of a Twin Screw Extruder (TSE) with the final part fabrication techniques of an injection molding machine. Tests conducted on a bench-scale model of the machine have shown that an entirely new set of process parameters comes into prominence due to the combination of compounding and injection molding processes. The main control objectives also differ from a traditional injection molding process.
Residence Time Analysis for Twin Screw Extruders
This paper presents and experimentally validates a physically motivated model for predicting the mean residence time in twin screw extruders. Accurate estimation of the mean residence time and the propagation delay through a plasticating extruder is critical for implementing feedback control schemes employing sensors mounted along the extruder. Experiments were carried out on a 30 mm Krupp Werner and Pfleiderer Co-rotating twin screw extruder equipped with reflectance optical probes over the melting section, mixing section and at the die. The residence time distributions for twelve operating conditions and two screw geometries are supplied. The mean residence times predicted by our model are in good agreement with the experimentally measured mean residence times.
3D FEM Simulation of the Stretch Blow Molding Process with a Two-Stage Material Model
In this paper we proposed a viscoplastic material model for PET, which was based on the uniaxial material tests conducted on the newest type of Meissner rheometer. The tests have been performed with the constant strain rates varying from 0.01 to 1 (1/s), at the temperatures ranging from 90°C to 150°C. The proposed model could precisely take into account the effects of strain hardening, strain rate sensitivity, variation of the hardening index, and temperature changes. This model has been implemented into our nonlinear finite element code. Very good agreement has been verified through the comparison between the blow molding simulation result and the measurement.
A Numerical Virtual Process Modeler Based on Computer Aided Engineering Software for Injection Molding
A numerical process modeler based on back-propagation neural networks has been employed for emulating the process of injection molding. Contrast to the Computer Aided Engineering simulations, the processing parameters, which are bounded by the process window, are used by the modeler to calculate the selected properties of interests, namely the outputs, by making use of a set of Radial Basis Functions. A systematic procedure for constructing the model parameters has been illustrated based on standard procedures derived from Design of Experiment to obtain the basic training data from the CAE simulations. After going through the iterative training, the process modeler was established for emulating the molding process. Verifications on the process modeler have been shown by randomly choosing the processing parameters in the process window.
TPE Overmolding Compounds for the Next Millenium
This paper describes the use of TPE compounds for over-molding on to engineering thermoplastic resins. These TPE compounds have a wide range of hardness and are bondable to a wide spectrum of engineering thermoplastic and engineering thermoplastic elastomer substrates. They exhibit very smooth, tack-free, mar resistant surface for the very soft compounds. The bonding between the TPE and the substrate resists environmental changes such as hot air aging and water immersion. The adhesion data and other physical data, adhesion quantification methods, suggested processing conditions and selected applications of these TPE over-molding compounds will also be presented. Theories in TPE over-molding or co-extrusion are discussed.
Reusing XLPE from Electrical Cable Waste: Cable Separation, Processing and Blend Properties
The recycling of power transmission cable was investigated by using different kinds of separation and reprocessing methods. The cross-linked polyethylene (XLPE) insulation of the cable, serving as a part of a broader study of the reprocessing of cross-linked thermoplastics, presented a specific challenge in separation. Separation of the XLPE from the other components of the cable was attempted by thermo-chemical, microwave and thermo-mechanical means. All three methods were able to separate the cable, and the relative advantages and disadvantages are discussed. Following separation, the following processing techniques were attempted: compression molding, extruding, and injection molding with and without preheating XLPE crumb. It was found that by preheating the XLPE and injection molding with high injection pressure, the neat XLPE could processed. Possible mechanisms for the flow and reconsolidation of XLPE crumb were hypothesized and investigated. Blends of XLPE crumb (0.3 to 3 mm particles) in either HDPE or LDPE were prepared and the tensile properties were evaluated.
The Effects of Filler Size on the Properties of TPO Blends
The effects of filler size on the properties of a TPO blend were examined using wollastonite and talc with particle sizes ranging from 1.2 to 40 µm. While addition of filler produced significant changes in the mechanical properties of the blend, filler size only affected impact strength. However, filler size, filler coating, and injection speed had a major effect on the surface properties of the blend. Faster injection produced denser shear zone layers" which exhibited better scratch resistance and poorer paint adhesion than slower injection. Scratch resistance and paint adhesion also decreased with increasing filler particle size. Filler coatings altered the scratch and adhesion properties of the PP blends."
Relationship between Structure and Rheology of Constrained Geometry Catalyzed and Metallocene Polyethylenes
Constrained geometry catalysts make it possible to control independently various molecular characteristics. The polymers produced with these catalysts are of great interest commercially and make possible the systematic study of the effects of various molecular characteristics on rheological behavior. Several constrained geometry catalyzed and metallocene polyethylenes were subjected to a comprehensive rheological evaluation including linear viscoelastic behavior and non-linear viscoelastic behavior in shear and extension. The effect of molecular weight, short chain branching and long chain branching on the rheology of these materials are described. Based on these results, a procedure was developed for quantifying LCB using linear viscoelastic data and backbone MWD.
Numerical and Experimental Studies of 3-Dimensional Thermoforming Process
Two Acrylonitrile-Butadiene-Styrene (ABS) polymers were thermoformed, and their behavior was compared with numerical simulation. Hot tensile and dynamic oscillatory shear tests were performed at various temperatures to characterize the polymers. Hot tensile test results were used to obtain the material parameters for simulation and to check the relative usefulness of these test parameters in the actual thermoforming process. The thickness distribution obtained from experiments was compared with simulation results. It shows that simulation results based on hyper-elastic rubber like model can predict the deformation behavior of a sheet reasonably well. We could also find that the temperature sensitive polymer in hot tensile test shows more temperature sensitive thickness distribution in actual thermoforming process.
Plastics in the World to 2020
World changes are accelerating in the next ten years, with global vision, instantaneous communications, access to disposable income for increasing numbers, growing needs for infrastructures, housing, roads, telecoms, energy and water distribution networks. Major changes are happening in the world, in the last years of this century, and the turn of the next. We live in extraordinary times. This is not a crisis, it is a major change, long, often difficult to bear, uncertain for the three decades, 1977-2007, coming after the Thirty glorious, very short on a historical scale. It is a change of world, of life and of pace. • A change of world, that has become global in less than fifteen years, with a plus, democracy winning. • A change of life patterns, with the coming of the telectronic world, the almost immediate access to information and other people, a novelty comparable to the new fast transportation of the last one hundred years, yet with an impact even stronger and more universal. • A change of pace. Europe took a century to develop, the US, fifty years, Japan, twenty five years, and the most active emerging countries now may take ten or fifteen years, from ploughs to computers, notwithstanding the recent hurdles and crises. This momentum is a major phenomenon for mankind, even more than the Renaissance or the Industrial Revolution, but immediately visible and happening much faster. The average annual rate of growth of 7.5% that brought all solid polymers from 8 million tons in the world in 1960, to 120 million tons in 1997, is to continue, reaching over 210 million tons in 2007 and close to 400 million tons in 2020, using a more conservative annual rate of 5%. The topic is vast, and to give it some perspective in a very short time, it is divided into four parts: • The world economic scene. • Plastics consumption in the main countries and areas of the world. • Plastic markets, with a new split into disposable products, durable goods, building of the inf
Use of PP-g-DEM in Short Sisal Fiber-Reinforced Polypropylene
In this study, the mechanical properties of composites obtained by different combinations of untreated and acetylated short sisal fiber with polypropylene and polypropylene-g-DEM were evaluated. Two PP were employed, PP1 and PP2. The last one was functionalized with diethylmaleate via extrusion. The composites were prepared using 20% of fiber in an intermeshing corotating twin screw extruder followed by injection molding. The results showed that composites containing fiber displayed superior mechanical performance and that PP2-g-DEM used as a third component (coupling agent) increased the elongation at break of composites. However, the acetylated fiber-PP1 composite showed the highest tensile modulus.
Investigation of the Effects of Deformation Rate on the Fracture Toughness of Polymers
Determining the fracture toughness of a polymer is important because it can be used to estimate the relation between the stress-to-failure and the defect size for a polymeric material in actual use conditions. Since polymers are viscoelastic materials, the fracture toughness as well as other mechanical properties will depend on the time and temperature of the test conditions. The effect of strain rate (time) on the mechanical properties of polymers such as Young’s modulus and yield and ultimate stresses are well known and studied [1-3]. High strain rate behavior of commercial polymers is of great interest to plastic part designers and yet these measurements are not readily available in the literature. The stress-strain measurements, either in tension or flexural mode, in the impact range are not easily obtained because it requires special testing systems. Low strain rate tests are usually done using a standard universal Instron testing system. Intermediate rates can be obtained by pendulum tests such as Charpy, Izod impact testers or drop tower impact tests. High strain rates can be acquired by several methods such as Hopkinson’s tensile bar apparatus by the impact of a projectile or a special testing system such as MTS high strain rate testing system. The aim of this article is to investigate the effects of strain rate on the fracture toughness of polymers such as polystrene (PS), polymethylmethacrylate (PMMA), polyethyleneterephtalate (PET), high density polyethylene (HDPE) and various compatibilized blends of HDPE/PET.
Crystallization of Ethylene-Octene Copolymers at High Cooling Rates
The crystallization behavior of a series of ethylene-octene copolymers synthesized using metallocene catalysts has been studied using the Ding-Spruiell method of rapid cooling. In conventional crystallization experiments it was found, as expected, that the spherulite growth rates varied with octene content and molecular weight. When studied at rapid cooling rates the polymers generate their own pseudo-isothermal crystallization temperatures, in agreement with Ding - Spruiell's studies on other systems, however, at the lowest temperatures of crystallization, the spherulite growth rates of all of the copolymers studied merge and are virtually indistinguishable. The results indicate that there is a major change of crystallization mechanism under these conditions, of considerable relevance to polymer processing operations.
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