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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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.
Hyperboidal Rotary Cutter - Modeling and Application in Recycling of Polyethylene Film in Pelletizing-Line Aggregation
Recycling of polyethylene films  is carried out by their disintegration into regular flakes - the process is difficult because of dimensional (large surface, small thickness) and property (flexibility and rebound) characteristics of the films. The disintegration is typically carried out with the knife mills  which constitute the first units of the recycling line. Traditional mills operate on the principle of pressurized knife cutting  since it allows to carry on the disintegration at a narrow slit between cutting edges of the fixed (stationary) and the mobile (rotary) knives of the mill. Because of parallel arrangement of the edges and large surfaces of the films which call for high cutting forces the process induces strong vibrations [3, 4]. The latter are eliminated in the hyperboloidal - rotary cutting mill developed recently and evaluated in our lab .
Polymers of Controllable Rheology - Volume Viscosity and Implications for Modeling of Processing
Shear and compression rheometry of representative boronsilane (BSI) polymers and corresponding LDPEs demonstrates feasibility of modeling processing of the latter using BSIs at an ambient temperature. Industrial-range rheology of BSis was shown to be relevant for the performance in shock absorbers. Boronsilane polymers [BSI] constitute an unique class of polymers [1,2] of readily adjustable ratio of viscous and elastic components of their (Tab. 1) viscoelastic response. Level of the response at an ambient temperature is comparable with that of polymer melts at processing temperatures [3,4]. BSIs display also high and adjustable level of recoverable compressibility (resilience). These characteristics imply application in: • rheometry e.g. for identifying local stress distribution in the melt flow of o polymer using calibrated stress traces  embedded in 'rheoequivalent' BSI in an ambient temperature experiment; • technology such as • ambient temperature performance testing of the rapid prototype"  plastic molds and dies which are less expensive than these made of metals • high performance shock absorbers of readily adjstable resilience . Here we aim at: • comparison of ambient temperature capillary rheometry of representative 'elastic' and 'viscous' BSI (designated as 'elastomer' and 'plastomer' resp.) with the melt rheometry of LLDPE a IUPAC melt rheology standard [7a]. In both cases technically significant range of stress was covered; • comparison of the volume viscosity and the time dependent compressibility of the 'elastomer' and the 'plastomer'. "
Clear, Radiation Sterilizable, Autoclavable Blends Based on Metallocene Catalyzed Propylene Homopolymer
In a previous paper the formulation and characterization of clear, radiation sterilizable, autoclavable blends of Ziegler-Natta catalyzed propylene homopolymers and metallocene catalyzed plastomers was described. These studies have been extended to blends in which the propylene-based component is also produced by a metallocene catalyst. We have found that higher plastomer content is required in blends with metallocene catalyzed polypropylene than with Ziegler-Natta produced material to provide comparable radiation resistance. Despite the higher plastomer content, the blends with metallocene polypropylene are similar in stiffness and resistance to softening at elevated temperature, yet clearer than the Ziegler-Natta polypropylene based compositions.
Commercial Epoxy + Monomer Liquid Crystal Epoxy Blends: Compatability and Curing Kinetics
Epoxy resins are known to have numerous applications. To improve their performance of the epoxy, we are applying molecular reinforcement by using polymer liquid crystals (PLCs). PLCs are well known for their excellent dimensional stability, good mechanical properties, high temperature usability, and outstanding environmental resistance. A novel retention class of LC thermosets can be obtained by endcapping mesogenic rigid rod molecules with reactive glycidyl groups. These thermosets potentially combine the performance of an epoxy resin with the excellent properties of LC. We have studied the simultaneous cure of the monomer liquid crystalline epoxy (diglycidyl ether of 4,4'-dihydroxybiphenol) with an anhydride cured diglycidyl ether of bisphenol F (DGEBP-F) epoxy. As a first step to determine optimum conditions for network formation, we report on the curing kinetics of molecular reinforcement of epoxy with a monomer liquid crystalline epoxy (MLC). The study was done by Differential Scanning Calorimetry (DSC) using autocatalytic expressions. Dynamic Mechanical Analysis (DMA) is used to verify compatibility of the blended systems by investigating the glass transition temperature as a function of %composition.
ESCR Behavior of Plastic Materials in Medical Environments
Besides other facets of product development, it is imperative for medical device manufacturers to take great efforts through proper evaluation and consideration of material properties under practical conditions to prevent product failure at the end-uses. The environmental stress crack (ESCR) induced by chemical agents plays a significant role on material performances. In this contribution, in-depth studies have been carried out on different medical plastic materials, such as polycarbonate, copolyesters, ABS, acrylics, rigid thermoplastic polyurethane and their blends. More attention will be focused on a copolyester material for its unique ESCR behavior. Variation of chemical agents (such as different types of hospital disinfection solutions) have great impacts on physical and functional properties. Various plastics shows distinct environmental stress cracking phenomena under different conditions. Mechanisms of ESCR phenomenon under different environments have been explored. Fibril reinforcement by cold crystallization and chain session by hydrolysis of the copolyester may have contributed to its excellent chemical resistance against a wide range of chemicals and its catastrophic failure in acidic or basic environment. In addition, appropriate definition of product failures is also critical in making materials decisions.
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