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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Residence Distribution Models for Twin Screw Extruder
Transformation of the residence time distribution (RTD) to give both the residence volume distribution (RVD) and the residence revolution distribution (RRD) yields new physical insights into the extrusion process. These new tools motivate the development of a simple residence distribution model which characterizes the partially filled and fully filled screw sections and is capable of distinguishing between screw configurations and operating conditions. A least square error fit method is used to identify the parameters of the RTD model and it is indicated that the model function is appropriate to describe the RTD experimental data. The model for the RTD is validated on the analysis of data collected from the extrusion of polyethylene on a 30 mm Krupp Werner and Pfleiderer (W&P) Co-rotating twin screw extruder.
Mean Residence Time Characterization in Co-Rotating Twin Screw Extruder: Screw Configuration Comparison
Many industrial processes are described by residence time distribution functions (RTD). Experiments were carried out on a 30mm Krupp Werner and Pfleiderer co-rotating twin-screw extruder (CoTSE) equipped with reflectance optical probes to study the residence functions of different screw geometries to distinguish them. Theory described by Gao, Bigio, et al, shows that the mean number of screw rotations can be found from these RTD functions from the product of the screw speed and mean residence time. This equipment was used to show that the mean number of screw rotations is proportional to the inverse of the specific throughput. In addition, different geometries exhibit different functional relationships between the mean number of screw rotations and the inverse of the specific throughput.
Fundamentals of Polymer Process Control
Process control has been recognized as an important means of improving the performance and consistency of thermoplastic parts. However, no single control strategy or system design has been universally accepted, and the manufacturing systems continue to produce defective components during production. This paper provides an overview strategies in polymer process control, and discusses some of the difficulties posed by the complex and distributed processes. Objectives for 'intelligent' process control are presented. Finally, the potential benefits of integating product and process design are demonstrated.
An Overview of Optical Brighteners for Copolyester Resin Extrusion Paper Coating Applications
Several topics will be covered in the Take Home Information" to aid the reader in a better understanding of optical brighteners use in extrusion coating applications. They include: • What is an optical brightener? • What is the mechanism? • How to formulate with optical brighteners in an extrusion coating grade copolyester resin. "
On-Line Monitoring of Free Radical Grafting in a Model Twin Screw Extruder
The on-line monitoring system of Raman spectroscopy was developed to monitor the grafting identification and level of grafting of glycidyl methacrylate (GMA) onto low density polyethylene (LDPE). The reactive extrusion and melting behavior of GMA and LDPE was monitored by a fiber optic probe through the glass windows mounted on the model non-intermeshing counter rotating twin screw extruder. Monitoring concentration of GMA along the screw extruder was carried out to determine the reaction level.
Sorption Properties of PAN/Chitosan Composite Fiber
Composite fiber of PAN and chitosan was obtained by hydration-melt spinning process. The fiber showed a fibrillar structure which can be converted easily into pulp-like structure by beating. PAN/chitosan pulp showed much higher amount of acid dye uptake than chitosan powder or activated carbon which is used for the color removal from the waste water of dyeing industry. This better sorption for the composite fiber is considered to result from the relatively large surface area due to its pulp-like shape.
Epoxy + Montmorillonite Nanocomposite: Dynamic Mechanical Analysis
Polymer nanocomposites are of growing interest. Epoxy resins are an important matrix resin for aerospace and electronic composites. Increasing the mechanical properties of epoxy resins is vital to increasing their long term reliability. Here we investigate the addition of a montmorillonite layered silicate to an epoxy resin using dynamic mechanical analysis. The effect of montmorillonite on the glass transition and beta transition are examined. Frequency - temperature sweeps betweeen 133K to 393K at 0.0159 to 159 Hz were recorded. Master curves were determined graphically and the shift factors analyzed for changes in activation energy and WLF constants. A narrow range of reinforcement concentration was identified where desirable impact properties might be found.
Isolating the Effect of Reaction on the Phase Inversion of Model PA/PS Blends
This paper aims to distinguish the effect of reaction on morphology development during polymer blending from other confounding parameters, particularly the rheological differences between the reactive and nonreactive components. Many works have focused on components that are rheologically matched at the processing temperature. However, based on previous results that have shown the importance of the melting regime in morphology development, it is crucial that the components be rheologically matched throughout the experimental temperature range. In this work, we use a model addition protocol to limit the morphology development to a temperature range where the reactive and nonreactive polystyrenes exhibit an excellent rheological match. The interfacial reaction was found to accelerate the pace of initial morphology development, where sheets are pulled off the solid pellet core during melting. Phase inversion began earlier but finished later in the nonreactive blend.
The Effect of Preform and Bottle Design Characteristics on the Performance of PET Water Bottles
With the increased demand for bottled water worldwide, PET packaging has had to adapt to meet consumers' demands and bottlers' needs. During the development of a new water bottle, potentially contradictory considerations must be addressed. In this study of a 0.5L water bottle, the effect of bottle design, preform design, and resin on bottle performance and economics was explored. A bottle with an arch shoulder and deep ribs or belts" using a high stretch high IV preform had a good combination of mechanical properties. The aesthetic impact of the bottle design and the longer cycle time for injection molding the preform might be the drawbacks of this choice."
Performance Evaluation of Polyethylene-Terephthalate (PET) Angioplasty Balloon Designs via Blow Molding Simulation and Structural Analysis
The design of high performance PET balloons for percutaneous transluminal angioplasty (PTA) requires an in-depth understanding of relationships between manufacturing process conditions and resulting material thickness and property distribution in the geometry chosen for a balloon catheter. In this paper, we present a material model for PET and its application in computational simulations of a typical balloon blow-forming process under isothermal and non-isothermal conditions. The constitutive model that we have employed is a finite strain thermo-viscoelastic formulation that captures the strain rate, temperature, and strain induced orientation effects typically observed in polyesters. Such simulations can be used to determine the processing window of temperature and strain rates that will yield appropriate balloon compliance and inflation characteristics.
Obtaining Flow Properties Directly from an Extruder
Melt flow properties are useful in selecting an appropriate extruder screw and die, in setting appropriate processing conditions, in troubleshooting extrusion problems, and in allowing prediction of extrusion behavior. Unfortunately, many companies do not have rheometers in house to measure melt flow properties. As a result, information on melt flow properties frequently is not available. This paper will describe some simple techniques that can be used to determine melt flow properties directly from an extruder. It requires running the extruder at several screw speeds and measuring the throughput and melt pressure at each screw speed. This can typically be done in about ten to fifteen minutes either during startup or shutdown. The effective viscosity in the screw channel can be calculated from the amplitude of the pressure fluctuation resulting from screw beat. The power law index can be determined by plotting throughput vs. pressure and fitting the data using a power law expression. Several examples will be given to show how the melt flow properties can be obtained from quick tests on an actual extruder. This allows quantitative determination of the power law parameters: consistency index and power law index. Data obtained from an extruder will be compared to data obtained from a capillary rheometer. It will be shown that there is good agreement between data from the extruder and the capillary rheometer.
Opportunities for Reinforced Plastics in Automotive Applications
This paper presents the motivation for using fiber-reinforced plastics in automotive applications and the advantages and limitations concomitant therewith. Applications of fiber-reinforced plastic components in current and future vehicles have been selected for discussion to provide examples of how these materials can be used to support the drive toward the continuous improvements in performance, energy-efficiency, manufacturing cost, and environmental conservation.
Kinetics of Isothermal Crystallization of Syndiotactic Polypropylene: Avrami, Tobin and Malkin Analyses
Various macrokinetic models; namely the Avrami, Tobin, and Malkin macrokinetic models, were applied to describe the kinetics of isothermal crystallization from the melt state of syndiotactic polypropylene (sPP). Data analysis was carried out using a direct data-fitting method, in which the experimental data were directly fitted to each macrokinetic model using a non-linear multi-variable regression program. The results suggested that the experimental data can be best described by the Avrami model, followed by the Malkin and Tobin models, respectively.
Blends of Ethylene-Styrene Interpolymers
Binary blends of ethylene-styrene interpolymers (ESIs) were studied over a range of styrene concentration. The miscibility composition map was determined primarily from the morphology as imaged with AFM, and when possible confirmed by analysis of the Tg behavior using DMTA and DSC. A difference in styrene content of about 8 wt% marked a transition from miscible to immiscible behavior for amorphous ESIs. The miscibility criterion extended to blends of semicrystalline ESIs. It was also found that molecular weight affects the observed domain morphology.
On-Line Melt Strength Enhancement of Polypropylene for Extrusion Coating
The superior performance of Montell's high melt strength branched polypropylene (bPP) resins has been well documented. Their long chain branched structure gives them high melt elasticity or melt strength, which allows very high line speeds, low neck-in, and thin coatings (high draw ratio) when extrusion coating. A concentrated but highly miscible version of branched PP has been developed which allows for the on-line addition of bPP to any linear polypropylene, including the relatively high-MFR grades used in extrusion coating. This versatile approach allows converters the flexibility to add only the quantity of bPP needed for their processing conditions and to select from a wide variety of linear PP types, depending on the desired properties of the coating. Performance data and rheology at various letdown levels into a variety of polypropylenes, heterophasic copolymers and random copolymer polypropylenes will be discussed.
Branching of LLDPE as Studied by Crystallization-Fractionation and its Effect on Mechanical Properties of Films
Linear low-density polyethylene (LLDPE) has short-chain branches that are incorporated into the polyethylene backbone by random copolymerization with varying amounts of one or more alpha-olefins (1-butene, 1-hexene, 1- octene, etc.). In LLDPE, ethylene is the predominant monomer and alpha-olefins are the comonomers that hinder the crystallization of the ethylene molecule. Thus the presence of alpha-olefin in the main molecule as a branch influences the properties of the copolymer. Diverse properties in films of LLDPE grades with similar MI, density, molecular weight and molecular weight distribution can be attributed to variation in short-chain branching distribution (SCBD), assuming that the type of alpha-olefin branches in the LLDPE grades are the same. Hence measuring the SCBD is of prime importance for predicting the performance of LLDPE. Traditional analysis of branching distribution is by using Temperature Rising Elution Fractionation (TREF) where the LLDPE solution is fractionated by taking advantage of the differing crystallizabilities of the molecules due to variations in chain branching levels. This fractionation is achieved in two full temperature cycles, crystallization and a subsequent elution. In a relatively new method called CRYSTAF (Crystallization Analysis Fractionation), only crystallization of the polymer solution is needed thereby reducing the analysis time considerably . This is the method used in this study to analyze three different solution-based, 1-octene LLDPEs prepared under varying conditions. The three LLDPEs are blown into films and tested for their physical and heat-seal properties.
Extrusion of Closed Cell Very Low Density Flexible Syntactic Foams Using Metallocene Catalyzed Polyolefins and Thermoplastic Microballoons
The purpose of this study was to develop a superior foamed jacketing compound for underwater communications cables. The cable structure and application requires a light weight foamed jacketing material to promote buoyancy while also possessing excellent hydrostatic pressure resistance, abrasion resistance, low compression set, low temperature flexibility, overall toughness, and good surface quality. The project goal was to achieve a foamed cable jacket material with a density no greater than 550kg/m3. The minimum obtainable foam density was to be determined. Cell structure, surface appearance and skin quality were also considered to be important. Small, closed cells and smooth skin were specified as necessary for an acceptable product. Analysis of variance was used to study the effects of screw speed, processing temperatures and microballoon concentration on foam density.
Using Manufacturer's Reps to Sell a Technical Product
Many small and growing firms use a network of manufacturer's reps to sell products. Experience and results using reps vary widely over the plastics industry. Commonly, smaller firms using reps complain that of low value for the money spend, and the reps for such firms counter that principals want results without investment or commitment. This paper examines issues and best practices when using reps to sell a technical product in the plastics industry. A survey was of plastics firms ranging from resin suppliers to small injection molding houses was done via telephone and mail. Results from employers and would-be employers of reps were tabulated and summarized. A similar survey was done of outstanding rep firms in the plastics industry. Answers to the both surveys are condensed with an eye to setting up a short list of do's and don'ts when setting up rep groups.
Effect of Heater Band Orientation on Cavity to Cavity Variations
This paper presents the results of a study that shows that heater band orientation on a machine nozzle can cause an imbalance of over 5% in multi-cavity molds. The amount of imbalance is material dependant. The imbalance is most directly related a material's temperature and viscosity constants.
The Effects of Stress Hardening on the Crystallization and Density of Polypropylene
When polymers undergo stress hardening, their crystallinities and densities are affected. Polypropylene was the material tested in this experiment. It was put under various levels of strain by using a tensile tester. Each sample was pulled to a predetermined strain, allowed to relax for a period of time, and measured for crystallinity using the Differential Scanning Calorimeter (DSC). Stress-hardened and original samples were used to compare the change in crystallinity. The density of each sample was also determined using the Density Gradient Column.
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