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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M. Xanthos, R. Dhavalikar, V. Tan, S.K. Dey, U. Yilmazer, May 2000
PET foams of variable densities, (1 g/cc to 0.2 g/cc), based on virgin and recycled material were produced by extrusion with physical or chemical blowing agents and evaluated as low density core in sandwich panels having M/F impregnated paper or flame retardant mineral reinforced PET as skin faces. Flexural and shear stiffness of the laminates were determined by variable span three point bending. Panels were also tested for thermal and moisture stability and compared with competitive sandwich constructions based on PVC foam, flake board, particleboard and plywood. Potential applications of the PET based laminates in building and construction are presented.
This feasibility study deals with the investigation of welding Polyvinyl Chloride (PVC) sheets of different formulations, using high dielectric frequency technique. The experimental work consisted of PVC formulation (rigid sheet), mold design (new products), experimental design to quantify the effect of process parameters, mechanical characterization (tensile, peel testing) of the weld area, and process optimization. Rigid PVC formulation was selected based on two primary mechanical properties, tear resistance and shear modulus. The weld was well achieved within the studied range of parameters, while the processing conditions were experimentally optimized. Finally, new office items were successfully produced as a result of the design of new molds combined with new process layout (sheets).
A patented Extensional Flow Mixer (EFM) (1) has been developed in which plastics is hydrodynamically mixed by flowing through a series of convergent and divergent regions so that very efficient dispersive and distributive mixing can be achieved. The EFM can be attached to any plastics pumping machine, such as single-screw and twin-screw extruders, for injection molding, blow molding, extrusion, and compounding. Comprehensive laboratory and industrial tests have been conducted especially for film applications, which indicate the mixing of a single-screw extruder (SSE) with an EFM can outperform that of a twin-screw extruder (TSE) in certain aspects. Results of gel elimination, strength enhancement and morphology changes are presented.
The relationship between pressure, volume and temperature (PVT) of polyvinylidene fluoride homopolymers (PVDF) and polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) copolymers was determined in the pressure range of 200 to 1200 bars and in the temperature range of 40°C to 230°C. Differential scanning calorimetry (DSC) analysis was performed on each resin to simulate the cooling process during the PVT experiments and to determine the crystallization and melting temperatures at atmospheric pressures. The TAIT state equation describing the dependence of specific volume on the zero-pressure volume (V0,T), pressure and temperature has been used to predict the specific volume of PVDF and PVDF-HFP copolymers.
Injection molded semi-crystalline thermoplastic parts show variable morphologies across their thickness. Process parameters such as injection speed, mold temperature, and melt temperature, play important role in forming these morphologies. The heat and shear history has great effect on the crystallization process of the semi-crystalline plastics. In this study, different available crystallization models were used to predict the crystallinity distribution, and capabilities of the models compared. Based on the results from these models, a more realistic model, which considers stress relaxation during the crystallization process, is proposed.
Adhesion properties were determined on five-layer coextruded cast films. With a few exceptions, the cap layers consisted of polypropylene, the tie layers consisted of blends of polypropylene and maleic anhydride-grafted polypropylene, and the center layer consisted of various polyamides. Up to a point, the adhesion increased as the overall film thickness and the level of maleic anhydride-grafted polypropylene were increased. The molecular weight of the grafted resin had a small effect on adhesion. Homopolymer diluent outperformed random copolymer diluents. Adhesion did not vary much when different types of polyamides were used as the center layer, but each exhibited much greater adhesion than an ethylene-vinyl alcohol center layer.
Angelika Schmidt, Carmen Alves, Maria Soliman, Wiebren S. Veeman, May 2000
The changes in phase structure under uniaxial deformation of block copolymers of Poly(butylene terephthalate) (PBT) and Poly(tetramethylene oxide) (PTMO) have been investigated using 13C solid state NMR spectroscopy and infrared spectroscopy on in-situ stretched samples. The study was focused on the strain-induced crystallization of the PTMO. It became obvious that a minimum stress level in the material is necessary for the strain-induced PTMO crystals to form and to be stable at room temperature. The amount of crystalline PTMO is dependent on the stress level and on the temperature. We also found, that the PTMO crystallization is favored by a large PTMO block length and a large PTMO content.
Marianna Sarkissova, Maria Soliman, Gabriel Groeninckx, May 2000
In the past decade, numerous novel polymeric products were introduced, including polymer blends, for various applications in the automotive and electronic industry. Up to now a homopolymer as such has to be reinforced to meet the high demands on stiffness and strength in engineering applications and glass fibres were the major reinforcing element used in these materials. Microfibrillar reinforced composites based on polycondensates are new polymeric construction materials with ultimate properties. Such a composite has specific economical and ecological advantages since, upon recycling, a polymer blend is obtained which can be re-used to make again polymeric materials with specific properties.
Jun Gao, Gregory C. Walsh, David Bigio, Robert M. Briber, Mark D. Wetzel, May 2000
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.
Paul Elkouss, David Bigio, Gregory Walsh, Paul Andersen, May 2000
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.
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.
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.
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."
Balakrishna Haridas, Christopher J. Matice, May 2000
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.
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.
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.
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.
Lawrence J. Trainer, Don Beauregard, Steve Orroth, Nick Schott, May 2000
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.
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.
Dean Q. Lewis, Gary A. Gabriele, Bob Brown, May 2000
Consumer product manufacturers continually desire to make their plastic components more inexpensive by such methods as reducing part count, reducing wall thickness, eliminating tools, and reducing assembly time. Integral fasteners, or snap-fits, can be used to achieve some of these goals, but must be carefully incorporated into a product design. Many of these products, especially portable or hand-held electronic items, need to meet rigorous test requirements, including drop testing. Many common attachment designs that use snap-fits can fail under these conditions. This paper covers the investigation of a desktop telephone housing to ensure that snap-fit disengagement did not occur under drop impacts. First, a failure tree analysis of the product was performed to determine likely scenarios for disengagement. Then tests were conducted to determine impact force magnitudes. Drop testing of prototypes was conducted to determine under what conditions disengagement occurred. From these results, design changes were suggested and prototypes constructed to test the suggested changes. The results of this analysis and testing suggest some general design guidelines to make products attached with snap-fits more robust against the conditions found in typical drop tests.
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