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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A Concept for a Applied Dryer Control by Prediction of the Moisture Content of Dried Material
To produce high quality parts from hygroscopic plastic materials like ABS, PA, PC, PET, PUR, etc. it is mandatory to keep the moisture content of the processed material below an upper limit for the specific product. Otherwise, the residual water causes problems during processing and probably decreases product quality. As a result of an increasing pricing pressure on the plastic processing industries the productivity of the manufacturing processes became more significant. One way to increase productivity is to reduce the energy consumption of the process. Drying requires a lot of energy. Process parameters are set after specifications from the producer of the raw material. These parameters are independent from the moisture of the raw material. Consequently, this leads to a higher energy consumption than is necessary and to fluctuations of the residual moisture. There is no closed loop control to keep the residual moisture behind the dryer at a constant level. The main reason is that there is no economic unit available to measure the moisture content that works for all materials independent from colour, apparent density, etc. This work presents a way to keep the level of the residual moisture at a constant level. For that a model of the drying process is used.
Meltdown-Time Profiles of Vibration Welded Nylon 66 Compounds
Meltdown is an important vibration welding process parameter. This research experimentally measured the meltdown-time profiles obtained from nylon 66 parts vibration welded on a Branson Mini II linear vibration welder. The study examined the effect of material (glass reinforced and unreinforced nylon 66), process parameters (weld pressures) and weld geometries (butt, T-shaped and cup welds) on meltdown-time profiles. Experimental meltdown-time profiles compare favorably with theoretical profiles obtained from existing models. Additionally, the presence of moisture in parts, and uneven or excessive welding are detectable by observing meltdown. This suggests its potential as an on-line quality control parameter.
The Influence of Different Processing Parameters on the Properties of Polypropylene for Rotational Moulding
This paper presents an overview of an experimental investigation to determine the influence of various processing parameters on the properties of rotomoulded polypropylene. Polypropylene samples were rotationally moulded under different heating and cooling regimes and under a nitrogen blanket. Mechanical properties were determined and compared to those of injection moulded polypropylene. It is shown that with the correct processing parameters, mouldings with good mechanical properties are achieved. Moulding with a nitrogen blanket combined with fast heating and cooling reduces degradation to acceptable levels.
A New Concept in Coextrusion Dies
Producing coextruded product structures with more layers results in stronger more economic film structures enhancing the polymer's unique properties in combination with the reduction of the unfavorable attributes of some polymers. Coextrusion brings out the best properties of the individual polymers in the film structure. This paper will present the Dual Spiral System (DSS), a new patented concept in coextrusion blown film and blow molding. The DSS enables processors to take advantage of the improvements brought about from adding layers without adding additional equipment costs. By dividing each individual layer into two separate layers, the enhanced structural and physical properties of each layer material can be taken advantage of. This means that a five extruder DSS die would in fact be producing a 10 layer film sheet.
Flow Instabilities of Linear Polyethylenes in Capillary Experiments and Effect of Die Materials
Flow instabilities of linear polyethylenes have been studied in capillary dies. The effects of shear stress, temperature, molecular weight and material of construction of the dies on the critical shear stress for the onset of slip have been evaluated. Flow curves were obtained using dies with constant L/D and different diameters. Slip velocities were calculated using the Mooney technique (1) as a function of shear stress. The onset of slip and slip velocity are affected by the material of construction of the capillary die. Stainless steel and copper alloys were used to determine the effectiveness of a dezincification hypothesis to explain observed slip phenomena.
The Rheological, Mechanical and Thermal Properties of Polypropylene/Polyethylene-Octene Copolymer Blends
Blends of ethylene-octene copolymer (EOC), Engage 8150, with Polypropylene (PP) were prepared using a Killion compounding extruder. The blends studied were in the range 1% - 30% EOC content. Rheological analysis of the various blends showed only slight increases in apparent viscosity with increasing EOC content. Mechanical analysis on injection moulded samples of these blends showed that tensile modulus and flexural modulus decreased and impact properties were improved significantly with increasing EOC content, especially at higher EOC concentrations. Dynamic mechanical thermal analysis (DMTA), and Differential Scanning Calorimetry analysis (DSC) would tend to indicate some degree of polymer miscibility especially at the higher EOC concentrations, with slight decreases in crystallinity and phase transition temperatures being recorded especially for the higher EOC concentrations.
Understanding the Source of Reduced Mechanical Properties in Reinforced Molded Products
The movement to design plastic products with thinner walls has raised many issues for molders. Using a glass-reinforced resin in high-shear applications can decrease the resin's physical and mechanical properties. Understanding where the breakdown occurs in the molding system is fundamental in designing thin-walled plastic products. Changes in glass fiber lengths were measured at various locations in the delivery system to the part, over several material generations. This information was developed in conjunction with the data collection for the long-term wear study of copper alloy mold components. A procedure was developed for prediction, testing and measurement of fiber length in a thin-wall application.
New Product Development: The Effect of Speed and Role of Outsourcing
Inventions and innovation process play critical role in long-term success of industry. New products promote growth and increase profitability - far more than added-on or derivative products. Higher costs, crowded market space, major acquisitions, and globalization in 1990s have forced industries to focus on supporting and sustaining core products and to avert risk involved with new products. This in turn has reduced corporate R&D budgets for developing new products. R & D and product managers are faced with managing new product development efforts with leaner staff and limited resources. Understanding how to stay in the game with limited resources is key. In this article, author reviews key factors for successful new product development process, with emphasis on effect of speed and role of outsourcing R & D early on.
Standard Test Method for Particle Size Analysis of Plastic Materials (Wet Analysis)
Standard test methods (ASTM D1921-96) have proven unreliable in determining percent passing" particle size analysis of plastic pellets on a given sieve size. Statically charged particles make dust collection and quantification difficult. Therefore dry sieve methods are unacceptable for particle sizes below 38 micron. We have developed a reliable method for quantifying a passing of plastic materials on a given particle size allowing for collection and quantification of particles above and below 38 micron. A liquid is used to wash particles through a sieve. The liquid is filtered and the filter papers dried and weighed to determine a passing Parts-Per-Million (PPM)."
Solid Conveying Model for Determining the Throughput for Ultra-Short Single Screw Extruders with Spiral-Groove Cylinder
Dimensioning conventional single screw extruders, axially grooved cylinders are utilised to achieve increased throughput and an operating performance being independent of the counter pressure by increasing the friction of the material on the cylinder wall. In contrast to this, the geometry of the grooves in an ultra-short single screw extruder  with combined conveying and plasticising areas serves to increase material friction and to realise a mass flow. For this reason, the models of the material throughput for conventional single screw extruders are not unconditionally applicable for this extruder type. It is not possible to consider only one volume element in the screw channel for formulating the model. Instead, a combined system of various volume elements that move at different speeds and in different directions must be taken into consideration.
Dynamic Mechanical Analysis of Aromatic Polyamide/Ethylene-Propylene-Diene Terpolymer Laminates
The dynamic mechanical analysis of aromatic polyamide, ethylene- propylene-diene terpolymer (EPDM) and 256-microlayer laminates of aromatic polyamide and ethylene-propylene-diene terpolymer have been investigated at different temperatures. Furthermore, microscopy was used to correlate the thermomechanical observations with the morphology. The aromatic polyamide studied is a random copolymer of isophthalic acid, 12-aminododecanoic acid and bis(4-amino-3- methylcyclohexyl)methane. The 256-microlayer laminates were prepared by using microlayer co-extrusion technology. Increasing compatibility between the aromatic polyamide and EPDM showed minor improvement on the dynamic response for the laminates.
On-Line Viscosity Control for the Injection Molding Process
Variation in material viscosity during production is a well-documented phenomenon. The variation can be caused by regrind usage, humidity level, factory temperature variation, and raw material batch to batch variation. Today's quality control systems react to viscosity changes by maintaining certain parameters of the process constant. These control systems operate without directly effecting the material viscosity, for example trying to maintain a reference peak cavity pressure profile. Direct control of material viscosity by means of melt temperature is one concept being explored. Compensation is required for the effect of temperature changes on density and material solidification times. The paper examines the ability to control part weight and dimensions in a production environment, as part of an on going research programme in the Moldflow laboratories.
Automated Injection Molding Machine Optimization
Injection molding manufacturers are increasing their requirement for consistent and optimised approaches for machine set-up. The ultimate aim of process monitoring and optimization within the manufacturing environment is (i) to develop molds with large processing windows, so there is a high confidence of producing good parts consistently with a higher overall set-up efficiency, or (ii) to achieve 100% automatic inspection and quality control of all molded products, in a straight forward and non-complicated manner. It is a requirement that no unacceptable moldings are passed on to the customer. An automated process monitoring and optimization strategy offers a key opportunity to the polymer processing industry to gain an understanding of its processes, and by this provide greater clarity for the machine operators. This paper presents a case study verifying the automated machine set-up strategy of a new mold in a high-end molding facility, using a computer aided engineering control system.
Extracting Chemical Information from Atomic-Scale Imaging and Spectroscopy
Scanning probe microscopes allow unprecedented views of surfaces. Here, we discuss our efforts to identify and to characterize atoms and molecules on surfaces and how the scanning tunneling microscope images these adsorbates. We are currently attempting to extend the spectroscopic capabilities of scanning probe microscopes in several ways. For example, recent advances in tunable microwave frequency AC scanning tunneling microscopy allow differentiation of some surface features and interrogation of single and bundled molecules. We are also able to map with nanometer resolution the emission of photons induced from nanoparticles induced by tunneling electrons. We are developing these and other local spectroscopic tools to determine the chemical, physical, and electronic properties of surface features and adsorbates while simultaneously measuring their chemical environment.
Nanometer-Scale Structural, Tribological, and Optical Properties of Ultrathin Poly(Diacetylene) Films
The ability to create organized ultrathin films using organic molecules provides systems whose chemical, mechanical, and optical properties can be controlled for specific applications. In particular, polymerization of oriented mono- and multi-layer films containing the diacetylene group has produced a variety of robust, highly oriented, and environmentally responsive films with unique chromatic properties . These two-dimensional poly(diacetylene) (PDA) films, where the conjugation runs parallel to the film surface, have previously been prepared in a variety of forms . Of particular interest is the optical absorption of PDA due to its -conjugated backbone. A wide variety of PDA materials, including bulk crystals, thin films, and solutions, exhibit a chromatic transition involving a significant shift in absorption from low to high energy bands of the visible spectrum, thus the PDA appears to transform from a blue to a red color. In addition, the red form is highly fluorescent, while the blue form is not. This transition can be brought about by temperature [3, 4], binding of specific biological targets , and applied stress (mechanochromism) [6, 7]. In this paper, we discuss the Langmuir deposition of ultrathin PDA films and the subsequent measurement of their structural, optical, and mechanical properties at the nanometer scale. By altering the head group functionality, we can choose between mono- and tri-layer PDA film structures . Measurements with the atomic force microscope (AFM) reveal strongly anisotropic friction properties that are correlated with the orientation of the conjugated polymer backbone orientation . Furthermore, we can use the AFM tip or a near field scanning optical microscope (NSOM) tip to locally convert the PDA from the blue form to the red form via applied stress . This represents the first time that mechanochromism has been observed at the nanometer scale. Dramatic structural changes are associated with this mechanochromic tr
Evaluating the Impact Behavior of Different Thermoplastics and Composites
The objective of this paper is to study the impact properties of different thermoplastics and composites by using different impact methods. The impact properties of Polyethylene (PE), Polypropylene (PP), Polyvinyl Chloride (PVC), Polymethylmethacrylate (PMMA), Acrylonitrile Butadiene Styrene (ABS), Ionomer, and PVC composite were investigated. The difference between uni-axial, bi-axial and tri-axial impact strength of the studied materials was illustrated. Impact load vs. displacement curves highlighted the difference between crystalline and amorphous thermoplastics and composite. In addition, the effect of short glass fibers on the impact properties was also demonstrated.
Screw Cooling Effects in Single Screw Extruders
Screw cooling has been used on occasional single screw extruder applications for many years. Most screws today are set up for cooling (have holes drilled down the screw shaft for some distance), but these days the cooling is seldom utilized. It would be helpful to have a general study of this parameter to prove where possible gains in performance are expected, or to obtain data to support why we should not be cooling the screw in some instances. This paper will give the results of a study of screw performance on several polymers where screw cooling was tested. The results of the non-cooled screw will be compared to screw cooling along the early portion of the screw as well as a fully cooled screw shaft. The tested screw will be one of today's barrier type screws and will allow conclusions as to the performance altering affects of screw cooling. The need to have this information documented in a concise form will be satisfied by this study.
Business Opportunities in the Czech Republic
The Czech Republic, a country with a population of 10 million has a formidable chemical industry with a long tradition. The polymer processing industry is its important part and represents a number of unique technologies. One of the prime candidates for the European Union, expected to be admitted in 2005, it is a stable partner ready to be part of the global economy. With a highly skillful and productive workforce it represents a very good opportunity for trade offering a great variety of unique products. Because of this country's location in the center of Europe, it is an attractive partner for investment. This paper will deal with current trends and provides details about the industry.
The Influence of Rotational Shear Pultrusion on Fiber Concentration and Wet out of Long Glass Polypropylene
New technology was developed to impregnate continuous glass fiber with molten thermoplastic polypropylene for manufacturing long fiber compounds. A composite with a polypropylene matrix and glass fiber reinforcement was made by rotation of a die orifice chamber about an axially directed roving of continuous fiber in the presence of the thermoplastic melt. The rotation reduced the melt viscosity of the polymer by shear thinning, while dragging and directing the polymer into the fiber, thereby wetting and dispersing the fiber. Fiber concentration was strongly influenced by the rotational speed of the die in conjunction with the line speed of the strand. Fiber wet out, measured by the shear strength of the strand, was improved at higher rotational speed and line speed.
The Processing and Performance of Nylon 4.6, Polypropylene Oxide/ Polyamide (PPO/PA) and Polyetherimide (PEI) in Automotive Fuel Handling Applications
This present work investigates the rheological properties and the effect of immersion in standard automotive fluids (an extension of SAE J2027) on the mechanical performance of a range of Nylons, Polypropylene Oxide/Polyamide (PPO/PA), and Polyetherimide (PEI). The rheological characteristics of Nylon 4.6., PPO/PA and PEI were investigated and the results showed significant decrease in shear viscosity at dwell times in excess of three minutes for Nylon 4.6. and PPO/PA. Injection moulded samples of the Nylon 4.6., impact modified Nylon 4.6., Nylon 12, PPO/PA and PEI were immersed in the standard automotive test fluids, Fuel C, zinc chloride solution and aggressive water. Subsequent mechanical analysis of the various specimens showed only slight decrease in the tensile modulus of the Nylon 4.6. after immersion in Fuel C, however significant weight gain and deterioration in tensile modulus were recorded after immersion in aggressive water. Dynamic Mechanical Thermal Analysis on the Nylon 4.6 showed only slight decrease in storage modulus (Log E') and Tg, after immersion in Fuel C. However a significant decrease in Tg by up to 80°C was recorded for samples immersed in aggressive water.
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