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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Visual Color Evaluations: Problems and Solutions
In this era of high-powered computers and spectrophotometers, the human eye-brain combination of a trained observer is still commonly used as a tool to evaluate color differences. This paper is written in hopes of pointing out some of the potential areas for problems with visual observation, and how these can be overcome to allow this wonderful tool to be used effectively. To start with the basics, there are three things necessary to have color-a light source, an object, and an observer. If you remove any of these, color no longer exists. What is equally true but perhaps less obvious is that if you change one of them, the color changes. Change the object, and the color changes-this is quite evident. Change the light source and the color changes-perhaps less evident, but still true. What is the least evident is that if the observer changes, the color changes. This is due to the nature of the way the eye works.
Development of a Continuous Thermal Separation System for the Removal of PVC Contamination in Post-Consumer PET Flake
Differences in thermal properties of plastics such as their softening and melting points can be exploited to separate mixed post-consumer plastic flake. This form of separation can be most effective if differences in melting or softening points of the two plastics are large. For example polyvinyl chloride (PVC) and polyethylene terepthalate (PET) differ in their softening points by ~ 60°C, (i.e. PVC becomes tacky at 200°C and PET at 260°C. This article examines the development of a rotary thermal separating system for the removal of PVC flake from a stream of post-consumer PET flake.
Advances to Dynamic Mechanical Analysis
Dynamic Mechanical Analysis (DMA) is growing technique for characterizing the modulus and mechanical damping of materials as function of temperature. The technique as it exists today is most important for measurement of the glass transition and sub-glass transitions, the latter of which gives insight into molecular structure. However the technique has not gained wide acceptance among design engineers because the calculated modulus values can only be verified over a limited range. A new instrument that uses a new measurement paradigm is presented. The new measurement system uses a simpler model for converting instrument signals to modulus values for more reliable results. Due to the enhanced measurement system, the range of measurements is also greatly extended. The new instrument uses single differential thermal analysis to provide a means for direct measurement of the specimen temperature through a thermal device in contact with the clamps. SDTA also provides the means to calibrate temperatures using primary melting point materials.
Influence of the San Content in the ABS Terpolymer Toughness and Phase Morphology
Currently toughening mechanisms are relatively well known for rubber toughened plastics. However, brittle polymer toughening by mechanical blending with another toughened plastic still need some understanding. The present work correlates morphology and physical properties for high rubber content ABS and its blends with SAN copolymer. The results indicated a close relationship between interparticle distance and fracture toughness for the blends. An non-inverted phase morphology of the ABS explains deviations in mechanical properties as compared to a conventional ABS.
Influence of Interphase Characteristics on Mechanical Properties of Polypropylene/Glass Fiber Composites with PP-g-MAH Interfacial Compatibilizer
The mechanical properties of glass fiber-reinforced polypropylene are strongly influenced by the type and degree of interfacial interactions attained, depending on the efficiency of the coupling agent used in the composite. In order to modify the fiber-polymer interfacial interactions, composites of PP with aminosilane-treated GF were prepared using PP-g-MAH as interfacial compatibilizer. The superior tensile and impact properties obtained in these composites can be attributed to improved fiber-polymer adhesion achieved by a thicker and more deformable interphase formed with PP-g-MAH concentration.
Determination of the Kinetics Crystallization Constant in a Heterophasic Polypropylene Using the Master Curve Approach
The purpose of the present work was to test the validity of the Master Curve Approach to determine the nonisothermal crystallization rate constant for a heterophasic polypropylene. Nonisothermal crystallization experiments were carried out in a DSC at several cooling rates, being the original curves corrected for the temperature lag between the sample and the furnace. The relative crystallinity as a function of temperature were simulated using the Nakamura equation and the determined kinetic constant. A relatively good agreement with the experimental curves was obtained.
Powerful Gearboxes for Plastics Extrusion Especially in the US Market - A Market Study
In the manufacturing process of plastic, extruders are commonly utilized. In addition to the relatively simple built single screw extruders, twin-screw extruders with co- or counter-rotating screws are used. The drive unit (motor and gearbox) it is the most important unit besides the screws and the barrel of the extruder, and is essentially influencing product quality and product output. During the last years the possible plastics output of these machines increased strongly. In a similar way, the demands towards the screws and cylinders increased as well as towards the gearboxes with regard to power, respectively torque / speed and output. To design such high-torque and/or high-speed drive units in an economic way, extraordinary experience and the use of the up-to-date results from research is required from the manufacturer of gearboxes. One further main demand on the gear is to achieve similar torsion stiffness of the two output shafts in order to hold the difference in torsion angle between the screws small. Differing rotation angles would lead to modifications in the screw gap, which directly influences the product quality. In the following, technical solutions for high-torque and high-speed gearboxes are explained and compared. For this they are put on a common technical basis.
Commercialization of Microcellular Blow Molding
Microcellular processing techniques have been applied at a commercial level to both extrusion and injection molding plastics processing, using the patented and proprietary development of Trexel, Inc. The results have been quite successful. In extrusion, the MuCell® microcellular process has allowed the reduction of weight of typical extrusion products by up to 25%, and increases in productivity, while maintaining excellent physical properties. In injection molding, the same basic processing techniques have provided molders with the ability to produce parts with reduced warpage, greater dimensional accuracy, at lower molding pressures and at faster cycle times. All this combined with weight reduction in these parts.
Film Finishing Part I: Commercial and Emerging Thermoplastic Film Based Technologies
The Automotive Finishing Industry, valued at $2.3 billion in North America1, is faced with serious challenges to reduce cost and a growing urgency to meet environmental pressures. The industry is making major progress to reduce emissions but more must be done as requirements are tightened. Concurrently, other technologies are being advanced that may radically change the finishing process in the long term. Finishing plastic parts with film is one of the emerging technologies. Film finishing presents an opportunity for the Plastics Industry to step forward with an all-plastic solution - plastic film finishes on reduced weight plastic body panels.
An Advanced High Modulus (HMG) Short Glass-Fiber Reinforced Nylon 6: Part II - Mechanical Performance
Resent developments were oriented on two high-flow, high-modulus grades fiber-glass reinforced nylon 6 (HMG series) grades for automotive and other industrial applications requiring high stiffness and high strength. These materials combined the following improved technological (injection molding, vibration welding, etc.) and mechanical performance properties such as greater dimensional stability, higher short-term (strength and stiffness) and long-term (fatigue and creep). The current and possible applications of these plastics includes auto mirror housing brackets, clutch pedals, clutch master cylinders, ski bindings, steering wheels, levers, auto seat frames, door handles and door lock mechanisms. In Part I of this paper, we presented results on the role and kinetic of reinforcement with the influence of level of loading and geometrical parameters of used fiber-glass. In Part II of this paper, we are presenting results on short-term and long-term mechanical performance of developed high modulus reinforced plastics.
Improving Cycle Time in Polypropylene Molds
An attempt to reduce the injection molding cycle time of ethylene-propylene copolymer (EPP) molded pieces was performed by means of a change in the crystallization behavior of this material. A sorbitol-based third generation nucleating agent was employed to increase the nucleation sites for crystallization. The thermal and mechanical properties of the blends EPP/sorbitol were evaluated. Cooling time of injection molding was reduced and the appearance of the molded articles checked. It was found that when sorbitol is added to EPP, the crystallization temperature increases in about 6 C for a sorbitol concentration of 600 ppm. The tensile properties of the blends do not showed remarkable differences when compared to the pure EPP. A reduction in the warpage was obtained when the EPP/sorbitol blend was employed; the cooling time could be reduced and the quality of the molded articles does not decrease significantly.
Nanocomposite Polymer Film Technology
Polymer-silicate layered nanocomposites (PSLNs), which exhibit enhanced barrier properties such as increased oxygen permeability, are being explored for use in food packaging applications. End-users want to determine if clay additives would be an inexpensive way to enhance the barrier properties of their products. Experiments were conducted on Nylon-6/montmorillonite clay nanocomposite films to characterize structure and determine properties. Permeability tests were conducted to measure the effect of clay loading on permeability. Electron microscopy was used to view images of dispersion and orientation at and below the nanometer scale. Mathematical models were applied to describe the minimum flow line of oxygen through the film and predict the average diffusivity coefficient. A Java-language computer program was developed to visually analyze particle stacking and diffusion paths by creating 3D images from particle size and spacing specifications.
Nano-Effect in In-Situ Nylon-6 Nanocomposites
12-Aminododecanoic acid modified montmorillonite (ADA-MONT) has been incorporated in nylon 6 nanocomposites by in situ polymerization. Mechanical and barrier performance properties were evaluated for nanocomposites containing up to 8 wt.% ADA-MONT. The high aspect ratio of montmorillonite and the interaction between polymer chains and dispersed silicate nanolayers creates a 110% increase in flexural and tensile moduli, and a 175% increase in heat distortion temperature under load. In addition, smooth, transparent films were successfully cast using standard techniques and equipment. These films were tested for gas permeation at 65% relative humidity. Oxygen transmission rates (OTR) improve as ADA-MONT addition levels increase. At the 8 wt.% addition level, OTR reduction is ~ 80%.
Forward to Better Understanding of Optical Characterization and Development of Colored Polyamides for the Infra-Red/Laser Welding: Part II - Family of Colored Polyamides
Recent developments were oriented towards optical characterization (laser transmission, absorption, etc.) at a wide range of the infrared wavelengths and optimized mechanical performance of polyamides (PA) for the infrared/laser through-transmission welding technology (TTLW). The influence of coloring technology and type of pigments being used was also analyzed. During this study recommendations were developed for optimizing the non carbon black pigment loading in various non-reinforced and fiberglass reinforced PA 6 grades. Additionally we will discuss the efficiency of an advanced method of J-color technology (structural methods of coloring effects) for TTLW of the colored PA based plastic.
Optimized Mechanical Performance of Welded and Molded Butt Joints: Part II - Weld and Knit Lines Integrity
Recent developments were oriented on the analysis of the mechanical performance at local (knit lines and welds) and bulk (molded part) areas, with the influence of molding and welding conditions. It has been found that for non-reinforced and reinforced nylon, the mechanical performance in the knit planes and welded areas are approximately equal to the mechanical performance of a base resin (matrix). The observations on similarities and differences in the formation of knit and weld lines are presented in Part I of this paper. Analysis of mechanical performance at weld at knit lines of various nylons discussed in Part II.
Adhesion between PP-Based Elastomer and PVDF in Layered Structures by Interleafing a Grafted Copolymer
The build up of interfacial adhesion between incompatible polypropylene (PP) based thermoplastic elastomer and polyvinylidenefluoride (PVDF) in layered structures is investigated. To achieve this purpose, a compatibilizer containing PP and polmethylmethacrylate (PMMA) sequences is incorporated as a thin interleaf. The adhesive compatibilizer is obtained from two types of precursors, a poly(propylene-g-maleic anhydride) (PP-MAH) and a poly(methylmethacrylate-co- hydroxyethylmethacrylate) (MMA-HEMA), and results from the reaction between anhydride and alcohol mutually reactive functions. The conversion of this reaction was determined by a FT-IR spectroscopy method by measuring the amount of remaining alcohol functions. The efficiency of the compatibilizer is characterised by U-Peel tests. The fracture energy obtained, which is limited to 60 J/m2 without compatibilizer, varies approximately from 300 to 2000 J/m2, depending on the type of compatibilizer used. The tests have also showed that an increase of the (MMA-HEMA) precursor molecular weight improves the efficiency of the compatibilizer. Moreover, it seems that the crosslinking level in the compatibilizer influences its capacity to enhance the adhesion of PP with PVDF: the higher the crosslinking, the lower the compatibilizer efficiency.
Increased Vinyl Surface Energy through Plasticizer Choice
Printing on flexible PVC can be a problem due to the low surface energy of the vinyl compound. Many of the additives commonly used in vinyl will lower the relatively high surface energy of PVC. The increasing use of water based inks has increased the demand for higher surface energy flexible vinyl compounds. Velsicol Chemical has developed two new polymeric plasticizers that are capable of increasing the surface energy of flexible vinyl film and sheet by as much as 4 dynes/cm. The two plasticizers offer the same surface energy improvement in a high molecular weight-high permanence version and a lower viscosity easier handling version. The improvement offered by the new plasticizers can be reduced or eliminated by the improper choice of lubricant. This study shows that the choice of one compounding ingredient, the plasticizer, can increase the surface energy of a flexible PVC film by up to 4 dynes/cm. In addition it demonstrates the negative impact of a commonly used lubricant on printability. As a lubricant, stearic acid is a very common additive but studies have shown that it can also be generated in the vinyl product from some thermal stabilizers commonly used in vinyl (1).
Machine Innovation and Elementary Steps
The systematic scientific analysis of polymer processing machines leads to the definition of a small number of elementary steps, which in chemical engineering terminology are the 'unit operations' of these machines that transcend individual machine configuration and reflect the common experience of the processed material in any type of machine. The elementary steps reveal the detailed specific physical mechanisms that take place in these machines. These mechanisms, in turn, are powerful tools that when properly used can trigger machine innovation. Moreover, with proper abstraction they can also lead to a formal methodology for invention of new machine configurations. In this paper both processes of innovation and invention will be described through a few selected case studies.
The Carbon Dioxide Technology Platform
What if the electronics industry used specially designed photoresists that could be deposited using a spin coating process based upon liquid CO2 instead of organic solvents? Also what if this industry didn’t have to use hundreds of millions of gallons of water per day to remove sub-micron particles during the manufacture of integrated circuits and flat panel displays? Imagine polymerizing monomers in a continuous stirred tank reactor with the resulting polymers instantly dry, avoiding the trillions of BTUs needed every year to dry commercial polymers made in aqueous reaction media. Imagine an automotive industry that doesn’t expose its employees to toxic chlorinated solvents during metal degreasing processes. Imagine a textile industry that doesn’t need to use 100 lbs of water for every 1 lb of yarn that was dyed. Imagine local dry cleaners that don’t need to clean garments in perchloroethylene and local businesses that don’t need to pay exorbitant, newly enacted taxes on solvent use or carry newly mandated liability insurance policies. What if the demands on municipal water systems and municipal waste water systems could be dramatically reduced by changes in manufacturing technology? Imagine an educational environment where students become grounded in the fundamentals of their core disciplines, are exposed to cutting-edge, multidisciplinary science, and can experience the satisfaction and excitement that comes from doing research that makes a difference to society. The discussion will focus on the latest developments from the NSF Science & Technology Center for Environmentally Responsible Solvents and Processes. In particular, the detailed synthesis and CO2 solution properties of fluorinated and siloxanebased homopolymers and block copolymers will be discussed. The utility of such macromolecules will also be demonstrated for use in coatings (photoresists and textiles), separations, stabilizers for polymerizations, and scaffolds for catalysis. Particular attention w
Analysis of the Failure of a Polyethylene Natural Gas Service Line
Leaking natural gas from a 23 year old polyethylene pipe service line migrated into the basement of a public building. The explosion which occurred upon ignition of the gas destroyed the building and killed six of the seven occupants. Fracture of the line was found to have occurred at the connection of the polyethylene pipe to a service tap on a steel gas main. The critical issue of this investigation was understanding whether the pipe resin had acceptable creep rupture strength for the application and was over stressed or had inadequate long term strength to resist typical stresses to which buried polyethylene gas lines are exposed. This presentation will examine some of the considerations involved in arriving at a conclusion as to which condition existed in this incident.
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