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 TriSEC and 3dTREF Approach to Polymer Blend Design
Polyolefin technology has made remarkable progress in the last four decades. The market is expanding and the technical challenges today remain high. New products are being developed with new catalysts or by the blending processes. New resins are needed to meet the requirements of high-speed fabrication machines, and market expansions into high-tech applications. A successful resin development either by blending or by optimizing catalyst and reactor condition requires a strong polymer characterization support in determining the polymer microstructures. To this end, we have made considerable upgrade of our polymer characterization capabilities using GPC and TREF. Our approaches are the following. First, we have focused on obtaining the best precision we could out of these techniques. We then added the triple detector capabilities to the systems and take a hybrid approach of analyzing the polymer microstructure results. We generated a polymer microstructure plot" that contains both the triple detector GPC and TREF results in one chart. We find the results presented this way are very effective in comparing products or defining blending conditions for resin design."
The Case against Oxidation as a Primary Factor for Bonding Acid Copolymers to Foil
Oxidation is often used in the extrusion-coating industry to enhance the adhesion of LDPE to polar substrates such as aluminum foil. Previous investigators have suggested that oxidation plays a key role in the adhesion of acid copolymers to foil; the most direct evidence for this is the observed increase in peel strength with increasing time in the air gap (TIAG). The results of new experiments, however, suggest that oxidation may not be responsible for this behavior. Acid copolymers that have been ozone treated, loaded with antioxidants or processed at temperatures well below the expected onset of oxidation still show the characteristic increase in adhesion with increasing TIAG. Measurement of peel strength in the MD and TD show that the TD peel strength is not influenced by TIAG and peel strength correlates with % elongation of the coating. This suggests that stress and orientation may play a role in the observed behavior. A practical implication of this work is that acid copolymers will generally adhere more strongly to foil than LDPE, even when the acid copolymer is processed at lower temperatures. This reduces the potential for taste/odor, processing and other problems associated with high-temperature processing.
A New mLLDPE for Extrusion Coating Applications
Metallocene polyethylenes are well known for providing superior toughness, heat sealing, and clarity versus conventional polyethylenes. Their unique attributes have been employed for almost a decade in the manufacture of many different high-performance blown and cast films for numerous end-use applications. Lower density metallocene plastomers have also found use in specialty extrusion-coated and laminated structures where good puncture and tear resistance along with excellent hot tack and heat sealing performance are required. An extrusion coating study has shown that a similar set of attributes can be obtained using a new mLLDPE. For the best extrusion coating performance, the mLLDPE should be blended with small amounts of LDPE.
Joining of Thermoplastics with Friction Stir Welding
Friction stir welding is a process that is used for joining aluminum and its alloys. It requires only relatively simple tooling, and is extremely safe. There are no arcs, fumes, or other emissions. Early attempts to use the process for joining plastics were unsuccessful, but newly developed tooling has made it possible to weld many thermoplastic materials using a modified FSW process. This paper reports the tooling and operating parameters used to join a variety of materials, as well as the strengths of the resulting joints. Weld properties in ABS, PP, and HDPE exceeded 90% of the base material strength using the new tooling developed.
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.
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