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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Effect of Water Sorption on Mechanical Properties of Fiber Reinforced Dental Resin
Composites from different glass fibers reinforced in dimethacrylate based dental resins were prepared for flexural tests in accordance with ISO 10477. Tests were conducted on both dry specimens and on specimens stored in water for 7 days at 37°C. Depending on type and amount of fibers, the strengths were found to decrease from moderate to minor. Loss of strengths correlated with the constituents of fibers.
Wasteless Distribution Medium: A New Development for the Resin Infusion Process
The typical resin infusion processes like SCRIMP (Seemann Composite Resin Infusion Molding Process) require the use of a distribution medium or system to increase the impregnation speed in large parts. Normally, a substantial amount of surplus resin remains in the distribution medium and has to be disposed with the medium or remains on the part as resin rich domains. A new patented type of resin infusion process is presented, which does not produce any surplus resin waste.
Welding of Polymers Using a Diode Laser
Welding polymers by using a diode laser is a fairly new joining method. The first industrial application is the joining of automotive keys. The process advantages are precisely defined heated zones, minimized melt flow and the realization of three dimensional weld lines. At the IKV a process analysis has been done and the influence of pigments on the weld strength has been investigated. It is possible to weld glass fibre reinforced polyamide, which is transparent for the laser beam, but appears black to the human eye.
Non-Isothermal, Non-Newtonian Analysis of Three Dimensional RTM/VARTM Processes Using HP-Adaptive Finite Element Method
A numerical analysis of the RTM/VARTM processes using an hp-adaptive finite element method is presented in this paper. The constitutive behavior of the resin is modeled using the Carreau-Yasuda 5-parameter model with the WLF and the Arrhenius functions for describing the temperature dependence of the viscosity. In addition, the viscosity can also be read in as a tabular function of the effective shear rate and the temperature. The RTM process is modeled as a three-dimensional, two-phase flow of resin and air (weakly compressible fluid) using a modified Darcy's model. Examples demonstrating the role of SUPG smoothing, viscosity variation, vacuum conditions, and dynamic adaptivity are presented in this work.
Mechanochemical Alteration of Ethylene Copolymers via Solid-State Shear Pulverization (S3P)
Solid-State Shear Pulverization (S3P) is a novel process that uses mechanical energy to cause mechanochemical alteration of some of the polymer chains. The process pulverizes polymers and results in fine powders. Fragmentation events involve a limited amount of chain cleavage depending upon the levels of mechanical strain developed and the molecular weight distribution of the materials. Several virgin ethylene homo- and copolymers were used in this study. It is seen that S3P can alter the flow properties but leaves molecular weight distributions and the thermal properties of these polymers unchanged.
Investigation of the Mechanisms by Which Glass Fibers Disperse in a Polystyrene Matrix
Effective dispersion of chopped glass fibers into thermoplastic matrices is critical for achieving optimum properties. In an effort to further understand the mechanisms by which dispersion occurs, model experiments are conducted using 4 mm long chopped glass fiber bundles embedded in polystyrene. The effects of the process variables of temperature and shear rate upon the onset and mechanism of dispersion are investigated with optical microscopy. Two distinct breakup mechanisms can be identified: rupture and erosion. Rupture results in clusters of fibers separating from the bundle. Erosion occurs when single fibers are removed from a bundle's edge. The onset of dispersion in both simple shear and squeezing flow experiments is a stochastic process.
Ethylene/?-Olefin Elastomer Based Compositions for Automotive Interior Applications
Ethylene/alpha-olefin copolymer elastomers based on single site constrained geometry catalysts exhibit a number of physical properties that make them extremely useful for automotive interior applications. Due to the low level of unsaturation in these polymers, they exhibit outstanding heat and UV aging resistance. Their molecular structures enable these polymers to exhibit low glass transition temperatures (Tg). Thus, compositions containing these polymers exhibit very good low temperature impact properties. Furthermore, these products impart inherent flexibility and soft touch to compositions and eliminate the need for plasticizers. Ethylene/1-octene copolymers exhibit an optimum combination of ultimate tensile and low temperature properties. Ethylene/1-octene copolymers can be compounded to produce flexible TPO compositions with elevated temperature and desirable softness suitable for automotive interior applications.
Utilisation of Fly Ash as a Filler in Plastics
Fly ash is a by-product of the ground coal burning process used in power generation plants. Since fly ash primarily consists of inorganic materials, it is a potential filler substitute for conventional fillers in the plastic industry. In this work, the mechanical, physical, and thermal properties of fly ash filled polypropylene were determined and the effect of adding fly ash on the properties of the resin was studied. Driven by the economical potential and environmental aspect of the usage of fly ash, this study enabled us to determine the viability of coal fly ash to be used as a substitute filler in plastic resins.
Biologically Derived Conducting Plastics
A new biological strategy has been developed to synthesize water-soluble conducting polyaniline. In this approach, anilines are polymerized by the enzyme horse-radish peroxidase (HRP) catalysis in aqueous buffer solution at pH 4.3 in the presence of a template. Strong acid polyelectrolytes such as polystyrene sulfonate (SPS) and the aqueous micelles formed by strong acid surfactants such as dodecylbenzenesulfonic acid (SDBS) are favor-able templates to form nano-scale reactors for the growth of conducting polyaniline. The properties of this enzymatically synthesized polyaniline are consistent with the polyaniline that is traditionally prepared via either chemical or electrochemical procedures. This biological approach offers unsurpassed ease of synthesis, processability, stability (electrical and chemical), and environmental compatibility.
Elastomer Matrix Composites for Impact-Resistant Parts
The impact resistance and energy absorption capacity of most thermoset matrix composites is rather low. Use of elastomer matrix can improve the impact behavior, allowing the design of impact-resistant parts (e.g. crash elements). By using low-viscosity elastomer systems, composite parts can be produced on a commercial filament winding machine. Mechanical tests of filament wound samples show that elastomer matrix composites exhibit superior energy absorption behavior and offer a high optimization potential for impact-loaded composite parts.
Characterization of Multi-Layer Permeation Barriers Made by Microwave Plasma Polymerization
Plasma polymerization is a suitable process to deposit high quality permeation barrier coatings on plastics substrates. The process allows to stack several layers forming multi-layer coatings. In these studies, the permeation properties of single- and multi-layer coatings made by plasma polymerization are investigated. As a result, the oxygen transmission through multi-layers does not only depend on the structures of the single layers. Also, the arrangement of the layers shows great effect on the permeation properties.
Development of a Reactive Extrusion Process for the Production of Plasticized Film Grade Polylactic Acid
The development of a reactive compounding process to provide an economical route for the production of film grade polylactic acid is discussed. The development of this process required the synchronization of a large number of unit operations. The unit operations were combined in a manner to optimize throughput and devolatilization, while minimizing gel formations and blocking. Free radical branching, plasticization, devolatilization, underwater pelletization and surface treatment techniques were employed during the development process. Process development was accomplished on a co-rotating, intermeshing twin screw extruder equipped with both devolatilization and underwater pelletizing systems.
Product Fabrication Project/Course
Polymer engineering courses are now being taught in a variety of departments of numerous engineering schools all over the world. In many cases, a single introductory course is offered, sometimes shared by departments. A practically-oriented project, designed to alert the students to the strong interdisciplinary nature of the field and to prepare them for the type of work that many engineers do in this field, will be discussed in the light of over thirty years of experience in our school. The project can be integrated in an introductory polymer engineering course or, in an expanded form, made into a complementary course. The presentation will include the general objectives, as well as many practical considerations which are important to the success of such project or course.
Novel In-Line Rheometer for Polymer Melts, Compounds and Solutions
A rugged new process rheometer employs a cam rotating in a cylindrical cavity containing a flush mounted pressure transducer. The cam generates excess hydrodynamic pressure in the wedge-shaped region between its outer edge and the cavity wall. As the cam passes the transducer, the measured pressure increases, reaches a maximum and then decreases. The amplitudes of the pressure fluctuations are proportional to viscosity. The shear rate of the viscosity measurement is the cam speed divided by the gap distance. The instrument continuously records and analyzes pressure versus time profiles. For dual shear rate measurements, two cams are keyed to an extruder screw or the shaft of a gear pump. For continuous shear rate sweeps, external variable speed drive motors can be used with side stream and reactor vessel versions. In-line and referee lab data are presented for typical polymers and rheometer configurations.
A Novel Technique for the Detection of a Hindered Amine Light Stabilizer (HALS), Based on Silicon Technology
Polyolefins such as polypropylenes need to be stabilized effectively against UV radiation in order to have a useful product life. The use of hindered amine light stabilizers (HALS) in polypropylene fibers and molded articles has been gaining popularity. Specific applications include automotive bumpers, medical devices and polypropylene fibers for carpets. A novel method was developed to detect the presence of a hindered amine light stabilizer (HALS), based on silicon technology in polypropylene. The method consists of extracting the HALS from the polypropylene matrix followed by detection and quantification using proton NMR spectroscopy.
Design and Analysis of Crosshead Annular Die for Braided Medical Tubing Extrusion
A theoretical method is proposed for optimum design of a crosshead annular die used for medical tubing. According to this method, the geometric variables are determined to minimize the change in gapwisely-averaged flow velocities due to the variation in flow patterns inside the transitional region of the flow channel of the die, namely the gum space. To achieve this, a numerical approach to flow analysis is put forward based upon the simplified motion and energy equations as well as the approximation of the flow channel using a series of varying annular slits, each having constant geometric parameters. Accordingly, the numerical schemes for flow analysis and design optimization are established, and the computer program is developed using Microsoft Visual C++ 6.0. For an optimum die design, the heat adhesion between the cold-fed inner tube and the hot melt during the over-extrusion is evaluated based upon the temperature rise and pressure profile of the melt in the die land. Based upon the optimum die design obtained from the method, the flow is well balanced with enhancement of extrusion quality. Also, it is found that the optimum die designs are less sensitive to extrusion conditions within a certain range.
Recycling PVB Automotive Windshield Interlayer
PVB (polyvinyl butyral) windshield interlayer retains physical properties very well, owing to being effectively packaged in glass prior to recycling. However, the cost of removing all of the contaminant has precluded PVB's acceptance in many applications where it might, otherwise, have been usefully recycled. We have found that finely pulverizing the scrap, with its attendant residues, allows melt-process manufacture of products meeting automotive requirements for vibration damping, tensile strength, tear resistance, and flexibility, over a wide range of temperatures.
Adding Value to Rotational Moldings with Color and Special Effects
This paper reviews the different ways of adding color in rotational molding and provides technical and economic arguments for each method. The effects of pigment incorporation on base material properties are discussed and the importance of factors such as pigment type, pigment loading and method of mixing are examined in relation to material processing, physical properties and the aesthetics of the final rotomolded part. The use of special effects such as stone and antique look colors to give further value enhancement is discussed.
Some Reasons Not to Use Multi-Cavity (>4) Tools
Injection molding continues to be the preferred plastic process for making large quantities of plastic parts. The goal is to make identical parts. When parts are not identical problems develop, not just in performance but also in assembly. The trend toward more complex parts, coupled with demanding tolerances continues to challenge processors in pursuit of the goal of identical parts. Reasons against the trend for high cavitation molds are proposed.
Supercritical Carbon Dioxide Assisted Polymer Blending in Twin-Screw Extrusion: Relations between Morphology Evolution and Mechanical Properties
Supercritical carbon dioxide (scCO2) was added during compounding of polystyrene and poly(methyl methacrylate) (PMMA) and the resulting morphology development was observed. The compounding took place in a twin screw extruder. Viscosity reduction of PMMA and polystyrene were measured using a slit die rheometer attached to the twin screw extruder. Carbon dioxide was added at 0.5, 1.0, 2.0 and 3.0 wt.% based on polymer melt flow rates. A viscosity reduction of up to 80% was seen with PMMA and up to 70% with polystyrene. A sharp decrease in the size of the minor (dispersed) phase was observed near the injection point of CO2. However, further compounding led to coalescence of the dispersed phase. De-mixing of the dispersed phase occurred upon CO2 venting. The resulting morphology was similar to that without the addition of CO2. Adding small amounts of fillers (e.g. carbon black, calcium carbonate, or nano-clay particles) tended to slow down the de-mixing of the polymer blend system when the CO2 was released. The comparison of morphology and mechanical properties for various polymer blends with and without CO2 considerations will be reported.
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