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 Study on the Crystallization Behavior and Morphology of PP/EPR Blends
The morphology and crystallization behavior of polypropylene/ethylene-propylene rubber blends were studied in this paper. The crystallization effect of the addition of EPR in PP was discussed via observation using a polarized optical microscope. The result shown that, with the addition of EPR in PP, the rate of crystallization became slower, the Maltese cross formation gradually disappeared and bead dispersion became evident. Through wide-angle X-ray diffraction analysis, with the addition of EPR in PP, the crystal size was smaller, and differential scanning calorimeter analysis showed that the melting point moved to a lower temperature. This paper also discuss the effect of different take-off temperatures on crystallization for different ratios of PP/EPR in the PP/EPR blend in the flat-film extrusion process. It was found that the crystallization degree and crystalline lamella size were greater at higher take-off temperatures than those at lower take-off temperatures.
Enhancing Mixing Performance of Extrusion Process via Vibration Force Field
Effects of vibration force field on dispersive mixing have been investigated during extrusion of a calcium carbonate filled LDPE system using a split barrel electromagnetic dynamic extruder, which introduce vibration force field into the whole extrusion process. The samples are collected along the length of the screw by barrel opening experiments and subsequently examined by means of scanning electron microscopy (SEM). The quantitative image analyses of SEM micrographs show that the introduction of vibration force field improves dispersion of calcium carbonate in LDPE matrix. With the same vibration amplitude, a higher vibration frequency leads to a smaller average particle size and a narrower particle distribution.
Thermal and Mechanical Properties of Recycled PET and its Blends
This paper discusses the thermal and mechanical properties of virgin PET, recycled PET and their blends. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the thermal properties. The tensile tests at ambient and elevated temperature were used to study the mechanical properties. There were significant differences in the recrystallization behaviour as far as the thermal properties were concerned. In the case of mechanical properties, the tensile test at elevated temperature showed that the strength of the blends of recycled PET/virgin PET were lower than those ones of virgin PET.
True 3D CAE Visualization of Filling Imbalance in Geometry-Balanced Runners
The filling imbalance in geometrically balanced runner system of multi-cavities is always difficult to handle in injection molding. Previous researchers revealed that the flow imbalance problem is related to the three-dimensional thermal history and shear rate distribution of melt flow in the runner, and accordingly proposed a novel apparatus to overturn the melt to avoid this problem. However, the design parameter of this apparatus is different to realize, and it is only performed by trial-and-error. In this paper, we have proposed a new methodology to analyze this injection process. Firstly, a flexible meshing methodology comprising different element topologies is proposed to provide high-resolution mesh for the runner system and cavity. Further, to demonstrate and verify our idea, the comparison between simulation and experiments has been performed. From the numerical experiments, we have proven that the proposed methodology is a highly valuable tool to help understand and further optimize the melt flipping apparatus.
Development of PP/Clay Nanocomposite using scCO2 in Twin Screw Extruder
In this study, as a continuous processing method for the fabrication of polypropylene/clay nanocomposite, supercritical carbon dioxide (scCO2) was introduced in twin screw extrusion process. Supercritical CO2 was used for the purpose of improving dispersion of clay layers in PP matrix and diffusion of polymer chains into silicate layers. PP/clay nanocomposite was produced by two step extrusion processes. In first step, CO2 was injected into the barrel of extruder by CO2 metered injection system and the foamed extrudate was pelletized after solidification in water bath. In second step, CO2 in the foamed product was vented by vacuum pump. Finally, PP/clay nanocomposite without CO2 was produced. In this study, for the development of nanocomposite, the investigations were made for various cases such as variations in CO2 concentrations, maleic anhydride grafted polypropylene (PP-g-MA) concentrations and processing conditions. To confirm scCO2 effect, the comparison was made for the nanocomposites processed with and without scCO2 injection. The structures of the nanocomposites were investigated with X-ray diffraction and transmission electron microscopy. Mechanical properties were also evaluated.
Processing Effects on the Tribological Properties of Thermoplastics
An important demand on engineering-technology is the optimization of materials for tribological stressed parts with regard to friction- and wear-behavior. To be able to use the full potential of improvement an optimum in processing is necessary. The morphology especially of the tribologically stressed surface-regions is influenced by the variation of mold- and melt-temperature. The dependence of tribological properties on processing conditions is shown for POM and PA66 in sliding contact against steel. The results of wear-tests are correlated with mechanical, morphological, and thermodynamic results.
Measurement of Strain Rate Dependent Material Properties for Polymers and Their Prediction from Normal Tensile Tests
Present market forces dictate that the automotive industry must increase passenger safety. Since polymer material behavior are sensitive to speed, the determination of material data at crash relevant strain rates is of great importance.This study is concerned with a new method to predict the material behavior of polymers at high strain rates. The material data is determined with normal tensile tests and this material data is subsequently extrapolated to high strain rates. The results are compared and evaluated with those from high speed tensile tests.
Ranking of PP Pipe Grades by Their Failure Behavior under Impact Loads
In this work the influence of different test specimen configurations (different local and global stress states) on the brittle/ductile transition temperature TBD in PE pipe grades (PE 80 and PE 100) was characterized under impact loads at 1 m/s. It was found that TBD determined based on an energy criteria and fracture surface analyses was highly dependent on the stress state prevailing in the different test specimens. For all test specimens lower values for TBD were found for PE 100 in comparison to PE 80, corroborating the better performance of PE 100 under the different test conditions (from near plain stress to near plain strain conditions).
Through-Thickness Process Zone Characterization at Fatigue Cracks in PE-HD
Fatigue crack growth (FCG) experiments were conducted on different PE-HD pipe grades with CT specimens. All tests were interrupted in the region of stable crack propagation. The crack front and the front of the process zone ahead of the crack were systematically characterized via microscopic methods in the thickness direction of the specimen. The effects of stress intensity factor and frequency were systematically investigated. The experimental data are employed to study the mechanisms of process zone development and to determine the effective crack length by compliance relationships (instead of using optical methods).
PEO-Na+/MMT Nanocomposite Film as Polymer Electrolytes
A polymer-clay nanocomposites of Polyethylene oxide (PEO) and Na+/montmorillonite (MMT) was prepared by a conventional melt blending method in an internal mixer. The level of intercalation of the composites of PEO with Na+/MMT layered silicates was crucial to influence the conductivity and mechanical properties as well as the thermal stability, which were studied by thermal analysis, FTIR and Wide Angle X-ray Diffraction. Thermal stability was also studied by using Thermogravimetric Analysis. The ionic conductivity and the impedance plots were measured by using an alternating current meter. It was found that PEO-Na+/MMT could be an alternative system for polymer electrolytes with high thermal stability, high tensile modulus and moderate ionic conductivity (10-6 Siemen cm-1).
A Study on the Extrusion of Open Cell Polystyrene Mixed Foams
This current study mixes two polystyrene resins with different rheology properties, PS-1 and PS-2, to present the resin with other property, and finds that the adequate mixing proportion of PS-1 and PS-2 is better between 18~25%, and perlite additive is added to carry out the minute change of property, where 1-2% difference of perlite application quantity will cause changes in complex viscosity. For the application of formulation after property changes plus difluoromethane / pentafluoroethane 50/50Wt% foaming agent, we directly adopt continuous extrusion foaming method to execute the experiment, which shows such formula combination is capable of achieving better balance in simultaneously reducing average cell diameter of foam body and maintaining the open-cell content. Via the above mentioned formula combination and process condition, the foam body produced can possesses about 30?m of average cell diameter and open- cell content higher than 90%.
Unique Crystallization Behavior of ?-Polypropylenes
The work deals with the effects of ?-nucleation and thermal conditions on crystallization and resulting supermolecular structure of isotactic polypropylene (iPP). Neat and ?-nucleated iPP were crystallized under various conditions. Strong interrelation between crystallization temperature (Tc) and ?-phase formation was found. Moreover, the content of ?-phase was specifically affected by the nucleator concentration - increasing Tc depressed the formation of ?-phase in samples containing higher amount of the nucleator while this effect was inverse when low-nucleated samples crystallized.
Processing of Antimicrobial Nanocomposites and Their Characterization
The volume of antimicrobial plastic materials in the healthcare and the food industry sector is growing rapidly. Different approaches to achieve antibacterial effects are followed. The technology discussed in this article is based on silver ion release.To obtain such antimicrobial nanocomposites, thermoplastic materials were processed with Agnanoparticles on TiO2 particles as carrier substance in a co-rotating twin screw extruder. Process parameters and the kind and amount of nanoparticles were changed to characterize their effect on the morphology, antibacterial and different mechanical properties using TEM, DSC, and tensile tests. In this work, the relation between these properties, the process parameters and the concentration of additives is presented. The processes of compounding and subsequently injection molding were optimized to get a plastic material with added value.
Clearweld™ Resins: Alternative Options for TTIR Clearwelds
Clearweld is a through-transmission laser welding process promoted for the ability to generate colorless welds. A colorless weld is generated by applying the absorbing material only at the weld interface. The coating may be applied by a liquid dispensing method such as spraying, microsolenoid dispensing, etc. The limitation of the coating process is the secondary step of applying the coating.Clearweld laser absorbing additives were compounded into various resins to be used as the bottom substrate in a weld configuration. The resins eliminate the need for the dispensing step. The laser absorbing additive has minimal affect on the coloration of the part, which allows for a broad selection of colors, both transparent or opaque. The resin is typically injection molded but may also be extruded into a film for insert molding. This paper presents results of compounding the Clearweld additive into various polymers, including but not limited to Acrylic, polycarbonate, and polypropylene.
Poly (Ethylene Terephthalate) -Organoclay- Impact Modifier Nanocomposites
This study was conducted to investigate the effects of component concentrations and addition order of the components, on the final properties of ternary nanocomposites composed of poly (ethylene terephthalate), organoclay, and an ethylene/methyl acrylate/glycidyl methacrylate (E-MA-GMA) terpolymer acting as an impact modifier for PET. Among the investigated addition orders, the best sequence of component addition (PI-C i.e. PET, Impact Modifier-Clay) was the one in which poly (ethylene terephthalate) was first compounded with E- MAGMA; later, this mixture was compounded with the organoclay in the subsequent run.
Study on the Mechanical Properties of Microcellular Injection Molded Parts
There are several benefits of using the supercritical fluid microcellular injection molding process. The weight of the parts, process conditions (material temperature, viscosity, and clamp force), shrink/warpage, dimensional instability, and cooling/cycle time are all reduced. This process is made by introducing the controlled gas during the injection stage cycle to create millions of micron-sized voids in otherwise solid thermoplastic polymer parts. The purpose of this study is to study the effects of process conditions on mechanical properties by microcellular injection molding. The weight variation was reduced by as much as 40%. This process reduced the melt temperature by about 20-30°C and also reduced the cycle time by about 5-15 s. The higher injection speed resulted in better cell structure. In addition, the supercritical fluid microcellular process did not reduce the tensile strength of the material, but the impact strength was increased by four times.
Modeling the Effects of Solid State Orientation on Blown High Molecular Weight High Density Polyethylene Films: A Composite Theory Approach
High molecular weight high-density polyethylenes (HMWHDPE) are unique, in that they can be uniformly oriented to high draw ratios to produce films with significantly enhanced physical properties. Such improvements are the result of the transformation of isotropic piles of lamellae into rigid, long, fibrous microstructures, which can be characterized by various analytical techniques. This work represents the first industrially usable approach to the prediction of mechanical properties in oriented polyolefin films and may have wider application to other fiber-like microstructure forming polymers. The model presented is tied both to the observed structural features, as well as to properties that are routinely measured in the industrial setting. These enhanced films create new opportunities for flexible packaging in high strength and stiffness applications.
Polydimethylsiloxane Polyurethane Modified Epoxy as Precursor for Manufacturing Carbon / Carbon Composites
The objectives of this study are to investigate the feasibility of utilizing the aromatic amine-terminated polydimethylsiloxane polyurethane modified novolac type epoxy to prepare carbon/carbon(C/C) composite. The compatibility of polymer blend and curing kinetic of modified epoxy were investigated. Thermal, physical and mechanical properties changes during the post-cure stage and carbonization processing are also examined.Results show that the polydimethylsiloxane polyurethane is compatible with epoxy resin when the content is below 5 phr (parts per one hundred parts of epoxy resin). The curing kinetic study show that epoxy matrix modified with polydimethylsiloxane polyurethane decrease the collision factor and increase total heat of reaction and the active energy of reaction. The polydimethylsiloxane polyurethane increases the mechanical properties after carbonization since polydimethylsiloxane polyurethane releasing the internal pressure and protecting the fiber surface during carbonization process. The Novolac Epoxy with polydimethylsiloxane polyurethane modified has better oxygen resistance and lower oxidation rate from the TGA oxidation testing results.
Welding Thermoplastic Foams
Foamed thermoplastics display economical potentials due to the material saving and reduced cycle time during the injection molding process. At present neither knowledge of the applicability of different welding methods exists, nor the process parameters to gain the optimum weld quality are known. In this paper an experimental study will be presented to analyze the effects of the process parameters on the attainable strength using the heated tool welding and vibration welding. Via three-dimensional experimental design all process-relevant parameters have been varied including the material density. It was found that the process parameters have a considerable influence on the weld results. Differences in terms of weld strength between the particularly small pores and large pores were found. Comparing to bulk material a major reduction of the cycle time has been observed. Connections between the melting characteristic and the process parameters were deduced.
CDs and Interactive Programs in Plastics Engineering Education
We have developed CDs1,2 and interactive programs that are being used in both polymer science and plastics engineering courses. These CDs contain various interactive programs and numerous animations. These materials can be used as self- learning tools with the aid of workbooks. Initial evaluation has been very positive with a high level of acceptance and use by students. The plastics industry is now the fourth largest manufacturing industry in the United States, accounting for $330 billion in annual shipments and directly employing more than 1.5 million people. A key to this industry remaining competitive with countries where workers are paid a fraction of U.S. wages is a skilled, educated, and flexible workforce. Over the course of the past five years, we have been working to address the need for technical personnel in this field through NSF funded projects whose goals have been the development of new and innovative educational materials and the dissemination and evaluation of this material.
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