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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Blends of Polylactide with Thermoplastic Starch
Blends of polylactide with thermoplastic starch are prepared using a one-step extrusion process. These materials, subsequently processed via injection molding, possess interesting properties. The tensile properties in these samples are related to the composition of the blends and also to the glycerol plasticizer content in the thermoplastic starch. These materials possess an advantage for the environment since they are fully biodegradable and are derived principally from renewable sources.
Average Temperature or Mean Kinetic Temperature: Which One Applies?
Reaction rates are not proportional to temperature, but instead follow Arrhenius behavior. Consequently, for systems with varying temperature, the “average temperature” is erroneous and should not be used. Instead, the easily calculated “mean-kinetic temperature”, should be used. The difference between these temperatures can be significant and failure to understand the differences can lead to catastrophic consequences. Specific examples of the calculations and the consequences are discussed.
A Statistical Analysis of the Tensile Strength of Blown Film
Many processing parameters have an effect on the tensile strength of blown film. In this study a Taguchi L8 designed experiment was used as a screening design. This design allowed the determination of which processing parameters had the biggest effect on the tensile strength of blown film in both the machine and transverse directions. The processing parameters examined in this experiment were: materials, die temperature, take up roll speed, blower speed, air ring gap, extruder speed and air volume.
Study of CBA-Blown Bubble Nucleation and Life Span under High Pressure Gas Environment
This research investigated the bubble nucleation and life span phenomena occurring in chemical blowing agent (CBA)-based foaming of plastics under atmosphere and high pressure conditions. The behaviour of CBA-blown bubbles exposed to various pressure conditions was observed in a high pressure chamber using optical microscope-based digital image processing system. Critical experiments were conducted to explain the mechanisms of CBA-blown bubble nucleation.
Erroneous, Accelerated, UV-Aging Results
It has been found that some thermoplastic systems survive accelerated UV weathering but fail in true environmental conditions. This is because quartz filters pass artificially high levels of 275 nm - 340 nm light, but artificially lower levels of longer wavelengths. For systems that are more reactive to longer wavelengths, the accelerated exposure tests provide false assurances of true weatherability. A specific example of this phenomenon occurring within polypropylene will be shown and discussed in detail.
Critical Issues in Extrusion Foaming of Plastic/Woodfiber Composites
Foaming of plastic/wood-fiber composites (PWC) with a fine-celled structure can offer benefits such as improved ductility and impact strength, lowered material cost, and lowered weight, which can improve their utility in many applications. This paper presents the critical issues in extrusion foaming of PWC and proposes processing techniques and strategies for producing artificial wood with enhanced properties.
Rheological and Morphological Properties of VARTM (Vacuum Assisted Resin Transfer Molding) Epoxy Resins/Clay Nanocomposites
Three types of modified organoclay were incorporated into VARTM resins at various concentrations. A Rheometric Dynamic Analyzer was used to analyze the flow behavior of the resins, while the morphology of the clay was examined by X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM). It was found that the viscosity of the resins increased after the addition of the clays and the clays were exfoliated into the matrix.
Influence of Viscosity Ratio on the Impact Properties of PS/HDPE Blends Prepared by Extrusion and Injection Molding
Blends of PS/HDPE were prepared by ribbon extrusion and injection molding. Three different PS and HDPE were used in order to modify the viscosity ratio (p). The impact properties and morphological study of test specimens are presented. The results indicate a different effect of the viscosity ratio depending of the processing method on the morphology and impact resistance. In general, it was observed better impact resistance in samples prepared by ribbon extrusion than the samples prepared by injection molding.
Ten Things Plastics Engineers Should Know about Intellectual Property
Intellectual property law has had a number of somewhat remarkable changes in recent years. For example, the scope and enforceability of patents in the United States has been modified with respect to what might be considered an “equivalent” to a claimed invention. The role of judges and juries in ascertaining the scope of a patent has been dramatically altered. This paper will identify these new and important changes in the law of intellectual property and how such issues should be considered by the community of plastics engineers.
Warpage Study on Two-Shot Injection Molding
A common problem affecting all thermoplastic parts is shrinkage and warpage. With two-shot molding the parts will have two materials with different properties molding onto one another. Through a design of experiments (DOE) the cause and effect of changing different processing parameters along with part dimensions and materials, can be used to determine the amount of warpage on the part.
The Coupling of Gas Chromatography with Olfactory Detection (GC/O) and Mass Spectrometric Detection (GC/MS) in Solving off Odor Issues
Off odor issues in packaging materials can have significant financial implications. Gas chromatography with a combination of detection techniques, olfactory (GC/O), and mass spectrometry (GC/MS) can help solve such problems. A general problem is the low detection limits afforded by the sense of smell versus the instrumental detection limits of GC/MS. Various methods of sample introduction that enhance the GC/MS response allowing identification of odor relevant compounds will be discussed.
Measurement of Swollen Volume of Polymer Melt Due to Gas Dissolution
The pressure-volume-temperature (PVT) property of polymer/gas mixtures is critically important in the polymer foaming process. Accurately measured volume swelling of polymer/gas solutions is not yet available. The objective of this paper is to propose a novel methodology for measuring the volume swelling accurately. The preliminary result using PP/N2 and accuracy verification using a known volume sphere will be presented.
Foamability of Thermoplastic Vulcanizates (TPV) with Carbon Dioxide (CO2) and Nitrogen (N2)
The foamability of thermoplastic vulcanizate (TPV) has been investigated in a customized foaming system using carbon dioxide (CO2) and nitrogen (N2) as a physical blowing agent. TPV or dynamic vulcanizate is a special class of thermoplastic elastomer that is produced by mixing a crosslinked rubber and a thermoplastic simultaneously. The influence of blowing agent content and the processing conditions on the expansion behaviour, the cell-number density and the foam structure are discussed.
The Effect of Wood Powder on Polymer Foam Nucleation
It is usually reported that wood particles in wood/polymer composite foams can act as nucleating sites. Since high wood contents are used, it is difficult to determine exactly the effect of wood particles. In this study, LDPE was chemically foamed in a twin-screw extruder and small amounts of wood (0-5 phr) were added to determine their effect. Particle size was investigated using three mesh sizes: 45-61, 104-125 and 180-210 ?m. As expected, wood particles are acting as nucleating agents reducing substantially cell size and increasing cell density.
Interpretation of Flow Curves from Semi-Hyperboloidal Dies
The contributions of shear and elongation to the measured pressure drop in flow of polypropylene melts through semi-hyperboloidal dies have been investigated with and without external lubrication. This was done with a set of dies having a fixed ratio of inlet area to outlet area and three different lengths. The flow curves obtained without lubrication have been analyzed for the dependence on length. Two distinct terms have been identified that represent the shear contributions to the measured pressure drop in unlubricated flow.
Rheological Investigation of Entangled Hybrid Copolymers of Polystyrene (PS) with Polyhedral Oligosilsesquioxane (POSS)
The thermal properties and rheological behaviors of polystyrene (PS)-based thermoplastics bearing polyhedral oligosilsesquioxane (POSS) were investigated with variation of isobutyl (iBu)-POSS weight percentage. The incorporation of POSS-group significantly decreases the glass transition temperature and the rubbery plateau modulus. These findings are attributed to an influence of the nanometer-scale POSS pendant group on the microscopic topology of the host polymeric chains and negligible interactions between POSS and PS matrix.
HDPE/Clay Nanocomposite Foams Blown with Supercritical CO2
In order to investigate the effect of clay particles on the cell morphology of HDPE/clay nanocomposite foams, research on the batch foaming process of HDPE/clay nanocomposites using supercritical CO2 was conducted. Our study demonstrates that, in comparison with pure HDPE, nanocomposites produce much finer and more uniform cell structures. Additionally, an attempt to produce a nanocellular structure was successfully performed using HDPE/clay nanocomposites.
Graphite Nanocomposites: Nylon 6 and Nylon 66 Systems
Natural crystalline graphite based graphite intercalated compounds [GICs] were exfoliated and milled into submicron graphite flakes. Graphite nanocomposites were fabricated with nylon 6 or nylon 66 resins. To examine the effectiveness of the exfoliated graphite as a reinforcement, composites with commercially available reinforcing materials were also fabricated and compared. The mechanical and electrical properties were investigated and exfoliated graphite showed comparable or better properties compared to the other reinforcing materials.
Effects of Clay Dispersion on the Mechanical Properties and Flammability of Polyethylene/Clay Nanocomposites
Intercalated and exfoliated high density polyethylene (HDPE)/clay nanocomposites were prepared by melt blending with and without the aid of maleated polyethylene (PE-g-MAn) as a compatiblizer. Their morphology was determined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of clay dispersion on the tensile properties and flammability of nanocomposites, especially those containing only a small amount of clay in the range of 0.05 ~ 1.0%, were investigated in this study.
Quantitative Mixing Uniformity Assessment in Two Laboratory Scale Devices
A technique is described to quantitatively assess mixing effectiveness. The technique utilizes infrared (IR) analysis of dissimilar polymer blends. The rheology of the blend system can be tuned through temperature to easily derive a spectrum of viscosity ratios. The technique has been applied to two common laboratory mixing apparatus, a batch mixer and a mini-twin screw extruder. Mixing effectiveness of these two devices will be described within both spatial and temporal considerations. The relative merits of the different mixing techniques will be additionally discussed.
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