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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Spectrophotometric Assessment: The Challenges of 0/45-45/0 in a D8 World
Determining the acceptability of automotive interior has typically been accomplished through visual consensus and spectrophotometric analysis. As many have experienced in this all too subjective pursuit, not only can three or more separate sets of eyes discern three or more totally diverse variations in color acceptability, our benchmark instruments of choice can offer distinctly different opinions also. Diversity in devices, innumerable surface-variation characteristics of the sample and inherent human imperfection in the repeatability of the manual “reading” process are all contributing factors to spurious spectrophotometric results. We will discuss what instrumental options we have available in order to have our electronic results correlate with what we see.
Crystallization Characterization of Injection Molded Parts Using Ultrasonic Technology
A method based on ultrasonic technology to study the crystallization characteristics of injection molded parts has been proposed. A new method for calculating the ultrasonic velocity and attenuation is presented. The ultrasonic velocity and attenuation signals, together with differential scanning calorimetry (DSC) measurements, were used to characterize injection molded polylactic acid (PLA) speci-mens annealed at 80 °C for different periods of time. Experimental results show that the ultrasonic velocity and the ultrasonic attenuation increased with the degree of crystallinity in the annealed specimens. This suggests that the non-destructive ultrasonic technology could be an effective tool in characterizing or monitoring the crystallization of injection molded parts during or after injection molding.
Glass Fiber Reinforced POM with Superior Mechanical Properties– Hostaform® XGC Series
Celanese has developed a new series of glass fiber reinforced polyoxymethylene (POM) co-polymers, - Hostaform® XGC (“Xtreme Glass Coupled”). Glass Fibers are commonly used to enhance stiffness and strength in thermoplastics. The adhesion between the fiber and the polymer matrix plays a predominant role governing the characteristics of the resulting reinforced plastics. Application of a specific coupling technology, together with the modification of the polymer backbone , leads to a unique mechanical property profile. The advantages of these products are a combination of improved strength and impact performance.
Antimicrobial Effects of Polymer Blended Triazole Derivatives
In this work, we have synthesized an amino acid conjugate of the triazole derivative 2-Amino-5-propyl [1,2,4] triazol [1,5-a] pyrimidin-7-(4H)-one (Triaz). The amino acid utilized is arginine due to its basic properties, thus rendering the final synthesized conjugate a positive charge. It is well known that cationic peptide conjugates show enhanced antimicrobial activity. Thus, we have examined the antimicrobial activity of the conjugate in the presence of the fungus Rhizopus. Further, fungal growth was monitored in a range of hydrophobic and hydrophilic environments by blending the conjugate with polymers such as polyethyleneglycol diacrylate (PEGDA), t-butyl acrylate (TBA) and diethylene glycol (DEG). Our results indicate that addition of PEGDA reduced antimicrobial growth, while DEG showed enhanced growth when Triaz was not conjugated with the amino acid. Thus the conjugate-polymer composites may have potent antimicrobial activity.
Acoustic Behavior of Open-Cell Foams Backed with an Air-Gap
Open-cell thermoplastic based materials have elicited much interest in the field of sound absorption due to its recyclability and high capabilities in airborne dissipation. In this work, open-cell material with high density polyethylene (HDPE) is fabricated and used in the construction of multi-layer sound absorption systems for lower frequencies. The preliminary study results show that a combination of air gap with high open-cell material can significantly improve the low frequency absorption of open-cell materials. In the application of this concept, the requirement for thick materials to obtain the required sound absorption coefficient may be eliminated. This paper discusses two multi-layer sound absorption systems constructed with open-cell HDPE material and an air gap.
Burn Mark Prediction in Injection Molding
Defects in injection molded parts are undesirable with increasing part quality. The root cause for burn marks (dieseling) is the rapid compression of trapped air in the mold. An approach for estimating the air temperature in the cavity is presented that allows the prediction of burn marks. The approach uses screw position signals coming from the machine to estimate the temperature increase due to compression, the heat transfer to the mold and the heat transfer to the melt front. Effects of the injection rate, melt temperature and mold temperature were experimentally compared to analysis results. The estimation technique provided the correct trends for most effects. The analysis offers a potential opportunity to incorporate on-line determination of burn marks for quality control.
A Study on the Acoustic Behavior of Micro Perforated Panels: Experiment and Modeling
Solid and foam 1mm-thick polypropylene injection molded parts were produced using the advanced structural foam injection molding machine. Relatively uniform cell morphology was obtained when the polymer melt was injected with relatively high pressure and high flow rate. Foam samples with 75%, 4E8 cell/cc, and 10?m of void fraction, cell density, and cell size respectively were produced. The samples were perforated with 500?m, 400?m, 300?m, and 200?m in size considering a 1% perforation ratio for all the samples. Solid and foam micro perforated panels (MPPs) for sound insulation were developed. The foam MPPs showed 6% to 35% higher absorption coefficient than solid MPPs when a 6mm air-gap was considered.
Defining Mechanical Performance Requirements for Flexible Packaging Utilized in Military Rations
The objective of this study is to determine which material properties are critical for package survival during rough handling studies, which simulate the stresses and rigors that military rations are subjected to throughout the logistics cycle. Three polyolefin films with varying degrees of mechanical performance were converted into pouches, filled with either food or a simulated food item and packed into the military’s existing individual ration, the Meal, Ready to Eat™ (MRE™). Twenty four cases, each containing twelve MRE™ meals, were subjected to a rough handling sequence that included vibration and drop testing at ambient conditions. Upon completion of rough handling the rations were opened and pouches were inspected for mode of failure and failure rates. Failure rates of the three polymeric pouches and current foil based pouches were recorded and compared to selected film and package properties, such as Young’s modulus, tensile strength, tear strength, puncture resistance, impact resistance, seal strength, and burst resistance. It was found that puncture and impact resistance showed the highest degree of correlation with failure rates.
Modeling Polymer Failure under Creep Loading through Simulation of Crack Growth
Plastics used for structural applications are often subjected to creep loading and component lifetime will be limited by crack propagation. A finite element model of crack growth in plastics subjected to creep loading is developed. The model is comprised of a viscoplastic model of the bulk material and a cohesive zone model for tracking crack growth. Model parameters are found by curve fit to experimental data for polyethylene sheet samples. Model predictions for creep behavior and time to failure under creep loading conditions are compared to published data for HDPE. The model predicts the trends observed in the published data.
Processing of Biomass Fillers and Reinforcements at Entitled Capacity on Co-Rotating Twin Screw Extruders
Polymers are increasingly being combined with renewable biomass fillers and reinforcements to improve product performance, reduce cost, reduce product density, improve aesthetics and/or reduce the carbon footprint typically associated with plastics. The use of renewable materials for fillers and reinforcements in plastics has existed for several decades, however, their acceptance is rapidly expanding due to increasing plastics costs and environmental concerns. Unfortunately, a common property most of these materials share - sensitivity to heat and shear, limits their availability to be mass produced in an efficient manner in order to be cost competitive with commodity plastics and thermoplastic composites. However, a better understanding of the physical mechanisms that contribute to the onset of thermal degradation and of the technologies available to prevent such can enable significant capacity enhancements when processing biocomposites using co-rotating twin screw extruders. Another characteristic of many of these materials is that they possess a low bulk density, making them difficult to transport into the extruder at a high throughput. Technologies have recently emerged that can effectively improve the conveying efficiency of “difficult-to-feed” fillers and reinforcements.
Residual Stress Analysis of Compression-Molded Poly(Ether Ether Ketone) Cylindrical Parts
Cylindrical parts were compression-molded using polyetheretherketone (PEEK) fine powder. Post-molding thermal stress relief was executed through systematic variations in time and temperature cycles. Following stress relief, washers were cut from the cylindrical stock shapes and used in the analysis of residual stress. Quantitative determination of the residual stresses along the circumferential direction was carried out based on displacement data obtained by a ring slitting and layer removal method. Thermal and morphological properties of the material were characterized, and their relationship with the residual stress distribution in the material is discussed.
Chemical Resistance of Pigments in a Plastic Substrate
Plastics are used in numerous applications where they come into contact with acids, bases and chlorine containing chemicals, for example common bleach. These include packaging of all sorts, home and garden uses, and building and construction applications, for example. Chromatic pigments used to color these polyolefins may or may not be durable over time depending upon how the chemical penetrates the substrate and how resistant the pigments are to the chemical agent. One application of particular interest is also what colorants can be used in conjunction with recreational pools and pool chemicals. This paper will present data on the color change of pigments exposed in such situations. Emphasis will be on polyolefins, but data from synthetic fiber testing can also be illuminating. An attempt will be made to understand the results on the basis of pigment chemistry, concentration, and particle size.
Understanding Processability of PA11 via Rheology
Polymers are continuously being introduced in applications where metals have been traditionally utilized. For example, PA11 is now being used in the oil and gas industry in underwater flexible pipelines. There are some challenges that are presented when using these nontraditional materials of construction, and likewise, there are interesting challenges that arise during processing. Due to molecular weight growth from shearing and thermal history, the rheological behavior of this resin is a function of time. The molecular weight increase leads to viscosity increase, which reduces sag after extrusion, but hinders flow inside the die. These competing mechanisms must be controlled during processing. This experimental study will help in the understanding of the rheological changes during processing by showing the influence of time, temperature, thermal history and moisture content on the rheology of PA11. Modeling the change in viscosity, which affects production parameters and throughput in extrusion processes, is part of the future work of this study. Beside the temperature-shifting factor, the thermal history and moisture content were identified as playing a critical role in processing tuning. Conventional shear thinning models fail to predict the behavior of this type of material. It is necessary to investigate modeling strategies to assess the appropriate processing conditions of PA11.
High Temperature Flexible PPS Products for Harsh Environments
There has been an increasing interest for high temperature flexible materials for growing market applications, such as deep ocean extraction in oil and gas industry, and under the hood fuel handling in automotive industry. This trend has prompted the search for a material that can operate above 130 °C and often in harsh chemical environment. A series of flexible polyphenylene sulfide (PPS) products were developed to enable high temperature tubing/piping applications in oil & gas and automotive industry. These new flexible PPS materials demonstrated superior heat resistance up to 165 °C and low temperature impact resistance down to -40°C. The flexible PPS materials also showed excellent chemical resistance to fuels, oils and variety of automotive fluids. More importantly, these material can be processed into parts, tubes, pipes, tanks, wires, films and sheets using injection molding, extrusion, blow molding and wire coating.
Thickness Measurement Methods Aiding Lightweighting of PET Bottles
The aim of lightweighting PET bottles is to reduce waste in material use by optimizing the design and manufacture process. Efficient lightweighting development requires adapting robust techniques for thickness measurements. Knowledge of the final thickness distribution at different locations of the bottle is essential for identifying critical locations that could be modified in the preform or mold. X-ray tomography, IR-based thickness measurements, and Hall Effect techniques have been demonstrated as nondestructive tools for thickness measurement. Some methods are slow or expensive. Here, a low cost method for thickness measurement of PET bottles based on cross section measurement also was demonstrated using an optical scanner.
Lightweight Polypropylene-Carbon Nanotube Foams with Low Filler Content, High Permittivity and Low Dielectric Loss for Charge Storage Applications
Microcellular polypropylene-multiwalled carbon nanotube (MWCNT) composites with low filler content exhibiting high dielectric permittivity, and low dielectric loss are reported. Nanocomposites were prepared by melt compounding and foamed using supercritical carbon dioxide in a batch process. The introduction of cellular structure decreased the dielectric loss of the nanocomposites up to five orders of magnitude, while the decrease in dielectric permittivity was only 2-4 times. Thus, microcellular composites containing only ~ 0.34 vol.% MWCNT presented a frequency-independent high dielectric permittivity (~ 30) and very low dielectric loss (~ 0.06). The improvement in dielectric loss was explained in terms of the formation of effective nano-capacitors caused by foaming action (biaxial stretching and uniaxial compression) and volume exclusion. The results of this work reveal that high dielectric nanocomposites can be developed using foaming technologies for charge storage applications.
An Innovative Method to Increase the Charge Storage Capability of Polymer Nanocomposites
Microcellular polypropylene-multiwalled carbon nanotube (PP-MWCNT) composites exhibiting high dielectric permittivity and low dielectric loss at low MWCNT content are reported. Nanocomposites were foamed using N2 in injection molding process. The electrical and dielectric performances of the foamed samples are compared against those of compressionmolded and injection-molded solids. In addition to 35% density reduction, the introduction of cellular structure provided a unique arrangement of MWCNTs around cells favorable to enhancing the dielectric properties. Therefore, foams containing 1.25 vol.% MWCNT presented a dielectric permittivity of ?'=68.3 and a dielectric loss of tan ? =0.05, highly superior to those of the compression-molded (?'=14.1 and tan ?=0.39) and injection-molded (?'=17.8 and tan ?=0.04) solids. The results of this work reveal that high performance dielectric polymer nanocomposites can be developed using foaming technologies for charge storage applications.
One-Step Nanocellular Foaming of Clarified Polypropylene Using Supercritical CO2
Nanocellular foams of clarified isotactic polypropylene (iPP+clarifying agent) were prepared through one-step batch foaming process with supercritical carbon dioxide (CO2). Clarifying agent, Millad NX8000, was used in order to promote cell nucleation. Clarified iPP was prepared using twin-screw microcompounder. Crystallization behavior of iPP and clarified iPP was studied using DSC. Cellular structure of the foam was also characterized. Depending on the foaming condition, foam structure was obtained in both micro and nano scales. Nanocellular foams with the cell size distribution of 33-260 nm and cell density of about 1014 cells/cm3 was achieved by controlling the size of the crystals within iPP. An optimum foaming temperature was found wherein the smallest cell size with highest cell density could be produced.
Morphology and Mechanical Properties of Polylactic Acid/Cellulose Nanofiber Composite Foams
This paper investigates the foaming behaviors of polylactic acid (PLA)/cellulose nanofiber composites and the mechanical properties of the composites and their foams. The composites were fabricated by mixing PLA and nanofibers in a solvent with different fiber contents, followed by drying and hot pressing into test specimens. The composites were then foamed via a batch foaming process with CO2 as a blowing agent at different foaming conditions. The effect of nanofiber content on the cell morphology of PLA was studied. The impact strength and thermo-mechanical properties of PLA composites and their foams were also investigated.
Performance Attributes of Thermoplastic Polyurethane Golf Ball Covers
Injection moldable thermoplastic elastomers (TPE) have been used in golf ball constructions since the 1960s. They provide an attractive combination of performance, processability, and cost when compared to thermoset materials. In particular, ionomer based TPEs are well suited for use in golf ball cover layers as they exhibit attractive properties such as high rebound resilience, good durability, excellent UV stability, and hydrophobicity. However, in multilayer golf ball constructions where the goal is maximum performance, thermoplastic polyurethanes (TPU) are better suited for use as cover materials. In this study, the thermal properties, mechanical properties, dynamic mechanical-thermal properties, and final golf ball performance attributes of a polyether based TPU were characterized and compared to a relevant ionomer based golf ball cover composition.
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