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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Constant Temperature Embossing (CTE): Process Analysis
The goal of this paper is to analyze the Constant Temperature Embossing (CTE) process by constructing a process model to determine the change in material parameters during the process. The process model is developed by combining the non-isothermal crystallization kinetics and suspension based rheological models. A shift factor is determined from the non-isothermal crystallization kinetics to predict the crystallization behavior at temperatures where the properties are difficult to measure. A suspension based rheology model is chosen to represent the change in viscosity of the polymer during the process as the increase in particle concentration. The thermal and rheology models are then merged by considering certain key assumptions, and a process model to determine the change in material properties during the CTE process is constructed.
Impregnation Process for Fiber Hybrid Braided Reinforcement Thermoplastic Plastic
The purpose of this study was to clarify the process of impregnation for hybrid braided FRTP. First, intermediate material was made and investigated. Second, braided fabric with some structure was made and by these braided fabric, moldings with some molding time were molded. After investigation of impregnation-property and mechanical property, it was clarified that essential molding time and the gradient of decreasing in un-impregnation ratio to molding time of BY and MEY were different according to the materials and to reduce un-impregnation area was important to improve mechanical property.
Friction Coefficient Measurements Using a Timoshenko and Van Karman Device: Bulk Polymers
In this paper, an alternative method to using the pin-on-disk tribometer was used to measure the kinetic friction coefficient of polymers. This method is based on the principle of the Timoshenko and Van Karman device . Compared to the pin-on-disk tribometer, this method is more cost effective and does not require precise manufacturing. Experiments were conducted to measure directly the period of oscillations from which the friction coefficient can be evaluated. Period is measured by IR timing device and Laser Vibrometer (LV). Three materials are tested, namely polyacetal (POM), Acrylonitrile butadiene styrene (ABS), and Polymethyl methacrylate (PMMA). The effects of normal force and sliding speed on the friction coefficients of these polymeric contacts are studied. Results show that both the normal force and the rotation speed of the rollers influence the friction coefficients. These observations conflict with the classical laws of friction.
Comparison of the Flow Performance Between Internal and External Deckling in Flat Film Die Systems
Deckles are devices useful to adjust the slot width of extrusion dies, and hence the extruded product width. There are basically two types of deckles: (i) internal deckles are made of components placed inside the die flow channel to block the flow channel to a specified width upstream the die lips, and (ii) external deckles typically comprise blockage devices positioned directly on and external to the die lips, at the exit orifice. To understand the fundamental differences in flow performance between the two technologies, 3D Computational Fluid Dynamics (CFD) models were built. A comparison of the original die width to the internally and externally deckled dies is carried out by evaluating the flow characteristics such as velocity uniformity at the die exit and Residence Time Distribution (RTD) in the die flow channel. The flow models show that the performance of an internally deckled die is close to that of a non-deckled die, while the external deckle system results in non-uniform flow distribution and broad RTD due to the occurrence of a large stagnation area upstream of the external deckle.
Decrosslinking of crosslinked HDPE via ultrasonically aided extrusion
Decrosslinking of crosslinked HDPE (XHDPE) at various processing conditions is performed by means of ultrasonic single and twin screw extruders. Without the imposition of ultrasound the high flow rate in the single screw extruder was impossible to achieve due to an excessive torque. Gel fraction, crosslink density, dynamic properties and mechanical properties of the virgin HDPE and XHDPE and decrosslinked XHDPE and is measured. Significant decreases of gel fraction and crosslink density of decrosslinked XHDPE was observed indicating the occurrence of decrosslinking. A universal linear relation between the normalized gel fraction and the normalized crosslink density is found, regardless of the type of extruders and processing conditions. The decrosslinking effect induced by ultrasound increased with the ultrasonic amplitude. The increase of amplitude led to a decrease of the complex viscosity and storage modulus and increase of the loss tangent of decrosslinked XHDPE. The viscosityfrequency curves were well described by a power-law model with the consistency and power law indices linearly increasing and decreasing with crosslink density, respectively. The dynamic characteristics of sol indicated an increase in polymer chain branching due to decrosslinking effect, as detected by an increase of the activation energy of viscous flow. The mechanical properties of decrosslinked XHDPE showed a strong dependence on the type of extruder and a no trend on processing conditions due to molecular complexity of the decrosslinked XHDPE.
Morphological Aspects of Injection-Molded Polypropylene with Metallic Pigments
Innovation, design freedom, cost and weight reduction are some factors for the replacement of metals by plastics. Plastics continue to offer attractive solutions for design engineers. The metallic effect obtained by incorporation of metal particles in polymers by injection molding has the advantage of eliminating post processing techniques such as painting or metallization. Moreover, it reduces production costs and time to get a superior part quality. Nevertheless, undesired defects in the final appearance of parts are common, such as flow lines and weld lines. These defects occur due to inhomogeneous orientation and anisotropy of the metal particles. Very few studies are reporting the influence of metallic particles on the morphology development of PP parts. This study focus on the production of composite materials made of PP/metallic pigments (aluminium, bronze and cooper) by injection moulding and on the influence of the metallic particles on the aesthetic and morphological properties of the parts.
A Safe and Low-Odor Organic Peroxide Formulation Designed for the Rotational Molding of Crosslinked Polyethylene
The rotational molding industry has experienced safety, hygiene and quality issues when using 2,5- methyl-2,5-di(tbutylperoxy) hexyne-3 (referred to as P-H3 in this paper). P-H3 at >93% assay is the traditional organic peroxide crosslinker for the rotational molding of crosslinked HDPE. P-H3 is classified as a subsidiary explosive based upon United Nations and USA safety testing. Furthermore P-H3 exhibits undesirable air and skin hygiene issues during the manufacturing and handling of crosslinked parts due to the primary skin irritants that are created when P-H3 decomposes to crosslink the HDPE. These low molecular weight triple bond by-products are also responsible for the discoloration of the crosslinked HDPE. The under-cure and general “inconsistency of cure” quality issues are traced to the incompatibility and volatility of P-H3 in the HDPE molding powder. Years of safety testing and R&D culminated in the development of Luperox® MIX (referred to as P-MX in this paper), specifically designed for the safe and reliable rotational molding of crosslinked HDPE. P-MX is a homogeneous blend of m/p-di(t-butylperoxy)diisopropylbenzene, triallyl cyanurate and a free-radical trap. The data in this technical paper demonstrates how P-MX addresses certain safety, hygiene and quality issues of P-H3. P- MX is a homogeneous solid at room temperature, with a 45°C melting point.
The Application of Rheological Techniques in Selecting Plasticizers for PVC Processing
This paper focuses on three different rheometric techniques to analyze how dibenzoate and other plasticizers affect flexible polyvinyl chloride (PVC) processability. Both plastisol and melt compounds will be considered. This analysis includes the use of a research rheometer in an oscillatory mode to evaluate plastisols. A torque rheometer was used to evaluate melt compound formulations. New dibenzoate plasticizers and a new monobenzoate have been introduced and the nature of the solvator class of these new benzoates will be evaluated.
Thermal Stability of Castor Oil Derived Polyurethanes
Polyurethanes synthesized using both unmodified and epoxidized, ring opened castor oil as a polyol were prepared and their thermal properties tested using thermogravimetric analysis and differential scanning calorimetry. Chemical changes upon degradation were investigated using Fourier transform infrared spectroscopy. The kinetics of degradation were elucidated using the Flynn-Wall and Flynn procedures. Epoxidized castor oil produces a rigid polyurethane exhibiting glassy behavior at ambient temperatures. All methods to determine activation energy of degradation indicate that, in a nitrogen environment, polyurethanes from unmodified castor oil are more thermally stable than those from modified castor oil. The appearance of peaks corresponding to amines, amides, and esters in FITR analysis of degraded samples suggests that the initial degradation step of the polyurethanes studied is the breaking of the urethane bond.
Effects of Glycerin Antifreeze on CPVC
There are multiple applications where chlorinated poly(vinyl chloride) (CPVC) may come in contact with glycerin. One common application is in fire suppression systems that could be subjected to subfreezing temperatures. Chlorinated poly(vinyl chloride) is increasingly being used for these systems in place of metal because of its many advantages, including the ease of installation, weight reduction, cost benefits and chemical resistance. When CPVC piping is used in an area that has the potential to freeze, an antifreeze solution must be used in the fire suppression systems to suppress the freezing temperature of the water and reduce possibility of failure of the piping system. Glycerin is a commonly used antifreeze for this application. The following article discusses the effects of using glycerin with CPVC piping and presents a case study of the use of bio-derived glycerin as an antifreeze agent. In general, it was found that glycerin from the bio-diesel industry had adverse effects on the CPVC.
Fabrication and Characterization of Polyvinyl Alcohol (PVA)/Nanofibrillated Cellulose (NFC) Filaments
This paper presents a new process to fabricate single polyvinyl alcohol (PVA)/nanofibrillated cellulose (NFC) filament and its tensile properties at various ratios (0.5 ~ 3 wt %) of NFC. The fabrication process generally contains four steps: NFC isolation, preparation of PVA/NFC solution, gel spinning and drying, and filament stretching. The ultimate strength of PVA/NFC increased by almost 2 times, compared with stretched neat PVA filament. In order to ensure that the NFC fibers disperse well in PVA solution, high shear processing was employed. To study the possible degradation of PVA caused by high shear, the parallel plate rheometer was used to investigate the viscosity of PVA/NFC solutions. The PVA crystal orientation in PVA/NFC filament was also characterized by wide angle x-ray diffraction (WAXD).
Fractographic Examination of Failures in Polycarbonate and Polyacetal due to Impact, Tensile, Fatigue, and Creep Mechanisms
Fractography is a powerful tool in the failure analyst’s arsenal, allowing unknown conditions that led to a failure to be revealed by examination of a fracture surface. In this study, fractures generated by different failure mechanisms were examined by scanning electron microscopy (SEM) to discern key characteristics and distinguishing features. Amorphous polycarbonate (PC) and semicrystalline acetal homopolymer were fractured by impact, tensile overload, cyclic fatigue, and creep. SEM images are provided and discussed.
Impact Modification of PLA Using Biobased, Biodegradable Mirel PHB Copolymers
This work will focus on an approach to improve the impact toughness of poly (lactic acid) or PLA without compromising the biobased carbon content and compostability of PLA. Specifically, low-crystallinity and amorphous PHB copolymers were demonstrated to be very effective in improving the toughness of PLA at modest loading levels of 10-20 weight percent. This presentation will also compare the above approach with urethane, butadiene and acrylic impact modifiers along with the impact modification provided by other compostable polymers such as PBS and PBAT. Of particular significance is the extent of impact modification provided by an amorphous PHB copolymer (M4300 @ 10-20% loading) wherein the blend demonstrates a combination of mechanical properties that rival those of some engineering thermoplastics. Morphological considerations for the observed improvement in impact performance will also be highlighted.
The World's Highest Heat Melt-Processable Amorphous Thermoplastic
A new class of high performance amorphous thermoplastic polyimide (TPI) resin has been designed with a glass transition temperature exceeding 300°C while still being 100% melt-processable. Further, this novel material has been bestowed with the highest UL (Underwriter’s laboratory) RTI rating in the world for an unfilled thermoplastic. The polymeric material offers outstanding high temperature strength and dimensional stability which makes it attractive to be positioned in applications with an emerging need of such materials that are truly melt-processable while giving as-molded properties for end use.
Complex Fiber Orientation Distributions within Injection Molded End-Gated Plaques
The Method of Ellipses has been applied to short and long fiber polymer composites in order to quantify the fiber orientation distribution within the end-gated plaque. Short and long glass fibers with post- processing average fiber lengths of 0.364 and 3.90 mm, respectively, have been studied at multiple percentages of mold flow, including at the gate and entry region and near the advancing front. Additionally, orientation data has been acquired for short glass fibers at multiple locations of plaque width including near the side mold wall. Preliminary data suggests that the orientation of short and long glass fibers is similar along the centerline of the plaque, with both fiber lengths developing the predicted core-shell structure at moderate to high percentages of mold fill. However, short glass fibers exhibit a broad and relatively uniform orientation distribution in the regions of complex flow at high percentages of plaque width, with a substantial increase in flow-aligned fibers. Work is ongoing to complete analysis of long glass fibers in regions of complex flow near the side walls of the mold.
Material Optimization and Performance Evaluation of PolyVinyl Alcohol (PVOH) Films in Fresh and Salt Water for Decelerator Applications
Material optimization of biodegradable and water soluble polymers along with the influence of fresh and salt water conditions on the performance of polyvinyl alcohol-based films was examined for a U.S. Naval sonobuoy decelerator application. PVOH films of various thicknesses were produced on a manufacturing-scale lamination line using a solvent-based adhesive. Salt water and its temperature significantly influenced dissolution properties of the films. Mechanical properties of the as-received and laminated films were also examined and reported.
Effects of Biodiesel on Plastics
Many chemicals have the ability to attack on plastics as solvents and can lead to failure. In some cases, the source of the solvent is not well defined. In this study, the effect of biodiesel, a fatty acid methyl ester, on various plastics, namely polyamide 6 (PA 6), polycarbonate (PC), acrylonitrile-butadiene- styrene (ABS) and ABS/PC plastic blends was studied. Various feedstocks of biodiesel were also studied, including, soy bean oil (new and used), animal fat (tallow), corn oil as well as choice white grease. The plastics samples were tested under ASTM standard where a predefined strain is applied to the samples prior to exposure to the solvent (biodiesel). It was found that under the majority of combinations, other than PA 6, cracking was seen within 12 hours, and with ABS/PC and PC cracking was seen in minutes. Thus, it has been shown that biodiesel can be a degrading solvent for engineering plastics, such as PC, ABS and ABS/PC blends.
The Effect of Processing Flows on Polystyrene/Nanotube Nanocomposite Conductivity and Structure: 3D Visualization of Cluster Distributions
The electrical conductivity of polymer nanotube composites can be dramatically modified during processing steps. We examine the interplay between processing, the multi wall carbon nanotube (MWCNT) network structure and the resulting conductivity through 3D measurements of cluster size distributions and orientation. We discover that the nanotubes assemble into clusters whose mass distribution follows a classic power law with a slope of approximately -1. This mass distribution is relatively insensitive to the imposed flows over our accessible shear range, even though the conductivity changes by orders of magnitude. The orientation distribution of the MWCNTs within the clusters is strongly dependent on the flow type and its magnitude, but does not correlate with conductivity. These results point to the dominant role played by the nanotube –nanotube contact resistance as a determinate of composite conductivity.
Investigation of Cold-Runner Injection Molding Processing Parameters and Their Effects on Product Optical Properties
This paper describes current efforts to investigate and expand melt modulation capabilities to control the packing parameters of cold-runner based injection molding processes. Packing parameters, including packing pressure and packing time, have significant impact on the internal molecular orientations, mechanical properties and optical performance of injection molded polymeric products. The investigation focuses on manipulating and controlling packing parameters in order to produce molded parts with different optical properties in each injection molding cycle. Numerical simulations of common thermoplastic optical polymers, such as PMMA, PC, and PS and some experimental results are also presented.
Investigation of Fracture in Polymers Using a Cohesive Zone Model
Polymers are increasingly being used for engineering structures and medical devices because of their excellent corrosion resistance and low cost compared with metals. However, the lifetime of plastics used in severe environments is significantly reduced due to environmental stress cracking (ESC). Current understanding of ESC in polymers is mostly empirical. In this paper, a methodology for investigating ESC in polymers is presented. The proposed approach, based on the cohesive zone model (CZM), is capable to characterize the degradation in the fracture zone explicitly, independent from the bulk material. In our preliminary investigation, the fracture on an elastic-plastic material was simulated, and the results were compared to a published paper. The simulation outcome indicates that the CZM is an effective tool to study fracture propagation in polymers under ESC.
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