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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CPVC Sprinkler Pipe in Contact with Suspected off-Ratio Urethane Foams
This paper discusses failures in a residential fire sprinkler system using CPVC pipe surrounded by sprayed urethane foam insulation. The pipe had multiple circumferential cracks. The external surface had a brown coloration in cracked areas. Chemical analysis showed presence of chemicals in the polymer consistent with components that may have been present in the foam. These chemicals had solubility parameters and boiling temperatures consistent with causation of Environmental Stress Cracking of CPVC. Accelerated exposure of strained CPVC pipe sections to three of these chemicals showed rapid formation of suspected environmental stress cracks.
Feasibility of Double Melting Peak Generation for Expanded Thermoplastic Polyurethane Bead Foams
This study investigated the effects of dissolved CO2 on the crystallization of hard segment (HS) to generate double crystal melting peak for expanded thermoplastic polyurethane (ETPU) bead foam manufacturing. The double crystal melting peak is generated while annealing at elevated temperatures in a autoclave-based ETPU foaming process. The influence of saturation temperature, time, and pressure on the generation of double melting peak structure in TPU was investigated. It was observed that higher saturation temperature assisted in the improvement in the size and perfection of the smaller HS crystals and resulted in formation of double melting peak close to the melting point of TPU. However, the saturation pressure was the most critical parameter to enhance the double melting peak. Furthermore, in the presence of dissolved CO2, the saturation temperature required to generate the double melting peak in the TPU decreased significantly due to the plasticization effect of CO2. The longer saturation time increased the amount of perfected HS crystals with a high melting temperature.
Experiments with Hot Tool Joining of Thermoplastics to Metal
With the requirements for increasing fuel efficiency of automobiles lightening of structures would require joining of dissimilar materials like metals to plastics. In this study, thermoplastics were joined to metal using a heated tool. The metal substrate was textured with a fine knurl pattern and heated for a preset time by pressing it against a hot tool that was kept at a high temperature. Then the metal part and hot plate were retracted, and the cool thermoplastic sheet was pressed against the hot metal surface for a preset time. The hot metal would then melt the thermoplastic surface resulting in flow and wetting and joining of the parts together. Increasing the heating time generally increased the joint strength until an optimum was reached. HDPE to steel joints were slightly stronger and more consistent than HDPE to aluminum joints. For a fixed heating time, the PC and HDPE steel joints were stronger than PP and acrylic to steel joints.
Polypropylene Crystallization in Bulk during an Extrusion Process: Effect of Molecular Weight and Supercritical Carbon Dioxide
Through in-situ visualization, the crystallization behavior of two grades of polypropylene (PP) with medium and high melt flow index was investigated during an extrusion process in the absence and presence of the supercritical carbon dioxide. In all experiments conducted in this study, the crystalline phase (i.e., crystallite) was visualized in the melt during continues process by decreasing the processing temperatures. However, the crystallization onset and the crystallites’ morphologies vary from one condition to another depending on the material molecular weight and the presence of the gas. In the absence of blowing agent, effect of processing conditions (i.e., temperature profile, and flow rate) on the crystallization was studied. It was observed that increasing the flow rate didn’t show any significant changes on the crystallization onset for the lower molecular weight PP. On the other hand, the crystallization onset was shifted to a higher temperature profile for PP with higher molecular weight. The results indicate that the flow-induced crystallization (FIC) is more active in PP with higher molecular weight. In the presence of supercritical CO2, the onset of crystallization was lowered for both PPs studied here mostly due to the CO2 plasticization effect. However, this temperature depression was more pronounced in the higher molecular weight PP than that of lower molecular weight PP, suggesting that carbon dioxide also hinders the effect of FIC.
Metal Replacement with Specialty Thermoplastic Solutions in Heat-Sensitive Automotive Applications
Automotive OEMs are facing immediate and continuous short- and mid-term targets to improve fuel economy. Light-weighting and energy efficiency are key enablers to reach these targets. Light-weighting primarily involves implementing material solutions with an appropriate performance/weight ratio for an application, without compromising quality and costs. Energy efficiency mainly comes from power-train innovations, including electrification of the car, with innovations in electronics (LED, power electronics, alternative energy, etc.) translated to automotive uses. Specialty thermoplastics have a key role to play in this respect. This paper/presentation from PolyOne will describe how thermally conductive thermoplastics can help achieve these targets, specifically in heat-sensitive automotive applications - from the fundamentals of thermal management and the corresponding material properties, to a case study of metal replacement in automotive LED lighting applications.
Importance of Application Representative Sealant Test Methods
Polyethylene (PE) based sealants are an integral part of the food packaging industry. Their use in packaging ranges from simple multi-layer PE film configurations to complex multi-polymer laminate structures. There is a constant drive to develop sealant resins that offer an improved balance of properties in terms of ease of processing, excellent sealant and physical properties. When developing new sealant resins, it is also essential that the performance be characterized by test methods relevant to converters and end-users. This study assesses the sealant performance of various PE resins in the context of molecular architecture, sealant performance test methods, and application specific packaging fabrication conditions.
Simulation of Single Fiber Motion and its Application to Short Fiber Orientation Predictions in Composites Processing
A simulation-based approach is presented to predict the motion of a single fiber or a set of fibers in a viscous fluid with application to short fiber composites processing. This model is developed specifically to reconsider basic assumptions made in Jeffery’s model published in 1922 which forms the basis for nearly all polymer processing fiber orientation prediction today. Our approach computes the velocities in the fluid domain surrounding a fiber, and the fiber motion is determined to zero the forces and torques on the moving fiber. A numerical integration method is then used to determine the fiber’s position and orientation as a function of time. This approach is used to better understand the effect of fiber shape, far-field boundary condition, velocity profile, and neighboring fibers on fiber orientation. Special attention is given to the effect each of these have on recent observations that current fiber orientation models based on Jeffery’s equation tend to over-predict the rate of fiber alignment.
Review of Analytical Models of Anisotropy-Induce Spring Forward Effect via FEA Simulation and an Experimental Study
The increase of residual stresses during the phase change of thermoset fiber-reinforced composites causes unintended situations. A specific situation of interest is the angular distortion in curved fiber-reinforced thermoset parts, also referred to as the spring-forward effect or anisotropy induced curvature change. It has been identified that conventional analytical models deviate from experimental results when changing the part thickness. Therefore, it is of interest to study the effect of thickness variation on the final angle change. Some of these models neglect the effect of phase change in the distortion. This research relates the current scope of analytical and experimental models to predict spring-forward effect. It is necessary to extend the current models to involve the cure time-temperature-diagram (TTT) of thermoset resins.
Short Cellulose Nanofibril/Polyvinyl Alcohol Nanocomposite Fibers
Short cellulose nanofibrils (SCNF) were investigated as a reinforcement for polyvinyl alcohol (PVA) fibers. SCNF fibers were mechanically isolated from hard wood pulp after enzymatic pretreatment. Various levels of SCNF were added to PVA and gel-spun into continuous fibers. The molecular orientation of PVA was affected by a combination of wet drawing during gel spinning and post-hot-drawing at a high temperature after drying. A maximum total draw ratio of 27 was achieved with various SCNF contents investigated. The PVA crystal orientation increased when small amounts of SCNF were added, but decreased again as the SCNF content was increased above about 2 or 3%, likely due to SCNF percolation resulting in network formation that inhibited alignment. SCNF fillers were effective in improving PVA fiber tensile properties (i.e., ultimate strength and elastic modulus). Shifts in the Raman peak at ~1095 cm-1, which were associated with the C–O–C glycosidic bond of SCNF, indicated good stress transfer between the SCNF and the PVA matrix due to strong interfacial hydrogen bonding.
Using Zemac® Copolymers to Upgrade Virgin Nylon Performance
Nylon is widely used in many applications. At the 2013 ANTEC, our paper covered the results obtained with compounding primarily recycled nylon with the addition of small quantities of alternating copolymers of ethylene and maleic anhydride and specific property improvements for applications in injection molded compounds. The resulting compounds have performance that can match or exceed prime virgin nylon at 30-50% cost savings. This current paper will cover the unique chemistry of alternating copolymers of ethylene and maleic anhydride to provide several advantages for upgrading prime or virgin nylon. For example, this paper will cover results of increasing relative viscosity and the advantages that brings to various applications. Another set of results will cover the unique improvements obtained in impact-modified nylon-6 and nylon-6,6 by reducing the negative impact of traditional impact modifiers by offering synergistic set of properties.
Important Factors Impacting the Performance of Polyolefin Pipes
The use of polyolefins in pipe applications has global acceptance. As such, polyolefin based pipes are expected to maintain their properties over an extremely long service life where the polymer must withstand climatic, extractive and mechanical forces. The success of polyolefin pipes has been enabled by the development of suitable resins with a defined molecular architecture plus stabilization systems which have enabled the protection of the polymer during both melt processing and the end use application. Through the proper development of the stabilizer systems for this challenging application it is possible to protect the polymer and also extend the service life of the pipe under various environmental factors.
Detection of the Brill Transition to Elucidate Localized Thermal History in Nylon 6/6 Injection Molded Samples
The semi-crystalline microstructure of nylon 6/6 is directly related to the shear and thermal history of the material. Injection molding freezes in a set microstructure distribution through the thickness of a quenched sample. The relationship between the amorphous and crystalline domains in nylon 6/6 injection molded samples was explored using DMA, Flash DSC and FTIR analysis. The rate of injection during molding was shown to have the most significant effect on final microstructure distribution through the part thickness. Areas within the test geometries were analyzed to determine if the microstructure had formed at conditions above or below the Brill transition temperature, providing insight to the condition of localized polymer melt just prior to quenching.
Recent Advances in Glass Bubble Polymer Compounds
Glass Bubbles (Hollow Glass Microspheres), due to their unique spherical geometry and low density, provide several benefits in thermoplastic composites. They help produce lighter weight parts in order to achieve stringent fuel economy targets for automotive and aerospace manufacturers. They also provide productivity benefits through shorter cooling times, enhanced dimensional stability and less warpage – helping to reduce waste and improve throughput. In this paper, we provide solutions to achieve high impact strength in glass bubble polyolefin composites through the combination of impact modifiers and compatibilizers as well as demonstrate how GBs can be combined with supercritical foaming technology to achieve double digit weight savings with well maintained properties primarily for glass fiber filled composites.
Development of Chaotic Mixing System for MWCNT/Polymer Nanocomposites
The aim of this study was the development of a novel chaotic mixing system utilizing two cylinder rotors rotating in a sinusoidal fashion to uniformly mix multi-walled carbon nanotubes (MWCNTs) with a polymer matrix. To investigate the influences of important mixing parameters and optimize the mixing conditions, four major parameters were selected; and, MWCNTs were mixed with polystyrene to fabricate nanocomposites. Electromagnetic interference shielding effectiveness (EMI SE) and electrical conductivity results of the chaotic mixed nanocomposites suggest that the chaotic mixer has a higher potential for mixing nano particulates into thermoplastics, compared to other types of melt mixing techniques.
Chemical Foaming Agents for Gap Bridging in Contour Laser Transmission Welding
The use of chemical blowing agents (CBA) as a means of bridging gaps in contour laser transmission (LTW) welding was investigated in this study. 5% 5 Phenyl Tetrazole CBA was mixed with low density polyethylene (PE) containing 0.05% carbon black (CB). The CBA-containing PE compound was able to bridge 5-10% larger gaps at a given laser power than PE without CBA. In addition, a tool for assessing CBA degradation during LTW was developed. It involved developing a kinetic model for CBA degradation using thermal gravimetric analysis (TGA) and determining the temperature-time history during LTW using a finite element method (FEM) simulation. The kinetic model and thermal history were then combined to yield the CBA degradation as a function of time and position in the assembly.
Effect of Photo-Oxidative Degradation on Environment Stress Cracking Behavior of Polycarbonate
The combined effect of two major causes of polymer failure, photo-oxidative degradation and environment stress cracking (ESC), have been investigated in this paper. Polycarbonate (PC) injection molded specimens were aged for 168 hours at 50 °C in an ultraviolet (UV) weatherable chamber. Then the stress relaxation and tensile tests were carried out in the ethanol environment to examine ESC behavior of PC. The results show that the tensile yield stress and stress relaxation resistance of PC improve slightly due to photo-oxidative degradation, while the ethanol will accelerate the failure of undegraded PC. When the previous degraded specimens were tested under the presence of ethanol, the stress relaxation rate increases significantly and the surface cracks appear to be more intensive in comparison with other ones. This indicates that there is a synergistic effect between photooxidative degradation and environmental stress cracking for PC injection molded parts.
Investigation of Blending Methods and Phase Morphology of Poly (Lactic Acid)/ Polystyrene Blends
Biodegradable poly(lactic acid) (PLA) blend with other materials is widely demanded as an effective approach for preparation of porous materials. In the present wok, two phases blends of PLA and polystyrene (PS) were prepared by twin-screw extruder and Torque Rheometer. For the latter blending method, the effects of various conditions such as blends mass and the temperature of mixing chamber on phase morphology were explored. A bimodal distribution of porous structure was presented after extracting the PS phase from the samples prepared by two different blending methods. Different with Torque Rheometer, the blends of twinscrew extruder rarely appears reunion phenomenon; therefore, a better phase morphology can be expected. It further found that the phase morphology of blends was apparently optimized under proper post annealing conditions.
High Flow Polycarbonate Copolymers for Medical Applications
High-flow polycarbonate (PC) copolymer derived from bisphenol-A (BPA) and a specific biosourced monomer derived from castor bean oil for medical applications available in two melt flow ranges is reported. This copolymer belongs to the class of Lexan™ HFD resins known for their improved melt flow and ductility balance compared to standard polycarbonate yet with similar high optical clarity and light transmission properties. These high-flow HFD copolymers for the healthcare industry are designed to have all attributes of the Lexan™ HFD resins such as lower temperature processing capability, longer injection molding flow lengths and improved low temperature ductility versus a standard polycarbonate and ISO10993 biocompatibility. The superior flow enables molding of thinner parts with similar practical impact to standard healthcare PC.
Maximization of Hydraulic Flow in Small Flexible Polymer Tubing by Stiffness and Wall Thickness Optimization Utilizing Hardness and Glass & Carbon Nano Tubes Fillers
As medical infusion treatments become increasingly more common in the United States and across the globe, the need for better and faster fluid delivery is greater than ever. The use of advancements in polymer and polymer composites structures will provide for medical products that have increased fluid flow while maintaining required outer dimensional sizing, adequate tubing stiffness, and tubing burst resistance characteristics compared to the currently used medical tubing materials. Tubing structures of current medical tubing proprietary polyurethane structure with glass bead filler of 4% by weight (structure A), with carbon nano tube filler of 1% by weight (structure B) and a polyurethane structure with 10% increased shore durometer without fillers (structure C) were tested per ISO 10555-1 for tubing d tensile strength, stiffness, flexural fatigue resistance, vacuum lumen collapse resistance and hydraulic burst resistance. With variations of each structure having outer wall thickness of 0.010”, 0.015” and 0.020”. Structure C tubing with increased shore hardness with wall thickness of 0.020” passed all minimum requirements per ISO 10555-1. Structure C exhibited a tensile strength 13.4% less than the control group however was 52.7% stiffer and did not sustain any noticeable wear or defects during flexural fatigue testing. Structure C demonstrated tensile strengths on average 14.8% less that the control group at post flex fatigue tensile testing but showed no failures at 150 psi burst testing when applied to it for 5 seconds. Structure C with the 0.020” wall thickness is estimated to have a 43% higher flow rate capacity than the current material. Thus providing for a significantly higher rate of infusion treatment.
An Investigation of Melting and Metering Sections in a Single-Screw Extruder
For an ABS resin, a three-dimensional finite element simulation of melting and flow in the melting and metering sections of a single-screw extruder was performed using barrel rotation boundary conditions. In the simulations, the flow domain was modeled as a full three-dimensional helical channel with flight clearance. The simulation results were then compared with the corresponding results from the screw-freezing experiment. Maddock melting mechanism was observed both in experimental results and numerical predictions. However, some discrepancies existed between the numerical predictions and experimental results, which are further discussed in the paper. These discrepancies may be clarified with simulations using screw rotation boundary conditions.
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