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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Capillary Coextrusion: A New Process for Creating Small-Scale Coextruded Films
Coextrusion is an important method for making barrier and optical products at large scale. In these multilayer polymer films, adhesion is critical for performance, yet is difficult to predict by small scale experiments. Past work has shown vast differences between bilayers produced in coextrusion (continuous process) versus lamination (batch, quiescent process). In this work, a small scale coextruder die is designed and attached to a dual-bore capillary rheometer. Model films are quickly produced for adhesion testing, with adhesion showing a strong dependence on residence time.
Mastering Plasma & Flame Surface Treating Technologies to Improve Adhesion
In-line surface treatment technologies are used in the plastics industry to clean, micro-etch and functionalize surfaces to promote adhesion, improve quality and increase productivity. For some applications surface treatment is a requirement for adhesion success, for others it eliminates the need for expensive & specialty coating formulations, and in all cases it provides a safeguard against materials which may exhibit inconsistent surface energy. Examples are found in the automotive, medical, decorating, marking, assembly, film extruding & converting, folding carton, pipe, cable and other markets where surfaces need assistance in bonding with coatings. This paper will share laboratory trial data on the impact of surface treatment on a variety of materials with results measured in dyne level, polarity and surface free energy. It also addresses adhesion basics, how to select the right technology for your application, and how to implement blown arc air plasma, blown ion air plasma, variable chemistry plasma and high velocity flame plasma treaters for optimum results.
Ionomers as Smart Vapor Barriers for Building Applications
A “smart vapor barrier” is a material whose moisture vapor permeance changes as a function of relative humidity, preferably with the permeance increasing with increasing relative humidity. Sodium ionomers are capable of behaving as smart vapor barriers at suitably high extents of neutralization. This unique property is accentuated even further when the sodium ionomers are modified with fatty acid salts. The smart vapor barrier properties of the ionomers compare favorably to commercially-available polyamide film used for this application (as measured by ASTM E96 Procedure A and B testing). Modified permeance testing at extremely high relative humidities indicates that the permeability advantage of ionomer films over the commercially-available polyamide film is extended even further, which is desired for this application.
Fabrication of Interconnected Porous Poly(Lactic Acid) Scaffolds Based on Dynamic Elongational Flow Procedure, Batch Foaming and Particulate Leaching
This study reports a highly porous interconnected poly(lactic acid) (PLA) scaffold fabrication method, which utilized self-developed vane extruder melt blending followed by supercritical carbon dioxide (Sc-CO2) foaming and particulate leaching. PLA as polymer matrix was blended with polyvinyl alcohol (PVA) and NaCl particles via vane extruder, which generates global dynamic elongational flow. Then, the prepared blends were foamed by Sc-CO2 followed by leaching the porogens. It was found that most NaCl particles could preserve their original size after vane extruder blending and the macropore density and size can be tuned by modifying the salt concentration and particle size. The scaffolds prepared using this approach could achieve a porosity up to 93% with well interconnected porous structure.
Modeling of the Fiber Orientation in Polymer/Fiber Composite Foams
The electrical conductivity of conductive fiber/polymer composites is highly affected by the alignment of the fibers, as well as the fiber-to-fiber distance and contacts. While the formation and growth of gaseous cells result in the translational and rotational displacement of the fibers in foamed conductive polymer composites, the mechanism of the cell/fiber interaction and the effective parameters on the fiber movement is not fully understood. In this research, we propose a geometrical model to predict the behavior of carbon fibers at close vicinity of a growing cell. The predicted results were then validated using experimental data, obtained from the foam injection molding of polystyrene/carbon fiber composites. The model predictions were in good agreement with the experimental observation. The parametric analysis using the model revealed that cell size, and cell-fiber distance greatly influenced the rotational displacements of the fibers around the growing cells. It was also found that the cell growth induces a nonuniform degree of re-orientation on the fibers in its vicinity.
Study on high-performance of WPC
The global environment problem is a very serious problem, especially the global warming issue. In order to prevent this phenomenon continues to deteriorate, WPC (wood plastic composite) can be used as a new kind of composite to solve this problem. However, as an industrial high-quality material, WPC still has a lot of problems at present. For example, WPC material has poor toughness and low izod impact strength. Based on the above two problems, in this study, a lot of research and some new technologies are used to improve the performance of WPC. In order to improve the toughness of WPC, we use wood particles having different lengths to make WPC, through tensile test, it is shows that the shorter length of the particles will lead the better toughness of WPC. On the other hand, surface modification technology is also used as a way to changing the WPC’s toughness. For improving impact strength of WPC, we mix microparticle and dispersant of wood with WPC. For high tensile modulus of WPC, we make the shape of wood likes fiber. Finally, conductivity and incombustibility of WPC have been evaluated in this research.
The Importance of Inflow Conditions on the Simulation of Extrusion of Thermally Sensitve Material
Simulating flow through the simplest components for use in extrusion still requires accurately representing the inflow conditions of that particular component. Due to the many different stages a polymer experiences through the extrusion process, capturing proper inflow conditions still remains a challenge. The goal of this study was to demonstrate the importance of proper setup of inflow conditions and material parameters to detect problematic regions for thermally sensitive materials within a simple symmetric adapter flow channel. The studied showed mimicking the outflow of material from the screws in a counter rotating twin screw extruder is the most significant factor to accomplishing this task. This work used an imbalanced inflow and a helical inflow condition to predict high residence time regions. These factors must be considered carefully when simulating any part of the extrusion process.
Preparation of PPC/PS/PTFE Composites with in-Situ Fibrillated PTFE Nanofibrillar Network and Their Supercritical Carbon Dioxide Extrusion Foaming Properties
In this work, polystyrene (PS) and polytetrafluoroethylene (PTFE) were compounded with poly(propylene carbonate) (PPC) via a triple-screw extruder to prepare multiphase composites that possess special properties and to improve the extrusion foaming ability of PPC. It was found that PS was immiscible with PPC and formed dispersion phase, and PTFE were in-situ fibrillated into nanofibrillar network within PPC/PS matrix. The introduction of rigid PS domains and PTFE nanofibrils showed remarkable effects on the properties of PPC. Compared with neat PPC, PPC/PS/PTFE composites had 1576% higher initial viscosity. Moreover, the physical network formed by PTFE nanofibrils effectively prevented the shear-thinning behavior of the polymer matrix. Significant influence of PTFE on the cell morphology was found in the extrusion foaming process. The cell density of PPC/PS/PTFE foams was four orders of magnitude higher than PPC foams.
Effects of Small Range Color (Pigment) Concentration Levels on Plastic Injection Molded Parts
Color (pigment) concentration levels play a great role in changing the mechanical properties of an injection molded part. Higher concentration levels result in failure during the use of the parts . A general rule of thumb for concentration levels are between 3 to 5% or 5 to 10% is being used across different industries to achieve the required color. The above concentration levels are considered as small range in this manuscript. It is observed during the tensile test conducted on injection molded plastic parts that the small range of concentration levels has an impact on a few mechanical properties including strain at yield and strain at failure. There is no impact on tensile strength, Young's modulus and Poisson's ratio. Hence Product Designers need to assess the impact of these small concentration levels with respect to the base resin and need to specify the acceptable concentration levels in their product drawings or in product specification documents. It is equally important for the molders to verify these concentration levels during molding process.
An Investigation of Real-Time Monitoring of Shear Induced Cavity Filling Imbalances during Polymer Injection Molding
Since the beginning of injection molding industry development, multi-cavity molding has been widely utilized to increase manufacturing efficiency, save time and reduce costs. As a result, geometrically balanced mold cavities and runner systems have become industry standards for injection molding. Some seemingly balanced designs, however, still provide imbalanced cavity filling results. The reason for the imbalanced filling is due to the shearing between the lamellae of the molten polymer as it is injected through the runner system and into the mold cavities. The current investigation includes visual studies of how the shearing of the polymer through the runner systems affects the mold filling in real time. In order to develop a deeper understanding of the shear induced imbalances in injection molding, a custom built mold incorporating transparent mold inserts and runner systems was used. Polymers were injection molded into different types of cavities and the cavity filling was documented in real time via a high-speed camera. With this study, there is a potential to find and/or verify methods to mitigate the non-uniform behavior of molten polymers undergoing shear thinning or shear heating, especially since the imbalances have the potential to alter properties of the finished products.
Dynamic Solubility of Carbon Dioxide in Polypropylene Melt
A testing method has been developed to measure the dynamic solubility of polymer/gas mixtures at high pressures and a wide range of melt temperatures. This method utilizes tandem extruders equipped with a highpressure optical slit cell; a camera; a set of pressure transducers; and a metering valve for back-pressure control. This in-line visualization system provides a direct way to investigate the dynamic solubility within a wide range of processing conditions (i.e, melt pressure, melt temperature, gas content, and flow rate). The measurements were carried out for various amounts of CO2 dissolved into branched polypropylene (PP) melt at two different temperatures. The dynamic solubility was estimated based on the degassing pressure when the second phase starts to nucleate. The experimental results showed that the dynamic solubility of carbon dioxide in PP melt increased with system pressure but decreased with melt temperature. It was also found that a higher flow rate, which corresponds to a higher shear rate, decreased the dynamic solubility of CO2 in branched PP.
Measuring the Interlayer Fracture Resistance of FDM Printed Thermoplastics
With increasing structural and functional applications of 3D printed materials, their mechanical performance is highly demanded. So far, stress- and strain-based experiments have been used to characterize the mechanical properties of fused deposition modeled (FDM) samples. In this work, a fracture-mechanics-based methodology was developed to characterize the interlayer adhesion of FDM 3D printed materials. Double cantilever beam (DCB) specimens were designed and printed with a precrack set at the interface of the layers. The DCB samples were tested in mode I loading and the load displacement curves were obtained. Critical stress intensity factor was found using the DCB loading data coupled with a finite element model. The critical strain energy release rate, Gc was also calculated using the finite element model data and the elastic properties, obtained by the tensile test of FDM 3D printed samples. The results of this work demonstrates a methodology that can be implemented to measure the interlayer fracture resistance of FDM printed materials.
Improving the Impact Properties of PLA by Incorporation of PHA, TPU and Carbon Nanofibers
In this study, PLA composites/blends were fabricated with carbon nanofibers, TPU and PHA through twin screw extrusion processing following by hot-press compression molding. Impact tests were performed to evaluate the energy absorption and momentum transfer during impact. Neat PLA, PLA with 15 wt% carbon nanofibers, 15wt% PHA and 15wt% TPU composites/blends were fabricated for instrumented drop weight impact testing. SEM morphology revealed that carbon nanofibers are well dispersed but weak matrix filler interface is indicated as much fiber pull-out was observed on the micrographs of the impact fractured morphology. The results indicated that PLA15CNF is less tough than neat PLA. Both PLA15TPU and PLA15PHA were found to be tougher than neat PLA.
The Flameretardancy Study of The Cardboard Bed Made from Corrugated Cardboard
Recently corrugated cardboard is utilized for not only packing materials but also furniture and beds at shelters in Japan. The reason why the cardboard has the characteristics of lightness, high strength, cheapness and recycle ability. Therefore, there is the strong needs to add flameretardancy for cardboard beds in medical facilities for prevention of second disaster. The purpose on this study is to add flameretardancy to the cardboards with keeping the recycle ability. In this paper, the cardboard of combusting behavior was measured by using a calorimeter under the UL-94 standard. So far we have used 6 kinds of flameretardant include 3 kinds of commercial flameretardant. As a result ammonium sulfate has given superior flameretardancy to cardboards. However we considered that it has no practical use, because flameretardancy of cardboards must be safety from chemical toxicity. Therefore we selected 2 kinds of flameretardant. As a result a flameretardant which contain phosphorus and nitrogen gave great flameretardancy to cardboards with small quantity.
The Role of Additives and Free Volume on the Gas Barrier Properties of PET
Additives such as low molecular weight diluents (LMWD) can be added at low concentration to poly (ethylene terephthalate) (PET) to improve barrier properties significantly. Orientation during PET processing, on the other hand, causes strain induced crystallization which can increase the diffusion pathway and lessen the amorphous chain mobility. The objective of this work is to analyze the effect of LMWD additives, such as dimethyl terephthalate (DMT) and orientation on the free volume and thermal properties of PET and correlate this with barrier properties. Films made of pure PET and PET/DMT using single screw extruder were oriented using Long Extensional Tester at a relatively fast rate of 200%/s (4 in/s) to prevent any relaxations in the rubbery stage . TGA and FTIR were used to quantify the concentration of DMT in the PET matrix. Permeation measurements were conducted using gases with different sizes (O2, CO2, CH4, N2, and He). Dynamic Mechanical Analysis (DMA) experiment was used to study long/short range chain motions. Besides, Differential Scanning Calorimetry (DSC) was used to study the thermal properties and crystallinity. Transport studies demonstrated lower permeability for both oriented PET and PET/DMT, with the barrier impact factors (BIF) of about 2 and 1.3 for all the gases, respectively. The dynamic mechanical property studies in the ? relaxation region explains this behavior, showing more restriction in the chain motion in case of oriented PET and PET/DMT compared to pure PET. Furthermore, calculating fractional free volume using WLF equation offered lower values for oriented PET and PET/DMT compared to pure PET.
Viscoelastic Shear Analysis of Polymeric Foam Midsoles
Athletic footwear companies continually create technological innovations to give the athlete a greater running experience. The nonlinear viscoelastic material behavior of polymer foams, found in the shoe midsole, dissipate the ground reaction forces to provide cushioning. Shear analysis up to 50% strain was experimentally conducted at 1 Hz and 5 Hz to characterize the stressstrain performance. Constitutive equations were curve fitted by using Finite Element Analysis performed in ANSYS. A look at footwear industry trends demonstrated the potential for highly cushioned and linear foams to support natural gait movement.
Mechanical Crystallization Properties and Foaming Behavior of Teflon-Reinforced Poly(Lactic Acid) Composites
In this study, poly(lactic acid) (PLA)/polytetrafluoroethylene (PTFE) composites containing different amounts of PTFE were prepared by melt blending. Multiple properties of the prepared composites were investigated including mechanical, crystallization, and foaming properties. Tensile test results indicated that the mechanical properties of the composite with PTFE showed significant reinforcement and toughening effects. The average elongation-at-break of the composite increased by 72% compared to pure PLA. Scanning electron microscopy (SEM) showed that the PTFE elongated into fibrils during blending and formed a physical network of entanglements in the melt. Differential scanning calorimetry (DSC) showed that PTFE had a significant nucleation effect and greatly increased the crystallinity of the PLA matrix. The injection molding foaming experiments revealed that adding 1 wt% PTFE had the most notable heterogeneous nucleation effect, with the cell size decreasing from 81.46 ?m for neat PLA to 25.2 ?m and the cell density increasing from 1.34×108 cells/cm3 to 2.53×109 cells/cm3.
Development of PLA/Cellulosic Fibre Composite Foams Using Injection Molding: Foaming and Mechanical Properties
Poly(lactic acid) (PLA) and northern bleached softwood kraft (NBSK) or black spruce medium density fiberboard (MDF) fibers were melt compounded using a co-rotating twin screw extruder and subsequently microcellular injection molded. The microcellular structure and mechanical properties were investigated. Compared to PLA/PEG, a finer and more uniform cell structure was achieved in the cellulosic fiber composite foams. After foaming, the specific flexural strength and modulus and impact strength of the PLA foams were comparable or higher than these of the solid counterparts. PLA/NBSK/PEG composites had better mechanical properties than PLA/MDF/PEG composites.
Predicting Mooney Viscosity from Online Rheology Measurements
Mooney viscosity is a key specification item for process and quality control for EPDM rubbers but can only be measured in a laboratory instrument. For early process upset detection and reduction of off-grade production, higher data frequency from continuous analysis would be beneficial. However, at this point in time available process analyzers do not deliver Mooney viscosity as a standard feature. In this study, a model was developed based on rheological principles to predict Mooney viscosity from viscosity curve information that can be measured using process rheometers.
The model is evaluated against dynamic mechanical spectroscopy (DMS) data for its general validity, and it was found that only slight adjustments were required to achieve a prediction error of only ±10%. However, prediction of Mooney viscosity from process rheometer data collected using a slit die was less accurate and required a correction factor (-16.6 to 4.8% prediction error).
Study of Ultrasonic Treatment on PP/CNT, PP/GNP and PP/CB Composites Using Continuous Ultrasonic Twin-Screw Extrusion
This study systematically investigated the efficiency of ultrasonic treatment on dispersion of different fillers in polypropylene (PP). PP/graphene nanoplatelets (GNP), PP/carbon nanotube (CNT) and PP/carbon black (CB) were prepared using twin screw extrusion without and with ultrasonic treatment. The ultrasonic power consumption varied with filler concentration exhibiting different trends in these composites: the power consumption increased with concentration for PP/GNP and decreased with concentration for PP/CNT, but for PP/CB, it only slightly increased at high concentration. The difference is related to the bubble concentration in the polymer composites. The efficiency of ultrasonic treatment was verified by rheological, electrical and morphological studies. The morphological study showed that CB exhibited the best dispersion in PP which is followed by CNT, whereas GNP showed the worst dispersion. However, the rheological and electrical percolation threshold from low to high was successively shown in PP/CNT, PP/CB and PP/GNP composites. For PP/CNT and PP/CB composites the storage modulus and complex viscosity at low frequency were increased by the ultrasonic treatment. However, PP/GNP did not show obvious change with ultrasonic treatment. The ultrasonically treated PP/1wt%CNT at an amplitude of 13 um dropped 8 order of magnitudes in electrical resistivity compared with the untreated sample, while PP/5wt%CB dropped 4 orders of magnitudes and PP/5wt%GNP only dropped 2 order of magnitudes. Morphological studies show that the agglomerates and agglomerates area ratio were decreased with ultrasonic treatment for PP/CNT and PP/CB composites, but not for PP/GNP composites. An ultrasonic mechanism is proposed based on the experimental data.
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