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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Modification of Epoxies for Low Friction
The morphology, elastic modulus, and friction properties of a commercial epoxy resin + fluorinated poly(aryl ether ketone) (12F-PEK) system have been studied. The system was cured at 24°C and 70°C. We achieved significant friction lowering, namely 30% less than the value for plain epoxy, at the 12F-PEK concentration of only 10% after curing at 24°C. By contrast, after curing at 70°C, an increase in both static and dynamic friction is observed.
Correlating Creep Data with High Temperature Tensile Testing
Obtaining accurate creep data can be time consuming when the material supplier does not publish it. A faster method of predicting creep behavior could be a benefit when designing plastic products that will encounter long term loading. This experimental study will examine the feasibility of using elevated temperature tensile testing data as a means for predicting the tensile creep behavior of general-purpose acrylonitrile-butadiene-styrene (ABS). Injection molded specimens will undergo tensile testing at elevated temperatures for comparison to the respective tensile creep curves.
The Shelf Life of Filled Polymeric Material for Medical Device: Accelerated Thermal Aging Experiment and Kinetic Prediction
In the present study, a kinetic method is suggested to determine the shelf life of a filled polymer material prepared for making medical device, including barium sulfate-filled polyethylene and poly(ether block amide), by using an well-designed accelerated thermal aging experiment. Accordingly, the effects of aging time and elevated temperature on mechanical performance of the material are mathematically defined by thermal aging index, namely the ratio of the elongation-at-break after to that before a period of thermal aging. A general m-order rate kinetics with Arrhenius-type temperature dependence is utilized to describe the deterioration of the mechanical properties during aging. An accelerated thermal aging experiment is performed to statistically measure various aging indices for the samples aged at various elevated temperatures within different short-term aging times. Kinetic parameters are acquired using nonlinear regression to the experiment. By assigning a permissible aging index, the shelf life of the material (or medical device) is kinetically predicted at storage temperature.
Robust Simulation for the Heating Stage in Thermoforming
Process simulation traditionally relies on the exact knowledge of parameter inputs, such as material properties, process conditions and heat transfer properties. However, these parameters are never known exactly and a degree of uncertainty exists. This level of uncertainty affects the confidence in the results obtained. One therefore has two options, reduce the level of uncertainty or account for it in the simulation through appropriate sensitivity trials. This work reduces the level of uncertainty through accurate evaluation of the input parameters. Accordingly, the accuracy of the predictions is significantly improved.
Thermomechanical Modelling, Microstructure Development and Part Performance in Stretch Blow Moulding
Blow moulding simulation can be used as a predictive tool for determining the bottle performance as a function of the stretch blow moulding operating conditions. Modelling the successive processing steps is necessary in order to obtain the final bottle geometry and the distribution of polymer microstructure. The container properties are then used to estimate top load resistance. The objective of this work is to integrate microstructure models in process simulation in order to better estimate part performance in service. The models are evaluated for the prediction of top load resistance of PET containers. Experimental validations of the integrated process and performance models were conducted for the one-stage injection stretch blow moulding process.
On the Effects of Migration of Filler Particles on Conductivity and Mechanical Properties
Shear-induced migration of filler particles during molding and extrusion of filled polymer compounds of polypropylene and glass beads and conductive carbon particles was investigated. The high-shear flow conditions were generated in capillary rheometers with length to diameter ratio of 20 and 30 and in injection molding machine. Reduction of both surface and volume conductivities of injection molded samples was observed, especially in the cases of conductive compounds with conductive particle composition in the range of percolation volume fraction. Significant migration of glass beads was observed from the surface to the interior in blends with PP. Maleic anhydride grafted polypropylene (PP-g-MAH), used to promote binding with filler particles, reduced the extent of migration of glass beads, but improvement in conductivity of injection molded samples was not observed.
Are Fundamental Mechanistic Studies Useful? A Novel Study in the Thermal Degradation of PET during its Manufacture and Processing Will Be Discussed to Illustrate the Importance of Mechanistic Studies
PET polyesters for food packaging comprise one of the fastest growing polymer markets in the world. One of the biggest challenges in the PET industrial R&D sector for the past twenty years has been to find the means to reduce the amount of acetaldehyde (a PET polyester's degradation by-product) generated during PET production and processing. A novel approach for studying the mechanism of thermal degradation of PET polyesters and copolyesters is described in this study, which also suggests precisely the ways to significantly reduce the acetaldehyde content in these polyesters. In this study, the amount of acetaldehyde evolved was measured over time at an elevated constant temperature. We found that there was a gradual decrease in the amount of acetaldehyde generated with time, and that this decline eventually approached a near asymptotic value. A degradation mechanism was proposed which showed that acetaldehyde was generated by three different routes involving, first, the hydroxyl end-groups, second, the vinyl end-groups and finally, the mid-polymer chain-scission. It was further suggested that of these, the hydroxyl and the vinyl end-group based acetaldehyde generation routes depleted with time leaving behind the last, but inexhaustible, chain-scission route. From the data in this study, it was also possible to estimate the rate of acetaldehyde generation by this mid-polymer chain-scission route. This information was then applied together with the (a) amount of residual acetaldehyde in the resin, (b) HO-end group concentration and (c) vinyl- end group concentration, to calculate the amount of acetaldehyde generation possible over a given period of time. This calculated [acetaldehyde] compared very well with the actual observed [acetaldehyde] over the same period of time, thereby validating the proposed mechanisms. In agreement with the thermodynamic principles, a near doubling of the chain-scission acetaldehyde generation rate was also observed when the temperature
Methods for Polystyrene Bead and Polyol Isocyanate Duck Decoys
The use of Polystyrene has been greatly increased since its introduction by the Koppers Chemical Company in the 1940's. Due to this rise in the use of Polystyrene many new and easier ways of production have been conjured. Some of these processes work better than others considering the exact heat that is needed to properly expand the beads to their full capacity. This paper will address issues on how molding conditions, mixture ratios, and mold quality will affect the molding characteristics and outcome of Polystyrene beads and Polyol Isocyanate products. The products in this paper will be duck decoys.
Surface Modification of Polymer via Surface-Induced Migration of Copolymer Additives
Surface-induced migration of low surface tension block copolymer additives, polystyrene-b-polydimethylsiloxane (PS-b-PDMS) and high surface energy copolymer additives, polystyrene-b-polymethylmethacrylate (PS-b-PMMA) in a polystyrene (PS) host was investigated using a series of matrix PS molecular weight (Mw). Dynamic Contact Angle analysis and Attenuated Total Reflection Fourier Transform Infrared spectroscopy measurements were used to characterize surface properties of polymer/additive blends created by solvent casting, precipitation, and melt annealing processes. For all matrix Mw, selective DMS enrichment of the air/polymer interface was observed due to the strong surface energy difference between additives and matrix. The surface excess concentration of DMS group, ??DMS was also found to depend on host polymer Mw and annealing conditions: ??DMS ~ Mw,PS?, where the scaling exponent a is a function annealing conditions. Whereas entropic-driven surface migrations were observed in PS-b-PMMA/ PS blends. The diffusion of PS-b-PMMA in PS matrix was found to depend on matrix molecular weight even though much high Mw, which is not consistent with reptation theory in molecularly homogeneous linear blends. And also for high molecular weight PS, thermodynamic driving force is revealed to compete with diffusion rate of additives. These findings could be discussed in terms of the matrix Mw dependence of diffusivity, surface tension and configurational entropy of host polymer.
Kinematics of Quasistatic Inflation of a Catheter Balloon Made of Elastomeric Material: Simulation and Experiment
Based upon a nonlinear membrane theory, a theoretical model is proposed for simulating a quasistatic deformation process of a catheter balloon made of an elastomeric material and inflated by the internal pressure acting across the membrane of the balloon. A Lagrangian approach is utilized to describe a material particle's motion during inflation. The deformation field and the system of governing equations are determined in terms of the principal stretches and the Cauchy stresses. With ~, incorporation of the constitutive laws of hyperelasticity and a set of proper boundary conditions, the numerical scheme for calculating the deformation-loading relationship of the balloon under quasistatic equilibrium condition is developed. The inflation experiments are conducted under the assumed quasistatic condition for various angiographic catheter balloons of different designs. Intermediate inflated geometries and inflating pressures at various inflating volumes are measured and compared with the predictions. It is found that the theoretical model can reliably predict the short-term kinematic behavior of balloon inflation. In addition, the effects of various balloon design parameters on the kinematics of inflation are evaluated.
High Performance Decoration with Polyamide Films
Over the last decades a large number of new surface decoration and protection processes have been developed using polymer films instead of coatings. Films of polyamide 12 and polyamide 12 elastomers offer the best combination of transparency, mechanical properties, and chemical resistance. Highest quality diffusion printing techniques are applied to create brilliant decorations on i. e. sports articles like snowboards, skis, tennis rackets, or for demanding automotive applications. Most recently two-layered so called lacquer films with brilliant metallic or other effect fillers were introduced into the market to replace conventional multi-step coatings. In the paper we will present mono- and multi-layer structures of decorative and protective polyamide films. Printing and processing techniques will be discussed showing various applications.
Structure of Propylene/1-Pentene Random Copolymers
Propylene/1-pentene copolymers were prepared, characterized and reported previously. [1-6]. This new family of copolymers form ?-modification during isothermal crystallization. Upon deformation significant changes take place in the crystalline structure of the material. Two extensional deformation methods, (thermoforming and cold stretching) were used and the thermal and crystalline properties of both the deformed and undeformed samples were determined by DSC and WAXD. Thermoforming has no effect on the thermal and crystalline properties of the material. On the other hand, cold stretching changes the crystalline structure of the material. Upon extension, the degree of ?-modification decreased with a corresponding increase in the degree of ?-modification.
The Effects of Directional Molecular Orientation on Tensile Stress and Elongation of Polypropylene Film
Highly oriented polymer dogbone samples were tensile tested at different angles to the machine direction to determine how tensile stress at yield and the percent elongation at yield is affected by the alignment of molecules. Theoretically, as the angle from machine direction increases, the tensile strength at yield will decrease. It is also expected that as the angle from machine direction increases, the strain will decrease. These effects are important in determining how the same material can have different mechanical properties.
Heat Transfer in Foam Plastics
Predicting insulating values in foam plastics have been difficult because of variations in process, variations in geometry, and general lack of understanding in heat transfer. With this research, an attempt will be made to develop a systematic method of characterizing foam injection molded parts so that the parts can be designed to withstand thermal-mechanical loads that they would not be able to survive in normal operating conditions. Finite element analysis techniques will be used to help map actual heat transfer results. These results will then be compared to those measured through heat transfer experiments.
Optimization of the Pultrusion Process Using Thermodynamic Analysis
In the pultrusion process, line speed is the primary measurement for process optimization. With the process being continuous, the fastest speed with no defects is seen as the production goal. Before optimal line speed can be determined, the amount of time required for commencement of the reaction must be obtained. Performing a thermodynamic analysis of the die is the first step in achieving this goal. Creating a computer simulation of this process using the results of the thermodynamic analysis is the objective of this research.
In Situ Observation of Fracturing Behavior of Polyethylenes by Transmission Electron Microscopy
In situ observation of deformation and fracturing process of polyethylenes was carried out using a transmission electron microscope (TEM). It was found that there are three kinds of fracturing behavior concerning polyethylenes. In case of linear polyethylenes, two kinds of fracturing behavior caused by Crazing" and "Elongation" were observed. On the other hand low-density polyethylenes (LDPEs) having long-chain branches (LCBs) were fractured dominantly by "Interfacial splitting" of spherulites. These results show that the molecular structure of polyethylenes effects the deformation and fracturing behavior."
The Effect of Wall Slip on the Performance of Flat Extrusion Dies
Flat extrusion dies are commonly used in a wide variety of film, sheet and coating applications. Although flat dies can be designed to produce an exit flow distribution that is very uniform across most of the width, there will usually be a region along each side where it drops gradually to zero. This often requires trimming the edges of the film or sheet downstream in order to meet product specifications. It is commonly believed that treating the land area of the die with coatings that promote a small amount wall slip will reduce the size of this edge effect and therefore improve die performance. This analysis shows that slip over the entire land region of the die will adversely affect die performance. Better performance is possible but only if the sides of the land are treated.
FFT - An Efficient Process Analytical Tool for Plastics Film and Sheet Processes
Every Plastics Film and Sheet Processor, whether using Calendering, Extrusion or Coating process, strives to manufacture the best quality product with minimal variations. The total variations in a product comprise of Cross Direction (CD) and Machine Direction (MD) variations. The Machine Direction variations can be further broken down into controllable Long-Term drift and uncontrolled Short-Term high frequency variations. Gauging Systems have been available in the Marketplace for quite a few years, which efficiently control the Profile (CD) and Long Term Machine Direction (LTMD) variations. This paper illustrates the capability of Gauging Systems that incorporate Fast Fourier Transform (FFT) feature to provide the plastics film & sheet processors with a timely and detailed analysis of the uncontrolled high frequency variations (Short Term Machine Direction (STMD) and the causes thereof. This efficient process analytical tool enables the processor to take timely action to reduce STMD, thus improving the overall product quality. The economic benefits to the plastics film & sheet processors derived from down-gauging, while meeting the specifications for end-use applications of the product can be substantial. This paper presents a case study of FFT application to a vinyl calendering process.
Optical Haze Properties of Polyethylene Blown Films: Part 1-Surface Versus Bulk Structural Considerations
In this paper we report on some recent findings regarding the factors affecting the optical (haze) properties of polyethylene (PE) blown films. The large majority of the contribution to the total haze in these blown films was a result of the surface roughness of the films, with the bulk (internal) contribution being relatively minor. Using several characterization techniques, we found, rather unexpectedly, that the surface roughness in some of these films was a result of the development of distinct spherulitic-like" superstructures formed during the blown film processing. Analysis of the rheological and molecular characteristics led us to conclude that in blown films of LLDPE-type resins the optical haze properties are adversely affected due to enhanced surface roughness caused by the formation of "spherulitic-like" superstructures in polymer melts that possess fast relaxing and low melt elasticity rheological characteristics."
Optical Haze Properties of Polyethylene Blown Films: Part 2-The Origins of Various Surface Roughness Mechanisms
In continuation of our associated report here (see Part 1, ANTEC 2001), we have now found that high haze in PE blown films can be caused by very different surface roughness mechanisms having unique origins. The total haze % exhibits a complex parabolic relationship with the logarithm of the recoverable shear strain parameter, ??. At low ??, spherulitic superstructures are formed. As ?? increases, an oriented, row-nucleated stacked lamella texture is developed. However, at even higher ??, fine-scale surface roughness due to high melt elastic instabilities is induced. We believe that this is the first time that both very low and very high melt elasticity have been shown as primary causative factors in yielding high haze in PE blown films, albeit for fundamentally very different reasons.
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