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.
Polymer blends are more and more important materials in polymer technology. Their role increases due to the recycling processes of mixed plastic waste. One of the key problems of polymer blends is the interaction between the components as they determine the properties. Commercial polycarbonate (PC) and ABS were blended in a dynamic melt mixer in 80/20 and 70/30 ratios. Homogeneity of the blends was characterized by SEM method. Glass transitions of the blends and the pure materials were measured by calorimetric and dynamic mechanical analysis. The interaction and the partial miscibility between the components were determined from the shift of the glass transition temperatures. It was found that the homogeneity of the blends was uniform. The shifts of the glass transition temperatures show some interaction between the components.
Melt strength of polyesters for foam extrusion and extrusion blow molding is controlled by weight-average molecular weight, molecular weight distribution, and the degree of branching. This paper describes the chemical modification of polyethylene terephthalate (PET) as a technique to improve its melt strength using compounds containing the reactive glycidyl (epoxy) group. The effect of addition of di-, tri-, and tetra- functional epoxy compounds to the PET resin in the melt state was studied using a batch mixer. Changes in the torque and temperature in the mixer resulting from the addition of modifier(s) were followed in order to relate to the kinetics of the reactions.
Grooved feed zones in single screw extruders have been used in many variations over the years, mostly axial grooves in many sizes and shapes. The lesser known helically grooved feed zone permits, when properly designed, an operating mode where flow rate becomes a function of geometry only, practically independent of friction coefficients. Therefore, it has a linear behaviour with screw speed and is virtually independent of backpressure over a wide operating range, as shown by experimental evidence gathered over many years. The high flow rates obtained require barrier screws for adequate melting capacity. In the barrier zone, considerable pressure differentials are observed between the primary and secondary channel, where the melting occurs, at higher screw speeds. This effect is associated to the melting mechanism.
Information storage devices such as re-writable DVD (DVDRW) disks require high degree of groove replication to achieve desired readability. Higher levels of replication are typically achieved by increasing mold temperature, packing pressure, and filling speed. These extreme molding conditions are often on the border of the material processing window. A simple groove forming process model is presented. The model is shown to predict well groove replication for wide ranges of mold and melt temperatures and two different radial locations. The model is useful in assessing replicability of new materials in new formats.
The forming of weldlines wherever polymer flow fronts meet is one of the problems that confound the overall success of injection molding technology. An L'18 experimental matrix design based on the Taguchi method was conducted to optimize the weldline strength of injection molded thermoplastics. Experiments were carried out on an 80 ton injection-molding machine. A plate cavity with an obstacle at the center was used to create a weldline. After molding, the weldline strength of the parts was measured by a tensile tester. For the factors selected in the main experiments, melt temperature and mold temperature were found to be the principal factors affecting the weldline property of injection molded thermoplastics. In addition, weldline strengths of injection molded parts increase with the size of the obstacles.
On-line rheometers have been around for over 30 years. They have been used in many different applications in R&D, polymerization processes, product development, and compounding. However, their main application has been in large volume resin production, mainly in the polyolefins industry. Applications in the processing and compounding industries have been almost non-existent because of the large size of the rheometers and the need to modify the extruders or compounders in order to use them. This paper discusses applications of a new rheometer, developed to address these problems, in the monitoring of a production PET sheet extrusion line. The real time" monitoring of viscosity and its application to the control of the resin moisture level and the consistency of a virgin/regrind blend is demonstrated and discussed."
For many years the capillary rheometer has served as an important tool in R&D and product development laboratories. It has even gained in popularity in the QA laboratory as a tool for assuring the processability of a resin. More recently two and even three barrels designs of the capillary rheometer have become more generally available. The main applications of these instruments have been for providing directly corrected viscosities and for doing measurements of extensional properties. However, very little has been said about the opportunity these rheometers provide for applications in QA and product development. This paper discusses the capabilities of the dual barrel rheometer for direct comparisons of materials in QA and for the fast and easy observation of changes in the flow properties of a new product, as it is modified in the development process.
In order to verify the accuracy of the filling analysis program (C-MOLD) for injection molding, pressure losses across four characteristic segments (Nozzle & Sprue, Runner, Gate, and Cavity) of the flow channel in the test mold were measured for the HDPE under various molding conditions regulated exactly. Without the additional assumptions in the simulation, the flow properties with the pressure-dependent viscosity and the juncture loss measured actually were added to the indispensable pvT-data, thermal conductivity, specific heat for simulation. After confirming good agreement between the observation and the simulation at the flow segment wherein thermal properties affected weakly on the pressure loss, the effects of the heat transfer coefficient between the polymer and the mold metal on the simulation were examined. By introducing the heat transfer coefficient of 1,200W/m2-K, instead of the default value of 25,000 W/m2-K, we found that the difference between the simulated and the observed pressure losses at the four segments were reduced to less than 20%.
Differential scanning calorimetry was used to analyze the state of water in crosslinked glycerol methacrylate and hydroxyethyl methacrylate hydrogel polymers. Glass transition temperatures were obtained for the dry materials and for the materials equilibrated at room temperature (23°C) and humidity (55% relative humidity). The total crystallization enthalpy was determined for these hydrogels equilibrated in water and at several states of partial hydration. The enthalpic information was used to quantitatively determine the fraction of nonfreezing water in the hydrogels. The integrated areas of the crystallization exotherms were reported to qualitatively access the freezing-bound and free water contents.
As the injection mold market increases, Time and Costs Reduction will be important aspects for mold makers. A detailed analysis of todays workflow in the mold making industry has pointed out the need for tailored tools in an integrated environment. The COSMOS project, (a pre-competitive European Union founded project) wants to enhance CAE integration and data exchange in CAD-based mold design. A PDM-based (Product Data Management) environment is being tuned on the basis of a new Concurrent Engineering-based approach. The expected results will lead to a reduction in time-to-market by about 30% and cost of about 40% as compared to the traditional injection mold design and manufacturing paradigm.
Determination of filled regions in extruders is important to the understanding of the operation of the extruder. This information can be useful to predict various performance measures for unit operations such as mean residence time and chemical conversion. A model is proposed that predicts the filled volume length for the extruder, based on the pressure drag flow model. This model is dependent on the system geometry in addition to the conveyed fluid's properties. Experiments have been performed that shows the ability of this model to predict the filled length in Co-rotating Twin-Screw Extruder (CoTSE) based upon a determined channel percent drag flow and specific throughput.
In Gas-Assisted Injection Molding, gas channels are usually utilized as a gas transfer system. However, the gas channel can be considered to have dual purposes; it can be used as inner cooling channel to improve fast cooling and to reduce cycle time without losing part quality. In this study, a simple plastics part with an open gas channel is used for prediction of cooling effect when gas channel is acting as a cooling channel by introducing the mixture of gas and liquid. Results can be drawn on how fast the part cooling is and how much the fingering effect reduces. Most importantly, we can compare how the quality differs between the gas-injection molded part with and without internal cooling.
Cracking in the injection-molded part is one of the problems which tooling engineer and/or design engineer often encounter in the molding process. This phenomenon originates from several factors. Among them are high-speed injection, high/long packing pressure/time, etc. In reality, the cracking may be recognized after long time, i.e. days or weeks after part production. In this study, CAE simulation helped to predict the potential cracking area in the plastics part and possible solution(s) to reduce or eliminate cracking by either redesign the part or changing plastics material or processing conditions through simulations. The part used in this study is from the thin-wall injection molded speaker grille product. In the analysis, this speaker grille would be 3-layer solid that is considered real 3D solid model.
Parameters typically used to optimize the performance of maleated polyolefins in various applications are the level of maleation, molecular weight, and amount of the maleated polyolefin used. However, not all the anhydride functionality present in a maleated polyolefin is covalently bonded, or bound to the polymer backbone. The bound maleic anhydride content is a function of the starting polymer and maleation process. This paper uses a simple analytical procedure to determine bound vs unbound maleic anhydride in maleated polyolefins, summarizes bound maleic anhydride values for selected experimental and commercially available materials, and discusses how the level can impact application performances.
The effects of plasticizing Barex, a commercial polyacrylonitrile/methyl acrylate (PAN/MA) copolymer, with carbon dioxide (CO2) are studied. Differential scanning calorimetry (DSC) is used to evaluate the resulting shift in the glass transition temperature (Tg) of Barex following plasticization. Pressurized capillary rheometry is used to evaluate the differences in melt rheology prior to and after plasticization. Dynamic rheology data is used to perform an Arrhenius type analysis that allows an estimation of the shift in processing temperature. An estimated 20°C decrease in processing temperature can be obtained upon CO2 plasticization, which slows the kinetics of the copolymer degradation (crosslinking) at processing temperatures.
Polyamides are currently employed in packaging applications requiring high oxygen barrier. The inclusion of small quantities of organo-montmorillonite clay into polyamides leads to an exfoliated clay morphology. By creating a tortuous path for gaseous diffusion, this morphology results in considerable enhancement in the barrier properties of the material. Characterization of the nanocomposite film by X-ray diffraction, transmission and scanning electron microscopy, and atomic force microscopy shows extensive exfoliation of the clay platelets into the polyamide matrix. The clay platelets tend to align themselves parallel to the film surface during the blow molding process. This paper discusses the structure-property relationships in polyamide-based nanocomposites and their utility in high barrier applications.
Analysis of flow and pressurization in single-screw extruders can be carried-out using one-, two-, and three-dimensional flow analyses. In one-dimensional analysis, the extrusion flow can be represented by the idealized model flow between infinitely long and wide parallel plates, i.e., the Generalized Couette flow, thus enabling the generation of analytical solutions. In two-dimensional analysis, the screw geometry is unwrapped in the helical direction of the screw and the lubrication approximation applied. For three-dimensional analysis, a mesh is generated which describes accurately the geometrical screw configuration without any unwrapping. For both the two- and three-dimensional analyses, the Galerkin Finite Element Method is utilized in the solution of the governing equations of conservation of mass, and momentum. In this study, the different analyses will be described for the flow of Heschel-Bulkley fluids with wall slip, and simulation results presented and compared for the special case of a Newtonian fluid for three different screw geometries. The limits of application of the different analyses will be discussed.
Twin screw co-rotating kneaders are popularly used as plasticating compounding extruders for a broad range of technical plastics and commodity polymers at high rates. Melting in these devices is always initiated by a combination of kneading disks which effect repeated bulk deformations of the plasticating mass. The resulting melt quality is sensitive to size, shape, and physical properties of the feedstocks, to the configuration of the melting screw, and to operating conditions. Four pelletized polymers were each plasticated using a split barrel ZSK40 configured with two screws and run at two operating conditions. Carcasses were examined in place and by dissection for overall melting lengths and residual particle shape and melt texture.
Fiber length retention during incorporation of glass fibers into a polymer matrix has re-gained importance over the past few years. This can be attributed to the introduction of injection moldable long fiber reinforced thermoplastics. The longer fiber length in the feed material results in 5 – 20 times longer fiber in the molded part with significant improvements in final product properties when compared to its short fiber counterparts . Long-fiber composites have been found to exhibit overall higher physical properties compared to their short-fiber analogs. Mechanical properties, elevated temperature performance and creep and fatigue endurance are all higher for long-fiber composites . An indication of how increased fiber length translates into better properties can be seen by burning off the matrix resin from a molded part (see Figure 1). The residue is a three dimensional structure formed by a network of long fibers that retains the original shape of the part. This allows better distribution of stresses throughout the part.
Microelectronics is a field currently in high demand considering its many applications. Concerns are raised to improve reliability and performance of high performance packages. To do this, one must first understand the physics behind the failures of these small packages. To do this, non-destructive testing and the use of microscopy to identify the location of failure can be employed. By identifying the mode of failure in these packages, a micromechanics and materials approach can be used to implement a new package that shows a significant improvement in both the reliability and performance.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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