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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Dynamics of Hot Runner Purging
Purging of hot runners consumes an inordinate amount of time, materials and money. A study to get an efficient color or resin change makes use of the viscosity reduction by varying process parameters, and using purge additives that influence viscosity and self cleaning characteristics. This paper reports a part of a study on how that shear rate and the temperature in the hot runner manifold and barrel affect purging. The results show that very high and low melt temperatures in both of them affect purging. The best temperature setting is a low temperature in the hot runner manifold and a low temperature in the barrel.
Wood Fiber Reinforced Polyamides
Wood fibers are often used to reinforce polyolefins but not high temperature polymers like polyamide 6 and 66. These polyamides melt above 200 °C, which is often considered the maximum processing temperature for wood fibers. A variety of techniques for compounding and molding wood fiber/polyamide composites will be presented. These techniques are evaluated by examining fiber dispersion, fiber attrition and composite mechanical properties.
A Novel Approach for Measuring the Specific Volume of (Semi-Crystalline) Polymers at Elevated Cooling Rates Using X-Rays
A new method to determine the specific volume of polymers over a wide range of temperature and pressure based on X-ray attenuation was developed. This method allows the application of different cooling rates enabling the investigation of the density depending on the thermal history. Experiments were performed to investigate the devolution of the specific volume of an isotactic polypropylene at elevated pressures and cooling rates.
Effect of Die Geometry and Extensional Rheological Properties on Vortex Development in Rectangular Dies
The vortex development of a low-density polyethylene in different flat dies under various processing conditions has been analyzed by the Finite Element Method employing the modified White-Metzner model as constitutive equation. The theoretical results are compared with the velocity distributions measured by Laser-Doppler Velocimetry (LDV).
Optimization of Rotational Molding Cycle through Thermal Data Acquisition
The DataPaq Rotomolding Telemetry System in conjunction with the Medkeff/Nye Shuttle PD developmental rotational molder was used to study and monitor internal mold and oven temperatures. Continuous internal temperature readout along with the software package were used to optimize the cycle of linear low density polyethylene (LLDPE). Designed experiments were employed to investigate process parameters and select physical and mechanical properties.
An Experimental Study on Shear Stress Characteristics of Polymers in Single-Screwextruders
Frictional forces (for temperatures less than melting or devitrification temperature) and viscous forces (for higher temperatures) have important roles on solids conveying and melting processes in single-screw, plasticating extruders. These forces are related to the shear stresses at polymer-metal interfaces. This paper presents the shear stresses and melting fluxes at four sliding velocities and at temperatures ranging from ambient temperature to 230°C for LDPE, ABS, HIPS, and LLDPE resins at a fixed pressure of 0.7 MPa.
Summary Results of a Novel Single Screw Compounder
A novel single screw mixer is described having multiple elongational flow fields, upstream axial mixing, and thin film degassing. SEMs show high magnification examples of mixing including a PS/PE immiscible polymer blend, ceramic nano particles, and iscrete carbon nano tubes. Novel degassing over the mixer is cited using three vents in a 36/1 L/D single screw to process undried PETG.
Advances in Adhesion with CO2-Based Atmospheric Plasma Surface Modification
The use of gas and/or liquid-phase carbon dioxide (CO2) with atmospheric plasma discharge surface pretreatment technology can remove micron and submicron particulates and hydrocarbon-based contaminations on plastics and metals. The cleaning process is based upon the expansion of either liquid or gaseous carbon dioxide through an orifice. The paper provides an understanding of the basic removal mechanism and provides experimental evidence of remarkable adhesion improvements relative to a broad range of applications in electrical, medical, and automotive manufacturing communities.
Fundamental Structure-Property Relationship of Polymer Nanocomposites
The structure-property relationship of a set of model polymer nanocomposite systems has been investigated. The findings suggest that degree of exfoliation and aspect ratio of nanoplatelets in polymer matrices can greatly influence physical, mechanical and rheological behaviors of polymers. Most importantly, there appears to be a limit to which polymer nanocomposites can be applied for structural applications.
The Role of Chain Branching in Extrusion Blow Molding of Polyvinylidene Fluoride
The effect of long chain branching in polyvinylidene fluoride in extrusion blow molding is investigated in light of the enhanced rheological properties. The presence of long chain branching increased the melt strength; melt elasticity and strain hardening of the branched samples as opposed to their linear counterparts. These enhanced properties suggest better sag resistance during blow molding and higher blow-up ratio while achieving uniform wall thickness.
Efficiency Gains and Control Improvements Using Different Barrel Heating Technologies for the Injection Molding Process
This paper compares the energy efficiency and control response of band-heaters with a new technology that uses non-contact induction to heat the barrel directly through an interposed layer of thermal insulation. Quantitative results from both laboratory injection molding machine runs and bench-top tests are reviewed. The effect of barrel diameter, surface condition and band-heater type on efficiency and control response are also considered, as are the implications of thermocouple depth.
Evaluation of Fracture Toughness for Thin-Wall Injection Moulded Plastics
Evaluation of fracture toughness was studied by means of essential work of fracture (EWF), using 1mm thickness injection moulded double-edge notched tensile (DENT) specimens with two types of materials, ABS and PP. Stress level analysis is discussed in this paper by means of maximum nominal stress.
Full 3D Injection Molding Analysis and Modeling Tips for Complex Models
3D injection molding analysis is getting popular to get accurate result in the industry. However, mesh generation time and memory size for complex models are being demanded more than those of general model or conventional 2.5D analysis. This paper adopts simulation technology such as CVFEM(Control Volume Finite Element Method) or fast multipole method based on BEM(Boundary Element Method) and shows real case for large models. It does not only develop effective method to reduce modeling time, but it also performs analysis with significant performance enhancement.
A Comparative Study of Simulation Softwares for Stretch Blow Moulding
Blow moulding simulation softwares are effective tools for blow moulders to predict and improve the performance of blow moulding process. Not many such software are available in the market. This paper presents a comparative study of two blow moulding software - B-SIM and Blow View – for specific application of stretch blow moulding process. Features and capabilities are compared based on the simulation study of a plastic bottle.
Estimation of Polymer Melt Index with a Controlled Rate Capillary Rheometer and a Parallel Plate Dma
The measurement of polymer melt viscosity is done by both controlled stress and controlled rate capillary rheometers. Each method has its advantages and disadvantages. Often, tests are performed with a capillary rheometer under one mode of operation but then the results are required under the other mode of operation. Various users have adapted a variety of methods to allow for the conversion of data from one mode to the ther. This paper explores some of the methods used in making conversions and discusses important considerations whenever this is done.
Plastic Integral Hinges; Design, Processing, and Failure Analysis
This paper addresses the design issues and processing conditions that affect the performance of integral hinges. For example, the relation between the material properties and the design of the hinge is addressed. An answer will be given to the question why does the increase in the melt temperature improve the performance of hinges?" Some case studies of failed hinges are discussed to practically show the effect of processing material and design on hinges performance. Microscopy was used to investigate the failure mechanism of these hinges."
Replication and Optical Properties of Injection Moldings with Microstructures
The effects of replication and molecular orientation on optical properties of polycarbonates (PC) injection molded parts with microscopic v-groove features have been investigated on various injection molding conditions and different cavity shapes. For optical properties, the luminance of the injection molded parts has been characterized. The mold temperature had significant effect on the replication. The replication is closely related to the optical properties. It was found that the optical properties depended on replication in compared with molecular orientation.
Effect of Die Design and Wall Slip on Die Drool Phenomenon for Metallocene Based LLDPE: Theoretical and Experimental Investigation
The effect of die design and wall slip on the die drool phenomenon was investigated for metallocene based LLDPE. It has been found that die exit opening and wall slip can significantly reduce the die drool phenomenon. Moreover, theoretical research has revealed that die drool onset can be explained by the negative/non-monotonic pressure profile generated inside the die and/or at the die exit region due to melt elasticity.
Determination of Uniaxial Extensional Viscosity for Polyolefins by Improved Entrance Pressure Drop Measurements
In this work, specially designed zero-length dies were used for the entrance pressure drop measurements with the aim to determine uniaxial extensional viscosity of polyolefin melts by using effective entry length correction and Cogswell/Binding models and the results were compared with the extensional rheology determined with the Sentmanat extensional rheometer. Reasonable agreement between these two techniques has been obtained.
Evaluation of Scratch Behavior of Plastic Mouldings
Scratching mechanisms of injection molded PC/ABS blend were investigated. The scratching damage was microscopically observed by OM, SEM, and TEM. The scaly pattern and bank were observed in ploughing, wedge formation and cutting modes commonly. The micro cracking appeared in the bank in the case of cutting mode, and it would become internal cracks growing to the cracks and a cutting tip. The film laminated structure near the surface induced by injection moldings severely deformed and wavy pattern and elongated particles were found in the bank.
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