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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Viscoelastic Behavior of Ethylene-Styrene Interpolymers
The linear relaxation master curves of Ethylene-Styrene Interpolymers, ESIs, were correlated with the molecular weight distribution by using double reptation theory. From this modeling, the plateau modulus was obtained. The entanglement molecular weight of the ESIs calculated from plateau modulus was much closer to that of polyethylene than to that of polystyrene. This was attributed to the unique chain microstructure of the ESIs in this study which have no styrene-styrene dyads. The large strain nonlinear stress relaxation behavior was also studied and the experimental data were successfully described by the Doi-Edwards theory. The instantaneous recovery after stress relaxation was investigated. The recovery was correlated with stress relaxation by newly developed model of two coexisting networks.
Fundamental Morphology-Property Studies of Reactor Grade Thermal-Plastic Olefins (RTPO)
The relationships between morphology and several physical properties, namely, flexural, cryogenic Izod impact strength, and dynamic mechanical properties of reactor grade thermal-plastic-olefins (RTPO), were examined as a function of ethylene-propylene (EP) rubber phase content. It is shown that the cryogenic Izod impact strength is greatly enhanced as the rubber phase increases without sacrificing critical physical properties. Dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM) results indicate that a good compatibility is achieved between isotactic polypropylene (iPP) matrix and rubber phase, which contributes to balanced physical properties.
Verification Studies of Blow Molding Software on Ovalized Parisons in Extrusion Blow Molding
This paper is a study of ovalized parisons in extrusion blow molding simulation software. The software being used is BlowView. BlowView can be used to simulate the extrusion blow molding process and aids in reducing design time for accurate product thickness. BlowView is utilized to lower the development time when used correctly. This paper will compare the output from the simulated process to the actual manufacturing setup and results. Currently extrusion dies are being built using previous standards and educated guesses. Dies are originally built and usually needing of modification to produce the desired profile. With the use of the computer simulations, giving all the design considerations will accelerate the developing of the die and necessary process.
An Injection Molding Process Capability Comparison between Position and Hydraulic Transfer Modes across Various Degrees of Check Ring Wear
The purpose of this study was to determine whether using the traditional position transfer mode or the hydraulic pressure transfer mode produces parts with less variation under the conditions of successively greater check ring wear. The process capability characteristics that were used were the standard deviations of the part weights, part diameters, cushion values and pressure at transfer values for each of the various molding conditions. The hypothesis of the study was that a process set-up in a three-stage hydraulic transfer mode will be more resistant to process variations caused by molding with a worn check ring and therefore more capable than a three-stage position transfer mode process.
An Injection Molding Dimensional Capability Comparison of Three Molding Transfer Modes Each Run under Both a Two and a Three-Stage Molding Strategy
The main focus of this study was to determine whether or not the hydraulic pressure transfer mode would produce more consistent parts than the screw position transfer mode would under simulated machine wear. The comparison was made across both two-stage and three-stage process set-ups. The three modes tested included screw position, hydraulic pressure, and cavity pressure transfer. The comparisons were made across both a two-stage and a three-stage process set-up. All of the molding trials were completed under the conditions of a mildly worn check ring that was used to simulate a portion of the normal shot size inconsistency found in a traditional production molding environment. The results showed that the cavity pressure transfer mode produced the most consistent parts. The hydraulic pressure transfer mode resulted in less variation than the screw position transfer mode.
Practitioner Training Program for Troubleshooting Injection Molded Part Defects
The main objective of this paper is to develop a program for teaching plant floor molding personal how to solve injection molded part problems and defects. A prioritized troubleshooting guide was developed using 12 common defects. The four defects that a case study was successfully performed on were vacuum voids, struck parts, color streaks, and discoloration. These four will be further discussed in this paper. Each defect was produced using different combinations of mold, material, and process conditions. The case study was performed to verify what actually causes each defect and to what degree.
Non-Destructive Means of Measuring the Glass Density of a Fiberglass Preform
The purpose of this experiment is to determine a non-destructive means of measuring the glass density of a fiberglass preform. This study includes two techniques: using a concentrated light source with a light meter and by using a thickness gage. The light meter measurement is taken by placing a concentrated light source on one side of the preform and the light meter on the opposite side. The thickness gage measurement is taken by pushing a pin through the preform and by using a dial gage to measure the thickness of the preform. Both of these measurements are believed to be related to the density of the fiberglass.
Improving Mechanical and Organoleptic Properties of Polypropylene
In an attempt to find a long term heat stable grade of polypropylene this project is designed to take pure flake polypropylene directly from the reactor and add specific fibers, fillers and additives with a minimal amount of processing. Polypropylene is not the usual material in potable water applications due to organoleptics and mechanical property weaknesses, which occur at elevated temperatures. With materials and additives, it is postulated that organoleptic issues can be lessened or eliminated from the finished product. Testing for mechanical properties such as heat deflection temperature (HDT), tensile strength, and taste and odor characteristics, will be conducted in order to create the ideal material for this application.
Development of Crosslinkable Binder System for Metal Injection Molding Using Urethane Technology
Shape retention of Metal Injection Molding (MIM) parts throughout the debinding and sintering stages of production is a common problem among molders. Slum ping of parts often causes distortion in complex shapes, minimizing surface details. Challenges in development of a binder system include powder compatibility, powder wetability, and polymer compatibility. A mix of coupling agents, surfactants, anti-oxidants, plasticizers and compatibilizers must be determined. The feedstock must not cure during com pounding or injection molding. Sample batches will be com pounded and molded. Successful candidates will be tested for shape retention and mechanical properties.
Verification of Parison Shape and Diameter with Extrusion and Blow Molding Simulation Software
The objective of this study is to use results from the analysis package, an extrusion simulation software program, to determine extrusion blow molding parison shape and thickness. This comparison will be used to develop a correlation between the software and actual trials while determining the software's ability to accurately predict parison geometry. This study is being done because this information is not easily determined and is needed for accurate blow molding simulation. In this study a parison will be modeled and trials will be run using different factors. The factors used will be varying wall thickness, speed, and temperature. Actual machine trials will then be conducted using the same factors. Measurements will be taken using a laser-mic so that a comparison can be made between the software and actual results. A correlation will then be developed from the comparison data. CAE has greatly decreased time to market in the injection molding field, now this same advantage can be found in the extrusion blow molding field.
The Effects of Ultrahigh Shear Rate and Shear Duration on Mechanical Properties of Commercial Polymers
Material manufacturers are forced to theorize the maximum shear rate limit that a polymeric material can withstand. The true shear rate limit of a material is rarely known. For the study effects of high shear rates and increased time of shearing on mechanical properties have been analyzed by creating a high shear region within an injection mold. Ultrahigh shear rates were created by reducing runner thickness. The effects of shear duration were analyzed by changing the length of the high shear region in the mold. The research looks at both glass-filled and unfilled polypropylene, nylon, and polycarbonate resins.
Raising the HDT and Elevated Temperature Tensile Properties of Injection Moldable HDPE by Dry Blending with Small Amounts of Dicumyl Peroxide
Polyethylene can be modified to improve the elevated temperature properties of the polymer by three dimensional cross-linking. One method of cross-linking is by using organic peroxides. The goal of this experimental study is to raise the Heat Deflection Temperature and elevated temperature tensile properties of high density polyethylene by dry blending with small amounts of dicumyl peroxide and injection molding the resulting composite using typical process conditions for polyethylene. The peroxide will be blended with polyethylene, at different weight ratios, and injection molded into various test specimens. Mathematical models will be developed from the results of the experiment to predict the change in heat deflection temperature that occurs from the cross-linking.
The Effects of Long Term Ultraviolet Radiation on the Mechanical Properties of Wood Flour Filled Recycled HDPE
Many outdoor products made from conventional lumber can be produced using wood flour filled polyethylene as a replacement material. In these applications the effect of ultraviolet radiation from the sun on the mechanical properties of these materials is important to understand prior to the design of any outdoor product. This study will examine the impact of long term ultraviolet exposure on the mechanical properties of wood flour filled high density polyethylene. An accelerated QUV testing apparatus will be used to simulate long term exposure to the sun. Impact strength, toughness, flexural modulus, and tensile strength will all be evaluated.
Linear Shrinkage Differences in Plastic Injection Molded Parts
Shrinkage occurs in all plastic injection molded parts. This study focuses on the shrinkage differences between amorphous and semi-crystalline plastics as well the shrinkage effects of process, wall thickness, and flow direction. A specially designed modular mold was used. The mold includes a 50.8 mm by 203.2 mm cavity with adjustable wall thickness and gating. Various neat and filled materials were processed using high and low pack pressures. The plaque samples were molded at thicknesses of 2 mm and 3 mm. Conclusions were made based on the differences in material, thickness, processing parameters, and flow direction. This information will help mold designers and moldfilling analysts develop better strategies in sizing their cavities for shrinkage and positioning their gates.
Development of a Rotational Molding Machine with Integral Heating and Cooling Passages within the Mold
Rotomolding is a process that is traditionally used to make larger complex shaped parts. A mold, traditionally, attached to a spider and arm, is moved through three or four different zones for loading, heating, cooling, and unloading. The mold(s) are rotated around two axes to allow the material to strike all internal surfaces of the mold. The heating occurs in large ovens where the mold is heated by radiation and convection until the plastic melts and coats the inside walls of the rotating mold. This paper will present ongoing construction and theory behind development of a rotomolder with integral heating and cooling passages within the mold. FIGURE 1 shows the entire machine with the mold mounted.
Breaking Barriers to Higher Output Rates with Densified Ultrafine Talc during Melt Compounding on the Corotating Intermeshing Twin Screw Extruder
The melt compounding of densified and nondensified ultrafine talc into polypropylene was performed on a 40 mm corotating twin screw extruder for comparison of compounding characteristics and product performance properties. Compounding nondensified talc was found to be volume limited by the maximum quantity of talc that the machine could be fed whereas the densified talc compounding was torque limited. The plastic performance properties for both types of talc filled compounds were comparable and would be widely acceptable for these high performance grades of talc filled polypropylene. Predictions of throughput rates on larger machines with higher toque ratings are included.
Requirements for Rapid Growth of All Olefinic Automotive Interiors
TPO has seen a major growth in the exterior applications such as fascias, claddings etc. for the last decade. For automotive interiors the growth has been slow and more in the area of hard feel applications than soft touch applications. Soft interiors are still a challenge due to many reasons including overall system cost. The driving force for TPO in Europe is mainly recyclability while in the USA, it is long-term durability. This paper describes the key limitations of the current TPO systems which are: poor grain retention of TPO skin, shrinkage in-consistency of the skin, high cost of priming (or other treatments) and painting of the skin, lower process window of the semi-crystalline TPO material during thermoforming or In-mold lamination / Low pressure molding, high cost of the foam, low tear strength of the foam for deep draw ratio etc. The paper shows the different ways of manufacturing the all olefinic parts which are: thermoforming over PP substrate, different Low pressure molding with in-mold lamination techniques, expanded PP foam process, slush molding etc. The limitations for each process and suggestions to overcome the disadvantages will be discussed to make all olefinic TPO interior parts viable and cost effective. The possibility of reducing the overall system cost will also be discussed such as: general information on formulation development to reduce the skin thickness for thermoforming, how to improve the properties of foam to reduce the thickness without affecting the formability and resiliency, value added recyclability of the skin/foam offal from production, and improving the paint efficiency etc.
Molecular Orientation of Crosslinked Polyethylene
To achieve improved mechanical properties, crosslinked polyethylene was uniaxially stretched above the crystalline melting point, (Tm). The material was stretched at different draw temperatures, draw speeds and to different draw ratios (?). The effect of different gel contents was also examined. For the molecular oriented samples tensile strength was shown to increase with increasing gel content. Tensile stress at yield (?y) was found to decrease at ?<1.5 and to increase for ?>1.5 while tensile stress at break (?B) was found to increase linearly with increasing ?. A lower draw temperature was shown to have an increasing effect on the tensile strength.
Melt-Flow Instabilities in Metallocene Based Polyethylenes
In capillary flow surface distortion of the extrudates, know as shark-skin" has been intensively investigated for decades especially in conventional polyethylene. Few papers however have been published using metallocene catalyzed polyethylenes although this instability represents currently one of the most serious limitation for the commercial application of these new polymers. In this contribution we present dynamic viscoelastic and extrusion capillary results of a series of polyethylenes and copolymers with 1-hexene (SCB) produced by single-site catalysts. Several of the samples analyzed content also small amounts of long chain branching (LCB). We investigate the effect of the molecular weight and the molecular architecture on the appearance of shark-skin and novel methods are discussed to overcome this limitation. A new type of distortion which we call "splitting" is described."
Properties of Polylactic Acid Optical Copolymers Achieved through Stress Induced Crystallization
The use of polylactic acid for common thermoplastic applications has grown substantially in recent years. The stereo structure of polylactic acid can be varied by polymerizing controlled ratios of the D- and L- isomers of lactic acid. Cargill Dow Polymers, LLC has developed a unique manufacturing process for polylactic acid, whereby lactide, one of the intermediates of the process, can be separated by optical composition, and then polymerized with controlled stereo composition. In turn the level of crystallinity can be varied from highly crystalline to amorphous, resulting in a wide range of properties that can be optimized for many applications. Fabrication processes using stress-induced crystallization take full advantage of the semi-crystalline nature of polylactic acid. The strain hardening and shrinkage properties of various optical copolymers of polylactic acid made by stress induced crystallization have been studied.
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