SPE Library

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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Conference Proceedings

Stress-Induced Crystallization
K.P. Palluch, A.I. Isayev, May 2000

The stress development during polymer processing of semi-crystalline polymers can cause stress-induced crystallization and changes in the crystallization kinetics. The integration of orientation entropy changes calculated by non-linear viscoelastic constitutive equations in crystallization thermodynamics gives us a proper physical model to describe the crystallization behavior in oriented polymer melts. Based on the model a new economic characterization procedure for stress-induced crystallization is put into application. The new model is used to simulate the stress-induced crystallization during the injection molding of isotactic polypropylenes. The results are compared with experimental data.

Interfacial Adhesion in Thermoplastic/LCP Blends
A.I. Isayev, N. Shah, May 2000

Knowledge about interfacial adhesion in thermoplastic/LCP blends is important for manufacturing self-reinforced composites with improved performance. Thus, in the present study, interfacial shear strength between different LCPs and thermoplastics was measured by using fiber pullout method. The LCPs employed were Vectra A - 950, Vectra B - 900, Ultrax KR - 4002 and Ultrax KR - 4003. The thermoplastics included were high density polyethylene, polypropylene, polycarbonate, polyphenylene oxide/polystyrene alloy, polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polyetherimide and copolyester. Based on these measurements, the similarities and differences in interfacial behavior of various pairs have been found. In addition, ranking of various pairs of thermoplastic/LCP blends has been made concerning their interfacial shear strengths.

Rheology of Highly Interactive Polymer-Filler Mixtures
G. Havet, A.I. Isayev, May 2000

The dynamic properties of polystyrene (PS)/silica mixtures of various concentrations were investigated as a function of frequency and strain along with the flow curves. An abrupt change in the viscoelastic properties is noticed above 1% volume concentration. Observations by means of scanning electron microscopy (SEM) indicate the creation of a 3D network through bridging of filler particles by adsorbed polymer. The rheological behavior is simulated utilizing a double network created by the entangled polymer matrix and the adsorbed polymer. Both networks are represented by a Giesekus viscoelastic constitutive equation. The dependence of rheological properties on filler concentration is taken into account through the density of polymer-filler interactions and a hydrodynamic reinforcement. The relative contribution of both networks is computed through the energy balance consistent with the thermodynamics of the chemical interactions and fluid mechanics. This self-consistent approach allows one to predict the major features of the rheological behavior of such systems.

Differential Scanning Calorimeters with Increased Sensitivity and Resolution
Vijay N. Reddy, Randy Byrne, Nobutaka Nakamura, Osamu Sakamoto, May 2000

Resolution and sensitivity are two of the most important properties of thermal analyzers. Resolution can be described as the ability to separate and observe two events, which occur close to one another and sensitivity is the ability to detect very small effects. The ability to significantly shorten the overall experimental time and increase throughput, yet obtain data with improved resolution and greater sensitivity are highly desirable. In many labs involving thermal analysis of polymers, today's instruments provide a similar choice. In this paper, improved sensor design and firmware in Differential Scanning Calorimeters (DSC) will be discussed using few application examples.

Linearity and Non-Linearity of Mechanical Properties in Blends of Virgin and Recycled HDPE's
Paul Miller, Edward Kosior, Syed Masood, Pio Iovenitti, May 2000

This paper investigates the behaviour of blends of Recycled Milk Bottle Resin (R-MBR) with Injection Moulding or Film Blowing grade HDPEs (IM-HDPE or FB-HDPE). This was done by measuring changes in mechanical and rheological properties as a function of blend composition and compounding intensity. There were three categories of compounding: bag mixing (BM), single pass single screw extrusion (EBx1) and double pass single screw extrusion (EBx2). The results were examined for linear and non-linear trends, and relationships between morphology, mechanical properties and molecular weights were proposed.

Resistance of Glass Fiber-Reinforced Thermoplastics to Water Hammer
Takafumi Kawaguchi, Hiroyuki Nishimura, Fumiaki Miwa, Kazunori Ito, Takashi Kuriyama, Ikuo Narisawa, May 2000

The resistances of three kinds of short glass fiber or glass bead-reinforced plastics [polyphenyleneether (GFPPE), polyphenylenesulfide (GFPPS), and polyoxymethylene (GBPOM)] to water hammer were studied. The fracture surfaces and the cross sections of the fracture surfaces were observed to investigate the fracture mechanism. PPE showed poor resistance to water hammer compared to PPS and POM. Investigation of the fracture surfaces showed that their surfaces were rather flat and hardly any glass fibers were observed at the fracture surfaces. It was found that the characteristic fracture surfaces was attributable to the breaking of the glass fibers at the fracture surface which is hardly observed in other modes of fracture such as tensile fracture.

Electrofusion Joint Strength of Polyethylene Pipes
Hiroyuki Nishimura, Fumio Inoue, Hiromichi Inoue, Hideki Tani, Yuji Higuchi, May 2000

Electrofusion (EF) joints have been widely used as easy-to-fuse and high-quality joints for joining polyethylene (PE) pipes. When we introduced EF joints 150 mm or more in diameter, an electrofusion simulation program was concurrently developed to reduce time for design and experimental work. It was verified that the simulation results calculated by using the program agreed well with the experimental results. This paper describes the features of the program and its application to EF joints developed for the casing pipes of district heating and cooling pipelines.

Advances in Fusible Core Technique
E. Schmachtenberg, O. Schröder, May 2000

Fusible core technology allows the production of injection molded parts which cannot be manufactured by conventional mold technology because of undercuts and internal geometries. The production sequence consists of several process steps. The reliability and economy of the process depend on each process operation as well as on the correct design of the interfaces between the steps. This paper presents sample applications, production methods and potentials for future applications. Moreover, current R+D work is described which mainly focuses on improved process engineering, a better understanding of the boundary conditions of product design and a wider range of applicable polymers.

Scale-Up Rules for Blow Heads
H. Potente, B. Krell, S. Kramme, May 2000

Alongside time-intensive flow analyses, requiring extensive calculations, the use of dimensional analysis is an alternative strategy for the design of blow heads. Selected blow heads are broken down into their basic geometrical elements and subsequently transfer formulas are established. Assuming for reasons of simplification that the material flow is isothermal, stationary and laminar and that wall adherence is prevailing, the concept of representative quantities is used to take into account the non-Newtonian behavior of the melt. The combination of the basic elements produce the full-scale device which -compared to the model - display both identical processing times and loss of pressure as well as unchanging shear velocity and wall shear stress, but will achieve different levels of material throughput.

The Processing of Renewable Resources Using a Short Single Screw Extruder with a Combined Section for Solid Conveying and Plastification
H. Potente, F. Reckert, May 2000

Due to the growing awareness of the necessity to protect the environment, the substitution of conventional plastic materials by biodegradable materials is gaining an ever increasing importance. An application that makes sense especially with regard to economic aspects is the processing of non-modified crop on plastics processing machines. This is made possible by the concept of a single-screw extruder equipped with a metering unit with which the total amount of energy required to plasticize the material is generated exploiting the friction occuring in the solid matter. As opposed to conventional extruder designs which exhibit separate areas for conveying the material and for plasticizing the same, these two tasks are united in one section of the extruder. The concept is based on specific geometries of screw and cylinder which secure that the entire mass flow passes a shear zone situated in the material conveying zone, warranting a very efficient transmutation of energy.

Transcription of Small Surface Structures in Injection Molding - An Experimental Study
Uffe R. Arlø, Erik M. Kjær, May 2000

The ability to replicate the surface roughness from mold wall to the plastic part in injection molding has many functional and cosmetic important implications from medical use to designer products. Generally the understanding of surface transcription, i.e. the replication of the surface structure from mold to plastic part, also relates to micro injection molding and molding of parts with specific micro structures on the surface such as optical parts. The present study concerns transcription of surface roughness as a function of process parameters. The study is carried out with a polystyrene part, process parameters at typical levels and a rough spark eroded mold surface with Ra = 12.6 ?m.

Influence of Molecular Weight Distribution on LLDPE Blown Film Processing Conditions and Property Sensitivity
Choon K. Chai, J-L. Selo, Eric Osmont, May 2000

The effect of key blown film processing parameters on linear low density polyethylene (LLDPE) film properties was investigated. The processing parameters studied were frost line height, blow up ratio, output rate and melt temperature. Statistically designed experiments were conducted with three high alpha olefins (HAO) copolymers of similar melt index, density and short chain branching distribution (SCBD) but of different molecular weight distribution (MWD). Film impact strength variations with processing conditions were found to depend strongly on polymer MWD.

The Relations between the Composition and the Permeation Resistance of the Polyethylene/Compatibilizer Precursor/Modified Polyamide Blends
Wern-Shiarng Jou, Kan-Nan Chen, Sheng-Shan Chang, Hung-Tse Yao, Jen-Taut Yeh, May 2000

The effects of compatibilizer precursor (CP) and modified polyamide (MPA) contents on the permeation rate of unleaded gasoline and on the morphology of polyethylene/modified polyamide (PE/MPA) blends are investigated. The optimal composition of PE/MPA for the lowest gasoline permeation rate is PE70/MPA15, which blended 30% of MPA (compounded 15% of CP with 85% of PA) with 70% of PE. The barrier properties improvement of PE/MPA blown tubes against unleaded gasoline reach a maximum (367 times at 25°C) comparing with genetic PE.

Color Mixing Performance in Injection Molding: Comparing a Conventional Screw and Non-Return Valve to Those Designed for Improved Mixing
Brent A. Salamon, Mark A. Spalding, Joseph R. Powers, Myrna Serrano, William C. Sumner, Susan A. Somers, Russell B. Peters, Jr., May 2000

A competitive global economy requires processors to consider every available option to reduce their costs. One popular approach is to convert to in-house coloring, the blending of natural resin with color concentrate at the injection molding machine. With this approach, the greatest cost savings can be realized by using the highest letdown ratio of color concentrate possible. However, to successfully realize this cost savings, good mixing performance in the barrel is essential. This study will show that a mixing screw provides better mixing than a conventional screw and that a sleeve mixer non-return valve significantly improves mixing when it is used with either screw. Thus, the improved productivity of in-house coloring can be realized by applying this technology.

Modeling of the Mechanical Behavior of Nonlinear Viscoelastic Materials under Multidimensional State of Stress
M. Wanders, E. Schmachtenberg, May 2000

The mechanical behavior of nonlinear viscoelastic materials depends on time, temperature, loading rate and height of load. A model is presented that allows the simulation of nonlinear viscoelastic materials under multidimensional state of stress and load history. This 3-dimensional deformation model is built by parallel arrangement of a certain number of basic elements. Each basic element consists of an elastic Hookean element and a damper system (3D damper) to describe the viscous properties. The model is calibrated by isothermal strain controlled tensile tests at different temperatures. Along with suitable calculation algorithms this model offers the ability to simulate any multidimensional load history caused by direct stresses. The model allows the simulation both of quasi-static and dynamic loading at different temperatures.

New Compatibilizers for Styrenic/Olefinic Blends
A.J. Uzee, May 2000

Styrenic block copolymers (SBC's) are increasingly being used as compatibilizers (interfacial agents) in polystyrene and polyolefin blends with either virgin and/ or recycled resins. Many technical articles and patents on blends of styrenic and olefinic polymers indicate that styrenic block copolymers and more specifically styrene-butadiene- styrene copolymers function as compatibilizers. This paper reports the effectiveness of new block copolymers to compatibilize styrenics and polyolefins. In addition, a comparison of physical properties of blends using new block copolymers is made to those currently used in the industry.

Compatibilizers for Thermotropic Liquid Crystalline Polymer/Polyolefin Blends Prepared by Reactive Mixing: The Effect of Processing Conditions
Younggon Son, R.A. Weiss, May 2000

The effect of processing conditions on the melt formation of a graft-copolymer compatibilizer for blends of a thermotropic liquid crystalline polymer (TLCP) and polyolefins was investigated. The compatibilizer was formed by an melt acidolysis reaction of a 50/50 (w/w) blend of TLCP and the sodium salt of a poly(ethylene-co-acrylic acid) ionomer. The effect of various processing conditions in a batch mixer and a single screw extruder on the extent of reaction were assessed. The extent of graft-copolymer formation and the efficacy of the product as a compatibilizer for TLCP/polyethylene blends was affected by the processing temperature and the rate screw (or rotor) speed.

Investigative Analysis of the Influence Reprocessing Has on the CIEL*a*b* Tristimulus Color Values of Special Effect Thermochromic Polypropylene
Trudie Sands E. Duart, May 2000

The intent of this investigation is to determine the feasibility of achieving optimal color quality when reprocessing special effect" thermochromic polypropylene. The investigation involves blending extruding and molding samples of virgin and reprocessed "special effect" thermochromic polypropylene. All samples undergo visual as well as CIEL*a*b* Tristimulus color value testing. Analysis of the visual and numeric data will determine whether the color values of the reprocessed material remain within the color space established by the standard. If the investigation proves that the color values are within the acceptable color range then recycling of the material would be both economically and environmentally beneficial."

Impact of Fines Separation on Reinforced Thermoplastic Regrind
Jason S. Trahan, Kurt Hayden, Paul Engelmann, Michael Monfore, May 2000

The process of regrinding thermoplastic resin is associated with a series of handling, feeding, contamination, and melting problems. Some have suggested that removal of fines from reinforced resin can have an adverse effect on certain material characteristics and processing conditions. A dedicated system employing special grinding techniques, aspiration of fines, and static abatement was used to study the impact of fines removal through a number of generations of process history. The system once optimized allowed a detailed study of the relative viscosity, glass content, and tensile properties of the material conditions. The results provide a foundation for molders seeking to incorporate thermoplastic regrind into current production settings.

Understanding Wear Mechanisms: The Key to Mold Life
Paul Engelmann, Kurt Hayden, Philip Guichelaar, Robert Dealey, Michael Monfore, May 2000

Molders and mold builders have been puzzled by unanticipated wear in the injection mold. For instance, sometimes hard components fail, and adjacent softer components last. A thorough investigation has been conducted on the types of wear that occur in a mold, as part of the long-term wear studies on copper alloys. Three very distinct mechanisms exist: abrasive, erosive, and adhesive wear. Characteristics of these three wear mechanisms have been isolated as they relate to injection molds. Certain design features in a mold are linked to each of these mechanisms. Understanding this relationship makes mold wear more predictable, avoidable, and correctable.

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