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

Effect of Processing Parameters on Bond Strength for Multicomponent Injection Molding

Shaival R. Mehta, Dipen R. Parikh, May 2001

TPVs already have a number of successful applications in many multiple component parts. Part consolidation and integration resulted in cost saving and added value. Useful attributes, such as soft touch for ergonomics, contrasting color for better consumer appearance and marking for corporate recognition, can be achieved along with better quality and performance. In those parts, TPVs play a very important functional role, as such integrated seals & gaskets for water tight applications, soft touch grips for kitchen wares, living hinges and/or energy absorption elements. Co-process fabrication technology takes advantage of the melt-processibility of TPVs and the heat fusion bonding to a compatible substrate. These multi-material techniques have been creatively used in co-extrusion, tri-extrusion, insert molding, two shot molding and even co-injection [1].

TPEs in Hot Runner Systems: An Elastic Entity

Robert C. Wegelin, Shaival R. Mehta, May 2001

Hot runner systems have been around since the early 1960's. They have provided users with runnerless, finished parts for many technically exciting applications. In producing these parts, materials play an important role in the type of hot runner system used to fabricate them. Hot runner systems lend themselves to multi-shot molding applications, which eliminates the need for three-plate cold runner systems. Hot runner systems are used for a variety of reasons, the main ones being a runnerless system with zero scrap, fast cycle times and, in many cases, improvement of part quality. There are no gates to trim. Cycle times are based on the part itself, and smaller gates can be used to improve the molded part appearance. While all this paints a rosy picture, disadvantages in hot runner systems do exist. Higher mold costs and longer learning curves, along with added personnel training, tend to make using these systems more costly. For high volume production, these systems are ideal and they can improve the ability to engage in a lights out" operation for best efficiencies. In our review we will touch briefly on standard hot runner systems for thermoplastics but the focus will be on hot rudder systems for thermoplastic elastomers (TPEs) and thermoplastic vulcanizates (TPVs)."

Ballistic Impact Measurements of Polycarbonate Layered-Silicate Nanocomposites

Alex J. Hsieh, John W. Song, Jon Nebo, Anant Singh, May 2001

The effect of layered-silicates on the impact response of polycarbonate (PC) nanocomposites against the .22 caliber fragment-simulating projectile was determined. The amount of nanoclays incorporated appears to be critical in the overall ballistic performance. For example, nanocomposites consisting of 5 wt.% nanoclays exhibit brittle mode of failure, while ductile deformation is observed for the nanocomposites containing 2.5 wt.% of nanoclays as well as for the PC control. Stress whitening, which is not observed in the pure PC, is apparent in the 2.5 wt.%-PC nanocomposites. This is consistent with their quasi-static mechanical response, and is attributed to good interfacial bonding and proper stress transfer between the matrix and layered-silicate reinforcements.

A Potential Screening Method for Interface Stability in Particulate Filled Dental Composites

A. Prasad, A. Karmaker, N. Sarkar, May 2001

This study involves in-vitro simulation and characterization of the degradation process of dental composites. Composite formulations with different silane contents on filler surfaces were prepared. Cylindrical test specimens of 6mm in diameter and 3mm in depth were prepared using visible light curing system. Cured specimens were treated with an aqueous solution of 0.1N sodium hydroxide (NaOH) at 60°C for various time intervals. They were then neutralized with hydrochloric acid (HCl) solution followed by 24 hours immersion in distilled water and air- dried. The radial surface of each specimen was polished and the depth of degradation was measured using an optical microscope. Specimens with optimized silane content exhibited the lowest degradation, and those with unsilanated fillers displayed the highest.

Printing on Vinyl-Part II, FTIR and TOF SIMS Studies

Joseph W. Burley, May 2001

Earlier surface analysis studies suggested that, at least in some situations, the print adhesion properties of barium/zinc stabilized, stearic acid lubricated, PVC are influenced by the migration (exudation) of a barium/zinc stearate complex. This paper expands the previous study in attempts to reproduce the effects observed on samples of commercially produced films, explain the origin of the migrating specie and to identify the variables which influence the extent to which the phenomenon occurs. The effects of different lubricants, stabilizers and processing conditions are studied. Mechanistic work suggests that a revised hypothesis is appropriate and that the hydrolyzed complex is actually formed in the PVC matrix and not at the surface.

Comparison of the Mechanical Performance of Extruded Blown and Cast Polyolefin Thin Film

M. Billham, A.H. Clarke, G. Garrett, G.M. McNally, W.R. Murphy, May 2001

Thin mono-layer films of metallocene catalysed polyethylene, linear low density and conventional low density polyethylene, as well as polypropylene, were produced from a 38mm extruder through a 75mm diameter blown film die and a 600mm cast film die. By using the same die gap on each die to achieve equal draw-down ratios, the influence of orientation from the two processes on the mechanical properties of each film was investigated. Tensile strength at break, Young's Modulus, percentage elongation at break, tear propagation resistance, in both machine and transverse direction all gave significant differences in properties with cast film when compared to different blow-up ratios for blown film. Differential Scanning Calorimetry was used to measure the percentage of crystallinity in each film. Differences were found to show that the cooling process as the melt exits the die has a significant effect on the percentage of crystallinity.

Novel Process for the Production of Long Glass Fiber Reinforced Composites

Gregor Chszaniecki, May 2001

Twin screw extruders have been used successfully to incorporate glass fibers in polymer melts. However, during the compounding step, the fiber attrition can be high, resulting in poor physical properties of the finished product. In order to obtain a high overall fiber length and a gentle treatment of the fiber, the glass roving has to be impregnated with melt prior to entering the extruder. The patented Berstorff solution presented in this paper is based on two counter rotating rolls, that feed the fibers to the extruder and impregnate them with melt. The impregnating unit is designed in a compact manner and can be sandwiched between two barrel sections of a co-rotating twin screw extruder.

Feeding and Processing of Compacted Fillers on a Reciprocating Single Screw Kneader Compounding System for Automotive and Masterbatch Applications

Colin G. Richardson, Hans-Ulrich Siegenthaler, Todd A. Lemanski, Frederic Jouffret, Georges Fourty, May 2001

Fillers are used in plastics to achieve a variety of beneficial structural and performance properties. These properties are maximized by using fillers in the form of powders with fine particle sizes and specific aspect ratios. The goal is to preserve these properties after compounding. Unfortunately, low bulk density materials like these tend to bring a significant amount of entrained air into the extruder that takes up volume, hampering, among other things, throughput rates. As an alternative to these powdered forms of fillers, compacted fillers can be used which significantly reduce the level of entrained air. As a result, processing and handling of these materials are much less labor intensive. Using a reciprocating screw kneading system, a number of talc filled formulations used for automotive and masterbatch applications were compounded over a variety of conditions. The results will show improvements in throughput rates when split feeding the powdered talc and marked improvements in handling, throughput rates and overall compounding performance when using the compacted talc.

Streamline Die Design for Complex Geometries

D. Beaumier, P.G. Lafleur, C.A. Thibodeau, May 2001

Severe tolerances of profiles in the plastic industry require a simple and accurate die design method. In this paper, we present a method taking simultaneously into account the flow-balancing problem as well as the complex dimensional changes occurring after the die exit. A network model is used to predict the flow behavior within the profile die. The model is non-isothermal and includes accurate sidewall effects. Experiments with capillary and slit dies were done to determine the swelling as a function of shear rate, residence time and temperature. Several die designs for a PVC profiles were realized. Tests conducted for rectangular PVC profiles confirmed the validity of the model.

Reinforced Plastic Design: Tensile Versus Flexural Fatigue

John A. Krohn, Glen E. Novak, Michael G. Wyzgoski, May 2001

Glass fiber reinforced thermoplastics are being used in applications where fatigue life is important. Although conventional S-N or Wohler curves can be adequate for design purposes, the inherent anisotropy of these materials is often not accounted for if one uses standard molded test bars. An additional factor, generally not recognized, is the difference between fatigue data generated in tension versus flexural loading. This paper will present fatigue data for several glass reinforced materials showing the relative influence of these effects. Simple rules of thumb to estimate the appropriate fatigue data for design pruposes are also provided.

Rheology and Crystallization in Fiber Optic Cable Jacket and Conduit Extrusion

Scott H. Wasserman, J. LaMonte Adams, May 2001

Rheological tests measure melt-state polymer flow, delineating molecular structure and predicting extrudability. Rheology of compounds used in fiber optic (FO) cable jackets and in the conduits that contain such cables will be our focus. Polyolefin-based jackets strengthen the FO cable and protect internal components, while the conduit provides long-term strength and protects the cables against environmental stresses. High density polyethylene use in these applications is growing rapidly, spurred by FO cable growth. Important properties in both applications include melt-state processability, stress crack resistance and solid-state stiffness. Melt rheology directly influences processability, combining with crystallization behavior to dictate final solid-state properties.

Reinforced Plastic Design: Microstructure and Stiffness of Tensile Bars

John F. O’Gara, Peter H. Foss, James P. Harris, May 2001

The majority of mechanical property data reported for reinforced thermoplastics and available to a part designer is based upon testing end-gated injection molded tensile bars. ASTM Type I injection molded tensile bars were molded of ~30 wt% glass-filled polybutylene terephthalate, polycarbonate, and nylon-66. Detailed microstructural evaluations of the lengths and orientations of the glass-fibers were made. The experimental elastic moduli are predicted to within 4% using micromechanics. As a general observation, the simulations reveal that the modulus for a 30 wt% short glass fiber-filled thermoplastic tensile bar is 50 to 70% that expected from a composite of unidirectional fibers of infinite lengths.

Coaching and Mentoring: Change Management

John R. Szymankiewicz, Jill E. Sackman, May 2001

In a global economy featuring mass customization, ubiquitous information, and extreme price and service competition, many companies have found it paramount to remain flexible. Flexible to answer customer needs and wants faster, better, cheaper. For many companies the required flexibility demands organizational change at a rapid rate. Organizational change, if not managed properly can cause serious internal and external performance issues. Coaching and mentoring can be used to manage, and even drive, change in your organization while building value and employee involvement in the change.

Phase Morphology and Cure State Characterization of Soft Thermoplastic Vulcanizates (TPVs) by Using Atomic Force Microscopy (AFM)

Oansuk Chung, Hari P. Nadella, May 2001

AFM shows comparable capability to transmission electron microscopy (TEM) for characterization of TPV phase morphology. Phase imaging by tapping mode AFM scanning gives good contrast between the rubber phase, plastic phase, and filler in a TPV. In addition to TPV phase morphology characterization capability, it can quantitatively distinguish the cure state difference of the rubber in TPVs. A procedure for the analysis on phase imaging data is demonstrated and a good correlation is observed between AFM data, weight gain, and modulus at 100% elongation.

Tear Resistance of INSPiRE Performance Polymer Blown Films

S. Wu, C. Bosnyak, D. Faul, L. Tau, Y. Huang, May 2001

Tear resistance is critical for Polypropylene (PP) blown film in packaging applications and has been widely evaluated by several ASTM standard test methods. However, for characterization and differentiation of the tear resistance of blown films, these factors should be considered: tear behavior, tear propagation trajectory, film thickness, and tear speed. The tear strength of several mono- and multi-layer INSPiRE performance polymer films was analyzed by several test methods in this paper. The effect of film orientation, loading speed, failure mechanism, and sample geometry on tear strength will be discussed. Some uniqueness of the tear behaviors and advantages of the INSPiRE performance polymer blown films will also be discussed.

Injection Molding Long Glass Fiber Reinforced Thermoplastic Composites

Scott Gottgetreu, May 2001

Long Glass Fiber Reinforced Thermoplastic (LGFRT) Composites are produced by a proprietary pultrusion process rather than conventional extrusion compounding. This pultrusion process provides a high level of fiber impregnation in the pellets with no fiber damage compared to conventional short glass compounding. The result is injection moldable pellets containing fully wetted fibers equal in length to the pellet, typically 11 mm. This longer, initial fiber length translates into improved properties in molded parts when processing with optimized molding equipment and conditions that preserve the higher aspect ratio. As a class, long fiber composites exhibit overall higher mechanical properties, better elevated temperature performance, lower wear, and improved creep and fatigue endurance. This paper will examine the advantages of long fiber composites, properties of long vs. short fiber, equipment, tooling and processing conditions to maximize fiber length in the molded part and resultant mechanical advantage. In addition, alternative processing techniques including structural foam, injection compression & gas-assist, types of thermoplastic materials used and typical applications will be discussed.

Dependence of Melting Behavior on Melt Index

Bo Ki Hong, Hyun Seog Kim, Chan I. Chung, May 2001

The dependence of dissipative melting behavior of solid bed on melt index ([MI]) was studied experimentally for polystyrene (PS) and high density polyethylene (HDPE). Melting occurs primarily by the heat generated in the melt film in dissipative melting. The melting rate and the shear stress were expected to decrease with increasing [MI] because of decreasing viscosity. For PS, the shear stress decreased as expected but the melting rate increased with increasing [MI]. For HDPE, both the shear stress and the melting rate did not show a simple dependence on [MI]. HDPEs with very low [MI] values exhibited unstable melting mechanism and their melt did not coat the metal surface. Such unstable melting mechanism is probably responsible for high screw wear. Shear stress depends on the viscosity in the melt film. [MI] only indicates the viscosity at low shear rates, far below the shear rates in the melt film, and by itself cannot indicate the viscosity in the melt film. Melting rate depends on the viscosity and also the velocity profile in the melt film. The viscosity and the velocity profile in the melt film depend not only on the [MI] but also on the shear and the temperature sensitivities in a complex way.

3D Blow Molding Today, an Overview about Different Systems Which Are Established in the Market Today

Michael Thielen, Frank Schüller, Martin Balzer, May 2001

3D-blowmolding was introduced some years ago. In the meantime a certain number of different systems became established in the market. Suction blowmolding, 3D-blowmolding with parison manipulation and a split mold, horizontal machine with vertically opening mold and a 6-axis-robot laying the parison into the cavity or a machine without a closing unit at all. All these systems can be combined with 6 or 7 layer coextrusion or with sequential coextrusion running hard-soft-hard resins one after the other. The paper gives an overview, production examples and an outlook to future developments.

In-Line Compounding: Effect of Screw Design on Control Pressure Stability

Gary S. Donoian, John P. Christiano, May 2001

In-Line" compounding is defined as any process in which both the compounding and the forming steps are performed at the same time. For these applications line stability is crucial and greatly effected by equipment selection and design. Presented is a brief overview of in-line compounding including control methods and factors effecting line stability. The pumping efficiency of various screw elements is established and their effect on control pressure stability examined. A modified screw design is presented which is found to produce a more stable control pressure."

Chain Extension of PA-6 and PA-6/66 copolymer via Reactive Extrusion with Triscaprolactamyl Phosphite (TCP)

M.K. Akkapeddi, Clark Brown, B. Vanbuskirk, May 2001

Polyamide 6 (PA-6) homopolymer and copolymers have been chain extended from a low molecular weight feedstock into high molecular weight, high melt viscosity nylon products via a reactive extrusion process using a novel chain extender viz., triscaprolactamyl phosphite (TCP). The chain extension process involves an 'activated' polycondensation reaction between the endgroups of the nylon. In this paper we will discuss the effect of the chain extender concentration and the extruder process conditions on the chain extension efficiency with respect to molecular weight and rheological property benefits achieved.