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

Modelling Impact Fracture and RCP Resistance of Thermoplastics from Cohesive Properties

Patrick S. Leevers, May 2004

Developers of thermoplastic materials for pressure pipe applications must design them to resist rapid crack propagation. However, they are usually able only to test them for resistance to impact. The hypothesis that both failure modes are dominated by adiabatic heating leads to good quantitative predictions for each property - and hence to an account of the relationship between them. Here, the model based on this hypothesis is extended to explore the influences on fracture resistance of molecular weight and of thermal property non-linearity.

Residual Strain Characterization Using an Embedded FFB Sensor: Measurements and Simulations

John Botsis, Fabiano Colpo, Laurent Humbert, May 2004

Residual strains in an epoxy specimen are investigated using embedded Fibre Bragg Grating sensors. A novel OLCR technique allows the direct reconstruction of the optical period and provides the strain distribution due to epoxy consolidation along the fibre. The experimental data show an excellent agreement with finite element simulations.

Designing Impact-Modified Polypropylene for Durability

C.P. Bosnyak, H.T. Pham, W. Zhou, A. Chudnovsky, May 2004

Polypropylene is increasingly being used as a structural load-bearing polymer in durable applications. Elastomer is usually added for impact toughness improvement but few studies address the selection of elastomer morphologies for resistance to failure due to load conditions over long time. This paper discusses the results of screening some polypropylene-elastomer blends for durability using a recently developed notch sensitivity methodology.

Failure Prediction in Polymer Composite, Sheet Metal Forming Dies

Young-Bin Park, Jonathan S. Colton, May 2004

This paper presents a systematic approach to predict damage in a sheet metal forming die fabricated from a composite (aluminum trihydrate-filled polyurethane). The dominant die failure mode is determined based on the mechanics governing the forming process, and the fatigue life is predicted. Both numerical simulations and experiments are performed to verify the method.

Investigating Environmental Stress Cracking with In-Situ Contact Angle Measurements

Peter J. Walsh, Alan J. Lesser, May 2004

This paper probes a hypothesis for initiation of environmental stress cracking (ESCR) based on a thermodynamic criterion for localized swelling induced by stress on the polymer. The system chosen for study is polycarbonate with oleic acid. An experimental technique involving contact angle measurements of a sessile drop as a function of stress is presented. A novel technique for contact angle measurements using refraction is also introduced.

Crystallization and Chemi-Crystallization of Recycled Photodegraded Polymers

J.R. White, I.H. Craig, C.K. Phua, May 2004

Injection molded bars have been made from blends containing recycled photodegraded polymers, then subjected to further ultraviolet (UV) exposure. Crystallinity measurements have been made at different depths from the exposed surface using X-ray diffraction and differential scanning calorimetry. Complementary information in the form of molecular mass distributions has been obtained using gel permeation chromatography, and the crystallinity results are interpreted in terms of molecular scission and photo-initiated molecular defects.

The Design, Construction and Operation of Equipment to Investigate the Response of Open, Coloured, uPVC Profiles to Solar Gain

D.M. Kelly, B.P. McMahon, T. Edgar, T. Foreman, May 2004

Laminated and dark coloured uPVC profiles, when exposed to sunlight during normal use, may occasionally suffer deformation. To gain a greater understanding of this phenomenon, a number of test rigs were developed to recreate the temperature increase, through the use of infrared heating elements, to simulate varying intensities of solar radiation.

Considerations for Relating Artificial Laboratory and Natural Outdoor Weathering Durability Testing

Henry K. Hardcastle III, May 2004

This paper reviews considerations for linking laboratory and outdoor reference exposure weathering durability data. Laboratory considerations include designing experiments and developing predictive functions using xenon arc devices. Reference exposure considerations include monitoring meteorological and irradiance exposure variables in Florida and Arizona. Exposure data is compared for polycarbonate.

Failure of Plastic Plumbing Products

Paul Gramann, Antoine Rios, Bruce Davis, May 2004

Failures of plastic components are being seen more often in industrial, household and commercial settings. Many of these failures involve the transport of water and cause significant damage when they occur. These failures can be caused by improper material specification, bad design, over loading or incorrect molding conditions. Issues such as chemical resistance, environmental deterioration, geometric sensitivity, temperature dependence and aging are at times overlooked.

Reliability of Joining Plastic Parts

Jan Spoormaker, May 2004

Critical items in designs of plastic products are joints. The paper will deal with a number of design aspects about designing reliable plastic products. It will combine the results from our research in the field of stress concentrations, orientation and weld lines around holes, embrittlement of polymers, adhesion and environmental stress corrosion. A number of failures in practice will be presented.

Performance Characteristics of a Styrene-Isobutylene Block Copolymer Produced by Living Cationic Polymerization Technology

David Marshall, Hideki Ishikawa, Hideki Kawai, Taizo Aoyama, May 2004

A completely saturated styrene-isobutylene based thermoplastics elastomer has been produced at the industrial scale for the first time. Triblock (SIBS) of Mw range 65,000 to 100,000 have been produced. Due to the saturated main chain of polyisobutylene, these products are superior in heat rersistance, gas barrier properties and damping properties.

Performance Enhancing Crosslinked SBR Masterbatches for Thermoplastic Elastomers

Manoj Ajbani, Chris Kiehl, May 2004

Masterbatches of crosslinked solution-polymerized styrene-butadiene random elastomers (XL-SBR) and polypropylene (PP) were prepared and used for enhancing the oil resistance, compression stress relaxation performance, lowering gloss, and compression set of styrene-ethylene/butylene-styrene (SEBS)-based thermoplastic elastomer (TPE) compounds. Enhanced performance was achieved when SBR partly or substantially replaced the SEBS component. Modification of SEBS compounds in the Shore A range of 45-85 with the crosslinked SBR is discussed.

New Soft EPDM Rubber Concentrate for Toll Compounding to Produce High Flow Thermoplastic Vulcanizates (TPVs) for Injection Molding Applications

Yundong Wang, Ryszard Brzoskowski, May 2004

New soft EPDM rubber concentrate can be used to produce thermoplastic vulcanizates (TPVs) with improved flow properties by toll compounding processes for injection molding applications. By adding various amounts of polyolefin plastics such as polypropylene homo polymer or copolymers, TPVs with different durometers and properties can be made easily using compounding equipment such as twin screw extruders or other mixing equipment with sufficient mixing capability.

New Thermoplastic Vulcanizates (TPVs) with Improved Processibility for Injection Molding Applications

Yundong Wang, Hua Cai, Ryszard Brzoskowski, May 2004

A new line of thermoplastic vulcanizates (TPVs) has been introduced by DSM Thermoplastic Elastomers for injection molding applications where UV resistance is critical. This new line of products, consisting of several grades with hardness ranging from 50 to 85 shore A in black color, shows superior flow characteristics and balanced properties meeting existing automotive material specifications. In this paper, we will discuss some of the features associated with this new line of products.

Extrusion Foaming of TPVs Using Water-Filled Polymers

Lorin H. Beaber III, May 2004

A novel, physical foaming agent, ‘water filled polymer,’ has been proven successful in producing low density foamed TPV profiles on standard single screw extruders. Extrusion processing parameters and physical properties (cell size, cell shape, tensile properties, specific gravity, compression load deflection, compression set, surface smoothness and water absorption) of TPV foamed profiles are reviewed. These results are compared to results from other types and forms of foaming agents used to produce foamed TPV profiles.

Numerical Analysis of Cable and Wire Coating: Interactions between Material Rheology, Flow Domain and Process Conditions

B. Toure, T. Baston, J. Fournier, P. Skabrahova, J. Vlcek, May 2004

Wire coating, based on the drag flow is a well-known process in the cable, wire or fibre-optic industry. It has been studied extensively in experimental and computational form over recent years. During the coating a polymer melt flows through an annular converging die and then meets a wire or cable that is usually traveling at high speed. This study is concerned with the numerical simulation of the complex flows that arise in the coating system with a thermoplastic polymer. The simulation study was performed in order to better understand the influence of the rheology parameters, the chosen processing conditions and the coating die geometry dimensions.

Measurement of Interfacial Instabilities during Coextrusion of LDPEs in Flat-Dies

Walter Kopytko, Martin Zatloukal, Jiri Vlcek, May 2004

This paper presents the results of some coextrusion flow studies for flat film on feed-block and multi-manifold flat dies for well characterised LDPE resins. The aim is to gain a better understanding of interfacial instability phenomena. The LDPE resins included materials of high and low viscosity as well as broad and narrow molecular weight distribution. The experiments involve the coextrusion of either the same materials in both layers or various combinations of materials with different viscosities. The focus of the work was to evaluate the effects of flow rate, viscosity and other material characteristics on the interfacial instabilities. The results from these experiments showed a possibility to locate areas where low or high frequency instabilities were created.

Compensating for Die Swell in the Design of Profile Dies

W.A. Gifford, May 2004

Because of the effects of die swell, the final shape of an extrudate is often substantially different from that of the exit opening of the die. As a result, the design of profile dies producing complex shapes often involves more than just “balancing” the die but also compensating for the effects of die swell. Typically, a successful design of such dies is only achieved through much “cut and try”. However, with the use of a fully three-dimensional finite element flow algorithm along with quick mesh generating capabilities, the usual cut and try involved in the design of many profile dies can be greatly reduced if not eliminated.This paper demonstrates how the effects of die swell can be compensated for in the design of profile dies. For profiles with one plane of symmetry, this includes compensating for the sideways translation of the extrudate as well as the change in shape that the extrudate experiences. Completely asymmetric profiles undergo a “twisting” downstream of the die. This twisting, which appears not to have been reported in the literature (at least for isothermal extrusion) is also accounted for here along with the change in shape that the extrudate undergoes.

A Survey of Manifold Designs for Flat Die Extrusion

Gary D. Oliver, May 2004

Feedblock Coextrusion is considered to have been commercialized with the Dow Chemical patents issued in 1971. As Cloeren and Nissel introduced their own Coextrusion technology, a common thread throughout all technologies was design of Coextrusion dies. For decades extrusion die manifold designs remained unchanged. The ‘90s ushered in new commercial manifold designs aimed at solving age old problems with flow uniformity, die deflection, and coextrusion performance. This paper will examine the progression of die manifold designs, their impact on extruded products, and their implications on future coextruded structures.

Real-Time Estimation of Crystallization Half Time during Blown Film Extrusion and its Influence on Final Film Properties

S. Cherukupalli, A.A. Ogale, May 2004

The development of crystallinity during film blowing of a linear low-density polyethylene at different processing conditions has been investigated using online Raman spectroscopy. The obtained trends for crystallization rates were explained using the concept of flow-induced crystallization. Further, direction dependent (machine and transverse) tensile properties were studied as a function of take-up ratio (TUR), inflation air pressure and cooling conditions. Based on the results for development of crystallinity at different conditions, the reciprocal crystallization half time was suggested as a likely essential parameter to formulate processing-structure-property relationships.