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 Clay Incorporation on the Broadband Dielectric Properties of MWCNT/Polyvinylidene Fluoride Nanocomposites

Maryam Khajehpour, May 2013

This study reports on the effect of clay addition on the broadband dielectric properties of multi-walled carbon nanotube/Polyvinylidene Fluoride (MWCNT/PVDF) composites, i.e., 101 – 106 Hz. The three-phase PVDF/MWCNT/Clay composites with different loadings of MWCNT and clay were prepared employing melt mixing method. Characterization techniques, such as X-Ray diffraction and transmission electron microscopy were employed to examine the crystalline structure and morphology of composites, respectively. The dielectric spectroscopy showed that introducing clay into the MWCNT/PVDF composites at the critical MWCNT concentration improved dielectric properties tremendously. For instance, incorporating 1.0 wt% clay into the PVDF/MWCNT composite at the critical MWCNT loading, i.e., 0.5 wt% MWCNT, increased dielectric permittivity significantly (670% at 100 Hz). Furthermore, it was observed that the addition of clay reduced the dissipation factor considerably (68% at 100 Hz).

Fracture Behavior and Mechanical Property of Jute-Glass Hybrid Composite

Ryuiti Nishida, Zhiyuan Zhang, Yuqiu Yang, Hiroyuki Hamada, May 2013

Jute fiber has gained extensive use in recent years due to its advantage in environmental protection, low cost and low density. However, the limitation of its low mechanical property affects its application. Because of this reason, jute-glass hybrid fiber configuration was considered as an improvement. In this study, 2 kinds of jute-glass hybrid fiber configuration were employed to investigate the mechanical property and fracture behavior in different configuration. At the same time, different plies and different angle of the composite were analyzed. It was found the composite fabricated by B type fabric expressed better properties both on tensile and bending test. Scanning electron microscope observation was also found excellent matching between jute fiber and glass fiber in B type composite.

Low Percolation Threshold and Improved Electromagnetic Interference Shielding Effectiveness of Polypropylene/Carbon Fiber Composites Through Foaming

Aboutaleb Ameli, Peter U. Jung, Chul B. Park, May 2013

Injection molding of solid and foamed polypropylene/carbon fiber (PP-CF) composites with different carbon fiber contents (0-20 wt. %) was conducted. ~ 25% void fraction in the foamed composites was achieved using supercritical N2 as the environmentally benign physical blowing agent. The effects of foaming on the percolation threshold, through-plane electrical conductivity, permittivity and electromagnetic interference shielding effectiveness (EMI SE) were investigated. Compared to the solid composites, in addition to the reduced weight of the polymer matrix (25%), introduction of foaming lowered the electrical percolation threshold from 17 wt. % to 11 wt. %. The relationship between the structure and electrical properties was explained in terms of the changes in the fiber orientation and skin layer thickness. At 15 wt. % CF content, the foamed composites yielded an EMI SE of about 25 dB, significantly higher than that of the solid composite (13 dB) with the same CF content. In both solid and foamed composites, the dominant EM attenuation mechanism was found to be wave absorption not reflection. The results reveal the application of injection foam molding technology to manufacture lightweight conductive products with lower fiber content and enhanced EMI SE.

Thermal ageing performance of novel Ultrol® Nuclear 60 year Cables.

Elliot Lee, May 2013

Wire and Cable manufacturers generally qualify products for class 1E application by envelope type testing to user specifications and environmental conditions recommended by IEEE standards 323- 1974 and 383-1974. Early cable qualification required only radiation in 1960s. 1960s and early 1970s added thermal aging to ICEA requirement. However the ageing requirement was very minimal (1 week @ 121°C). The long term ageing requirement was not as nearly stringent as present until IEEE 383- 1974 was added to standards. To determine the ability of samples to withstand normal operation, IEEE 383- 1974 introduced ageing samples to “End of Life” condition. Samples were heat aged to a timetemperature condition in excess of 40 years of service life. Federal law and regulation recently allowed electric companies to renew their nuclear plants’ operating licenses for 20 years beyond their original, 40-year license term, which in turn triggered IEEE standard 383-2003 to govern minimum requirements to meet 60 years. General Cable Corporation, GCC simply in this paper, recently completed qualification programs. The major milestones in the development included (a) product life improvement of our established products, Ultol® products, from 40 yrs to 60 yrs. (b) introduction of Ultrol® medium voltage power cable with 60 year life. Cable constructions tested were 600V instrumentation cables, 600V power cables, 600V control cables, 2000V power cables and 15kV Power cables. This paper presents Arrhenius thermal aging data collected for materials used in the qualification programs using IEEE 101-1987 as basis confirms that a 90°C conductor temperature has a life in excess of 60 years.

Fracture Toughness Of A Medical Grade Ultra High Molecular Weight Polyethylene Using A Single Specimen Method

Christopher Brignola, Ahamed Shabeer, Paul Guthorn, Gerald Zamiski, May 2013

Ultra-high-molecular-weight polyethylene (UHMWPE) has been extensively used in total knee arthroplasty because of its superior physical and mechanical properties. Fracture toughness and fatigue crack growth of UHMWPE has been widely accepted as critical to the structural performance of orthopedic implant bearings. Literature search revealed that the most commonly used techniques to determine the fracture toughness of UHMWPE material are the multi-specimen and single specimen normalization method. In this paper, a novel single specimen method was used to determine the resistance to fracture of GUR 1050 material during a stable crack extension. The crack length extension was obtained using digital microscopy and photogrammetric methods. The test results obtained were compared to the other multi-specimen method data published in the literature.

Feedback Control and Disturbance Rejection in Polymer Extrusion

Diane Haberbusch, Zhiqiang Gao, May 2013

Feedback control is important for commercial manufacturers of polymer compounds, especially in the extrusion process. The inability to respond to disturbances in the extrusion process results in production of off-specification product and down-time. Due to the complexity of the system, it is difficult to accurately model an extrusion process. The technique of active disturbance rejection control (ADRC) requires a small amount of knowledge of a system, and is effective over the traditional proportional integral derivative (PID) controller. ADRC is currently in use in programmable logic control code on multiple production lines of polymer hose extruders for barrel zones temperature control.

Broadening of the foam processing window of polypropylene in extrusion foaming via the incorporation of CO2-philic nanofibers.

Ali Rizvi, Alireza Tabatabaei, Reza Barzegari, Chul Park, May 2013

Tensile stress growth during extensional flow is enhanced in linear polypropylene (PP) via the incorporation of chemically modified polytetrafluoroethylene (PTFE) nanofibers which demonstrates strong affinity for carbon dioxide (CO2). Foam extrusion of the PP nanocomposite using CO2 as the blowing agent reveals a three orders of magnitude increase in cell density, a ten-fold increase in expansion ratio, and a marked broadening of the foaming window with respect to when no nanofibers were added. The improvement in foaming ability is attributed to the increase in strain-induced hardening and the ability of the nanofibers to act as a reservoir of the blowing agent and facilitate the foaming process.

Solid-State Batch Processing and Structure of Nano-cellular Thermoplastic Polyurethane foams

Mehdi Saniei, Nemat Hosseiny, Amir Ameli, Davoud Jahani, Chul B. Park, May 2013

Two step solid-state batch foaming of TPU/Clay nano-composite as well as melt processed neat TPU was conducted by using CO2 as the physical blowing agent. Nanoclay was dispersed into the TPU by using a twin screw extruder in order to promote cell nucleation. The samples were saturated under CO2 pressures of 30 MPa at room temperature. Subsequently, the solid state foaming step was carried out by immersing the saturated samples in a silicone oil bath at different temperatures around the first thermal transition of the considered nanocomposites assigned by differential scanning calorimetry. A scanning electron microscopy was used to examine the structure of the foams. Depending on the combination of processing parameters, a wide range of cellular structures was achieved. The cell size ranged between 10 ?m and 400 nm and the cell density was between 109 to 1013 cells/cm3. An optimum foaming time and temperature were found wherein the smallest cell size with highest cell density could be produced. This CO2-TPU/Nanoclay system provides a unique frame in which the bulk properties of nano-cellular and microcellular structures can be compared.

Structure-Property Relationships in a New Family of Bio-Based, Compostable Blown Films

Raj Krishnaswamy, May 2013

This paper is concerned with the influence of processing conditions on microstructure development and performance of a new family of biobased and compostable blown film products based on Mirel? PHB copolymers (product referred to as B5009). The unique combination of performance attributes of B5009 blown films including biobased carbon content and compostability, along with an excellent balance of tear propagation resistance, puncture toughness and tensile strength will be highlighted. The potential applications of the subject film, that has similar to superior mechanical properties compared to LLDPE, will be reviewed. The synergistic advantages that can be garnered with multi-layer film structures (through coextrusion with other polymers) will also be discussed.

Electrical Properties of Polypropylene Composite Foams Reinforces with Long Stainless Steel Fibers

Aboutaleb Ameli, Mehdi Saniei, Davoud Jahani, Chul B. Park, May 2013

Conductive thermoplastic composite foams are a novel class of materials that can be an excellent candidate for producing cost-effective and lightweight products. In this work, electrically conductive polypropylene (PP) foams of various densities filled with varying contents of long stainless steel fibers (SSF) were successfully fabricated. The foaming of composites was achieved using a batch process and supercritical CO2 as the environmentally benign physical blowing agent. The PP-SSF foams maintained high level of electrical conductivity over a wide range of density reduction, depending on the initial loading of SSF. To better understand the conductivity behavior of solid and foamed composites, statistical percolation analysis was conducted. The analysis showed that the conductivity change with the foam density followed the percolation power law. The critical SSF concentration, calculated based on the sample’s final volume was 0.37 and 0.28 vol.% for the solid and foamed composites, respectively. In the current PP-SSF system, foaming decreased the weight up to ~70-80 % and lowered the percolation threshold by about 25%.

Determination of Specific Aluminum Flake Characteristics in Injection Molded Plastic through Colour and Effect Measurement

Sam Cauchi, Rae L. Roby, May 2013

An attractive alternative to painting plastic parts with formulations that include metallic pigment has become the inclusion of metallic flake directly in the resin. One of the challenges associated with including metallic flake directly in the resin is that current molding technology limits our ability to control flake distribution during the manufacturing process and achieve a uniform appearance. For many end use applications including automotive interiors, a low-quality appearance is not acceptable; thus, the economic benefits of this method have historically remained out of reach. As a first step towards achieving a uniform finish in an injection-molded part with embedded flake, a method must be established to evaluate the uniformity of colour and flake effect in the end product. Recent developments in colour and effect measurement technology now allow for quantitative characterization of both metallic colour and flake effect. With this method in place, it is possible to begin optimizing all those parameters that affect flake distribution and quantify the customer’s visual impression. This paper describes this measurement method and demonstrates the method’s ability to discriminate between different effect pigments.

High Throughput Methodology for Mechanical Testing of Polymeric Films

Sara Reynaud, May 2013

Assessment of mechanical properties of thin polymer films under high speed impact is often nontrivial. Standard dart drop tests are not suitable for thin samples, nor does it provide information on stress- strain relationship under load. Other techniques such as tensile/flex and nanoidentation testing can only be performed at relatively low strain rates. A High Throughput Methodology for Mechanical Testing (HTMECH) of freestanding thin films under high speed loading is used in this work. The main advantages of this technique are the high instrumental sensitivity, ability of rapid screening, and simplicity of data analysis. Toughness properties of thin films were measured by HTMECH and compared with dynamic mechanical analysis (DMA) data. The correlation between the two techniques has been established and discussed.

The Effect of Hydroxyl-functionalization on the Structure and Properties of Polypropylene

Sahil Gupta, T.C. Mike Chung, Robert A. Weiss, May 2013

Hydroxyl-modified polypropylenes (PPOH) with side chains containing OH groups were synthesized by the copolymerization of propylene with undecenyl-oxytrimethylsilane monomer. Copolymers with OH concentration ranging from 1.3 to 3.9 mol% were produced and their properties compared with unmodified polypropylene. The presence of intermolecular H-bonding between the OH groups affected the base polypropylene structure as well as its thermal and rheological properties. As predicted by Flory’s theory of melting point depression in copolymers, the melting point reduced with increasing [OH]. While the crystal structure remained unaffected, the crystal size reduced by approximately 15%. Crystallinity for PPOH polymers was also reduced by as much as 40% because of the hindrance to the ordered packing of backbone chains into the lamellar structure. On the other hand, the rheological properties such as the melt strength and the elasticity increased for the PPOH polymers. PPOH with only 3.9 mol% OH groups displayed a gel-like rheological behavior suggesting the formation of a weak elastic network in the melt.

Slow Crack Growth in High-Density Polyethylene Part 1: Experimental Observations

Haiying Zhang, Alexander Chudnovsky, Zhenwen Zhou, May 2013

This paper aims to simulate slow crack growth in high-density polyethylene by using Crack Layer Model. We first derived the analytical approximations of stress intensity factor and crack opening displacement for finite geometries using close form solution of a semi-infinite crack and the numerical solutions for corresponding geometries. We then use the approximate solutions to assess the size of the process zone accompanying the crack, slow crack growth rate and mechanisms as well as the lifetime in brittle fracture of high-density polyethylene.

Virtual Prototyping in Rubber Seal Manufacturing and Testing

Phillipe Klein, Frederic Fradet, Ashutosh Srivastava, Hossam Metwally, Peiran Ding, May 2013

This case study highlights the entire design and testing process, virtual prototyping, of an extruded automotive aluminum reinforced rubber seal. First, the expected deformation of two similar shapes of the rubber seal will be analyzed. The design that will provide the required deformation, contact pressure, and reaction force, and hence better sealing performance, will be chosen for production. Two rubber material models are considered for the non-linear plain stress analysis, one being rate dependant (more realistic) and one is rate independent. The difference in behavior of the seal due to the material model used is highlighted. Then, to obtain the required extrusion die profile that will be used to manufacture that seal shape, the process of inverse die design will be implemented. In this procedure, the final seal cross section is used to obtain what the required die lip shape should be so that after die swell the final profile is obtained. Finally, to verify the entire die performance, detailed flow analysis is carried on the entire extrusion die and the flow balance is verified.

Constant Temperature Embossing (CTE): Process Analysis

Ramasubramani Kuduva Raman Thanumoorthy, Donggang Yao, May 2013

The goal of this paper is to analyze the Constant Temperature Embossing (CTE) process by constructing a process model to determine the change in material parameters during the process. The process model is developed by combining the non-isothermal crystallization kinetics and suspension based rheological models. A shift factor is determined from the non-isothermal crystallization kinetics to predict the crystallization behavior at temperatures where the properties are difficult to measure. A suspension based rheology model is chosen to represent the change in viscosity of the polymer during the process as the increase in particle concentration. The thermal and rheology models are then merged by considering certain key assumptions, and a process model to determine the change in material properties during the CTE process is constructed.

Impregnation Process for Fiber Hybrid Braided Reinforcement Thermoplastic Plastic

Mitsurou Takagi, Toshihiro Motochika, Kazufumi Nakazawa, Toshikazu Uchida, Akio Ohtani, Asami Nakai, May 2013

The purpose of this study was to clarify the process of impregnation for hybrid braided FRTP. First, intermediate material was made and investigated. Second, braided fabric with some structure was made and by these braided fabric, moldings with some molding time were molded. After investigation of impregnation-property and mechanical property, it was clarified that essential molding time and the gradient of decreasing in un-impregnation ratio to molding time of BY and MEY were different according to the materials and to reduce un-impregnation area was important to improve mechanical property.

Friction Coefficient Measurements Using a Timoshenko and Van Karman Device: Bulk Polymers

Abdullah A. Alshaya, Sean Petzold, Melih Eriten, Tim Osswald, May 2013

In this paper, an alternative method to using the pin-on-disk tribometer was used to measure the kinetic friction coefficient of polymers. This method is based on the principle of the Timoshenko and Van Karman device [5]. Compared to the pin-on-disk tribometer, this method is more cost effective and does not require precise manufacturing. Experiments were conducted to measure directly the period of oscillations from which the friction coefficient can be evaluated. Period is measured by IR timing device and Laser Vibrometer (LV). Three materials are tested, namely polyacetal (POM), Acrylonitrile butadiene styrene (ABS), and Polymethyl methacrylate (PMMA). The effects of normal force and sliding speed on the friction coefficients of these polymeric contacts are studied. Results show that both the normal force and the rotation speed of the rollers influence the friction coefficients. These observations conflict with the classical laws of friction.

Comparison of the Flow Performance Between Internal and External Deckling in Flat Film Die Systems

Olivier F. Catherine, May 2013

Deckles are devices useful to adjust the slot width of extrusion dies, and hence the extruded product width. There are basically two types of deckles: (i) internal deckles are made of components placed inside the die flow channel to block the flow channel to a specified width upstream the die lips, and (ii) external deckles typically comprise blockage devices positioned directly on and external to the die lips, at the exit orifice. To understand the fundamental differences in flow performance between the two technologies, 3D Computational Fluid Dynamics (CFD) models were built. A comparison of the original die width to the internally and externally deckled dies is carried out by evaluating the flow characteristics such as velocity uniformity at the die exit and Residence Time Distribution (RTD) in the die flow channel. The flow models show that the performance of an internally deckled die is close to that of a non-deckled die, while the external deckle system results in non-uniform flow distribution and broad RTD due to the occurrence of a large stagnation area upstream of the external deckle.

Decrosslinking of crosslinked HDPE via ultrasonically aided extrusion

Keyuan Huang, Isayev Avraam, May 2013

Decrosslinking of crosslinked HDPE (XHDPE) at various processing conditions is performed by means of ultrasonic single and twin screw extruders. Without the imposition of ultrasound the high flow rate in the single screw extruder was impossible to achieve due to an excessive torque. Gel fraction, crosslink density, dynamic properties and mechanical properties of the virgin HDPE and XHDPE and decrosslinked XHDPE and is measured. Significant decreases of gel fraction and crosslink density of decrosslinked XHDPE was observed indicating the occurrence of decrosslinking. A universal linear relation between the normalized gel fraction and the normalized crosslink density is found, regardless of the type of extruders and processing conditions. The decrosslinking effect induced by ultrasound increased with the ultrasonic amplitude. The increase of amplitude led to a decrease of the complex viscosity and storage modulus and increase of the loss tangent of decrosslinked XHDPE. The viscosityfrequency curves were well described by a power-law model with the consistency and power law indices linearly increasing and decreasing with crosslink density, respectively. The dynamic characteristics of sol indicated an increase in polymer chain branching due to decrosslinking effect, as detected by an increase of the activation energy of viscous flow. The mechanical properties of decrosslinked XHDPE showed a strong dependence on the type of extruder and a no trend on processing conditions due to molecular complexity of the decrosslinked XHDPE.