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.
The effect of simultaneous alignment of polyethylene (PE) lamellae and graphene nanoplatelets (GnP) on thermal conductivity of PE-GnP nanocomposites is investigated. Such alignment is achieved by subjecting the composite to mechanical strain. Alignment of PE lamellae is quantified using wide-angle X-ray scattering measurements while graphene nanoplatelet alignment is quantified via polarized Raman spectroscopy. Measurements reveal that thermal conductivity (k) of the composite increases at a faster rate with applied strain compared to pure PE pointing to the beneficial effect of GNP alignment on k enhancement. At the maximum applied strain of 400% and using 10 wt% GnPs, a composite thermal conductivity of 5.9 W/mK is achieved representing an enhancement of ~12-fold over the unoriented pure polymer (k~0.5 W/mK), a ~4-fold increase over the unstretched filled polymer (1.5 W/mK) and a ~1.75-fold increase over the unfilled oriented polymer (3.5 W/mK)
This paper reports the importance of resin selection on the pore formation of semicrystalline homopolymer polyethylene (PE) films by cold stretching at room temperature and the subsequent hot stretching at an elevated temperature. Five different PE resins with various crystallinities and molecular weights were evaluated by using differential scanning calorimetry (DSC), conventional gel permeation chromatography (GPC), light-scattering GPC, and X-ray techniques. Mercury porosimetry was employed to characterize the pore structure of PE porous films, and water vapor transmission rate (WVTR) was used to determine the breathability of these porous films. The result show that high crystallinity (> 0.96 g/cm3), high molecular weight distribution (Mw/Mn > 6) and high z-average molecular weight Mz (> 500,000) of PE resins are critical for the pore formation in PE films. The WVTR value of PE porous films can be as high as 345 g•mil /(100 inch2•day).
A new polymer processing technique called Melt-Mastication (MM) is presented as a useful method to fabricate isotactic polypropylene (iPP) with improved thermal and mechanical properties. Melt-Mastication is a low temperature mixing technique that subjects molten iPP to chaotic flow at temperatures between the melting and crystallization transitions thereby promoting flow induced crystallization. The resulting iPP assumes an unusual morphology that is highly crystalline (57% crystal volume fraction), melts at a temperature 10.3 K higher than conventionally processed iPP, and demonstrates melt memory after annealing at 200 °C. The crystal morphology by polarized optical microscopy and atomic force microscopy appears to be comprised of largely disorganized lamellae, with possible ordering in local regions. Melt-Masticated iPP demonstrates greatly improved compressive modulus (+77%) and strength (+40%). The enhanced thermal and mechanical properties are attributed to aspects of the crystal morphology produced by MM.
Z. Benrabah and Anna BardettiNational Research Council Canada Automotive and Surface Transportation Research Center75 de Mortagne Blvd., Boucherville, QC J4B 6Y4, CanadaE-mails: email@example.com; firstname.lastname@example.orgABSTRACT: BlowView is an engineering 2.5D finite element simulation software, developed at NRC, dedicated to simulate conventional extrusion blow molding, twin-sheet extrusion blow molding, stretch blow molding and thermoforming processes. This versatile blow molding simulation software is highly automated, flexible and user-friendly, yet allows users in-depth analysis capabilities for a wide range of materials, including optimization and permeability. Extrusion blow molding, and twin-sheet extrusion blow molding, are extensively used in manufacturing automotive plastic fuel tanks (PFT). These processes consist of three main phases: parison/sheet formation, inflation and part cooling and solidification. The parison/sheet formation is the most critical stage, as the final dimensions and mechanical performance of the PFT is directly related to the initial extrudate shape, which often requires the use of advanced die shaping technologies such as: Vertical Wall Distribution System (VWDS), Partial Wall Distribution System (PWDS), Die Slide Motion (DSM), and/or a combination of all three. These technologies are all available in the BlowView software, and can be handled simultaniously and synchronized with the machine programming points. In order to predict the extrusion with sag and swell, BlowView uses a hybrid approach that couples fluid mechanics to represent the die flow, with solid mechanics to represent the parison/sheet behavior outside the die, and a phenomenological swell model to capture the die geometry effect. This approach permits avoiding instability issues encountered by traditional fluid mechanics, especially at high Weissenberg numbers. After extrusion, the parison/sheet inflation is predicted tacking into account all mold components and their respective position and displacements. The modelling capabilities of NRC’s BlowView software will be presented based on using an industrial case study of a PFT. Permeability and optimization results will be also illustrated.
The ability of a gasket to maintain sealability over a long period of time is the primary consideration for pressure vessel and piping designers. While service conditions such as temperature, internal pressure, gasket stress, and the caustic nature of the transport media are all important parameters, factors such as the gasket material, gasket dimensions, and flange torque procedure have generally been viewed as the most influential. Viscoelastic gaskets are attractive as intermediate layers between bolted flanges because they conform to the inherent imperfections between mating flange faces. They display time-sensitive relaxation responses over the long term. Next generation gaskets, termed EPX and manufactured by Garlock, have been designed with a dual-face, raised honeycomb pattern to confer more rapid stabilization compared to existing non-textured products. Historically, a re-torque is conducted at approximately 24 hours after initial torqueing. The consequence of the secondary load is a significant boost in the load retention response, especially for more compliant materials. Preliminary studies reveal that the viscoelastic properties exhibited by ceramic-filled PTFE materials can achieve a nearly identical post-re-torque response with a one hour dwell in place of the day-long dwell. The gaskets having a textured-style (i.e., EPX), however, were found to require no re-torque whatsoever. Gasket efficiency, %, defined in earlier studies, is used to measure both stress relaxation and load carrying capability of gaskets. A design of experiments (DoE) approach is applied to characterize the factors that influence load relaxation response of the both candidate (EPX) and existing (Legacy) gasket styles. Experimental data are used to develop modeling constants associated with the Burger viscoelasticity model. With the use of finite element modeling, stress distributions within the gasket are revealed. The collection of efficiency measurement methods, approach to re-torque optimization, and modeling convey a novel framework that designers can invoke to facilitate improved flange performance.
Susceptibility to visible mar damage of polymers significantly affects their aesthetic appearance. Quantitative evaluation of mar damage on polymer surfaces is highly desired for the design of mar resistant polymers and structures. In this study, an effective mar testing and evaluation methodology is introduced that is capable of evaluating mar damage for white and transparent thin polymer films, which are the most difficult colors for mar detection. Here, the mar damage is imaged and evaluated based on the contrast differences between the marred area and virgin background along the mar path. It is found that mar contrast results obtained by this method show good correlation with the assessment by human eyes. This methodology provides a quantitative measure of mar that correlates well with “human perceptions through visualization”. This method of mar surface analysis can be a potential methodology employed to investigate the fundamental structure-property relationship between polymer material properties and mar behavior.
A new technology from Braskem extends the use of clear polypropylene to thermoformed containers for refrigerated conditions. Typical clear polypropylenes have poor impact properties at low temperature. Polypropylene impact copolymers have greatly improved impact properties compared to polypropylene homopolymers and random copolymers but are opaque. This work explores what causes haze in thermoformed polypropylene impact copolymers, how that haze can be improved, and how Braskems new impact copolymer compares to conventional impact copolymers, random copolymers, and with blends.
The influence of processing parameters on barrier properties of nanocomposites was investigated. Elastomer nanocomposites consisting of nitrile rubber latex and clay nanoparticles were prepared by three techniques: Chemical dissolution, melt-mixing in an internal mixer and extrusion. Resistance to methanol were assessed using gravimetric method. It was observed that extruded material exhibited the highest chemical resistance. Small-angle X-ray scattering patterns indicated that this improvement was due to nanoparticle orientation in the structure. With the other techniques, a neat enhancement of solubility was spotted over the pure rubber. X-ray diffraction results related this aspect to the delamination of the clay nanoparticles. Moreover, when melt-mixing was adopted, improvements were also recorded proportionally to the increase of the torque as well as the residence time inside the mixer.
A system comprising an antimicrobial compound, an interfacial agent and a vinyl acetate copolymer augments an oxygen barrier package to provide a viable active packaging solution to extend the shelf-life of poultry products. Fresh poultry is a perishable product with a short shelf-life. An antimicrobial-incorporated active packaging film can extend the shelf-life of poultry products and reduce retail and customer shrink substantially. This work provides an overview of the various factors that affect the shelf-life of poultry products, discusses the role of potassium sorbate as an effective antimicrobial agent, and elucidates its incorporation into and release kinetics from the package’s food contact layer.
In this paper we present a brief review of large body of publications related to conformability of multilayer system. Conformability of thin film with a curved geometry substrate on which the film is applied is commonly manifested in formation of blisters, wrinkles and other forms of delamination. The delamination is driven by elastic energy of thin film associated with the film deformation required by film application. A simple method of observation and quantitative characterization of delamination and its evolution in time is proposed. A continuous growth of delamination over many hours is observed on a number of plastic films. The time dependency of delamination results from an interplay between the stress relaxation within the film and viscous flow of adhesive that support the film deformation. Thus, the conformability of multilayer system is characterized by a combination of the film rigidity and relaxation as well as the time dependent strength of adhesive. A design of conformability tester, measurements of delamination growth, modeling of the observed process and an algorithm for quantitative characterization of delamination are presented. A practical application of the conformability tester is illustrated by ranking of a number of thin plastic films with respect to conformability.
This study demonstrates the charge storage and electromagnetic interference (EMI) shielding performance of thermoplastic polyurethane (TPU) based nanocomposites containing various amounts of conducting multiwall carbon nanotubes (MWNTs). The functional properties of TPU nanocomposites were systematically designed by generating various degrees of interconnected networks of MWNTs in the TPU matrix. The dispersion and interconnected networks of MWNTs were assessed using rheology and direct current (DC) conductivity measurements. An enhanced charge storage (i.e., high real permittivity) and extremely small loss (i.e., loss tangent) were achieved at a low fraction of MWNTs (5.0wt%) in X-band frequency, whereas, large elimination of incoming microwave radiation was achieved via highly interconnected networks of dielectrically lossy MWNTs.
Markets trends of cost reduction, sustainability & down-gaging drive the need for new and improved products. Development of such products requires a look across the entire value chain – an Asset to Market look. An emerging trend in the materials space is related to collection and management of data that enables knowledge creation. Management of this data and the knowledge generated is critical to accelerating research. This talk will focus on what is required for rapid product development, launch and knowledge transfer across a global organization to sustain market leadership. Key examples will be presented and will cover these trends.
Melt-mixed polypropylene (PP) composites with singlewalled carbon nanotubes (SWCNTs ) were used as thermoelectric materials which can convert a temperature difference between the two sides of the material into a thermovoltage. The effect of SWCNT content on Seebeck coefficient (S), electrical conductivity, and power factor was studied. In order to enhance these values for p-type composites, several strategies were applied. These involve (a) variation of the SWCNT modification, (b) incorporation of a high S copper oxide, (c) variation of melt-mixing conditions, and (d) addition of an ionic liquid. To generate n-type composites, additives like polyethylene glycol (PEG) and a non-ionic surfactant polyoxyethylene 20 cetyl ether were simply added during the melt-mixing procedure, inducing a switching from positive to negative S values in the pressed films. Finally, two prototype thermoelectric generators using both, p- and n-type PP based materials, could be manufactured.
We test whether the electrical conductivity of copper-polystyrene composites can be improved by adding a metal solder alloy during blending. Copper-in-polystyrene composites prepared by melt-blending have poor electrical conductivity. Addition of a flux (a compound commonly used in soldering) during blending is found significantly to improve the conductivity. A further large increase in conductivity was obtained by adding molten solder during composite preparation. The mechanism of this improvement is that the solder bonded the copper particles together into large aggregates that percolated throughout the sample. We examined the effects of the volume ratio of solder to copper particles on electrical conductivity and the composite morphology. If sufficient solder was added, the copper particles become welded together by the solder to form a self-supporting metal network, and a conductivity of ~500 S/m was realized at a metal loading of only 20 vol%. With insufficient solder, large but non-percolating structures of solder-bound copper particles appeared, and the corresponding blends had lower conductivity. While most of the samples were prepared by hand-blending, we verify that the same approach of improving conductivity can be applied using a Brabender batch mixer.
This paper will first address the general challenges of dispersing discrete multiwall carbon nanotubes in polymers followed by detailed morphological and tensile deformation studies of polyvinylidene fluoride blends with carbon black and discrete carbon nanotubes, commercially available as MOLECULAR REBAR®. The specific carbon nanotubes employed here are about 13nm in diameter and about 900nm in length. In thermoset, or materials which fail in a brittle mode, the discrete carbon nanotubes show improved crack initiation and propagation resistance via a crack pinning mechanism. In ductile, or elastomeric materials the tubes are seen to align with the principal stretch direction. In semi-crystalline materials the carbon nanotubes may act as crystal nucleators, but are small enough to be able to be excluded from crystal domains as they form. This crystallization behavior with discrete nanotubes results in quite complex structures, highly dependent on fabrication processes. The ability to control the structure and placement of discrete carbon nanotubes creates new opportunities for advanced materials.
The use of a self-sterilizing package that can sterilize its contents ‘on-demand’ when triggered by specific stimuli (such as ultraviolet energy (UV)) can provide a novel method for medical device sterilization that is faster, safer and more cost-effective than conventional methods in use today. We describe the development of a self-sterilizing package which can release ClO2 gas as a sterilant when triggered with UV light to sterilize medical devices packaged inside. We discuss the scheme of operation of such a package, gas release characteristics, sterilization efficacy, post-sterilization residuals and material-sterilant compatibility. We demonstrate that a sterilization assurance level of 10-6 can be achieved within such a package.
In an effort to become more “green” in the plastics world, engineers are developing unique products by adding biomass materials to create bio-friendly plastics. The biomass additives may have a different aspect ratio, size, compressibility or density than the pellets and powders but they all must come together in a uniform, consistent, reliable flow into the extruder. Understanding the implications to the handling of adding a new biomass material to a blend is critical for the success of the product. Taking a scientific approach to understanding the flowability of a component and blend is critical to ensuring a successful outcome. Often, this approach results in either making a change to the equipment that the material is handled in to support the new blend, or to making a change in the material or blend (or the conditions at which it is handled) to flow through the existing equipment.
The gaining importance of sustainability in recent years has also led to a closer look on lightweight materials such as fiber reinforced plastics. However, these materials usually pose a challenge in application. Purposeful virtual engineering and prediction is part of it. A new approach allows the reliable prediction of discontinuous fiber reinforced plastics based on integrative simulations while taking local fiber orientation and local fiber length into account. The results obtained with this method already show an improvement in prediction of simple part geometries. Further gain in quality is expected by complex parts where fiber orientation distribution and fiber length distribution spread more widely.
Vehicles confront damages and breakdown caused by various factors under working condition. The most common type of the failure is scratch. External particles such as small pebbles pop up and cause physical damages on the surface of the vehicle. It is not desirable in the aesthetic point of view. Clear-coat layer, which is on the top of the painted surface, is directly affected by scratch. To evaluate the scratch characteristics of the coatings of passenger vehicles, we conducted scratch tests using ASTM D7027 standard. Through the experiments, we obtained scratch properties of various coatings. Using the results, scratch-resistant clear-coat will be developed.
Three different thermoplastic polyester materials were evaluated to investigate the connection between the structure of the materials and their properties. Three materials representing distinct characteristic structures were selected to contrast the results. The resins evaluated included polycarbonate, with carbonate ester functionality; poly(ethylene –co- 1,4-cyclohexanedimethylene terephthalate), a poly(ethylene terephthalate) copolymer; and poly(ethylene naphthalate), with two condensed aromatic rings. The characteristics tested as part of this work included tensile properties to illustrate the short-term mechanical attributes, glass transition temperatures to represent the thermal response of the materials, and creep modulus to demonstrate the time dependency.
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