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
Rotational Molding of Polyolefin Plastomers and TPOs
Wenqing Wang, Marianna Kontopoulou, May 2002
The present research aims at examining the rotational molding characteristics of metallocene catalyzed Polyolefin Plastomers (POPs) and Thermoplastic Olefins (TPOs). The latter are blends of polypropylene with POPs. The rheological and thermal properties of two grades of POPs and a TPO in powder and micropellet form have been tested and their processability has been assessed by conducting sintering and rotomolding studies. Depending on their formulation, POPs can be successfully rotomolded and excellent properties can be obtained. Rotomoldable TPO resins should have low zero shear viscosity and low melt elasticity.
Rotational Moulding of a Dicyclopentadiene Reactive Liquid Polymer
N. Corrigan, E. Harkin-Jones, R.J. Crawford, May 2002
To date, powdered resins remain the main form of raw material used in the rotational moulding industry. However, in recent years interest has grown in the use of reactive liquid polymers as alternative materials. Reactive liquid systems offer the potential of engineering polymers which have previously proved difficult to rotomould in the powdered form, as well as significant reductions in cycle time. This paper investigates the potential of Dicyclopentadiene as a rotomoulding material. Rheological analysis and uniaxial moulding techniques, which have been used to develop a suitable material formulation for use in the rotational moulding process, are described.
Routes to and Properties of Intercalated Silicate Nanocomposites
Adam S. Zerda, Terrence C. Caskey, Alan J. Lesser, May 2002
Recent work in layered silicate nanocomposites has focused on the exfoliated morphology wherein the clay platelets are homogenously dispersed within the matrix polymer with no registry between silicates. The intercalated morphology, however, wherein individual platelets retain strong registry, is thought to have the potential for properties unavailable to the exfoliated morphology, including flame retardance, fracture toughness and true polymer-ceramic behavior. Routes to the manufacture of such hierarchical laminates and their potential property enhancements are discussed.
Scratch and Abrasion Resistant UV-Topcoats for Plastics Using Colloidal Silica Acrylates - Impact of Size, Size Distribution and Silica Loading on Coating Properties
Vu Can, LaFerté Olivier, Eranian Armand, Kelly Michael, May 2002
The impact of particle size, size distribution, and silica loading on film properties of UV-cured hybrid organic-inorganic thin composites was investigated in this work. Commercial silica organols of hexanediol diacrylate monomer (HDDA) containing high concentration of monodisperse silica nanospheres (13, 25 and 50 nanometers) were cured with a polyester tetraacrylate (PEA) to give transparent nanocomposites. Silica loading can be as high as 40% silica. The composite coatings can be efficiently used as topcoats to protect polymer substrates against scratch, abrasion and chemicals.Dynamic mechanical thermal analysis (DMTA) measurements showed that complex modulus (E*) increased and loss tangent (tan?) decreased with small particle size and high silica content, but the dynamic glass transition temperature (Tg) was unaffected by size and size distribution.Coatings with mixtures of 50 and 13 nm particles at 75/25 weight ratio obeyed to volume packing theory and gave the highest values of E* and tan?. Resistance to abrasion and friction were more effective with large particles, while gloss was highest with small ones. These properties were best seen when silica content is superior to 15 % where strong interactions at the silica-polymer interface and particle/particle were detected.AFM observation showed that the surface of the coating was well covered with silica particles, protecting it from aggressive physical and chemical attacks. Examples of transparent hard coatings protecting various plastic foils or sheets against scratch and abrasion will be shown during the presentation.
Screw and Barrel Design for Grooved Feed vs. Smooth Bore Extruders
Johannes Wortberg, May 2002
Grooved feed extruders (GFE) for quality production at lowest costs require screw and barrel designs capable of achieving gradual increases in pressure along the extruder and low friction in the feed section. Barrier-melting and mixing zones must be adapted to higher rates compared with smooth bore extruders (SBE). Because of reduced energy-losses new GFE-designs are no longer water cooled but use ceramic heating-/air-cooling-devices. Performance data of GFEs and SBEs represent differences in output and quality esp. at high speeds. Pros and Cons are discussed with respect to extruder downsizing, flexibility, regrind processing and vented extrusion, leading to preferred applications for GFEs and SBEs.
Seal through Contamination Performance of Metallocene Plastomers
Philippe Mesnil, Jan Arnauts, Richard W. Halle, Norbert Rohse, May 2002
Metallocene plastomers are well known for providing superior toughness and excellent heat sealing performance in many high performance flexible packaging films. In a great many form-fill-seal applications it is also a requirement that the film continue to seal well even when the film surface is contaminated with product.This paper presents examples of the excellent sealing performance of plastomers, in particular of their performance when sealing through contaminants. Both laboratory heat sealing experiments and actual VFFS packaging tests are described.
Secondary Aminosilanes for Mineral-Filled Polyamides
Helmut Mack, May 2002
Inorganic fillers such as calcined clay and wollastonite have been used to modify the properties of nylons for several years and glass fiber reinforced products are extensively used. The use of glass fibers, while offering many benefits, does lead to problems of anisotropy caused by fiber orientation. This can result in warpage and shrinkage, particulary in larger, thin sectioned mouldings. Calcined clay and wollastonite were introduced to minimize warpage, but still maintain rigidity.Silane coupling agents provide the ability to bond inorganic fillers to organic resins by establishing molecular bridges". Current technology utilises primarily ?-aminopropyltriethoxysilane as a coupling agent for improving interphase interactions in mineral-filled nylon systems. Although many mechanical properties are greatly improved by the use of ?-aminopropyl-triethoxysilane impact properties generally are not.This presentation covers mineral fillers and silanes and how to combine both in a successful way. N-nbutyl-?-aminopropyltrimethoxysilane is presented as a further aminosilane development that imparts not only excellent processability and rigidity to a composite but also increased impact strength due to its coupling and dispersion abilities."
Selective Reinforcement and Structure Development Control in Injection Molding of Bone-Analogue Composites
Rui A. Sousa, Rui L. Reis, António M. Cunha, Michael J. Bevis, May 2002
Composites of high density polyethylene (HDPE) with hydroxyapatite (HA - the main inorganic constituent of the human bone) were produced by extrusion compounding and subsequently injection molded. Shear controlled orientation in injection molding (SCORIM) was used deliberately to induce a strong anisotropic character in the composite materials. Bi-composite moldings featuring a sandwich like morphology were also produced by mono-sandwich injection molding. These composites combine a HDPE/HA outer layer and HDPE/C fiber reinforced core. For all the cases, the mechanical performance of the produced composites was assessed and the structure developed investigated and related to the processing conditions.
Sensory Aspects of Plastic Materials
Jean-Emmanuel Noreux, Sylvain Jeannin, May 2002
Over the last twenty years plastic materials have played an ever increasing role in the field of industrial design. Indeed, plastic materials allow an infinity of shape, colours and aspects. But, today, they are taking another turn and their intrinsic qualities are being used to provide sensory aspects to plastics products. We looked, therefore, into what sensory plastic material aspects meant and what they could offer as far as the conception of new products is concerned. We were interested in the purchasing behaviour of customers throughout the analysis and with an industrial example we would like to show you the techniques which are used and applied in industry.
Separation of Polyphenylene Ether from its Additives
Sarah M. Reynolds, David F. Ober, May 2002
Polyphenylene ether (PPE) is a high cost material, starting at three times the cost of polypropylene, with the price only increasing as fillers are added. Plastic parts made of PPE with the additives carbon, talc, and mica could be reused as pure PPE if the additives were removed. A process was developed to separate the PPE from the additives, using a solvent that dissolves the PPE and leaves the additives as tiny particles. The mixture was filtered, allowing the dissolved PPE to pass through but retaining the additives. The reclaimed PPE can be sold for a profit and used to make new parts. Recycling the PPE saves millions of pounds of material from being dumped into landfills each year.
Shear-Mediated Crystallization of Isotactic Polypropylene: The Role of Long Chain-Long Chain Overlap
Derek W. Thurman, Julia A. Kornfield, Motohiro Seki, James P. Oberhauser, May 2002
Studies of structure and morphological development during shear-induced crystallization of a model isotactic polypropylene (iPP) blend were performed using in-situ rheo-optical and ex-situ microscopic techniques. In order to elucidate the effects of long chain-long chain overlap, a series of binary blends were prepared in which a high molecular weight fraction of iPP (L-PP, 923 kg/mol) with narrow molecular weight distribution was blended with lower molecular weight metallocene iPP (Base-PP, 186 kg/mol). The effect of L-PP concentration (c) was examined from c/c* = 0 to 2, where c* is the overlap concentration of L-PP (c* ? 0.7 %wt). Birefringence measurements during and after shear showed that addition of L-PP greatly enhanced shear-induced development of oriented structures. Polarized light microscopy and TEM techniques provided further probes of morphology following complete crystallization of samples. Results indicate that oriented structures develop with a non-linear dependence on c showing the role of long chains is cooperative, enhanced by long chain-long chain overlap.
Shiny Solid Surface Structural Foam Injection-Molded Parts with Rapid Mold Temperature Control by MmSH Process (Momentary Mold Surface Heating and Cooling Process)
Dong-Hak Kim, Myung-Ho Kang, Young Ho Chun, May 2002
MmSH(Momentary Mold Surface Heating) process is an invention that heats only the mold surface over 400 °C in a few seconds with gas flame and cool it down very quickly again[1,2].Practically it was tried to produce a shiny surface of 98% light reflecting of notebook PC housing of 20% expanded structural foam with PC/ABS alloy. In addition to the outstanding surface quality, physical properties such as falling dart impact strength and heat resistance were improved. And it was carried out successfully with simple attached equipment and specially designed MmSH Mold which is to supply the gas fuel and air between the two parts of mold.The results of injection-molded notebook PC housing with MmSH Process will be discussed in this paper.
Simulation Study of Polymer Flow through an Extrusion Blow Molding Head
Matthew J. Day, James T. Haring, May 2002
The unequal flow of polymer, through a die, is a common problem in industry. This imbalance in flow is due to a non-uniform flow path resulting in different velocities at different points in the die. This problem is commonly fixed by adjusting the die or pin position to compensate for the uneven flow. In complex die shapes, compensating for uneven flow cannot be done as easily. Simulation software was used in a verification study to ensure that the results from the software matched the experimental results. This will be useful in industry's determining of the validity of such software.
Simultaneous Butt/Lap Joints for PVDF Pipes
Alex Savitski, May 2002
EWI has developed a concept of simultaneous butt and lap double-secure beadless joints for tubular plastic components and tested it experimentally on high-purity (HP) polyvinylidene fluoride (PVDF) and high-density polyethylene (HDPE) pipes. The technique is based on through-transmission infrared (TTIR) welding method and uses an IR energy source placed outside of the joint area, so pre-assembled parts can be welded. The original joint design incorporates two welds: the lap and butt welds. The lap weld, which utilizes a straight coupling, provides structural strength to the joint. The butt weld between the pipe ends, while contributing to the overall strength, seals the gap without any bead, and forms a smooth transition from one pipe to another.Butt/lap joints offer considerable advantages, such as strength and security, absence of the internal bead, and inspectability, and while this project demonstrated that it is possible to produce such joints, further work is needed before the process will be fully developed and refined for specific applications.
Single Capillary Rheometer Technique for Determining Molecular Weight Distribution of Conventional and Metallocene Catalysed Polyethylenes
B.G. Millar, G.M. Mc Nally, W.R. Murphy, May 2002
A new approach to determining the molecular weight distribution of metallocene (mPE) and conventional polyethylenes using a single capillary rheometer technique is reported here. The melt flow properties of a range of 17 mLLDPEs and 4 conventional LLDPEs with different MFIs, densities and co-monomer types (butene, hexene, octene), from six different suppliers were investigated using this technique. The results show a direct correlation between melt flow rate ratio and molecular weight distribution (MWD,) measured by Gel Permeation Chromatography: MWD = (2.34 x MFRR) - 5.14. A direct correlation between weight average molecular weight (Mw) and melt flow index for the resins was also determined: Mw = 1.09 x 105 MFI-0.26.
Single-Step Rotational Foam Molding of Skin-Surrounded Polyethylene Foams
Remon Pop-Iliev, Chul B. Park, May 2002
This paper demonstrates how the rotational foam molding process can be employed for the manufacture of plastic articles that have a distinct layer of non-foamed skin surrounding a foamed core or layer. It is focused on the single-step processing principle the main feature of which is the simultaneous introduction of both the foamable and non-foamable resin into the cavity of the mold at the beginning of the cycle. Although this advanced concept eliminates the need for process interruptions and the use of drop boxes or plastic bags, it requires an appropriate processing strategy that would assure that the execution of the adhesion of the non-foamable thermoplastic resin to the internal surface of the mold always takes place prior to the activation of the foamable resin.
The Sintering Behavior of Ethylene/?-Olefin Copolymers Powder and Cylinders
S.A. Guillén-Castellanos, C.T. Bellehumeur, M. Weber, May 2002
Rotational molding is used to produce hollow plastic parts. The polymer, usually in powder form, is loaded into a mold. The mold is then heated and rotated biaxially. During the heating process, the tumbling powder gradually melts and sticks on the mold surface. Heating is continued after the powder has melted until complete densification is achieved. The mold is then cooled and the molded part is removed. As the powder particles adhere to the mold surface, pockets of air are trapped within the melt and form bubbles. The presence of bubbles is an inherent drawback in a finished molded part. It impairs the aesthetic value and the mechanical strength of the product. The polymer sintering phenomenon plays a major role in both the molding cycle and the properties of the final parts.This work is part of a research program whose objective is to examine the sintering behavior of ethylene copolymers under conditions related to the rotational molding process and to determine the relative effects of the polymer molecular structure on the sintering process. It is also expected that in addition to the polymer molecular structure, the preatreatment imposed on the resins during the pulverization process also influences sintering behavior. The magnitude of these effects is, however, difficult to quantify. Experiments using both powder particles and cylindrical particles are conducted in this work to obtain a general overview of the effect of pulverization on the sintering process.
Size Does Matter: Minimization of Gate Wear
Kurt Hayden, Paul Engelmann, Philip Guichelaar, Mike Monfore, Jay Shoemaker, May 2002
Previous work in flow simulation and runner system balancing has demonstrated the impact that small changes in gate size have on cavity filling. Gate wear affects shear rate and in turn, the viscosity of the melt. The flow of glass filled material has long been identified as a factor in tool wear. As part of the long-term wear studies of copper alloys and tool steels at Western Michigan University, careful scrutiny was given to wear of edge gates due to the flow of molten plastic. Certain hard coatings and alloys were shown to demonstrate superior resistance to wear.
Skin-Core Effects in Polypropylene Nanocomposites
Alejandro Hernandez-Luna, Nandika Anne D’Souza, Ajit Ranade, Marta Drewniak, May 2002
Interest in polypropylene (PP) nanocomposites has increased considerably recently, especially in the automotive industry where PP comprises the main constituent in rubber modified PP blends for exterior and interior applications. The potential for increasing the mechanical properties with small reinforcement concentrations has driven much of this interest. However, it has been known that PP exhibits prominent skin-core effects. Here it is investigated this effect for nanocomposites using transmission electron microscopy, X-ray diffraction and thermal analysis. Further tensile and fracture toughness measurements are done as a function of concentration. Real time Infrared thermal wave imaging coupled to the mechanical testing is used to examine plasticity changes.
Solid Finite Elements for the Prediction of Complex Sheet Distortions
P. Debergue, D. Laroche, May 2002
Significant developments in finite element modelling of the thermoforming process have been observed in the recent years. The large deformations of the sheet that occur during sagging and forming have traditionally been modelled using membrane or shell type elements. This paper proposes a 3D solid finite element approach for improving the part wall thickness predictions. A 27-node brick element with incompressibility constraint is presented for modelling large viscoelastic deformations of the sheet. An experimental validation on a vacuum formed part with three different sheet thicknesses is presented. A comparison with the membrane formulation is also provided.
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