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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The Role of Fundamentals, Visual Observation and State-Of-The-Art Instrumental Methods in Solving Plastics Failures
While experience is a valuable asset, a novice failure analyst can solve even complicated plastics failures using a logical approach and utilizing the most appropriate analytical and test methods. By including old as well as state-of-the-art new methods, the test results often point right to the cause of failure. The eye, by itself, and with moderate magnification early in the investigation can provide information which helps point the way to solving the problem. Observations and test results are assessed as to which of the three major factors in plastics performance are involved - design, material, processing or combinations thereof.
The Role of Simulation and Computer Aided Analysis in Injection Molded Products
Simulation and computer aided analysis of the injection moulded process is known to many, but rarely employed. Computer Aided Engineering (CAE) affords the opportunity to reduce costs.This is a case study of the rectification of the inconsistent surface finish concern involving rear mudguards used in automotive applications. The cause of the problem was difficult to diagnose accurately, and attempts to remove the problem by speculation guided by experience failed. CAE software was used as an instrument, to diagnose the cause of the problem via process simulation and analyses of the results. The information obtained was then applied to provide recommendations, which not only solved the problem but also improved the molding process. By showing the benefits CAE added to the final product design and process, it was concluded that process simulation and computer aided analysis is too important a tool for saving time, material, human resources, and consequently money, to remain under utilized.
Rotational Molding of Polyolefin Plastomers and TPOs
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
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.
Scratch and Abrasion Resistant UV-Topcoats for Plastics Using Colloidal Silica Acrylates - Impact of Size, Size Distribution and Silica Loading on Coating Properties
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
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.
Secondary Aminosilanes for Mineral-Filled Polyamides
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
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
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
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
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)
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.
Simultaneous Butt/Lap Joints for PVDF Pipes
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
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
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
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.
Skin-Core Effects in Polypropylene Nanocomposites
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
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.
Solid State Polymerization of Recycled Poly(Ethylene Terephthalate) - The Influence of Process Conditions in the Increase of Molecular Weight and Thermal Properties
The solid state polymerization (SSP) of recycled PET from 2L bottles was investigated. The bottles were ground, washed, dried, crystallized and processed in a reactor under heating and nitrogen flow. The material was feed in the reactor as flakes and not in pellet form, so an extrusion step was eliminated. A systematic study of the influence of process conditions, like crystallization temperature, SSP temperature, reaction time and nitrogen flow rate was carried out. The weight-average molecular weight of the recycled PET were measured by SEC. Thermal properties and crystallinity were determined by DSC.
Spatially Controlled Growth of Polyelectrolyte Multilayer Islands
We are pursuing a new method for the rapid processing of polymeric multilayers with spatial resolution based on a combination of Electrostatic Self Assembly (ESA) and contact deposition using swollen hydrogel applicators. Thus far, we have demonstrated the build-up of multilayered polymeric structures (10-200 nm thick) by using separate applicators swollen with either a polyanion or polycation solution and pressing them upon a pristine substrate. The swelling response of the photopolymerized hydrogel is an important phenomenon. We find that the steady state swelling in water depends on the crosslink density while observations of the swelling behavior in polyelectrolyte solutions revealed a dependence on both ionization and concentration. We found that as more PAH (polyallylamine hydrochloride) is added to the solution, the degree of swelling decreases slightly and as the crosslink density is decreased, the percent swelling increases. PMAAc (polymethacrylic acid) has a contrasting effect on the swelling of the hydrogel; at full ionization, a slight amount of PMAAc surprisingly promotes swelling. Using Atomic Force Microscopy, we compared surface structures of ESA done by dipping with those created by stamping. The AFM from contact ESA showed favorable homogeneity, but some large features that are hypothesized to come from aggregates that form in the stamps.
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