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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Rheological, Morphological and Interfacial Properties of PP/HDPE Blends
In this paper the linear viscoelastic properties of polypropylene (PP)/high-density polyethylene (HDPE) immiscible blends were measured as a function of frequency for different blend composition and temperatures. The morphology of the blends was studied by Scanning Electron Microscopy. The interfacial tension between the components of the blends was evaluated using small amplitude oscillatory shear analysis. The results seem to indicate that there is a range of compositions for which it is possible to use Gramespacher and Meissner analysis in order to calculate interfacial tension between polymers using small amplitude oscillatory shear measurements.
Predictive Model Helps Develop New High-Performance HDPE for Barrier Film Application
As the blown film industry has matured, the need for decreased cost has become paramount. The most attractive means of reducing cost is by down gauging film thickness, which inherently reduces the toughness of the film. This paper describes how a predictive model was used to develop a new homopolymer HDPE resin, which produces films with significantly improved mechanical properties without sacrificing barrier properties. The improved properties are the result of modifying the molecular weight and molecular weight distribution of the resin. Detailed blown film results demonstrate the performance improvement and the downgauging potential of the new resin compared to conventional HDPE.
Effect of Interdiffusion Regions on Barrier Properties of Multilayer Films
Barrier properties of polymer films can be improved in various ways, such as formation of multilayer structures by coextrusion, surface treatment, and coatings. This work explores the use of thousands of alternating layers of polymer (xyxy...) to alter the resistance to permeation. A model is presented to predict the number of layers needed in a laminate to change the flux of a permeant by a given amount. An important feature of the model is the species transport across the interdiffusion regions at the polymer-polymer interfaces where diffusivity of the penetrant is assumed to be a function of the volume fractions of the interdiffusing polymers. Our modeling results show that increasing the number of interfacial regions decreases the flux for a given condition, and a large number of layers are required to achieve appreciable barrier enhancement.
Temperature Monitoring of Capillary Rheometry Using a Fluorescence Technique
A non-contact temperature monitoring technique based on fluorescence spectroscopy was used to measure the temperature of a polymer resin during capillary rheometry testing. Polyethylene doped with a fluorescent dye, perylene, was used in experiments that were designed to measure resin temperature changes due to shear heating as shear rate in the capillary increased from 10 to 10000 s-1. Resin temperature at the exit orifice of a 1 mm diameter capillary die was found to increase monotonically with increasing strain rate reaching 25°C above the capillary set point temperature at the highest shear rates. The implications regarding rheometry testing are discussed.
New Solidification Models for the Simulation of the Injection Molding Process
In order to predict shrinkage and warpage in injection molded products, the thermal contraction and the residual stress have to be calculated. Therefore the temperature distribution in the injection mold has to be simulated during the fast cooling in the cavity. For semi-crystalline polymers this implies the incorporation of the latent heat of crystallization into the heat equation by means of an adequate crystallization model. Furthermore, properties such as the specific volume and the heat capacity and conductivity need to be modeled. The models for the crystallization and the thermal properties presented here are physically motivated. Simulations are presented of the temperature distribution during the fast cooling of semi-crystalline polymers with and without glass fibers. The calculations are compared to experimental results, which have been obtained with an apparatus designed especially for very high cooling rates.
A Preliminary Investigation into the Use of Wood Fibers as a Filler in the Rotational Molding of Polyethylene
There has been no known work carried out on the use of wood fibers as a filler in the Rotational Molding (herein also referred to as rotomolding) of Polyethylene. It is reported though that the extrusion industry has noticed a 100% increase in wood fiber profiles over the past two years. (1) It is only a matter of time before this diversity of materials will find itself being used in Rotational Molding. This paper presents investigative results of the characteristics of the molded parts in terms of molding conditions, percentages of wood fiber used and the type and size of wood used. Potential for novel product design and the uses for the wood/ plastic composite will also be discussed.
Natural Fiber Reinforced Polypropylene Composites – an Approach on Thermoforming Processing
This work has been performed at Mercedes-Benz of Brazil in a partnership with its suppliers aiming the replacement of fiberglass in polypropylene matrix composites by natural fiber reinforcements. The process that has been chosen for this purpose was Vacuum-forming. This choice took into account the large application that this technique represents in the company's commercial products. The results expected for this new material is cost and weight reduction besides the friendly environmental aspect that this change introduces. Jute fiber reinforced polypropylene sheets at constant thickness and fiber content were prepared in order to evaluate the feasibility of the application. The preliminary results have shown that this material has a great potential of application because of the low fiber costs.
Experimental and Analytical Verification of Plastics Material Models for Automotive Crashworthiness Applications
Plastics are widely used in automotive component applications, such as instrument panels, door panels, consoles and pillar garnishes. These components are subject to government-mandated impact tests for occupant safety. To overcome the traditional cut-and-try methods in designing automotive components, advanced CAE (Computer Aided Engineering)/FEA (Finite Element Analysis) analytical methodologies have been used to assist the design and manufacturing of the desired components. The objective of this paper is to investigate the effects of material model and impact speed of the drop weight on the response of an injection-molded plastic knee bolster part under a designed drop-silo impact test. FEA simulations on the knee bolster were conducted using both LS-DYNA3D and ABAQUS/Explicit. The analytical results are compared to the experimental data from the drop-silo impact test. Several engineering plastic materials are evaluated, and correlation is quantified. Observations are made with respect to materials characterization experiments, material constitutive models within the analyses, and general test and modeling procedures. Suggestions are made for improved correlation for the future.
The Effect of PP-MA and PP-GMA as Compatibilizers on Polypropylene/Nylon 6 Blends
Blends of polypropylene (PP) and nylon can combine good properties, however both polymer are incompatible. PP functionalized with maleic anhydride (PP-MA) has been used as compatibilizer for this system and the PP functionalized with glycidyl methacrylate (PP-GMA) should be a good alternative due to reactivity of the epoxy group with -NH2 and -COOH group. Blends of PP/PP- MA or PP-GMA/Nylon 6 were prepared using 30% of nylon (Ny6). The effect of the compatibilizer were evaluated by DSC, SEM micrograph and mechanical properties. The analysis indicate that PP modified with MA show the best compatibilizing effect in these systems.
Compatibilized Polypropylene/Polyamide Blends
When properly compatibilized PP/PA blends can offer a wide range of desirable characteristics, combining properties of both components. The aim of this work is to compare the effectiveness of the compatibilizing effects of different modified polyolefins on the properties of PP/PA blends. The blends were constituted by a PP matrix and they were obtained in a mixer chamber. PP modified with maleic anhydride and vinyltriethoxysilane (PP-MA and PP-VTES) and EPR modified with maleic anhydride (EPR-MA) were employed as compatibilizing agents. Products were characterized by SEM and DSC. Melt flow indexes and mechanical properties of the blends were determined.
Use of Pyrolised Oil Shale as Filler in Polyolefins
The pyrolysed oil shale originating from the pyrolysis of the bituminous rock was used as filler in mixture with poly(ethylene-co-vinyl acetate) (EVA) and high density polyethylene (HDPE). The effects of this addition were compared with the ones obtained with different vinyl acetate content and size of pyrolysed oil shale particle. The compounds were prepared on a Haake equipped with mixing head Rheomix, at 180°C. Samples were compression-molded and tensile testing ware performed on an Instron apparatus using a crosshead speed of 10 mm/min. Tension curves of samples were obtained. These curves showed the possibility utilization the pyrolysed oil shale without damaging the mechanical properties of the compounds, for low concentration of pyrolysed oil shale (1-5 wt%) if the particle of pyrolised oil shale is lower than 270 mesh. Besides of this behavior it was observed that the vinyl content of polymer is important to enhance the mechanical properties in the compound. Compounds of poly(ethylene-co-vynil acetate)/pyrolysed oil shale and high density polyethylene were obtained with concentration of pyrolysed oil shale up to 30%. The behavior of these materials were evaluated taking into account the concentration and the size of the used particle. It was observed that particles with the smaller diameters showed best effects on the mechanical properties of the final material if the concentration of the pyrolised oil shale used up 5% wt%. The mechanical properties, differential scanning calorimetry, and scanning electron microscopy results and dynamic mechanical thermal analysis are discussed.
Degradation Mechanisms of Thermoplastic Polyurethane Resins
The use of polymeric materials for transparent, lightweight armor has been of great interest to the U.S. Army for a number of years. Field items such as goggles, lens, face and windshields are currently manufactured using advanced polymeric plastics. These items are designed with polymers that provide excellent optical clarity, rugged abrasion resistance, and high ballistic impact strength. However, as with any organic polymer system, these materials are susceptible to degradation over time when exposed to various environmental (i.e. sunlight, moisture, temperature) conditions. This structural degradation (1-4) will eventually comprise the original integrity of the materials' desired properties. In this study, the impact of accelerated weathering upon newly developed polyurethane based thermoplastic materials was investigated. A fluorescent ultraviolet (UV)/condensation weathering tester was selected for the exposure study. The materials were characterized by UV/VIS spectroscopy and FT-IR spectroscopy. The results reveal that the urethane linkages undergo a scission reaction upon UV exposure drastically affecting the mechanical properties of the material. Furthermore, these urethane scissions produce a yellowing of the polyurethane which can inhibit its use where optical clarity in important.
Diffusion Studies in Polymerized Poly (Methyl Methacrylate) Nanocomposites by FT-IR
Polymer-layered silicate nanocomposites have attracted enormous interest both in scientific research and potential commercial applications mainly due to the potential technological applications. The silicates used in these nanocomposites consist of stacked individual platelets with a dimension typically on the order of 1 - 100 nm in length and 1 nm in thickness. These nanoscale structures provide the resultant material with an improvement in properties, which include abrasion resistance, and mechanical properties. In this paper, we report the improvement in barrier properties when a PMMA/Clay nanocomposite is synthesized. This increase in barrier properties is attributed to a successful dispersion of the clays in the polymer matrix. Reports have shown that properties depend upon the extent of intercalation, and in many cases exfoliation are desired to achieve the properties. Comparison of the effect of two different types of clays, montmorillonite and a synthetic clay, fluorohectorite, on the transport properties was studied. In each case an improvement in barrier properties was observed.
Multi-Component Blends Based on Polyamide 6 and Styrenic Polymers
Reactive and non-reactive blends of polyamide 6 (PA6) with different styrenic based polymers [acrylonitrile-butadiene-styrene terpolymer (ABS) and styrene-acrylonitrile copolymer (SAN)] were made on a twin screw extruder under similar processing conditions and blend composition. Effect of reactive compatibilizer on thermal, morphological and rheological properties were studied using DSC, SEM and a parallel plate oscillation rheometer. It was found that the reactive blends have lower crystallization rate and nucleation ability but higher melt viscosity with co-continuous morphology, whereas the uncompatibilized blends have higher crystallization rate and nucleation ability but lower melt viscosity and form disperse and/or coarse co-continuous morphology.
Integrated CAE Analysis for Powder Injection Molding: Filling, Packing and Cooling Stages
Powder Injection Molding (PIM) is a manufacturing technology for the mass production of small and complex metal or ceramic parts. PIM is composed of mixing, injection molding, debinding and sintering processes. We have developed a numerical simulation program for the injection molding process of PIM parts, PIMflow, taking account of the peculiar rheological behavior of powder/binder mixture, most notably the apparent slip phenomena at the mold wall. The coupled analysis between the filling, packing and cooling stages was performed because the viscosity and slip phenomena of powder/binder mixture highly depend on temperature. Using the example of electronic package, this paper demonstrates the importance of this issue.
A Portable on-Line Rheometer
The Helical Barrel Rheometer (HBR™) is a device capable of utilizing viscosity monitoring of a melt slipstream from the process (reactor or extruder), or independently, determining the viscometric behavior utilizing solid feed. It does not require flow or torque measurement and solely relies on pressure drop and shaft speed to generate the viscosity data as a function of shear rates. The design principles of the current HBR™ unit have been focused on its portability, flexibility and versatility, yet it remains industrially rugged. It has been demonstrated that the HBR™ is a unique device in measuring viscosity of filled polymeric systems in a flow field more representative of process equipment as opposed to capillary devices. Other uses beyond viscometric measurement are also described.
Substitution of Metallic Insert Joints by Two-Shot-Molding
Threaded inserts in brass or in plastic show static and dynamic load-limits comparable to economic joints with self-tapping screws. A newly developed approach that is based on molding in a local area of reinforced plastic into a non-reinforced plastic component using multi-component-injection-molding was investigated. In this reinforced area a self-tapping screw is assembled. This joining technology could substitute the implementation of an insert after molding. In this paper, the joint performance in dependence of the interfacial strength will be shown in comparison to inserts made from brass and plastic as well as to self-tapping screws. In particular, the static load-limits and the clamp force, which is time dependent, will be discussed.
Mechanical Behavior and Crack Propagation in Injection-Molded Polyamide 6/Clay Nanocomposites
The crystalline structure and mechanical behavior of injection-molded polyamide 6 (PA6) reinforced with 2 wt.% polymer-intercalated nano-layered silicate (montmorillonite) is studied. X-ray diffraction and differential scanning calorimetry show that the presence of layered silicate in PA6 nanocomposites lead to the formation of a different crystalline structure when compared with unmodified PA6. Considerably improved tensile strength and modulus obtained from the nano-layered silicates while maintaining the ductility of the PA6 matrix indicate that strong matrix-filler ionic interactions and very high specific area and aspect ratio of the polymer intercalated-layered silicates characterized this nanocomposite. In the conditioned state, while an elasto-plastic fracture with extensive tearing is observed in unmodified PA6, a linear-elastic fracture is observed in the PA6 nanocomposite.
Optical Constants Determination of Absorbing Polymer Film with the Prism Wave-Guide Coupler
The prism wave-guide coupler has been limited to measuring the refractive index of transparent or weakly absorbing thin films. However, this study shows that it is possible to extract the complex refractive index (both the refractive index and the extinction coefficient) of highly absorbing films from a careful analysis of the internally reflected light intensity from the prism-wave-guide coupler. This method has been used to obtain the three-dimensional complex refractive indices of two polymer films, spin coated polyaniline (PANI) and 3M black vinyl electrical tape, using a modified Metricon PC 2010 prism wave-guide coupler.
Investigations into Rotational Moulding of Short Fibre Reinforced Thermoset Resins
The addition of reinforcing fibres, or fillers, to liquid thermosets significantly alters the rheological behaviour of such resins, drastically increasing viscosity. In order to successfully mould these materials a good understanding of their rheological behaviour is required. A simple numerical model is developed, predicting evolution of the resin cure reaction, and resulting in-mould rheological, and flow behaviour. Qualitative comparisons are made to initial moulding experiments completed with neat, and wood fibre filled polyester resins. Moderate additions of fibre were found to improve part quality due to the increase in initial viscosity, while a practical limit was reached above which excessive fibre clustering occurred.
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