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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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.
Inventions in Polymers: It Takes Teamwork to Make a Successful Business
The last five decades have seen the explosive growth of synthetic polymers. Innumerable types of polymers and their derivatives designed for specific properties and applications have been invented and developed. Fundamental to such growth are the creative discoveries of several scientists and innovators. Converting these brilliant discoveries into major business successes have taken the concerted efforts of a large number of a second set of inventors and innovators. While the primary inventors have been well recognized, often, the latter scientists and innovators, without whose contributions these products and processes would not have become large successful businesses, are relatively unknown. As examples, Teflon*, super-tough nylon, and sretch-blow-molding of PET bottles and the teamwork that made these into significant businesses, will be discussed here.
Experimental Investigation of Slip in Plug-Assisted Thermoforming
Surface friction is known to play a vital role in determining product wall thickness distribution during plug-assisted thermoforming. In this study this behavior has been investigated by carrying out experimental tests to measure both the static and dynamic coefficients of friction acting between typical plug materials (Delrin, syntactic foam and aluminum) and polypropylene (PP) sheet at elevated temperatures. Plug only tests were also conducted to investigate the effect of plug temperature on wall thickness distribution. Results showed that values of coefficient of friction varied from 0.13 up to 0.72 depending on sheet temperature and the combination of materials tested. Plug temperature was also shown to be very important, with a temperature of 90°C showing the greatest slip during plugging. It was concluded that friction at the plug-sheet interface was temperature dependant and further work is required to verify these initial observations.
Inventions, Patents and Innovations: A Beneficial Symbiosis - How I Learned to Stop Worrying and Love Patents"
Alter exploring the role of patents in encouraging disclosure of inventions as a significant stimulus to technological developments and innovations, this presentation will also probe how patents can protect commercial investments and provide a competitive advantage in global economy. Also presented will be certain practical considerations and tips on how to prepare and obtain patents others would envy." To this end the presentation will highlight major differences between the U.S. patent system and others will review important recent changes in legal requirements (with particular emphases on rule changes resulting from the enactment of the American Inventors Protection Act) and will examine common pitfalls to avoid. Where appropriate the patents relating to the innovations advanced by other speakers in Fundamentals Forum on Invention and Innovation will be featured as illustrations."
A Model and Parameter Formulation of Stress-Induced Crystallization Kinetics of Polymers
A stress-induced crystallization model for semicrystalline plastics is proposed based on the theory that stress induced orientation of molecules and chains increase the melting point of the plastics, and hence, the supercooling which is the driving force for crystallization. By assuming that the effect of stress on crystallization is only by increasing the equilibrium melting point, the basic quiescent state crystallization equation can be directly applied to model stress-induced crystallization kinetics. The model predicts the most prominent features of stress-induced crystallization. The main advantage of the model is that the parameters in the quiescent state crystallization model do not change. Consequently, the parameters in the equilibrium melting temperature shift model are easy to determine, and the unknown constants are kept to a minimum.
Optimization in Process Control for Uniform Quality of the Optical Components
Part weight, dimensions, shrinkage and birefringence are a few important measurable parameters that are used to define the quality of plastic optical components. The quality of a plastic part can be assured by determining the proper and optimized set of injection molding process variables. Online cavity pressure data as a function of time for a dual cavity optical mold were analyzed with an equation of state for an Ising fluid for establishing the PVT relationship. The PVT data were then used in an empirical model to determine the optimized set of process variables for the expected quality of a part.
Theoretical Validation of Long Chain Branching Quantification Technique for Polyethylene
An empirical technique for determining long chain branching level in well-defined polyethylene (PE) was recently proposed by Wood-Adams and Dealy. This technique consists of comparing the molecular weight distribution measured by GPC with an apparent molecular weight distribution derived from the complex viscosity. The method was proved to be robust for PE synthesized using constrained geometry catalysts. Nonetheless the theoretical basis underlying this technique remains not fully understood. This paper clarifies and widens the validity of the method by making use of the molecular dynamics theory based model of Milner et al. for blends of linear chains and three-arm stars.
The Effects of Varying Peroxides Concentration in Moisture-Crosslinking of LLDPE
The effects of linear low density polyethylene (LLDPE) grafting with vinyltrimethoxysilane by different types and contents of peroxide were studied. When grafting silane onto LLDPE, 0.10 phr content of Dicumyl peroxide (DCP) or 0.05 phr content of 2,5-Dimethyl-2,5-di (tert-butyl- peroxy)-hexane (DHBP) was found to improve the grafting effect; however, as Di (2-tert-butylperoxypropyl -( 2))-benzene (F40) or excess DHBP was used, LLDPE was supposed to cause self-crosslinking which deducted the grafting percentage of silane and invalided the processing of extrusion.
Linear Viscoelasticity of Binary and Ternary Immiscible Blends
The linear viscoelastic behavior of binary and ternary immiscible Polypropylene (PP) based blends with linear low density polyethylene (LLDPE) and different ethylene-propylene copolymers (EPR) is studied in this work. The effect of changing the composition and concentration of the dispersed phase under the small amplitude oscillatory shear flow is analyzed. It was found that the influence of the type of elastomer used is more important in the low frequency range. The predictions of a simplified constitutive equation for emulsions of viscoelastic fluids are only in good qualitative agreement with experimental results when an elastomer of lower Mw is used and in the high frequency range.
Compatibilized PP/PHAE Blends by Reactive Blending
Blending of immiscible polymers is a powerful method to create materials with enhanced properties at competitive costs. Reactive compatibilization additionally gives a more stable morphology and improved adhesion between phases. Blends of polypropylene (PP) and materials of very low oxygen permeability are very promising in this area. In this work we study polypropylene and polyhydroxyaminoethers (PHAE) blends of different compositions prepared in a batch mixer. The reaction of maleic anhydride graft polypropylene (MA-g-PP) with PHAE is analyzed. The reaction products were analyzed by FTIR, DSC and SEM. MA-g-PP is found to be an effective compatibilizer of PP and PAHE.
Reactive PP/Elastomer Blends Using Coupling Agents
Reactive blending is an attractive way to produce block or graft copolymers in situ to compatibilize immiscible polymer. Location of the copolymer at the interface decreases the interfacial tension and at the same time a steric stabilization occurs that reduces particle coalescence. In this work we explore the efficiency of 1,4- Phenylenediamine (PDA) as a coupling agent for polypropylene (PP) and ethylene-propylene diene (EPDM) funcionalized with maleic anhydride to produce PP-co-EPDM. Different concentrations of the coupling agent were used at fixed mixing conditions and reaction products were characterized by FTIR, DSC and SEM.
The Effect of Layer Stretching on the Onset of ‘Wave’ Interfacial Instabilities in Coextrusion Flows
The effect of layer stretching on the onset of 'wave' interfacial instabilities in coextrusion flows is evaluated through transient viscoelastic stress calculation by modified Leonov model and the velocity field determination through FEM with the help of newly proposed criterion based on the difference of normal stress differences across the layer interface. The study shows how this criterion can be used to investigate the role of the die design and elongational viscosities of coextruded materials from the interfacial instability point of view. It is shown that both the die geometry and the elongational strain hardening have a crucial effect on the interfacial wave instability.
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