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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Morphology and Mechanical Behavior of Poly(3-Hydroxybutyrate)/Functionalized Ethylene Copolymers Blends
The possibility of poly(3-hydroxybutyrate) (P(3HB)) mechanical properties improvement through reactive blending with ethylene-methacrylic acid copolymers either in the acid form (I-H) or partially neutralized with Zn (I-Zn) and Na (I-Na) was investigated. Blends of P(3HB) and I-H, I-Zn and I-Na were prepared in an internal mixer and in a double screw extruder. The blend with I-H showed the best results for mechanical properties. All the blends showed a significant reduction in the Young modulus, which was smaller for P(3HB)/I-Zn blends. Blends containing 30% of I-Zn presented the higher impact resistance and morphology containing the dispersed phase as cylindrical domains.
Strain Hardening Behavior in Elongational Viscosity for Blends of Linear Polymer and Crosslinked Polymer
Rheological properties for the binary blends of a linear polymer, such as isotactic polypropylene (PP) and polystyrene (PS), and gel fraction of a crosslinked terpolymer composed of ethylene, 1-hexene, and ethylidene norbornene (gEHDM) have been studied. Blending of the gEHDM, which is characterized as the gel just beyond the sol-gel transition point, much enhances the strain hardening behavior in the elongational viscosity of PP, even though the amount of the gEHDM is only 1 wt%. On the other hand, the PS/gEHDM (97/3) blend shows no strain hardening in the elongational viscosity. The entanglement couplings between the gEHDM and the PP will be responsible for the strain hardening behavior.
Influence of the Dispersed Phase Composition on the Mechanical Properties of Toughened PP Ternary Blends
Polymer blends offer nowadays a quick and economic way of improving properties at competitive costs. Such blends have already reached a massive application in the case of thermoplastics. This work presents results obtained for blends of polypropylene (PP), linear low-density polyethylene (LLDPE) and ethylene-propylene rubbers (EPR or EPDM). Different dispersed phase particle sizes are obtained varying the content of LLDPE and the viscosity of elastomers. The morphological features of such blends prepared in a twin screw extruder have been studied by TEM. Notched Charpy impact resistance of injection-molded samples was determined at different temperatures. Fracture surfaces were observed by SEM and elastic modulus were measured and correlated with dispersed phase composition.
Mechanical Mixing in Pin Screw Extruders: Experimental and Numerical Analysis
Pin extruders are frequently used in rubber processing. They are designed to exhibit good mixing capabilities and deliver an important mechanical work to facilitate the processing and mixing of elastomers. The design of such single screw extruders (SSE) is based on empirical know-how and trial-and-error. In this study, we compare three extruder configurations: a simple, continuously flighted single screw, a single screw with interrupted flight and finally a pin barrel screw. The calculation of the flow rate vs. pressure drop confirms that the interrupted flight reduces the pumping efficiency and the addition of the pins does not increase this effect any further. Statistical analysis of the trajectories obtained from the transient velocity field allows us to evaluate directly indices linked to the mixing quality. We obtain a good qualitative agreement between the calculated and measured RTD and confirm that there is an increasing mixing capability in the grooved screw and even more so in the pin barrel extruder.
Studies on the Rotomolding of Liquid Crystalline Polymers
This work investigates the rotational molding (RM) of liquid crystalline polymers (LCP) for making storage tank liners for storing cryogenic and corrosive fluids. We had previously reported work done on sintering of LCPs in order to determine the right candidate for rotomolding (1). This paper reports the studies conducted on the rotational molding of a standard polyethylene and the LCP chosen as a result of sintering studies. The various parameters examined include the rotational molding times, oven temperature, and rotor speed on final mechanical and morphological characteristics of the part formed. Low shear rate viscosity is a very important aspect determining the feasibility of rotomolding of LCPs. This has been examined in case of two LCPs, Vectra A and Vectra B230.
Modification of Clay Intercalate Structure and Properties of TPO Based Nanocomposites
Intercalated montmorillonite (MMT) is the most important organoclay for production of polymer/clay nanocomposites. Understanding the structure-properties relationship is crucial for the successful development of new materials based on organically modified clays. Structure analysis based on X-ray diffraction and computational molecular modeling reveals details of Na-MMT intercalated with octadecylamine. Properties of polypropylene and polyethylene nanocomposite films prepared from clays intercalated with octadecylamine by ion-dipole method and with alkylammonium organocations intercalated by more conventional ion-exchange method are discussed.
Performance and Structure of Highly Oriented Toughened Polypropylene
In this paper, two solid state forming processes, namely roll-drawing and die-drawing were evaluated for inducing high levels of orientation in toughened polypropylene (PP). PP was toughened using a metallocene polymer (mPE) at two levels, 10 and 25 wt%. Orientation, structure and properties of the resulting materials were evaluated. Draw ratios obtained ranged from 1 to 10 using the roll-drawing process and up to 15 using the die-drawing process. Moduli and strengths were affected in proportion to the elastomer content and the die-drawing process showed an improvement in the drawability of the toughened material. Morphological examination revealed the orientation of the dispersed phase domains.
Vibration-Assisted Injection Molding Applied to Recycled General Purpose Polystyrene
Because of their previous thermal and shear history, recycled plastic materials have properties that are significantly inferior to those of their unrecycled counterparts. Thus, the applications of these materials are limited. With the aid of Vibration-Assisted Injection Molding (VAIM) technology, during the present study the properties of products made from recycled polymeric materials were improved. In this paper, the property enhancements realized with recycled polystyrene are presented compared with those obtained through the convention injection molding of virgin material. Also, a potential theoretical basis for the phenomena is discussed.
A Vision for the Rational Design of Polymer Nanocomposites
This paper maps out a systematized approach to the design of nanoscale composite structures in heterogeneous polymer systems to meet application performance requirements, the processing technologies to generate those structures and the resulting material properties. Implementation of such a program would focus materials development on performance objectives while also serving to establish commercially viable process routes and define property benchmarks. It addresses the need to identify and understand nanophase interactions in order to realize desired enhancements in engineering properties. Understanding of these phenomena may best be achieved through a synergistic combination of modeling and experimentation. Examples will be provided to illustrate selected facets of the overall scheme with a focus on commercially significant applications.
The Influence of Processing Parameters on the Properties of Melt-Spun Polypropylene Hollow Fibers
Isotactic polypropylene hollow fibers were produced by melt spinning. Spinning speeds up to 1880 m/min were used, and sample hollowness (percent void in cross section) ranged from 0 to 69%. The fiber samples were characterized using dynamic mechanical analysis, birefringence, tensile testing, and differential scanning calorimetry. The hollow fibers were found to have higher crystallinity, orientation and strength than the analogous solid fibers. In general, the polymer orientation in a hollow fiber was larger than the orientation in a solid fiber, even when the spinning speed for the latter was much larger. For a fixed outer diameter, increasing the hollowness improved fiber properties. However, as hollowness was further increased, fiber properties declined slightly. At a given percent hollowness, increased spinning speed increased modulus and tenacity.
Quick Tooling: New Software Applications Bring Power and Compatibility to the Toolmaking Process
With customers demanding shorter and shorter lead times to get their products to market, profitable moldmaking demands accurate quoting. Design problems that are unforeseen during the quoting process disrupt production and impact your margin. Quick Tooling delivers critical tooling information to salesmen, engineering and shop-owners for timely and informed decisions. This new technology enables moldmakers to compress the mold delivery cycle, elevate critical design variables early in the process, and eliminates repetitive manual tasks. The faster you can establish which constraints will cost you the largest engineering concerns in the tool delivery cycle, the more accurately you can quote, the better the bottom line. Quick Tooling adds value to the tooling development process by providing an environment in which expert tool engineering process knowledge is captured and analyzed, enabling the user to account for upstream constraints earlier in the tool design process. Simulation software enables users to digitally view the actions of the tool before committing engineering hours to the job.
Mixing Behavior of a Model Miscible Binary Polymer System Having Extremely Low Viscosity Ratio
It is well known in industry that production of multi-component compounds with an extremely low viscosity ratio is a very difficult undertaking. This paper describes an attempt to investigate factors affecting mixing of a model system having a viscosity ratio well below 0.001 using a batch internal mixer. Similar to the findings of Ratnagiri, Scott, Joung, and Shih (1, 2, 3) on morphological development during mixing of immiscible polymers, we have observed similar S-shaped torque profiles during mixing of miscible polymer systems of styrene-isoprene-styrene block copolymers with hydrocarbon oils. The time to reach the upper higher torque branch, i.e., the Phase Inversion (PI) time as defined by Ratnagiri and Scott (2), increased with the amount of low viscosity component in the binary composition. The data could be well represented using an exponential model. We also found the PI Time to be longer at equal shear rates and slightly longer at equal RPM using a larger mixer. We were surprised to find the miscible system also exhibited a similar S-shaped torque profile. A method to reduce the PI Time in blends with a high concentration of the low viscosity ingredient was explored. It was also shown that PI Time could be reduced significantly using a split low viscosity feed addition and that a 25% / 75% split had a shorter time to PI than a 50% / 50% or 75% / 25% oil distribution. This emphasized that a slight lowering of the major component viscosity with small additions of oil was the most advantageous process for decreasing total time for PI.
Deformation and Yielding in Blown Oriented Polystyrene Films
Shear bands were generated in polystyrene upon melt extrusion and film blowing. These bands consisted of two sets with an intersection angle ranging from approximately 36 to 65 degrees. The definition, morphology and intersection angle of the bands varied with film processing conditions. The widely distributed bands are indicative of shear yielding rather than viscoelastic flow that could govern the later stages of film formation. Upon further deformation, new shear bands were generated with the band morphology varied with the draw ratios introduced in film blowing. The bands were fine and diffusive for films with high draw ratios. They were large and localized for that of low draw ratios.
Failure of Thermoplastic Tanks
Thermoplastic sheet polypropylene and PVDC is widely used in corrosion-resistant tanks for storage of fluids, including dangerous chemicals. We report the failure of one such PP tank used to store 40% caustic soda. A weld failed in a full tank 3 months after installation, causing damage to property but no personal injury. The detailed investigation revealed that the basic design was faulty, the tank being built like a barrel rather than like a dam. The excessive hoop stress from the hydrostatic pressure caused the failure of two welds. Other tanks made in the same way were inspected and corrective action taken. Such tanks should be built to the German standard DVS 2205.
Solvent Welding of Abs and Hips-A Case Study in Methylene Chloride Substitution
An investigation was conducted to evaluate replacements for methylene chloride in the solvent welding of an acrylonitrile-butadiene-styrene system (ABS) and a high-impact polystyrene (HIPS). Fourteen candidate solvents were experimentally considered. These were divided into three general categories: traditional, green and clean." A relative hazard rating was assigned to each solvent by taking the maximum concentration that the solvent could keep in equilibrium in a specified air space and dividing this value by the threshold limit value (TLV). Solvent welding was tested in both bond-in-tension and single-lap shear geometries. Parameters affecting resultant bond strength that were quantified included time polymer in contact with solvent time after surfaces joined temperature (pre- and post-bonding) contact pressure and vacuum."
Product Positioning in the INSITE* Technology Process
Over the last ten years Dow Chemical has been developing INSITE* technology using Speed" based principles to insure speedier development and faster revenue growth. One of the principles we have been using relates to using marketing to position our products to the various audiences required for a successful launch: our customers our competitors and our people. In general positioning products is not well understood in our company but it is critical to help shape people's perceptions of what is possible how this product relates to other products and what the value of the product is to the marketplace. By positioning INSITE technology and delivering new products to the marketplace Dow's image as a technology leader has been enhanced. The INSITE technology capability continues to encompass more opportunity and the credibility of the technology and products Dow launches grows. The process to establish a positioning and new product delivery are key elements to maximize the value not only of consumer products but also even differentiated commodities. Positioning is a key element in Dow's drive to launch INSITE technology and maximize value of the subsequent product lines."
The Role of Testing in the Failure Analysis of Plastics
Failure analysis (FA) of products and materials always requires careful observation of the general circumstances involved. The product failure analyst never overlooks external causes or environmental effects. All FA also requires a healthy dose of common sense and a 'Sherlock Holmes' investigatory sense. However, specialized material and product tests are also essential components of successful FA including: material mechanical properties, tests for composition and uniformity, residual stress tests, tests for contamination, identification and quantification of residual solvents, microstructural examination, and many more. An overview of general FA techniques will be presented, followed by specific examples of plastic FA. These specific examples will be discussed in detail, with special emphasis on the key findings derived from specialized laboratory testing. Examples will include plastic piping systems, consumer products, industrial equipment, and sporting equipment. Techniques discussed will include residual solvent identification by GC/MS, various spectroscopic techniques, optical and electron microscopy, thermal analysis, and mechanical properties testing.
Interfacial Tension, Phase Inversion and Co-Continuity in Poly(L-Lactide)/Polystyrene Blends
In this work blends of poly(L-lactide) (PLA) and polystyrene (PS) were investigated. The breaking thread method was used to measure the interfacial tension between poly(L-lactide) and polystyrene at 200°C. The complex viscosity and the storage modulus of the pure components were measured as a function of the frequency. L-PLA/PS blends were prepared by melt mixing the polymers in a Brabender mixer and the level of continuity has been investigated. The interfacial tension was found to be about 9.1 mN/m, whereas the phase inversion was determined to a PS concentration higher than 60%.
Biodegradable Plasticizers for Polylactic Acid
Poly(lactic acid) [PLA] is a well known biodegradable polymer which has been used in drug delivery systems, surgical repair systems such as sutures and bone fracture fixation pins and screws. PLA is biocompatible, has a high tensile strength, and has a high elastic modulus[1,2]. However, one drawback of PLA is the low elongation at break due to a brittle fracture while under tensile and bending loads. The elongation at break of PLA is typically 3 - 5 percent. The reason for this brittle behavior is due to physical aging which occurs during storage at room temperature and has been studied extensively. Plasticization is a common technique used to increase the ductility of a brittle polymer. In the case of PLA a suitable plasticizer must be miscible with PLA so as to decrease the glass transition temperature, as well as be biodegradable and nontoxic so as to provide a useful biodegradable blend. The advantages of the plasticization are low cost, ease of processing, and the ability to alter the properties of the blends by varying the amount of plasticizer. Use of a functionalized plasticizer can be more desirable such that a chemical bond is formed with the PLA polymer thereby preventing loss of the plasticizer through migration.
An Assessment of Dynamic Feed Control in Modular Tooling
An experimental investigation of the inter-cavity dependencies of a modular tool using Dynamic Feed control is presented. The results showed that part weight and overall part dimension are controlled by the individual command pressure to each cavity and the material's melt temperature. The weight and dimensions of a particular cavity appear independent of the control pressures set to fill the other cavity inserts. This was demonstrated to the extent that weight and dimension showed independence from a deliberate short shot condition in the hardest to fill part. There may be a minor synergistic effect of adjacent cavity pressure and the shorting part but this would need to be confirmed with additional experimentation. Once initially stabilized both traditional machine velocity control and Dynamic Feed weight variations were in the range of +/- 0.025% or less.
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