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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Experimental Investigations on the Plasticating Process in a Short Single Screw Extruder for Biopolymers
Compared to conventional single screw extruders, the ultra-short extruder has a completely different design. Therefore, the melting mechanism is also completely different. Experimental investigations in case of processing biopolymers like starch have shown first insight in the relations between process parameters, the place of melting and the energy conversion related to the melting process. Because the ultra-short extruder has no heating system, the plasticating process is only based on the conversion from drive power to friction. The variation of screw speed, feed rate and die resistance showed that mostly the screw is partly filled. This has an influence on the energy conversion and on melt temperature. Based on this knowledge, physical relationships between the parameters have been formulated in order to allow a further mathematical modelling.
Successful Defense Against Infringement
This personal narrative about involvement in a multimillion dollar patent infringement suit excites me even to this day. It actually involved work that I did in the1950s. The lawsuit took place in the 80s and involved over a year and half of preparation prior to trial in New Orleans. The infringement claim was based on an issued patent that involved a variation of a basic patent of mine which had been declared prior validity during a very active research era in which I introduced organotin/sulfur stabilization for polyvinyl chloride. At deposition time, the opposing attorney insisted that this case would not be settled out of court. At trial, the opposing attorney made a fool of himself and the case was decided in our favor. Because of continuing litigation elsewhere, the trial record was sealed and I was not allowed to testify in any similar case.
Rapid Cooling Crystallization in Thin Films of Linear Polyethylene
A rapid cooling technique has enabled us to study crystallization at very large supercoolings in the past, and is now well established for routine experiments on thin films. The results obtained for a series of polyethylenes, polypropylene, nylons and PET using the technique have enhanced current knowledge of the crystallization behavior of such materials at very high cooling rates. All the previous studies were carried out using thin films, 40 ?m or higher in thickness, and with embedded thermocouples. In the current study we will report the effects resulting from using films lower in thickness (~10?m) on the growth rate and morphology of linear polyethylene
Novel Metallocene Catalyst Phillips Loop-Slurry Based Polyethylene Resins for Extrusion Coating Applications
Significant advances in our abilities to synthesize novel polyethylene resins for extrusion coating applications are discussed. The new resins were largely equivalent to a conventional HP-LDPE resin in impact, tear, adhesion, sealing, extruder motor loads and pressures at comparable melt index values. Some resins closely approached the neck-in and drawdown of the HP-LDPE resin. These results are discussed in terms of the molecular and rheological properties of these novel resins compared to conventional HP-LDPE resins.
Observations and Insights into Some Unusual Rheological Behavior of Metallocene Catalyst Polyethylene Resins
The dynamic shear rheological behavior of polyethylene resins made using a single metallocene catalyst was measured and analyzed. We observed some unusual rheological behavior that, at first glance, was more reminiscent of the well-known behavior of highly filled systems. Specifically, the viscosity exhibited yield stresslike character with a sharp upturn in the low-frequency viscosity. The standard molecular weight distribution profile for these resins was generally unremarkable. The causes of this viscosity behavior were explored by further characterization of the molecular architecture and attributed to the presence of long chain branching selectively present in the highest molecular weight fractions of the polymers.
Torque and Speed Fluctuation on Polymer Processing Large Volume Kneader
Large volume kneaders are designed to handle highly viscous polymer processing. The unitary operations can be compounding, polymerizations, devolatilization or drying. Depending on the polymer viscosity in the kneader, the interaction of kneading elements induce a torque and force evolution on the shaft over one revolution. Since the torque load depends on the polymer amount and viscosity over the machine length, information about process data, shaft transport and helix angle have to be considered while superimposing the individual load distribution of shaft segments. Torque fluctuations lead to hydraulic drive system pressure fluctuations, which can lead to shaft speed fluctuations due to the hydraulic oil compressibility. The shaft inertia may amplify torque fluctuations on the drive shaft connection. These fluctuations were measured on lab and industrial scale kneaders. A three-dimensional model is presented, which allows accurate assessment of the mechanical design of the shaft and other kneader components.
Low Temperature Impact Modifier for Clear Polypropylene Applications
A styrene-ethylene/butylene-styrene (SEBS) block copolymer with enhanced rubber segment is used to modify homo polypropylene and random copolypropylene. The impact property of blends is analyzed based on the instrumented impact test, and the optical property is measured by haze and transmission tests. The results show that both impact strength and optical properties of blends are improved even with low addition of the unique SEBS. Another novel SEBS is also used to further improve the low temperature impact strength of random co-polypropylene without sacrificing the clarity. The findings can be applied in many packaging applications where both clarity and impact strength are desired. The mechanical, rheological and thermal properties of blends are investigated by flexural test, capillary rheometer and DSC respectively. Those results provide important guidance for optimizing the formulation.
Injection Molding Aliphatic TPU for Brighter Color Applications
TPU or Thermoplastics Polyurethane is divided into two families, aromatic and aliphatic TPU. Our focus in this paper is Aliphatic TPU. The demands on elastomeric plastics, particularly those destined for application where appearance is key are growing rapidly. Aromatic TPUs tend to turn yellow when exposed to sunlight or heat; this has prevented TPU from being used in automotive interiors applications or where brighter color retention TPU is needed.In this work, Elastollan® LP9273 (ester type aliphatic TPU) is compared to Elastollan C85A (ester type aromatic TPU) and Elastollan 1185A (ether type aromatic TPU). Various testing methods were applied to characterize mechanical and thermal properties; yellowness index, heat aging, QUV and weathering properties are discussed. Four different colors were examined (White, Tan, Grey and Blue). We found that Elastollan® LP9273 showed superior color retention when it compared to the other two materials.
The Effect of Polymeric Excipient Selection and Process Variables on Solid Drug Dosage Forms Using Hot Melt Extrusion
The selection of the polymeric excipient to be used in HME (hot melt extrusion) is a very important consideration. Excipients must be chosen such that the formulation can be processed at conditions where the components are not degraded. Further, excipient choice is expected to have a direct impact on the dissolution profile and API morphology obtained. Processing variables (e.g. extrusion temperature, equipment configuration, etc.) can also have a significant impact on the characteristics of the extruded material. The formulations used for this study included various grades of ethylcellulose, hypromellose, and polyethylene oxide with model drugs. The focus of this presentation will be on the impact excipient selection and processing variables have on dissolution profiles, API (active pharmaceutical ingredient) morphology, and formulation stability. Data will be presented that demonstrates varied dissolution profiles, as well as the successful generation of solid dispersions that survive 6 month accelerated stability testing.
Material Designation Code for High Performance Polyethylene Piping Materials
As the North American piping industry became familiar with both ASTM and ISO standards and test methods, the need to create a new material designation code for high performance polyethylene piping materials also became evident. Over the last few years, much effort has been expended to reach industry consensus on developing a new material designation code. This paper informs the reader of the actions taken in the standards development process to create a new material designation code for these materials. Also this paper addresses the performance properties of PE 4710 materials and actions taken to-date in incorporating the new material designation code in application standards.
Structure Development of Various Polyolefins in Injection Molding
There have been no systematic comparison studies of structures in injection moldings of the various commercial polyolefins.We have investigated crystallization and orientation development in injection molding of various polyolefins, which include high density polyethylene (HDPE), isotactic polypropylene (i-PP), isotactic polybutene-1 (i-PB1) and isotactic poly(4-methyl pentene-1) (i-P4MP1). We used both volumetric injection speed and injection pressure control as the main processing parameters with varying packing pressure and thermal condition based on injection melt and mold temperatures, similarly related to the crystalline melting points.The effort to take into account of these variations on structure development was combined with considerations of crystallization kinetics and rheological properties of raw materials.
Filament-Like Polyaniline-Polypropylene Based Electro-Conductive Composites
The effect caused by adding a polyaniline (PANI) complex (PANICX) on the electrical conductivity and microstructure of (PANICX)-polypropylene (PP) filamentlike composites with contents ranging from 1 to 50 wt.% of PANICX was studied. The composites were produced following an in-situ deformation process using a laboratory single-screw extruder and a capillary die. The microstructure was analysed using optical and scanning electron microscopy techniques. The conductivity was calculated using a Keithley electrometer. The variation of the composites conductivity with respect to PANICX content was observed to be characteristic of a percolating system. The electro-conducting phase was deformed into elongated structures embedded in the bulk of the PP and preferentially oriented in the extrusion direction.
Bulk Polymerization of Methyl Methacrylate in a Kneader Reactor
The bulk free radical polymerization of methyl methacrylate (MMA) or the bulk free radical copolymerization of MMA based monomer recipes face a gel effect (Trommsdorff’s effect) and exothermicity. The kneader reactor offers a perfect combination of surface renewal and evaporative cooling to control temperature at high conversion (85 to 95%).This type of reactor can be tested batch-wise to optimize the recipe, such as concentrations of initiator and of chain transfer agent. A simulation program was correlated to experimental batch data to determine the optimum concentrations of initiator and of chain transfer agent to target a given molecular weight.
Iso-Strain Force-Temperature Test (IFTT) - Probing Transitions and Stress and Thermal History in Polymeric Materials
A new thermal-mechanical test method, Isostrain Force-Temperature Test (IFTT) is proposed in this paper to study the thermal behavior of polymeric materials. This method was utilized to investigate thermal properties of different forms of polymeric materials with inherent anisotropy, such as fibers and films. A variety of polymeric materials were examined. The examined materials include fibers of Kevlar®, and Spectra®, and films of Teflon®, bisphenol A PC and PET. This study provides important thermal properties of the studied materials including sub-Tg transitions or relaxations, glass transition, melting, and the stress and thermal history they experienced. Some information, which is difficult to probe using other thermal characterization methods, was disclosed for the first time.
Clay-Gelatin Nanocomposites of Improved Properties
Transparent clay-gelatin nanocomposite films were made through solution processing. These films exhibit enhanced physical performance. The Young’s modulus of the composite film was 8.3 GPa, almost 3 times that of gelatin alone, by dispersing only 10 wt% of one type of montmorillonite clay into the nano-sized phase in the gelatin. With the addition of the clay nanoparticles, the melting point of the gelatin increases and the crystallinity decreases.The property enhancements of gelatin are affected by the dispersion of particles (i.e., intercalation and exfoliation), particle properties (i.e., particle aspect ratio), and particle alignment, as studied by XRD and TEM.
An Empirical Model for Melting in Co-Rotating Twin Screw Extruder
In extrusion processes, melting strongly influences the development of product end-use properties such as tensile strength. For effective monitoring and control of these properties, it is essential to describe the melting process quantitatively. Obtaining a high-fidelity quantitative description of the melting process, however, remains a challenging problem. This paper proposes and employs an empirical modeling approach (similar to the identification" of dynamic systems from input/output data) to model the melting process. The recently developed "pulse perturbation technique" is used to generate the input/output data. Each parameter of the identified model can be associated with a distinct melting mechanism thus providing valuable quantitative insights into the melting process. Based on the melting data presented in  the model is used to analyze the effect of extruder operating conditions on the melting of semi-crystalline amorphous and rubbery polymers."
Coupled Filling and Cooling Analysis for Injection Molding
Conventional analysis such as MOLDFLOW divides the injection molding process into two different stages: filling and cooling. Filling analysis assumes both the cavity and core temperatures keeping constants during filling stage, while cooling analysis assumes the part temperatures in anywhere being constants. In this study, the temperatures between mold and part are assumed unknown and determined by solving both polymer and mold thermal problems. After ejection, the mold temperatures, inheriting from the last cycle, are memorized and used as the initial values for next cycle simulation. To keep the geometrical information consistency, both the part and mold are represented by solid models. The dual domains and conventional Galerkin methods are employed to solve the filling and cooling problems respectively. The coupled method can simulate the transient and more complicate thermal problems.
Weldability of Bio-Renewable Ultrasonic Exfoliated Nanocomposites
In this work the weldability of bio-renewable nanocomposites was studied. Soybean proteins were denatured in a glycerin solvent and plasticized with a screw extruder. The glycerin contained clay platelets that were exfoliated with high power ultarsonics (2.2 kW @ 20 kHz). Various levels of exposure to the ultrasonic energy were used to exfoliate the clay platelets resulting in nanocomposites with various levels of exfoliation. It was also seen that these materials were not effectively welded with hot plate welding; however, success was found with vibration welding where significant material pullout was seen at the faying surfaces after tensile testing.
Beam Shaping with Spatial Modulators for Laser Micro-Welding of Plastics
This paper reviews the use of diffractive optics for beam shaping of high-power lasers (100 W) for micro-welding of plastics. By using Fourier transformations on twodimensional complex arrays, spatial domain images were transformed into phase domain images. These images were then used to produce a mask for the microlithography etching of a glass diffractive optical element (DE). An 80 W fiber laser with a wavelength of 1084 nm was coupled in air to the lens to shape the beam into predetermined patterns. These patterns were then reduced with standard optics to a desired size. The images were focused at the faying surface of two plastic components in a through-transmission weld configuration. Weld quality was assessed based on fidelity, burst pressure and consistency. The resulting welds were able to support burst pressures as high as 0.6 MPa. In addition weld features as small as 300 ?m were also produced.
Coupled Temperature, Diffusion and Squeeze Flow Model for Interfacial Healing Predictions
This paper reviews work done to determine weld strength as a function of temperature history fields at the faying surfaces of welds. In order to simplify the resulting models, isothermal conditions were assumed by welding relatively thin films with impulse welding. Furthermore, the weld geometry was clearly defined by accurate placement of an overlap weld geometry. It was found that healing of the weld can be better defined as a function of time and temperature instead of temperature alone, as historically done. By combining squeeze flow of asperity peaks and reptilian diffusion models into one model, it was shown that by using an Arrhenius Equation as a function of temperature and time one can accurately predict weld strength and degree of healing.
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