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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Birefringence Distribution in Injection Molded Parts with Weld Lines
The effect of processing conditions on the birefringence distribution in Polystyrene injection molded parts with weld lines was investigated. The gapwise averaged birefringence of injection molded parts was measured by photoelasticity method. Birefringence at weldline area generated by different obstacles was also investigated. It was found that melt temperature and packing pressure are the two dominant factors that determine the birefringence development of the molded parts. Birefringence distribution has an appreciable distinction at weldline area, which is attributed to the molecule orientation distribution, local flow behavior and melt meeting angle at the melt front.
Effects of Tooling and Injection Molding Conditions on Nanoscale Replication of Thermoplastic Elastomers
The effect of tooling geometry and processing conditions on the ability to injection mold nanoscale features was investigated for thermoplastic polyurethanes (TPUs). While pattern geometry was not as critical as feature size in determining good replication, TPUs exhibited enhanced replication quality when compared to a polycarbonate control. Melt temperature was limited by polymer degradation, but increasing mold temperatures provided better replication. Very high mold temperatures, however, did not improve replication and were detrimental to cycle time.
Ionic Liquids as Additives for Thermoplastics
In attempts to develop new process modifiers for thermoplastics, two ionic liquids with long chain hydrophobic cations and different anions were introduced in a biodegradable polymer. Methods of incorporation included melt blending, solvent casting and microencapsulation from w/o/w systems at concentrations up to 10 wt%. The modified polymers were characterized rheologically and by TGA to determine process and thermal stability, respectively, and by DSC to determine miscibility and types of the polymer-ionic liquid interactions. Potential applications in plasticization, lubrication and emulsification are discussed for selected polymer-ionic liquid combinations.
Development of Conducting Polymer Using Stabilized Gold Nanoparticles for Chemical Sensor
In this paper, we describe a method for preparing thiol capped Self Assembled Monolayer (SAM) of gold-nanoparticles. Because of the variety of functional groups that can be supported using SAM techniques and due to the relative stability of the monolayers generated, we believe these materials will be useful for developing a variety of chemical or gas sensors. Thiol-capped gold nanoparticles are used as conducting filler for poly dimethyl siloxane matrix in the detection of organic vapors. Thin films of nanocomposite is deposited using Continuous Ink-Jet printing system (CIJ) on the interdigitated microelectrodes (IDE) thus forming chemiresistors" and are analyzed by exposing to different analytes (N-methyl pyrolidine tetrahydrofuran methyl ethyl ketone
Vibration Welding of Hard TPO to Soft TPO
Hard and soft thermoplastic polyolefins (TPOs) have been used in the automotive industry for many years. Most of the applications did not involve interaction between these two materials. Recent developments have combined these two materials together. Therefore, there is a need to understand the weldability of these two materials.This study examined the weldability of these two materials using vibration welding in a T-joint geometry. A two factor and two level DOE was used to evaluate the weld strength of several TPE-TPO combinations. It was found that the weld strength was not sensitive to the welding parameters selected in the study. It was also found that the weld strength was dominated by the soft TPO used in the system, not the hard TPO. Additionally, the failure mode was also dominated by the soft TPO. A ductile failure mode was possible for some soft/hard TPO combinations with appropriate welding conditions. and toluene) at very low concentration and different relative humidity (RH). The chemo resistive response is measured by four- probe method for different analyte at various concentrations and the results show a linear profile of concentration vs. conductivity at different RH. The response time and percolation threshold vs. conductivity of this novel chemiresistor compares favorably over conventional carbon black (CB) polymer composite."
An Investigation on the Effects of Fine-Particulate Filler on the Properties of a Rotomolding-Grade Polyethylene
This paper examines the influence of adding a fine-particulate industrial by-product namely fly ash as reinforcing filler into a rotomolding-grade polyethylene. The compounds of various filler contents were added either by dry-blended or by-meltcompounded, and their rotomolded parts were analyzed to check fro their appearances, processabilities, and mechanical properties.In terms of rotomoldability, it was possible to add the filler up to about 10% without dramatically affecting the part removal capability. In terms of stiffness, a slight improvement was made at such filler loading; however, the impact properties were drastically reduced even a small amount of the filler was present.
Effect of Electron Beam Radiation on the Melt Rheology of Polyvinylidene Fluoride and its Copolymers
The effect of electron beam radiation on the shear and extensional rheology of polyvinylidene fluoride and its copolymers with hexafluoropropylene is investigated. The samples were exposed to low levels of radiation ranging from 0 to 5 Mrads at room temperature. The shear rheology showed an increase in the storage modulus, as the level of radiation increased while the viscosity at high frequency remained unchanged. These results suggest the formation of chain branching and/or the formation of a second population of higher molecular weight. The results were corroborated using size exclusion chromatography combined with light scattering (SEC-MALLS), which confirmed both the presence of chain branching and the formation of a higher molecular weight tail. Extensional rheology showed strain hardening as the level of radiation is increased.
Effect of Process Conditions on the Micro-Domain Structure and Mechanical Behavior in Cylindrical Block Copolymer Systems
The effect that different process conditions have on the structural characteristics and the mechanical response of cylindrical block copolymers is investigated. It is observed that structural characteristics such as domain size and spacing change due to different process conditions and thermal treatment. Subtle changes in dspacing (from small angle x-ray scattering) are shown to correlate with the material's stiffness. This change is explained by the temperature dependant segregation between the styrene and rubbery phases at a particular process/annealing temperature.
Filling Balance Optimization by Best Gate Location
The quality of an injection molded part is strongly influenced by the filling balance of the mould cavity. This paper presents a method and the relevant software application to determine the best gate location for an injection molded part. The proposed optimization method automatically and iteratively calculates the gate position that maximizes the melt flows balance during the filling phase. The software is based on the Moldflow Plastics Insight®/Microsoft Visual Basic® interface and uses a non-linear optimization algorithm based on the Gauss-Newton and Conjugated Gradient techniques. The effectiveness of the developed method is demonstrated through some significant case studies.
Solubilities of Blowing Agent Blends
Investigating the solubility of blowing agent blends in polymer and the phase equilibrium of multicomponents mixture system is a challenge due to the following reasons: (1) the composition ratio in the vapor phase is not the same as the composition ratio of blowing agents dissolved in polymer, and (2) one blowing agent has an effect on the solubility of the other blowing agent. This paper describes the general thermodynamic model that simplifies these investigations. The model is established by measuring sorption with a magnetic suspension balance, and not only predicts the overall solubility for the blowing agent blend but also calculates the solubility of each component dissolved in the polymer melt.
Potential Ultrasonic Compaction of Zein and Distiller's Dry Grain (DDGS)
As the demand for ethanol as fuel additive increases, a consequent rise in the production of distiller's dry grain with solubles (DDGS) and commercial zein is expected. Corn dry milling processing produces two major coproducts; ethanol and DDGS. In wet-milling, pure zein is a high value by-product of corn processing. This study evaluates the potential of ultrasonic compaction of zein and DDGS composites to produce biodegradable biorenewable plastics. Various amplitudes, compaction times and compositions were characterized in terms of tensile strength. It was found that samples could be formed within a few seconds with tensile strengths as high 12 MPa.
Study of Orange Peel Phenomena in Rotational Molding
The term orange peel" describes a surface defect that is characterized by irregular grooves and pitting—much like the topography of the outer skin of an orange. Although similar phenomena have been reported for high-pressure processes such as injection molding the root causes of orange peel in rotational molding are essentially unknown. The presence of orange peel is undesirable not only for aesthetic reasons but also for its potential negative effects on the functional properties of the final product.A fundamental study was conducted to determine the root causes of the orange peel in rotational molding. The effects of material properties such as density rheological thermal and powder properties and process parameters were investigated. In addition comparisons are made between the dry blended and melt blended samples in terms of orange peel development."
Melt Blending Graphite into Poly(Ethylene-2,6-Naphthalate)
Graphite can be an attractive reinforcement for polymers due to its high stiffness and low thermal expansion as well as high electric conductivity. Graphite was melt blended into poly(ethylene-2,6-naphthalate) (PEN). After molding extruded composites into films via biaxial squeezing and uniaxial stretching, their stiffness, thermal expansion and gas barrier properties were tested. Even though graphite in PEN matrix appeared to form unintercalated or partially intercalated morphology, noticeable enhancements in composite stiffness and hydrogen barrier properties were observed. Less improvement in dimensional stability was found. We evaluated average aspect ratios of anisotropic graphite sheets embedded in PEN by interpreting experimental data with composite theories. Young's modulus and dimensional stability of composites were dramatically improved by film drawing.
Impact of Approximating the Initial Bubble Pressure on Cell Nucleation in Polymeric Foaming Processes
According to the classical nucleation theory, the free energy barrier for bubble nucleation and thereby the nucleation rate are functions of the bubble pressure, Pbubble. In computer simulations of polymeric foaming processes, almost all previous research has approximated the value of Pbubble by the saturation pressure, Psat. In this paper, the thermodynamic equilibrium condition and the Sanchez- Lacombe (SL) equations of state (EOS) are employed to determine the value of Pbubble. It is shown that the Pbubble approximation using Psat will lead to significant overestimations of the nucleation rate and the final cell density.
Influence of Surface Energy on Dispersion and Flexural Properties of PS/Phosphonium Organoclay Nanocomposites
Phosphonium-modified montmorillonite (PMM) organoclays were used to produce polystyrene (PS)/clay nanocomposites by melt processing. Two PS resins with different molecular weights were used, along with four different PMM organoclays. The structure of the resulting nanocomposites was characterized using wide angle X-ray and transmission electron microscopy. It was found that the quality of clay dispersion, nanocomposite thermal stability, and flexural mechanical properties depend on the combination of organoclay type and PS molecular weight. The differences are discussed in light of the interfacial tension values measured for the different PS/PMM systems.
Fast Acquisition Melt Pressure Measurements to Detect Flow Instabilities. A New Option for Capillary Rheometers
Flow instabilities cause various problems in extrusion blow- or flat film processes. Especially shark skin is affected by the molecular structure. This phenomenon is analyzed in various scientific works using apparatus that are complex or difficult in operation.A new set-up, now available is being presented as an option for new and existing capillary rheometers, consisting of a special designed die and a fast responsive transducers system. The software allows the evaluation of diverse pressure frequency regimes causing flow instabilities. Measurement examples are given for different shear rates and polymers. The measured frequency regimes are related to molecular parameters.
Casting of Zein Protein Polymers
This paper reviews an investigation of the processability and properties of commercially available corn protein polymers for cast film products. Different formulations of protein substrates were cast and characterized for their mechanical properties. In this study it was seen that zein plastic sheets could be cast with tensile strengths as high as 6 MPa with a strain to failure of 6%. In addition, ultrasonic treatment of the solution, prior to casting, reduced the tensile strengths; however, the treatment did enhance the strain to failure to as high as 200%. Lastly, the addition of nanoclays also reduced the tensile strength of the cast films.
Preparation of Gold Nanoparticles Filled Poly Dimethyl Siloxane Membrane for Gas Separations and its Reverse Selective Phenomena
A novel nanocomposite membrane, poly dimethyl siloxane (PDMS)/Au was prepared for carbon dioxide/methane separation. Synthesis of stabilized nano particles is also reported. The nanoparticles were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM). The hybrid membrane was characterized morphologically by scanning electron microscope (SEM) and the change in inter-segmental distance due to filler loading by wide angle X-ray diffraction patterns (WAXD). The gas transport properties were measured at different pressures and temperatures. The effects of filler loading on permselectivity, diffusivity selectivity and solubility selectivity are reported for CO2/CH4 separation. Reverse selective phenomena of PDMS/Au nanocomposite membrane over the conventional PDMS membrane is explained based on sorption kinetics of CO2.
Viscoelastic Flow in Micro-Injection Molding
Understanding the free surface flow of viscoelastic fluids in micro-channels is important for the design and optimization of micro-injection molding processes. In this paper, flow visualization of a non-Newtonian polyacrylamide (PA) aqueous solution in a transparent polymethylmethacrylate (PMMA) channel with microfeatures was carried out to study the flow dynamics in micro-injection molding. The transient flow near the flow front and vortex formation in microfeatures were observed. Simulations based on the control volume finite element method (CVFEM) and the volume of fluid (VOF) technique were carried out to investigate the velocity field, pressure, and shear stress distributions. The mesoscopic CONNFFESSIT (Calculation of Non-Newtonian Flow: Finite Elements and Stochastic Simulation Technique) method was also used to calculate the normal stress difference, the orientation of the polymer molecules and the vortex formation at steady state.
Novel PET Nanocomposites with Enhanced Barrier Performance of Interest in Food Packaging Applications
PET is one of the polymers most widely used in the packaging industry. However, it is highly desirable to enhance its barrier properties for applications such as carbonated drinks and for other rigid and flexible packaging applications. The nanocomposites route offers unique possibilities to enhance the properties of this material, provided that adequate thermally resistant and legislation complying nanofillers are used. This paper presents novel nanocomposites of PET with enhanced barrier properties to oxygen, water and d-limonene based on a new specifically developed food contact complying montmorillonite grade. Morphology and thermal properties are also discussed as a function of filler content.
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