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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Electric Field Tailoring of Single Wall Carbon Nanotube and Carbon Nanofiber Polymer Composites
The performance of nanocomposites is affected by dispersion and patterning of the nanoinclusions in the polymer matrix. The main goal of this study is to manipulate high aspect ratio nanoinclusions such as carbon nanotubes (CNTs) and carbon nanofibers (CNFs) in polymers using AC electric fields to tailor the mechanical and electrical properties in the resulting composites. While the electric field is applied, the polymer is cured to freeze-in the alignment. The specific objectives are: to achieve efficient dispersion of the nanoinclusions in the polymer solutions; to investigate the alignment in liquid polymers in terms of electric field magnitude and frequency; and to quantify the alignment using electrical characterization in the liquid state.
Stress-Strain Behavior and Crystallization during Uniaxial Drawn PET/MMT Nanocomposites above Glass Transition Temperature
Uniaxial tensile tests of poly (ethylene terephthalate) (PET)/montmorillonite(MMT) nanocomposites were preformed over a temperature range of 85°C-105°C and stretch rate of 7.5mm/s-12.5mm/s. The stress-strain curves consisted of three regions: the linear visoelasticity, the rubbery plateau and the strain hardening. The effects of temperature and stretch rate on stress-strain behavior were discussed. The results of differential scanning calorimetry (DSC) measurements indicated that the stretch lead the increase of the crystallinity degree of specimens. The wide angle X-ray diffraction (WAXD) measurements revealed that the more perfect crystal structures were obtained with the increase of temperature and oriented along the stretch direction.
Structure Development and Mechanical Property Changes of Stretched Syndiotactic Polystyrene Film
In the study, we prepared uni- and biaxially stretched syndiotactic polystyrene films with various stretching ratio. As increasing stretching ratio, the film exhibited a cold crystallization peak while heating. The area of the cold crystallization peak was reduced with increasing stretching ratio, and the peak temperature lowered. Biaxially stretched films showed sharp and large cold crystallization peak compared to uniaxially stretched films. It was found that the Young's modulus and tensile strength generally increased by stretching ratio. The elongation at break was enhanced by increasing stretching ratio.
Rheology-Based Pore Size Estimation in Polyacrylamide Hydrogels for DNA Analysis
The physiochemical properties of polyacrylamide hydrogels have made them important in a variety of biomedical applications including drug delivery, tissue engineering, and electrophoresis of charged biomolecules. In this paper, we perform a series of in-situ dynamic small-amplitude oscillatory shear measurements during photopolymerization of crosslinked polyacrylamide electrophoresis gels to investigate the relationship between rheology and parameters associated with the gelation process including UV intensity, monomer and crosslinker composition, and reaction temperature. These results are then combined with a simple model based on classical rubber elasticity theory to obtain estimates of the average gel pore size.
A Comparison of the Effects on Polypropylene Using Sterilizing Doses from Three Different Sources of Ionizing Radiation
The effects of high energy radiation on polypropylene were studied using three different sources of ionizing radiation: _, electron beam, high current X-radiation derived from electron beam sources. The deterioration of tensile, flexural and impact ductility were similar for specimens irradiated by each of the three sources in higher crystallinity formulations. At lower cr ystallinity, the differences were more substantial, generally involving crosslinking. These differences are attributed to the radiation exposure rates which vary in the reverse order to the degradation trend.
Tracking the Commercial Development Process
This paper will outline and detail successful commercialization best practices for plastics materials and processing systems. By understanding the distinct steps to a successful commercialization plan we hope to share a template that can be used to make the process shorter and/or more cost effective for industry participants.The template will require research will and due diligence in the following areas:Identify and explore all possible applicationsDetermine Technical deficiencies and develop a plan to address themIdentify and assess competitive technologiesDetermine total system cost for each applicationIdentify and understand Barriers in the Channel/Supply chain
Inter-Layer Adhesion in Co-Extruded Structures: Role of Melt Interfacial Viscoelastic Stresses during Flow through the Die
Interlayer adhesion between a polycarbonate (PC) layer and a PC-ABS blend layer, in 3-layer films made by melt coextrusion in a multi-manifold die, was analyzed using nonlinear viscoelastic (NLVE) die-flow simulations with POLYFLOW. These simulations showed significant extensional stresses in the interface vicinity where the two melt layers come into contact for the first time. A Viscosity Normalized Nonlinearity Ratio" parameter was defined to correlate the simulated interfacial melt stresses and the observed adhesion behavior. Larger deviation of this parameter from a value of 1.0 (large disparities in melt extensional configuration across the interface) corresponded to poorer observed peel strength."
Designing Injection Molded Bioplastics Products
The ongoing need to keep reducing trial-and error in product design definitely applies to plastics products, and perhaps even more to bioplastics. It remains essential to optimize unavoidable weak spots in injection molded products, such as flow weld lines. Critical product properties were investigated for a poly-hydroxybutyrate, an experimental wood fiber-filled poly-hydroxybutyrate, and a general purpose polystyrene for comparison. Specimens from products molded with poly-hydroxybutyrate were found to have quite good impact strengths in weld line regions. Certain non-trivial injection molding settings, which reduce the impact strength in neat product regions, were found beneficial for weld line properties.
Product Design Support for Nanocomposite Materials Application
Biopolymers offer sustainability advantages over oilbased polymers as well as unique new property profiles, in addition to the ones of oil-based polymers. Advantages of polymer nanocomposites include high reinforcing effectiveness at low additive concentrations, and greatly improved recyclability as compared with fiber-filled polymers. A project was initiated to address both practical nanocomposite behavior in products and product design with bio-based nanocomposites. Such design support is useful to facilitate conversion of new materials and technologies into design opportunities. Additionally, new and surprising opportunities may be very inspiring in early design stages.
Melt Intercalation/Exfoliation of Polystyrene – Sodium Montmorillonite Nanocomposites Using Sulfonated Polystyrene Ionomer Compatibilizers
Quaternary ammonium salts of sulfonated polystyrene (SPS) were used as compatibilizers for melt-intercalation of polystyrene and pristine Na-montmorillonite. Tetraoctyl ammonium SPS and tetra-decyl ammonium SPS ionomeric compatibilizers produced significant exfoliation and a homogeneous dispersion of the polymer-clay nanocomposites. The morphology of the nanocomposites was characterized by WAXD and TEM and modulus was measured by DMTA. Image analysis was used to measure the percentage exfoliation. Exfoliation increased with increasing length of the alkyl chain of the ammonium counter-ion of the SPS ionomer.
Migration of Surface Defects Thru Thickness of a Polymer Film during Thermoforming
Mechanism of defect migration from bottom to top surface of a sheet due to thermoforming has been investigated in this work. ABAQUS, a commercially available package was used to conduct finite-element analyses of point defects found on back surface of film/ sheet. It is postulated that these point defects are incorporated during sheet/ film extrusion process. In film/ sheet as manufactured they do not necessarily negatively impact Cl A surface finish. However, post-thermoforming they manifest themselves as dimples or craters on the first surface (exposed surface on final part, visible to eye). This may negatively impact Cl A surface finish of the thermoformed part. Recommendations to prevent such defects on the thermoformed part have been provided.
What Every Plastics Professional Should Know about Patents and Patenting- Part 3: Lawful Designing around Valid U.S. Patents
Claim elements and construction of claim terms define the intellectual property rights granted in a valid U.S. patent, Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996). As such, based on a claim element-byelement comparison, one may determine whether an accused product or process infringes (literally or under the doctrine of equivalents) a patent claim. Conversely then, carefully designing a product, a process, an apparatus or a chemical composition so that it falls outside the scope of the allowed patent claims would likely avoid potential successful infringement actions. This article provides an overview of literal infringement requirements and the test employed by the courts in determining infringement under the doctrine of equivalents.
Mechanical and Physical Properties of High Strength, High Conductivity Copper-Nickel-Silicon-Chrome for Mold Tooling
In the last 10 years, a CuNiSiCr alloy with thermal conductivity in excess of 100 W/m/K and a nominal hardness of 30HRC has been produced and marketed into the plastic injection and blow molding industries. The alloy is comprised of nominally 7% Ni, 2% Si, 1% Cr and a balance of Cu. We have tested wrought versions of this alloy produced by us as well as other manufacturers. We present the hardness, strength, conductivity and fracture resistance, and compare it with that of other high strength copper mold alloys. We also present actual cooling data for polycarbonate lenses molded in a 100 W/m/K copper insert vs. a tool steel insert as an illustration of the utility of high conductivity molds.
Failure Analysis of Gasoline Storage Assemblies
Failures occurred within tank assemblies used for the storage of gasoline. The cracking was observed in a significant number of assemblies that had been in service. The cracking was found within the injection molded spout in areas immediately adjacent to the surrounding blow molded tank body. The focus of this investigation was a determination of the nature and cause of the failures. The results obtained during the evaluation of the cracked components indicated that the failures occurred through slow crack initiation via a creep rupture mechanism. This paper will review some of the testing performed to characterize the failure mode and identify the cause of the cracking, while demonstrating the analytical procedures used in the investigation.
Reactor TPO: Innovations in Low Temperature Ductility and At-Press Dimensional Control
Material specifications for exterior TPO applications require materials which are highly ductile at temperatures as low as - 40°C. Practical impact tests such as pendulum impact on large part moldings, are simulated by multi-axial impact tests according to ISO 6603 or ASTMD3763 standards. In such tests, molded discs with a prescribed thickness (2-3 mm) are impacted at low temperatures (0 to -40°C) and impact speeds (2 to 7 m/s). Injection molded 3 mm thick discs from compounded TPOs using ethylene –? olefin copolymer elastomers are known to have total energy absorption of > 60 Joules and fail in ductile manner down to -40°C. A compounded TPO must use a particular PP, and 30-35% added elastomer to obtain such ductile performance. Thus, manufacturing complexity and an additional heat history had to be added via compounding to meet these specifications.In response, Dow R&D has developed a natural reactor TPO (product name Dow PP D143.00) which is fully ductile at - 40°C. This performance is the result of a product design based on specific elastomer design and MWD distribution while still being produced in the reactor. The resulting flexural modulus is greater than 900 MPa and coefficients of linear thermal expansion (CLTE) = 90-100?m/m·°C. This reactor TPO will meet the functional requirements for many bumper fascia designs. In cases where higher modulus and/or lower CLTE is required, talc filled master-batches are developed to allow easy dispersion within an injection molding press.
A Method for Quantifying Relative Interfacial Shear Stress in Mwnt/Polymer Composites
In order to better understand the micromechanical behavior of carbon nanotube filled polymers, the load transfer behavior and interfacial shear stress must be quantified. This paper presents preliminary work on an experimental technique for quantifying the relative interfacial shear stress in multi-walled carbon nanotube / polycarbonate composites. The procedure provides a comparison of the aspect ratio of the nanotubes pulled from a fracture surface. In addition, the correlation with pullout angle is discussed. This work showed a decrease in the aspect ratio and thus an increase in interfacial shear as a result of chemical surface modification to multiwall nanotubes.
A Durability and Adhesion Test for Fabric Covered Plastic Parts
The cross-cut adhesion test provides a rating for the adhesion of a surface material to a plastic substrate. The original ASTM standard D3359-02 for the cross-cut adhesion test was developed to measure the adhesion between thin paint films and flat, metal substrates. This test, however, is not well suited for three dimensional plastic parts that are covered with fabric. It will be shown in this study that improper cross-cut testing protocol can result in false failures and artificially low adhesion performance scores. A modified cross-cut adhesion test procedure is documented here that is based on the ASTM method and is applicable to fabric covered parts.
Effect of Screw Type on Development of Polymer Blend Morphology along an Extruder during Compounding
The morphology development of an immiscible polymer blend along a single screw extruder was investigated experimentally. Three different screw geometries were evaluated: one with conventional screw elements; the other two with a fluted and Pineapple mixing element, respectively. The experiments were conducted using a polypropylene/polyamide-6 (PP/PA6) blend. The samples of blends were collected from four different positions using specially designed sampling device along the extruder online during compounding and were then examined using scanning electron microscopy (SEM) to evaluate the morphology development. The results showed that the screw with a fluted mixing element appears to produce the finest morphology at the end of the extruder. The Pineapple mixing element, with a characteristic of chaotic mixing, facilitates to form thinner laminar layers of dispersed phase.
Hybrid Nanoclay-Rigid PVC-Wood-Flour Composites
This study examined the use of nanoclay reinforced rigid PVC prepared with a novel melt-blending approach as a matrix for PVC/wood-flour composites. The effects of nanoclay contents and chitin as coupling agent on the properties of the composites were evaluated. The flexural, tensile and dynamic mechanical properties of composites made with nanoclay reinforced PVC matrix and chitin were measured and compared to their counterparts made with unreinforced PVC matrix. The experimental results indicate that wood-plastic composites with properties similar to solid wood could be manufactured by tailoring the formulation, i.e., combining nanoclay, rigid PVC, wood flour, and coupling agent.
Micro-Injection Molding of High Aspect Ratio Features with Thermoplastic Polyurethanes
High aspect ratio (4:1) microscale features were injection molded using thermoplastic polyurethanes and silicon tooling and measured using atomic force and scanning electron microscopy. Direct filling of the features enhanced replication when compared to indirect filling (i.e., filling during melt pressurization). With direct filling, mold temperature and melt temperature equally impacted replication. For good replication, mold temperatures must selected to balance filling, stretching of molded features during ejection, and shrinkage of the features.
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