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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Micromechanical Analysis of Interfacial Shear Strength of Aramid Fibre Reinforced Thermoplastic Elastomers
For the majority of composites and their intended applications, the transfer of stress from the point of application throughout the remainder of the composite structure is by a shearing mechanism. The interface between fiber and matrix therefore, plays a major role. This paper examines the drawbacks from conventional micromechanical testing of model composites and introduces the benefits of fragmentation testing of aramid fibers in a thermoplastic elastomer matrix using Raman spectroscopy. Accurate and precise measurements of the interfacial shear strength between fibers and matrix are attainable.
Tg in Polymer/Oligomer Athermal Blends
The glass transition behavior of poly(?-methyl styrene), its tridecamer, and an athermal blend with its hexamer is investigated using differential scanning calorimetry. The glass transition, Tg, of the blend is found to become broader than that of the pure materials. However, the absolute heat capacity of the blend remains unchanged. The length scale of the cooperatively rearranging regions of the samples, as well as previously studied pentamer, polymer, and blends, is estimated from Donth's fluctuation model. The broadening of Tg is found to accompany a decrease of the length scale. In addition, the correlation between Tg, fragility, and the length scale of CRR is also examined.
Crystallization of Shape Memory Polymer Blends
Shape Memory Polymers (SMP) blends are of particular interest because they are easily processible, commercially available and recyclable. In this paper we study blends of PVDF (semi-crystalline, Tg=-35 °C, Tm=173 °C) and PVAc (amorphous, Tg=33 °C) which are miscible at all blending ratio (presence of a single Tg). Effects of composition as well as thermal histories on crystallization were investigated via differential scanning calorimetry (DSC), parallel plate rheology and polarizing optical microscopy (POM). For the first time, evidence for two distinct crystalline forms was observed in a blend with PVAc and PVDF crystallized for all blending ratios. Rheological measurements show that the rubber plateau of the blend decreases with lower PVDF content because of lower density of physical crosslinks. Surprisingly, in the case of 30:70 PVDF:PVAc the highest rubber plateau was achieved by isothermal crystallization at temperature close to, but above, the crystallization point measured by DSC. Comparing rheological and optical results for crystallization kinetic, it can be inferred that PVDF crystallizes faster near a solid interface than in the bulk.
Investigation of Reversed Shear Induced Melt Imbalances in Injection Molds
It has been proven that shear induced melt variations cause both cavity to cavity and intra-cavity filling imbalances. Cavity to cavity imbalances have been shown to result from the shear induced melt variations becoming separated in a runner branch. The high sheared outer laminates will follow the inside corner side of a branching runner and the low sheared material will follow along the opposite side of a branching runner. Unsupported theories suggest that these imbalances are a result of the local shear at the corner itself. This paper presents a study which shows that there is an additional phenomenon that occurs at the corner of a runner which is unrelated to either of the above mentioned theories, and that the effects are opposite. These opposite effects can be significant and are shown to cause filling imbalances of over 20%.
Multilayer Coextrusion of Polypropylene Nanocomposite Materials
A multilayer coextrusion die was used to create polypropylene (PP) / organoclay nanocomposites and to study the stress effects on clay dispersion. Nanocomposites contained 5 wt% maleic anhydride grafted PP compatibilizer and 1 – 5 wt% organoclay. Nanocomposite layers were extruded opposite talc filled PS before being separated. Individual PP nanocomposite layers were tested for improvements in mechanical, thermal and barrier properties and were compared to theoretical predictions in order to determine an aspect ratio for the organoclay. Aspect ratios from theory were compared to those measured directly through TEM. A PP nanocomposite / elastomer system was also considered.
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.
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