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.
The overall goal of the project targets the development of a product containing a rheology modifier additive in polyethylene (PE). This product is being sold to film converters for addition to the extruders of blown-film lines together with LLDPE resins. This increases the melt-strength during processing and the shrink tension for collation shrink films, enabling reduction in LDPE content and resultant tougher films. A tougher film will allow down-gauging and hence reduce material consumption, increasing the sustainability component for customers. This study focuses on the development of an analytical method at Dow to measure the concentration of the rheology modifier additive in PE. The method was validated and implemented successfully.
Advances in nanotechnology and surface sciences have necessitated superior polymeric coatings with novel applications. Urethane-acrylate-based interpenetrating polymer networks are one such class of ultra-tough polymers being researched actively for their wide-ranging applications from bullet-proof vests to binders for super dewetting coatings. Urethane-based systems are well-known for undergoing side reactions which could result in instability of colloidal suspensions engendering gelation resulting in significantly reduced shelf life of synthesized formulations and coating inconsistencies over time. Consequently, it becomes crucial to examine and control the factors inducing gelation. In this study, we investigate two approaches to prevent the gelation of colloidal urethane-based suspensions. In the first approach, we tune the NCO:OH ratio, and in the second approach, urea groups were formed in the presence of water. It was observed that both approaches resulted in storage stable colloidal suspensions with more than six months of shelf life. Durability assessment of coatings however indicated that urea-containing formulation resulted in notably robust coatings as compared to NCO:OH tuned coatings which can be attributed to the presence of strong hydrogen bonding arising from bifurcated hydrogens of urea.
The extraction of cure-dependent fatigue behavior under tension-tension fatigue is presented for filament-wound coupons. Displacement controlled fatigue tests are performed on tubular filament-wound coupons. The state of the tube is characterized by performing interrupted static tests in between the fatigue cycles. At the coupon level, the state of damage in the matrix is obtained using micromechanics expressions with the help of Digital Image Correlation (DIC) technique. The results show a noticeable difference between fully cured (95%) and 80% cured composite specimens.
Foamed parts are being produced in ever greater quantities. This is done, on the one hand, to save weight and, on the other hand, to take advantage of the greater design freedom in the layout of foamed components. Until now, quality control of the foam structure has hardly been possible without destructive testing methods. Therefore, a test method is presented to qualitatively evaluate the foam structure of foamed components without destruction.
This work explores the effect of core shell rubber (CSR) addition on the resulting properties of a highly crosslinked bi-component epoxy resin blend. The effects of network structure and topology are explored and related to the efficacy of CSR as a toughener for rigid, high-Tg polymer networks. A combination of thermal, spectral, and mechanical testing shows that excellent toughness enhancement can indeed still be achieved, despite a modest reduction in flexural properties for a high glass transition temperature (~259°C) network.
Nanocellular foam has attracted significant attention because of its superior physical and mechanical properties than microcellular foams. In this study, nanocellular foams were produced using the hot-bath and hot-press foaming methods. By lowering the saturation temperature (Tsat) to -30 ºC, the CO2 solubility was increased to 45.6%, and the cell size was reduced to less than 40 nm. Samples prepared by hot-bath exhibited smaller cell size, thinner solid skin, and transitional layer.
Polymers are inherently scratch sensitive due to their soft nature. Utilizing patterned surfaces while retaining transparency is a viable strategy to achieve better scratch performance. In this paper, we model the scratch behavior of micro-patterned surfaces using FEM simulation by employing a powerful coupled Eulerian-Lagrangian approach. The effect of two different pattern types on scratch behavior is studied and validated with available experimental results. Results suggest the significance of patterned surface topology in improving scratch performance.
In the effort to alleviate climate change and energy consumption issues, thermally insulating polymeric foams can improve energy-management efficiency. we report a superior thermal insulation (~28.5 mW⋅m-1K-1) microcellular foam from ethylene-norbornene (NB) based cyclic olefin copolymers (COCs). Unlike the traditional carbon-filled approach, the incorporation of more NB segments (content from 33, 36, 51 and 58 mol %) in the COC structure greatly improved its ability to block thermal radiation without increasing its solid thermal conductivity. Using the supercritical CO2 and n-butane as physical blowing agents, we fabricated COC foams with tunable morphology. The void fraction of the foams ranged from 50 to 92%, and they demonstrated a high degree of closed cell content (>98%). In COC foams with given cellular structures (e.g. void fraction of 90%, cell size of 100–200 μm and cell density of ~107 cells/cc), their total thermal conductivity decreases from 49.6 to 37.9 mW⋅m-1K-1 with increasing NB content from 33 to 58%, which is attributed to high- NB COC’s strong ability to attenuate thermal radiation.
Due to rising demands on the quality of the final plastic product, it becomes increasingly important to influence the thermal behavior of the injection molding tools. Due to this fact the geometry of heat control channels becomes very complex, leading to a change in the manufacturing strategy of large-scale tools: manufacturing of a layered structure followed by joining the complete component. Besides the influence of the surface roughness and precision of the mold making the possibility of joining non-planar surfaces is elucidated. To demonstrate and to evaluate the diffusion bonding process, a demonstrator injection-molding tool was constructed and realized by joining the nozzle side and the ejector site of the mold by diffusion bonding after the contour conformal cooling channels were integrated. The cycle time for the production of fan wheels with the finalized mold could be reduced by 10%. Moreover, the concentricity of the fan wheels could be improved.
The material properties of fiber reinforced plastics are highly directional and the final fiber orientation can usually only be determined after the manufacturing process by time-consuming and cost-intensive sample preparation. The determination of the mechanical properties usually requires destructive testing. Compared to conventional methods, the method of ultrasonic birefringence presented here allows a non-destructive determination of the shear moduli G13 and G23. Furthermore, it allows the determination of the fiber orientation without the need of a complex specimen preparation. The difference in shear modulus measurement between the two methods is less than 1%.
The purpose of this research is to develop measurement devices and verify whether the permeability values obtained by different experimental devices and theoretical models are correct through Moldex3D RTM simulation tool. The experimental mold dimension and process parameters are established in Moldex3D for verification, such as one-dimensional flow and radial flow. From the results, it is known that the experimental and simulation results are highly consistent. Therefore, Moldex3D simulation software can be used as a verification tool to compare the permeability and flow front.
Background: In Spring of 2020, Instaversal was contracted to test our newly developed conformal cooling technology, CoolTool™, against existing production benchmarks for a plastic injection molded Pipe Bracket Adapter. The Product Innovator was going through a period of elevated demand where the current cycle time of the existing injection mold tool prohibited them from meeting their demand. When cooling cycles were sped up this led to higher scrap rates due to sink marks. This left the Product Innovator with two options: delay delivery of the product to their top customer with the risk of losing the sale and potentially losing the customer or to invest in additional injection mold tools to double production capacity. To meet the customer’s demand, 100,000 parts needed to be produced in a 60-day time period. This request created conflict with the contract manufacturer. They were being asked to absorb the cost of additional molds to meet the timing or run full 24-hour (Monday-Friday) shifts over the 60-day period which would create losses in revenue by eliminating other clients’ scheduled jobs.
Effect of the thermal barrier coating (TBC), deposited on the mold for plastic injection molding was investigated. The mold cavities were coated by yttrium stabilized (YSZ) and phosphorous doped (PDZ) zirconium dioxide as multilayer film using chemical vapor deposition (CVD) method. It was found that films deposited at higher temperatures have better thermo-insulating properties than films deposited at lower temperatures. Growth rate and film porosity increase as deposition temperature increases. It was observed that the TBC slightly affects the flow length of the plastic melt but improves the filling ability of poorly vented molded part areas.
ASTM F1980 provides a methodology for accelerated aging of sterile barrier systems for medical devices, and is also widely used as the definitive guide for accelerated aging of medical devices and pharmaceutical packaging. ASTM F1980-16, as well as previous versions going back to 2007, emphasize that when increasing temperature to accelerate aging, it is preferable to decrease relative humidity so as to maintain an approximately constant moisture content. However, there is a revision under consideration by the ASTM F02.50 committee that would dramatically change this guidance to indicate a preference (although allowing for other options) to keep relative humidity approximately constant. This change is based on somewhat limited test data and literature review published recently by Thor et al. In this paper, we perform a study looking at eight resins (PP, COC, ABS, PC/PET, Copolyester, PBT, PA66gf, PUR) that have been aged at 60C and three different RH levels to evaluate the impact on aging. Our findings to date indicate that: (i) yes, it is likely that RH should be held constant when increasing temperature in order to keep moisture constant in the resins at a similar level; and (ii) for the medical-grade resins evaluated here, RH level does not significantly impact the physical aging mechanism. We also recommend that further accelerated aging studies are performed to more thoroughly evaluate the impact of moisture content on Q10 factors, corrosion rates, and other endpoints before this dramatic change is made to the ASTM F1980 standard.
The viscoelastic properties of carbon fiber reinforced thermoset composites are of utmost importance during processing such materials using composite forming. The quality of the manufactured parts is largely dependent on intelligent process parameter selection based on the viscoelastic and flow properties of the polymer resin. Viscoelastic properties such as the complex viscosity (η*), storage modulus (G’), loss modulus (G’’), and loss tangent (tanδ) are used to determine the critical transition events (such as gelation) during curing. An understanding of the changes in viscoelastic properties as a function of processing temperature and degree of cure provides insight to establish a suitable processing range for compression forming of prepreg systems. However, tracking viscoelastic properties as a function of cure during the forming process is a challenging task. In this current work, we have investigated the effect of sample size and adhesive type on the rheological properties of a commercially available carbon fiber prepreg material. Specifically, determining the linear viscoelastic region (LVE) as a function of sample configuration and different adhesive chemistries were explored. The results suggest that the square-shaped sample geometries coupled with cyanoacrylate based adhesive are optimum for conducting rheological characterization on the carbon fiber prepreg system.
The post-consumer single-use polyethylene-based plastic bags supplied by the supermarket grocery stores, are converted into new materials with improved mechanical properties using a thermo-mechanical recycling process. The low-density polyethylene (LDPE) sourced from waste plastic bags, is injected into a high shear internal mixer and compounded with the additives such as acrylonitrilebutadiene copolymer or nitrile rubber (up to 10 wt%) and also treated with an organic peroxide curing agent. The resultant materials exhibit high ductility and elasticity, with a maximum tensile strength of 20.3 MPa, stiffness of 1262 MPa, elongation of approximately 500%, and impact strength of 62 kJ/m2 depending on materials compositions. These mechanical properties are profoundly higher than those of neat recycled LDPE. It is observed that the post-consumer plastics contain a significantly high amount of calcium mineral of approximately 30 wt% (13 vol %), which plays a key role in improving mechanical properties during high shear blending with additives such as nitrile rubber. The melt-rheological characteristics such as complex viscosity and storage modulus of the materials are analyzed to evaluate the thermal recyclability and thermoplastic nature of the materials.
Presently, polymers such as high density polyethylene(HDPE) are utilized for an extensive array of applications because of their low weight, economical production, and exceptional physical and chemical properties. Thermal analysis and rheological measurements are the ideal techniques for characterizing the material properties of polymers. This paper employs thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and capillary rheometry to collate the contrasting nature of two HDPE resins. These resins will be referred to as HDPE A and HDPE C and are similar to two resins (Sample A and Sample C) included in a previous publication  that focused on blow molding parison sag and swell. TGA was used to investigate the thermal stability of these polymeric materials, as they were ultimately decomposed inside a furnace. DSC was conducted to examine the thermal transition behaviors of the polymers. Capillary rheometry was run to construct shear viscosity and extrudate swell versus shear rate data through single and twin bore configurations under varying temperatures. These measurements were conducted under testing conditions that are representative of industrial processes, such as extrusion blow molding. HDPE C was found to exhibit greater extrudate swell than HDPE A, as measured by capillary rheology measurements, and these data correspond to the earlier published results that Sample C exhibited greater parison diameter, thickness, and weight swell than Sample A as measured with a lab scale extruder.
In high pressure hydrogen environment, elastomeric seals undergo degradation of mechanical properties and wear problems. Especially, wear of elastomeric seals causes failure of sealing system. Therefore, developing the material with good mechanical properties and wear resistance is important. In this study, five ethylenepropylene-diene-monomer (EPDM) with different content of plasticizer were prepared to investigate the effect of plasticizer on their tribological properties after the specimens were exposed to high pressure hydrogen.
In this study, the stress corrosion crack (SCC) growth model for the cracked round bar (CRB) specimen was developed. The axisymmetric crack layer (CL) theory for simulating the slow crack growth (SCG) behavior of CRB specimen was modified to consider the chemical degradation due to diffused aggressive environment. The diffusion of oxidative fluid into the process zone (PZ) in radial direction is considered. Also, the chemical degradation kinetics of PZ materials due to the oxidation were modeled. The proposed model was shown that the discontinuous SCG behavior and the deteriorative effect from the chemicals were successfully simulated.
Smart materials that can adapt their mechanical response in the presence of an external stimuli are popular for their applications in 4D printing. Such printing methods exploit a smart material’s capability to interact with these stimuli to impart controlled material deformation tailored to specific applications. A modified percolation model was formulated to predict the dynamic transition exhibited in polymer composites containing cellulose nano-crystals (CNCs) which undergo mechanical softening in the presence of water. Coupling the effects water diffusion to the degree of CNC connectivity provided a method to capture the dynamic softening of CNC-based, water responsive smart materials as a function of filler loading. This modeling approach can be implemented to develop humidity sensing actuators and water-sensitive shape memory devices.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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