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Failures occurred within threaded fasteners used in an outdoor industrial application. Specifically, cracking was observed within fasteners used to terminate a pipe conveying a gaseous chemical product. The parts had been installed leak free as verified through leak testing. However, failures occurred within some of the installations between four and five years, as identified by leakage of the gaseous project. A failure analysis identified that some of the fasteners had cracked through a mechanical short-term overload mechanism in which the stresses applied during installation exceeded the short-term strength of the material. Other parts, however, cracked through creep rupture, whereby the applied service stress exceeded the long-term strength of the material. In both cases, crack propagation and ultimate rupture was associated with the creep properties of the material. A material conversion was considered to increase the creep performance of the fasteners. This paper will review the testing performed to characterize and compare the creep performance of the incumbent and proposed materials.
Johannes Rudloff | Marieluise Lang | Thomas Hochrein | Martin Bastian, May 2021
The co-kneader is well known for its superior mixing performance and its exact temperature control capabilities. Therefore, it is widely used in the polymer industry for the compounding of shear- and temperature-sensitive materials. In contrast to the considerable amount of scientific work that deals with investigation, modeling or simulation of the process behavior of single and twin screw extruders there are only few studies about the co-kneader. Due to increased quality requirements and the trend for cost reduction by process optimization, this is increasingly becoming a problem for plant construction and processing companies. To address this problem, experimental investigations of the melting behavior of polymer materials in the co-kneader were conducted. In order to determine the melting degree along the extruder length a special barrel was used which can be opened in axial direction. Based on the experimental results, a theoretical consideration for co-kneaders that are operated as plastification extruders is proposed. Therefore a disperse solid melting model is used. A comparison between simulated results and experimental data shows a descent agreement, when the point of melting initiation is estimated accurately.
Hatice Malatyali | Volker Schöppner | Seyit Ali Akar | Felix Hanselle | Laura Austermeier, May 2021
The twin screw extruder is used for processing of plastics. One of the most important processing tasks is the preparation of plastics with fillers and reinforcing materials. For the processing of fibers various recommendations can be found. But in an industrial production, with the same specification and process parameters, the resulting fiber length may differ. These variations must be clearly defined and determined. While process deviations occur during compounding, measurement deviations can be detected in the fiber end length measurements. In order to evaluate the experimental investigations and to use it for model validations, the corresponding deviations must be known beforehand. Within this paper, a reproducibility study will be carried out to ensure the reliability of the experimental investigations. The aim of the work is to determine the fiber length degradation along the screw and their deviations. The investigations in this paper are showing that a producible fiber length reduction is possible.
Piyapong Buahom | Chongda Wang | Mohammed Alshrah | Chul B. Park | Guilong Wang | Pengjian Gong | Minh-Phuong Tran, May 2021
This work developed a mathematical model for the correlation between the cellular structure and the thermal conductivity of closed-cell microcellular and nanocellular insulation foams. Because convection is negligible in such confined structures, the model includes the contributions from thermal radiation and conduction through the solid and the gas. The conduction term included the effects of gas volume fraction, fraction of solid located in struts and cell walls and the Knudsen effect in the gas. The radiation term was determined by analyzing absorbing-scattering-reemitting radiative heat transfer based on Mie’s scattering theory, interference of propagating waves and tunneling of evanescent waves. Validated by the measured thermal conductivities in the literature, the model was used to predict the thermal conductivity of polystyrene (PS) poly(methyl methacrylate) (PMMA) foams at various volume expansion ratios and cell sizes. It was found that the radiative contribution plays a crucial role in nanocellular foam because of the thinner and highly transparent cell walls and struts. The balance between conduction and radiation leads to the optimal expansion ratio and the optimal cell size at which the thermal conductivity was minimized.
Laura Restrepo-Uribe | Nicolas Ioannidis, May 2021
The solubility and dissolution enhancement of the poorly soluble drug ketoprofen (KTO) in polymer blends prepared by hot melt extrusion was studied using two different twin screw configurations while changing extrusion processing parameters. Soluplus and Kollidon SR blends were used as solid dispersion excipients. A design of experiments with three melt temperatures, three screw rotation speeds, and three fill factors was performed. Different characterization techniques such as differential scanning calorimetry (DSC), optical and polarized light microscopy, X-ray diffraction (XRD), solid-state nuclear magnetic resonance (ss-NMR), and dissolution testing were used. The results from DSC and XRD showed an amorphous solid solution. An optimal processing condition by twin screw extrusion was found for each screw configuration achieving more than 80% drug release in 8 hours.
Sejin Han | Franco S. Costa | Renn Chan Ooi, May 2021
This paper presents a study on flat-panel warpage deflection using experimental and numerical methods. The study was done for various silicon-die densities and panel thicknesses. The package was produced by compression molding, and the warpage was measured after the molding. The numerical warpage analyses were performed using both linear analysis and geometrically nonlinear analysis techniques. Comparison of the experimental and simulation results show that the geometric nonlinear warpage analysis produces results which better match the experimental results.
Carbon black filled immiscible polymer blends are specialty materials used for a variety of applications. The present work utilizes statistical approach to understand the controlling parameters of crosslinking and resulting mechanical properties in ethylene vinyl acetate copolymer (EVA)/acrylonitrile-butadiene copolymer (NBR)/carbon black (CB) conductive polymer composites. The influence of varying composition on material properties was investigated. Statistical analysis was used to model the overall crosslinking behavior and mechanical properties of the composites. Crosslinking in these composites seemed largely dominated by radical concentrations only. Mechanical properties were modeled well by degree of crosslinking and CB loading for the ranges of composition tested.
Ursula Stritzinger | Wolfgang Roland | Hanny Albrecht | Georg Steinbichler, May 2021
Twin-screw extrusion modeling is in most cases based on analytical approaches that are build on considerable geometric simplifications. These approaches give only rough estimations of the processing behavior. More accurate predictions generally require numerical methods with less drastic simplifications. In this work, we analyzed the pressure-throughput behavior in fully-intermeshing double-flighted kneading blocks. First, we conducted a dimensional analysis based on the Buckingham Π-theorem. Second, for each staggering angle, we determined the characteristic angular position that describes the mean throughput. Based on this position, a parametric design study was carried out by varying the identified dimensionless parameters. To solve the complex flow patterns, 3D CFD simulations were conducted. For each design point we evaluated the dimensionless drag flow-rate and the dimensionless dam-up pressure. As an addition to the two established dimensionless conveying parameters A1 and A2, we propose a novel conveying parameter A3. This new parameter simultaneously enables the description of conveying and non-conveying kneading discs. Our results offer considerably deeper insight into the conveying characteristics of kneading blocks. In addition, they can serve as foundation for screw design and process modeling. For a better understanding of the process, we additionally investigated the power consumption and viscous dissipation in Part B of this publication.
Wolfgang Roland | Ursula Stritzinger | Christian Marschik | Georg Steinbichler, May 2021
Modeling twin-screw extrusion is commonly based on significant geometric simplifications such as the representation of the flow domain as flat channels. Furthermore, the prediction of the conveying characteristics and power demand of kneading blocks is typically based on their approximation as conveying elements. Considering the accurate flow geometry of fully intermeshing co-rotating twin-screw extrusion kneading blocks we analyzed the power characteristics by means of three-dimensional numerical simulations for Newtonian flow. Therefor we first conducted a dimensional analysis to identify the dimensionless characteristic influencing parameters. Next, we derived novel dimensionless power parameters and then conducted a parametric design study. Our proposed power parameters are capable to simultaneously cover conveying and non-conveying screw elements. The results provide new insights in the power characteristics of kneading blocks and are fundamental for screw design, screw simulation, and scale-up. In Part A. [1] of this work we focused on the conveying parameters.
A thermodynamic theory was applied to predict compatibility between a completely biobased epoxy adhesive and substrate. Single lap shear strength samples were also prepared to confirm the correlation. Using this theory, equations were defined that could predict the type of failure and the failure strengths observed.
Thin polymer films with high Coefficient of Friction (COF) often perform poorly on packaging lines due to their tendency to buckle or elongate under stress. Film buckling, leads to inconsistent package dimensions and other flaws. Lowering the film’s COF by addition of slip agents reduces drag or unbalanced forces during converting can improve the packages’ dimensional consistency. However, since friction can never be eliminated, reducing COF offers limited utility. Improving the film’s buckling resistance by increasing bending stiffness may be a practical, complimentary strategy to resolve film buckling. A better understanding of the combined effects of film COF and bending stiffness can help manufacturers optimize multilayer films without increasing gauge or sacrificing key performance criteria.
The purpose of this study was to evaluate the combined effects of bending stiffness and COF on the convert-ability of films in vertical form-fill-seal pouch (VFFS) lines. Specifically, we examined dimensional changes in VFFS pouches made using similar films with variable bending stiffness and COF values. The results suggest that films with the right balance of high bending stiffness and low COF exhibit less buckling and are less prone to tracking, bunching or slipping issues in VFFS conversions. A proposed mechanism is provided to explain how high COF and low bending can lead to unbalanced forces in the film and inconsistent dimensions in the finished package.
Fatoumata Ide Seyni | Lawrence Barrett | Steven Crossley | Brian P. Grady, May 2021
An asymmetric double cantilever beam (ADCB) test was used to determine the ability of carbon nanotubes with varying chemistry along their length, i.e. diblock nanotubes, to strengthen the polystyrene/poly(methyl methacrylate) (PS/PMMA) interface. PS molecules were grafted primarily to one of the blocks to cause that block to migrate to the PS phase since otherwise both blocks would prefer to reside in PMMA. Fracture toughnesses increased monotonically with increasing diblock carbon nanotube concentration and maximum values were similar to that for block copolymer reinforced interfaces while single-chemistry nanotubes showed no reinforcing effect. However, the abrupt increase in fracture toughness with added compatibilizer indicative of a transition to crazing was not found consistent with nanotubes suppressing crazing in homopolymers. Significant aggregation was visibly present, which likely reduced the interfacial thickness toughening possible.
The role of polyrotaxane (PR) on the scratch behavior of poly(methylmethacrylate) (PMMA) was investigated. PR is a necklace-like supramolecule with rings threaded onto a linear backbone chain that is capped by bulky end groups. Cyclodextrin (CD) serves as the ring structure and it can be functionalized to induce specific interactions with the hosting polymer matrix and achieve improved mechanical properties. The CD structure in PR contains polycaprolactone (PCL) grafted chains, which are partially modified with a methacrylate functional group. The effect of PR on the scratch resistance of PMMA was investigated by varying the PR concentration. The findings suggest that the methacrylate functional group in PR enhances the compatibility with PMMA, leading to an increase in tensile strength and reduction in scratch coefficient of friction, which accounts for an improvement in scratch resistance by over 100%.
Joshua Krantz | Davide Masato | Ashley Caiado | Leonardo Piccolo | Marco Sorgato | Giovanni Lucchetta, May 2021
The generation of micro-structures on plastic part surfaces has been a topic of great interest due to the potential applications in a wide range of fields such as optical, medical, and electronics. These microstructures modify the wetting properties allowing the creation of superhydrophobic surfaces. Accurate surface replication is essential to achieve consistent and repeatable wetting properties. In this work, micro-structures were generated on steel inserts using a femtosecond laser and then replicated by injection molding on polypropylene and polylactic acid. Experiments were performed for each polymer to determine the effects of mold temperature, texture orientation, and measurement location on the replicated structures’ height and the contact angle. The experimental results show that the orientation of the drop and the mold temperature have significant effects on both the contact angle and height of the micro-structures.
Lars Kraus M.Sc. | Tobias Vossel, B.Sc. | Dr.-Ing. Martin Facklam | Prof. Dr.-Ing. Christian Hopmann, May 2021
In blown film extrusion, heat dissipation is usually achieved by convection, using double-lip cooling rings. To maximize the heat dissipation, a narrow cooling air flow at the film bubble is essential. However, the cooling air flow is influenced by the so-called “Coanda-effect”, which describes the adhesion of a flowing medium to a surface. If the cooling air adheres at the cooling ring lip, this can lead to a dead zone in the flow field, which reduces the convective heat extraction and thus the mass throughput. Up to now, this effect has been almost unexplored in blown film extrusion, so that the IKV is investigating this effect for the first time in real flow experiments. The aim is to find out, whether the effect depends on the process parameters and the die lip design, so that this knowledge can be used in the future to optimize cooling rings. First investigations show a great potential for an optimization: Only by adjusting the die lip geometry higher mass throughputs are possible at equal energy inputs.
Mou Paul | Barry Morris | Jeff Weinhold | Karlheinz Hausmann, May 2021
Multilayer films are widely used in flexible packaging to provide an optimum balance of performance and cost. Orientation in the semi-solid state via tenter frame, double bubble and machine direction orientation processes enhances barrier and mechanical properties and offers a means towards light weighting packaging structures. Interlayer adhesion of coextruded films, however, substantially decreases during orientation as generation of new interfacial area decreases bond density and chain segments are stressed. A heuristic model is proposed that provides insight into how changes during orientation in chain segment penetration, entanglement, orientation and density affects peel strength. Examples are provided that use these insights to design novel tie resins with improved performance.
Sean McDonald | Fabian Ullrich | Dr. Davide Masato | Alexander Krueger | Dr. Shailendra Pal Veer Singh | Dr. Alireza Amirkhizi, May 2021
Sapphire and polycarbonate are commonly used for transparent ballistic applications. This work focuses on the application of eyewear protection with the requirement of maintaining a thin profile. In this work, the properties of the two materials are combined in layered composites with two different material thickness configurations. The lamination process of the two materials is investigated to achieve appropriate adhesion and maintain acceptable light transmission. The ballistic properties of the laminates were observed with a qualitative analysis focusing on delamination upon impact.
Yong Zheng | Yiqing Jiao | Haewoong Park | Frank Chen | Byoungcheon Jo, May 2021
Ethylene acrylic acid copolymer (EAA) is widely used as tie-layer in multilayer film structures containing aluminum foil. EAA provides adhesion between foil and rest of the film structure. It can be used in pure or blending with low density polyethylene (LDPE) ordinarily in the range from 20 to 50%. However, this common practice of blending does not always work perfectly. From time to time, a clear film becomes hazed. The adhesion can deteriorate as well. This study focuses on examining the mechanism behind high haze and poor adhesion in LDPE and EAA blends and factors for optimization. The results from this study indicate that miscibility not viscosity mismatch is the dominant factor affecting the blending of EAA and LDPE. Low acid content EAA in general is more compatible with LDPE than high acid content EAA. Processing parameters, such as rotation per minute and temperature of an extruder, can also effectively change the properties of the blend.
Anshal Jilka | Leonardo Piccolo | Davide Masato, May 2021
In injection molding, the heat transfer coefficient (HTC) is a parameter defined as the polymer-mold interface's heat transferring ability. HTC depends on many factors, including polymer properties and processing conditions. Computer-Aided Engineering approaches use a constant preset value of HTC, which might lead to incorrect prediction of simulation results. In this work, a new approach is developed to validate and calibrate HTC using a numerical model. The model is based on Fourier's heat conduction law applied at the interface between the plastic part and the steel mold. Different HTC values on part temperature distribution, fill pressure, and fill time are studied. Moreover, the model is used to validate an injection mold design that could be used for experimental HTC measures using in-mold sensors. The results highlight the effect of HTC on the prediction of crucial injection molding parameters, suggesting the importance of experimental calibration.
Niclas Emrich | Stefan P. Meyer | Rüdiger Daub | Reinhard Schiffers, May 2021
Applications for automotive battery systems require hybrid joints of copper and polymer with high demands towards helium seal tightness and long-term durability. This work examines hybrid bonds, using indeterministic laser-nanostructures as pretreatment and variotherm injection molding as a joining method. Laser nanostructures are produced with two different laser setups; one having a mean power output of 20 W (state of the art) and one system with 200 W, promising faster processing rates by one order of magnitude. The spot distance and the number of laser pretreatment repetitions are varied systematically for both laser systems. All treatment variations are joined by variotherm injection molding using inductive heating of the metal specimen. A polyamide 12 compound with 10% glass fiber content is used. Bonds are tested for shear strength and helium seal tightness and the degradation of these properties due to ageing. For root cause analysis, the boundary layer is analyzed using ion beam cross-sectioning and SEM-imaging.
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Any article that is cited in another manuscript or other work is required to use the correct reference style. Below is an example of the reference style for SPE articles:
Brown, H. L. and Jones, D. H. 2016, May.
"Insert title of paper here in quotes,"
ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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