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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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.
Effective Antimicrobial Protection for Automotive Composite Applications
by F. Deans & Dr. H. Khan
A growing concern that OEM’s, suppliers, and dealers have is how to protect their customers from exposure and transmission of harmful pathogens. The market has been flooded with a number of products for direct human use. However, there remains unanswered data and details on how to effectively utilize antimicrobial agents for automotive components that could come into contact by human occupants. Specific information on types of antimicrobial performance, manufacturing techniques on protecting plastic and composite applications, and prolonging the antimicrobial effectiveness will be discussed.
The cooling phase in injection molding has a very high influence on the resulting part warpage and is crucial for the resulting quality of the parts. Therefore, an automatic and reproducible design of cooling channels can contribute to produce highly precise parts.
In this paper, cooling channels are generated based on the results of an inverse thermal optimization of an injection mold. This optimization calculates the optimal heat flux inside the surrounding injection mold such that the part is cooled as homogeneously as possible. Iso-surfaces, which indicate locations, where the calculated heat flux would be equal to a cooling channel with a certain temperature, can be derived and are used as a basis for the presented path-planning problem
Based on the iso-surfaces, cooling channel segments are generated close to those surfaces based on a geometric minimization problem. In a next step, these segments need to be connected in an optimal way concerning fluid flow and path length. Path planning algorithms usually determine a path between a single start and end point, whereas in this case multiple combinations have to be evaluated. Thus, an algorithm is presented which determines a reasonable sequence of the channel segments to be connected and ensures that the found finished cooling channel is collision-free - both to obstacles such as the cavity or parting plane of the injection mold and to itself.
Validation simulations show that the results are comparable in time and performance to a manual design, but need less effort by the user.
Environmental consciousness is driving modern research and development in the automotive sector to target the advancement of feasible green materials in automotive applications. Basalt fiber has shown to be a robust competitor against glass and carbon fiber and is more eco-friendly manufacturing processes. Reinforcing polypropylene with basalt fiber and hemp hurd using maleic anhydride-grafted polypropylene (MAPP) as a coupling agent, has shown to contain similar mechanical properties to its competitors. A mixture model was implemented to optimize the mechanical properties of a variation of fiber ratios and MAPP to compare against a controlled GF mixture. Scanning Electron Microscope (SEM) analysis of fracture surfaces show the variation in fiber–matrix adhesion based on addition of MAPP. This study concludes that the addition of MAPP improves the mechanical behaviors of hybrid composites made from basalt fiber and hemp hurd reinforced polypropylene.
Amy Langhorst | Sabrina Peczonczyk | Hannah Sun | Alper Kiziltas | Debbie Mielewski, May 2021
Automotive manufacturers have been increasing use of natural fiber composites to reduce vehicle weight and respond to consumer demand for environmentally friendly products. However, the low thermal stability of natural fibers can limit their use to low-processing-temperature polymers and low-temperature automotive environments. Pyrolysis of biomass results in the formation of a porous substance called biocarbon, which can improve composite thermal performance, eliminate odor, and reduce hydrophilicity. The objective of this study was to investigate the effects of biocarbon on the performance of biocarbon-glass fiber hybrid composites for use in under-the-hood automotive applications. This study evaluated the macroscopic (mechanical performance, density) and microscopic (SEM) characteristics of biocarbon-hybrid composites with varying loading level and biocarbon type. Biocarbon-hybrid composites were approximately 10-13% lighter than currently used fan-and-shroud materials and the addition of biocarbon content improved composite flexural strength & modulus.
Piccolo Leonardo | Giovanni Lucchetta | Marco Sorgato | Davide Masato, May 2021
The replication accuracy of submicron surface structures by micro injection molding control the replicated part functionalities, such as tissue engineering. In this work, we propose a multi-scale model for the replication quality of laser-induced periodic surface structures by micro injection molding of different bio-based polymers. The model decouples the macro cavity flow, investigated through a numerical simulation, from the micron-scale flow, that is modeled with a novel analytical approach. The macro model determines the boundary conditions for the filling of the sub-micron surface structures. An in-depth characterization of the mold topography of the polymer thermal, rheological, and wetting properties was carried out to feed the model. Injection molding tests were performed, varying the mold temperature to manufacture sub-micro textured parts for the model validation. The sensitivity of the replication accuracy to mold temperature and polymer selection was captured. The multi-scale model showed a maximum deviation of 8% from the experimental results.
The recyclability of natural fiber and glass fiber reinforced polypropylene composites and glass fiber reinforced nylon composites have been studied through injection molding and mechanical grinding. Mechanical properties of virgin and recycled composites were assessed through flexural, tensile, and impact tests. No significant degradation in the mechanical properties of natural fiber composites was observed after subjecting the composites through several rounds of recycling and water absorption at ambient temperature in tap water. However, severe degradation in the mechanical properties was observed for glass fiber composites. For instance, after five cycles of recycling, only 59% of flexural strength and 64% of flexural modulus was retained for glass fiber reinforced nylon composite. This is mainly due to severe attrition in glass fibers caused by recycling as evidenced by studies on fiber length distribution. Water absorption tests conducted at room temperature and subsequent environmental conditionings such as freeze-thaw cycling and extended freeze cycling only affected nylon composites. At saturation point, water absorption for nylon composites was 7.7% by wt. after 45 days of immersion, which significantly affected the mechanical properties. The tensile strength of the nylon composites reduced from 88.4 MPa to 36.2 MPa, and modulus reduced from 5.6 GPa to 1.8 GPa after saturation.
Tianhong (Terri) Chen | Louis Waguespack | Gregory W Kamykowski, May 2021
This paper describes the use of differential scanning calorimetry (DSC), modulated DSC, and dynamic mechanical analysis to characterize different regions of thermoformed beverage cups made from polylactic acid. These techniques demonstrated the differences in crystallinity and mechanical strength of the cup based on the location of the specimen. These techniques can guide the processor in resin selection and processing conditions.
Nabeel Ahmed Syed | Utkarsh | Mohammed Tariq | Amir H. Behravesh | Ghaus Rizvi | Remon Pop-Iliev, May 2021
The emergence of new composite materials as replacements for metals has been demonstrated in many studies. Many products derived from steel-reinforced composite materials can potentially be modified by replacing the existing steel cord reinforcement with that of synthetic fibers such as carbon to overcome the problems involving dimension instability and the effect of creep which could pose problems in applications such as belts driving heavy machinery. In the present study, Carbon fiber reinforced in the TPU matrix was manufactured by compression molding and was tested for dynamic mechanical and tensile analysis. The results obtained with carbon/TPU are positive with respect to steel/TPU composites which proves that the carbon fibers can be a suitable replacement to the steel cords that are used in applications such as conveyor belts for providing the required tensile strength and creep resistance.
Masoud Allahkarami | Michael Rector | Sudheer Bandla | Jay C. Hanan, May 2021
Understanding heat shrink film properties and behavior will help optimize shrink wrap formation in packaging applications. Two experiments were conducted to better understand shrink properties of PE film. The first experiment was to collect data on film shrink ratios. The second experiment was an attempt to compare film preshrunk and post-shrunk mechanical properties. For this, a fixture was developed to quantify film shrink under isothermal heating. The film submersion tool successfully yielded films that were shrunk at different temperatures and demonstrated a method applicable for analyzing properties of heat shrink film at various stages of the shrinking process. Further work is focused at developing correlations between preshrunk properties to post-shrunk properties.
Aya A. Saleh | Garrett W. Melenka | Siu Ning Leung, May 2021
The development of Poly(vinylideneflouride) (PVDF) material with high electroactive properties is of great interest for its use in energy harvesting. This study is concerned with producing PVDF filaments to be fed into a Fused Filament Fabrication (FFF) 3D printer to broaden the horizon for printing complex energy harvesters. An extrusion process followed by post treatments was applied and the processing conditions were varied as they play a crucial role in altering the phases within PVDF and its crystallinity. The correlation between the parameters and the resultant properties of the PVDF filament was made using combination of Fourier-transform infrared spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) characterization techniques. The optimized processing conditions were found to be 230 ᴼC for extrusion temperature and 4.5 – 6.5 stretching ratio. This led to the fabrication of an electroactive PVDF filament with 80% β-phase content and 50 to 55% degree of crystallinity.
Praveenkumar Boopalachandran | Yongfu Li | Steve Rozeveld | Barry Morris | Leslie O’Leary | Josh Enokida, May 2021
Ethylene-methacrylic acid (EMAA) copolymers are converted to ionomers (ionic functionality) through the partial neutralization of their carboxylic acid groups. These ionic groups are randomly distributed along the polymer backbone, and various cations (i.e., Na, Zn, Mg, Li, etc.) can be incorporated into the ionic functionality to modify their properties. Some unique properties that these ionomers exhibit include high melt strength, excellent toughness and optical clarity. These desired properties make the ionomers ideal for applications that include packaging, decorative perfume and spirit caps and capstock decking.
This study was focused on the use of Fourier-Transform Infrared (FTIR) spectroscopy to study EMAA copolymers partially neutralized with Zn cations. FTIR was also used to measure the degree of neutralization of ionomers. The % neutralization method was developed internally, and it was applied to extract the experimental neutralization values with comparison to theoretical values for EMAA–Zn ionomers. The values were in good agreement with the expected neutralization levels. Chemical mapping of the acid band (C=O stretch) and carboxylate band (COO- stretch) in EMAA–Zn ionomer indicated that their distribution on a micro-scale in the selected cross-section were homogeneous. The FTIR method was also used to study EMAA copolymers neutralized by mixed metal Zn and Na cations and compare with EMAA ionomers neutralized by single metal cation. For the mixtures, a new carboxylate band appeared around 1569 cm-1, which was assigned to the COO- stretch. Based on the unique peak position, it suggests that there are interactions between the zinc and sodium cations.
This work is focused on investigating the influence of processing parameters on the fiber breakage in the plasticizing unit of an injection molding machine. To determine the fiber length reduction, an injection molding machine is equipped with a special cylinder which can be opened over a length of 700 millimeters. This makes it possible to measure the fiber length along the screw channel and to analyze the influence of the melting behavior. Fiber length degradation is investigated for short fiber reinforced polypropylene with different fiber fractions under the variation of the processing parameters screw speed, barrel temperature and back pressure. The results show a negative influence on the fiber length for an increase in screw speed and back pressure as well as for a reduction of the barrel temperature.
Cheng-Hong Lai | Chao-Tsai (CT) Huang | Jia-Hao Chu | Wei-Wen Fu | Sheng-Jye Hwang | Hsin-Shu Peng | Chih-Che Wu | Chun-I Tu, May 2021
The fiber-reinforced plastics (FRP) material has been applied into industry as one of the major lightweight technologies, especially for automotive or aerospace products. The reason why fibers can enhance plastics is because of their microstructures. One of those microstructures is fiber orientation distribution. Since the fiber orientations inside plastic matrix are very complex, they are not easy to be visualized and managed. In addition, there might be some interaction between flow and fiber during the injection molding processing, but not fully understood yet. In this study, the flow-fiber coupling effect on FRP injection parts has been investigated using a geometry system with three ASTM D638 specimens. The study methods include both numerical simulation and experimental observation. Results showed that in the presence of flow-fiber coupling the melt flow front advancement presents some variation, specifically at the geometrical corners of the system. Furthermore, through the fiber orientation distribution (FOD) study, the flow-fiber coupling effect is not significantly at the near gate region (NRG). It might result from too strong shear force to hold down the appearance of the flow-fiber interaction. However, at the end of filling region (EFR), the flow-fiber coupling effect tries to diminish the flow direction orientation tensor component A11 and enhance the cross-flow orientation tensor component A22 simultaneously. It ends up with the cross-flow direction dominant at the EFR. This orientation distribution behavior variation has been verified using micro-computerized tomography (micro-CT) scan and images analysis by AVIZO software. Finally, the flow-fiber coupling effect also verified based on the tensile stress testing and the shrinkage of the injected parts through different flow domains.
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