SPE Library
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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Conference Proceedings
Spreading Coefficient: A Simple Tool for Predicting Failure in Adhesives
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.
Optimizing Film Bending Stiffness and Coefficient of Friction for High Speed Converting
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.
The Use of Diblock Carbon Nanotubes to Increase Fracture Toughness at Immiscble Blend Interfaces
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.
Scratch Behavior of Polyrotaxane-Modified Poly(methylmethacrylate)
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%.
Wetting Characteristics of Microstructures on Injection Molded Parts
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.
Optimization of Double-Lip Cooling Rings in Blown Film Extrusion Considering the Coanda-Effect
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.
Adhesive Resin Technology for Oriented Multilayer Films
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.
Transparent Layered Composite for Protective Eyewear Applications
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.
Optimization of Ethylene Acrylic Acid and Low Density Polyethylene Blend in Tie-Layer
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.
Numerical investigation on the Effect of Heat Transfer Coefficient in Injection Molding
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.
Evaluation of Polyamide Copper Hybrids for Automotive Battery Systems
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
Abstract Submission
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.
Path-Planning Algorithm for the Automatic Generation of a Cooling Channel Layout in Injection Moulds
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.
Optimizing Mechanical Behavior of Basalt-Natural Fiber Hybrid Injection Molded Composites
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.
Biocarbon Hybrid Composites for High-Temperature Automotive Applications
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.
Multi-Scale Modeling of the Replication of Submicron-Structures by Micro Injection Molding
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.
Water Absorption Behavior of Recycled PP and PA6 Composites with Fiber Reinforcement
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.
Thermal and Mechanical Techniques for Troubleshooting Polylactic Acid Processing Issues
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.
The Study on Replacement of Steel Cord Reinforcements by Synthetic Fibers in Composite Materials
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.
Method to Evaluate Shrink Film Material Properties
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.
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