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SPE Akron Section March 2022 Newsletter
Read the March 2022 issue of SPE Akron Section newsletter.
Integration of Polycarbonate Thermoplastic in LED Lighting
Thermally conductive (TC) polycarbonate was utilized as aluminum metal replacement in LED lighting luminaires, along with transparent, diffusion, and reflective polycarbonate thermoplastics in order to describe a light weight, design-friendly, cost efficient part. To assess suitability of the TC polycarbonate, the part was subjected to thermal testing. Results showed very similar thermal characteristics as aluminum.
Designing for Six Sigma (DFSS) - A Systematic Approach to Robust Plastic Part Design
Designing for Six Sigma (DFSS) - A Systematic Approach to Robust Plastic Part Design To design and manufacture today's complex plastic components, product designers are under tremendous pressure to produce robust designs at a minimum cost and in the fastest possible time. Leading author David Wright wrote in his book titled “Failure of Plastics and Rubber Products” that design issues account for almost 20% of product failures. The fact is that many errors that manifest themselves as material, tooling or processing can also be attributed to design issues. Conventional plastic flow simulation does not necessarily help diagnose and avoid common design issues. Decisions made at the design stage impacts manufacturing quality, product cost, and delivery lead times. Taking a proactive approach by including Six Sigma philosophy upfront into the early design stage can help develop high quality, profitable products eventually bringing sustained value to customers and markets. The Paper will discuss the Design for Six Sigma (DFSS) philosophy and best practices and tools for its incorporation into new plastic product development. This will include: • Understanding the DFSS concept and popular methodologies such as DMAIC and DMADV • Learning how to use DFSS Methodology in early part of plastic product design lifecycle • Applying DFSS techniques and available simulation and DFM tools for successful implementation
Analysis of the State of the Art of Technical Drawings of Plastic Molded Parts Regarding Tolerances
The plastic-specific material properties are often not taken into account in the specification of technical drawings of injection molded parts. As a result, tolerance requirements are specified, that are too tight and sometimes even impossible to manufacture, which result in high production expenses. To avoid this, it is necessary to coordinate the functionally required accuracies of plastic components with the technical possibilities available for injection molding production.
In this paper a systematic analysis of drawings from practice is used, to show the current state of the art regarding geometric product specification and tolerance assignment of plastic molded parts. In addition to the quantification of the number of specified features, the unambiguousness of the product specification is assessed. Beyond that, the degree of accuracy of the tolerance requirements is quantified and the manufacturing feasibility is checked in accordance with ISO 20457 in order to then determine the resulting production expense that is necessary to achieve the required tolerances. It is proven that for almost a fifth of the plastic parts tolerance requirements are specified that are not feasible to be produced in the injection molding process. Additionally, it is found that all drawings examined do contain ambiguously specified features, that do not allow for an unambiguous verification.
Three Trends in Healthcare Adhesives
With an aging global population growing, the demand for new healthcare products and telehealth systems will increase. The FDA aims to advance innovation and development in digital health while ensuring patient safety and effectiveness. Adhesives are critical in the new remote monitoring products, such as the small wearable devices that stick to skin. In addition, surgical adhesives are replacing stitches, and robotic surgical systems are rising. With healthcare adhesives, there are additional challenges in safety, performance, biocompatibility ISO 10993, and cost requirements. This paper reviews three healthcare adhesive trends: (1) topical skin adhesive patches, (2) tissue adhesives, and (3) medical device assembly and equipment adhesives.
Adhesion of Overmolded TPE to FR-PC/ABS: Effect of TPE Properties and Substrate Color Recipe
Various grades of Thermoplastic Elastomer (TPE) were overmolded onto a FR-PC/ABS blend prepared with several different color recipes and tested for adhesion. All combinations prepared exhibited adhesive failure with a standardized peel test, yet showed relatively high average peak peel forces that ranged from 3.74-4.07 N/mm, which agreed well with literature values. Different color recipes for the substrate had no discernable effect on peel forces. Two-step overmolding of TPE using pre-molded (and therefore conditioned) substrates gave no significant difference to those prepared with direct 2-shot overmolding.
The Most Frequent Design Flaw That Leads to Part Failure
The topic presented in this paper is not new. There are numerous reasons why sharp transitions should not be present in a plastic part. However, the number of failures that are occurring at sharp transitions is still very common. In most cases, they can easily be avoided by simply removing metal from the mold to make a smooth transition. This paper will review where most of these transitions are being found, and why they are common in critical parts. A tensile testing study was performed to better understand the effect of geometric transitions. Two cases studies are given showing why the sharp corners can significantly reduce the lifetime of a plastic part.
Effect of Molding Parameters on Orientation and Tensile Properties of Polycarbonate
The tensile properties of two different molecular weight polycarbonates were examined in relation to injection-molding conditions, such as low and high temperatures & speeds (affecting injection pressures), that were beyond those recommended by the supplier. We found conditions that prompted higher injection pressures led to decreases in tensile elongation-at-break, with more significant decreases for higher molecular weight (and high viscosity) PC. Examination of molded samples under polarized light suggested higher degrees of molded-in stress along the flow length as an important contributor to the changes in elongation at break. Additionally, corresponding to the elongation at break, the onset of strain hardening decreased under injection molding conditions that produced higher injection pressures.
Effect of Rubber Surface Treatment on the Properties of Rotomolded Thermoplastic Elastomers
Thermoplastic elastomers (TPE) are a combination of a rubber and a thermoplastic to create a recyclable blend combining the properties of both resins. The objective of this work is to produce and characterize rotomolded parts based on polyamide 6 (PA6) as the matrix and recycled ground tire rubber (GTR) as the dispersed phase. In order to improve the adhesion between PA6 and GTR, and consequently the mechanical properties of the resulting TPE, a treatment with formic acid was used on the GTR surface. All the samples were initially mixed via dry-blending using 5 and 10% wt. of GTR and then rotomolded. For these concentrations, successful rotomolded parts were produced to report on their morphological and mechanical properties. The results show that increasing the GTR content led to lower tensile modulus and tensile strength, but higher elongation at break and impact strength compared to the neat matrix.
Polypropylene/Ground Tire Rubber (PP/GTR) Composites Produced Via Rotational Molding
In this work, polypropylene (PP) was dry-blended with ground tire rubber (GTR) to produce composites by rotational molding. In particular, the effect of GTR content was investigated to modify the mechanical properties of the PP matrix. Each compound was characterized via morphology, density and mechanical properties (tensile, flexural and impact). As expected, the results showed that all the mechanical properties decreased with increasing GTR concentration due to its low modulus and strength. Also, the crosslinked structure of the GTR particles is believed to limit the interfacial PP-GTR interaction, thus also limiting mechanical stress transfer.
Self-reinforced Polylactide Composites Manufactured by Melt Spunbond Technology
A series of stereocomplex polylactide (SC-PLA) blends (PLLA 95 wt%/PDLA 5 wt%) were prepared by spunbond technology. For this, the compounds of linear PLLA, and low and high molecular weight as well as branched PDLAs were spun at two different temperatures. They were spun at 190 °C, which was below the melting temperature of the stereocomplex crystals. And, they were melt-spun at 230 °C, which was above the melting temperature of the stereocomplex crystals. Morphological observation of the etched samples showed that the samples spun at 190 °C demonstrated tiny spherical crystals exhibiting diameters in the range of 100–200 nm; however, the samples spun at 230 °C showed thin fibers in the size range of 60–70 nm. The obtained results were supported by shear and elongational rheological measurements. Moreover, crystallization kinetics of the samples was also enhanced after spinning and was largely dependent on the spinning temperature. Tensile modulus and strength of the spun samples was also significantly improved. The spun samples also presented a considerable decrease in boiling water and hot air shrinkage.
Introduction to Possible Hybrid Veneer Composite Laminated Panels
In the current research, hybrid laminates having veneer facesheets and natural fibre composite cores were fabricated to investigate their fire and mechanical properties and to observe a suitable combination. Wool and flax fibres were selected for fibre reinforcement. Ammonium polyphosphate (APP) was used as the primary flame retardant for all the composites. The mechanical performance of the flax fibre reinforced fire retardant polypropylene (flax-FRPP) and fire retardant wool-polypropylene (FR-wool-PP) hybrid layered panels were further studied and compared to plywood made similarly. The results showed that hybrid laminates have better fire properties and the hybrid layered veneer composites can have significant structural applications if proper bonding between the composite and the veneer layers can be achieved. The tensile properties showed a reduction in Young’s modulus and ultimate tensile strength, though the wool-veneer hybrid laminates outperformed the flax-veneer ones. Moreover, the impact test showed that the wool-veneer hybrid laminates had the best resistance when compared to all the veneer-based samples tested. The results point towards the possibility of manufacturing a superior fire-resistant hybrid veneer composite laminate.
Compostable Adhesive Formulations for Extrusion Lamination
In this work, two compostable adhesive formulations, i.e., Resin A – MPP (Major PLA phase) and Resin B – MINPP (Minor PLA phase), were developed and evaluated for their performance as an adhesive in the extrusion lamination process. The densities of both the resins were in the range of 1.26-1.32 g/cc. The MFI values of Resin A and Resin B were 5 and 3 (g/10 min at 190ºC/ 2.16 kg), respectively. The complex viscosity of Resin A was lower than the complex viscosity of Resin B. The percent neck-in of Resin A at 235ºC was almost 4 times as that of Resin B at same conditions. The percent neck-in increased with increasing the temperature and distance from the die. Multilayer laminates were made using cellophane and metalized cavitated PLA as substrates, and Resin A or Resin B as adhesive. The adhesive strength of the Resin B to the cellophane was 20 g/cm, which was 10 times higher than the adhesive strength of Resin A (2 g/cm) to the cellophane. Also, the adhesive strength over the period of two weeks did not decrease significantly.
A Co-Monomer Resin Matrix Design for Processing of Polymer Concrete Composites
The present study aims to design a comonomer based resin matrix with a prolonged gel time while maintaining low viscosity and minimal curing time to ensure its processability with high filler contents in fabricating polymer concrete composites (PCC) for bases of tool machines. In this work, a copolymerization route was adopted to optimize the processability of a commercially available epoxy vinyl ester. Comonomer resin systems were prepared from addition of Methyl methacrylate (MMA) as a reactive diluent into the commercial epoxy vinyl ester resin (VE) which was premixed with styrene (ST) diluent (48 wt. %). Compositions of comonomer resin systems were varied systematically to achieve an optimum mixture design. The viscosity and gel time of comonomer resin systems were measured by a digital Brookfield viscometer. The influence of MMA on the curing behavior, elastic modulus and glass transition temperatures of comonomer resin systems have been investigated by differential scanning calorimeter (DSC) and dynamic mechanical analyses (DMA) respectively. The obtained optimum comonomer resin system was 40wt% VE resin, 23wt% MMA and 37wt% ST. This formulation exhibited 80% lower viscosity and about 45% longer gel time as compared to the viscosity and gel time of commercial VE resin system with just half the styrene monomer content, thereby not only ensuring its processing with high filler contents, but also reducing the volatile organic compounds associated with the large-scale manufacturing of PCC products. Also, this composition showed the shortest curing time and 60% higher flexural strength (53.6 MPa) compared to that of the commercial VE resin system (17.3MPa).
Enhanced Dispersion of Lignin in Pet Polyols for Improved Thermal Insulation of Polyurethane Foams
The incorporation of technical lignin, a multifunctional natural polymer, into rigid polyurethane foam (RPUF) for the enhancement of thermal insulation performance has gained increasing interest in academia and industry. However, the structural complexity of technical lignin hinders its dispersion in the polyols commonly used for the preparation of RPUF. Poor dispersion of technical lignin in polyols inhibits the chemical reactions and limits the potential improvement in the thermal and mechanical properties of RPUF. Herein we report enhanced dispersion of unmodified kraft lignin, at a loading of 3 wt % in a mixture of glycerol and an aromatic polyester polyol (20:80) for the preparation of RPUF. It has improved the insulation property by 30% while retaining its mechanical performance compared to the control RPUF without lignin. Such a level of improvement, to the best of our knowledge, has not been reported in RPUF using chemically unmodified lignin to date. This is attributed to the enhanced dispersion of the kraft lignin in the polyol blend causing changes in the cell morphology of the resultant RPUF, as supported by microscopic and rheological analysis. To this end, the insights into the influence of kraft lignin on the polyol-precursor on the properties of the RPUF are discussed.
Prediction of Enzymatic Degradation of Poly-g-Caprolactone with Esterase Using a Reaction Model
An enzymatic degradation mechanism of Poly- ε-Caprolactone (PCL) is discussed in this paper. A ping-pong bi-bi reaction mechanism with esterase is chosen to obtain the model equations. The reaction rate constants were either estimated or fitted in the model. The model is then utilized to predict concentration vs time plots for PCL and a degradation product, hydroxycaproic acid. The reaction between the enzyme and polymer is found to be rate limiting because of the limited polymer surface available for reaction. The predictions of the model are compared to experimental results reported in literature.
Controlled Release of Essential Oils Using Laminar Nanoclay and Halloysite / Essential Oil Composite
The preparation and characterization of a multilayer film reservoir with clay/essential oil (EO) composites was described. The goal is to analyze the potential use of these reservoirs with clay/EOs composites as aroma-controlled release for various applications such as pesticide or attractant for pest control as well as antimicrobial control. Two types of clays were analyzed, porous halloysite (HNT) and octadecyl modified montmorillonite (MMT) nanoclay; as well as two types of essential oils, orange (OO) and thyme oil (TO). The DRX results confirmed that MMT clay presented higher thyme oil adsorption and better interactions than orange oil. Clay/EO composites encapsulated in multilayer film showed a prolongated aroma release during longer times. Polyamide (PA) barrier layer thickness has an effect on the liberation of the volatile compounds through the multilayer film.
Preparation and Characterization of Polylactic Acid-Sawdust Deep Eutectic Solvent Extracted Lignin
There is an ever increasing need for sustainable and biobased materials. Plant-based feedstock such as cellulose and lignin can potentially become competitive resources as alternatives to fossil-based materials. Lignin as an inexpensive feedstock has been examined toward preparing polymer composites. It however faces some challenges including its detrimental impact on the mechanical and thermal properties of the resultant composites. This work reports the fabrication and characterization of polylactic acid/lignin composites with the incorporation of a new type of lignin, called deep eutectic solvent (DES) extracted lignin. White fir sawdust was used as feedstock to extract DES lignin. For comparison, commercial alkali lignin (CAL) was also used as a benchmark. PLA/lignin composites containing 0-15 wt.% lignin were fabricated using twin screw extrusion process followed by compression molding. Composites characterization were conducted using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and tensile testing. The results revealed that the mechanical and thermal behaviors of DES lignin composites significantly outperformed their CAL counterparts. For composites with 15 wt.% DES, the tensile strength, Young’s modulus, and elongation at break dropped by ~33, 7 and 45%, respectively, compared to those of neat PLA. However, the composites with 15 wt.% CAL showed 90, 45 and 86% drop in the strength, modulus, and elongation, respectively. The initial thermal degradation temperature of PLA dropped by ~ 8-27 °C with the incorporation of 5-15 wt.% DES lignin. On the other hand, the introduction of CAL to PLA lowered the degradation temperature by ~89-124 °C. DSC also showed a drop in the glass transition temperature (Tg) and melt temperature (Tm) for both the composites but the drop was less significant for DES lignin composites. The good performance of PLA/DES lignin composites may be associated with the DES lignin’s high purity, low heterogeneity, low molecular weight, fine particle size as well as its homogenous dispersion and compatibility with PLA matrix.
Variability Levers in ASTM D-2863 Results for Styrenic Foams
ASTM D-2863 is a small-scale fire performance classification test, part of ASTM C-578 standard for polystyrene rigid thermal insulations, with a binary pass/fail outcome at a given oxygen concentration level. When applied to foams, the test is highly variable and is easy to manipulate, putting its accuracy as a test method into question. In this work, macro-imaging was used to closely monitor the foam – flame interaction to gain a better understanding of variability levers. For example, one of the levers is duration of flame application to a sample. Our imaging studies indicate that the pass / fail boundary oxygen level is strongly correlated with the flame application duration.
In-Line Laminate Decorative Thermoplastic Composite Panel
In this paper, a decorative material was first applied onto the light weight reinforced thermoplastic (LWRT) composite core mat during the core manufacturing, and then followed by a consolidation process through the calender rolls. This method is defined as an in-line lamination process with a finished A-surface panel in comparison with conventional off-line decorative materials lamination process, in which the decorative layer is applied in a separate process from core manufacture. Decorative layers with two patterns, namely woodgrain and marble, have been studied. The adhesion performance between the decorative skin material and LWRT composite substrate has been evaluated by 180° peel adhesion test following ASTM standard D903. The separation between the decorative layer and the substrate was difficult to initiate, which demonstrates an outstanding adhesion between the two components. A stylus method quantitatively confirmed the decorative surface is smooth and able to cover the core’s texture. Flatwise tensile test results by ASTM standard C297 method showed the decorative panels could not be delaminated, indicating strong bonding between decorative skin material and core mat. Materials produced with the woodgrain pattern were tested to have better flexural strength and stiffness than the sample made with marble decorative pattern material. In addition, flame retardancy results showed the laminated decorative panels can meet ASTM E84 requirement of Class C and above. The decorative material with custom design provides the decorative A-surface with an appearance of wood, stone, textile or other natural materials as desired, opening a window for the LWRT composite to be used inside an RV such as the interior layer of sidewall and ceiling.
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