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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Fatigue Resistance of Structural Adhesives
Matt Miner, May 2020
Adhesive selection in high dynamic load environments relies heavily on mechanical adhesive properties, including shear, peel and compressive strength. Over time and in the life a part, fatigue can occur to metals, plastics and adhesives. Fatigue weakens the overall strength of these components and can lead to premature failure. In the case of adhesives, shear strength values may depreciate an order of magnitude, from thousands to hundreds of psi due to a life of wear and dynamic movement, which can lead to failure. When selecting an adhesive for bonding a joint, the likely first choice is the adhesive with the highest shear strength with the assumption that the higher the shear strength the longer the part will last. However, upon testing, higher shear strength does not directly correlate to a longer part life. In the case of hybrid adhesives (Loctite® HY4090GY™ and HY4070™) compared to epoxies (Loctite® E-20HP™), the epoxy greatly outperformed the hybrids in shear strength, but the hybrids greatly outperformed the epoxy in limit of endurance. Overall, the methyl methacrylate (MMA) adhesive (Loctite® H8003™) proved to be the most fatigue resistant adhesive tested.
Fibrillated and Highly Interconnected Porous PCL Scaffolds by Supercritical Foaming and Leaching
Jing Jiang, May 2020
Highly porous and interconnected 3D structures are crucial elements for tissue engineering scaffolds since they can support the mass transport of cell nutrients and waste. Supercritical foaming technology is an environmentally-friendly and solvent-free way of manufacturing porous scaffolds. In this research, highly porous, interconnected poly(ɛ-caprolactone) (PCL) scaffolds combined with supercritical carbon dioxide (SCCO2) foaming and a polymer leaching process were fabricated by blending PCL with water-soluble poly (ethylene oxide) (PEO) as a sacrificial material. The effects of phase morphology of PCL/PEO blend on foaming behavior and pore morphology were investigated. The incorporation of PEO not only facilitated the foaming of PCL by increasing its viscosity, but also improved the porosity and interconnectivity of the post-leached PCL scaffolds. The fibrillated porous scaffolds with open-pore content up to 91% were obtained after the leaching process because of two different cell-opening mechanisms. Cell-opening on surface of scaffolds is difficult in preparing porous materials. In the end, a novel method for improving surface porosity and producing the so-called outer and inner porous PCL scaffolds is described. The information gathered in this study may provide a theoretical basis for research into porous tissue engineering scaffolds.
Flow Simulation of A Microcapillary Cast Film Die
Kurt Koppi, May 2020
A relatively wide (610 mm) lab-scale microcapillary cast film die was fabricated to aid in the development of this unique film processing technology. Due to the approach used to create microcapillary channels, standard die design techniques for maintaining uniform film gauge (e.g. die lip adjusters) are not applicable. A series of modifications were made to the original die design to improve film gauge. One such modification was the use of computational fluid mechanics (CFD) to improve flow uniformity across the die. Due to the multitude of air pins located near the die outlet, it is impractical to perform direct CFD simulations based on the actual flow geometry. Instead, the flow geometry associated with the comb-like structure of the air pin region is replaced by a porous medium with an equivalent viscous resistance. The primary focus of this paper is a description of the porous medium CFD technique used in the design of the 610 mm wide die.
Foam Sheet Extrusion with Blowing Agent Mixtures and Correlation Analysis With Dimensionless Numbers
Robert Breuer, May 2020
In foam extrusion, the blowing agent has a significant influence on the process parameters and the resulting foam properties. Low-density polystyrene foam sheets are usually produced with aliphatic hydrocarbons or alkanes as physical blowing agent. Due to the necessary safety precautions and the environmental impact, there is great interest in using alternative blowing agents such as carbon dioxide (CO2). The sole use of CO2 often leads to corrugation, open cells or surface defects on the foam sheet and therefore requires modifications to the process technology. The aim of this work is to investigate the effect of blowing agent mixtures of CO2 and organic solvents on the production of foam sheets. In particular, the interactions between the blowing agent formulation, the process parameters and the foam sheet properties are analyzed. The knowledge of the interactions can allow a systematic influencing of the foaming behavior without modifying the polymer itself. For a systematic evaluation, an existing process model for describing the melt flow in the extrusion die is extended and applied to an annular gap die. Based on the model, dimensionless numbers can be calculated to describe the foaming behavior. The characteristic numbers enable the direct comparison of different recipes, process settings and die geometries.
Foaming of PVC Using Ultra High Molecular Weight Acrylic Processing Aids
Manoj Nerkar, May 2020
Polyvinyl Chloride (PVC) foaming was studied as a function of high molecular weight acrylic processing aids. It was demonstrated that an ultra-high molecular weight processing aid is 25-30% more efficient than relatively lower, but still high, molecular weight acrylic processing aids. The higher Mw processing aid provided similar foaming performance at lower loading levels. Foaming reduced the density of PVC compounds to 0.32-0.34 g/cc. More than 1000% expansion was achieved in the melt extrusion process using a chemical blowing agent. Fusion characteristics were also studied. Fusion times for initial fusion peaks were in the range of 42-44 seconds while the fusion times of the second fusion peaks were in the range of 74-94 seconds. The higher molecular weight processing aid maintained fusion characteristics of PVC compounds, warranting no significant changes in extrusion process.
Functional Alkane Solvent Systems
Ying-Hua Fu, May 2020
An oligomeric hydrocarbon, Poly(α-olefins) (PAOs), were previously reported as a potential greener solvent to replace conventional alkanes solvent due to its lower toxicity, flammability and volatility. However, its poor solubility toward most organic substrate may limit its applications as solvent. This work demonstrated three strategies to introduce polarity in PAOs and recycle polar additives simultaneously: polymerization of polar monomers onto a PAO anchor, host-and-guest interaction and end-group modification of a PAO anchor, vinyl-terminated polyisobutylene (PIB). In the first method, RAFT polymerization gave a better control of polar polymers onto PIB in order to maintain hydrocarbon solubility over other two polymerizations (hydroboration/O2 initiation, ATRP polymerization). Secondly, the polar polymer, poly(isopropylacrylamide) (PNIPAM) could be successfully brought into and recover back out an alkane phase by treating with chemicals via a hydrogen bond network. The reversible solubilization of PNIPAM were used in recyclable Rhodium catalyzed hydrogenation. Lastly, a hydrophilic moiety (Hexamethylphosphoramide, HMPA) was successfully incorporated onto PIB. The hydrocarbon soluble Lewis base catalyst can be used in allylation of benzaldehyde in PAOs. Other ongoing studies are exploring this molecular recognition based solubilization with other solubilizing agents, other precipitation agents and exploring the use of this chemically responsive solubility both as a tool to prepare new solvent systems and new sorts of recyclable catalysts.
Glass Reinforced PA 66 Compound with Improved Flowability for Thin Wall Applications
Mo Meysami, May 2020
Glass reinforced polyamide compounds are widely used in various applications. Many of these applications require a material with high flowability to allow the molders to properly manufacture parts with thin walls and complex geometries. In this study, a flow enhancing additive is used to improve the flowability of a glass reinforced polyamide 66 compound. Flow characteristics of the new formulation were studied using various characterization methods. Test results showed that physical and mechanical properties were maintained very well while flowability of the modified formulation was enhanced significantly compared to the control material.
Hot Runner Molding of Bioplastics and Recyclates
Davide Masato, May 2020
The interest for molding of bioplastics and recyclates is continuously increasing, not only with increased awareness of sustainability issues but also in response to regulatory mandates to reduce environmental impact. Bioplastics and biopolymers have been successfully derived from renewable resources, however their commercial adoption remains hindered by the lack of processing experience. Degradation issues are a potential concern for manufacturers, especially for hot runner injection molding. In this work, the performance and thermal stability of three commercial biopolymers and a recycled resin were characterized and compared to a reference synthetic polypropylene. The results indicate that bioplastics can be readily processed by hot runner injection molding by following design and processing rules similar to those conventionally implemented for synthetic resins. Minor degradation and quality issues are solved by routine optimization of processing parameters.
How Poor Selection of Materials, Design, Tooling and Design Errors Affect the Aesthetics of Plastic Parts and What Designers Need to Know About the Science of Color and Appearance - Part 1
Vikram Bhargava, May 2020
Most engineers and designers come from the metal world. Therefore, many of them make assumptions on the predicted performance of plastic properties based on their metals background. Unlike metals, the knowledge of color and appearance is extremely important in the case of plastics. Most plastic parts have dual functions— physical performance and aesthetics. Aesthetics are important since very few of the parts need to be painted or otherwise decorated if designed and manufactured with due diligence. On the other hand, even if we are designing the most aesthetically critical metal components such as exterior automotive parts, we mostly choose the metals and alloys based on the physical properties, weight, and cost. The aesthetics are left to the paint specialist, who will in most cases find a paint system (primer, paint, and application method) that will meet the cost, durability, and cosmetic requirements. In other words, aesthetics and physical properties are quite independent of each other. A vast majority of metal parts meet their aesthetic and environmental requirements just by getting brushed, plated, chromate conversion coated or anodized. Plastic parts not only need to meet the short-term color and appearance requirements, but also need to be resistant to long term color shift and fading. This paper is in two parts. Part 1 - Appearance and Color Factors - Material - Design - Tooling and Processing Part 2 –The fundamentals of Color and Appearance, Specifications, Measurement and Tolerances
How Poor Selection of Materials, Design, Tooling and Design Errors Affect the Aesthetics of Plastic Parts and What Designers Need to Know About the Science of Color and Appearance - Part 2
Vikram Bhargava, May 2020
Most engineers and designers come from the metal world. Therefore, many of them make assumptions on the predicted performance of plastic properties based on their metals background. Unlike metals, the knowledge of color and appearance is extremely important in the case of plastics. Most plastic parts have dual functions— physical performance and aesthetics. Aesthetics are important since very few of the parts need to be painted or otherwise decorated if designed and manufactured with due diligence. On the other hand, even if we are designing the most aesthetically critical metal components such as exterior automotive parts, we mostly choose the metals and alloys based on the physical properties, weight, and cost. The aesthetics are left to the paint specialist, who will in most cases find a paint system (primer, paint, and application method) that will meet the cost, durability, and cosmetic requirements. In other words, aesthetics and physical properties are quite independent of each other. A vast majority of metal parts meet their aesthetic and environmental requirements just by getting brushed, plated, chromate conversion coated or anodized. Plastic parts not only need to meet the short-term color and appearance requirements, but also need to be resistant to long term color shift and fading. This paper is in two parts. Part 1 - Appearance and Color Factors - Material - Design - Tooling and Processing Part 2 –The fundamentals of Color and Appearance, Specifications, Measurement and Tolerances
Improving Surface Quality of An Injection Molded Part By Adapting Rapid Heating and Cooling Technology
Raghavendra Janiwarad, May 2020
In injection molding, the cooling stage has significant impact on the overall part quality. Cooling time is a major contributor towards the molding cycle time. In conventional molding, the mold is maintained at a constant temperature for the entire duration of molding cycle. To achieve this, coolant at a constant temperature is pumped through the mold cooling channels. A relatively new molding technology called ‘Rapid Heating and Cooling Molding’ (RHCM) involves varying the inlet temperature of the coolant fluid, so as to maintain the mold temperature relatively hotter during filling stage and reduce the surface temperature to ejection temperature during the packing and cooling stages of the injection molding cycle. RHCM is best achieved with mold designs that allow for conformal cooling ofthe mold. Some of the key benefits of using RHCM are mitigation of weld line effects, improvement in the weld line strength, achievement of high-gloss surface finish, reduction of molding pressures, residual stresses and clamping force. In this paper, a comparative study is carried out between Conventional and RHCM molding to quantify the benefits of RHCM. The component chosen for this study is arepresentative center bezel part typically seen in automotive industry; a center bezel is used in the interiors of the car, and is required to be of high-quality surface finish and devoid of surface defects such as weld lines. Different materials, i.e., filled and unfilled grades from SABIC were used for this study. The molded parts were evaluated for gloss, L*, a*, b* values, visual defects, weld line appearance and its depth, scratch and mar resistance performance.
Improving Thermal Conductivity of CoContinuous Ternary Composites using Double Percolation Structure
Molin Guo, May 2020
The double percolation structure was used to produce thermally conductive polymeric composites including high density poly (methyl methacrylate) (PMMA)/polyethylene (HDPE)/ carbon nanofiber (CNF) and polypropylene (PP)/PMMA/boron nitride (BN) composites. Microscopy images showed that for both systems, most of fillers were in PMMA phase, confirming the hypothesis of the filler location by the thermodynamic theory. The thermal conductivity of the PMMA/HDPE/ CNF composite was higher than that of the HDPE/CNF and the PMMA/CNF composites with the same content of fillers loading when the CNF concentration got to 16 wt%. In addition, a similar phenomenon was also found when the BN concentration was above 10% in term of the PP/PMMA/BN composites. This study proved that double percolation structure was a useful way to improve the thermal conductivity of the polymer composites.
Improving Thermoforability of IPP Through Multilayer Coextrusion
Alex Jordan, May 2020
While the flow forces governing primary melt-based polymer processing techniques, such as extrusion and injection molding, have been extensively studied, characterization of forcesin secondary processes such as thermoforming is limited. In this work we utilize multilayer coextrusion to create an extruded film with 100s of alternating linear low density polyethylene (LLDPE) and isotactic polypropylene (iPP) layers; and by extension, 100s of interfaces. The combination of LLDPE, iPP, and these interfaces decreases the elastic storage modulus (E’) and broadens the rubbery plateau observed via dynamic mechanical analysis (DMA). The broadening of the rubber plateau is correlated with an observed improvement in LLDPE/iPP multilayer thermoformability compared to the homopolymer LLDPE and iPP films.
In Situ Injection Molding Thermotropic Liquid Crystalline Polymer Reinforced Nylon 6 Composites With MWCNTS Filler
Jier Han, May 2020
Thermotropic liquid crystalline polymer (TLCP), Vectra B, and nylon 6 (PA6) along with multi-walled carbon nanotubes (MWCNTs) forming multi-scale composites were processed via injection molding, yielding in-situ nanocomposites. Within this research, optimal injection molding processing conditions, in particular the temperature profile, for the production of MWCNTs filler reinforced in-situ composites were established. The optimized processing condition was aimed to minimize thermal degradation of PA6 and maintain mechanical properties of the composite. With the help of one percent addition of MWCNTs filler, the strength of the in-situ nanocomposites in the transverse to fluid flow direction was enhanced by 28%, while maintaining other tensile properties. MWCNTs also could help reduce the anisotropy in the nanocomposite. The experimental tensile results quantitatively followed the estimated values by the rule of mixture, which indicated PA6 had no thermal degradation.
incorporating Unmodified Lignin into Flexible Polyurethane Foams Formulation
Akash Gondaliya, May 2020
Industries that use polyurethane foam are looking for new sustainable and greener material to replace the petroleum-based polyols. Lignin produced as byproduct of pulp and paper and bioethanol industries is a suitable natural polymer to replace petroleum-based polyol in formulation of PUs. The emphasis was to study effect of different lignins obtained from different chemical processes and plant sources on the structural, mechanical and thermal properties of PU flexible foam and to achieve maximum lignin substitution. Additionally, we were interested to find correlation between lignin properties and performance of lignin-based PU foams to identify which lignin properties would affect the performance of developed lignin-based flexible PU foams and find the most suitable lignins for this application. It was seen that lignins isolated through organosolv process were better for PU fiexible foam applications. Overall, substitution of polyol with lignin increased compression strength, support factor, tear propagation strength and tensile strength of the developed PU foams.
Increasing the Process Window of Single-screw Extruders Operated with Regrind
Philipp Thieleke, May 2020
A feed zone geometry was developed which adapts the specific throughput when processing regrind to that of virgin material without adjustable means. This leads to an enlarged process window of the extruder. For this, the filling zone of a single-screw extruder was increased and a conical section was implemented in the feed zone which was designed with helical grooves. The experimental investigations with a 35mm extruder show that a complete alignment of the specific throughput is possible depending on the enlargement of the filling zone, the grooving as well as the angle of the conical section. Here, the self-adjusting compression is used which varies depending on the material’s particle shape. Additionally, approaches for the three-dimensional description of the throughput behavior using the discrete element method are shown. The uneven shape of regrind particles is transformed into so called superquadrics.
Influence of Additive Type On the Properties of Polyolefin Blends
Christoph Burgstaller, May 2020
The aim of this work was to compare the effects of compatibilisation with different additives on the properties of polyolefin blends, made from different PP and PE grades, to mimic the mixed polyolefins found in post-consumer waste and investigate ways to improve the properties of these mixtures. We found, that it is possible to compatibilize such polyolefin blends via the addition of ethylene-octen- or olefinic-block copolymers, where the type of copolymer shows an influence on the properties achievable. Also the blends show differently improved impact behavior, depending on the polyolefin which builds the major phase of the blend. These results show that it is possible to recycle such mixed polyolefin streams towards a suitable material with reasonable properties.
Influence of Variothermal Temperature Control on the Weld Line Quality of Extrusion Blow Molded Articles
Martin Facklam, May 2020
Extrusion blow moulding enables the cost-effective production of plastic hollow bodies with complex geometries and different volumes. The majority of the components are used as packaging articles for the consumer goods- and food industries or as technical components, e.g. in the automotive and chemical industries. Extrusion blow moulded products are often failing at the weld line. The quality of joint depends mainly on the welding temperature. In order to improve this critical area, the IKV is investigating the use of variothermal temperature control of the blow mould. This brings the advantage of being able to locally increase the temperature of the blow mould. By using this temperature control concept, the results show a significant improvement in the quality of the weld line.
Inline Surface Activation in the Multi Injection Molding Process
Frederik Mühlhoff, May 2020
Surface activation by plasma is a widely used process technology for connecting several components to each other. Usually, the activation takes place outside the injection molding machine as an additional step. With the development of the InMould-Plasma technology, the surface activation is fully integrated in the injection molding process, which eliminates an additional process step. Therefore, a plasma nozzle is directly connected to the mold. The plasma runs along a defined channel and activates the substrate surface in the closed mold. Through the technology, a strong bond of originally incompatible materials has been achieved. Without a surface activation, there is no adhesion of polypropylene (PP) and thermoplastic polyurethane (TPU). Studies on the peel strength of PP with TPU show that a treatment time of 5 s can drastically increase the material compatibility and achieve a peel strength of > 12.5 N/mm over the entire treatment area.
Intelligent Hybrid Hot Runner System for Optimized Polymer Products
Khalid Alqosaibi, May 2020
A novel “Rheo drop” concept is developed to advance the process of injection molding with hot runner systems. It controls shear rate during injection molding process in the hot drops, allowing us to process the material at lower temperatures since the viscosity can be reduced by increasing shear instead of increasing the temperature. Also, maintaining lower viscosity at the hot drop will prevent slug formation that causes incomplete filling defects when manufacturing thin walled parts. This innovative idea is suitable for temperature sensitive materials as they might degrade when subjected to excessive heat for longer periods. Analytical and experimental investigations were performed to validate the developed “rheo drop” concept. Simulations were performed using ANSYS fluent and the results confirmed that the concept was able to produce a sufficient amount of shear to significantly reduce the dynamic viscosity between injection molding cycles. To validate the concept experimentally, a hot runner mold was modified to retrofit the rheo drop technology. The results showed that the new concept was able to solve one of the molding significant issues, which is a defect that is caused by incomplete filling.
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