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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
Influence of Processing Route on the Properties of Polyolefin Blends
One of the streams from plastics waste collection is a mixed polyolefin stream, which cannot be separated completely with reasonable effort at the current technological state.
The aim of this work was to investigate the influence of the processing route, realized by different plastic processing machines, on the properties of selected polyolefin blends, made from different PP and PE grades as well as compatibilizing additives, to mimic the mixed polyolefins found in post-consumer waste.
We found, that the processing route influences the properties in regard to the shear brought into the materials – only dry-blended and injection molded blends yield lower properties than the ones which were prepared by the other processing machines. This is more pronounced when compatibilizers were added. These results show that several processing machines can be used to establish such blends, which is an important finding for mixed polyolefin stream recycling, as there not only a good mixture in the blend needs to be established, but also the processing machine has to be stable and unsusceptible to foreign materials in the stream.
Analysis of Parameters for Heat Sealing and Ultrasonic Sealing of PET/PE Films.
Sealing of laminated polymer films is done by applying/generating heat in the seal area. Heat causes the low melting point inner layer to melt and intermolecularly diffuse with a matching layer, creating a joint. Two common processes for sealing are heat sealing and ultrasonic sealing. Different process parameters for both heat sealing and ultrasonic sealing were evaluated individually in order to find a relationship with peel strength. For this experiment a two ply film of PET/PE was used. In heat sealing, increasing the sealing temperature and sealing time caused an increase in peel strength. Increasing heat sealing pressure decreased peel strength. However, this was shown to be due to excessive pressures, which resulted in PE squeeze. In ultrasonic sealing, the effects of weld time and weld force on peel strength were evaluated. For ultrasonic weld time, initial increases caused large changes in peel strength with subsequent changes being less pronounced. Similarly, for ultrasonic weld force, initial increases in weld force caused increases in peel strength. However, at higher weld forces, peel strength decreased due PE squeeze out.
Some Properties of 100% Recycled Ocean Plastic Polyolefins
Levels of plastic waste accumulating in the oceans are continuously rising and prompting an increase in concern on their negative environmental impacts. To help close the gap and create a circular life cycle for ocean plastics, this study begins to show the changes in chemical and engineering properties of polyolefins collected from a marine environment. Three ocean plastic polyolefins, high density polyethylene, low density polyethylene, and polypropylene, were mechanically recycled and then injection molded. The ocean plastics’ chemical characteristics were then characterized via FTIR to observed the impacts of environmental degradation. Thermal, rheological, and mechanical properties were all studied and related to the chemical structures and typical accepted values. All ocean plastic olefins were found to have properties similar to their terra-firma counterparts, however degradation was observed and is discussed in terms of the measured properties.
Characterization of polypropylene/hydrocarbon resin blends for 3D printing
Additive manufacturing (AM) of polyolefins, such as polypropylene (PP), employing filament-based material extrusion (MatEx) has gained significant research interest in recent years. The semicrystalline nature of PP makes it challenging to process using MatEx. The addition of amorphous low molecular weight hydrocarbon resins into PP matrix was found to delay the onset of crystallization of the blends. The slow crystallization behavior, as evident by the increased crystallization half-times, aided the relaxation of residual stresses during MatEx of PP blends that resulted in manufactured parts with reduced warpage. Rheological characterizations were performed on the PP blends revealing the shear-thinning nature. The combined interaction among crystallization rates, timescales, and morphology was found to affect the interlayer welding process during MatEx. Mild thermal annealing of the manufactured parts resulted in mechanical properties which approach that of injection molded parts.
Styrenic Block Copolymers for Enabling Improved Performance of Post-Consumer Resins
Improving the reusability of plastic parts, increasing the usage of post-consumer resin (PCR), and converting mixed PCR streams into high value resins are three key challenges facing the plastic recycling industry. To address these challenges, CirKular+‚Ñ¢ products were developed by Kraton Polymers to enable plastics upcycling and circular economy solutions. These products enable multi-resin compatibilization and performance enhancement of PCR resins across a wide range of applications. By leveraging the versatile chemistry of styrenic block copolymers, polymeric additives have been developed that benefit plastic recycling in multiple ways, such as improvement in properties of recycled resins and blends of virgin and recycled resins, and compatibilization of mixed PCR resin streams. In addition, these polymeric additives provide the performance enhancement at low loading levels, which in turn leads to an excellent balance of properties and low formulation cost. In this paper, several application-specific test results and case studies will demonstrate the value of these polymeric additives.
Sustainable Processing Aids to Enhance the Performance of Plastics with Recycled Content
In response to government and consumer demand for sustainable solutions to the escalating plastic waste crisis, plastic compounders and manufacturers are seeking to increase the level of post-consumer recycled content in their product formulations. The inherent variability of recycled resin streams presents challenges related to operational efficiency and product performance; thus, there is an increased need for processing aids that can assist manufacturers in their quest to balance operational efficiency with sustainability. GreenMantra® Technologies has developed and commercialized an innovative advanced chemical recycling technology that converts recycled plastics into specialty polymers and synthetic waxes that can function as processing aids in plastic production. This paper presents two case studies that demonstrate how GreenMantra’s additives enhance the manufacturing efficiency of plastic extrusion processes and maintain the physical properties of polymer systems containing 25-100% recycled plastics. Certified as containing 100% post-consumer recycled plastics, GreenMantra’s additives enhance the sustainability of the polymer system while enabling the formulation flexibility for plastic manufacturers to incorporate higher recycled plastic content without sacrificing performance.
Product-Related Process Data Acquisition in Blown Film Extrusion
In today’s advanced plastics processing industry, a quality-based control of an entire production line is desirable. This requires a product-related process data acquisition allowing to merge process data and quality data with high accuracy. In this context, an approach for the blown film extrusion process will be presented. An experimental study confirms that the tool of residence time distribution analysis is suitable to identify the system behavior of a blown film line. On that basis, suggestions are made on how to proceed with the implementation of a product-related process data acquisition.
Machine Learning and Data-Driven Additive Manufacturing
Additive manufacturing has emerged as a disruptive digital manufacturing technology. However, its wild adoption in the industry is still impacted by high entry challenges of design for additive manufacturing, limited materials library, processing defects, and inconsistent product quality. Machine learning has recently gained increasing attention in additive manufacturing due to its exceptional data analysis performance, such as classification, regression, and clustering. This paper provides a review of the state-of-the-art machine learning applications in different domains of additive manufacturing.
Effects of Steam Heat and Dry Heat Sterilization Processes on Polylactic Acid with Hydroxyapatite Composite Printed by FFF
3D printing is used for various medical applications, such as the manufacture of guides for surgical operations, custom medical instruments, and low-cost medical applications. In few of these studies that have been performed, the effect of sterilization on these parts has not been considered yet. The fused filament fabrication process (FFF), which is the most widely used today, is used for the making of these guides and instruments. One of the most used materials in the FFF process is polylactic acid (PLA) due to its ease of printing, however, this could be degraded with the sterilization processes by steam heat and dry heat and lose its dimensional accuracy and resistance, something required for medical applications. The purpose of this study is to determine the effects of the steam heat and dry heat sterilization processes on the mixture of PLA and hydroxyapatite (HA) to check whether this mixture can be used in medical applications that are not implantable in the human body. The percentage by weight of hydroxyapatite used is 5%. To study the effect of sterilization processes already mentioned, 3D specimens were printed for flexural, tensile, Shore Hardness and impact mechanical tests. Thermogravimetric analysis (TGA), Differential scanning calorimetry (DSC) and Dynamic mechanical thermal analysis (DMTA) tests were also performed. It is concluded that the blend of PLA and hydroxyapatite increases its resistance to temperature but decreases its mechanical characteristics.
Fischer-Tropsch Hydrocarbons as Processing Aids in Injection Molding: An Overview
Polymer producers and converters are continuously evaluating potential options to reduce costs by producing faster, reducing energy consumption, reducing scrap and improving article properties. Recently, however, sustainability and overall environmental impact have also become prominent themes for converters, as a result of the pressure to minimize the footprint of the plastics industry on the environment.
Polyolefin blown film and injection molding are large polymer conversion market segments that have received significant attention in terms of equipment improvements and formulating principles. Processing aides are commonly used in blown film extrusion and injection molding. Specifically in injection molding, silicone spray is used to ease the removal of the article from the mold, thereby saving cycle time. Silicone spray is, however, difficult to remove from the final part. An alternative is to use higher molecular weight Fischer-Tropsch (FT) hydrocarbons as a polymer processing aide and mold release agent due to good compatibility with the polymer compound matrix. This paper gives an overview of the use of FT hydrocarbons as processing aides in injection molding. Examples of more than 15 years of experience in the global marketplace, ranging from the production of small to large articles, are shown. Formulating with these hydrocarbons allows the converter to reduce cycle time, produce faster to reduce labor, to reduce energy consumption and improve certain properties of the injection molded article. Ultimately FT as a polymer processing aide could be an important tool to a converter to reduce manufacturing costs and improve quality.
Applying the Shooting Method to Predict the Co-Extrusion Flow of Non-Newtonian Fluids Through Rectangular Ducts
Because of their versatile properties multi-layer polymer products have a high industrial relevance. Process understanding and prediction of the flow characteristics of co-extrusion, hence, is of major importance. When the shear-thinning behavior of polymer melts is to be included in modeling, there is no alternative to numerical solution methods. We present a numerical solver that is based on the shooting method to predict two-layer co-extrusion flows of non-Newtonian fluids within rectangular ducts of infinite width. The pseudo-plastic flow behavior of polymer melts is modeled by the power law according to Ostwald and de Waele. We carried out a dimensional analysis of the governing equations based on the theory of similarity, and identified four independent dimensionless parameters that fully describe the problem. To solve the dimensionless governing equations, we developed a numerical solution procedure. Additionally, we conducted an extensive parametric study by varying these independent dimensionless quantities over a wide range that covers almost all applications in industry. The numerical results offer insights into the influence of the independent parameters on, for instance, pressure gradient, (interfacial) shear stress, velocity profile, and viscosity distribution.
Investigations of the Influence of Process Conditions on the Fiber Length Reduction for Recycled Carbon Fibers
A new carbon black product was developed at Birla Carbon with ultra-high jetness and bluish undertone for high color applications in plastics. The new product was demonstrated with improved jetness in various polymer systems over the existing high color products, especially achieving a 40% improvement in polyamide 6. The new product shows great potential for ultra-high jetness plastics applications including automotive, household appliances, and consumer electronics.
Improving the Hydrophobicity of Polymers through Surface Texturing
Introduction of surface textures has long been used to improve the hydrophobicity of solid materials. This study focusses on understanding the effects of various micro-texture geometries on the hydrophobicity of textured polymer surfaces. Square pillar, cylindrical, hemispherical and conical surface features, both protrusion and cavity, are considered in this study for two polymers. Employing the well-known models, the study shows that introducing textures on polymer surfaces generally increases the contact angle and, therefore, improves the hydrophobicity of polymers. The effect of surface texture on hydrophobicity significantly varies with texture geometry and dimension. The study provides useful guidelines for improving hydrophobicity of polymers by introducing textures on the surface.
Research on Transfer Learning Applied to Characteristic Prediction of Injection Molded Products
With advances in computing technology, applications of computer-aided engineering (CAE) technology are becoming widespread in diverse industries. Specifically, machine learning is now being applied to fields such as that of materials design and production which is the field within which this study focuses. However, problems in implementing this technology arise in regard to lengthy analysis times and a lack of suitability in regard to on-site, real-time judgments during some production processes.
This study addresses these issues in regard to the problems of applying CAE to the injection molding production process where quite complex factors inhibit its effective utilization. In this study, an artificial neural network, namely a Back Propagation Neural Network (BPNN), is utilized to render results predictions for the injection molding process. By inputting the plastic temperature, mold temperature, injection speed, holding pressure, and holding time in the molding parameters, these five results are more accurately predicted: EOF pressure and maximum cooling time, warpage along Z-axis, shrinkage along X-axis and shrinkage along Y-axis. This study first uses CAE analysis data as training data and reduces the error value to less than 5% through the Taguchi Method and the Random Shuffle Method which we introduce herein, and then successfully transfers the network which CAE data analysis has predicted to the actual machine for verification with the use of transfer learning.
Of particular interest, is this study's use of a Back Propagation Neural Network (BPNN) to train a dedicated prediction network through using different, large amounts of data for training the network, which is proven fast and that can predict results accurately using our optimized model.
Shear Induced Crystallization Through Altering Polymer Melt Flow Area
A novel additive manufacturing technique has been developed in the Manufacturing Science Laboratory at Lehigh University.The technique utilizes an extrusion based 3D printer, which has the ability to regulate the areaof the polymer flow inside the extrusion head, thus, allowing precise control over shear rate applied to polymer melt. The controlled shear alters the melt rheology, which in turn controls the evolution of crystallinity in the printed parts. The temporal control of shear translates to spatial control of melt rheology. Thus, the localized evolution of molecular orientation and nucleation/crystallization kinetics as well as the mechanical and optical properties can be precisely controlled during the additive manufacturing process. In this research, a semi crystalline poly-lactic acid (PLA)was utilized to validate the developed technique of controlling the shear rate while printing. The confinement will induce shear on the polymer the degree of which can be controlled by the gap between the conical cavity and theconical extruder tip. The analytical modeling results indicate that this strategy can increase the induced shear rate. Preliminary experimental analysis validated an increase incrystallinity percentage up to 16%.
Solid-State Shear Pulverization of Ultra-High Molecular Weight Polyethylene for Mechanical Recycling
Solid-State Sheer Pulverization (SSSP) is acontinuous processing technique in which low-temperature application of shear and compressive forces impart changes in structure and properties to different thermoplastics. In this paper, SSSP is applied to post-industrial ultra-high molecularweight polyethylene (UHMWPE) materials for a technical feasibility study of mechanical recycling of high-molecular weight, high-melt viscosity polymers. The SSSP process is able to effectively reduce the particle size while also mechanochemically enhance the crystallization behavior of the polymer.
Simulating Flow through Channels with novel Cross-Sections: Pressure Drops and Flow Coefficients
Despite the evolution of several new die concepts since the invention of spiral mandrel dies in the 1960s, the basic geometry of the spiral grooves themselves remained unchanged. The cross section of the groove is u-shaped, i.e. consists of a rectangular and a semi-circular area. Typically, the spiral grooves abruptly merge into the annular gap, forming sharp edges. These edges negatively affect process performance e.g. by potentially damaging the polymer chains or provoking deposits. Rounding off these edges ease the effect to some extent, but alternating the general shape of the cross section has obviously a much better potential to influence the process characteristics of the die.
This paper systematically investigates spiral mandrel dies with channels of different cross-sections: type I is u-shaped, as it is normally used for spiral dies, type II is u-shaped with one side inclined at 45 degrees and type III is a wider variation of the u-shape. To calculate the pressure drop along channels with such cross-sections, it is common practice to use correction factors. These so-called flow coefficients correct the error introduced by the geometrical simplifications necessary to obtain analytical solutions. This paper presents flow coefficients calculated from CFD results for the given cross-sections.
Effect of Glass Fibers on the Viscosielastic and Thermomechnical Properties of Poly(Ether Ether Ketone)
The effect of glass fiber on the viscoelastic properties, thermal stability, permittivity and volume resistivity, as well as stress relation behavior of poly(ether ether ketone) (PEEK) was investigated using dynamic rheology, TGA, broadband dielectric spectroscopy and DMA over a wide range to temperature. The complex viscosity of PEEK filled glass fiber with 30 wt.% increases by one order of magnitude at 360 oC compared to the unfilled PEEK indicating that the glass fibers inhabited the polymer chains motion and reduced the free volume at high temperature in the melt. The viscosity and dynamic moduli (G′ and G″) of both PEEK and 30 wt.% glass fiber filled PEEK were not very sensitivity to the temperature variation (i,e.; the viscosity, G′ and G″ slightly decreased with increasing temperature). The angular frequency dependence of complex viscosity was found to be well described by Carreau–Yasuda model. It was also observed that the thermal stability of PEEK improved significantly by adding glass fibers. In addition, the relaxation modulus master curve at 200 oC reference temperature for glass filled PEEK is significantly higher than that of pure PEEK due to the excellent reinforcement effect of the glass fibers.
Crystallization Behavior and Impact Performance of PA6 Based Nanocomposites
PA6-based in-situ nanofibrillar composites, containing polyphenylene sulfide (PPS) nanofibrillar domains with average diameter around 60 nm, were produced combining melt compounding and hot stretching. Then, effect of this fibrillar network on the crystallization behavior of PA6 composites was investigated using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and polarized optical microscopy (POM). Results indicated no significant increase in the composite’s crystallinity due to PPS nanofibrils; however, the nanofibrillar network did induce a significant difference in the crystallization curve with the evolution of a high temperature crystallization peak. The impact performance of nanofibrillated PPS-PA6 was improved with 3 wt.% PPS nanofibrils, which was explained by the interconnected fibril network and the formation of transcrystalline structures and small crystal size in the presence of the fibril network.
A Method for Cross-Sectional Analysis of Polymer Welds
A fundamental aspect of a polymer weld is the presence of intermolecular diffusion between the two joint surfaces. Without the movement of polymer chains across the melt interface, then the bond achieved is merely adhesive, and not a true weld. Therefore, it is essential to be able to determine where diffusion has occurred in order to properly evaluate weld quality. One of the simplest methods to do so is via cross section and heat treating of a weld section. The scientific basis for this process and the experimental method to complete it is presented here.
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