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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

Fabrication and Characterization of Electrospun Polyvinyl Alcohol Fibrous Nanocomposite Reinforced with Wood Flour
Sheikh Rasel, Remon Pop-Iliev, Ghaus Rizvi, May 2017

This paper focuses on the processing of high performance Polyvinyl alcohol (PVA) and wood flour (WF) fibrous nanocomposite mats using electrospinning. Successfully fabricated PVA filled with WF fibrous nanocomposites using electrospinning are hereby reported in the open literature for the first time. The effect of filler materials on fiber surface morphologies was investigated using environment scanning electron microscopy (ESEM). The respective mechanical and thermal properties of the resulting nanocomposite mats were determined as a function of WF contents. The mechanical properties such as tensile strength and tensile modulus improved significantly with the addition of fillers indicating good adhesion and dispersion of filler materials into the matrix. PVA/WF (20 wt%) fibrous nanocomposite showed the maximum tensile strength, and tensile modulus but minimum elongation at break. Thermal results show that introducing WF had no distinct effects in the thermal stability of nanocomposites. The developed fibrous PVA/WF nanocomposites could be of potential use for many industrial applications where high mechanical strength is needed, such as, filtration and mechanicaly reinforced applications.

Modeling the Monoaxial Stretching of Polypropylene Films by a Nonlinear Spring Dashpot Model
Frauke Marie Reinders, Volker Schöppner, May 2017

The stretching of semi crystalline materials such as isotactic polypropylene leads to an increase of the material characteristics (tensile strength, E-Modulus etc.). The trend towards using wider and faster film production lines causes the need to develop a better understanding of the complex correlation between molecular structure of the raw material, the processing conditions, the morphology of the cast film and the final film properties. In this investigation a viscoelastic model for the simulation of the stretching process is selected. In this study the definition of the suitable material parameters is supported by further characterization of the material.

Relationships between Low Temperature Impact Performance and Structures of Rotationally Molded Crosslinked High Density Polyethylene
Yueqing Ren, Xia Dong, Xuelian Chen, Xiaojie Sun, Shuguang Wang, Yafei Li, Dujin Wang, Wenbin Liang, May 2017

The low temperature impact performance of rotationally molded specimen is of great importance for the final products. Crosslinked high density polyethylene (XL-HDPE) is a preferred material for large chemical and fuel tank due to its superior environmental stress crack resistance and high impact strength. In the present research the drop weight impact strength (defined as ARM impact strength) of rotationally molded XL-HDPE was carried out at -40°C and the relationships between impact strength and microstructures were investigated. The results confirmed that the microstructures of XLHDPE molecules in the innermost surface layer dominated the low temperature impact performance of rotationally molded XL-HDPE articles.

A Study on the Entrapped Air Bubble in the Plasticizing Process
Byungohk Rhee, Hogeun Park, Bongju Kim, Jinsu Gim, Eunsu Han, May 2017

In injection molding, gas in the melt causes various defects in molded parts. As well as many other sources of gas in the injection molded parts, the entrapped air during the plasticizing process would be an important source of gas in the parts. The entrapped air bubbles in the screw channel were examined by the screw quenching experiment. To reduce time for investigating the effect of plasticizing condition on the bubble size distribution, a bubble detecting device with a capillary and pressure sensor was designed in this work. The result from the bubble detector experiment with different plasticizing conditions showed a similar trend which is observed in the samples in the screw quenching experiment. It proves the feasibility of the bubble detecting device to examine the bubble size distribution in the screw channel.

A Study on the Halo Surface Defect of Injection Molded Products
Byungohk Rhee, Joohyeong Jeon, Minsu Kim, Jaehyuk Chio, Eunyoung Park, Kyungho Jung, May 2017

The halo surface defect is one of the surface defects of the glossy products. A sudden change of the flow front speed causes the difference in the cooling condition of the surface, resulting in the halo. In this work, a quantified evaluation method for the halo by image processing was developed. Its feasibility was confirmed by compared with visual observation. The strongest influencing factor to the halo was the injection rate. A strategy of reducing the speed difference around the halo location was tested for eliminating the halo. The location of the halo was found by CAE analysis. As the injection rate was reduced to the minimum level at the location, the halo was successfully eliminated. The elimination of the halo was confirmed by both visual observation and the quantified evaluation method proposed in this work.

Designing Electrical and Electronics Equipment for the Circular Economy by Using Recycled Plastics
Brian Riise, May 2017

In order to conserve resources and at the same time spur economic growth, the European Union is pushing to establish a Circular Economy. For global businesses, including manufacturers of electrical and electronics equipment (E&EE), some of the principles of the Circular Economy will likely be applied globally rather than just within the European Union. This paper describes how the recycling of plastics from shredded waste electrical and electronics equipment (WEEE) fits within the Circular Economy, and provides some guidance to manufacturers looking to incorporate these recycled plastics in new E&EE. Furthermore, we provide recommendations on the design of E&EE such that plastics may be recycled more easily in the future.

Surface Texturing of Composite Materials by Induced Damage: Surface Morphology and Friction
Reza Rizvi, Sharon Li, Ali Anwer, Hani Naguib, Tilak Dutta, Geoff Fernie, May 2017

Ice is a unique natural substance, whose solid state behavior is deceiving due to the pervasive presence of a liquid-like surface layer, especially at temperatures close to its melting point (>-10°C). As a result, ice is a very slippery, self-lubricating substance on which most materials, thought to give high traction (e.g. elastomers), cannot achieve high coefficients of friction (COF ~ 0.1). Here, we describe the high friction behavior (COF ~ 0.5) of a new class of textured elastomer fiber composites made using a facile fabrication method of cutting and rearranging molded composites. These fibrous TPU composites have uniformly distributed surface protrusions that are capable of penetrating and interlocking with an ice substrate underneath resulting in static COF that are 4- 7X higher the TPU elastomer by itself. Increasing the fiber content improves the surface structure characteristics, namely protrusion density, and hence improves the friction coefficient. Furthermore, increasing the contact pressure increases the depth of protrusion penetration and hence improves the friction force. These structure-property relationships were verifiable through a mechanics model, with the appropriate normalization, that describes the characteristic forces on a single fiber. Strong potential applications of such textured elastomer composites exist for winter safety applications such as footwear and tires.

Rotational Molding of Polylactic Acid and Agave Fiber Biocomposites
Jorge R. Robledo-Ortiz, E.O. Cisneros-López, A.A. Pérez-Fonseca, D.E. Ramírez-Arreola, R. González-Núñez, Y. González-García, D. Rodrigue, May 2017

In this work, biocomposites of agave fibers (Agave tequilana Weber var. Azul) and polylactic acid (PLA) were produced by rotational molding. In particular, a simple dry-blending technique was used to disperse the agave fibers in the biodegradable polymer matrix. The effect of fiber content was studied (0, 10, 20, 30, and 40 wt.%) and the samples were characterized in terms of morphology, density and porosity to relate with mechanical properties (tensile, flexion, impact and hardness). The results showed that rotomolded biocomposites were successfully produced, but had high porosity leading to lower properties for fiber contents above 10%. It was possible to observe that low fiber contents produced the best morphology, indicating that there is an optimum fiber content to get well-distributed fibers in the matrix.

Processing MICA Based Pigment Masterbatch
Robert Roden, Prakash Hadimani, Pradeep Bakshi, May 2017

Many effect pigments used in thermoplastics such as those used for pearlescent appearance are comprised of coated mica crystalline platelets. For effective coloration of thermoplastics the mica structure should not be altered. If the mica platelet is reduced in size while being compounded into the plastic it will alter the appearance of the plastic. It is desirable to maintain the mica structure in order to produce the best possible appearance of such pigments. To avoid attrition of the platelet structure exposure to shear during processing should be avoided, particularly when compounding high concentrations of pigment for masterbatch production. Co-rotating twin screw extruders are used for the compounding pigments into thermoplastics. Typical kneading blocks have predominantly been used with this equipment for the compounding of pigments for many decades. The mixing properties of this element include compression and simple shear which causes damage to the mica structure. Avoiding compression through the use of elongational mixing can significantly reduce damage to the crystalline structure of mica and enhance the appearance of mica based pigments. New mixing alternatives are available today that eliminate the shear peaks that are characteristic of typical kneading blocks, and utilize highly effective and efficient elongational mixing for the dispersion and distribution of mica based pigments while preserving the platelet structure.

Rotational Molding of Linear Low Density Polyethylene with Different Concentrations of Ground Tire Rubber
Denis Rodrigue, Y. Dou, May 2017

In this work, ground tire rubber (GTR) was dryblended with linear low density polyethylene (LLDPE) to produce thermoplastic elastomer parts by rotational molding. In particular, different GTR concentrations (0, 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50% wt.) were incorporated to determine the effect of the rubber phase on the processability and overall properties of the parts. Each composition was characterized in terms of morphology and mechanical properties (tensile, flexural and impact). The results show that the addition of the rubber phase decreased the tensile and flexural moduli and strengths, but the tensile elongation at break was always above 100%. This good elasticity produced impact strengths higher than the neat matrix with an optimum GTR content around 20% wt.

Low Density Open Cell Flexible Foams with High Tortuosities and Mechanical Properties Highly Dependent on the Strain Rate
Miguel Rodriquez-Perez, Eduardo Lopez-Gonzalez, Santiago Muñoz-Pascual1, Cristina Saiz-Arroyo, May 2017

This paper describes the mechanical behavior in compression, at both low and high strain rates, of several low density open cell polyolefin cellular materials with different gas phase tortuosity of the cellular structure. Due to the high tortuosity of some of the polyolefin foams under study they have a mechanical behavior similar to that of open cell polyurethane foams at low strain rates (i.e. they could be used for comfort applications) and they have a similar mechanical behavior to that of closed cell polyolefin foams at high strain rates (i.e. they could be used in body protection applications). Therefore, these new materials with high tortuosities have an unique mechanical performance strongly influence by the strain rate.

Analyzing the Viscous Dissipation of a Two-Dimensional Flow of Non-Newtonian Fluids in Single Screw Extruders
Wolfgang Roland, Jürgen Miethlinger, May 2017

For modeling the flow of non-Newtonian polymer melts in single screw extruders numerical methods are required in general. In this study the viscous dissipation and the conveying characteristics in the melt channel of single screw extruders are analyzed for a two-dimensional, fully developed flow of power law fluids. Therefore three different numerical methods are presented and the results are compared. Furthermore, a comprehensive parametric design study is shown, analyzing the viscous dissipation depending on three independent parameters: (i) pitch to diameter ratio, (ii) power law exponent, and (iii) dimensionless pressure gradient. The derived results for the viscous dissipation can be used to calculate the mean melt temperature profile more precisely.

In-Situ Visualization and Cell Growth Modeling in a Polymeric Foaming Process
Sandra Romero Diez, Patrick C. Lee, May 2017

In this paper, we consider a two-dimensional model of the foam nucleation process of CO2 in polystyrene (PS) matrix by random initiation of growing bubbles in time and space. The model was extended to account for the simultaneous cell nucleation, growth, and collapse processes of the foaming bubbles at two different viscosities of PS resins. By means of connection among neighboring bubbles, secondary nucleation behaviors emerged from a multi-bubble system were attempted in simulations. The resulting cell size distribution (CSD) of bubbles shows power law behaviors for both simulations and experiments. The cell size distribution and morphologies obtained from the numerical simulation agreed with the snapshot pictures of the experiments qualitatively and quantitatively. Finally, different nucleation and growing rates were investigated to understand the relationship between the bubble nucleation /growth and final morphology of the foam structure. Potential applications lie in the analysis of the resulting micro-/nano-cellular structures due to secondary nucleation and the foam stabilization.

The Adhesion of LSR Thermoplastic Composites after Storage Tests
Annette Rüppel, Ralf-Urs Giesen, Hans-Peter Heim, May 2017

The adhesion properties of liquid silicone rubber (LSR) and different thermoplastics (PC, PA, and PP) were examined in this investigation. In order to guarantee the adhesion of both components, an activation (silicatization) of the TP surface, which is a conventional method, was carried out. Furthermore, the long-term stability of the silicatization (storage of the activated surfaces) as well as the wetting behavior were investigated. Moreover, microscopic investigations were performed to analyze the activated thermoplastic surfaces. The test specimens were produced on a 2-component injection molding machine. In accordance with the guideline VDI 2019, the peeling resistance was determined and the results were compared.

Characterization of Developed Hybrid Moldings by Textile and Short Fiber Reinforced Composites
Taiga Saito, Kazuharu Yasuda, Asami Nakai, Akio Ohtani, May 2017

Advanced material is developed by using continuous fiber reinforcement to achieve higher strength than can be obtained with injected composite material. High forming performance has been achieved by using the cloth-like textile fabric material, made from combined filament yarn. By applying the developed textile composite, parts can be molded with deep drawing and complex shapes with ribs. Moreover, high weld strength has been achieved between the materials of compression molded textile composite and injection molded short fiber reinforced material in hybrid molding.

Effect of Die Design on Liquid-Liquid Mixing in Polymer Based Additive Manufacturing
Aditya Sangli, Marcelo Arispe-Guzman, Connor Armstrong, David Bigio, May 2017

Incorporating liquid fillers in additive manufacturing processes can produce liquid-filled solid parts with unique properties. To develop this, the behavior of immiscible droplets in a polymer matrix subject to different kinds of flows is explored. Castor oil droplets, with a range of capillary numbers much higher than the critical capillary number, were injected in a matrix of Silicone oil and subjected to flows within a converging channel. The rate of change of capillary number as the droplet moves down the channel was measured to illuminate the effect of the die design. The affine state was not reached when the droplets were deployed in the center but was achieved when injected in an offset position. This data is valuable to understand the effect of the die on the deformation induced on immiscible droplets and is one of the preliminary steps to incorporate liquids in additive manufacturing.

Utilizing Dynamic Hold Capability of Servo-Driven Ultrasonic Welders in Studying Cooling Phase of the Ultrasonic Welding Process
Alex Savitski, Leo Klinstein, Kenneth Holt, David Cermak, Hardik Pathak, Keith Pedziewiatr, May 2017

Ultrasonic welding of thermoplastics is widely used by many industries to fuse together two parts in a short time without introducing additional consumables such as fasteners, adhesives, or solvents. The recent development of servo-driven ultrasonic welders, as opposed to pneumatically driven welding machines, introduces unique levels of control throughout the welding cycle. This study focuses on the final phase of the welding process, i.e., the hold cycle, and the benefits that the servo-driven ultrasonic welders can provide to this final phase by controlling both hold distance and the velocity at which this final phase is accomplished.

Micropelletization of Virgin and Recycled Thermoplastic Materials
Christian Schäfer, Jackson S. Bryant, Tim A. Osswald, Stefan P. Meyer, May 2017

Traditional polymer powder and micropellet based processes, such as powder bed fusion and rotational molding, have been in increased demand in modern processing industries. These processes require polymer powders and micropellets with a small particle size, narrow size distribution and defined geometry for a variety of polymer resins. Therefore, micropelletization technologies, where particles in the size range of 50 to 1000 µm are generated, have been attracting growing attention over the past decade. A new technique, developed at the Polymer Engineering Center, yields micropellets with a controlled morphology and narrow particle size distribution. In this process, a polymer melt is extruded through a capillary and is subsequently stretched with a hot air stream until flow instabilities cause it to break up into particles. Small changes in process conditions result in different size distributions and particle shapes, such as lentil-like pellets, fibers and thread segments. This work shows how material properties and processing parameters influence the produced micropellets. Besides the processing of virgin thermoplastic material, recycled high density polyethylene flakes are used as feedstock for the micropelletization process in order to show the capability of this process to contribute to current polymer recycling efforts.

Effect of Pre-Cross-Linking on Mechanical and Rheological Properties of Solid Silicone Rubber and its Processability in Extrusion Blow Molding
Sarah Schäfer, Christian Hopmann, May 2017

The blow molding process offers the possibility of reproducible, fully automatic and therefore cost-efficient mass production of complex hollow bodies. Due to the poor mechanical properties of uncured rubber, it has not yet been used for the manufacturing of elastomeric hollow parts. In this contribution, it is shown that with a defined pre-cross-linking of solid silicone rubber the blow molding of the material is possible. With pre-cross-linking the mechanical material properties can be adjusted precisely. This allows parison extrusion without strong drawdown. During the forming, it provides the necessary elasticity while maintaining the weldability and formability of the material. But pre-crosslinking also influences the materials rheological properties. Preliminary investigations showed pre-crosslinking has to take place in the blowing head bevor the material leaves the die. Therefore, changes in rheological material behavior are investigated and considered for the flow channel design. It is shown that the pre-cross-linking allows the blow molding of elastomeric hollow bodies with a surface stretch ratio of 3.6 to 1. However, precross- linking can also lead to flow instabilities such as wall slippage and melt fracture.

Influences on the Flow Behaviour of Phenolic Molding Com-Pounds Measured in Continuous Kneaders
Thomas Scheffler, Daniel Methe, Nils Schmeißer, Michael Gehde, May 2017

Due to their complex flow and curing behavior the quality of parts made from thermosetting molding compounds depends to a high degree on the reactive and viscous characteristics during their processing. In the presented studies a continuous kneader was used to investigate how those characteristics depend on the filler content of the fluid molding compound, the grain size distribution and the present material humidity. Therefore, the grain size of different batches of three thermosetting molding com-pounds was examined, they were purposefully impinged with high air moisture and their flow resistance was measured using various kneader temperatures. The results display a strong dependence of the flow resistance on the filler content, the respective composition of the molding compound and the water content within the material. They will be discussed and interpreted according to their influences within the injection molding process.

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