SPE Library

The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.

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Conference Proceedings

Calculation of the Anisotropic, Temperature-Dependent Thermal Expansion Coefficient (TEC) of Parts Made From Short-Fiber-Reinforced Polymers

Martina Vetter, Dietmar Drummer, May 2013

For the design of injection molded parts made of short-fiber-reinforced polymers, the anisotropic, geometry- and temperature-dependent thermal expansion coefficient (TEC) is often needed at the early stages of the design process, for example during material selection. The data usually available from material suppliers does not consider temperature dependency and the influence of geometries such as part thickness. State-of-the-art calculation methods such as the rule of mixture neither include these effects. Hence the development of simple models designed to estimate the TEC at the early stages of development is of interest. This paper deals with a method for engineers working in research and development to calculate the geometry- and temperature-dependent anisotropic TEC of parts made from short-fiber-reinforced polymers under consideration of fiber orientation. To evaluate the validity of the method, the results from the calculations were compared to measurements conducted on parts of different thicknesses. Here a good correspondence with the anisotropies of the TEC in different part directions was achieved.

Non-Isothermal Melt Crystallization Behavior of Poly(Ethylene Terephthalate)/Graphene Nanocomposites

Shigeru Aoyama, Yong Tae Park, Christopher W. Macosko, May 2013

Poly(ethylene terephthalate)(PET)/graphene nanocomposites were prepared by melt mixing to characterize their gas permeability and mechanical properties. With 2 wt% of few layered graphene, PET/graphene composite films show more than 70% decrease in N2 gas permeation and 10–21% increase in storage modulus, E'. Their non-isothermal crystallization phenomena from the melt were also investigated by differential scanning calorimetory (DSC). Crystallization temperature, Tc, of PET/graphene nanocomposites was higher than that of PET/MWCNT nanocomposites. This suggests that the nucleation effect of graphene was higher than that of MWCNT and was enhanced with the increase in concentration of graphene. On the other hand, PET/graphene nanocomposites show shorter half crystallization time, t1/2, than neat PET at lower concentrations, and t1/2 increased along with concentration of graphene. From Raman spectroscopy, it was shown that PET chains in nanocomposites are confined strongly in the presence of an excess of graphene. This confinement effect suggests that crystal growth rate of PET was suppressed by graphene in nanocomposites.

Raman Spectroscopy Study on the Addition of Peroxides as a Dispersing Additive in Multiwalled Carbone Nanotube Reinforced Polypropylene Composites

Shyam Sathyanarayana, Ganiu Olowojoba, Christof Hübner, Jan Diemert, Petra Pötschke, Frank Henning, May 2013

The addition of peroxides as a dispersing additive for multiwalled carbon nanotubes (MWCNT) incorporated in polypropylene is investigated with Raman spectroscopy both in the melt and on the extruded composite. Peroxide addition results in lowering of the melt viscosity of PP in addition to enhancing the defect concentration of the MWCNT. The better melt infiltration due to the former and evidences of CNT functionalization from the latter result in improved MWCNT dispersion quality in PP.

An introduction of the Planetary Extruder and areas of application

Harald Rust, Michael W. Batton, Thomas Malzahn, May 2013

Presenting and explaining the functions and history of the planetary extruder. Covering the advantages in physical characteristics, to include contact surface availability per rotation of the central spindle, Energy exchange capabilities (thermodynamics), control of mechanical energy and mixing properties. Technical advances made over the years in areas of manufacturing and employment of the planetary extruder in areas of de-gassing possibilities, individual blending of raw materials, liquid injection, mass- temperature and pressure measurement, control over fill degrees and residence times. Showing the advantages and applications of a modular built planetary extruder, in the adaptation of dis-continuous production processes into continuous processes. Introducing areas of application where the planetary extruder has shown major advantages and is used today throughout the world.

R&D Tax Credits – U.S. Tax Savings for U.S. Innovation

Michael J. Devereux, May 2013

One of the most under-utilized tax savings opportunities for companies in the plastics industry is the U.S. Credit for Increasing Research Activities (R&D tax credit). The R&D tax credit rewards companies who invest resources in innovation, product development, mold design, new materials or resins, and process development/improvement. In addition to Federal tax savings, several states have a similar program that rewards companies for the development or improvement to its products or processes. The types of activities that may qualify for the R&D tax credit include, but are not limited to the following: Developing new product designs Improving functionality or reliability or existing products Designing new molds or improving transfer molds Experimenting with processing variables to improve processes Improving manufacturing processes through automation Experimenting with new resins Performing PPAP or First Article inspections on new parts This article will discuss the following: The types of activities that may qualify for the R&D tax credit The types of expenditures that are eligible for the R&D tax credit The different methodologies for calculating the R&D tax credit The types of documentation necessary to substantiate a R&D tax credit claim The determining factors of whether the costs of externally-produced molds may be included as qualified expenditures The possible utilization of the R&D tax credit to offset taxes paid up to five years ago A case study of a plastics processor claiming the R&D tax credit

Properties of clay nanocomposites based on PETG by twin-screw extruder using supercritical CO2

Kwangho Jang, Jong Han Choi, Sangmook Lee, Jae Wook Lee, May 2013

A twin-screw extrusion process for PETG/clay nanocomposites using supercritical carbon dioxide was studied. Well-dispersed nanocomposites enhance the superior properties of the PETG/clay nanocomposites. So, we studied to achieve a good dispersion of the individual silicate layers of the clay. For even more enhancement of the dispersion of the clay in polymeric phase, supercritical CO2 can be employed in the processing of the nanocomposites due to the fast diffusion into the clay particles. The properties of PETG/clay nanocomposites are investigated by rheometer, thermal analyzer, permeability tester, and mechanical tester. The effects of clay contents and CO2 feed rate on the rheological and barrier properties of PETG/clay nanocomposites are presented. The results show that the rheological and thermal properties of the nanocomposites increase with the addition of clay. From the permeability test of nanocomposites, the barrier properties also increase. Moreover, the analysis of the nanocomposites also reveals that the use of supercritical CO2 leads to an increase of the rheological and barrier properties. From the results above, we strongly suggest that the use of supercritical CO2 assisted twinscrew extrusion is an effective way to improve the superior properties of PETG/clay nanocomposites.

Effects of Different Carbon Nanoparticles to the Morphology of PS/Carbon Nanocomposite Foam

Shu-Kai Yeh, Ming-Qing Ke, Kuo-Chung Cheng, Wen-Jeng Guo, Ren-Jei Chung, May 2013

In this study, polystyrene / carbon nanocomposite foams were made by in-situ polymerization and solution compounding. The foam was made by batch foaming using CO2 as the blowing agent. Various carbon nanomaterials such as nanographite, carbon nanofiber (CNF), carbon nanotube (CNT) and thermally reduced graphene (TRG) were used as the nucleation agent. In addition, processing variables such as foaming pressures and temperatures were also studied. The results indicated that TRG is the best nucleation agent because it possesses the highest surface area among these carbon nanomaterials. The cell morphology changed dramatically in the presence of carbon nanomaterials. This discovery not only opened up a new route for producing foams of a similar structure at a low foaming pressure, it also created a new application for graphene nanomaterial.

Manufacturability Study of Nano-Enhanced Fiber Reinforced Polymeric Composites (FRPC)

Ziwei Zhao, Na Zhang, Jose M. Castro, James L. Lee, May 2013

Due to the ever increasing cost of energy, there is an increased demand of lightweight materials. Towards that goal, we need to take advantage of new material developments such as is the case of nanoreinforced polymeric composites. The use of nanoparticles has shown improvement in mechanical properties of fiber reinforced polymeric composites (FRPC) but with adverse effect on processability, thus fully understanding the manufacturability of these processes is critical. Vacuum Assisted Resin Transfer Molding (VARTM) is the primary molding technique considered due to its significant advantages over other molding techniques and large size capacity. In this process, permeability plays a key role in determining processability. Understanding how permeability of these nano-enhanced FPRC is affected by the addition of nanoparticles is the main focus of this study.

Nano Direct Process for Compounding of Nanocomposites

Paul Andersen, Marina Matta, May 2013

Numerous varieties of polymer nano-composites have been developed on the laboratory scale and characterized regarding their properties. These include, nanofiller based on exfoliated clay, nanosilver, carbon nanotubes (both single and multiple wall geometry), zinc oxide, silica, and graphene among others. Carbon nanotubes (CNT) are of particular interest as they play a special role when it comes to improving or creating electrical conductivity in a polymer matrix. Currently most CNT based nano- composites are produced on co-rotating twin-screw compounding extruders via split feeding the polymer and the CNTs. However, processes using aqueous nano suspension are on the rise and offer new opportunities regarding technical performance, economical viability and reduction of health concerns related to the particle size of the CNTs. By using well pre-dispersed suspensions, which are already available on the market, it becomes easier to produce nanocomposites that provide the required characteristics, such as electrical conductivity. Also the usage of aqueous solutions enables dust-free handling of the carbon nanotubes. This presentation will introduce the Nano Direct Process and show its advantages in comparison to the conventional melt-mixing process.

Injection Molded Multi-Walled Carbon Nanotube/Polystyrene Composites: Effects of Alignment on Electrical Properties

Mohammad Arjmand, Uttandaraman Sundararaj, May 2013

The effects of multi-walled carbon nanotube (MWCNT) alignment on the electrical properties, i.e., electrical conductivity, electromagnetic interference shielding effectiveness (EMI SE), real permittivity and imaginary permittivity of MWCNT/polystyrene composites in the X-band (8.2 to 12.4 GHz) were investigated by comparing the electrical properties of injection molded samples, where MWCNTs were aligned, versus compression molded samples, where MWCNTs were randomly distributed. The results showed that the MWCNT alignment reduced the electrical conductivity and EMI SE tremendously. Nonetheless, it was observed that the MWCNT alignment significantly improved the dielectric properties of the MWCNT/polystyrene composites.

Breakup of Silica Particles Agglomerates in Corotateng Twin Screw Extruder: Modeling and Experiment

Avraam I. Isayev, Sug Hun Bumm, James L. White, May 2013

Extensive experimental studies on silica agglomerate breakup during compounding with polymer melts of various viscosities and polarities in a modular corotating twin screw extruder were conducted. Increasing the screw speed, melt viscosity and silica concentration were found to increase the silica agglomerate breakup. The effect of these parameters on agglomerate breakup was ranked as follows: silica concentration > polymer viscosity ?screw rpm. A good correlation between silica agglomerate breakage and power input was also found. A composite modular kinetic model for evaluating silica agglomerate breakup during compounding in a co-rotating twin screw extruder was developed. The kinetic constants of breakup and re-agglomeration of silica agglomerates were calculated based on the stresses applied to the agglomerates and their cohesive strength. These constants for silica agglomerates were found to be not significantly different at high concentrations. Comparison of the experimental and calculated results on the silica agglomerate size evolution during compounding with polymer melts indicated a reasonable agreement between them at high rotational speeds.

Blended Meat and Bone Meal Bio-plastic and Polyethylene Sheets: Enhanced Moisture Resistance and Mechanical Properties

Sam Lukubira, Amod A. Ogale, May 2013

Bioplastic sheets made from plasticized meat and bone meal (MBM) protein have high water vapor permeability (WVP) and low mechanical properties that are further affected by environmental humidity. This paper describes the improvement of tensile properties and moisture resistance of the sheets by two routes: (i) chemical crosslinking of the protein with calcium ions and (ii) blending with a synthetic polyethylene. The calcium ions led to a rigid glassy state of the modified MBM with 4 and 6 times higher tensile strength and modulus, respectively, but no significant improvement in WVP. Blending of polyethylene with MBM significantly improved moisture resistance and tensile properties.

Mechanical Evaluation and Damage Sequence Identification of Muliaxial Textile Reinforced Composites

Carlos R. Rios-Soberanis, Shuichi Wakayama, Takenobu Sakai, Emilio Perez-Pacheco, Jose Rodriguez-Laviada, May 2013

Mechanical properties and damage pattern of a multiaxial textile reinforced epoxy composite was evaluated by tension and bending test. A non crimp fabric (NCF) of [0°,+45°,90°,-45°] stacking sequence was used as reinforcement. Through the identification of the initiation sites and the coalescence of cracks was possible to correlate the damage with the textile geometry and its effect on the mechanical properties. Fractography was used as a tool to identify governing mechanisms and link these to the material internal structure and the textile geometry. Acoustic emission technique was employed to identify the mechanisms of fracture by correlating the signals of mechanical waves produced my damage with fracture stages. Additionally the effect of textile architecture on the composite mechanical properties and damage pattern was correlated with its damage initiation and propagation. Through a combination of experimental work and theoretical studies the mechanisms controlling the mechanical behavior are explained.

Screw and Process design for the manufacturing of Pa12 pipes for high internal pressure applications

Omar Estrada, Maria D. Noriega, May 2013

This paper presents the redesign of an existing polymer extrusion line involving a 75 mm screw design with a barrier zone and a mixing unit for the manufacturing of PA12 pipes for high internal pressure applications. The existing line was used for the manufacturing of HDPE pipes for gas supply. The new PA12 screw was designed to be used with an axial grooved feed zone. The bulk density was measured as a function of the container depth or bulk height (i.e. screw channel depth) and approximated to a function. A comparison between the improved approximation function and measured data for some common polymer families is shown. The bulk density is an important property of powders, granules and other solids. As a function, it is relevant for the appropriate design of screws to be used with grooved feed section.

An Examination of Variables in Multiaxial Impact Testing of Automotive TPO Products

Jonathan Stiffy, Laina J. Macklin, Robert W. Cribbs, May 2013

A study was coordinated between Washington Penn Plastic (WPP) and a major automaker to investigate multiaxial impact test results under a variety of testing parameters for two polyolefin alloy products — TPO-6087 P Black and PPC5UF0-Natural. It was determined that the use of a lubricated striker consistently lowered energy to maximum load results versus equivalent setups where no lubrication was used on the striker. The optimum test setup with respect to achieving ductile failures for TPO-6087 P Black required an ASTM striker/clamp setup, 2.2 m/s drop velocity, no striker lubrication and an ASTM disc specimen. The optimum test setup with respect to achieving ductile failures for PPC5UF0-Natural required an ASTM striker/clamp setup, 4.4 m/s drop velocity, striker lubrication and an ASTM disc specimen. The effect of sub-ambient temperature conditioning on these two materials —in particular the effect of time from freezer to impact when a remote chest freezer is used for sub-ambient conditioning of specimens —was also studied. It was determined that test results are significantly affected beyond a ten second time interval out of the freezer.

New Insights into Interfaces in Injection Molded Parts

Ines Kuehnert, Anne Schoenfeldt, Maria Auf der Landwehr, May 2013

The influence of process parameters, particularly with regard to the cooling rate, on the specific interfacial morphology and strength of paired polymers will be discussed. The focus is on the “cold” interface that occurs during a multi-shots injection molding process. A “cold” interface is consequently defined as the overmolding of a second melt to a chilled, hardened preform. In the experiments three different semicrystalline polymers polyoxymethylene, high density polyethylene and polypropylene were used. Regarding the strength two different types of interfaces were determined and for the visual inspection of interfacial morphology polarized light microscopy was used. The second important interface during injection molding process is the so called “hot” interface or well known as weld line which represents two melt streams meeting. The comparison between hot and cold interfaces presented here will focus on substance-to-substance bonds between plastics. An overview will show the propensity to fail for several thermoplastics, in case there are interfaces in the injection molded part. The strengths of hot and cold interfaces will be compared for certain thermoplastics. In conclusion, new aspects about a correlation between interfacial morphology, bonding strength and injection molding parameters are addressed.

Optimization of Electrical Properties of Bipolar Plastes Out of Highly Filled Compounds: Investigations on Conditioning and Thermal-Mechanical Stress

Jens Dörner, Antje Swoboda, Johannes Wortberg, Daniel Günther, May 2013

To attain an optimal and efficient bipolar plate, the used material, a ternary compound consisting of polypropylene, graphite and carbon black, as well as the molding process have to be fathomed. Therefore, steps for conditioning the highly filled compound before injection molding are compiled and the behavior of the matrix material polypropylene during thermal-mechanical stresses was analyzed. On the one hand this paper shows the influence of pellet forms (different L/D ratios), moisture absorption and barrel temperature on the resulting electrical resistance of the bipolar plates. On the other hand the consequences of process temperatures above the recommended temperature range of polypropylene are investigated via the dedication of different amounts of a polypropylene-based heat stabilizer masterbatch and residence times.

Rapid Crack Propagation (RCP) Performance of Unimodal Medium Density Polyethylene (MDPE) Pipe

Hitesh Patadia, Karen Lively, Mark J. Lamborn, Pam Maeger, Ashish Sukhadia, May 2013

As polyethylene (PE) pipe is being employed across an ever-widening range of applications, its resistance to rapid crack propagation (RCP) is a primary consideration for designers and end users. Test methods for determining a pipe’s resistance to RCP are the ISO 13478 Full Scale (FS) test and the ISO 13477 Small Scale Steady State (S4) test. Because of availability, low cost, ease of installation, and low maintenance, medium density polyethylene (MDPE) has been a customary material of choice for gas distribution lines for several decades. Presented here are the results of an experimental study to characterize the RCP resistance of chromium catalyst based unimodal MDPE pipe of common sizes using both the FS and S4 tests. While the S4 test results suggest lower RCP performance, the FS test results for all pipes tested indicated very adequate RCP resistance for use in gas distribution lines. This difference is attributed to the fact that the current S4-to-FS correlation factor of 3.6 is not representative of many current generation PE pipes, and a factor of 4.5 is more appropriate. The correlation factor of 4.5 determined from the current study matches very well with previously published data from our laboratory.

New Approaches of 2D Recursive Least Squares System Identification for Batch Processes

Yi Yang, Zhixing Cao, Furong Gao, May 2013

For most model-based control algorithms, the control performance is heavily relied on the model accuracy. This paper presents two new Two Dimensional Recursive Least Squares (2DRLS) estimation approaches for batch process system identification, a time wise 2DRLS (t-2DRLS) and a batch wise 2DRLS (b-2DRLS). Both approaches use parameters information from previous batches. The difference between them is that the t-2DRLS uses intermediate computation information from last sampling period, while the b-2DRLS uses the information from last batch but the same sampling period. The proof of convergence of b-2DRLS is given in this paper. Furthermore, both approaches have been applied to injection molding, a typical batch process, to test the performance of the design. An adaptive control scheme has been adopted and the experimental results of injection packing pressure control verified the advantages of the proposed approaches over the traditional RLS.

Polymerization of Lactide to Polylactic Acid and Co-polymers of Polylactic Acid using High Viscosity Kneader Reactors

Boyd T. Safrit, George E. Schlager, Ziang Li, May 2013

Polymerization of lactide to polylactic acid (PLA) can be performed using conventional reactor technology such as stirred tank reactors, but the conversion and/or final molecular weight may have to be controlled to a lower level. At higher conversion and/or molecular weight, the reaction mass will become very viscous, which limits the ability of conventional reactor technology to provide adequate mixing, minimize mass transfer effects on reaction kinetics, remove exothermic heat of reaction and ensure proper heat transfer in order to eliminate hotspots/thermal degradation. Kneader reactor technology has been used over 60 years in many high viscosity applications such as reactions and polymerization, devolatilization, and drying. This technology can handle the higher conversion and molecular weight polymerizations of lactide and other copolymers of lactide, while also providing the heat transfer required for proper temperature control. Using model kinetics and rheology data, a study was performed that shows the capability of kneader reactor technology for lactide polymerizations as well as other copolymers. Kneader reactor technology can also be used to remove the unconverted monomers from the polymer and expected results from the continuous operation of a polymerizer and finisher will be shown.