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

Elimination of Flash –A Novel Micro-Embossing Technique

Greg Harmon, David Grewell, May 2007

Micro-electro-mechanical systems (MEMs) with fluidic devices rely on micro features typically ranging from 10 to 200 ?m in size. To produce these features on polymer substrates with high quality and fidelity, existing techniques typically have long cycle times and are relatively expensive. It has been shown that localized heating with ultrasonic embossing has short cycle times but generates flash. This paper reviews the elimination of this flash by using micro-cellular foamed polystyrene substrates, that self absorb the generated flash. Standard dog bone shaped features were embossed with various parameters and the resulting features characterized by optical end electron beam microscopy.

Influence of Particle Size on Melting and Energy Consumption during Compounding: Does the Effect Hold at Scaled-Up Conditions?

Mohamed Esseghir, Anthony C. Neubauer, May 2007

A number of studies have shown that differences exist in the melting behavior of polymers in twin screw extruders (and continuous mixers) when the feed is in a granular form as opposed to a pelletized form. Specifically, small particle melting is influenced by frictional heating while larger particles undergo extensive plastic deformation before melting. These differences also have an impact on energy consumption and melt temperature. The data reported in previous studies were generated on small scale laboratory equipment and it is not clear if and how the reported differences in melting behavior, energy consumption and melt temperature would vary as equipment size increases to those used in commercial scale polymerization facilities.This paper presents results of experiments conducted on a twin rotor continuous mixer (Kobe LCM-100G) using a high density polyethylene resin in a granular form and in a pelletized form. We have also investigated the impact of adding granular material to the pellet feed at various concentrations. Results include temperature profiles in the melting section of the continuous mixer as recorded by strategically located thermocouples as well as overall impact on key process parameters such as energy consumption and melt temperature.

Shrinkage Study of Textile Roller Molded by the Microcellular Injection Process

Shyh-Shin Hwang, Peming P. Hsu, C.-W. Chiang, May 2007

There are several advantages of the microcellular injection molding process. One of the advantages is that the shrinkage of the part can be reduced. This project investigated the effect of the process parameters on the shrinkage of the textile roller. Polybutyleneterephthalate (PBT) materials with 30 wt% glass and Wollastonite fiber were used. The results showed that the shrinkage by microcellular injection molding is less than that of conventional injection molding. Glass fiber filled PBT has more shrinkage than Wollastonite fiber filled PBT due to the non-uniform cell size of the glass fiber filled PBT.

Stress Induced Mixing in Rotor Elements of a Counter-Rotating Continuous Mixier

T. Ishikawa, F. Nagano, T. Kajiwara, May 2007

The numerical approaches we originally developed were applied to the rotor element of a counter-rotating continuous mixer in order to evaluate the mixing performance. Our approaches include the combination of the 3-D FEM based flow analysis and the marker-particle tracking method. The kneading block of a co-rotating twin screw extruder was also investigated in order to contrast the mixing behavior with the rotor.The numerical results showed that the stress induced mixing in rotor elements totally depends upon the process conditions and high rotational speed achieved the uniform mixing. The uniform mixing was expected when the polymer melt underwent narrow stress distribution in the flow channel.The numerical approaches are the effective method to design the process conditions in order to improve the stress induced mixing.

Nitroxide-Mediated Controlled Degradation of Polypropylene

Alexandros Psarreas, Neil McManus, Costas Tzoganakis, Alexander Penlidis, May 2007

The purpose of this work is to evaluate a new polypropylene (PP)–based nitroxyl radical generator (NOR) and offer comparisons with a commonly used peroxide in the production of controlled-rheology polypropylene (CRPP) resins. CRPP resins are produced by reactive processing in a batch mixer by using different amounts of either the NOR or a peroxide initiator at different temperatures. Molecular weight and rheological properties are determined for all CRPP produced and a comparison between the effectiveness of the NOR and the peroxide initiator is provided.

Dynamic Mold Surface Temperature Control for Assisting Injection Molding of Light-Guide Plate and Improving Optical Performance

Shia-Chung Chen, Jen-An Chang, Jin-Chuan Cin, Chun-Feng Yeh, May 2007

During the light guide plate (LGP) injection process, there are challenges in filling the polymer melt completely into a micro-featured geometry. Although a high mold temperature can solve this issue, it also significantly increases the cycle time. Dynamic mold surface temperature control may be implemented to assist LGP injection molding. It was found that when the mold temperature exceeds 140 degrees centigrade, a reasonable accuracy figure can be achieved in micro-feature replication (about 94.66% to 98.22 %). Residual stresses were also reduced and luminance values increased by approximately 33.50% near the light source and by 49.40% further from the source.

Effect of High Mold Temperature and Layout of Gate Position on Conductivity of Composite Polymer Bipolar Plate

Shia-Chung Chen, Min-Yi Shih, Yi-Chang Lin, May 2007

In this study, the feasibility of an injection molded fuel cell bipolar plate for the purposes of lowering costs is evaluated. PC was blended with 4%wt carbon fiber to observe the fiber condition in grooves, and then using PPS blended with carbon fiber as high as 50%wt molded samples. But high contents fiber may have been blocked by the groove and thus led to non-uniform density distribution of fiber and surface conductance. It was found that both gate locations (one being that melt flow parallels the groove (Pa), another being that melt flow is perpendicular to the groove (Pe)) influence conductance. Further, variable mold temperatures were required to assist the melt flow with a high content of fiber and to reduce the fiber-blocking, resulting in better conductivity performance. This improved the resistance by about 60% in PA and 48.89% in PE when using higher mold temperature.

Effect of Injection Molding Parameters on the Electrical Conductivity of Polycarbonate/Carbon Nanotube Nanocomposites

Alexander Chandra, Adam J. Kramschuster, Xiaodong Hu, Lih-Sheng Turng, May 2007

Polycarbonate (PC) was compounded with carbon nanotubes (CNT) using a co-rotating twin screw extruder followed by injection molding. Two 1.8 wt% C/CNT nanocomposites produced from the direct compounding and solution masterbatch approach were injection molded into ASTM D638 standard tensile bars and underwent electrical conductivity measurement in accordance with the ASTM D4496 standard along the flow directions of the tensile bars. It was found that the resulting electrical conductivity was sensitive to injection speed and melt temperature, as well as the location of the injection molded specimens. High electrical conductivities were achieved at high melt temperatures, but high injection speeds resulted in a non-uniform distribution of conductivities across the specimen width. Finally, higher electrical conductivities were found at locations farther away from the gate.

Study on the Optical Performance of Light Guide Plate with Double-Side Micro Feature Design

Shia-Chung Chen, Ching-Hsin Hu, Ming Chang, Wei-Yao Hsu, Li-Chi Su, Ying-Chieh Wang, May 2007

The objective of this study is to manufacture a two-sided micro-feature light guide plate to replace a diffusion plate. First, Trace Pro optical simulation software was used to simulate the micro-feature of the two-sided light guide plate. Then the micro-molding was manufactured, and precision injection experiments were run. Finally, the results of the simulation and the experiments were compared, and the optical simulation results showed that the rightness and uniformity of the light guide plate related to the size and density of the micro-feature. Further, the larger the distance from the sided light source, the closer the size increase and density became. However, the size decreased and the density loosened when the distance from the side light source was decreased. The uniformity achieved 88%. Molding transformation results were the most important factor which influenced the simulation error.

Clusters as a Tool for Companies´ Performance Increasing: A Comparison of Conditions for Establishment and Development of Clusters in the U.S.A, Austria, and the Czech Republic

Drahomira Pavelkova, Roger F. Jones, Eva Jircikova, May 2007

This paper is focused on opportunities for increasing the performance of small and medium-sized companies in the environment of globalization and, particularly, by concentrating production through joining a cluster. Clusters´ establishment and development under different conditions of the U.S., Austrian and Czech economies, and cluster policies are described and discussed. Finally, short case studies of selected clusters with plastic firms established in these countries are presented and conclusions for advantages of clusters existence for companies´ and regional development are given.

Electron Microscopy in Polyethylene Films Research

A. Bobovitch, Y. Nir, G.H. Michler, S. Henning, A. Ajji, Y. Unigovski, E.M. Gutman, May 2007

In the present study morphology of different polyethylene films was shown. The morphology investigation of biaxially oriented linear low density (LLDPE) was investigated by transmission electron microscopy (TEM). The fibrillation of the crystalline phase during biaxial orientation was presented. The influence of crosslinking on polymer crystallization was presented as well. We emphasized that the scanning electron microscopy (SEM) can give sometimes inadequate results if it is used for morphology studies. Atomic forced microscopy (AFM) was shown to be an useful tool studying surface roughness of the blown and cast films.

Study on Pressure Control Device to Improve Foaming Uniformity for the Injection Molding Microcellular Foaming Process

Shia-Chung Chen, Jui-Pin Yang, Yu-Wan Lin, Ping-Shun Hsu, Shih-Sin Hwang, May 2007

In the microcellular foaming process, cell structure and distribution are very difficult to control. This experiment was carried out using the variable geometry mold. We used a cavity pressure control device and a hot nozzle system causing the polymer melt front to flow more steadily. Modification of cell structure and surface flow sink was experimentally verified. The experimental results show that the parts have smaller cell sizes and more uniform cell distribution. The surface reflection increases 10 to 30 % as compared to the traditional process and achieves the optical specification of the backlight module.

Study on Hot Embossing Molding Process and Replication Effects with Different Aspect-Ratio Micro Channels

Shia-Chung Chen, Ying Chang, Ying-Chieh Wang, May 2007

In this study, micro molding via hot embossing was applied to micro channels with different aspect ratios. The micro feature in the Ni-Co based stamp consists of a micro-channel array of approximately 51.56?m in depth and widths of 50?m, 30?m and 15?m, respectively. A PC film of 1 mm thickness was used as a hot embossing substrate. Effects of different aspect ratios and various molding conditions on the replication accuracy of micro channels were investigated. It was found that the accuracies of the micro-channels decreased at increased widths when depth was 51.56?m. Higher embossing temperatures and embossing force led to demolding problems and made the substrate become thinner than 1 ?. However, the molding performance also increased. In sum, higher embossing force and embossing temperatures could lead to higher molding accuracy for micro channels with different aspect ratios.

Study on Microcellular Injection Molded PP/POE and HDPE/POE Composites

Peming P. Hsu, S.P. Liu, S.S. Hwang, Y.J. Lyu, May 2007

This study investigated the effect of the Polyethylene-octene-elastomer (POE) content on the mechanical and thermal properties of PP/POE and HDPE/POE composites by microcellular injection molding. Batches of PP and HDPE with POE content of, 0 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, and 50 wt% for each material were prepared. Nitrogen was used as the blowing agent. DSC was used to study the thermal properties of the samples and SEM was employed to study the microstructure of the fracture surface. The results showed that as POE content increases, tensile strength and flexural modulus decreases. However, as POE content rises, impact strength is increased.

Optimum Design of PET Bottle Bases against Stress Cracking

B. Demirel, F. Daver, E. Kosior, May 2007

Petaloid shaped base for the carbonated soft drink bottles made out of (polyethylene terephthalete) (PET) is quiet common; and there are currently a few bottle designs with slightly different petaloid base in the market. While the petaloid bases provide stability to the bottles; stress cracking of the base during hot climates occurs.In this study, dimensions of the petaloid base against stress cracking are optimized via a FEA software package. Based on the simulation results, a new design for the petaloid base and optimum process conditions for the production of PET bottles are proposed.

Microcellular Injection Molding of PP and PC/ABS with Precision Mold Opening and Gas Counterpressure

Andrzej K. Bledzki, Joanna Kühn, Hendrik Kirschling, Walther Pitscheneder, May 2007

The injection molding of microcellular polymers is expected to be increasable promise for engineering applications. The combined effect of precision mold opening and gas counterpressure process produced uniform microfoam structure with a maximal cell diameter less than 10m /1/. The nature of microcellular PP and PC/ABS was analyzed. It was observed that the mechanical properties, the morphology and the application of microcellular PP were influenced by the degree of crystallinity and the conditions of foaming process. The viscoelastic behavior of materials and their correlation between process, foam structure and properties of PP foam and PC/ABS foam were investigated by DMA.

Smarter Materials Systems Designs for the Future

Clive P. Bosnyak, Alexander Chudnovsky, Shaofu Wu, Hoang T. Pham, May 2007

The term Smart Materials" has been coined to those materials which change behavior when stimulated by light pressure thermal electrical or magnetic fields. Early applications of smart materials are for example electrorheological fluids for clutches and piezoelectric sensors for airbags. The challenge is to create significant additional value to large plastics markets by bringing enhanced functionality through smart materials systems designs. Smart materials systems designs require integration of multidisciplinary skills from materials science through to fabrication and lifetime prediction. Here in this review we address the issues of advancing the technology of polymers into "smarter systems". In particular we identify the needs and challenges to create significant additional value to large plastics markets via smart materials systems designs."

Environmental Stress Cracking in Polycarbonate – Prediction of the Long Term Behavior by the Use of Short Time Tests

Walter Michaeli, Jan Henseler, May 2007

The environmental stress cracking is the most common failure reason of polymer parts during their use. There are already many tests to verify the stress crack resistance. Most methods use combinations of an external strain and aggressive liquids to achieve a quick test result. The extrapolation to longer time periods is only successful with the help of the expert knowledge of the raw material producers. The development of a new testing method enables a simulation of the material long-term behavior on the basis of a short time test of plastics under the influence of a medium.

A New Procedure for Dimensioning Plastics Parts with Similar Consideration of Tensile and Compression Values

Walter Michaeli, Thorsten Krumpholz, Tim Arping, May 2007

Today, the usage of plastics extend also to fields, where they have to stand high compressive loads. Because of the lack of compression values, a technically safe and economically meaningful dimensioning is often a problem. The quantitative comparison of tensile and compression values within the underlying work has shown, that it is possible to calculate the compression behavior from the belonging curves under tensile load with the knowledge of only one compression curve. Further investigations concerning plastics pipes have shown, that the usage of material models, which are calibrated with both values from tensile and also from compression tests leads to a 30% saving of wall thickness.

Curing of Bisphenol M Dicyanate Ester under Nanoscale Constraint

Qingxiu Li, Sindee L. Simon, May 2007

It is well known that the properties of materials are affected by constraint at the nanoscale. Although thermosetting resins have been cured in the presence of nanoparticles and nanotubes, cure of thermosetting resins under the well defined nanoscale constraints imposed by controlled pore glass (CPG) or similar matrices has not been previously documented. In this work, we investigate the isothermal curing of bisphenol M dicyanate ester/polycyanurate under various nanoscale constraints, including in unsilanized controlled pore glass, in silanized controlled pore glass, and within an alumina nanofilter. Differential scanning calorimeter is used to monitor the evolution of the glass transition temperature (Tg) as a function of pore size and pore surface chemistry. Fourier transform infrared spectroscopy (FTIR) is applied to study the degree of cure of polycyanurate in the bulk state and under nanoscale confinement. For the glass transition temperatures of the polycyanurate networks cured in the silanized controlled pore glasses, only the nanoconfinement effect is observed; whereas for the material cured in the unsilanized controlled pore glasses, both the nanoconfinement and surface effects are observed. Furthermore, nanoscale constraint accelerates the cure of bisphenol M dicyanate ester. FTIR study confirms the full conversion of the polycyanurate networks under nanoscale confinement.