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Conference Proceedings

IMPACT OF MOLECULAR BRANCHING ON MICROCELLULAR FOAMING OF POLYLACTIC ACID IN EXTRUSION
Jing Wang , Wenli Zhu , Chul B. Park , Jed Randall, May 2010

Microcellular foams of polylactic acids (PLA) with and without molecular branching were produced on a tandem extrusion system using carbon dioxide as the physical blowing agent. Cell density and expansion ratio were found to be strong functions of the molecular structure the blowing agent content and the processing temperature. Very low density foams were produced with the branched PLA at the optimal processing condition while the linear PLA exhibited severe cell opening beyond a reasonable expansion ratio. Very low crystallinity was detected in the foamed samples indicating that shearing and the presence of supercritical carbon dioxide in the extrusion system did not induce crystal growth.

IMPACT OF MOLECULAR BRANCHING ON MICROCELLULAR FOAMING OF POLYLACTIC ACID IN EXTRUSION
Jing Wang , Wenli Zhu , Chul B. Park , Jed Randall, May 2010

Microcellular foams of polylactic acids (PLA), with and without molecular branching, were produced on a tandem extrusion system using carbon dioxide as the physical blowing agent. Cell density and expansion ratio were found to be strong functions of the molecular structure, the blowing agent content, and the processing temperature. Very low density foams were produced with the branched PLA at the optimal processing condition, while the linear PLA exhibited severe cell opening beyond a reasonable expansion ratio. Very low crystallinity was detected in the foamed samples, indicating that shearing and the presence of supercritical carbon dioxide in the extrusion system did not induce crystal growth.

DEPTH SENSING NANO-INDENTATION TECHNIQUE TO ASSESS DEGRADATION OF WEATHERED POLYMER SURFACES
Lei-Ti Huang, Ping-Shun Hsu, Shia-Chung Che, May 2010

Measurement of surface appearance often fails to predict mechanical failure while bulk mechanical testing confirms failure only after prolonged exposure in weathering. In this study, we attempt to detect small changes in surface mechanical properties during initial stages on the weathered surface of polycarbonate-based materials using surface sensitive nano-indentation technique. Samples were also characterized using various techniques including transmission electron microscopy and infrared spectroscopy. Information on the degradation layer thickness may help in assessing mechanical failure of polymer during early stages. Studies show the superiority of Lexan* SLX resin over polycarbonate in weathering.

THE GENERATION OF THE PTFE POROUS STRUCTURE INDUCED BY UNIAXIAL STRETCHING PROCESS WITH ASYMMETRIC HEATING OPERATION
Lei-Ti Huang , Ping-Shun Hsu , Shia-Chung Che, May 2010

Polytetrafluoroethylene (PTFE) is a remarkable membrane material. Due to its high melting point, PTFE cannot be processed using the conventional melting processing methods. In addition, porous materials have been used in many industrial technologies and life surroundings. Plastic expansion technology has created a new class of filter material, called expanded PTFE (ePTFE). The material comprises a highly fibrillated and porous microstructure that contributes to its excellent filter capability. In this paper, different stretching ratio, asymmetry heating temperature, and different heating time was used to modify the ePTFE membrane pore size. It was found that a longer heating times and lower stretching times, the porosity of PTFE membrane was increased from 30 to 70% and the mean pore size was decreased from 0.22 to 0.08 ?¬m.

WARPAGE MANAGEMENT USING THREE DIMENSIONAL THICKNESS CONTROL METHOD IN INJECTION MOLDING
Yuing Chang , Shih Tsun Huang , Sung-Wei Huang , Shia-Chung Chen , Chao-Tsai Huang , Meng- Chih Chen , Venny Yang, May 2010

Warpage is one of the most crucial problems in injection molding quality control. Since many factors will cause shrinkage and warpage it is very difficult to distinguish which factor always dominates warpage. In this study we have developed Three Dimensional Thickness Control Method (3DTCM) to manage the warpage of the injected parts. Using this method we will specify the geometry of parts with non-uniform three dimensional structures. After integrated with special gate design material selection various operation conditions warpage of injected parts can be managed significantly. Also to verify our results both numerical and experimental investigation will be performed in this study.

WARPAGE MANAGEMENT USING THREE DIMENSIONAL THICKNESS CONTROL METHOD IN INJECTION MOLDING
Yuing Chang , Shih Tsun Huang , Sung-Wei Huang , Shia-Chung Chen , Chao-Tsai Huang , Meng- Chih Chen , Venny Yang, May 2010

Warpage is one of the most crucial problems in injection molding quality control. Since many factors will cause shrinkage and warpage, it is very difficult to distinguish which factor always dominates warpage. In this study, we have developed Three Dimensional Thickness Control Method (3DTCM) to manage the warpage of the injected parts. Using this method, we will specify the geometry of parts with non-uniform three dimensional structures. After integrated with special gate design, material selection, various operation conditions, warpage of injected parts can be managed significantly. Also, to verify our results, both numerical and experimental investigation will be performed in this study.

CYCLE TIME OPTIMIZATION AND PART QUALITY IMPROVEMENT USING NOVEL COOLING CHANNELS IN PLASTIC INJECTION MOULDING
Abul B.M. Saifullah , S. H. Masood , Igor Sbarski, May 2010

Cooling channel design in injection moulding is very important as it greatly affects the cycle time as well as the shrinkage and warpage of the plastic part. Traditionally, cooling channels have been machined into mould components with gun-barrel drilling, with that only straight channels were possible to manufacture. An advanced method of cooling system that 'conforms' to the shape of the part in the mould can be made possible with free form fabrication technique such as DMD (direct metal deposition). This paper presents an investigation on the optimization of mould design of conformal cooling channels of different cross sections for plastic injection moulding. Comparative study has been done with the conventional straight cooling channels. ANSYS thermal simulation software has been used to get comparative temperature profile on the mould and Moldflow simulation software has been used to compare shrinkage, warpage and temperature profile of the part itself during moulding process . Comparative results are presented based on temperature distribution and cooling time for the mould and warpage deflection, volumetric shrinkage and temperature profile of the part. The results provide a uniform temperature distribution with reduced shrinkage and warpage and reduction in cycle time for the plastic part.

PACLITAXEL ATTACHMENT TO PLA-PHA BLEND FILMS
Courtney J. Taylor, May 2010

The overall objective of this research was to prepare paclitaxel-delivering poly(L-lactic acid) (PLA) - poly(hydroxyalkanoate) (PHA) blend films, focusing on drug attachment to the films. Blend films (10 wt% PHA) were melt extruded using a single screw extruder. A sequential two step photografting approach was used to photograft poly(acrylic acid) (PAA) to the film surface. Acid groups from PAA were then reacted with a specific – OH group on paclitaxel using water soluble carbodiimide chemistry. To assess the extent of drug attachment, the resultant films were characterized using ATR-FTIR spectroscopy.

DYNAMIC MOLD SURFACE TEMPERATURE CONTROL FOR MOLDING HIGH GLOSS, PAINTING FREE PART SURFACE ACHIEVING CYCLE TIME AND COST REDUCTION
Shia-Chung Chen , Jen-An Chang , Jin-Chuan Cin, May 2010

The study shows the molding of a high gloss surface notebook computer (NB) display support without painting using dynamic mold temperature control. The required mass production rate is 300,000 pieces per month. Both water heating/cooling and induction heating/water cooling were employed to investigate the cycle time, mold and machine requirements. The former requires 60s cycle time whereas the later needs only 36s to achieve a weld line free surface. The associated cost reduction in energy consumption is US $23,700 per month, injection machine operation is US $52,800 per month, mold making cost is US $75,000 and painting cost saving is US $190,500. Annual savings could reach US $3,237,900.

A DIMENSIONAL ANALYSIS OF VISCOUS HEATING IN RUNNER SYSTEMS USING THE RADIAL FUNCTIONS METHOD
William M. Aquite, Iván D. López, Tim A. Osswald, May 2010

Polymer flow through circular tubes is a common occurrence in injection molding runner systems. Viscous dissipation affects the temperature distribution of the melt as it enters the cavity. The Radial Functions Method was used to model the flow and heat transfer inside runner systems in dimensionless form. Temperature increases are obtained from simple expressions as a function of the dimensionless Brinkman and Graetz numbers. This eliminates the necessity of simulation or experimental test of such flows when predicting temperature increments as a function of processing conditions.

EVALUATION OF THE CRACK INITIATION CHARACTERISTICS OF PIPE GRADE POLYETHYLENE UNDER FATIGUE LOADS
Jing Wang, John W. S. Lee, Jae D. Yoon, Chul B. Park, May 2010

Recently, a circular notched specimen (CNS) is selected for studying the crack initiation characteristics of pipe grade polyethylene as a part of understanding quasibrittle failure. In this study, four types of pipe grade polyethylene were chosen and tested under variable fatigue loading conditions using CNS with various notch depths. The fatigue characteristics of four polyethylenes were evaluated, and the fracture surface of CNS after failure is analyzed by optical microscope and scanning electron microscope (SEM) to evaluate the fracture mechanism of pipe grade polyethylenes. In addition, the technical issues with CNS during tests were also investigated by finite element analysis.

CHALLENGE TO THE FOAMING OF A THIN-WALL INJECTION MOLDED PART- INFLUENCE OF INJECTION SPEED AND GATE GEOMETRY
Jing Wang , John W. S. Lee , Jae D. Yoon , Chul B. Park, May 2010

Foaming of a thin-wall part during injection molding is challenging. Cell nucleation and growth are significantly constrained by rapid cooling from the mold by limited cavity space and by high mold cavity pressure generated by the viscous polymer melt. In this paper we study the influence of injection speed and gate geometry on the cell size uniformity and void fraction control of a foamed thinwall part. Real-time mold cavity pressures were recorded using pressure transducers and a computer system. It was found that high injection speed and proper gate design can minimize cooling from the mold maximize shear thinning at the gate and thus making possible uniform foaming throughout the part volume.

POLYMER-GRAPHITE AND POLYMER-CARBON NANOTUBE NANOCOMPOSITES:PROCESSING VIA SOLID-STATE SHEAR PULVERIZATION
Jun’ichi Mausda , Katsuyuki Wakabayashi , Philip J. Brunner , John M. Torkelson, May 2010

A continuous, industrially scalable process method called solid-state shear pulverization is shown to be effective in producing well-dispersed polypropylene/ carbon nanotube and polypropylene/ as-received graphite nanocomposites that cannot be obtained by conventional melt processing alone. Major improvements in Young's modulus (> 100% increase) and yield strength (65% increase) are obtained in the nanocomposites made by SSSP, with the maximum increases being observed in samples containing the highest concentrations of nanofiller that are well-dispersed. In contrast, electrical conductivity is correlated to dispersion of carbon-based nanofiller in a different manner, with conductivity increasing with increasing nanofiller content even when an increase in nanofiller content results in less effective dispersion or exfoliation.

POLYLACTIDE COMPOSITES FILLED WITH MICROCRYSTALLINE CELLULOSE, NANOCRYSTALLINE CELLULOSE AND CELLULOSE NANOFIBERS
Karen Stoeffler , Minh-Tan Ton-That , Johanne Denault , John Luong , Crystal Wu , Mohini Sain, May 2010

Polylactide (PLA) nanocomposites based on microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC) and cellulose nanofibers (CNF) were prepared in the molten state by microextrusion. The dispersion was investigated by optical and electron microscopy. The mechanical properties of the nanocomposites were analyzed by dynamic mechanical analysis (DMA). The thermal properties were analyzed by differential scanning calorimetry (DSC). The effect of the addition of a proper coupling agent on dispersion and mechanical properties was analyzed.

MORPHOLOGY DEVELOPMENT IN THE PELLET DURING COMPOUNDING OF RECYCLED POLY(ETHYLENE TEREPHTHALATE) (RPET)/POLYPROPYLENE (PP) BLENDS
H. Inoya , Y. W. Leong , S. Thumsorn , S. Thitithanasarn , H. Hamada, May 2010

The morphology of RPET and PP pellets has been shown to have a profound effect on the properties of injection moldings. The size of PP dispersed phase is critical as it dictates the ductility of the blend. It has been shown that the size of a dispersed phase could grow by either coalescence or relaxation during and immediately after extrusion where temperatures are high. This study focuses on the chronological development of PP dispersed phase throughout the extrusion line during RPET/PP blending prior to pelletizing. The effect of compatibilizer content will be correlated to the growth rate of PP phase and also on the mechanical properties of subsequent injection moldings.

ASSESSING AND IMPROVING NANOMATERIALS HANDLING IN EXTRUSION
Michael J. Molitor, Mark Weinberg, Mark D. Wetzel, May 2010

The compounding of polymer nanocomposites involves the handling, feeding and cleaning of high volumes of potentially low bulk density powders. The Nanorisk Framework document [1] guides practitioners in how to assess the effectiveness of operations and engineering controls designed to contain nanomaterials and minimize the risk of exposure or environmental release. This paper reviews a new approach for measuring and evaluating the effectiveness of engineering controls and operating procedures when feeding nanofiller powders into a compounding extruder. A method will be described that uses the extruder itself as an effective means to reduce dust generation from the feed system.

CONTRASTING DEFORMATIONAL CHARACTERISTICS BETWEEN LAMELLAR AND CYLINDRICALLY PHASE SEPARATED TPES
Mohit Mamodia , Alan J. Lesser, May 2010

In this study we investigate and compare the deformation behavior of SEBS triblock copolymers with lamellar and cylindrical morphology. Structural changes that occur at various length scales have been studied using a simultaneous small- and wide-angle X-ray diffraction (SAXD/WAXD) technique during uni-axial tensile deformation. Further deformation calorimetry is used to investigate the energetics involved during the deformation of these materials. Series of results from these various techniques indicate that the deformation takes place in three stages.

IN SITU PRODUCTION OF SLIGHTLY BRANCHED POLY(ETHYLENE TEREPHTHALATE) BY SOLID-STATE SHEAR PULVERIZATION: A POTENTIAL SOLUTION TO IMPROVED RECYCLABILITY AND SUSTAINABILITY
Cynthia Pierre , John M. Torkelson, May 2010

Using solid-state shear pulverization (SSSP) to process poly(ethylene terephthalate) (PET) without addition of chemical agents, we demonstrate that linear PET can be transformed into lightly branched PET, with resulting improvements in physical and mechanical properties. Rheological characterization demonstrates an increase in the melt viscosity of the pulverized PET while intrinsic viscosity characterization yields data consistent with no increase in linear chain length. These results indicate that branching occurs in situ during SSSP via mechanochemistry involving the production of polymeric radicals that result from low levels of chain scission accompanying SSSP. A hypothetical mechanism for this mechanochemical transformation is discussed. The lightly branched PET resulting from SSSP yields a dramatic increase in the crystallization rate of the PET, improving its processability. The ability to increase the melt viscosity of PET by SSSP may contribute to sustainable engineering of PET; a long-standing issue with recycling PET for high-value applications is the fact that melt processingof PET results in reduction of molecular weight and thereby melt viscosity, making the recycled material often unusable for the original application for which it was made.

A NEW METHOD FOR CONTROLLING THE BARREL TEMPERATURE IN AN INJECTION MOLDING MACHINE
Meaghan Charest, Jose Mauricio Hernandez, Rickey Dubay, May 2010

A new method of obtaining open loop responses of a three barrel injection moulding machine is investigated. The method involves limiting the amount of heat transfer between adjacent zones by using a controller to create an artificial adiabatic wall. Since most barrel zones are run at or near to the same temperature, the system identified by the adiabatic wall method better represents industrial operating conditions. A predictive controller was designed to handle the dynamics of the adiabatic system and compared to a conventionally-tuned controller

PROCESS MONITORING AND CONTROL FOR MICROCELLULAR INJECTION MOLDING
Dana Hnidáková, Roman Cermák, Jana Výchopnová, May 2010

The current study tests cavity pressure sensors and in-mold temperature sensors to determine their effectiveness for the process monitoring of microcellular foam injection molding. Piezoelectric pressure transducers were placed behind ejector pins. Exposed junction, microbead thermocouples were installed in the ends of ejector pins, with direct exposure to the melt. Sensors were located near the gate and near the end of fill in a two cavity production mold. Cavity pressure and melt temperature profiles, peak pressures and peak melt temperatures at each position were logged as well as the time to reach these peak values. These process data were then analyzed relative to part weights and part dimensions.










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