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
Degradation of PBSA in Water
Douglas Hirt, Mary Mitchell, Treyton Ryder, May 2017
The degradation of poly(butylene succinate-co-adipate) (PBSA), a biodegradable polyester that can be made from renewable feed stocks, was investigated in this work. PBSA-starch-furfural blends of up to 20 wt% corn starch and up to 15 wt% furfural were made to determine if these systems could be used to deliver a control amount of furfural, a known nematicide, for agricultural applications. The PBSA-starch-furfural blends were aged in distilled water for up to 30 days. There was only a slight downward trend in molecular weight of the PBSA and PBSA-starch blends over the 30-day aging period. Changes in the total weight of samples and the concentration of furfural in the water surrounding the pellets indicated that furfural was quickly released from the pellets and a total furfural release of 92% was achieved by day 10 of degradation.
Optimization of the Devolatilization Process in the Injection Molding Cylinder
Yuki Hisakura, Hisakura Yuuki, Kawakubo Mitsuhiro, Kitahara Kenichi, Sugihara Makoto, Hamada Hiroyuki, May 2017
In the recent years, many of the past demerits and all vent up problems that the past vent-type injection molding machines had were solved, so such a vent-type injection molding machine is being focused. However, the plasticization process of vent-type molding is not solved theoretically and systematically. In order to use a vent-type molding widely in the future, the technology needs to be built systematically by theoretical break-through of the devolatilization of gas and moisture, and by studying the influence on the molding materials. In our study, PA6 materials with dry pellets and water absorption pellets were molded by the normal barrel and the vent barrel injection molding. The systematic construction of the technology studied by grasping injection molding parameters which would influence the devolatilization of gas and moisture in the cylinder during the plasticization process for the vent-type molding by the system optimizations using Quality engineering .
Sterilization Effects on the Mechanical Properties of Laser-Welded Polymer Specimens of Polypropylene and Polycarbonate
Kai Holl, Thomas Seul, May 2017
Microorganisms on components need to be removed through sterilization in order to ensure the safe use of medical products for patients. Therefore, polymer parts are typically treated with gamma radiation, ethylene oxide or superheated steam; such treatment may result in a modified structure or the degradation of the polymer. The present paper shall demonstrate how the mechanical properties of test specimens and welded samples of polypropylene and polycarbonate change during the sterilization procedure. The resulting changes in the structure and the degradation respectively will be analyzed by Fourier transform infrared spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC) and structural property relationships shall be derived. The analyses showed that the changes in the mechanical properties depend on the sample, the sterilization procedure and the corresponding polymer; and that those changes must be considered when designing the respective products.
Bonding of Plastic Parts with Dispersion Adhesives – Film Formation via Diffusion Processes
Matthias Hopp, Elmar Moritzer, May 2017
Bonding of plastic parts poses some challenges e.g. regarding wettability, adhesion or the choice of a suitable adhesive system. Often cost-intensive, chemically setting adhesives such as epoxy resin adhesives are used. In the furniture and paper industries, porous materials such as wood or paper are bonded with dispersion adhesives which are regarded as ecologically friendly and, due to the high water content, are cost-effective. In the context of combining wood and plastic, for example with WPC (Wood-Plastic Composites), hybrid joints of wood/WPC or wood/plastics are becoming more and more important for industrial applications. The investigations in this paper show a possibility to bond non-hygroscopic parts with dispersion adhesives. Through perforation of one bonding partner, the water in the wet adhesive can be removed from the adhesive layer. The process of film formation is analyzed considering diffusion processes, capillary forces and deformation of the particles.
A Basic Experimental Study of Cast Film Extrusion Process for Fabrication of Plastic Microlens Array Device
Yi Min Hsieh, Chih-Yuan Chang, Xuan-Hao Hsu, May 2017
This paper reports a highly effective method for fabrication of plastic microlens array device based on a cast film extrusion process. In this method, a thin steel mold with a micro-circular hole array pattern is fabricated by photolithography, and a wet chemical etching process. The thin steel mold was then wrapped onto a metal cylinder to form an embossing roller mold. During the cast film extrusion process operation, the molten polymer film was extruded and immediately pressed against the surface of the embossing roller mold. Under the proper processing conditions, the molten polymer will just partially fill the micro-circular holes in the mold and due to surface tension form a convex lens surface. A continuous plastic film with a microlens array pattern was fabricated. This technique shows great potential for the mass production of large-area plastic microlens array device with high productivity and low cost.
Optimizing the Warpage of Injection Molding Parts Using 3D Volume Shrinkage Compensation Method
Chao-Tsai Huang, Cherng-Jyi Yeh, Gwo-Geng Lin, Wen-Ren Jong, May 2017
Injection molding has been applied to manufacturing for various products for years. However, due to the requirement of high precision for modern products, the product development is still very challenge. Conventionally, people used to utilize the packing pressure technology (either enlarge packing pressure or extend the packing time) to enhance the dimension quality, but it is not always useful. In this study, first we have applied Computer-aided Engineering (CAE) technology to analyze why the conventional packing pressure is not always effectively. The reason is that the compiled injection system with different thickness along the product will cause non-uniform shrinkage all the time. It is not easy to compensate using packing pressure skill. Furthermore, we have applied 3D volume shrinkage compensation method (3DVSCM) to reduce the warpage defect based on a mobile phone benchmark. Results show that through various packing pressure operations the dimension deviations at different regions can be compensated simultaneously. It is also verified under various operation conditions, such as different injection times, melting temperatures, mold temperatures, and so on. The modification is always so effectively. That means the high dimension quality demand is possible obtained utilizing 3DVSCM under suitable process condition setting.
Online Measurement of Polymer Melt Viscosity in Injection Molding
Ming-Shyan Huang, Shih-Chih Nian, Jian-Yu Chen, Kai-Jye Yang, Jian-Chou Tseng, May 2017
Melt viscosity, determined by the shear rate, barrel temperatures, and pressure during plasticization, greatly affects the flow ability of polymer melts as well as the quality of injection-molded parts. In particular, the consistency of molding qualities is highly relevant to the plasticizing quality at each cycle (i.e., injection molding requiring a high yield rate highly relies on the stability of polymer melts). However, numerous factors affect the plasticizing quality, including the geometry of injection screws, processed polymer materials, processing parameters of plasticization such as the feeding rate, screw rotational speed, barrel temperatures, back pressure, and screw backward speed. The conventional approach of plasticization in injection molding machines uses a single reciprocating screw for conveying, melting, and metering polymer melts. The plasticizing quality is roughly adjusted by indirectly controlling barrel temperatures; thus, the melt viscosity varies. An in-suit approach of assuring melt quality is to measure the melt viscosity variation online, which is a more suitable indicator of the plasticizing quality than temperature. This study thus monitored the melt viscosity variations in polymer melts by using in-mold pressure sensors. Furthermore, the effects of the injection velocity and mold temperature on the melt viscosity variations were examined.
The Different Viscosity Arrangement Effects on the Variation of Interface between Skin and Core in Co-Injection Molding
Chao-Tsai Huang, Cheng-Huang Chen, Kuan-Hao Chen, Gwo-Geng Lin, Chih-Chung Hsu, Rong-Yeu Chang, Shi-Chang Tseng, May 2017
Co-injection molding, one of the multi-component molding methods, is commonly used in our daily life product. However, there are too many combinations of designs and parameters, how to properly control of co-injection is very challenge. Furthermore, co-injection with multi-cavity system is still not fully understood yet. In this study, we have focused on a nonsymmetrical multi-cavity system. First, we tried to find out how the different viscosity arrangement effects on the variation of the interface between skin and core layers in co-injection molding. Specifically, we have assigned three types of material arrangements, say A/A (low viscosity-to-low viscosity), A/B (low viscosity-to-high viscosity), and B/A (high viscosity-to-low viscosity). In A/A system, with a unique skin-to-core ratio and a fixed flow rate, general operation parameters have no significant effect on the change of the interface between skin and core. In A/B system, it generates longer and narrower locus than that of A/A system. It might be due to the higher viscous core material has higher inertia force to push in flow direction. On the other hand, in B/A system, it generates shorter and wider locus than that of A/A system. It might be due to less viscos core material has lower inertia force to push core melt in perpendicular to flow direction. Moreover, in the presence of flow rate variation, as flow rate increased, the penetration distance of interface between the skin and core is reduced for A/A system. This reduction phenomenon on the penetration distance of the interface is also observed in A/B and B/A systems. Finally, the experimental study is also performed to verify the numerical predictions on the different viscosity arrangement effects. Specifically, in the presence of flow rate variation, the numerical prediction on the interface between the skin and core is in a good agreement with the experimental data in trend.
Study on the Micro-structures of Long Fiber through Runner and Cavity in Injection Molding for Reinforced Thermoplastics (FRT)
Chao-Tsai Huang, Xiang-Lan Peng, Sheng-Jye Hwang, Huan-Chang Tseng, Rong-Yeu Chang, May 2017
Lightweight technology has been applied into many industries especially for automotive to enhance the fuel efficiency. One of most famous methods is applied fiberreinforced thermoplastics (FRT) technology, it includes short and long fiber-reinforced thermoplastics (FRT) to support lightweight technology. However, the enhancement mechanism by the microstructures of the fibers in FRT is still too complicated to understand. In this study, we designed a benchmark to study the fiber microstructures based on ASTM D638 with dog-bond system. First, we have tried to study how the geometry of cavity influences the fiber orientation during the injection processes. Furthermore, we have paid the attention on the variation of the fiber length distribution as the injection molding processing. Results show that the geometry of cavity has significant effect on the fiber orientation during the injection processes. Since the system has contraction and expansion structure, the orientation tensor component a11 corresponding to the flow direction, will be enhanced and then decreased along the cavity. Moreover, the fiber lengths have dramatically sharp distribution on skin layer when melt goes through the gate into the cavity. It will allow almost 90% lengths are broken through the skin layer. Meanwhile, using numerical visualization from runner to cavity through core layer, there is about 30% length broken during the journey in runner section. Finally, some fiber orientation results are compared with some literature’s. Results showed that our numerical predictions are matched with that of literature quite well in the trend.
Effect of Ethylene Content on Maleic Anhydride-Grafted Polypropylene Based Block Copolymers
Wenyi Huang, Parvinder Walia, Yushan Hu, Zhe Zhou, Nicholas Horstman, Tianzi Huang, May 2017
This paper reports an alternative approach by incorporating ethylene segments into polypropylene backbone, that is, ethylene propylene (EP)/isotactic polypropylene (iPP) block copolymers, to mitigate the chain scission issue during the free radical initiated maleic anhydride (MAH)-grafting reactive extrusion of polypropylene. 13C-labeled MAH was used to study chemoselectivity by 13C Nuclear Magnetic Resonance (NMR) spectroscopy. Results showed that MAH was selectively grafted onto ethylene sites of copolymers. The MAH-grafting reactive extrusion conducted on a 25-mm twin-screw extruder indicated that increasing ethylene contents in EP/iPP block copolymers from 15 wt% to 46 wt% not only significantly improved MAH-grafting efficiency but also dramatically reduced the molecular weight degradation and low molecular weight fraction in the resultant functionalized polymers. This method can be also leveraged to other free radical-based functional polypropylenes.
Preparation of Three-Dimensional Poly(e-Caprolactone) Porous Tissue Engineering Scaffolds by a Combination of Microcellular Injection Foaming and Polymer Leaching
AN HUANG, Xiang-Fang Peng, Lih-Sheng Turng, May 2017
Three-dimensional (3D) interconnected porous poly (e-caprolactone) (PCL) scaffolds with desirable pore sizes and porosities have been prepared by utilizing both microcellular injection foaming and polymer leaching techniques. The incorporation of water-soluble poly(ethylene oxide) (PEO) served as a porogen to improve the porosity and interconnectivity. Highly oriented and elongated pore structures were obtained from the scaffolds via microcellular injection foaming. It was found that the pore diameter variety and the porosity increased with PEO. The compression modulus of the porous PCL scaffold decreased from 68.2 MPa for neat PCL to 46.7 MPa for 50%PCL (i.e., 50%PCL/50%PEO blend by volume) with an increase in porosity, which may render these scaffolds suitable for a variety of medical and tissue engineering applications. 3T3 fibroblast cell culture was performed to confirm the biocompatibility and cell viability of the scaffolds, which revealed that the cells proliferated the best on the 50% PCL scaffolds, as compared to the other three scaffolds, due to the more elongated and spindle-shaped pore structures, indicating favorable cell–scaffold interactions. Therefore, this novel method offers an effective means for scalable fabrication of tissue engineering scaffolds.
Research and Application of Gas Counter Pressure Technique to the Strength of Co-Injection Molding
Yan-Mao Huang, Wen-Ren Jong, Chi-Hung Kao, Chien-Chou Wu, De-Wei Liu, Shyh-Shin Hwang, May 2017
With people’s daily life full of various plastic products, many molding technologies are developed in order to reduce production cost, increase product strength, improve product appearance, and adhere to environmental protection. Co-injection molding is also known as sandwich molding, producing composite plastic products with a multilayer structure through one injection procedure. Most manufacturers use secondary recycled material or high strength plastics as the core material to reduce material cost and increase product strength or utilizes an appropriate proportion of materials to improve product strength and surface quality. This study employs the GCP(Gas Counter Pressure) technique in the co-injection molding process to increase product strength. As co-injection molding has two flow front behaviors of melt, the skin layer thickness distribution and core penetration length are difficult control, and the fountain flow effect results in an unstable injection of core melt. Therefore, the gas counter pressure technique in co-injection molding can inhibit the flow front behavior. This study discusses the effect of the gas counter pressure technique on core penetration and mechanical strength as well as the effect of penetration length and penetration section of core melt on mechanical strength under different gas counter pressure intensities. The experimental results show that the gas counter pressure mechanism enhances core material penetration stability, changes the penetration length and penetration section of core material, and effectively enhances the end product strength.
Exploration of Annealing Effect on Pore Formation of Polyethylene Films
Wenyi Huang, Brian Landes, Yijian Lin, Joe Deavenport, Jackie deGroot, May 2017
This paper reports the exploration of annealing effect on the pore formation of semicrystalline homopolymer, polyethylene (PE) films. Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and wideangle X-ray diffraction (WAXD) techniques were used to gain fundamental understanding of the change in the crystalline structure of a PE film during the annealing process. Mercury porosimetry was employed to characterize the pore structure of PE porous films under different annealing conditions. The result showed that annealing was critical for the pore formation in PE films. Longer annealing time not only resulted in larger crystalline lamellae and higher crystallinity, but also promoted the pore formation leading to larger porosity and pore size in PE films. Porous films with 49.5% porosity and an average pore size of 96.5 nm were achieved when the annealing time was 24 hours.
Synthesis and Characterization of Microcellular Injection and Injection-Compression Molded PPgMA/Graphene Nanocomposites
Shyh-shin Hwang, Jui-Pin Yang, Ching-hsin Hu, Peiming Hsu, May 2017
Maleated polypropylene (PPgMA) and Graphene (GP) nanocomposites were prepared directly by microcellular injection and injection-compression molding. Synthesized PPgMA/GP nanocomposite dispersion morphology was confirmed by X-ray diffraction (XRD) and Transmission Electron Microscope (TEM) analysis. Thermo-mechanical and electric properties of PPgMA/GP composites were also reported. Furthermore, electromagnetic interference (EMI) shielding effectiveness was investigated by injection molding (IM), foamed injection molding (FIM), injectioncompression molding (ICM), and foamed injection compression molding (FICM) methods.
Linear and Nonlinear Behavior on PP/CNT Composites Prepared by Continuous Ultrasonic Twin-Screw Extrusion
Avraam I. Isayev, Jing Zhong, Tian Liang, May 2017
PP/CNT nanocomposites of various concentrations are prepared using ultrasonic aided extrusion without and with ultrasonic treatment to achieve different CNT dispersion levels. The linear and nonlinear rheological behaviors of these nanocomposites are studied using small and large amplitude oscillatory flow (SAOS and LAOS) start-up shear flow and step-strain relaxation. The improved dispersion of CNTs by ultrasonic treatment is found to increase the shear stress level at different shear rates. The relaxation modulus of PP/1wt%CNT composites is found to be lower at low strains, than that at high strains, due to the instability of the filler network. LAOS results of PP and PP/1wt%CNT composites indicate that the elastic and viscous Lissajous curves are ellipses. In contrast, for PP/3wt%CNT and PP/5wt%CNT composites at high strain amplitudes the shape of the Lissajous curves are distorted, as a result of the nonlinearity. The intensity of the third harmonic increases with the strain amplitude and CNT concentration. Ultrasonic treatment of PP/CNT nanocomposites, leading to an improved CNT dispersion, further enhances the nonlinear behavior. At low CNT concentrations, values of G’ and G’’ decrease with the strain amplitude, but at high concentrations a value of G’’ exhibits a maximum with the strain amplitude. Chebyshev polynomials are used to decompose the elastic and viscous stresses. At high strain amplitudes, both the elastic and viscous stresses exhibit a nonlinear behavior. All the PP/CNT composites exhibit a strain-stiffening behavior. The ratio of viscous contribution v3/v1shows a peak with increasing of strain amplitude, meaning that the intra-cycle shear thickening followed by intra-cycle shear-thinning behavior with the strain amplitude. These intra-cycle nonlinear behaviors are increased with the increase of CNT concentration and enhanced by the ultrasonic treatment.
Vibration Assisted Injection Molding of Poly(lactic Acid) - Thermal, Spectroscopic, and Mechanical Analysis of Hydrolytic Degradation
Israd Jaafar, Qi Li, Raymond A. Pearson, Gabby Esposito, Sabrina S. Jedlicka, John P. Coulter, May 2017
Hydrolytic degradation of PLA was studied, and a comparison was made between samples molded using vibration-assisted injection molding (VAIM) technology and those through conventional injection molding. Data from an earlier study is revisited to observe hydrolytic degradation effects by analyzing thermal, spectroscopic, molecular weight, and tensile strength trends. The trends show that degradation causes an apparent decrease in crystal order, reduction in molecular chain length and weight. Comparison between molding cases shows that VAIM results in a relatively higher strength of molded PLA, with apparently a more ordered crystal structure. It is interesting to note however that comparison in data trends as degradation of the samples proceeds throughout the study does not show any significant differences between VAIM and conventionally molded PLA, especially in terms of changes in thermal and spectroscopic data.
Simulation Methodology for Large Part Processing Using 2-Shot Injection Compression Molding (2K-ICM)
Raghavendra Janiwarad, Bhaskar Patham, Harindranath Sharma, Ruud Heerkens, May 2017
Large body panels, side air deflectors of trucks, panoramic sunroofs, rear quarter windows, TV back panels, housings, bumpers, backlights and tailgates are examples of large parts with higher surface area. If conventional injection molding (CIM or IM) is used to produce such parts, it requires very large pressure and clamp force, which may not be practically possible. In addition, part stress levels will be higher. To overcome these issues, 2-shot Injection- Compression molding (2K-ICM) an advanced molding technology is used, which results in lower residual stresses in the part and significant reduction in clamp forces while molding such large parts. A single-part solution is possible through the 2K-ICM process. With that said, for quicker adoption of this technology, it would be ideal to develop a fully validated simulation framework for 2K-ICM process so as to enable machine and grade selection, mold design, as well as optimization of processing parameters in a reliable manner, while minimizing or eliminating experimental trial and error. The specific objective of this work is to demonstrate the novel simulation framework for 2K-ICM developed using Moldex3D† software, and capture the key phenomenological aspects of the process in the context of a model ribbed geometry. In the simulation study, the thermal history of the first shot is interlinked with the second shot by Multi-Component Molding (MCM). This interlinking of results effectively captures the thermal gradients and differential cooling rates at cross section of rib area; such information would be critical to understand the impact of processing and geometry on development of defects on surface. This framework will aid in optimization of the design for 2K-ICM parts and evaluation of its performance in a realistic manner.
A New Method to Characterize Environmental Stress Cracking Resistance (ESCR) of Polyethylene Pipes
Ben Jar, Patrick Ward, Chester Jar, Yi Zhang, Wajdy Ateerah, May 2017
A new test method has been developed to evaluate environmental stress cracking resistance (ESCR) for polyethylene (PE). The new test method applies transverse loading to the central area of a plate specimen, to generate local stretch that results in a truncated cone. Time for crack initiation in the truncated cone, during the exposure to an aggressive agent (10% Igepal CO-630 solution), is used to characterize ESCR. Results from the new test method are consistent with those from ASTM D1693, but the former does not require any pre-notch and takes less than 3% of the time required for the latter. Based on the new test method, a stand-alone device has been developed to characterize ESCR, which uses change in electrical conductivity to measure the time for the crack development. The device is compact and easy to operate. Using this device, time for crack initiation can be determined automatically and accurately without the use of a commercial test machine.
Induction of Mesenchymal Stem Cells (MSC) Differentiation to Endothelial Cells via Scaffold Stiffness Modulation
Yong-Chao Jiang, Ming-Song Lee, Qian Li, Wan-Ju Li, Lih-Sheng Turng, May 2017
Insufficient endothelial cell (EC) sources and angiogenesis abilities are still limiting factors of tissue engineering, whether in blood vessel reconstruction or large organ regeneration. The study of pathology has revealed that cardiovascular disease and preceding vascular dysfunction result in vascular calcifications and concomitant arterial stiffness, therefore making the host release high amounts of circulating macrophage migration inhibitory factor (MIF). MIF can promote stem cell assembly, self-proliferation, and differentiation to endothelial cells to accomplish pathological site repair, suggesting the feasibility of adjusting the endothelial cell differentiation degree via modulating the amount of MIF. In this study, fibrous scaffolds were produced by electrospinning, then an annealing treatment was used to alter the scaffold stiffness without changing the scaffold structure or chemical groups. Interestingly, mesenchymal stem cells (MSC) showed higher proliferation rates and higher endothelial cell differentiation potential on stiffer scaffolds modulated via higher MIF levels.
Predicting Short Fiber Composite Material Distribution and Orientation Using Optimization for Additive Manufacturing Applications
Delin Jiang, D.E. Smith, May 2017
Fused Deposition Modeling (FDM) is one of the most popular Additive Manufacturing (AM) techniques in the market. Recent development of blending short fibers with polymer filament for print application has shown mechanical property improvement in the printed parts. Furthermore, large scale 3D printing has demonstrated the potential of moving this technology from hobbyist usage to industrial manufacturing. As the use of this technology becomes more widespread, it is important to have a predictive tool that aids in the design of structures for optimal material distribution and fiber orientation. This paper presents a three dimensional (3D) topology optimization method for FDM application, and the method solves the statically load structure for minimum compliance.
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