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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Rheology of Carbon Nanofiber-Modified Thermotropic Liquid Crystalline Polymers
A series of carbon nanofiber-modified thermotropic liquid crystalline polymers (TLCP, Vectran V400P) were investigated for their rheological properties. Steady shear viscosity at 250 °C revealed that incorporation of nanofibers led to a higher steady shear viscosity and a narrowed plateau region, implying a different microstructure for TLCP composites from that of a pure TLCP. Complex viscosity increased with increasing CNF content (0 ~ 15 wt%) for all frequencies at 230 °C. Shear thinning behavior in complex viscosity plot was observed for pure TLCP and all composites; there was no plateau in the dynamic viscosity even for a pure TLCP, indicating that this TLCP does not obey Cox-Merz rule. In a G? versus G ? plot, the slope for pure TLCP was different from those of composites.
CAE Prediction of Ink Wash-Out on Phone Keypad for In-Mold Decoration
This article investigates the ink that using for in-mold decoration project washes out during production. The material for film and resin is polycarbonate. The average thickness of keypad of mobile phone is 0.7 mm. The printed ink on the film washes out due to the shear stress of plastic flowing. Therefore, the shear stresses of gates in balanced and unbalanced runner system are investigated by the results of CAE simulation. Furthermore, a mold of keypad was used to investigate the phenomena of ink wash-out and to compare with the results of CAE analysis.
Influence of the Coupling Agent on Polypropylene/Clay Nanocomposite based Wood-Plastic Composites
In this study, wood-plastic composites (WPCs) were made by compounding 50 wt% wood flour with 50 wt% of a matrix material composed of a polypropylene (PP)/clay-based nanocomposite using a co-rotating twin-screw extruder. Polymer nanocomposite (PNC) pellets, having varying percentages of clay, were first made by employing a PP/clay master batch. These pellets were then compounded with the wood flour and different percentages of polypropylene grafted with maleic anhydride (PP-g-MA) that acts as coupling agent between wood and PP. WPC pellets were finally injection molded into a variety of test specimens whose mechanical properties and rate of water absorption were measured and whose fracture surfaces were examined with the help of a scanning electron microscope (SEM). Results were compared with WPCs containing additional wood flour but no clay. It was found that the addition of clay to PP enhanced the modulus of both the base polymer and the injection-molded WPCs. Results of water absorption tests indicated a reduction in the initial rate of water uptake when 4 wt% of clay was used in the WPC matrix.
Organosilane Modification of Montmorillonite Clay: Characterization and its Influence on the Properties of Polyvinyl Alcohol Nanocomposite
Montmorillonite clay has been treated with various concentrations of 3-aminopropyltriethoxysilane in various solvents such as water, tetrahydrofuran and toluene. Intercalation of aminosilanes between the clay layers have been confirmed from the increase in the average dspacing obtained from X-ray diffraction (XRD). The two peaks observed in the x-ray diffraction results of clay modified with organosilanes in the water medium confirms the intercalation of amino silane as well as the tactoid formation due to the surface interaction of the surface –OH groups with water. Presence of organosilanes in modified clays has been further confirmed from the –CH asymmetric and symmetric stretching of >CH2 groups at 2920 and at 2855 cm-1. The amount of exchanged cations between organosilanes and clay has been determined using thermogravimetric analysis (TGA).The influence of modified nanoclay on the mechanical properties of the polyvinyl alcohol nanocomposite have been investigated. Significant improvement in mechanical properties like modulus and tensile strength has been observed.
Evaluation of Momentary-Mold-Surface-Heating (MmSH) Process
In order to prevent molding defects such as weld-line, flow-mark, gas-mark, etc., various mold-surface-heating injection-molding technologies have been developed. The feasibility of these technologies depends upon the heating method. Electric heating is easy to implement and control. However, it increases cycle time due to deep thermal penetration under the mold surfaces. The patented MMSH process utilizes a flame heating with propane gas and heats the mold surfaces only. Since only the mold surfaces are heated, the mold can be cooled down quickly. It also improves the surface quality and the mold filling into a thin wall. In this experimental study, process variables such as cavity pressure, resin temperature and mold temperature are evaluated during the molding process. The process variables measured with and without flame heating are compared. The enhancement of surface quality by the MMSH process is also evaluated.
Hygrothermal Aging of Glass and Carbon Fiber Reinforced Nylon 6 Sandwich Injection Moldings
Previous studies on hygrothermal aging would typically involve films, plates or dumbbell shaped specimens produced by various polymer-processing techniques. This study utilizes a relatively new processing technique; the sandwich injection molding, which enables the production of moldings with distinctive skin and core layers that can comprise of either similar or dissimilar materials. Diffusion of liquids into conventional injection moldings would usually be Fickian. However, in sandwich injection moldings, the unique combination of different materials at different specimen depths, coupled with a very different morphology caused by the ‘double-resin-flow’ during the molding process, would provide a rather complex but interesting platform to examine the extent of permeability, diffusion kinetics, as well as susceptibility of these moldings to hygrothermal degradation. This study compares the moisture absorption kinetics of sandwich and conventional injection molded glass fiber (GF) and carbon fiber (CF)-reinforced nylon 6 (PA6) composites. The effects of hygrothermal aging on their mechanical properties were also elucidated. It was found that in the sandwich moldings, better strength retention upon redrying of the specimens after aging, could be expected if the skin layer consists of CF-reinforced PA6. Thus, it is believed that the skin layer (and not only the core) in sandwich moldings can also determine the final bulk mechanical properties.
Parallel True 3D CAE with Hybrid Meshing Flexibity for Injection Molding
True 3D mold filling simulation is becoming popular for its capability to providing better accuracy with minimum model simplification. However, such a large-scale non-linear computation places extreme demands on computing power. Moreover, the complex 3D geometry of the injection molded part further challenges the capabilities of the existing mesh generator and computation algorithms. In view of this fact, this paper develops an innovative parallel true 3D mold filling simulation technology, which allows for the adoption of hybrid volume element topologies. The parallel processing capabilities and the hybrid-element-supported solver capabilities of the proposed methodology have allowed the user to perform analyses in much less time on complex model with much larger element number than ever.
Study on Response Characteristics in High Speed Injection Hydraulic System
In this paper, systematic studies on the response characteristic of hydraulic servo system for the high-speed injection molding were presented. A PID controller with digital V/P control cards was utilized to understand the response characteristics of system. The human-computer interface through LabVIEW software was also developed to get command and feedback signals then calculate delay time and reaction time. Influence of delay time and reaction time of elements to response characteristics of system in a non-melt loading condition with accumulator turned on were investigated in different process setting particularly up to a high injection speed of about 1000 mm/sec. The measured results were also compared with melt loading condition. From the results, it was found that the response time, which increases with increasing load and injection command, whereas it will decrease with increasing hydraulic pressure under the conditions of speed closed-loop control, stable and stepping up the PID velocity control. Obviously, different PID controller and the power of system play dominant roles to influence the response of system. From the results, one can provide hydraulic serve system design guideline for designers to develop a high speed injection molding machine.
Seamless Integration of Injection Molding and Structure Analysis Tools
The application of CAE analysis in injection-molded plastic part is becoming popular in the recent years, especially for part structure design and molding process optimization. Users study the designs and experiments through numerous individual CAE tools. In fact, these analyses and designs should be mutually dependent. The process-resulting properties might be not favorable to the final products, such as fiber-induced anisotropic mechanical property. Besides, the mesh requirement for different CAE analysis might be different. In this paper, an integrated approach from design phase to manufacturing phase is proposed to seamlessly combine part structure analysis and injection molding analysis through related-data linking and mesh property mapping. This developed approach is proved from numerical experiments to be a cost-effective method for related part/mold designers.
Three-Dimensional Simulation of Multi-Shot Sequential Molding
For the recent years, multi-shot sequential molding is widely applied in various industries. It is a process that uses two or more molds to produce a multi-material component. In principle, the first material is injected into the first mold by standard single-material molding technique and then moved to the next mold where the next material can be injected to combine with it. This complex process is difficult to identify and study correctly by the traditional 2.5D model. In this paper, a three-dimensional numerical approach is developed to simulate the filling, packing and cooling stages in multi-shot sequential molding, as well as the part warpage after ejection. Several cases are reported to indicate the success of the present model.
Experimental Study of the Cavity Pressure during the Vibration-Assisted MIM
A novel vibration-assisted metal powder injection molding (MIM) machine was adopted to study the effects of the vibration amplitude and vibration frequency on the cavity pressure. The melt in the cavity could be manipulated dynamically and continuously during the vibration-assisted metal powder injection molding. The experimental results showed that the cavity pressure was decreased with the increase of amplitude/frequency when the average injection velocity was constant. The cavity pressure gradient was lower than that of conventional injection molding processing (without vibration) within our research scope. The metal powder could be molded at a relative lower temperature or a lower injection pressure without the loss of the product quality.
The Utilization of Benchmarking in the Financial Management of Plastics Processing Companies
The goal of this contribution is to show the possibilities of utilization of benchmarking and its procedures in the financial management of plastics processing companies. Benchmarking is a significant tool for financial management motivating the company managers to make necessary changes thereby affecting the performance of the enterprise. This contribution contains a benchmarking study of a sample of plastics processing companies operating in the United States and in the Czech Republic. The results of the study identify the areas of financial management of an enterprise that require particular attention in order to increase its performance. The concept of Economic Value Added as a measure of performance has been chosen.
The Effect of Ingredients and Processing Conditions on the Extrusion Processability of Halogen-Free Flame Retardant Thermoplasitcs
Inorganic flame retardants, such as aluminum trihydrate(ATH) and magnesium dihydrate(MDH), are most widely used fillers in halogen-free flame retardant polyolefin materials, especially for cable. These inorganic fillers, as they used in great amount, influence the rheological properties and extrusion characteristics of resin. During processing, they sometimes raise a problem such as die lip buildup, which refers to the resin accumulation on the open faces of extrusion dies. It commonly deteriorates the processability. The mechanism of die lip buildup is not fully understood, though there are many proposed explanations. The effects of resin composition and processing aids on the rheological and processing performance, including die lip buildup characteristics, were studied here. Also, processing conditions on the extrusion processability were investigated.
Consolidation of Glass-Fiber/Polypropylene Towpregs by Compression Molding
Compression tests were carried at different temperatures and constant press pressures on unidirectional GF/PP towpreg preforms. The experimentally determined displacement/time curves were compared to the simulations obtained from a theoretical model that assumes an isothermal process and two different fiber/polymer packing arrangements, one triangular and the other hexagonal.Discrepancies were found between the experimental results and theoretical simulations as consequence of the difficulties found in establishing the real fiber/polymer arrangement and polymer flow conditions during consolidation. This work presents an empirical equation, which includes two constants to be determined experimentally, that allows reducing those discrepancies and predicting with higher accuracy the relationship between the material properties (polymer viscosity and fiber and polymer particle dimensions) and the operational compression molding conditions (press pressure and consolidation time).
Using Additives to Improve the Properties of Composites Made from Towpregs
In the present work, a carboxylic-acid-anhydridemodified polypropylene additive was used to improve the interfacial properties of low-cost glass fiber/polypropylene (GF/PP) towpregs produced in developed dry coating equipment. The article describes how the use of the additive affects towpreg processing conditions. The towpregs were used to produce composites by compression molding and filament winding.The produced composites were submitted to mechanical testing. Improvements were clearly identified on the fiber/matrix interface by comparing the obtained results with those determined from non-added GF/PP composites.
Developing a Time Dependent Processing Window for Recycled Crosslinked Polyethylene
The chemical structure of crosslinked polyethylene (PEX) prevents easy reprocessability. Crosslinking of the polymer backbone covalently bonds it to another polymer chain. This bond prevents chain slippage and therefore any further melt processing. With an increase in time or temperature the crosslinking reaction will proceed, increasing its molecular weight to a point where it can not be processed a second time. The objective of this research is to determine a time window such that the crosslinked material can be reground and reprocessed using conventional melt processing equipment before the crosslinking reaction proceeds to a point where the material becomes unprocessable.
Compatibilizing Immiscible Blends with Block Copolymers and Pulverization
While addition of block copolymer during melt mixing of immiscible polymer blends has yielded compatibilization in small-scale academic studies, it has not been commercially successful due to thermodynamic and kinetic limitations. We show that addition of a commercially available styrene/ethylene-butylene/styrene triblock copolymer to an immiscible polystyrenepolyethylene blend during solid-state shear pulverization (SSSP) can substantially reduce coarsening in subsequent melt processing. In comparison with blends made by melt mixing, blends mixed by SSSP led to coarsening of the dispersed phase during high temperature annealing that was reduced by more than an order of magnitude. We believe that mixing block copolymer with the blend by SSSP yields greater levels of block copolymer near the interfacial regions as compared to melt processing. By overcoming the thermodynamic limitation of block copolymer micelle formation during melt processing, block copolymer addition via SSSP offers a commercially viable strategy for blend compatibilization.
Delamination Phenomenon and its Prevention in Water Jet Piercing of Continuous Fiber Reinforced Plastics
The water jet cutting of ACM laminates often causes a serious defect or delamination. This paper describes that water jet cutting can be successfully applied for small bore piercing of advanced composites by an impulse jet. Results of a piercing test on the laminates of continuous carbon and glass fiber reinforced plastics, confirmed experimentally and theoretically that a defect appeared in internal layers of material due to a bending moment of the bottom layer, caused by the high pressure of the jet. The bottom layer deflects to peel or delaminate from the upper layer as if it is a simple beam and finally as a cantilever lever at the bore edges as the hole progresses. Hence, the defect was most effectively prevented by supporting the work material behind the cut edges with a thick plate having a bore smaller than that of the nozzle.
Tunable Reflective Polymeric Nanolayered Films
An optical elastomeric system having a nanoscale layered structure was fabricated using a novel continuous coextrusion processing technology. This system was composed of hundreds of alternating layers of two elastomers with different refractive indices. When the layer thickness was on the order of quarter wavelength of visible light, these novel films exhibited reflectivity due to the periodic variation in refractive index (1-D photonic crystal). Nanolayer structure, reflectivity, and its tunability of these films were studied. Results indicated that the wavelength of reflection is tunable and reversible with applied strain. An analytical model was developed that agreed with the experimental data. Potential applications include tunable optical filters and optical strain gauges.
Modification of Polypropylene by High Intensity Ultrasonic Wave and its Characterization of Rehological Properties
A new method using high intensity ultrasonic wave, instead of peroxide-aided reactive extrusion, was applied to modify a linear polypropylene to a branched structure. To enhance and control the recombination reaction during sonication, multifunctional agent and antioxidant were used. From the rheological property measurements, it was confirmed that the modified polypropylene has nonlinear branched structure. Also, adequate use of antioxidant could control the degradation or recombination of polypropylene by stabilizing the structure during sonication.
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