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.
Compounding extrusion of Polypropylene-Carbon nanotube composite is presented as a case study with Design of Experiments approach to identify best processing parameters for optimum dispersions and conductivity. Influence of Specific Mechanical Energy input on resulting morphology and volume resistivity of extruded strands are analyzed with statistical viewpoints. Resistances of the melt are measured with an online process monitoring approach and correlated with measurements on extruded strands. This aids process planning, and economization.
The causes of a drastic reduction in the service life of plastic enclosures molded from an acrylonitrilebutadiene- styrene (ABS) resin have been investigated. The mechanism and type of failure have been deduced from a detailed morphological examination of the fracture surface. Various factors responsible for a rapid failure of the enclosure have been identified. Analytical testing such as infrared spectroscopy and differential scanning calorimetry were performed to identify a specific material characteristic responsible for the failure. The results obtained during the evaluation indicated that the failure was due to environmental stress cracking, which occurred as a consequence of the presence of an incompatible chemical and assembly stress. The nature of the chemical agent was found and its effect on the properties of the ABS is discussed.
Three major polyethylene (PE) engineering plastics, linear-low-density (LLDPE), low-density (LDPE) and high- density (HDPE) are studied in capillary flow. The purpose is to find experimentally and predict numerically their flow behaviour, namely the pressure drop in flow through tapered dies. This behavior is related to their individual rheological and flow properties. Using a series of capillary dies having different diameters D and length-to-diameter L/D ratios, a full rheological characterization has been carried out, and the experimental data have been fitted with the viscoelastic K-BKZ/PSM model. The branched LDPE has a strong pressure-dependence of viscosity, with a pressure-dependent coefficient ?p. For the linear LLDPE and HDPE melts, the pressure-dependence of viscosity is weak, but slip at the wall is strong and affects their flow behaviour. Thermal effects due to viscous dissipation are included but are rather mild. It is found that the viscoelastic simulations are capable of reproducing the experimental data well, in the whole range of apparent shear rates and L/D ratios.
Calendering is a process for producing plastic sheets of a desired final thickness and appearance. The thickness of the exiting sheet during a calendering operation is uniquely found by the Lubrication Approximation Theory (LAT) and the application of the Swift boundary conditions, which dictate that both the pressure and its axial derivative are zero at detachment. This cannot be used in a 2-D analysis of the process, where the detachment point is the anchor of a free surface, and hence a singular point where both the pressure and the stresses go through numerical oscillations. This difficulty can be circumvented by using the Boundary Element Method (BEM), which uses as primary variables velocities and tractions, and thus avoids pressures and stresses. Then the detachment point is found as the point where the tangential traction becomes zero. Numerical tests undertaken here with the Finite Element Method (FEM) show that the LAT results can be used as a good approximation for the detachment point, which is then fixed. Comparisons with 2-D BEM results show a good agreement for all flow field variables. However, the exact position of the detachment point in a 2-D FEM analysis is still elusive, since for viscous polymer melts the contact angle is not known and should be part of the solution. Some thoughts are given about how to tackle this still unresolved issue, based on double nodes with discontinuous velocities and pressures.
The miscibility between drug indomethacin and excipient Eudragit® E PO were extensively characterized by rheological and thermal analysis. The evolution of glass transition temperature and activation energy with indomethacin concentration indicates the existence of overall positive deviation which represents anti-plasticization effect. The rheological analysis is in agreement with the thermal analysis, and both methods indicate that the miscibility between them is very good for indomethacin concentrations up to 60~70%.
The injection molding process is widely known as one of the most advanced processes for manufacturing of parts that range from simple commodities to accurate technical parts. Due to the cyclical process the power consumption is highly discontinuous causing distinct peak power. This article describes an alternative local drive concept, which is able to realize a continuous power consumption during the injection molding process. This concept is designed for tasks with a high power demand, for example clamping forces about 13.000 kN.
Polypropylene blown film containing 1 wt% nanoparticles was fabricated which organoclay and copper nanoparticles were incorporated for barrier and antimicrobial purpose. Effect of copper nanoparticle content (5, 10, 15 and 20 wt% of total nano-fillers) on clarity and mechanical properties of polypropylene nanocomposite film was investigated. Nanocomposite PP films were fabricated via water-quenched blown film extrusion. A sodium neutralized ethylene-methacrylic acid ionomer of 2 phr was used to modify compatibility between polypropylene and nano-fillers.
The morphological basis of improvements in film haze achieved by blending LDPE into LLDPE was explored with light scattering. Two-dimensional light scattering patterns were analyzed by a novel approach to define a “Morphology Index”. Besides its utility as a numeric descriptor of the superstructure in the continuum from spherulitic to fibrillar morphologies, the Morphology Index was also found to correlate well with the internal haze of films.
The dielectric lifetime and breakdown mechanism of PC/PVDF-HFP systems were studied under constant DC field. The 32 L and 256 L PC/PVDF-HFP systems show two orders of magnitude longer dielectric lifetime compared with blend system of PC/PVDF-HFP. It is attributed that the layered structure can impede the breakdown process by deflecting the fracture propagation pathway. The DC resistivity of PC/PVDF-HFP systems was measured and correlates well with the dielectric lifetime in PC/PVDF-HFP system, which implied that the DC resistivity is also an important factor contributing to the enhancement of dielectric lifetime of the layered films.
In this study, thermal and rheological properties of polyamide 6 (PA6), poly (m-xylene adipamide) (MXD6) and their commercial nanocomposites (4 wt.% clay) were studied. Dynamic rheological experiments were carried out for both neat resins and corresponding nanocomposites at different temperatures. Rheological measurements were conducted using a strain-controlled rheometer. Crystallinity and thermal transitions of the materials are established via both DSC and XRD techniques. Oxygen transmission rates were also measured and normalized by the films thickness.
Gas permeation measurements performed on films according to the standard take a long time. We present a method with helium for a quick measurement with measuring times of only a few minutes. This allows an accelerated iterative development of new formulations for films directly at the production line and the monitoring of the barrier properties for quality control. The investigations show a good correlation between the results of the accelerated and standardized tests.
This study shows how the flow uniformity from a film die can be improved by modifying the geometry of the die using a three dimensional finite element optimization technique. In this study, various optimization strategies were used to optimize the geometry to meet the desired objectives of uniform flow at the die exit and minimal pressure drop. Finite element simulations using the numerically optimized geometry predict a more uniform flow than simulations using the baseline geometry. However, some of the numerically optimized die geometries obtained in this study would be impractical to fabricate. Thus we see the power of CFD-based optimization methods to lead towards potentially better performing options; but we also see the necessity of understanding both the die design technology and fabrication techniques in order to analyze the practicality of the proposed optimized solutions. This knowledge can be used to redirect the optimization towards more practical solutions through the use of geometric constraints.
The advent of new base raw materials composed of recycled post consumer/post industrial plastics combined with organic bio fibers that up to now had no value added/sustainable use, has created a global market for a new classification of materials, Bio Fiber Composites. Fundamentally, these composites reduce the hydrocarbon content, (oil) replaced with natural fillers in the form of organic “renewable.” This family of materials is best suited to replace pure polymers, and drives the green, sustainable shift of achieving a balance of physical and mechanical properties to produce the goods and components needed across the complete product landscape. Any product that is injection molded, extruded, thermoformed, or rotationally molded today, can be replaced with a natural organic filled BioComposites Materials. MCG BioComposites, LLC has been formed to supply this place in the industry. This paper will demonstrate the uses and commercial applications for various biomasses, i.e., corn cob fiber, flax fiber and wheat starch.
The simulation of thermally and flow induced crystallization behavior of semi-crystalline polymers is of great engineering significance in polymer processing like injection, blow molding and extrusion. However, its key technology for practical application remains to be difficult. In the study, the mathematical model of three- dimensional thermally and flow induced crystallization of polymer melts obeying Phan-Thien and Tanner (PTT) constitutive model is established. A penalty finite element/finite difference method is introduced to solve the nonlinear governing equations. The computation stability is improved by using the discrete elastic-viscous split stress (DEVSS) algorithm incorporating the streamline upwind scheme. A modified Schneider’s approach is employed to discriminate the relative roles of the thermal and the flow state on the crystallization phenomenon. Two driving causes for the crystallization of polypropylene in extrusion process including the thermal and the flow state are investigated. Both the crystalline distribution and crystalline size of polypropylene are obtained based on the proposed mathematical model and numerical scheme.
Mold flow analysis of mobile phone case was used in this study to evaluate the intrinsic characteristics of biomass materials how to influence the parameters of injection mold process and the outward appearance of product. Two materials were selected, one is TPS/(PC/ABS) biomass-based material developed by ITRI, and the other is commercial petrochemical plastic PC/ABS. In addition to evaluate the difference between these two materials in the injection mold process and dimensional stability, carbon emissions during this injection mold process were also calculated. Above results will show advantages and shortcomings of this newly developed TPS/(PC/ABS) biomass-based material.
The present work attempted to implement reactive compatibilisation of blends of recycled engineering plastics, more particularly the case of recycled PA66 contaminated by recycled PA6. Low molecular weight, high Tg Styrene-Maleic Anhydride copolymers were tested as chain extenders / compatibilizers. It appeared that the addition of 2% by weight of SMA to an incompatible system of recycled PA6 and PA66 improved both ductility and impact performance by factors of at least 10 and 1.5 respectively. Moreover, high Tg SMA improved performances at elevated temperature, partly due to its ability to effectively crosslink but also because of its inherent heat resistance.
A high percentage of today’s blown-film-extrusion-machines is equipped with a reversing system. The reversing draw-up unit is supposed to rearrange tolerances of the thickness profile on the film-roll within the winding process. Most process setups in the blown-film-extrusion production have a standardized reversing speed or do not use the reversion. A new simulation model developed at the University of Duisburg-Essen can show the critical effects of these setups in the build-up of film rolls and links them to detected defects in today’s production.
Vapor grown carbon nanofiber (VGCNF) / High density polyethylene (HDPE) conductive nanocomposites were prepared by melt mixing. The nanocomposites electrical and electromagnetic (EMI) shielding properties were studies as function of filler concentration. The electrical resistivity of 1.5 vol% VGCNF/HDPE nanocomposite was 105 Ohm-cm indicating that this nanocomposite is suitable for electrostatic discharge (ESD) protection applications. In the 0.1-1.5 GHz frequency range, 2 mm thick plates made of HDPE filled with 5 vol% VGCNF showed an EMI SE of 20 dB, this level of attenuation is adequate for laptop and desktop computers shielding.
Moulding of micron features is a pre-requisite for manufacturing of polymeric microfluidic chips. The final quality of moulded microfluidic chips could be affected by the various types of design factors in a mould feeding system. In this paper, two design factors, notably the gate location and gate type, are extensively evaluated through finite element analysis (FEA) simulation to investigate how the melt flow behaviour of polymer could affect the quality of moulded microfluidic chips.
Cross-linking of polymeric biomaterials has increased in interest over the last 5-10 years. One category of biomaterials is hydrogel, a chemically cross-linked network that swells when immersed in water. Dextran, a polysaccharide, can be crosslinked to form hydrogels that have found application as tissue scaffolds and delivery devices. In this study, dextran is cross-linked with diisorbide bisepoxide, a water soluble chemical cross-linker. The gelation temperature and gel time will be monitored using oscillatory rheometer.
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Brown, H. L. and Jones, D. H. 2016, May.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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