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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Carbon Assisted Laser Sintering of Thermoplastic Polymers
Selective laser sintering (SLS) with CO2 lasers is only used commercially with polyamide (PA) and polystyrene (PS). This is because only these polymers absorb enough energy to melt properly in the SLS process.In a new approach, carbon black is added to the thermoplastic polymer powder. Carbon is sensitive to the wave length of Nd:YAG lasers and can absorb enough energy that adjacent polymer melts.In this paper a feasibility study of this new method is presented. As an example the sintering behaviour of the high temperature resistant polymer polyether ketone (PEK) is shown.
Evaluating Flow through Grill-Like Features Using Width-To-Thickness Ratio in an Adjustable Mold
Using a mold specifically designed for the purpose of studying Width-to-Thickness Ratios in grill shaped geometry, parts are molded at each of four different width-to- thickness ratio settings using a control ratio of 10:1 in each setting. Semi-crystalline and amorphous behavior is investigated.
Experimental and Numerical Investigation of the Elongational Viscosity Effects in a Coat-Hanger Die
The flow in a flat die is simulated using the axisymmetric and planar elongational viscosities of a low-density polyethylene (LDPE) resin. Elongational viscosity is found to have only a limited effect on the velocity distribution at the die exit. However, the predicted pressure drop in the die increased when the effect of elongational viscosity is included in the simulation. Predicted pressure drop is compared with the corresponding experimental data.
Comparative Performance and Barrier Properties of Biodegradable Thermoplastics and Nanobiocomposites vs. PET for Food Packaging Applications
This paper reports about the comparative behaviour, regarding PET, of biodegradable biopolymers such as PCL, PLA and PHBcoV and their nanobiocomposites, in terms of thermal and retorting resistance (thermal humid processes) and oxygen, water vapour and aroma barrier by means of time-resolved synchrotron radiation, FT-IR and permeation methods.
Drawing Forces and Film Properties in Semi Sequentially Stretched Polypropylene
The relationship between biaxial stretching kinematics and oriented polypropylene film properties was studied. Initially only transverse direction (TD) speed was varied while areal draw ratio and machine direction (MD) speed were held constant. Slow TD speeds increased final TD drawing force and produced anisotropic film shrinkage. Tensile properties were primarily a function of draw ratios. Using different MD and TD draws allowed tensile properties to be changed while holding film shrinkage nearly constant.
Melt Fracture Analysis Using an In-Line Camera
A low melt flow rate metallocene isotactic polypropylene homopolymer was cast into film with and without melt fracture. Using an in-line camera, melt fracture was quantitatively described using real-time measurements of film defects. Melt fracture caused more variation in light transmittance, leading to a higher defect count. This measure of film optics was more sensitive to melt fracture than haze or gloss.
Effect of Flow Behavior on Internal Structure of PC/ABS Injection Moldings
Effect of flow behavior on internal structure of PC/ABS injection moldings was investigated. The cross sections in flow direction of etched specimens were observed, and the thicknesses of the cavities (ABS rich region) through thickness direction were measured. Subsequently, the flow field was calculated by using CAE software and the relationship between the flow behavior and internal structure was examined. As a result, it was found that the maximum shear stress and solidification time of the resin was important in determining the final morphological properties.
The Effect of Molecular Weight on the Interfacial Properties of GF/PP Ingection Molded Composite
The interfacial shear strength of glass fiber(GF)/polypropylene(PP) injection moldings were investigated by using the Kelly-Tyson formula. PP was grafted with maleic anhydride for compatibilization purpose. The weight - average molecular weight of PP was also varied. As a result, it was found that the interfacial shear strength of GF/PP can be influenced by changing weight - average molecular weight of PP. Smaller weight - average molecular weight of PP would yield higher interfacial adhesive strength between the glass fiber and PP.
Scratching Behaviors in Injection Molded Products
Scratch behaviors of injection molded products, such as PS, HIPS, ABS, PC/ABS, were investigated. From the observation by optical microscopy of scratch, the damages generated were understood. They depended on the types of polymers and the structure near the surface generated during the injection molding. The scratch behaviors would be affected by friction between the polymers and scratch tip and modulus, yield strength, fracture toughness of the polymers.
Fast Simulation Methodology and its Application in Injection Molding
The injection molding is a popular technique of polymer processing, which multiple parts with tight tolerances and complex shape can be produced in a single operation. Through studying the flow behavior of melt in cavity and runner system, a fast flow simulation method is developed based on the introduction of the equivalent flow length concept. The optimization algorithms and fast flow simulation technology are integrated to optimize gate design.
Mechanical Properties of Polyoxymethylene Copolymer Injection Moldings
Polyoxymethylene (POM) copolymer using dioxysolane (DOL) with polyethyleneglycol (PEG) was fabricated by injection molding. The DOL and PEG contents were varied, and the effects of them on morphology and mechanical properties were discussed. Small particles were observed in the case of PEG 1-5wt%, and the number and diameter increased with increasing PEG content. The charpy impact strength increased with increasing PEG content. Such morphology with particles resulted in the improvement of the impact strength.
Morphology of PC/ABS Blend Systems Fabricated by Injection Moldings
Morphology of PC/ABS injection moldings was observed by TEM in parallel to flow direction and transverse. The thin films, which thickness was less than 100 m, of PC and ABS were observed near the surface with regardless of injection speed, while ABS was in fibrous shape at the center. The geometry of butadiene rubber domains creating salami occluding SAN was a focus. It is confirmed that they elongated in flow directions.
An Approach to Gradation Mesh Generation in Injection Molding Simulation
Based on advancing-front method and Delaunay triangulation concept, a new interior point generation scheme is proposed. The longest edge at the current advancing-front is always chosen to create a new triangle element by using Delaunay triangle’s property, so that a high-quality graded mesh is obtained and a smooth transition in element size is maintained. The high-quality mesh can make plastics injection molding computer simulation more precise.
Influence of Clay Orientation and Aspect Ratio on Morphology and Mechanical Properties of Nylon-6/Clay Nanocomposites
The influence of clay orientation and aspect ratio on morphology and mechanical properties of nylon-6/clay nanocomposites is investigated. Our findings suggest that clay orientation can affect the nucleation and orientation of crystalline lamellae of nylon 6 matrix. The presence of clay also hinders the relaxation of nylon matrix during annealing. Consequently, clay aspect ratio and orientation can greatly influence the overall morphology and mechanical properties of the nanocomposite.
Simulation of Flow Patterns of Melt during Melting Process of Single-Screw Extrusion with Vibration Force Field
The polymer melting mechanism in a novel extruder with extra axial vibration was studied. A self-amended non-isothermal Maxwell constitutive equation was used in simulating the special flow patterns of melt in the melt film between the driving wall and the solid/melt interface with various vibration force fields. The simulation results indicate that within a certain vibration strength range, the vibration force field can optimize the distribution of the shear rate in the flow field, thus accelerates the melting process.
Novel Dynamic Nucleation Theory for Microcellular Plastics
Polystyrene microcellular plastics blown with supercritical carbon dioxide were prepared by novel electromagnetic dynamic foaming simulator. Bubble nucleation processes in stable and dynamic shearing flow field were analyzed. The experiments showed that after imposing vibration, cell size decreased and cell density increased. The key issue with dynamic nucleation is that the shear energy generated by mechanical vibration improved bubble nucleation. Novel dynamic nucleation theory was put forward from the viewpoint of shear energy in this paper.
Flow Dynamics in Injection Molding with Microfeatures
Filling the microchannels is very important in designing micro-injection molding, microdevices, etc. In this paper, flow dynamics was studied in injection molding with microchannels. A transparent PMMA mold was designed and the flow dynamics was observed. The experiment was performed using poly (ethylene oxide) (PEO) and polyacryamide (PA) aqueous solutions. The transient dynamic flow and flow competition between the base plate and the microchannels were observed. The flow observation was used to explain previous filling length results in microchannels during micro-injection molding.
The Effects of Runner Diameter and Cavity Size on Packing a Part in Injection Molding
This paper presents the study which challenges some of the classic theory regarding runner sizes as related to packing. This study has found that, in some cases, packing control can be maintained with runner diameters which may be as small as, or even smaller than, the wall thickness of the parts being molded. This study further showed that in some cases, increasing cavity size allowed for improvements in packing control. Both of these findings are contrary to the classical wisdom used for today’s runner designs.
Performance of a Machine Augmented Composite
An advanced machine augmented composite was fabricated and tested. This composite is composed of rigid polyurethane machines with pre-buckled walls as a reinforcement and soft polyurethane as a matrix. Dynamic properties of the composite were measured in the frequency of 0.1 ~100 Hz range at room temperature by load-controlled cyclic testing. Measured tan ? values and loss modulus showed noticeably higher values than the matrix did at the frequency range of 0.1~ 40 Hz.
Part Weight Prediction Using Capacitive Transducer in Injection Molding
Quality of the injection molding product is getting increasingly important in the industry. One of the most important product quality measurements is the part weight. In this paper, a novel method is proposed for on-line weight prediction with the use of a capacitive transducer (CT) installed inside the injection mold. Experiments with different conditions show that the proposed method of using CT signals, through simple linear fitting, can indeed provide on-line predictions of the product weight, providing a practical means for process monitoring and online quality control.
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