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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Study on Mechanical Properties of ABS Parts in Microcellular Injection Molding Process
The study uses a fixed amount of ABS as matrix, mixed with supercritical fluid (N2) in different proportions, in order to obtain foamed ABS. The resulting product of the above is a structured foamed ABS, by which to research into the MuCell process. The results of the study indicate that increasing the amount of the blowing agent will obviously improve the warpage and shrinkage, but this will also decrease the strength of tensile and impact.
Using Thermal Process Imaging for Extruder Analysis and Improvement
A scanning infra-red thermal imager is used to continuously measure extrudate temperatures in an extrusion coating process. Position dependent and time dependent process variables are recorded and can be used for process improvement. Before and after images are shown and discussed with corresponding machine and process modifications.
Adhesive Properties of Terpene Cleaning Solvent Residues
A commercial terpene-based cleaning solvent has been found to contain a significant amount of non-volatile residue. This non-volatile residue has been isolated and characterized. DSC has shown that the material is capable of exothermic reaction at ~ 150°C. Additional analytical techniques, FTIR, GPC and viscometry have been used to further characterize the reaction. Tensile and double lap shear test specimens were prepared and used to characterize the bond strength. The rate of reaction was found to depend significantly on the availability of air. Arrhenius activation energies were obtained from mechanical test data results. Under the most severe reaction conditions used the adhesive material did not crosslink. Removal of the adhesive residue was possible using solvents, such as isopropanol.
Simple Technique for Abatement of Noise Generated from an Air Ring of a Large Polyethylene Film-Blowing Equipment
This paper presents a simple technique to suppress a high level single-tone sound pressure generated from the air ring of a large polyethylene film blowing machine when operating close to its high output range. SPL suppression obtained was in the order of 27-29 dBA. Analysis showed that the shallow cavity created between the adjustable chimney inner geometry and the fixed chimney of the upper air ring is responsible for a discrete tone noise around 119 dB. Two positions of the adjustable chimney were found to be responsible for this high single-tone noise. The suppression technique was based on a perforated sliding collar placed around the chimney, which has the effects of reducing the initial perforation on the adjustable chimney.
New Concepts in Mold Comformal Cooling Design
Cooling system design is important in mold designs to achieve short cycles, dimensional stability and reduced part stresses. Traditionally, cooling lines have been machined into mold components to avoid interference with the ejection system, coring and other mold details. Efforts have also been made to create turbulent flow in these lines to maximize heat transfer. Over the years straight cooling lines have given way, in part, to conformal cooling techniques often using free form fabricated mold components. The author has taken conformal cooling to the next level. In this concept, cooling is accomplished by designing various shapes of cooling channels. These channels control the heat exchange medium flow direction and flow rate in order to extract the proper amount of heat from the mold where it is needed. This is demonstrated by laboratory results from experiments utilizing various cooling design concepts in a standard part.
Impact of Rheological Properties on Melting Rate Calculations
Melting rate calculations have been shown in the literature to be strongly effected by the temperature dependent effects (flow activation energy) of polymer viscosity, especially for amorphous polymers1. And this is an important factor in explaining the poor model results for polymers relative to semicrystalline polymers observed in the literature2. Over the years a great number of changes in catalyst systems have occurred in the polymerization of “standard” polymers such as polypropylene and polyethylene. These new catalyst systems have appreciable changed the temperature response of the polymers which can have a significant impact on melting rate calculations. This paper will examine the cause of many melting models general failure with amorphous polymers in relationship to existing experimental melting rate calculations which clearly highlight the importance of the temperature sensitivity of the viscosity to accurate melting rate calculations.
The Effect of Recycle History and Processing Temperature on the Weld Line Strength of a Polypropylene Homopolymer
This investigation focuses on the inherent recyclablility of a polypropylene homopolymer by characterizing the mechanical and rheological properties of a multiprocessed resin. The investigation studied molded samples both with and without the presence of a weld line. Several blends of virgin and reground polypropylene homopolymer (consisting of 5 recycle histories) were prepared. The tensile properties (including weld strength) and melt flow rate tests were performed on all molded samples from each of the blends.The results of the study showed that regrind did not affect the tensile modulus, tensile strength at yield, or elongation at yield for samples molded without the weld line to any significant degree. The presence of a weld line had a negative effect on the mechanical properties of the molded sample. The weld line strength also decreased significantly as regrind concentration increased. Melt flow rate tests of the various blends showed the melt flow rate increased by a total of 29% over the entire range of regrind percentages studied. Increasing the processing temperature did have a positive effect on the weld line strength. The addition of regrind did not affect the first stage injection pressure or cavity pressure observed during the molding of the test samples.
Bonding Strength in Micro Injection Assembly Moulding
Polymer materials offer a wide range of properties that can be chosen according to the functional necessities. Therefore these materials are increasingly often used for decisive elements in micro systems. Injection molding as a production process for polymer materials can also be applied as a joining and assembly process in addition to generating micro parts. This approach offers a high potential for micro technology, since an offline joining process can be avoided by overmolding of the components, where it is possible to generate movable and force fit connections. New research at IKV (Institute of Plastics Processing) shows progress made in the attainable bond strength of hybrid micro systems. A specific testing method for different material combinations has been developed. Since plastics/metal bonds possess little adhesion, surface modifications such as increased surface roughness or silane coating show promising results.
Functionalization of Polyolefins through Catalytic Hydrosilylation and Imidation Reactions
Polypropylene and polyethylene were terminally functionalized with anhydride groups through a two-step solution catalytic hydrosilylation reaction. Subsequently, the anhydride group in the functionalized polymers was reacted with 1,6-diaminohexane following an imidation reaction to produce primary amine functionalized polymers. The anhydride functionalization of polyethylene was also carried out in molten state. The functionalized products were characterized by FT-IR and an acid-base titration method, and attempts to prevent crosslinking of polyethylene and the application of the novel anhydride functionalization technique in extruders are discussed.
A Novel Suspension Polymerization Process without Mechanical Agitation, Yielding Mono-Sized Beads
The concept of a novel suspension polymerization technology without mechanical agitation is presented. It aims to yield a practically monosized product, allows the inclusion of a variety of components in the polymer matrix with a potential for broader range of products, compared to a conventional stirred-tank process. The technology is comprised of two stages: dispersion of an organic phase into droplets with the required size, and the subsequent polymerization of the droplets, while preserving their initial size distribution. The dispersion method combines pressure atomization of the organic phase below free surface of a stabilizing continuous phase, with the controlled pressure pulsation imposed on the flowing stream, and yields mono-sized droplets for both Newtonian and Non-Newtonian viscoelastic liquids. The atomized droplets are next polymerized in low shear, low turbulence flow pattern created within the continuous phase, by injecting an inert immiscible gas at selected reactor locations. The process was validated on lab-scale; the results are presented and discussed.
Properties and Applications of Blends of High Melt Strength PP and Linear PP
Polypropylene and its variants by far offers the best balance of cost and performance for wide range of applications requiring flexibility, toughness, rigidity, heat and chemical resistance. However, one major drawback of PP is its low melt strength, which limits its use in blow-molded, thermoformed and extruded and injection molded low-density foams. During last decade, various PP grades with improved melt elasticity have been introduced to overcome this drawback. However, in neat form processors find these HMSPP difficult to process and expensive. This paper describes various approaches to impart high melt strength to PP. It is shown that blending 10-30% of HMSPP with linear PP produces significant and unexpected benefits.
Novel Method for Rapid Determination of Tehrmoformability
The demand for large parts with thick wall, constructed of multiple polymer layers, along with the desire for quick turn around time, lower tool cost, and low pressure processing is making thermoforming very attractive over injection molding. In spite of the long history, thermoforming is still very much an art than science. There are very few reliable tests available to processors and researchers for analyzing and quantifying thermoformability. This paper presents comparison between current methods and a novel test apparatus, which closely simulates thermoforming process under controllable conditions while collecting quantitative information, which can be used to assess, compare, optimize or predict thermoformability of test material.
Collocation Method Solution with Radial Basis Functions of the 2D Energy Equation
This paper describes the collocation method with radial basis functions (RBFCM) of the 2D energy equation for Newtonian and non – Newtonian fluids, These fluids are widely used in polymer processing in various processes like extrusion, blow molding, and injection molding. The 2D energy equation involves specially the variation of the thermal properties with temperature and the viscous dissipation term. The boundary conditions are of Dirichlet, Neumann and Robin Type. The accuracy of the solution is assessed by comparison with well known analytical solutions and numerical procedures, such as, benchmark test, found in the literature. The problem of the fluid between the two parallel plates is completely simulated using RBFCM. It is clear the accuracy of the RBFCM solution assessed by comparison with the analytical solution and the DRBEM numerical solution.
Foaming Polystyrene with HFC-245Fa and Blends of HFC-245Fa and CO2
HFC-245fa is a newly available blowing agent that was developed specifically for the polyurethane market. It is however, sufficiently soluble in polystyrene and polyethylene so that it can be successfully used in the thermoplastic foam extrusion process at moderate concentrations.Higher loadings of gas were tested in polystyrene and were found to generate large holes owing to inadequate nucleation. Blending small quantities of CO2 with HFC- 245fa turned out to be beneficial for foaming and allowed to decrease the foam density further than using HFC-245fa alone. Moreover, it improved the overall morphology of the foam and reduced the incidence of extrusion defects.
The Preparation of TPU /Silica Hybrid Using Sol-Gel Process
Thermoplastic polyurethane elastomer/silica hybrid (TPU/SiO2) using sol-gel process was prepared. This work was undertaken to investigate the thermal and physical properties of this type of hybrid by employing different catalyst systems during sol-gel processing. Two types of catalyst systems including acetic acid (HOAc) and HCl were used to prepare sol particles. The mixing of sol solution and TPU solution was then carried out to form TPU/silica hybrid. Fourier Transform Infrared (FTIR) spectra and dynamical mechanical properties were recorded to depict the enhanced interfacial interaction. Thermogravimetric analysis was used to determine actual silica content forming in the hybrid, and to evaluate the heat resistance of hybrid. Mechanical property such as tensile strength was investigated at various concentrations of in situ silica. Tensile strength increased at all concentrations of silica. HOAc catalyzed system showed better optical property than HCl catalyzed system. Fracture surface was revealed through SEM (scanning electron microscopy) to observe the dispersion degree of SiO2, which in turn confirmed the results of optical property and mechanical properties.
Study of Dynamically Cured PP/Mah-g-PP/Talc/Epoxy Composites
In this paper, an epoxy resin was dynamically cured in a PP/MAH-g-PP/talc matrix to prepare dynamically cured PP/MAH-g-PP/talc/epoxy composites. SEM analysis shows that the maleic anhydride-grafted polypropylene (MAH-g-PP) and an epoxy resin are demonstrated to effectively increase the interaction adhesion between PP and the talc in the PP/talc composites, dynamical curing of the epoxy resin can further increase the interaction in the PP/MAH-g-PP/talc composites. The mechanical properties of PP/MAH-g-PP/talc and PP/MAH-g-PP/talc/epoxy composites are better than that of the PP/talc composites. The dynamically cured PP/MAH-g-PP/talc/epoxy composites have the best mechanical properties in all the PP/talc composites. The suitable content of epoxy resin in the composites is about 5wt%.
Advanced Development of Molded Expanded Polypropylene and Polyethylene Bead Foam Technology for Energy Absorption
Recent advancements in the field of polyolefin resins in the area of PP+PE copolymers, impact co-polymers, and homopolymers have allowed for the creation of a new class of thermoplastic foam products. These new products are capable of improved performance due to the advancements that have been made in the area of polyolefin resin catalyst systems. These new Metallocene catalysts are being used to create resins with improved mechanical properties that otherwise were not available using the traditional Ziegler- Natta catalyst systems currently being used to produce a majority of the thermoplastic materials available today.This paper describes these recent advancements and how they allow for improved properties in the area of moldable expanded bead foam used in the automotive, marine and recreational occupant safety and cushioning system designs. This technology allows for improvements in the mechanical properties of these thermoplastic foam components, while allowing them to be produced on existing processing equipment. This paper will also compare these advancements to those currently being used, and demonstrate how improvements in performance, system integration, and cost can be realized. Compliance to existing and new environmental substance regulations and restrictions are also addressed.
Numerical Simulation of Deformations for Injection Molded Parts
Thermally induced stress and the relevant warpage cause by inappropriate mold design and processing conditions are problems that confounded the overall success of injection molding. A thermorheologically simple thermoviscoelastic material model is used to simulate the residual stress and warpage within injection molded parts generated during the cooling stage of the injection molding cycle. The initial temperature field corresponds to the end of the filling stage. The fully time-dependent algorithm is based on the calculation of the elastic response at every time step. Numerical results are discussed with respect to temperature and pressure.
The Investigation of the PTFE Wall Slip Effect in Paste Extrusion
Polytetrafluoroethylene (PTFE) is a remarkable material having high melting temperature, high chemical resistance, low frictional and dielectric coefficients. However, PTFE fine powder cannot be processed without understanding the rheological behavior of paste powder. In this study, a simple PTFE rheometer was built and the PID control technology used to control the extrusion pressure and extrusion speed (from 2mm/s to 0.5mm/s). Different extrusion length from 45mm to 94mm to change the L/D ratio were also utilized. After analysis of measured data, it was founded the viscosity of PTFE paste basically follows the power law with shear thinning behavior similar to thermoplastics melt. Because of wall slip effect, the pressure drop was one order of magnitude less than that without wall slip and wall slip becomes more significant at high extrusion speed. Lower extrusion speed also results in a better performance in extrudate.
3D Simulation and Verification for Mold Temperature Control Technologies
Three new temperature control technologies: 1) high and low temperature coolant switchover for heating/cooling, 2) electrical heater combined with medium temperature coolant, 3) induction heating combined with low temperature coolant, have been simulated and verified in the paper. Traditional injection molding software of temperature field usually cannot deal with any heat source item multi-processing cycles, e.g. heating/cooling switchover in the same coolant channel, electrical heater and induction heating. Therefore, fully 3D temperature simulation technology for different heating system was constructed. To verify the simulation technology, a mold plate temperature field of each heating/cooling control system has been simulated first. Temperature heating/cooling cycle with selected points on mold plate surface variation ranges within 50--100--50-and 50--110--50-, were designed and experiment data were measured by thermometer, and infrared radiation thermal imaging (IRTI) system. The predicted results show quite precise predictions in accordance with experimental results. Finally, an actual lens mold with combined temperature control system of heater and coolant switchover has been simulated by coupled-field solution. All studies indicate that the simulation technologies are reasonable accurate and feasible.
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