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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Effect of Temperature and Pressure on Surface Tension of Polystyrene in Supercritical Carbon Dioxide
The surface tension of polystyrene in supercritical carbon dioxide is determined experimentally by Axisymmetric Drop Shape Analysis-Profile (ADSA-P), where a high pressure and temperature cell is designed and constructed to facilitate the formation of a pendant drop of polystyrene melt. As pressures and temperatures increase, the surface tension of polystyrene decreases. A linear relationship is found between surface tension and temperature, and between surface tension and pressure. The slope of surface tension change with temperature is dependent on pressure.
Reactive Extrusion Process Characterization: Q/N Mapping Method
Reactive extrusion is an important industrial compounding process. Usually, a product is manufactured by the product by process" approach without direct monitoring or control of the critical in-situ chemical reaction. By means of a rapid steady state throughput (Q) and screw speed (N) mapping method described in previous publicat mean residence time and physical properties. The reactions examined include polymer degradation (peroxide cracking of Polypropyleneions a reactive extrusion processes is characterized by several model parameters derived from the on-line monitoring of the mixing intensity and time as measured or estimated from power consumption Polyester degradation) and in-situ grafting (Polyamide 6/SMA). In this study the effects of Q and N on melting mixing and rates and extent of reactions that change viscosity were quantified process changes in reactive extrusion systems with linear models of power consumption and mean residence time. Since these reaction systems tend to be controlled by interfacial area generation the effects of mixing intensity and time were captured. Using the proposed method such as rate optimization can be made without compromising product quality e.g. extent of reaction."
Dynamic Mechanical, Thermal and Fracture Toughness Properties of PC/ABS Blend System with Incorporation of Pcoligomer
The successful blending of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) has led to its many commercial applications such as electronic housings and automotive accessories. The presence of low molecular weight components in any resin is usually avoided due to their detrimental effects on mechanical performance of the final part. In this case, however, the incorporation of PC-oligomer was found to have enhanced the toughness and deformability of the molded product, even though the miscibility between the PC and ABS phases were poorer judging from the increased differences in terms of their glass transition temperatures.
Extrusion Compounding Fundamentals: An Industrial Perspective on Melting and Mixing of Polymer Blends
The classical explanation that melting and mixing take place sequentially in an extruder will be examined in view of the melting mechanisms existing in the literature, most notably laminar conductive and mixed melting models. Recent results utilizing the pulse perturbation technique suggest that phenomena such as lubricated melting, and morphological development involving phase inversion take place during dissipative mix-melting of polymer blends when the onset and rates of melting of each ingredient are different. Traditional polymer dispersion principles based on melt mixing of non-interacting particles can still be used to some extent, but with modifications, in view of the complications brought upon by the high concentration of the minor ingredient present.The melting and mixing principles thus derived have a profound influence on many commercially important compounding processes, especially plastic and rubber blending with in-situ grafting, or with in-situ rubber crosslinking, and compounding of polymers and plasticizers. The morphological development schemes during compounding introduced in the literature can now be viewed using the derived mixing principles in conjunction with the melting mechanisms described above.
Comparison of Shear and Butt Joint Designs for Vibration Welding of Polypropylene-Based Nanoclay Composites
Polymer/clay nanocomposites are attractive because addition of small amounts of clay platelets increases the modulus, strength, and reduces permeability of the material. Previous studies showed that for hot plate, vibration and ultrasonic welding, the weld strength decreases with increasing nanoclay content. It was theorized that squeeze flow during welding produced adverse orientation of the clay platelets weakening the weld. Therefore, vibration welding of butt and shear joints that produce different flow patterns were evaluated. Test results for vibration welds show that even shear joints had significant reductions in weld strength probably due to vibration induced flow and orientation.
Processing of Nanocomposites with Gradient Architectures in Twin Screw Extrusion for a Novel Combinatorial Approach
Nanocomposites, with superior material properties, have promising potential applications in almost every field. Using the dynamic characteristics of the TSE, the present works aims at developing a novel combinatorial approach for rapidly and efficiently assessing the processing-structure-property relationships for polymer nanocomposites. This approach is based on creating gradient architectures through step changes in the feed input. These gradient architectures are then predicted by convolving the step input with the Residence Volume Distribution (RVD) of the TSE process.
Causes of Melt Temperature Variatons Observed in the Nozzle during Injection Molding
Injection molders often assume that the temperature of the melt prior to injection is either equal to the barrel temperature or the temperature measured from a purge shot. Data obtained via an intrusive temperature probe in the nozzle showed a sharp increase in the melt temperature during injection followed by gradually decaying temperatures during holding and cooling. The effects that adiabatic compression, shear heating, and the initial thermal variation have on the observed temperature increase were determined through experimentation. It was found that adiabatic compression had a significant affect on the temperature increase, but the majority of the observed variation occurred as hot melt from the barrel flushed cooler melt out of the nozzle.
Comparing Laser Transmission Principles
In this paper simulation results of the simultaneous-, contour- and quasi-simultaneous laser welding processes will be presented. The calculations of this paper were performed by using a finite element analysis to understand the influence of the welding parameters: scanning velocity, frequency of scans, pressure and laser power. It will be shown how the process parameters affect the temperature distribution in the joining area. The FEA-model includes the heating phase and cooling phase and uses temperature dependent material data. Absorption in the transparent part and the convective cooling and emissivity at the surface of the weld interface were considered.
Analysis of the Effects of Fibre Surface Modification of Aramid Fibres in a Thermoplastic Matrix
Aramid fibers were subjected to a variety of surface treatments to improve the interfacial stress transfer between a thermoplastic matrix and the treated fiber composite. Analytical techniques to characterize the effect of surface treatment included DSC, Optical Microscopy, AFM and micromechanical analysis using Raman spectroscopy. Correlations between the different analysis methods were identified. It was found that plasma modified and chloride grafted fibers had the largest degrees of transcrystallinity, highest nucleation rates and greatest interfacial shear strength between fiber and matrix.
Development of a Head Pressure Index
Head pressure is a key extrusion variable. It is advantageous to know prior to extruding what the pressure will be because it affects safety, rupture disk rating, and vent flow. This paper describes development of a model to determine head pressure. The model is not intended to be highly accurate, but to provide a useful estimate. Therefore, the result is termed a head pressure index (HPI). Head pressure results from three process variables: melt viscosity, flow rate, and flow restriction. With the HPI, an operator can make quick decisions about operating conditions, such as acceptable screw speed, melt temperature, and vent location. Experimental data is shown that correlates HPI with measured head pressure.
Material Development on Flame Retardant Polyester Compositions with Improved Flowability
Polyesters are widely used in automotive and electrical industry parts due to their excellent electrical, mechanical and molding properties. However, as the industry is driving/evolving towards miniaturization of parts it is a challenge to develop polyester compositions with high flow properties in order to fill the thin wall molds/parts. Furthermore, flow improvement is more challenging in filled polyester compositions as these have substantially higher viscosity than corresponding neat polyesters. We reported last year a novel additive approach to improve flow properties of polyesters via reactive extrusion. In the present study, we discuss the development of new high flow polyester flame retardant compositions using extrusion process and flow additives. The correlation between standard viscosity measurements and spiral flow measurements in thin wall molds is also discussed. In addition spiral flow data at wide range of temperatures and thickness are also reported.
Robotic UV Curing: A Cost-Effective Way to Cure Large 3-D Plastic Parts
Plastic part manufacturers are paying more attention to UV curing as a means to produce their parts. The interest is driven by several advantages of UV:UV cure is fast. Coatings can be cured in a tiny fraction of the time needed for traditional cure systems.Little heat is required. UV curing relies on light energy and not heat to drive polymerization. This mechanism is ideally suited to temperature sensitive substrates.The UV process minimizes the emission of hazardous VOCs. Many popular plastic UV coatings are very high solids formulations with little or not solvent.UV formulations may exhibit superior properties. Many UV formulations are noted for high gloss, superior scratch and mar resistance -- properties often sought in plastic part manufacturing.While UV curing is new relatively new to the plastics market, it is the established way to cure coating materials. In graphic arts for example, many UV varnishes, inks and adhesives are cured with UV. DVDs are produced with UV bonding adhesives and often decorated with UV cured inks. Wooden flooring, optical fibers, and printed circuit board resists all use UV.But these parts are simple compared to most plastic parts. They are small, they are flat, or they are relatively simple shapes. The markets that have accepted UV have often been markets lending themselves to UV exposure by simple fixed lamps. Surely this has developed because without direct line of sight between the part surface and the UV lamp there can be no cure.For the last few years , as makers of large and complex 3D plastic and composite parts explored the UV option they found that the established techniques of placing fixed lamps end-to-end to be fraught with technical problems and high price tags. Many projects where the coating was developed and proven stalled when the price quotation for a system of 10, 15 or 20 or more UV lamps was presented.This paper describes recent developments using robotically actuated UV lamps to cure large and complex parts.
Super-Critical Carbon Dioxide Assisted Melt Intercalation of Polymer Layered Silicate Nanocomposites
Preliminary experiments were preformed to study the influence of super critical carbon dioxide (sc-CO2) on the melt intercalation (platelet dispersion and mechanical properties) of polymer-nanoclay composites. A series of mixing scenarios incorporating sc-CO2 and maleic anhydride in the melt compounding of polypropylene with organically-modified nanoclay were examined and compared to a commercially available polypropylene nanocomposite. The greatest mechanical property response was a result of the novel technique of directly and rapidly injecting pre-mixed sc-CO2 and nanoclay into the polypropylene melt during extrusion. X-ray diffraction data showed no characteristic peak for the nanoclay layer spacing in this method. The invented mixing technique showed a negligible influence on the rheological response, which was dissimilar to the commercially produced nanocomposite.
Ultrasonically Assisted Hot Plate Welding of Glass Fiber Reinforced Polypropylene
Short glass fibers are commonly added to polymers to enhance their properties. When joining these materials, it is desirable to maintain the enhanced characteristics of the bulk material at the weld interface by orienting the fibers perpendicular to, and across the joint. However, in most conventional plastics welding processes, such as hot plate welding, the glass fibers tend to orient themselves parallel to the weld joint.In ultrasonic (US) welding, mechanical vibrations are used to generate heat via intermolecular friction. These same US vibrations are also used in many other processing functions, including mixing.The concept of using US vibrations to mix glass fibers in a molten polymer was considered as a possible solution for forcing glass fibers to bridge weld joints in hot plate welding applications. An investigation of the morphological and weld tensile strength properties resulting from the incorporation of US vibrations and the hot plate welding process was evaluated.
Phase Morphology and Orientation Development of PP/Ethylene Butene Copolymer Blends in Melt Processing
Phase morphology development of the iPP/EBM blends in both extrusion and melt spinning was studied. With an increase of shear rate or draw down ratio, the dispersed iPP droplets were stretched into long fibrils, subsequently began to accumulate at the surface, producing a smooth surface. We found that 1-20wt% of isotactic polypropylene (iPP) could largely decrease the birefringence of melt spun ethylene butene copolymer (EBM) fibers. Because iPP crystallizes much earlier than EBM, after crystallization the iPP surface will exert most of the spinline stress, which leads EBM to crystallize at much lower stress and to show lower birefringence.
Comparison of Carbon Nanofibers and Activated Carbon on Carbon Dioxide Foaming of Polystyrene
Carbon nanofiber and activated carbon particles are two forms of carbon with different shape and surface properties. These two carbon materials are used as additive/nucleation agents in polystyrene extrusion foaming. Activated carbon particles with different moisture contents are used to investigate the effect of moisture as the co-blowing agent on the finished foam products. Carbon dioxide is used as the blowing agent. Morphology and thermal properties of extruded foams are reported and compared with the characteristics of these two additives.
Micropatterning Poly(Acrylamide) on PLA Films Using Photolithography
Micropatterning is a robust tool to surface-modify bioplastics like poly(lactic acid) (PLA) for biomedical applications. We used a sequential two-step photografting and photomask approach to micropattern poly(acrylamide) (PAAm) on PLA film. In step one, a PLA specimen, dip coated in benzophenone solution in ethanol covered with the photomask, was sandwiched between two glass plates and exposed to UV in an inert atmosphere. In step two, benzophenone-micropatterned film was immersed in 10% v/v monomer solution in water and exposed to UV for 3 h to grow poly(acrylamide) (PAAm) from the film surface. The resultant film surfaces were examined by AFM and optical microscopy, which revealed the resolution and acuity of the micropatterns.
Towards Lower Crystallization Temperatures in Polyethylene
Recent advances in experimental techniques such as rapid cooling, droplet crystallization and in-situ light scattering have made it possible to extend the crystallization range of polyethylene to temperatures as low as 90-75°C. The current study reports the development of a simple, yet effective technique that allows quench-crystallization at unprecedented low temperatures in the neighborhood of 30°C. The veracity of this claim is supported by slope analysis of cooling curves, lamellar thickness and crystallinity measurements as well as melting studies using SAXS, wide-angle XRD and DSC respectively. The results indicate that this technique has made it possible to crystallize HDPE over a series of hitherto unreported temperatures ranging from 30-70°C corresponding to lamellar thickness of 67-100Å respectively. At the temperatures being reported, linear PE is expected to exhibit growth rate kinetics consistent with the diffusion controlled region of the growth rate-temperature curve, something that has never been demonstrated to date.
Estimation of Bulk Melt Temperature from In-Mold Sensors: Part 2 - Convection
An analytical approach for estimating the bulk melt temperature within a mold cavity using data from in-mold temperature sensors has been further developed. The analysis uses a convective boundary condition to approximate the contact resistance of the mold-melt interface. The measured mold coolant temperature was also taken into account. The accuracy of the predictions was tested over a wide processing window. While most trends were correctly predicted, the magnitude of the predictions varied greatly due to the high sensitivity of the analysis to the temperature measurements.
A Non-Newtonian Model of Flow in a Special Mixing Element Region of a Modular Intermeshing Corotating Twin Screw Extruder
The flow of non-Newtonian fluid in screw and kneading disk block regions of an intermeshing co-rotating twin screw extruder has been analyzed by various investigators using different methods for non-Newtonian flow models. New types of new special mixing elements have been developed and frequently used in the polymer industry. The fluid mechanisms and pumping characteristics of these elements needs to be better understood. The screw characteristic curves of special mixing element were calculated and compared with other traditional screw and kneading disk blocks.
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