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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Influence of Process Parameters on the Weld Lines of a Micro Injection Molded Component
The insufficient entanglement of the molecular chains and the stress amplification at the v-notch of a weld line compromise the mechanical strength of a plastic product, also in the micro scale. To investigate the influence of process parameters on the weld lines formation, a special micro cavity was designed and manufactured by ?EDM (Electro Discharge Machining). Weld lines were quantitatively characterized both in the two-dimensional (direction and position) and three-dimensional range (surface topography characterization). Results showed that shape and position of weld lines are mainly influenced by mold temperature and injection speed.
Laser Transmission Welding of Electro-Pneumatic Valves
Laser welding has proved an appropriate method for joining plastic parts. The increasing trend towards greater freedom of design, integration of ever more functions, and therefore more complex modules is putting increasing pressure on joining technology, and is thereby promoting the development and introduction of novel technologies.Laser welding of plastics is a suitable complement to established joining processes, and thereby opens up new fields of application. This has been demonstrated by numerous applications for small and even for larger components.Compared to alternative joining methods the contact free method has the advantage that hardly any flash or no flash is being produced, which means that joints with a high quality visual appearance can be produced. The laser is clearly superior to alternative processes, even for joining 3D geometries produced by coupling to a robot. The heat-affected zone is only a few #m deep and reduces the risk of surface flaws.The following paper is a case study for the introduction of the Laser welding process for electro-pneumatic valves. It describes the process development from the initial tests to the In-Line integration in mass production.
Birefringence Distribution in Gas-Assisted Tubular Injection Moldings: Simulation and Experiment
Measurements and simulation of three birefringence components and of the gas/polymer interface distribution in gas-assisted injection molding (GAIM) of a tubular geometry are presented. The governing equations of the process are derived using a nonlinear viscoelastic model and solved using a hybrid finite element/finite difference/control volume method (FEM/FD/CV). The measurements were carried out on polystyrene moldings before and after annealing. Simulation and experimental results indicate that the birefringence is high in the gas penetration region and low in the region where the gas did not penetrate.
Radiation Cross Linking Engineering Thermoplastics for Tribological Applications
Electron beam irradiation primarily leads to cross linking in the amorphous fraction of semi-crystalline thermoplastics. As a result, there is a change in morphology and an improvement in mechanical and thermo dynamical properties. This effect can be utilized for tribologically stressed parts as micro parts and gear wheels. These parts feature an unfavorable relationship of part/volume leading to a disadvantageous formation of morphology and crystallinity. Experimental work shows the potentials of radiation cross linked polyamides. Due to cross linking in particular the thermal-mechanical and tribological properties are shifted into a range, which enables the employment of this substrate for application at elevated temperatures. Furthermore, the investigations on PA6 and PA66 show that a lower crystallinity degree leads to better results of cross linking via electron beam radiation and to an improvement of abrasion resistance.
Failure Analysis and Prevention – A New European SIG
The new European Failure Analysis and Prevention Special Interest Group (FAPSIG) is creating a database with failure cases. The members share this database and contribute with their own failure investigations. The two main groups are Failure Causes and Failure Mechanisms. Failure Causes are subdivided in: Stress concentrations, low mass and/or mould temperature, highly stressed weld lines, faulty ribbing; too high stiffness of construction elements, incorrect joining, and incorrect material selection.Failure Mechanisms are subdivided in: Creep and stress relaxation, wear, fatigue, UV degradation, chemical attack, environmental stress cracking.The paper will present some examples for designers of plastic products.
Measurement of the High Frequency Viscoelastic Properties of Polypropylene Using a Sliding Plate Rheometer
A newly constructed sliding plate rheometer (SPR) is used to investigate the high frequency linear viscoelastic properties of two polypropylene (PP) resins with widely differing melt flow rates. Extrapolation of rheological measurements obtained on a traditional parallel plate rheometer to frequencies obtained on the SPR, through use of the generalized Maxwell and Cross models, was used to assess the performance of the high frequency SPR. Good agreement between the extrapolated and measured data demonstrates the ability of the SPR to measure the high frequency rheological properties of PP.
Development of Rubber Mould Inline Process and Offline Process Inspection by Touch Probe
Development in design of mould using reverse engineering can reduce lead time and increase the quality of mould inspection. For two methods used: touch probe on machining center and portable arm coordinate measuring machine, these are used along software that is capable of measuring three-dimensional coordinate and analyzing the results. The first inspection is done on the machine during production (inline) then another is examined after production (offline). The experiment result demonstrates in terms of accuracy there is no significant difference between two measurement methods. Nevertheless, the portable arm CMM has an advantage in its simplicity, and require less operation and lead time.
Optimization of Quality and Throughput at Low Revolution Speeds in an Advanced Two Stage Compounding System
Melting and incorporation of high viscous particles into a low molecular matrix is a difficult process due to differing requirements for melting and homogenizing. Melting is preferably done by using high shear rate and stress in combination with a small residence time. These facts lead to a fast turning small machine. Homogenizing on the other hand requires elongational flow, high viscosity and a significant amount of residence time which leads to a low revolution speed. By using a two step compounding system one can meet the differing constraints at the same time. Optimization of efficiency in pressure build-up can be done effectively by using state of the art CFD calculation methods.
Numerical Balancing of Coextrusion Dies : A Validation Study with a TPV-Based Hose
In some industrial applications, like hydraulic hoses, a two-layer structure may be produced from the coextrusion of a soft Engineering Polyamide Alloy and a Thermoplastic Vulcanizate (TPV), like Santoprene™ Thermoplastic Rubber. As the inner layer, the polyamide component provides a barrier against oil at high temperatures; the TPV provides flexibility, resistance to abrasion as well as adhesion to the inner layer.Reaching a die design that yields the required concentricity and homogeneous material distribution in each layer is a challenge. The following two-step approach is here proposed. First a 3D numerical simulation using the POLYFLOW code confirms the current unsatisfactory extruded profile quality. A second extrusion simulation is next carried on a modified geometry to ensure proper flow balancing. A validation is performed for the coextrusion of a relevant Thermoplastic Rubber grade compatible with an Engineering Polyamide Alloy.
Heat-Aging Performance of Metallized Thermoplastics for Automotive Lighting
Driven by weight savings, design freedom, manufacturing economics and pedestrian impact considerations, the use of plastics in automotive lighting has grown over the last decade to include all aspects of forward and rear lighting. Among these is the use of plastics in reflector applications where the molded plastic part is metallized, heated and expected to maintain high reflectivity and tight dimensional stability over time at use temperatures. In addition to the thermal properties of the plastic, other factors can affect the use temperature in such an application. The effects of metallization conditions, moisture and post-metallization aging are discussed as they affect the use temperature of a variety of high temperature thermoplastics.
Synergistic Effect of PP-g-MA and SEBS-g-MA on Polypropylene-based Wood-Plastic Composites Reinforced with Nanoclay
In this study, polypropylene grafted maleic anhydride (PP-g-MA) and styrene ethylene-co-butylene styrene block copolymer grafted maleic anhydride (SEBS-g-MA) were employed as coupling agents for polypropylene-based wood-plastic composites containing 50 wt% wood flour. Adding PP-g-MA to wood flour increased the tensile strength of the wood-plastic composite (WPC) by 60% and the reversed-notch Izod impact strength by 100%; the modulus remained essentially unchanged. By contrast, SEBS-g-MA had a greater effect on the impact strength but a smaller influence on the tensile strength; in addition, the modulus was reduced. On adding both PP-g-MA and SEBS-g-MA to the WPC, the impact strength increased by a factor of more than 2.5, but the tensile strength was not reduced. Since the incorporation of nanoclay increases the modulus of WPCs without decreasing the impact strength, the use of all three additives affords the possibility of manufacturing WPCs with high modulus and high impact strength.
Thermal Stability and Rheological Properties of Multiwall Carbon Nanotube Reinforced Thermotropic Liquid Crystalline Polymer Nanocomposites
Multiwall carbon nanotube (MWCNT) reinforced thermotropic liquid crystalline polymer (TLCP) nanocomposites were prepared by a melt compounding process. Incorporation of small quantity of the MWCNT improved the thermal stability of MWCNT reinforced TLCP nanocomposites. The rheological behavior of TLCP/MWCNT nanocomposites was dependent on the MWCNT content. The complex viscosity and storage modulus of TLCP/MWCNT nanocomposites increased with increasing MWCNT, resulting from physical interactions such as the nanotube-polymer matrix interactions and the nanotube-nanotube interactions. This increment effect was more significant at lower frequencies.
Experimental Investigations on the Plasticating Process of Polymers in a Short Single Screw Extruder and Energy Efficiency of the Process
In comparison to normal single screw extruders, the short extruder has completely different screw and barrel geometries that allow the plasticization of polymers over a very short screw length (L/D < 5). Experimental investigations demonstrated the influence of screw speed, throughput and die pressure on the plasticization process. Due to the fact that this extruder does not require external heating, except heating of the die, a characterization of the operating point is carried out with help of an energy balance of the extruder.
Numerical Simulation and Experimental Investigation on Parison Formation from a Varying Die Gap in Extrusion Blow Molding
The use of simulation software to predict the process of blow molding can save considerable time and money in the product development and is becoming more widespread. However, for parison formation simulation, the current finite element (FE) software is suitable only for the situation where the die gap is fixed. In this work, a new method was proposed to apply the FE simulation to the varying die gap parison formation. In order to evaluate the availability of the new method, the predicted parison thickness distributions were compared with the experimental results. It is demonstrated that the new method has certain accuracy and reliability in predicting the parison thickness from a varying die gap.
Experiments with Combined Ultrasonic and Laser Embossing of Microchannels in PMMA
MEMS and micro-fluidic technology are two of the fastest growing areas of micro and nanotechnology. The rapid fabrication of micro features is crucial to their continued growth. Previous studies of through transmission laser embossing showed that it produces high accuracy replication but there are difficulties with de-molding. Previous ultrasonic embossing studies showed that it produced rapid heating and the ultrasonic afterburst was effective for de-molding without damage to the part or mold. By combining ultrasonic with laser embossing we take advantage of the high precision of laser embossing with the rapid initial heating and ease of de-molding using an ultrasonic afterburst.
Non-Isothermal Crystallization Kinetics of Polypropylene – The Use of a Modified Kissinger Method
Kissinger method of kinetic analysis was modified for crystallization of polymer from melt to include both the uncrystallized concentration and differential temperature as the driving forces. The modified expression allowed an apparent energy presumably related to the growth behavior of the crystalline structure to be determined. From non-isothermal crystallization data the apparent energy of a polypropylene copolymer increased moderately from 2.98 to 3.44 KJ/mole as the talc content increased from 0 to 1%. The variation of apparent energy was correlated with the Avrami and Ozawa exponents. Both the modified Avrami exponent and the Ozawa exponent measured at Tc increased with talc content and cooling rate suggesting the increase of complexity in nucleation and growth due to talc.
Nonwetting Low Friction Nylon 6/ Polyhedral Oligomeric Silsesquioxane (POSS®) Hybrid Nanocomposites
Hybrid polymer nanocomposites based on polyhedral oligomeric silsesquioxane (POSS®) molecules with improved surface properties are of interest for a wide range of engineering applications. POSS molecules exhibit remarkable ability to modify polymer surfaces. Nylon 6/POSS Nanocomposites based on two different classes of POSS, a closed cage octaisobutyl POSS and an open cage trisilanolphenyl POSS, were prepared via extrusion. Surface topography and friction properties were evaluated utilizing atomic force microscopy. Contact angle investigation reveals enhanced hydrophobicity. Relative surface friction of Nylon 6 was also reduced by 45% by the appropriate selection of POSS molecules.
Plastics Industry: The Ability Age
The American plastics industry is in the Ability Age created by outsourcing, industry consolidation, the power of Wall Street, the Information Age, and dynamically changing rules and environments.The challenges of this age are continually making right decisions and providing leading global valued growth while facing dynamically changing rules and environments. The opportunity of this age is having sufficient resources and information to act quickly.Coming from this age will be a new set of hypotheses aimed to continually make right decisions and provide leading global valued growth. One such hypothesis on using internal emerging technologies to lead outsourcing is proposed in this paper.
Crystalline Polymer Microgels with Surface Interactions
We report one rheological and microstructural investigation of dispersions of polyethylene microgels in squalane. Emphasis in literature has mainly been limited to systems that depend largely on polymer-solvent interactions and little is known of systems that exhibit both intra- and inter-particle crystallinity. The majority of similar reported systems are prepared using a bottom-up approach while the described system is prepared from recycled bulk XLPE via mechanical grinding and fragmentation by sonic energy. Bulk rheological properties and particle surface interactions are explored using conventional rotational and oscillatory rheometry.
Effect of Nano-Clay on the Microcellular Structure and Properties of High Internal Phase Emulsion (HIPE) Foams
High internal phase emulsion (HIPE) polymerization foaming process is controlled for production of novel foams with various microcellular structures and morphologies. In this study, organoclay, C10A and C20A and natural clay, Sodium montmorillonite (NaMMT) was introduced at different concentrations to control the microcellular morphology, cell size and open cell content. Scanning electron microscopy was used to observe the microcellular morphology and open cell contents, volume expansion ratio and cell sizes where evaluated. It was found that the open cell content increased as organoclay content increased, due to lowering the viscosity ratio of dispersed to continuous phases due to the addition of high molecular weight clay into the oil phase of emulsion. A correlation for the open cell content and volume expansion ratio depending on clay content was attempted and the result was quite satisfactory.
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