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.
This paper presents an investigation of the effect of mixing natural Jute fibre and Maleic Anhydrite compatibilizer with recycled Polypropylene (PP) and Polyethylene terephthalate (PET) blends. Recycled plastic has a significant contribution to reduce the environmental issues and encourage the economic benefit. PP and PET polymers are commonly used in the industrial fields, however, they are immiscible and it is difficult to be blended. Two different PP & PET (65/35 and 78/22 v/v %) samples have been blended with 0.5% wt (2 g) Jute fibre and 5% wt (20 g) Maleic anhydride (PP-g-MAH). The mechanical mixing has been done by using twin-screw extruder to get pellets of PP/PET/jute/Maleic Anhydrite, which were used to make test samples with injection moulding machine. The comparative result shows that blend of PP/PET with and without any addition of Maleic anhydride and Jute fibre has enhanced tensile and flexural properties significantly.
With induction heat/cool mold technology it is possible to reach mold temperatures effective for low and high melting polymers with precise temperature control during the injection stage of a molding cycle. This results in enhanced flow behavior of the resins enabling, among others, thin wall molding, enhanced surface replication and generally improved part performance. There is a need to better quantify these effects for various resins. The High Definition Plastics database offers central storage for these quantified benefits according a standardized method and allows easy material selection for a specific design or purpose.
This paper investigates the fabrication of micro-molded features using Moldflow analysis to optimize processing parameters. Melt temperature, mold temperatures, injection velocity, and packing pressure were all examined to help understand the process of microinjection molding. Micro pillar type features with different cross sectional shapes, diameter, and height were investigated using Moldflow® analysis to optimize filling. Critical processing parameters were identified for common thermoplastic polymers such as Polystyrene (PS) and Thermoplastic Polyurethane (TPU).
As per Vikram Bhargava's request I am submitting this abstract as an Invited Speaker. Thanks.A robust process produces parts that are consistent in quality cavity to cavity, shot to shot and run to run despite the natural variations such as that of the machine, material, environment and the operator. A capable process produces parts that are consistent within the required quality requirements. Both these are a requirement for a successful molding operation. To reach to this success, the part design, the mold design, the mold build, the machine selection and the molding process need to be considered all at one time right at the start of the project. Unfortunately, in most cases, a designer designs the part, throws it over the wall to the mold maker who makes the mold and throws it over the wall to the molder who then ends up with a substandard process with several quality issues. The talk will focus on how and why to apply concurrent engineering principles for the success of a project.
What you didn’t think was possible with Automatic Water Flow Control. Previous methods of water flow control have proven themselves beneficial to the molding process but come with a series of headaches between setup and monitoring. Automatic water flow control is the next wave of technology in the molding industry. Imagine being able to reap the benefits of water flow control without all the hassle.The key advantage of automatic water flow control over a manually adjustable one is that it permits continuous electronic monitoring and automatic adjustment of proportional control valves to meet preset flow and temperature values. All data can be logged. Already proven in service many times over, the WITTMANN fine regulating valve of the 301 Series performs flow regulation. Generously dimensioned channels in the casing blocks guarantee the lowest possible pressure loss and high flow rates.The net benefit is being able to easily balance temperature and flow through complex tooling pathways, bubblers, thermal pins, conformal cooling and of the like. This leads to a much higher level of process repeatability because an automatic regulator reacts much quicker and with a higher accuracy than most temperature controllers, as well as provides zone control of the tool. A technician can balance the tool to avoid shrinkage or warpage in trouble areas of the tooling, and even balance fill rates. Another benefit is that once you’ve qualified the mold with certain temperature and flow settings, those setting can be saved, allowing an easier setup of the mold. Likewise all of the processing data on the machine for zone temperatures and flows can be tracked. Working with a multi-cavity tool? Great because automatic flow control ensures uniform cavity filling due a modifiable heat profile throughout the mold and it’s cavities. Lastly, if there is degradation in flow due to a blockage or restriction, the system will identify this, its location, and indicate to the operator that there is a problem. This allows a technician to proactively clean a cooling channel before a failure occurs.
The processability of injection molding ultra-high molecular weight polyethylene (UHMWPE) was improved by introducing supercritical nitrogen (scN2) or supercritical carbon dioxide (scCO2) into the polymer melt, which decreased its viscosity and injection pressure while reducing the risk of degradation. When using the special full-shot option of microcellular injection molding (MIM), it was found that the required injection pressure decreased by up to 30% and 35% when scCO2 and scN2 were used, respectively. The mechanical properties in terms of tensile strength, Young’s modulus, and elongation-at-break of the supercritical fluid (SCF)-loaded samples were examined. The rheological properties of regular and SCF-loaded samples were analyzed using parallel-plate rheometry. The results showed that the use of scN2 and scCO2 with UHMWPE and MIM retained the high molecular weight, and thus the mechanical properties of the polymer, while regular injection molding led to signs of degradation.
In this paper, an ultrasound-aided ejection system was designed and tested for various polymers and mold topographies. The use of ultrasound vibration aims at decreasing the ejection friction by reducing its adhesion component, which is controlled by the real contact area developed in the filling phase of the injection molding process. The experiments indicate that the ultrasound vibration reduces the ejection friction up to a maximum of 16%. The effect depends on the polymer used and it increases for rougher mold surface. Moreover, the dependence of ejection friction on mold surface roughness, melt viscosity and elastic modulus at ejection was modeled using the experimental data.
In this study, mold filling simulation crystallization data were compared with experimental data collected with a fast scanning chip calorimeter. This new technique gives the opportunity to collect data at higher cooling rates, which mimic the injection molding process. Experimental data showed that the crystallization temperature depends on the cooling rate, which is neglected in previous models implemented in the simulation software. It is suggested to modify the simulation software crystallization data in order to account for more realistic prediction of the crystallization process and, consequently, microstructure formation affecting properties.
Thermoplastic prepregs that are also known as organo sheets are processed in presses and formed to half shells. Larger components can be produced by joining the half shells, which results in hollow bodies. However, current manufacturing technologies allow only cap profile shaped joints, which cause fiber deflections in the joint plane. This paper shows that overlapping infrared welds in organo sheets enable weld strengths close to the interlaminar shear strengths of the unwelded materials and thus a fiber utilization across the joint plane. By using high welding pressures, a matrix depletion and a change of the fiber alignment in the weld plane may occur which causes low weld strengths. Therefore, criteria for the successful welding were defined various possibilities to the optimization of the weld strengths were investigated.
A newly developed material known as Stylight has been created for design flexibility and lightweighting solutions. Stylight incorporates carbon and glass fibers in an SAN (amorphous polymer) matrix. The SAN matrix allows for a smoother "Class A" finish than traditional thermoformable composite sheets that are normally used hidden structural applications. The glass and carbon fiber also help provide a rigid and tough backbone for structural applications as well. Stylight also provides design flexibility and is able to be painted or covered in decorative film or used with carbon weave pattern.
Beside the economical production of bipolar and heat exchanger plates made from graphite composites, the stack assembly is of great importance for the further technological development of fuel cell, redox-flow battery and heat exchanger systems. In order to choose a suitable welding method, to evaluate the weldability of the composites and to produce a secure stack assembly, a comprehensive understanding of the welding behavior of the materials is required.This work focuses on the welding of graphite composites using the infrared welding method. To form a material-locking joint during the welding process, a defined melting of the material in the joining area is decisive. Due to the thermal properties of highly filled graphite composites, the welding process differs fundamentally from conventional welding of unfilled or low-filled thermoplastics.To perform a scientific examination of the material heating depending on the heating source, a surface and a contour-following infrared radiator were used. Independent of the radiator type, no high-quality joining connection could be achieved. Due to the high thermal conductivity and the low heat capacity of the graphite compounds, the joining area does not have a sufficiently high temperature after infrared heating. Furthermore, it is not possible to apply a sufficiently high joining force, as deep material heating takes place. As a result, the formation of a material-locking joint is significantly impaired with an increasing graphite content.
This research focuses on the characterization of bioplastics joined using ultrasonic welding and modeling of temperature distributions and interfacial healing. Polylactic acid (PLA), which is typically derived from starch-rich crops such as corn, was studied. While the measurement of activation energy for interfacial healing at weld interfaces of PLA films has been reported, here, this information is used to predict the weld strength of rigid PLA samples welded by ultrasonics. A characterization of the mechanical properties was completed with a tensile test to determine the effects of amplitude, weld velocity and collapse distance on weld strength. From previous interfacial healing activation energy measurements based on an impulse welding method, it was also possible to predict weld strength. It was found that the most influential parameters were weld time, collapse distance and weld velocity. In general, the model predicted weld strength reasonably well with r2 values between 0.77 and 0.78.
Friction Riveting is an innovative and promising joining technology, which can potentially fulfill the industry requirements for sustainable and efficient systems. The objective of this work is to prove the feasibility of Direct-FricRiveting by inserting a metallic rivet through metal-composite overlapped plates and subsequent anchoring in the composite part, which is a challenging configuration with limited knowledge available. The case-study joint configuration used in this work comprised a Ti6Al4V rivet, which joined an overlapped AA2024-T3 upper plate with a 30% short-carbon-fiber-reinforced poly-ether-ether-ketone lower plate, material combination of high interest for the aircraft industry. Evaluation of joint formation, temperature development, microstructural and physicochemical changes in the composite, and mechanical properties were carried out for joints produced under low and high energy input. The feasibility was proved, showing satisfactory mechanical performance under lap shear testing (up to 7 ± 1 kN). Changes of polymer crystallinity and thermo-mechanical decomposition in the composite were shown not to affect the joint mechanical performance and failure behavior, while the plastic deformation at the rivet tip played the major hole. The knowledge gathered in this preliminary work will be further applied to optimize the process, contributing to the development of the Friction Riveting technology and improvement of its industrial applicability.
Ultrasonic welding is an efficient technique for rivetless assembly of thermoplastic composites. To further improve this process, it is necessary to develop numerical simulations. A phenomenon often misevaluated but crucial for accurate process simulations is hammering. It is the loss of contact between sonotrode and upper adherend during the vibration phase. The goal of this paper is twofold: present an experimental procedure to measure the displacement of the sonotrode and upper adherend during welding, and discuss two strategies to quantify amplitude transmission to the upper adherend. This will lead to improvement of predictive models for ultrasonic welding and closer agreement with experimental data.
Laser transmission welding is a complicated process with the coupling effect among the unsteady and uneven temperature field, mechanical force, stress and strain and plastic forming flow. The theory based on the ideal contact surface has not satisfied the requirement of practical production. In this paper, the mathematical model of surface roughness profile was built based on Weierstrass-Mandelbrot (W-M) fractal function, the contour welding process for polycarbonate (PC) was simulated with the idea taking real 3-D topography of contact area into account and the effect of laser scan power on the surface topography with different surface roughness was discussed, a combination of a rotary Gaussian volumetric heat source with a Gaussian distribution of surface heat source was proposed. Finally, finite element simulated results agree well with the experiments in contour welding with PC. The experimental study indicates that the laser absorption rate, the welding temperature and the variation of temperature gradients of rough surface are lower than the smooth one.
According to the theory of laser transmission welding (LTW), a 3D transient finite element temperature field and fluid field coupling model based on volumetric heat source and melting and solidification model were built. The moving volumetric heat source of laser transmission welding and boundary conditions were implemented by programming user-define function file written by C language. The temperature filed and fluid field were obtained considering the influence of clamping force. Then distributions of temperature and fluid in heat affected zone were analyzed. The results show that the heat affected zone of opaque part is bigger than that of transparent part. The node of peak temperature is under the weld bead and lags behind the center of laser beam. In the molten pool, the higher the temperature is, the faster the fluid flows. In the Y-Z and X-Z plane, fluid flows to the solid liquid interface and forms two vortexes. Temperature field and velocity field simulation will help to guide and study on laser transmission welding process.
This work investigates the potential of the Weld-Bonding concept to improve the fatigue performance of friction spot joints. Therefore, friction spot joints of AA2024-T3/CF-PPS (carbon-fiber-reinforced polyphenylene sulfide) were produced with an additional thermoplastic film interlayer. Two joining conditions manufactured with low and high heat inputs were investigated. The fatigue performance of those joints was evaluated at 35%, 50% and 75% of their respective ultimate lap shear force (ULSF). It was observed that process-related microvoids decreased the fatigue strength of the joints in high cycle fatigue (HCF). Superior fatigue life of the joints with interlayer in comparison with those without interlayer was observed. At 105 cycles, typical qualification requirement of the aircraft industry, the interlayer joint showed fatigue strength of 51% of ULSF, whereas the fatigue strength of the joint without interlayer was 37% of ULSF. In the whole spectrum, the joint with interlayer showed a fatigue life approximately four times higher than the joint without interlayer.
Due to the rising demand of lightweight constructions as well as saving material, the density and weight of thermoplastic parts can be influenced significantly by using the thermoplastic foam injection molding process. The characteristic three-layer structure which is originated by the foam injection molding, a microcellular foamed core is surrounded by a non-cellular skin layer, results in a weight saving and leads to an increased specific bending stiffness with a simultaneous low tendency to warp. Whereas the established welding processes for solid parts have already achieved a high degree of perfection within the last decades, the joining of microcellular thermoplastics is a novel. The structure as well as the remaining foaming agent within the part represents a challenge for welding, which can cause great difficulties in the process. Unfortunately, there are no standards or experiences for welding such foamed parts yet.The present investigation researched the welding behavior of foam injection molded parts in comparison to their solid counterpart in dependence on fiber reinforcement and joint type. In contrast to solid parts, the welding behavior shows a significant time-dependence in case of foam injection molded parts for the various materials.
Fusion deposition modeling of PLA was studied to determine the effect of build orientation and fill-level on mechanical properties of tensile test samples. This was used to assist in the design and FDM manufacture of airless tires for the NASA rover competition. It was found that the failure and energy at break increased with increasing fill-level for flat built tensile samples, and there was evidence of crazing prior to failure. For the upright built tensile samples, the effect of fill-level on failure load and energy at break was small for fill-levels between 20% and 80%, with large increase for fill-level of 100%. However, for all fill-levels for the upright build samples, the failure load and energy at break were much lower than for the flat build samples. For tire types, the threaded tire in the upright build orientation has the highest failure load with the lowest deflection.
Many technologies exist for joining plastics, and each process has its advantages and compromises. Processes are selected based on the application and customer needs. This presentation examines vibration welding and compares it to Clean Vibration Welding (CVT), also known as vibration with infrared pre-heat. Vibration welding offers excellent strength, process speed, material compatibility, and the ability to weld large parts. However, vibration alone uses friction and high forces, resulting in particulate and unsightly “flash.” CVT adds an IR preheat step to create molten plastic prior to the vibration welding. The result is a cleaner joint with virtually no particulate, which allows more three-dimensional design flexibility and is ideal for applications with aesthetic requirements. Through material testing in a laboratory setup, engineers from Emerson demonstrate the results of CVT welding found on Branson products, and established a relationship between “changeover time” and weld appearance.
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