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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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Injection Molding

Monitoring Of Injection Molding Process With Piezo-Electric Sensor
Mostafa M. Pasha, Kyehwan Lee, Heinrich Foltz, Jesus Valladares, June 2022

Injection molding is one of the most popular techniques for global plastic production. With this automation technique, the plastic products can be manufactured at low cost with a complex geometrical shape. A manufacturing process with high productivity of an injection molding machine depends on optimized injection molding parameters. Injection molding pressure and temperature inside the mold cavity are the most critical parameters. However, cavity pressure transfer is not used due to cost and maintenance issues. During this research, an experimental procedure is performed to determine a process monitoring system using asynchronous data acquisition, through the incorporation of a wired piezo-ceramic sensor to acquire pressure of the injection molding system. This piezoelectric sensor is designed in such a way that, a Bluetooth device can be connected with a sensor and can take live data reading of parameters from the running molding machine.

Density-Based Analysis Of Polymers Using Magnetic Levitation Device Constructed By Magnet Arrays
Peng Zhao, Jun Xie, Yuhan Jia, Lih-Sheng Turng, June 2022

Standard magnetic levitation (MagLev) device consists of two identical square permanent magnets with like poles facing each other. Limited by the size of the permanent magnet, standard MagLev device cannot levitate samples with large size. This paper proposed a novel MagLev device using magnet arrays, which can accommodate large-scale samples. Unlike magnet arrays in previous studies, all magnets employed herein face the same direction. The magnetic field generated by the magnet arrays is similar to that of the standard magnet. Within the magnetic field induced by the magnet arrays, the polymer can be levitated to an equilibrium position in a paramagnetic solution and the levitation height is related to its density. The equation correlating density and levitation height can be obtained according to the simulation results. Solutions of different concentrations were used to measure densities of a variety of polymers with an accuracy of ±0.0003 g/cm3. The non-destructive testing could also be used for plastic parts based on its posture (orientation) within the paramagnetic solution. The use of magnet arrays circumvents the trouble of manufacturing large magnets, realizes testing of polymers/parts with large sizes, and facilitates industrialization of magnetic levitation detection.

Zirconium Dioxide As A Thermo-Insulating Coating For Molds In Plastic Injection Molding
Anatoliy Batmanov, Vanessa Frettloeh, Ruben Schlutter, Frank Mumme, Paul Ditjo, Ivan K. Kibet, Juergen Wieser, June 2022

Effect of the thermal barrier coating (TBC), deposited on the mold for plastic injection molding was investigated. The mold cavities were coated by yttrium stabilized (YSZ) and phosphorous doped (PDZ) zirconium dioxide as multilayer film using chemical vapor deposition (CVD) method. It was found that films deposited at higher temperatures have better thermo-insulating properties than films deposited at lower temperatures. Growth rate and film porosity increase as deposition temperature increases. It was observed that the TBC slightly affects the flow length of the plastic melt but improves the filling ability of poorly vented molded part areas.

Injection Molidng Of Microporous Ultra-High Molecular Weight Polyethylene
Huaguang Yang, Lih-Sheng Turng, June 2022

Microporous ultra-high molecular weight polyethylene (UHMWPE) parts were produced by microcellular injection molding (MIM) technology, which enabled higher production efficiency and lower part cost compared to the traditional powder sintering method. The microstructure could be tuned by adjusting the shot size to produce either sandwiched solid-skin – porous-core – solid-skin parts or open porous parts. The pore morphology, average pore size, pore size distribution, and pore density were characterized, and the water contact angle (WCA) and degree of oil-water separation were determined. The part weight reduction of open-porous UHMWPE and sandwiched UHMWPE parts were 16.5 wt% and 11.8 wt%, respectively. The WCA results showed that the porous surface transformed molded UHMWPE samples from being hydrophilic (34.5°) to hydrophobic (124.6°). Furthermore, the open-porous structure exhibited good oil water separation capacity. Tensile tests were carried out to study the effect of morphology on the mechanical performances of the molded UHMWPE parts. The characterization shows that a possible application for the sandwiched UHMWPE parts could be as a bone replacement material because of its high mechanical performance, and an application for the open-porous UHMWPE is as a functional filter material due to the fine pore size and high pore density.

Pressure-Controlled Injection Molding Of Recycled Polyolefins
Joshua Krantz, Peng Gao, Zarek Nieduzak, Elizabeth Kazmer, Olvia Ferki, Margaret Sobkowicz-Kline, Davide Masato, June 2022

The importance of utilizing recycled materials to manufacture plastic products has been a topic of great interest due to the environmental repercussions. Processing issues arise from the usage of these resins due to the variation in their molecular weight and rheology. In this work, pressure-controlled injection molding is evaluated and compared against conventional velocity-controlled injection molding. The effects of injection velocity, mold temperature, and pressure on part shrinkage and mechanical properties of injection molded parts fabricated with post-consumer film-grade polyethylene were evaluated. The experimental results show that the different processing techniques significantly affect the mechanical properties and part shrinkage for both materials. Additionally, different levels of injection pressure and velocity significantly affect the shrinkage of the plastic parts. Moreover, it was seen that parts fabricated using pressure-controlled injection molding had preferable overall quality.

Evaluation Of Component Specifications Of Largeformat Plastic Products Through The Use Of Machine Learning Methods
Michael Werner, M.Eng., Prof. Dr.-Ing. Thomas Seul, Prof. Dr.-Ing. Michael Gehde, Prof. Dr.-Ing. Andreas Wenzel, Norbert Greifzu, M.Sc., Markus Lehr, June 2022

This conference paper presents the investigations, results and findings from the research project "Tool-integrated assistance system for production control of highly complex and demanding component specifications" (acronym in German WASABI). The project investigates the possible use of sensor technology in combination with machine learning methods for the prediction of quality-determining component features on large-format plastic products. Furthermore, the information obtained will be used to propose target-oriented recommendations for action based on the predicted feature characteristics. An outer skin component (bumper) from the automotive sector was defined as the reference product for the investigations into the prediction possibilities of demanding component specifications. The injection molding tool required for production was designed as part of the project work and equipped with a variety of different sensor types (including pressure, melt contact, displacement measurement). The recording of the measurement signals is realized by a self-developed hardware system concept. The aim of the research is to predict various quality-determining characteristics from the fields of geometry (including total length) and surface (including sink marks). In the course of the project, extensive tests were carried out to generate a meaningful database. Through analysis and evaluation, it was possible to define the positions and number of sensors that provide a high level of information. Ultimately, three different approaches of machine learning methods could be learned for the prediction of component qualities and the prediction of corrective actions. These structures could be verified in laboratory environment by appropriate test data sets.

Effect Of Seal Pressure On Leak Resistance Of Rigid Hot Tool Sealing Over Film Thickness Transitions In Multilaminate Films
Flint Colvin, Avraham Benatar, June 2022

In flexible packaging, film thickness transitions can be problematic regions to seal due to their propensity for leaking, as well as the high seal pressure required to create a continuous seal over the transition. A compliant anvil can be used to decrease the required seal pressure, as the hot tool will be able to contact both the thick and thin regions of the packaging, with compression of the compliant anvil. However, a compliant anvil cannot be used in a double-sided heating process. Therefore, in a double-sided heating process, high seal pressures must be utilized in order to reduce the film thickness in the thick region, to facilitate tool to film contact in the thin region. In this study, the required seal pressure needed to create continuous (non-leaking) seals over a 4-film to 8-film thickness transition was explored, with both a rigid and conformable anvil. With a rigid anvil 3.25 MPa was required to consistently create continuous seals. With a conformable anvil 0.87 MPa was required to consistently create continuous seals.

Fibril-Flash Formation During Vibration Welding
P.J. Bates, C. Quijano-Solis, J. Vanderveen, B.K. Baylis, June 2022

Vibration welding flash occurs when molten polymer flows under pressure from the weld interface. This study examines the formation of small hair-like fibrils during vibration welding. Polypropylene and nylon 6 plates were butt-welded and the assemblies were assessed using a high-speed camera and digital microscopy. A mechanism has been proposed whereby initial asperities at the weld interface first melt to form a polymer pool. Thermal expansion of this pool allows polymer to be extruded laterally towards the edge of the weld interface. The extrudate is rolled up to form fibrils that can eventually grow to several millimeters in length.

Enhancing Emi Shielding Performance Of Thermoplastics With Long Steel Fibers And Carbon Fibers
Prabuddha Bansal, Suresh Subramonian, Young-Chul Yang, Soo Hee Choi, June 2022

Electromagnetic interference (EMI) is a common problem encountered by electronic devices, especially in electric vehicles. External electromagnetic (EM) waves affect the operation of an electronic device by interfering with the internal EM signals. To provide EMI shielding, various materials were studied, and the measured electromagnetic shielding effectiveness (SE) data are presented in this study. The main factors affecting EMI SE are quantified statistically – filler loading, shield thickness, and base polymer resin matrix. Long steel fiber thermoplastics provide the highest EMI SE, at over 60 dB at frequencies ranging from 30 MHz to 20 GHz, and at thickness as low as 1.6 mm. It is also demonstrated that carbon fiber filled thermoplastics can provide EMI shielding at levels greater than 50 dB.

Understanding The Effects Of Process Parameters On The Curing Of Hexcel As4/8552 Prepreg Composites
Shardul Panwar, Royan J. D’Mello, and Umesh Gandhi, June 2022

The effects of the processing parameters on the curing of continuous carbon fiber composite made from Hexcel AS4/8552 prepreg tape are studied. A commercial process simulation finite element method, that takes in account the residual stresses due to chemical, thermal, and mechanical shrinkages, is utilized. This method solves the curing process sequentially. In the first step, the distribution of temperature and degree of cure in the composite is computed. In the second step, the information from the previous step is used to calculate the stress evolution during cure. At the end of the second step, the composite deformation due to tool removal is also calculated. The impact of three different process parameters on the final degree of cure and the residual stresses are studied in detail.

Ultrasonic Joining Of Additively Manufactured Metalpolymer Lightweight Hybrid Structures
W. S. de Carvalho, S. T. Amancio-Filho, June 2022

Ultrasonic joining is a novel friction-based joining technique to produce through-the-thickness reinforced hybrid joints between surface-structured metals and unreinforced or fiber-reinforced thermoplastics. The reinforcements’ presence is responsible for improving the out-of-plane strength of the parts, enhancing their damage tolerance. The process feasibility has been successfully demonstrated to join additively manufactured (AM) metal and polymer parts. However, further investigation of its main advantages and the joining process of subcomponents to support the technique’s further development is still missing. This paper aims to demonstrate the application of U-Joining to fabricate AM 316L and PEEK hybrid structures produced via laser powder bed fusion and fused filament fabrication, respectively. Firstly, the quasi-static single lap shear performance of coupon specimens produced with optimized joining parameters was assessed. The results indicate an improvement of 2.7 times in the ultimate lap shear force and 5.9 times in the displacement – when compared to non-reinforced flat samples. Fracture surface analyses of tested samples exhibited a mixture of cohesive and adhesive failure. Further microstructural analyses at the metal-polymer interface showed micromechanical interlocking between the parts. As observed, the PEEK was able to flow and penetrate the cavities at the metallic specimen’s rough surface due to the joining friction heat input. Finally, a selected skin-stringerbracket case study was analyzed, showing the potential of AM and U-Joining to drastically reduce the structure’s weight by about 64%. To validate this idea, a scaled-down skin-stringer-bracket technology demonstrator was successfully fabricated.

Using In-Mold Switches For Control And Monitoring Of A Multicavity Hot Runner Mold
Brad Johnson, June 2022

The use of in-mold melt-front detecting switches were used to control the velocity-to-pressure (v/p) transfer during injection and/or to monitor the injection in a 2-cavity, hot runner valve-gated mold. The switches were connected to a data acquisition/control system either independently, in series or in parallel. When the switches were not used for v/p transfer, screw position was used. It was found that using the in-mold switches for monitoring was more effective than either peak injection pressure or cushion monitoring to sort suspect parts and alert of changes in cavity balance. When the switches were either hooked up in parallel or independently, using the first switch closed for v/p transfer, overpacking of the mold was prevented when the heater in the drop/gate of one cavity was turned off.

Machine Learning Modeling to Predict Transient Cavity Pressure Profile in Injection Molding Process
June 2022

A machine learning approach based on artificial neural network is presented and applied to injection molding process. Fill time, maximum fill pressure and transient cavity pressure profiles are predicted with the input process conditions of injection speed, melt temperature and mold temperature. The physics based model using Autodesk Moldflow is evaluated by comparing it with experimental fill pressure profiles for various process conditions, and it is used to generate enough data to train and validate the machine learning model. With the present machine learning model using 400 data samples, not only the fill time but also the transient pressure profiles are accurately predicted with less than 4.7% error. Further, a new machine learning model is trained with 200 data samples, instead of 400 samples, to check the dependence of the model accuracy on the sample size, and the error in prediction of transient pressure profiles increases only to 6.7%.

Deformation Analysis Of Mold Cavity With Sla Conformal Cooling Channel Insert
Olumide Aladesiun, Kyehwan Lee, Yooseob Song, Younggil Park, June 2022

Injection molding is the process of injection molten plastic into a mold to form desired shape of part and it’s widely used process for mass production of plastics over the world. This process is not complete without the mold as it is the most critical part of the process. The cost of producing mold is huge due to manufacturing process and technique, tool material and cost of labor. The more effective the mold, the more efficient the process and the more profitable to the business. A critical factor is the cooling time, and a well-designed mold can achieve even cooling in the shortest period, which leads to increased productivity and higher quality of molded parts. In this research, an alternative core design was employed, to achieve these goals during the molding process. The core has 2 parts: the core and core insert. The core insert was produced using SLA technology to achieve the conformal cooling while the core was machined, and the deflection was studied using finite element analysis.

Influence of Injection Molding Parameters on the Surface Structure of Polyamide Parts
Marius Janßen | Mirco Janßen | Reinhard Schiffers | Robin Blankenagel | Felix Heinzler | Marvin Wagner, May 2021

Injection molded and then electroplated plastic parts are mainly made of acrylonitrile butadiene styrene (ABS) or polycarbonate/acrylonitrile butadiene styrene (PC/ABS) blends. Nevertheless, compared to these materials, polyamide (PA) has superior physical properties. However, the coating quality is inferior to that of conventional polymers and the scrap rates of 25% to 30% are higher. The coating quality depends not only on the electroplating parameters but also on the surface of the injection molded part. The aim of this paper is to determine the influence of injection molding parameters on the surface structure of injection molded, mineral-filled polyamide parts. Therefore, mineral-filled polyamide parts are produced in a full-factorial design of experiments (DoE) and electroplated subsequently. Afterwards, surface parameters from DIN EN ISO25178 are determined by confocal microscopy for different pre-treatments of the electroplating process chain and at different positions.

Novel Foam Injection Molding of Polyamide/Glass Fiber (PA/GF) Composites Using Gas-Laden Pellets
Huaguang Yang | Demitri Shotwell | Jing Jiang | Edward Chen | Lih-Sheng Turng, May 2021

A novel approach of producing foamed polyamide/ glass fiber (PA/GF) composite parts using gas-laden pellets was proposed. Gas-laden pellets loaded with nitrogen (N2) were produced by introducing sub-critical N2 into PA/GF during compounding using a twin-screw extruder equipped with a simple gas injection unit. Compared to the commercial microcellular injection molding (MIM) technologies, gas-laden pellets enable production of foamed parts with a standard injection molding machine, which is more cost-effective and easier to operate. The shelf life of N2-laden PA/GF pellets was examined. Results showed that the N2-laden pellets still possessed good foaming ability after one week of storage under the ambient atmospheric conditions. With this approach, the weight reduction of foamed PA/GF parts was able to reach 12.0 wt%. The tensile strength, cell morphology, and densities of foamed PA/GF parts were also investigated.

Study on the Quantification of the Advancement of Core Material in Co-Injection Molding Products
Kuan-Yu Ko | Chao-Tsai (CT) Huang | Chih-Chung Hsu | You-Sheng Zhou | David Hsu | Shi-Chang Tseng, May 2021

Co-injection molding has been developed for decades. However, due to too many factors which can affect its processing, it is very difficult to obtain good quality of co-injected products all the time. One of the major challenges is that the prediction and management of the advancement of core material is very difficult. In this study, both CAE simulation (Moldex3D) and experimental methods have been applied to investigate the advancement distance of core material in co-injection molding based on the standard tensile bar (ASTM D638 TYPE V) system. Specifically, the flow behavior of the core material has been predicted numerically and verified experimentally through short shot testing, and skin/core ratio effect testing. Moreover, based on the optimized skin core ratio, the major factors to influence of the advancement of core materials have been conducted. Finally, to quantify the advancement of the core material in co-injection molding, both simulation prediction and experimental observation were performed. Results showed that the advancement of the core material is strongly proportional to the core ratio in co-injection molding system. Moreover, the flow rate and the different skin/core material arrangement also can influence the advancement of the core material.

The Effect of Orotic Acid on the Crystallinity Development in Poly-Lactic Acid During Vibration Assisted Injection Molding
Peng Gao | Faisal J. Alzahrani | Animesh Kundu | John P. Coulter, May 2021

This research was focused on the synergistic effect of nucleating agents and an oscillatory motion on the crystallinity development of poly-lactic acid (PLA) during vibration assisted injection molding (VAIM). A differential scanning calorimetry (DSC) study was performed to understand the efficacy of orotic acid, a nucleating agent for 2500 HP PLA, under quiescent conditions. A new protocol for quantitative characterization of crystallization kinetics from DSC data was developed to gain insight on the crystallization kinetics. It was observed that the 1 wt.% orotic acid provided significant enhancement in crystallization kinetics. The isothermal crystallization, injection molded and VAIM data obtained from DSC were compared. The shear stresses introduced during traditional injection molding enhanced PLA crystallization at 90°C and 70° C mold temperature as compared to crystallization under quiescent conditions. The crystallization was enhanced by ~250% when VAIM was introduced at 70°C mold temperature as compared to traditional injection molding was observed. The effect of VAIM was nominal when the mold temperature was 90°C indicating that VAIM is more effective at lower mold temperatures.

Analysis of Injection Molding Simulation of Static Mixer Within the Runner System to Improve Melt Homogeneity, Filler Distribution, and Part Quality
Demitri Shotwell | Stefanie Glas | Edward Chen | Lih-Sheng Turng, May 2021

A Kenics static mixer was introduced into the runner system of a convex-concave circular disc mold and simulated using Moldex3D. The set-up was tested with two mixers with the same diameter, length, and pitch but different mixer element thickness as well as various polymer resins with different rheological properties. The maximum sprue pressure rose with increasing mixer thickness but stayed within normal machine capabilities. Overall, simulations with the thin mixer exhibited improvements regarding melt homogeneity and part quality for polymers such as polyamide 6 (PA6), polycarbonate (PC), and poly-propylene (PP), while the thick mixer had a neutral or negative effect on the same properties. The fiber analysis showed a decrease in fiber alignment in runs including a mixer. Polymers with more extreme rheological properties, such as polybutylene terephthalate (PBT) and polymethyl methacrylate (PMMA), revealed unsatisfactory results.

Effect of Strain Rate and Thermal History on the Mechanical Properties of Polycarbonate
Fabian Ullrich | Davide Masato | Javier Vera, May 2021

This paper compares the strain-rate behavior of injection and compression molded Polycarbonate plates in compression through Split Hopkinson Pressure Bar (SHPB) experiments. The samples are tested under strain rates ranging from 0.01 to 6,000 /s and at a temperature ranging from - 25°C to 75°C. The difference in mechanical response of specimens fabricated using the two different processes is relatively well understood when tested in plane and is influenced by the different molecular orientation distributions resulting from processing [1-4]. However, there has not been a systematic study of out-of-plane response of such materials, particularly for higher strain rates relevant to impact performance of Polycarbonate. The results of this study suggest that an orientation distribution difference between the samples fabricated via the two paths may not fully account for the observed differences, which become more pronounced at the higher ranges of strain rate based on SHPB testing.

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