SPE Library

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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Conference Proceedings

Mechanical Properties Of Polyamide 6/Zeolite Composites

davoud jahani, May 2018

Many researchers have investigated the effect of Nano- and Micro-scale materials on the mechanical properties of the thermoplastic polymers. Some researchers showed that adding small amount of some mineral material to polymers matrix may enhance their physical and mechanical properties. In this study polyamide 6/zeolite composites having 2.5, 5, and 7.5 phr of the zeolite were prepared using a twin screw extruder and injection molding process, and different mechanical properties of the composites were investigated. Our results show that adding zeolite particles to polyamide, leads to increase of tensile strength by the maximum of 33%. Also having 7.5 phr of zeolite particles in the polyamide matrix results on 61% increase on the strain to rupture, compared to the pure polymer.

Effect Of Stress Relaxation On Shrinkage And Warpage Of Injection Molded Parts

Zhiliang Fan, May 2018

The residual stresses in the injection molding process are built up due to the restriction of thermal contraction during the process, coupled with the frozen layer growth with varying pressure history. The stress relaxation behavior of plastic materials complicates the stress field. A three-dimensional linear anisotropic thermo-viscoelastic residual stress model is developed for predicting the effect of stress relaxation on shrinkage and warpage of injection molded parts. Thermo-rheological simplicity is assumed for the material, and the viscoelastic master curve is fitted with a generalized Maxwell model. A time-temperature shift factor table over the range of temperatures which occur during the injection molding process is preferred over the WLF equation and Arrhenius equation due to its general applicability. Two numerical examples are given, and the simulation result comparison between the thermo-viscoelastic model and thermo-viscous-elastic model shows that stress relaxation reduces the molded-in residual stresses slightly, and has a modest impact on shrinkage and warpage. The validation cases also confirm that the simple thermo-viscous-elastic residual stress model is generally able to give a good qualitative and reasonable quantitative prediction of the final shrinkage, warpage and molded-in residual stresses.

Effect Of Injection Molding Condition On Mold Adhesion During Thermoplastic Polyurethane Injection Molding

Jian-Yu Chen, May 2018

Injection molding is one of popular approach for the mass-production of plastic products with complex geometries. Although it is convenient and cost-effective to manufacture goods, some issues such as warpage, quality fluctuation of injection molded part, surface defects, insufficient physical properties are still needed to overcome. During ejection stage, one of annoying issues called mold adhesion, which happens to the interface between molded part and cavity surface, makes molded part difficult to release from mold surface, and the defects such as distortion and crack also occur as serious mold adhesion effect arises. This phenomenon is familiar during thermoplastic polyurethane (TPU) injection molding process. There are numerous factors affected the mold adhesion level, including injection molding conditions, surface morphology, surface modification, rheological properties of molten polymer. In order to understand the effect of molding conditions on mold adhesion level, tensile mode mold adhesion tester was proceeded to quantitatively evaluate mold adhesion level. In addition, surface free energy measured on molded part surfaces was carried out to better understand the wettability. In experiment results, mold temperature and melt temperature both effect on mold adhesion level. Moreover, the responses of SFE on different mold adhesion level are apparent.

Effects Of Processing Parameters On Fiber Length Distribution And Tensile Strength Of Long Glass Fiber Reinforced Nylon66 Composites Molded Parts

Hsin-Shu Peng, May 2018

This study investigates the effects of processing parameters on the tensile strength and fiber length distribution of long glass fiber reinforced nylon66 composites. This study carried out the injection experiment at different screw speeds in order to take the fiber breakage and length distribution as the basis for the setting of processing parameters. The effects of processing parameters on tensile strength of long glass fiber reinforced nylon66 composites (LGF-Nylon66) were then studied using a tensile test specimen mold with single /double gate design (part thickness of 1.8 mm and 3.6 mm).The experimental results show that increasing the screw speed leads to fiber breakage, shortens the fiber length, and thus affects the tensile strength of long glass fiber reinforced nylon66 composites molded parts. On the other hand, as the melt temperature and the mold temperature increase, the tensile strength also increases. In addition, SEM observation presents that the effect of fiber length and orientation distributions on the weldline tensile strength of the molded specimen is very obvious. These results also show that the interfacial adhesion is required to achieve a desired composite strength.

Zero Defect Manufacturing In Injection Compression Molding Of Polymer Fresnel Lenses

Dario Loaldi, May 2018

Fresnel lenses are polymer optics with reduced dimensions and higher illumination properties. Their structured profile involves high precision replication techniques when industrial scale manufacturing is concerned. Injection Compression Molding (ICM) is the state of the art replication technology to ensure mass production of polymer optics. The opportunity to perform a compression phase on the polymer melt while injected into the cavity, ensures a more homogenous replication of the part, enhancing birefringence and transparency amongall the optical properties. However, it is not common to find studies concerning the technological signature of ICM components. The optical transparency of polymer optics as long as the complexity of Fresnel lens profile, are big challenges for metrology making this knowledge expensive and rarely investigated. In this study, absolute dimensions of Fresnel lenses step heights are correlated with respect to ICM process conditions. In a first experimental plan, the effect of packing and compression is individually evaluated on two different materials. In the case compression is performed without packing, the form replication accuracy of the micro structures fails, showing deviations up to 10 times the nominal dimension. On a secondary experimental campaign, packing pressure and compression gap are optimized together to identify the most favorable replication condition. The results show a second order interaction between compression gap and packing pressure. The average replication increases by 1.4 % when both a high level of compression gap and packing pressure are selected.

Controlling The Local Part Properties Using A Segmented Temperature Control In Injection Molding

Mauritius Schmitz, May 2018

One of the most important challenges in injection molding is to achieve precise parts regarding dimensional stability and warpage. Due to the nature of thermoplastic material properties, the inner properties of a part change drastically with varying conditions like pressure, temperature or shear rate. Additionally, the specific plastics properties may change due to batch variations or ambient conditions like humidity or temperature. This work illustrates a method to influence the part properties locally within the injection molding cycle. This should be achieved by a segmented temperature control in combination with local temperature and pressure measurements. The aim to manipulate the local part properties such that a homogeneous part shrinkage can be achieved, resulting in minimized part warpage. As control variable the local specific volume is used. Therefore, a novel mold was developed to effectively influence the local specific volume using a segmented temperature control. The results have shown, that the part warpage reacts significantly on the changing processing conditions and that the mold is capable of influencing the part properties heavily.

3D Surface Characterization Of Etched, Injection Molded Parts Before A Follow Up Electroplating Process

Jens P. Siepmann, May 2018

When technical polymers like acrylonitrile butadiene styrene (ABS) or polycarbonate/ acrylonitrile butadiene styrene blends (PC/ABS) are processed with injection molding machines for a subsequent electroplated coating not only the electroplating parameters, but also the surface of the etched, injection molded part is responsible for the adhesion of the polymer and the metal [4],[5].In this paper, the effects of processing parameters and mold geometry on the surface structure of injection molded ABS and PC/ABS parts after etching within the electroplating process chain are investigated. For this purpose, relevant parameters (injection speed, barrel temperature and mold temperature) are varied in an experimental design. All parts are prepared for the following electroplating by etching the surface with identical parameters (time, temperature). The part surface is measured at different positions on a test part using a confocal microscope, which was identified to offer sufficient resolution to generate micro- and nano-scale depth information of the surface structures. Surface parameters from DIN EN ISO 25178 (height and spatial parameters) are investigated to describe the surface properties depending on the position on the part and the processing parameters. By combining already published methods for the measurement of two-dimensional surface properties using SEM [1], [2] and the new 3D information, findings regarding the properties of ABS and PC/ABS were generated.

Study On An Optical Evaluation Of Surface Adhesion In The Multilayer Injection Molding Process

Byungohk Rhee, May 2018

To reduce production time of thick walled parts such as optical lenses, the multilayer injection molding has been developed. In the optical applications, surface adhesion quality between layers should be sufficient. To evaluate the surface adhesion a mechanical strength test was used. However, mechanical strength test has a limitation to evaluate the surface adhesion quality. In this work, an optical evaluation method is proposed to quantify the surface adhesion quality of multilayer injection molded optical parts. It measures light intensity change by light scattering at inter-layer surface. Feasibility of the optical evaluation method as a reliable evaluation tool was examined with specimens ground by sand papers to alter surface roughness. As surface roughness increases, the light intensity increases. Also, it showed a high intensity at an inter-layer surface made by insufficient diffusion. As well as surface roughness of the first layer, influence of processing conditions to surface adhesion were examined. However, no processing conditions showed a noticeable influence.

Stabilization Of BMC Injection Molding By Process Control Measures

Nicolina Topic, May 2018

Polyester molding compounds form a quarter of Europe´s glass fiber reinforced plastics production. Their main applications are automotive parts such as exterior body parts and headlight reflectors. Dependent on the processing method there are two types of polyester molding compounds which mainly differ in their composition and raw material condition. For compression molding sheet molding compounds (SMC) are used, while bulk molding compounds (BMC) are processed by injection molding. In comparison to SMC compression molding, BMC injection molding allows higher production rates at a better process reproducibility. However, there are several effects such as material induced interferences or changing ambient conditions that cause fluctuations and lead to varying part quality. The manual adaption of the relevant process setting parameters presents an option to react on such interferences and prevent further rejects. The outcome of these adjustments is dependent on the experience of the operator, since an accurate knowledge of the influence of certain setting parameters on individual part quality features is required. In this paper the impact of occurring interferences on the volumetric part filling is analyzed. In order to prevent negative effects by these disturbances, two existing process control measures, which react inline on fluctuations by automatically adjusting relevant process parameters, are used and validated.

The Effect Of Rapid Heating Cooling Molding On Polycarbonate Based Material Properties

Jessica Boyer, May 2018

The plastic industry uses advance injection molding technologies to enhance part performance and surface appearance. Rapid heating cooling molding (RHCM) technology has been shown to enhance surface appearance and achieve high mold surface replication. In this article, we examined the physical properties of Polycarbonate and Polycarbonate/ABS to compare conventional injection molding (CIM) and RHCM. The comprehensive study investigated stress-strain properties, weld-line strength, impact performance, and flow length. The results demonstrated that RHCM did not affect the bulk material physical properties. In some cases, the study showed an increase in physical properties for weld-line strength and flow length.

Injection Molding Parts With Integrated All-Inkjet Printed Strain Gauge For Conditon Monitoring

Thomas Mitterlehner, May 2018

Injection molding parts became more and more complex and especially critical components are subjected to high safety requirements. In this paper a fully functioning injection molding test specimen with integrated condition monitoring was developed by using all-inkjet printed strain gauges and back injecting them. For the printing of electrically conductive traces a commercial available Epson printer and silver nanoparticle dispersion was used. This enables the fabrication of sensor systems without the need of a photo mask. Furthermore the applicability for monitoring injection molding parts with low-cost sensor systems was investigated. Therefore several test specimens with integrated strain gauges were fabricated and tested with a tensile testing machine. With the integrated strain gauge the relative change in resistivity was measured and the resulting strain was then compared to the results of the tensile testing. In this context the gauge factor of the printed conductive traces were characterized.

Automatic Anomaly Detection And Root Cause Analysis For Holistic Process Monitoring And Control In Injection Molding

Alexander Schulze Struchtrup, May 2018

Modern injection molding machines with state-of-the-art control technology enable plastics-processing companies to operate processes resulting in high part quality and low reject rates. However, external influences such as fluctuations in the material properties may cause the production of bad parts, which is often detected with a time delay, causing high costs. Based on this, the present paper describes a procedure to gain valuable information from the continuously generated process data. It shows how methods for anomaly detection and localization of their underlying root causes can help machine operators identify critical process states more quickly. This in turn leads to lower reject rates and machine down times and thus an enhanced overall process control.

Get The Wear Out

Steve Wilson, May 2018

Most would agree that the mold is the heart of the molding process. From those that make them to those who use them, we all want them to last for as long as they were designed. A lot of work goes into striving toward that goal: good design, proper metallurgy selection, configuration, coatings, etc. With all that having been taken into account, why clean the mold with traditional methods that may wear out the parting line and shut-offs? This paper will demonstrate that cleaning tooling with dry ice is a safe, effective and non-abrasive way to clean common injection molds. It will provide molders, not only a way to extend the asset life of the tool, but also to improve quality, increase productivity, lower costs and improve environmental quality. This paper will focus on the first benefit of maintaining the expected life of our molds. Today, high-dollar and often complex molds, are run and maintained in varying degrees of skilled molding shops and tool rooms. Some of the cleaning methods still be utilized can contribute to tool wear.

Mechanical And Rheological Characteristics Of Pp/Pet Blend With Maleic Anhydrite And Jute Fibre

Abul Saifullah, May 2018

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.

Induction Heat Cool With Sabic Resins: An Intro To High Definition Plastics

Jos van Gisbergen, May 2018

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.

Moldflow Optimization Of Micro-Cavities Filling During Injection Molding Process

ali rajhi, May 2018

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).

How Over The Wall Engineering Affects Process Capability And Process Robustness

Suhas Kulkarni, May 2018

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.

Flowcon Plus, Digital Water Flow Regulator

Edgar Sanchez, May 2018

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.

Improved Processability Of Ultra-High Molecular Weight Polyethylene Via Supercritical Nitrogen And Carbon Dioxide In Injection Molding

Galip Yilmaz, May 2018

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.

Modeling Of The Ultrasound-Assisted Ejection In Micro Injection Molding

Giovanni Lucchetta, May 2018

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.