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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The Effect of Clamping Force on Product Quality: A Study on Platen Deformation
The clamping force is a critical parameter to the stability of mold during injection molding process. An improper setting of the mold clamping force can adversely affect the service life of movable and stationary platens, tie bars, and molds. Thus, the clamping force is a key factor in product-quality consistency. This study bonded strain gauges to both sides of the movable platen to measure, in real time, strain changes in the platen under different clamping-force settings. The results were assessed using the corresponding cavity pressure and mold separation values to determine the molding clamping force’s effect on product quality (with respect to thickness, weight, and appearance). The findings indicated the following. (1) The mold clamping force is significantly correlated with cavity pressure, mold separation, and platen deformation. A low clamping force can cause mold separation to increase, which in turn results in greater platen deformation. (2) For the prediction of mold separation, strain gauges that are mounted on the movable platen can sufficiently replace displacement transducers that are placed within the molds. In other words, the condition inside the molds can be predicted using sensing devices outside the molds. (3) The analytic results for platen deformation and product quality indicate that an insufficient mold clamping force potentially results in excessive mold separation and platen deformation, causing flashing and an increase in product weight and thickness.
The Influence of Laser Power Variation on SLS-printed PA6 Parts and their Long-term Properties
In the field of Additive Manufacturing (AM), Selective Laser Sintering (SLS) is well-known as anAM technique to produce partswith comparatively high load capacity. The usage of Polyamide 6 (PA6) materials allowshigher continuous operating temperatures than Polyamide 12 (PA12) materials, which aretypicallyused forSLS. For this work,PA6 SLS specimens were printed with a high temperature SLS industry printer. The samples were aged thermo-oxidatively at different temperatures, tested mechanically and investigated with different analytical methods. The SLS processing of PA6 materials has not beenstudied sufficiently yet. The aim of this study was to deliver first contributions:the laser power energy wasvaried to identify the influence on the mechanical properties of the printed specimens andtheirlong-term properties. In addition, the material structure of the specimens wasinvestigated and the viscosity number (VN) was determined.
The Influence of Recycling On Thermotropic Liquid Crystalline Polymer and Glass Fiber Composites
In this paper, high-performance thermotropic liquid crystalline polymer (TLCP)/polypropylene (PP) and glass fiber (GF)/PP composites were prepared by the injection molding process. Mechanical recycling of TLCP/PP and GF/PP composites consisted of grinding of the injection molded specimens and further injection molding of the granules. The influence of mechanical recycling on mechanical and thermal properties was investigated. In situ TLCP/PP maintains tensile modulus and strength during the recycling process, indicating the regeneration of polymeric fibrils at each reprocessing stage. GF/PP composite exhibits deterioration of mechanical properties after recycling because of fiber breakage during processing, which is a very common issue on reusing glass or carbon fiber reinforced composites. The experimental results reveal that the TLCP/PP composite has better recyclability than GF/PP and significantly enhances the mechanical properties of the blend.
The Use of Multi-Wave Oscillation To Expedite Testing and Provide Key Rheological Information
Dynamic oscillatory testing is usually performed in a point-by-point fashion. For example, in a frequency sweep, the test material is subjected to oscillation at a particular frequency, equilibrium conditions are attained, and the experiment progresses to the next, discrete frequency. With isothermal tests or temperature ramps, testing is performed at 1 particular frequency, e.g., 1 Hz (6.28 rad/sec). The method discussed in this paper, Multi-wave oscillation, allows one to impose multiple frequencies simultaneously. This enables testing at multiple frequencies in less time than by the conventional method and is particularly useful in characterizing curing systems in isothermal time sweeps or temperature ramps. With some curing systems, especially where there is no Storage Modulus – Loss Modulus crossover point in the experimental timeframe, this enables one to determine an objective gel point, which is defined as the point where tan delta (= Loss Modulus/Storage Modulus) is independent of frequency.
The Use of Novel Biomaterials For Affordable Packaging
The effects of the use of biomaterials for the development of novel packaging composites have been evaluated. An increase in the amount of treated fillers improved the dispersion of the particles and consequently led to an enhancement of the mechanical properties of the materials. The composites were melt-blended using co-rotating intermeshing twin screw extrusion technology and although there can be degradation of the organic additives during extrusion processing, it did not affect the dispersion of the novel biocomposites and the biofillers.A range of techniques used to characterise these materials will be discussed, including morphology, differential scanning calorimetry, (DSC), Scanning electron microscopy (SEM), including experimental techniques likemechanical property evaluations.
Thermal Derating Factors for Fused PVC
The use of PVC pipe has been expanded in the most recent edition of AWWA C900-16. Once solely for drinking water, the AWWA C900 standard now includes reclaimed water, irrigation water, wastewater, or any other fluid compatible with nonplasticized PVC. When limited to drinking water, there is relatively little use for PVC to operate at elevated temperatures. The scope increase including industrial, raw water, geothermal, and other opportunities now make the use of PVC pipe viable so long as the pipe can meet temperature and pressure requirements. The hypothesis tested is that the present set of thermal derating factors may contain room for adjustment with the present PVC pressure pipe extrusion formulations and technology. This presentation details out the test methods used to screen and then develop derating guidance for fused PVC pipe. Screening methodology and results to validate the hypothesis are discussed. With positive results from the screening, the long term testing done to develop an alternative set of derating factors is also included.
Thermoplastic Elastomer Blend Exhibiting Combined Shape Memory and Self-Healing Functionality
Here we report on a polymer blend consisting of a soft-thermoplastic polyurethane (TPU) elastomer and a low melting temperature thermoplastic healing agent (Polycaprolactone, PCL) capable of repairing highly deformed cracks without the need for an external load. In this study, a blend containing 30wt% PCL (30PCL) was shown to exhibit two well-separated melting transitions thus enabling shape memory behavior. Moreover, upon heating to above PCL’s melting temperature the flow of PCL into an undeformed crack was shown to fill the crack void thus promoting self-repair. A combined healing mechanism relying on both shape memory and self-healing action was demonstrated. Through the simple action of mild heating (90C/30 minutes), fracture surfaces are brought into intimate contact through the action of shape memory recovery and subsequently healed. Healing efficiency was evaluated by comparing the tensile force restoration after healing of a highly deformed, notched sample to its behavior prior to notching. Here it was shown that the polymer blend exhibited full restoration of its originally mechanical integrity whereas the mechanical performance of pure TPU was only minimally restored (about 5%). This blend is based on thermoplastic ingredients and thus able to be converted using conventional melt processing. Applications of such blends can be extended to products prone to damage such as liner materials, protective coatings, sporting goods and shoe soles.
Towards Multi-Tiered Quality Control In Manufacturing of Plastics and Composites Using Industry 4.0
One of the most important topics in modern manufacturing, Industry 4.0 is quickly changing the way in which production lines in many industries operate. Industry 4.0 broadly refers to the connection of multiple manufacturing systems into a large system in which those individual systems communicate with one another. With systems connected in such a fashion, manufacturers can easily obtain actionable data from every aspect of their systems and use that data to improve their processes. Generally, Industry 4.0 technologies will vary significantly with application, and as a result, it can be difficult to develop an effective system from scratch. Given the increasing quality requirements demanded of the composites industry, particularly from automotive manufacturers, the development of an effective system to integrate data from the manufacturing process and apply it to advanced quality control methods is critical. Accordingly, we propose the concept of a multi-tiered system that combines machine data, in-mold sensors, external sensors, and a human component for use in plastics or composites manufacturing settings. Using this infrastructure, a multivariant analysis is first conducted to evaluate the advantages and limitations of each data sources in terms of determining process and part deviation. In the second study, the feasibility of developing a framework for monitoring quality of injected parts is investigated using a machine learning approach.
Transition From Ductile Failure To Brittle Fracture of High Density Polyethylene Under Creep Loading
Uniaxial creep tests on notch-free specimens were conducted on unimodal high-density polyethylene (HDPE) over a wide range of stress and temperature. As expected, occurrence of ductile failure or brittle fracture was found to depend on the applied stress and temperature. In this work, a stress-time-temperature (StT) expression was established to construct the master curve of stress versus creep time to ductile failure (or brittle fracture) at a given temperature, which contains the transition between the two behaviors (commonly known as the DB transition). For the unimodal HDPE used in this study, critical stress for the DB transition was found to decrease significantly, from 11.43 to 6.50 MPa, by increasing test temperature from 296 K to 358.5 K. The corresponding time also reduced considerably, from over 560 hours at 296 K to about 6 hours at 358.5 K. In addition, critical stress for the DB transition shows a good correlation with one characteristic quasi-static stress that we reported before. Such a phenomenon sheds a light on the possibility of using a short-term test to characterize DB transition of PE pipe.
Transition Metal-Catalyzed Degradation of Polymers: Review and Future Perspectives
In many instances, failure of polymer-based articles is attributed to chemical interaction with metals or metallic compounds. Indeed, the stability of polymers is often modified by these species; however, their effects on the degradation of polymers are complex and influenced by many factors. This paper reviews known polymer degradation mechanisms and how metals may influence them, discusses deactivators and their role use as stabilizers in polymer formulations, provides literature-based vignettes describing example scenarios where metal-accelerated degradation of plastics may contribute to failures, and provides commentary regarding potential future areas of work in the field.
Understanding the Limitations of 3D Printed Polymers Through A Staged Screening Protocol
Direct printing of polymers has continued to advance with new printing technologies and engineering grade materials allowing actual additive manufacturing versus 3D printing of prototypes. Key developments include the adaptation of digital light processing (DLP) printers as well as improvements to and novel powder-based printing systems. These technologies offer the ability to bring new printed materials to the market. However, simply because a material can be printed does not mean that it will function well. With the number of printing and material advances, the need to understand possible failure modes and incorporate that knowledge into screening testing is critical. This work provides basic consideration and screening methodology to ensure that these possible material failure modes are accounted for.
Upcycling Ocean Bound PET Waste Into Durable Materials
Dealing with plastics waste is a major issue confronted by the society. Single use items from water bottles to plastic packaging are major contributors to the generation of plastics waste globally. Innovative upcycling technology can transform a plastic with limited applications and a brief useful life into a different, more-durable resin with expanded potential uses and an extended lifetime. In this way, upcycling can help strengthen the circular economy and can help reduce the impact of single-use plastic applications on the environment. Using propritary de-polymerization of recycled polyester, SABIC has introduced a more sustainable polyester products family containing up to 60% recycled materials. This new PBT and its compounds have similar purity and properties as virgin resin. Hence they are drop in for many virgin PBT or compounded products. Chemistry, properties, and application for these sustainable polyester materials will be discussed. In particular, the application of ocean bound based resin in Dell computer fan housing will be highlighted.
Using a Micro Blown Film Line for Formulation Screening
A LabTech Ultra Micro Combi line (Microline), the smallest blown film line in the world, was used to conduct blown film formulation screening with a set of LLDPE/LDPE blends. A sample cutting pattern was developed to enable preparation of crease-free test specimens from the small layflat made on the Microline. Haze, dart A, tear (MD, TD) and tensile (MD, CD) were tested using the film made by the Microline. By carefully controlling the time to frost line on the Microline to match the time to frost line on the larger scale lines, it was found that dart A, tear (MD, TD) and tensile (MD) of the Microline film were correlated with those of the larger scale lines films. These film properties can be used for formulation screening with minimal consumption of materials (~150 g per film sample). Haze and tensile (CD) properties did not correlate with those of the larger scale lines films. Future work will investigate the cause of these deviations.
Validation of the Virtual Lifetime Prediction Method for Elastomer Components
In the field of mechanical engineering technical elastomers are indispensable due to their material properties. They are often used to avoid load peaks and to influence the vibration behavior of dynamically loaded systems, because of their damping characteristics. Therefore, one field of research constitutes the damage accumulation and lifetime prediction. This paper presents the validation of the virtual lifetime prediction model method, which was developed at the institute of product engineering at the University of Duisburg-Essen. The lifetime is defined as the number of load cycles till the global damage reaches the value 1. This damage is calculated by a failure criterion based on the change of a characteristic value like the dynamic stiffness degradation from a finite-element (FE) simulation. The virtual lifetime prediction method uses a combination of a damage-dependent material model (Yeoh-Model) and a nonlinear damage accumulation model (nlSAM). Both models are calibrated by means of experimental data from dynamically loaded elastomer components. The nlSAM computes the local damage for each finite element depending on material stresses and pre-damage. The dynamic stiffness degradation is a result of locally changed material properties in the FE simulation due to the damage of each element. Finally, the lifetime prediction for unknown loads and different component geometries of the elastomer is carried out, which shows good agreement with the experimental data of the same material batch.
Viscoelastic Measurement and Injection Molding Simulation of Amorphous Polymer: From Liquid to Solid
The viscoelastic properties under wide temperature range (from viscous to glassy state) and various flow field are studied in this work for a commercial amorphous polymer. It is found that multi-mode EPTT model can describe all measured properties well including dynamic modulus, steady shear viscosity, first normal stress difference, and transient extensional viscosity. 3D flow VE simulation are conducted to validate the applicability of the fitted model and parameters by comparing with the injection pressure in filling and packing stages.
Viscosity Characterization and Transient Flow Simulation and Visualization of Ptfe Paste Extrusion
The shear viscosity of polytetrafluoroethylene (PTFE) paste and its flow behavior during paste extrusion were investigated. Frequency sweeps using a parallel plate rheometer were performed on compression molded samples of PTFE paste made from fine powder PTFE mixed with ethanol as a lubricant. Various grits of sandpaper were used to reduce slip of PTFE paste on the walls. A viscosity model was generated and COMSOL Multiphysics was used to create a time-dependent flow simulation of PTFE through a paste extruder. The simulated results were compared to experimental data of actual paste extrusion. Due to simplifications used in the model, the simulated extrusion pressure over time differed in both magnitude and slope when compared to the experimental data. The simulated velocity profile was compared to flow visualization experiments, showing good agreement in wider regions of the extruder. Despite these drawbacks, the experiments and simulated model provided useful information about the flow within the paste extruder.
Viscosity Considerations In Multilayer Coextrusion
Due to complex viscoelastic nature of the polymers, it is challenging to process multicomponent structures with uniform layer thicknesses. Although multilayered structures have been processed in a broad array of polymer materials and formulated to service a wide range of applications, a clear understanding of the effects of viscosity matching on the uniformity of the layer periodicity is not well understood. Significant work on viscous encapsulation and secondary flow patterns in the die channels affecting the layer structures has been previously reported. However, further evaluation of these effects on wide range of materials in commercial coextrusion lines has been limited. In this paper, we look to extend the initial studies of rheology in multilayered materials via layer multiplication coextrusion approaches and demonstrate preliminary results on model systems that illustrate the effect of mismatched viscosity on coextrusion multilayered polymer materials systems.
Workflow for Enhanced Fiber Orientation Prediction of Short Fiber-reinforced Thermoplastics
In this paper a workflow is proposed for an enhanced fiber orientation prediction in injection molding of short fiber-reinforced thermoplastics. The workflow is easy-to-use, as the final fiber orientation prediction is integrated into the commercial software Moldflow®. For a given material with polymer matrix P and a volume fraction x of fibers, four steps have to be performed: 1) Generating a representative volume element (in the following, referred to as cell) with volume fraction x and mean fiber length, 2) Shearing of the cell using a mechanistic fiber simulation, 3) Calculating the transient fiber orientation tensor and fitting macroscopic parameters and 4) Performing the fiber orientation analysis with the optimized macroscopic parameters in Moldflow®. Based on experimental data, the pARD-RSC model was selected as macroscopic simulation model. It was implemented in Moldflow® via the Solver API feature. The enhanced workflow is validated at the example of two industrial applications with different polymer matrices and different fiber volume fractions. With the proposed workflow, we observe equal or higher accuracy of fiber orientation estimation in comparison to Moldflow® fiber orientation models RSC and MRD.
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