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
Mitigating Resin Degradation Via Nitrogen Inerting for Single-Screw Extruders
Resin degradation can reduce the value of a product, especially for polyethylene (PE) films. Most of the degradation occurs in the final processing operations using single-screw extruders. There are many reasons why degradation occurs, and screw design is considered the first and best opportunity to mitigate it. The elimination of atmospheric oxygen is the next best option. This paper describes a method for mitigating resin degradation via nitrogen purging at the hopper. Extrusion data are provided that demonstrates the effectiveness of nitrogen purging for PE resins.
Experimental & Analytical Investigation of Incomplete Filling Defects During Hot Runner Based Inject
A novel processing innovation called Rheodrop technology is introduced for hot runner based injection molding. The goal is to enable both optimized processing and properties of final molded parts. The technology applies a controlled shear rate to the polymer melt during and/or in between injection molding cycles by rotating the valve pin inside a hot drop nozzle. Doing so can eliminate defects such as incomplete filling which was focused on during this study. This issue was investigated through both simulation and experimental analysis. Moldflow software was utilized to study the effect of melting temperature on cavity filling. Acrylonitrile Butadiene Styrene (ABS) was chosen as a focus material, and three different melt temperature levels were selected. The cavities are perfectly filled at the highest melt temperature level with incomplete filling resulting at the lower levels. Implementation of the Rheodrop technology then produced consistent and complete filling throughout the melt temperature range studied.
Large-scale extrusion-based 3D printing for highway culvert rehabilitation
A significant problem associated with repairing deteriorating highway culverts is the resultant lowered flow capacity. This can be mitigated by the use of culvert diffusers. Current culvert diffusers are made using fiberglass reinforced thermosetting epoxy polymers, which require custom made molds. This research work explores the use of large-scale 3D printed thermoplastic polymer composite to manufacture culvert diffusers. The research work shows that 3D printing technology reduces the manufacturing time as well as the cost of culvert diffusers. Large-scale 3D printing technology is well-suited for the manufacture of individualized culvert diffusers with unique geometrical designs without the need for molds. 3D printing technology is also capable of using different materials according to environmental requirements. The use of segmental manufacturing in conjunction with large-scale 3D printing enables the manufacturing of culvert diffusers larger than the build envelope of the 3D printer. Different post-processing techniques used for cutting, finishing, and joining the 3D printed segments are discussed.
Fused Filament Fabrication Feedstock Characterization via In-Line Rheology
An instrumented hot end has been developed to monitor the pressure in Fused Filament Fabrication, and is used as an in-line rheometer to characterize the viscosity of an acrylonitrile butadiene styrene (ABS) material. Additional analysis was performed on the transient pressure data to consider compressibility effects and nozzle drool. The range of flow rates was identified at which the pressure in the hot end was most stable. Stabilization time given compressibility effects was also evaluated.
Investigation and Realization of Watertight FDM Structures Made of Ultem 9085 in Pressurized Systems
Fused Deposition Modeling (FDM) parts generally show a fluid permeability due to their specific and characteristic strand structure. Therefore, an application including contact with water is difficult and limits the areas of application of this Additive Manufacturing (AM) technology. In this paper the aim is to determine the water tightness of FDM manufactured Ultem 9085 structures in a pressurized system using a suitable test setup. Based on the results, optimization approaches such as parameter modification, variation of the specific part thickness and a surface treatment shall identify if a complete tightness can be realized. For the validation of the results, analysis methods such as CT-scans and macroscopic images are used to determine the component surface.
Effect of Carbon Fiber On the Fracture Toughness of Fused Filament Fabricated CF/ABS Composites
This study reports the effect of carbon fiber (CF) on the fracture toughness of 3D printed carbon fiber/ acrylonitrile butadiene styrene (CF/ABS) composites. Chopped carbon fiber was compounded with ABS to prepare CF/ABS filaments containing 0-25 wt.% CF. Compact tension specimens were designed, 3D printed, and tested to measure the composites’ mode-I fracture toughness, KIc. The results showed CF/ABS composites can be made with up to 25 wt.% loading without any drop in their fracture toughness. In fact, ABS’s KIc increased by ~22% with an introduction of 10 wt.% CF. There was a slight drop in KIc, once the CF content was increased to 15 wt.%. Further increase in CF content from 15 to 25 wt.% did not cause any significant change in KIc and it was found to remain similar to that of the neat ABS. The fracture toughness trend with CF content was qualitatively explained in terms of two competing mechanisms, namely increased actual fracture surface area and less perfect interlayer adhesion at the presence of CFs.
Simulative Analysis of the Filling Process in the Two-Component-GITBlow-Process on Organo Sheets
The combination of different special processes allows the production of complex hybrid component structures with simultaneous function integration, thus opening up a large portfolio of possibilities. One example of this is the combination of back-injection of thermoformed organo sheets with the GITBlow process. An organo sheet is back-injected by two components, whereby one of the two components is additionally formed by the GITBlow process. The separation of the two cavities during the filling process by the formed organo sheet is a challenge not to be underestimated. The investigations refer to the simulative analysis of the filling process of the cavities. Here, the melt displacement into the secondary cavity during the first gas injection and the influence of the separation of the two cavities are considered. Investigations show that the melt temperature, the gas pressure and the injection speed have the greatest influence on the filling of the cavity separation.
Evaluation of Pressure Reduction for Various Materials at Various Length to Thickness Ratios Using An iMFLUX® Constant Pressure Process
This paper will show that an iMFLUX® constant pressure process can significantly reduce molding pressure requirements compared to conventional velocity controlled injection molding while molding a part with an equal length to thickness ratio. A significant pressure reduction is observed for all materials; regardless of material type or family. All comparisons in this paper are based on the maximum achievable flow length of a conventional velocity controlled process for each material.
Investigate on the Degree of Assembly for Components in an Injection Family Mold System
The main target for Design for Manufacturing and Assembly (DFMA) is to integrate multiple components with multiple functions to minimize cost and efforts. In addition, a family mold system has been utilized in industrial manufacturing to make a series integrated components for years. However, there is very few information to the degree of assembly for a single component or components. In this study, we have tried to investigate the degree of assembly using a family mold system with two different components. The study methods include numerical simulation and experimental observation. Firstly, we have adopted packing pressure as the practical operation parameter to affect the variation of degree of assembly. Then the pre-defined characteristic lengths can be utilized to catch the degree of assembly. Results showed that when a higher packing pressure applied in injection molding, it will results in more difficulty in the assembly for Part A and B by numerical prediction. Furthermore, the experimental validation on the degree of assembly based on the characteristic lengths has also performed. The tendency is quite consistent for both numerical simulation and experimental estimation. However, there is some gap between simulation prediction and experimental measurement for the same operation condition setting. It is necessary to make further study in the future.
Characterization of In-Mold Shrinkage Using a Multi-Variate Sensor
The design of a multivariate sensor is detailed that incorporates a spring-biased pin for measuring in-mold shrinkage. The sensor also includes a piezoelectric ring for measurement of polymer melt pressure and an infrared detector for measurement of the polymer melt temperature and the local mold temperature. As a result, the multivariate shrinkage sensor can accurately measure cavity pressure, melt temperature, ejection temperature, various event timings, and in-mold shrinkage to closely estimate the total shrinkage. The performance of the sensor is validated with a design of experiments for a high impact polystyrene (HIPS) and polypropylene (PP).
Influence of Chemical Blowing Agents on the Filling Behavior of Wood-Plastic-Composite Melts
A major challenge in the injection molding of wood fiber reinforced thermoplastics, so-called Wood-Plastic-Composites (WPC), lies in the flow anomalies that occur during the cavity filling process. The melt front is brittle and breaks open at unpredictable points. Particularly at wood contents above 40 % by weight stream flow (jetting phenomenon) caused by wall slipping occurs more frequently, which in turn leads to undesired weld lines. In this study, an analysis method is presented, which allows a quantitative evaluation of the filling process. The methodology is applied to different WPC formulations. Higher wood content, low viscous matrix polymers and coarser particles lead to poorer filling behavior overall. In order to reduce the flow anomalies, chemical blowing agent is added to the WPC. This should reduce the viscosity and thus the elasticity of the melt. It has been shown that reducing the viscosity has no positive influence on the filling behavior. An improvement could only be achieved with the lowest viscosity formulation. However, the explanation for this is seen in the comparatively lower resistance of the melt to the expansion of the blowing agent, as a result of which the melt is pressed more strongly against the mold wall and wall slipping is thus rather suppressed.
Enabling Mechanically Adaptive 4D-Printing with Cellulose Nanocrystals
Additive manufacturing of stimuli-responsive materials is an area of 4D-printing that is continuing to gain interest. Cellulose nanocrystal (CNC) thermoplastic nanocomposites have been demonstrated as a water responsive, mechanically adaptive material that has promise to generate 4D-printed structures. In this study, a 10wt% CNC thermoplastic polyurethane (TPU) nanocomposite is produced through a masterbatching process and printed using fused filament fabrication (FFF). A design of experiments (DOE) was implemented to establish a processing window to highlight the effects of thermal energy input on printed part mechanical adaptivity (dry vs. wet storage modulus). The combination of high temperatures and low speeds result in thermal energies that induce significant degradation of the CNC/TPU network and reduced absolute values of storage moduli, but the mechanical adaptation persisted for all the printed samples.
Simulation of the Flow in a Bilayer PVC Window Profile Die With Gradually Changing Calibrator Profiles
Simulation of the flow and extrudate deformation in a bilayer window profile die is presented. The shape of the profile was modified during extrudate cooling by changing the shape of successive calibrator profiles. The effect of non-uniform exit velocity, cooling shrinkage and shape of calibrator profiles on extrudate deformation is included in the simulation.
Operating Performance of Free-Rotating Mixing Sleeves in Single-Screw Extrusion
In this paper, an experimental design with three mixing sleeves, two materials and several operating points is carried out to determine the operating performance of free-rotating sleeves in single-screw extrusion. The focus will be on the investigation of the operating parameters: sleeve speed, pressure loss and temperature development. Therefore, an automated method for determining the sleeve speed will be presented.
The Journey to Stabilization of Automotive Plastic Applications
This paper will treat to expose the complexity of stabilization of plastics in automotive applications. First, we will review some basics on stabilization, the use of phosphites and phenolic antioxidants. We will cover the different aspects of polymer stabilization: during processing and along the service life of the parts. This will involve discussion around light stabilization too. Along this paper, we will see some examples of outstanding chemistries than can lead to combine several benefits to achieve the performances required by OEMs.
A Breakthrough in Piano Black: Raven 5100 Ultra for Engineering Plastics
A newcarbon black product was developed at Birla Carbon with ultra-high jetness and bluish undertone for high color applications in plastics.The new product was demonstratedwith improved jetness in various polymer systems overthe existing high colorproducts,especiallyachievinga 40% improvement in polyamide 6. Thenew product shows great potentialfor ultra-high jetness plasticsapplications including automotive, household appliances, and consumer electronics.
Reaction Model to Predict Photo Degradation Mechanism of Polyethylene Containing CB and HLAS
Photooxidative processes that lead to chain scission and chain linking in polymers play an important role in polymer degradation. These processes are induced by both ultraviolet and visible light absorption. Antioxidants can enhance the usable life-time of polyethylene, and some fillers can act as a UV screen and also as a chain terminating and peroxide decomposing agent in the polyethylene UV degradation. In this paper a reaction model is developed and described for UV degradation of polyethylene containing a hindered amine as an antioxidant and carbon black as filler. The degradation mechanism follows free radical initiation, propagation, termination, and stabilization steps. Reactions between free radicals and antioxidants with carbon black are considered. Mass balance on each reacting species gives the model equations that are solved using parameters that are either estimated or fitted. The model gives key parameters responsible for the degradation and stabilization.
Simulation of Thermoforming Process for Truck Roof Fairing Applications
Thermoforming is an efficient, very cost-effective and widely used process for the production of large parts in transportation applications. The long-haul truck roof fairing demonstrates the feasibility of replacing traditional materials with thermoplastics in order to improve aerodynamics and, in turn, cut a truck’s fuel use. Simulation becomes a powerful means for a large part and complex process to arrive at, and optimize process conditions. This, in turn, helps to achieve the desired product quality for a given material.
The present study describes the results from the use of thermoforming simulation as a tool for optimizing sheet thickness, sheet temperature, and processing conditions to achieve a desired thickness distribution and minimal weight of a truck fairing part without sacrificing its structural performance.
The given design of truck roof fairing part is simulated using Accuform’s commercial thermoforming simulation software TSIM® for three different resin materials (acrylonitrile butadiene styrene (ABS), a blend of polycarbonate (PC) and ABS (PC/ABS); and thermoplastic olefin (TPO). These materials are modelled using nonlinear time-dependent viscoelastic K-BKZ model. The model parameters are estimated using stress-strain measurements. The average polymer sheet thickness and sheet temperature of each material varied to study thickness distribution and weight of the part. Finally, simulation results compare the thermoforming performance in terms of thickness distribution and part weight, and recommends optimal processing conditions for each material.
A Hansen Compatibility Approach in Understanding Solvent Bonding Between Acrylic Copolymers
Flexible PVC is the tubing of choice used in infusion therapy applications as well as other medical devices applications. But the health risk awareness for the plasticizer (Diethylhexylphthalate) DEHP in flexible PVC is gearing the industry to seek alternative tubing materials. Solvent bonding between two materials is a common joining technique that relies on compatibility between the substrate polymers to the tubing material for fabricating medical assemblies. Solvent is the integral component to swell the joining components and allow intermingling, diffusing and sealing the joint. In this study, we present solvent bonding as a versatile fabrication technique for joining various plastic materials to medical tubing. Acrylic copolymers, (specifically CYROLITE® GS-90 manufactured by Roehm America LLC) are tested for bond strength against four different tubing materials, namely non-DEHP-PVC, TPU, Polybutene, and Silicone, using solvent bonding. A variety of industrially accepted solvents such as Acetone, Methylethylketone (MEK) and Cyclohexanone/MEK were tested. These solvents demonstrated strong lap shear pull force strength, replacing the carcinogenic Dichloromethane (DCM), DCM/Glacial acetic acid 90/10 or the more aggressive stress-crack inducing 100% Cyclohexanone solvents. The article also describes Hansen solubility parameter as an engineering mechanism in determining miscibility and understanding the bonding performance of acrylic copolymers, and other medical plastics such as medical grade polycarbonate (PC), and Methyl methacrylate Acrylonitrile Butadiene Styrene (MABS) to various tubing materials.
Influence of the Plug Roughness on the Wall Thickness Distribution in Plug-Assisted Thermoforming
Thermoforming enables the cost-effective production of thin-walled packaging products. Pre-stretch plugs are used to adjust the resulting wall thickness distribution of the formed parts such as cups. Due to the friction and adhesion of the plastic material to the pre-stretch plug, the material is less stretched in areas having contact to the plug than in areas without contact and accordingly the wall thickness distribution is influenced. In addition to a wide range of process parameters, such as sheet temperature, stretching distance or the activation time of the forming air, the surface roughness of the pre-stretch plugs has an influence on the wall thickness distribution. In order to estimate the resulting wall thickness distribution of the formed parts, the influence of the surface roughness on the resulting wall thickness distribution was analyzed at the IKV. The use of pre-stretch plugs with different surface roughness showed, that the influence of the roughness on the wall thickness distribution depends especially on the plugs geometries and thus stretching conditions of the sheet.
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