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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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.
Influence of Processing Route on the Properties of Polyolefin Blends
One of the streams from plastics waste collection is a mixed polyolefin stream, which cannot be separated completely with reasonable effort at the current technological state. The aim of this work was to investigate the influence of the processing route, realized by different plastic processing machines, on the properties of selected polyolefin blends, made from different PP and PE grades as well as compatibilizing additives, to mimic the mixed polyolefins found in post-consumer waste. We found, that the processing route influences the properties in regard to the shear brought into the materials – only dry-blended and injection molded blends yield lower properties than the ones which were prepared by the other processing machines. This is more pronounced when compatibilizers were added. These results show that several processing machines can be used to establish such blends, which is an important finding for mixed polyolefin stream recycling, as there not only a good mixture in the blend needs to be established, but also the processing machine has to be stable and unsusceptible to foreign materials in the stream.
Analysis of Parameters for Heat Sealing and Ultrasonic Sealing of PET/PE Films.
Sealing of laminated polymer films is done by applying/generating heat in the seal area. Heat causes the low melting point inner layer to melt and intermolecularly diffuse with a matching layer, creating a joint. Two common processes for sealing are heat sealing and ultrasonic sealing. Different process parameters for both heat sealing and ultrasonic sealing were evaluated individually in order to find a relationship with peel strength. For this experiment a two ply film of PET/PE was used. In heat sealing, increasing the sealing temperature and sealing time caused an increase in peel strength. Increasing heat sealing pressure decreased peel strength. However, this was shown to be due to excessive pressures, which resulted in PE squeeze. In ultrasonic sealing, the effects of weld time and weld force on peel strength were evaluated. For ultrasonic weld time, initial increases caused large changes in peel strength with subsequent changes being less pronounced. Similarly, for ultrasonic weld force, initial increases in weld force caused increases in peel strength. However, at higher weld forces, peel strength decreased due PE squeeze out.
Some Properties of 100% Recycled Ocean Plastic Polyolefins
Levels of plastic waste accumulating in the oceans are continuously rising and prompting an increase in concern on their negative environmental impacts. To help close the gap and create a circular life cycle for ocean plastics, this study begins to show the changes in chemical and engineering properties of polyolefins collected from a marine environment. Three ocean plastic polyolefins, high density polyethylene, low density polyethylene, and polypropylene, were mechanically recycled and then injection molded. The ocean plastics‚Äô chemical characteristics were then characterized via FTIR to observed the impacts of environmental degradation. Thermal, rheological, and mechanical properties were all studied and related to the chemical structures and typical accepted values. All ocean plastic olefins were found to have properties similar to their terra-firma counterparts, however degradation was observed and is discussed in terms of the measured properties.
Characterization of polypropylene/hydrocarbon resin blends for 3D printing
Additive manufacturing (AM) of polyolefins, such as polypropylene (PP), employing filament-based material extrusion (MatEx) has gained significant research interest in recent years. The semicrystalline nature of PP makes it challenging to process using MatEx. The addition of amorphous low molecular weight hydrocarbon resins into PP matrix was found to delay the onset of crystallization of the blends. The slow crystallization behavior, as evident by the increased crystallization half-times, aided the relaxation of residual stresses during MatEx of PP blends that resulted in manufactured parts with reduced warpage. Rheological characterizations were performed on the PP blends revealing the shear-thinning nature. The combined interaction among crystallization rates, timescales, and morphology was found to affect the interlayer welding process during MatEx. Mild thermal annealing of the manufactured parts resulted in mechanical properties which approach that of injection molded parts.
Styrenic Block Copolymers for Enabling Improved Performance of Post-Consumer Resins
Improving the reusability of plastic parts, increasing the usage of post-consumer resin (PCR), and converting mixed PCR streams into high value resins are three key challenges facing the plastic recycling industry. To address these challenges, CirKular+‚Ñ¢ products were developed by Kraton Polymers to enable plastics upcycling and circular economy solutions. These products enable multi-resin compatibilization and performance enhancement of PCR resins across a wide range of applications. By leveraging the versatile chemistry of styrenic block copolymers, polymeric additives have been developed that benefit plastic recycling in multiple ways, such as improvement in properties of recycled resins and blends of virgin and recycled resins, and compatibilization of mixed PCR resin streams. In addition, these polymeric additives provide the performance enhancement at low loading levels, which in turn leads to an excellent balance of properties and low formulation cost. In this paper, several application-specific test results and case studies will demonstrate the value of these polymeric additives.
Sustainable Processing Aids to Enhance the Performance of Plastics with Recycled Content
In response to government and consumer demand for sustainable solutions to the escalating plastic waste crisis, plastic compounders and manufacturers are seeking to increase the level of post-consumer recycled content in their product formulations. The inherent variability of recycled resin streams presents challenges related to operational efficiency and product performance; thus, there is an increased need for processing aids that can assist manufacturers in their quest to balance operational efficiency with sustainability. GreenMantra¬Æ Technologies has developed and commercialized an innovative advanced chemical recycling technology that converts recycled plastics into specialty polymers and synthetic waxes that can function as processing aids in plastic production. This paper presents two case studies that demonstrate how GreenMantra‚Äôs additives enhance the manufacturing efficiency of plastic extrusion processes and maintain the physical properties of polymer systems containing 25-100% recycled plastics. Certified as containing 100% post-consumer recycled plastics, GreenMantra‚Äôs additives enhance the sustainability of the polymer system while enabling the formulation flexibility for plastic manufacturers to incorporate higher recycled plastic content without sacrificing performance.
Product-Related Process Data Acquisition in Blown Film Extrusion
In today’s advanced plastics processing industry, a quality-based control of an entire production line is desirable. This requires a product-related process data acquisition allowing to merge process data and quality data with high accuracy. In this context, an approach for the blown film extrusion process will be presented. An experimental study confirms that the tool of residence time distribution analysis is suitable to identify the system behavior of a blown film line. On that basis, suggestions are made on how to proceed with the implementation of a product-related process data acquisition.
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