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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Reduction of Energy Consumption in Injection Molding of Polypropylene Parts through the Optimization of Mold Thermal Control
The environmental impact of the injection molding process is mostly due to electricity consumption. This is particularly significant for packaging applications, which are the largest application sector for the plastics industry. In this work, electricity consumption measurements of the process were performed, considering a large packaging plant. In particular, the energy consumption related to mold thermal control were analyzed and minimized through a representative case study. The effects of alternative cooling channels configurations and different process parameters were experimentally investigated, considering also their influence on the quality of the molded parts. The results indicated that the common industrial practice for mold thermal control is highly inefficient. The implementation of electricity consumption measurements allowed the optimization of molds thermal control leading to considerable economic savings.
Material Characterization of CF-Nonwovens with Thermosetting Matrices
Regarding the need of robust and lightweight materials there is an increasing market for carbon fiber (CF). Therefore blending fabrics produce a huge amount of valuable process waste like prepregs which are out of specification and end-of-life products. The carbon fiber is regained from polymer matrix by new recycling methods. These fibers are chopped and can be reused for manufacturing isotropic fleece by wet-laid process. Created fleeces are impregnated with thermosets by resin transfer molding (RTM). At the beginning the isotropy of the fleece is verified by a circular disk and a 4-point bending test. After that the influence of different fiber surface weights and homogeneity, as well as no significant effect of various dispersing agents are identified. In addition to that the interrelation between fiber volume content, fiber length and specific values (tensile strength, flexural stiffness, Young's modulus) is analyzed. Referring to the results for thermosets with virgin fibers the process is transferred to recycled fibers.
Micro Molding with Bioabsorbables: Not Your Average Thermoplastics
This whitepaper explores Micro Molding with Bioabsorbables. For micro medical components, there is a wide variety of materials to choose from and many new micro medical applications are relying on bioabsorbable materials because the materials dissolve or absorb into the body, eliminating the need for additional surgeries and minimizing concerns about adverse effects.Across the board with plastics, the rules are different when you mold it so small. But when it comes to bioabsorbable resins, they require a much more extensive and specialized approach than thermoplastics. By understanding how processing bioabsorbables differs from thermoplastics, medical OEMs can understand the key factors needed for optimizing the design and production of their bioabsorbable products.
Method for Degrading Polyethylene Sheet Samples in an Oxidative Environment
Stress cracking is a failure mode that must be considered when evaluating the lifetime of polymer components. In modeling this failure mode, mechanical properties as a function of the extent of degradation must be evaluated. This paper describes an apparatus and method for degrading thin polymer sheets in an oxidative environment. A model system of PE in hot chlorinated water with an oxidation reduction potential of approximately 825 mV is considered. The oxidative environment is achieved by a water bath with temperature, pH and free chlorine controlled to 60-65°C, 5.2 +/- 0.5 ppm free chlorine, and 6.3 +0.5/-0.0 pH. Under these conditions, the molecular weight of 50-60 micron thick PE sheets was reduced by 60% and the strain at break for the sheets was reduced by 90% after 1000 hours exposure.
Improving the Patient Experience of Your Drug Delivery Using Polymers with Improved Tribology
In medical and pharmaceutical devices, such as injection pens, inhalers, lancing devices or surgical instruments, metal and ceramic components are increasingly being replaced by engineering polymers. Their light weight and the dimensional accuracy derived from precision molding, combined with good wear resistance and low coefficients of friction, often make engineering polymers a better solution than metal. In many medical and drug delivery devices the device components must slide against each other in complex systems containing multiple materials. To allow the device to work smoothly, particularly in the activation of the device, they must not create noise, wear or too much friction, and retention of low and consistent activation forces during the life-time of the drug delivery device are required. This performance has to be achieved in sophisticated designs, across a range of temperatures, different chemical environments, and with a range of speeds and forces in operation. This presentation reviews common engineering polymers, the benefits and disadvantages of external lubrication and gives insight into a smart material selection process. Slip and wear properties are described as well as scientific analytical methods to deliver optimal performance, reduced risk of failure and increased patient comfort.
Modeling Three-Dimensional Non-Newtonian Flows in Single-Screw Extruders
Modeling the multidimensional non-Newtonian flow of shear-thinning polymer melts in single-screw extruders generally requires the use of numerical methods. We present a heuristic approach to predicting the three-dimensional, fully developed, isothermal flow of power-law fluids in single-screw extruders that avoids complex and time-consuming numerical simulations. By applying a heuristic optimization algorithm, we approximate numerical results obtained from a comprehensive parametric design study, yielding an analytical relationship for the output-pressure gradient relationship depending on four independent parameters: (i) height-to-width ratio (h/w), (ii) pitch-to-diameter ratio (t/Db), (iii) power-law index (n), and (iv) dimensionless pressure gradient in the down-channel direction (pp,z). The new approach is demonstrated to provide a close approximation to numerical solutions.
Modeling and Simulation of the Inflation Step in the Two-Stage Gitblow-Process
The innovative two-stage GITBlow process combines the advantages of injection molding and blow molding. This is achieved by producing a preform using gas-assisted injection molding, which is then inflated by a second gas injection within a larger cavity in the same mold. The components obtained have a large volume/wall thickness ratio, while, at the same time, featuring elements that are typical of injection molded parts, e.g. ribs. This paper presents the simulation of the inflation behavior under consideration of inhomogeneous preform temperature. For this purpose, a spring-dashpot model is developed to describe the viscous and viscoelastic behavior of the plastic material. The findings obtained in the simulations are then verified with experimental results.
Effect of Fiber Orientation and Process Parameters on Shrinkage in Injection Molding of Thin-Wall Parts
Injection molding of high quality thin-wall parts is a challenge due to the high values of the shear stress in the melt flow, which affect the morphology of the moldings and their consequent shrinkage and warpage. In this work, the effect of the injection molding processing conditions on the dimensional accuracy of thin-wall fiber-reinforced parts was studied. The reduction of the shrinkage was taken in consideration analyzing how processing parameters affected the final dimensions of a specifically designed part. Moreover, the relation between the distribution of short glass fibers within the part and its dimensional accuracy was investigated by means of X-ray micro computed tomography. The experimental results showed that a selection of high values for both melt temperature and packing pressure allowed the minimization of the dimensional difference between the mold and the final parts. The analysis of the cross sections of the thin-wall parts, obtained from the micro computed tomography scans, allowed the observation of the `skin-shear-core' morphology indicating that the thickness ratio between the shear and core layers is affected in particular by the injection speed.
Effect of Compounding Approaches on Fiber Dispersion and Performance of Poly(Lactic Acid)/Cellulose Nanocrystal Composite Blown Films
This study was aimed to identify the best approach for incorporating cellulose nanocrystals (CNCs) into a poly(lactic acid) (PLA) matrix by examining two different CNC addition approaches. The first approach consisted of melt blending PLA and CNCs in a three-piece internal mixer whereas the second method involved the direct dry mixing of PLA and CNCs. The prepared compounded materials were then blown into films and compared in terms of fiber dispersion, optical, thermal and barrier properties. The experimental results indicated that the extent of fiber dispersion was not influenced by the CNC addition method, i.e., good dispersion was achieved by either method. However, the melt blended PLA/CNC films thermomechanically degraded during the melt blending process. Consequently, the melt blended PLA/CNC films had inferior properties than their direct dry blended counterparts. Thus, the direct dry blending process appeared to be the best approach of incorporating CNCs into the PLA matrix.
TUBALL™ Single Wall Carbon Nanotubes: A New Additive for Thermoplastics
TUBALL single wall carbon nanotubes (SWCNT) is a new SWCNT product developed by OCSiAl and produced at an industrial scale. It exhibits unique characteristics making it an excellent candidate to enhance material properties and to impart electrical conductivity to plastics. SWCNT allow the formation of a conductive network much more efficiently than other conducting fillers. A network of nanotubes can be established at very low additive dosages which results in a minimal influence on the other material characteristics. Investigations have been conducted to determine the possibility to prepare composites based on SWCNT using standard melt mixing equipment, such as twin screw extruders, to enable large scale adoption. This paper is primarily focused on polyolefins and demonstrates that a two-step compounding approach involving an initial masterbatch preparation enables compound development showing very low percolation thresholds. A range of parameters related to process conditions, including the effect of process temperatures, screw speed and profile or feeding conditions, have been investigated to determine their influence on the final performance. This study indicates that SWCNT can be considered as an additive for superior conductive performance for the masterbatch and compounding industry that will support the growth of high performance materials.
Melt Extrusion and Injection Molding for the Development of Pharmaceutical Mini-Tablets – Case Study Using Clotrimazole
Injection molding and hot melt extrusion are well developed plastic forming processes that have recently been garnering more attention in the pharmaceutical industry. The use of these thermal processing techniques reduces the need for hazardous solvents in order to create amorphous solid dispersions, which can improve the efficacy of poorly soluble drug compounds through increased solubility and bioavailability. This article describes the application of hot melt extrusion and injection molding to create pharmaceutical doses using clotrimazole in hydroxypropylcellulose.
Latest Developments in TPO Stabilization for Automotive Applications
In the past few years started a race for performances in TPO compounds for Automotive applications. Lighter, stronger, more durable, better aesthetics, more sustainable, less smell, a large amount of requirements for a given part in vehicles is making new developments more and more demanding and challenging. Clariant Business Line Polymer additives, specialized in polymer stabilization, is introducing new solutions which provide most of the current performances requested by the OEMs and beyond. Heat and light stabilization, low odor, surface appearance, low/no blooming are some of the qualities provided by this new range of products dedicated to Automotive TPOs under the AddWorks terminology. Specific AddWorks have been developed for Interior, Exterior and Under-the-Hood applications, and will be presented here.
Strain Analysis of HDPE Butt Fusion Joint in Side Bend Test
The standard practice ASTM F3183-16 (F3183) has been developed for conducting a three point side bend test to evaluate the ductility of a polyethylene butt fusion joint, but our understanding of the bending strains that are applied across the specimen during the test is far less than desired since there are no test values provided by the practice. In this paper we perform the strain analysis through grid method to investigate the strain level applied to the specimen. The present paper provides the results of strain levels at different bending angles for various selected combinations of loading nose radius and specimen thickness and then compares them with the estimated strain from pure bending theory. The experimental results show the strains increase with the bending angle and are higher than the estimations when the bending angle is larger than 60°. In addition, we conduct the side bend tests in three different temperature conditions to address the effect of temperature on the strain levels applied to the specimen at a given bending angle. The test results show that the higher strains are applied to the specimens at a lower temperature. In general, the present work will be a good resource to assist in the employment of the standard practice F3183 and advance our understanding of the process of the side bend test.
Processing of In-Plant Mechanically Recycled PA-12
The increasing public awareness and demand for a more sustainable handling of the earth’s resources has led to the idea/ concept of a circular economy. Within this concept materials will be re-used in a closed loop system rather than being down-cycled or inappropriately managed (disposed via landfill) at the end of their life-cycle. Based on previous research, Polyamide 12 (PA-12) is a promising material candidate in the sports and leisure sector and its ability for being reprocessed via injection molding has been investigated. While other PAs tend to show a decrease in impact properties on mechanical recycling, PA-12 is shown to be able to overcome these problems when reprocessed at a higher melt temperature, yielding samples with improved impact properties compared to the primary material.
Injection Moulding Pilot Production: Performance Assessment of Tooling Process Chains Based on Tool Inserts Made from Brass and a 3D Printed Photopolymer
Additive Manufacturing is becoming a viable option for the production of injection molding inserts in pilot production settings. This work compares an insert made from brass using conventional machining with an insert made from a proprietary photopolymer using Digital Light Processing (DLP) through the application of precision injection molding. The performance of the inserts is analyzed focusing on design, metrological aspects, tool lifetime, and thermal performance. In the experiment, a disk-shape geometry (diameter 41.5 mm, thickness 3.5 mm) was injection molded in Low-Density Polyethylene in a two-cavity mold. The inserts as well as selected injection molded parts were analyzed with an optical 3D micro-coordinate measuring machine. It was found that additive manufacturing technology can lead to a significantly more cost effective pilot production, both in terms of development time and investment. DLP technology enables fast production of micro-features, however insert production with DLP is less reliable than milling e.g. when considering process repeatability. Photopolymer and brass inserts lead to differences in optical surface appearance on the injection molded parts. The lifetime of the photopolymer inserts is challenging to predict reliably. Depending on how many parts need to be produced, the use of several photopolymer inserts instead of one brass insert is a means to overcome the shorter lifetime and can represent a cost-effective alternative to machined inserts. In order to exploit the advantages of using additive manufactured injection mold inserts, specific tool design rules have to be applied.
Multilayer EVOH/HDPE Packaging in Processing and Performance of Recycled HDPE
Kuraray, EVAL Europe N.V. (EE) produces Ethylene Vinyl Alcohol copolymers (EVAL™), which are used in multilayer structures in a combination with a wide range of materials such as High Density Polyethylene (HDPE) to produce multilayer bottles to provide superior barrier properties to gases, flavours or bring functional barriers against external contaminants such as mineral oils (MOSH,MOAH). Bottles are typically made by Co-Extrusion blow moulding (Co-EBM) technology and are used for beverage packaging such as dairy products and specialty milk and other packaging applications for sauces or dressings or for the packaging of medical products for which the Water Barrier of HDPE is of added value. The objective of the study was to investigate if multilayer EVOH/HDPE rigid packaging material, which is a percentage of the post-consumer recycling stream, can be effectively sorted with the HDPE stream and decontaminated back to food grade approved for use as Post-Consumer Recycled (PCR)-HDPE into food packaging applications. Multilayer rigid food packaging found in the post-consumer recycling stream has been represented in the design of materials guides and recycling guides as ‘may be suitable’ for recycling. The present work investigates the recyclability of EVOH barrier packaging due to the growing trends of multilayer rigid food packaging and more importantly, as recovery systems strive towards a better circular economy. The steps taken to produce food grade rHDPE with analysis included; Audits of the HDPE fraction at Viridor MRF, testing on automated NIR sorting equipment at Tomra (Titech), compounding in a low pressure, elevated temperature, food-grade decontamination process and overall migration testing conducted by Smithers-Pira. The evaluation showed that post-consumer HDPE (rHDPE) material containing at least 0.25% EVOH (equivalent to 5% multilayer EVOH/HDPE packaging) can be “super cleaned” to food grade quality without any significant impact on the process performance or physical properties compared to rHDPE only. The results showed that at the levels of multilayer EVOH packaging typically found in the recycled HDPE stream, the rHDPE can be processed and utilized in a full range of applications, without impact on migration characteristics or physical properties compared to rHDPE alone.
Back Injection Molding with Additive Manufactured Mold Inserts Using All-Inkjet Printed Substrates
Back injection molding is a well-known process in the plastics industry. For example, the fabrication of decorated interior parts in the automotive industry is one of many fields of application. In the last few years, the additive manufacturing process rapidly expanded in injection molding. For instance, it is used for producing injection mold inserts made of metal or plastic. This technique is called Rapid Tooling. The aim of this paper is to investigate the back injection molding process with additive manufactured mold inserts made of Fullcure RGD 720 and to verify if this technique is feasible. Therefore, a substrate with all-inkjet printed conductor traces was placed in the mold insert. The injection molding was done with a standard injection molding machine. The conductive traces were printed with a standard inkjet printer manufactured by Epson. To generate additional information about the additive manufacturing material Fullcure RGD 720 a differential scanning calorimetry (DSC) was done.
Influence of Long-Term Annealing on Residual Stress Distribution and Quasi-Brittle Failure Properties of Talcum Reinforced Pipe Grade Polyproyplene
In this study a polypropylene material with talcum reinforcement used for sewer pipes has been subjected to an annealing procedure at 80°C, roughly 60°C above the actual application temperature, in air for a time period of 18 months. As expected, examination of the material showed no significant decrease in mechanical or fracture mechanical properties due to the temperature exposure. However, samples stored at higher temperature showed better resistance against quasi-brittle failure in fatigue tests compared to unconditioned samples. This could mainly be attributed to the decrease of residual stress in the pipe wall. Even though pipes have been annealed for very long times above Tg, residual stress could not be totally relaxed within 18 months.
Creep Deformation Behaviour of Pc-Abs Parts Processed by Fused Deposition Additive Manufacturing under Different Extrusion Parameters
Fused deposition modeling (FDM) is a complex process for many additive manufacturing practitioners as it involves selection of a large number of intervening process conditions to produce quality products to meet customer needs and achieve competitive advantages. Understanding the effect of operating conditions on the mechanical properties of FDM printed parts is an important task as they influence the functionality of the products. The growing demand for use of Polycarbonate /Acrylonitrile-Butadiene-Styrene (PC-ABS) alloys in the production of automotive components led to the need for understanding the creep deformation performance of processed material and product under various processing parameters. This study investigates the effect of FDM process conditions on creep deformation behaviour. A systematic study through definitive screening design and statistical analysis was carried out in order to correlate the FDM processing parameters with the performance of PC-ABS alloys. In this study, the regression model was developed for the calculation of the processing parameters in FDM of PC-ABS products and gives technical information for the determination of which process parameters are the best to use for practical purposes.
The Influence of Plastics Processing on the Biocompatibility of Medical Products
Medical products must be biocompatible depending on application. However, numerous factors can negatively affect biological compatibility. Plastics processing can lead to degradation of polymer molecules via various process parameters such as processing temperature. These degradation products can have a negative influence on biocompatibility. The aim of these initial investigations is to explore the influence of injection molding on the biological properties of medical products. Comprehensive analyses of processing parameters, polymer degradation and its degradation products, as well as the cytotoxicity of various medical-grade plastics are presented. That processing parameters can significantly influence the final product's biocompatibility for certain materials is shown. Thus the release of formaldehyde during POM processing is demonstrated to have a cytotoxic effect on medical products.
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