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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Jessica Lin, Shih-Po Sun, Tung-Huan Su, David Hsu, May 2017
We introduced in this paper a simulation tool designed to predict the most common defects related to the in-mold decoration process. Ink-wash is the most obvious aesthetic problem caused by high temperature or high shear from the incoming melt. Warpage is another dimensional uncertainty defect due to the poor heat conduction of the film. Overcoming these problems often requires mold fixing including critical gate location change. Mold filling simulation could help identify these potential problems in the early mold design stage. However, conventional simulation techniques require tedious work of thin layer mesh making of the decoration film. It is therefore essential to develop a quick preprocess tool without losing simulation accuracy.
Jessica Lin, Huan-Chang Tseng, Chia-Hsiang Hsu, Rong-Yeu Chang, May 2017
Long fiber-reinforced thermoplastic composites open up exciting new possibilities for the green automotive industry, owing to excellent mechanical properties, advantageous weight reduction, and economical fuel consumption. However, fiber microstructure including fiber orientation and fiber length, is a very critical issue to cause anisotropy in mechanical properties and warps. For an injection-molded, long-glass fiber composite part, we use Moldex3D to obtain an accurate fiber orientation prediction. Thus, mechanical properties depending on the predicted orientation is calculated via Digimat. It is ultimate to explore changes in stress with respect to strain in the ABAQUS structural analysis. All of the predictions are compared with experiments herein.
In this paper, we investigated the effect of multi-walled carbon nanotubes (MWCNT) on the foaming behavior of poly(e-caprolactone) (PCL). The PCL/MWCNT nanocomposites prepared using HAAKE Rheometer, and the resulted composites were subsequently foamed using supercritical carbon dioxide (Sc-CO2) foaming technology. Results showed that the involvement of MWCNT promoted crystallization of PCL matrix and improved the crystallinity of PCL matrix, which is attributed to the enhancement of melt strength. Morphological analysis presented that the MWCNT was well-dispersion in the PCL matrix at low loading. In Sc-CO2 foaming process, the addition of MWCNTs led to higher cell densities, smaller cell sizes and uniform cell morphology in the composite foams. The results indicated that the MWCNT nanoparticle acted as a heterogeneous nucleation agent in the PCL matrix, and provided more nucleation site during the foaming process.
Polyolefin seal layer was incorporated into crystalline PET (CPET) rigid packages (e.g. trays) to better control the seal and peel performance. The adhesion bond between polyolefins to CPET is destructive and inseparable, which exceeds common means of bonding technology (e.g., adhesives or tie layers) and prevents delamination while peel strength can be tuned with different easy peel lidding options. This new product was also passed preliminary tests under retort and oven conditions. Regrind with PE surface was studied in order to reclaim flakes in the CPET manufacturing process and the compatibility of PE matrix with PET was further analyzed.
Peng Liu, John Lindahl, Ahmed Arabi Hassen, Vlastimil Kunc, May 2017
The influence of hollow glass microspheres (HGM) on the rheological properties of a commercially available Acrylonitrile-butadiene-styrene (ABS) polymer was investigated. ABS/HGM composites were prepared with various HGM contents. The rheology of the ABS/HGM composites was characterized to provide insight into the influence of the temperature and sphere concentration on the flow behavior under shear. Linear viscoelastic measurements show that both complex viscosity and storage moduli exhibit about 4 orders of magnitude increase with increasing HGM concentration from 40 vol% to 50 vol%. The viscosity increase is more pronounced at low frequency shear rates.
Rotational molding shows the potential to build up multi-layer parts by sequential adding of different materials into a rotating cavity. The limited compatibility of several materials to each other reduces the potential material combinations significantly. Former investigations showed the general applicability of a multi-phase interlayer to bond incompatible materials during the rotational molding process. Within this interlayer interlocking occurs between the two materials. This work investigates the influence of particle size on the material distribution and peel strength for the material combination Polyethylene and Polyamide 12. It is shown, that the material distribution is depending on the particle size added to generate the interlayer whereas the peel strength is mostly unaffected if the interlayer thickness exceeds the particle size. For thinner interlayers smaller particles show higher peel strengths and a varying interphase region.
Canfor’s Prince George Pulp & Paper Mill in Prince George, BC, Canada operates a bleach plant effluent system for the production of Bleached Kraft Pulp. The original underground fiberglass reinforced pipe (FRP) presents an elevated risk to both environment and production targets. Over the past five years there have been over 10 repairs required to maintain integrity of the pipeline. The primary objective of the project was to create a more reliable pipeline and reduce the risk of a major leak event and subsequent consequences. With temperatures up to 75°C, standard PE4710 materials were not suitable for this application. A brand new PE-RT product that expands the use of PE into larger diameter industrial applications allowing continuous operating range from -45°C to 82°C with intermittent temperatures up to 95°C was selected to replace the underground fiberglass piping.
Iván D. López, Juan C. Ortiz, Alexander Hernández, Omar Estrada, May 2017
Energy efficiency of injection molding is critical to increase the sustainability indexes of this process and to reduce production cost. The Energy Gap Methodology (EGM) is presented as a valuable tool to prioritize the interventions to increase the energy efficiency in injection molding and other polymer processes. This methodology identifies four gaps: production, process, technological and R&D gaps. Three industrial successful case studies reducing energetic gaps in injection molding are presented, obtaining specific energy consumption (SEC) reductions between 9 and 15%.
Giovanni Lucchetta, Davide Masato, Marco Sorgato, May 2017
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.
Torsten Maenz, Andreas Jakobinski, Gerrit Hülder, Michael Gehde, May 2017
Thermoset molding compounds are showing great potentials in applications that demands high temperatures, high media resistance and good mechanical properties. Customized properties such as enhanced heat conductivity or magnetic properties that can be achieved through functionalization are often sought after in the thermoset as well as in the thermoplastic industry. This paper deals with the orientation of magnetic and heat conductive fillers in epoxy molding compounds, which are essential for part design and process control.
Jasmin Mankiewicz, Michael Heber, Ernst Cleve, Jochen S. Gutmann, May 2017
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.
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.
Susan Mantell, Evan Cosgriff, Mrinal Bhattacharya, May 2017
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.
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.
Christian Marschik, Wolfgang Roland, Bernhard Löw-Baselli, Jürgen Miethlinger, May 2017
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.
Yannick Martin, Elmar Moritzer, Björn Landgräber, Stefan Seidel, May 2017
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.
Davide Masato, Jitendra Rathore, Sorgato Marco, Giovanni Lucchetta, Simone Carmignato, May 2017
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.
Laurent M. Matuana, Sonal S. Karkhanis, Nicole M. Stark, Ronald C. Sabo, May 2017
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 (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.
Ethan McCarthy, Stephen Johnston, Maria Barsom, James DiNunzio, May 2017
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.
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