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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Influence of Additive Type On the Properties of Polyolefin Blends
The aim of this work was to compare the effects of compatibilisation with different additives on the properties of polyolefin blends, made from different PP and PE grades, to mimic the mixed polyolefins found in post-consumer waste and investigate ways to improve the properties of these mixtures. We found, that it is possible to compatibilize such polyolefin blends via the addition of ethylene-octen- or olefinic-block copolymers, where the type of copolymer shows an influence on the properties achievable. Also the blends show differently improved impact behavior, depending on the polyolefin which builds the major phase of the blend. These results show that it is possible to recycle such mixed polyolefin streams towards a suitable material with reasonable properties.
Influence of Variothermal Temperature Control on the Weld Line Quality of Extrusion Blow Molded Articles
Extrusion blow moulding enables the cost-effective production of plastic hollow bodies with complex geometries and different volumes. The majority of the components are used as packaging articles for the consumer goods- and food industries or as technical components, e.g. in the automotive and chemical industries. Extrusion blow moulded products are often failing at the weld line. The quality of joint depends mainly on the welding temperature. In order to improve this critical area, the IKV is investigating the use of variothermal temperature control of the blow mould. This brings the advantage of being able to locally increase the temperature of the blow mould. By using this temperature control concept, the results show a significant improvement in the quality of the weld line.
Inline Surface Activation in the Multi Injection Molding Process
Surface activation by plasma is a widely used process technology for connecting several components to each other. Usually, the activation takes place outside the injection molding machine as an additional step. With the development of the InMould-Plasma technology, the surface activation is fully integrated in the injection molding process, which eliminates an additional process step. Therefore, a plasma nozzle is directly connected to the mold. The plasma runs along a defined channel and activates the substrate surface in the closed mold. Through the technology, a strong bond of originally incompatible materials has been achieved. Without a surface activation, there is no adhesion of polypropylene (PP) and thermoplastic polyurethane (TPU). Studies on the peel strength of PP with TPU show that a treatment time of 5 s can drastically increase the material compatibility and achieve a peel strength of > 12.5 N/mm over the entire treatment area.
Intelligent Hybrid Hot Runner System for Optimized Polymer Products
A novel “Rheo drop” concept is developed to advance the process of injection molding with hot runner systems. It controls shear rate during injection molding process in the hot drops, allowing us to process the material at lower temperatures since the viscosity can be reduced by increasing shear instead of increasing the temperature. Also, maintaining lower viscosity at the hot drop will prevent slug formation that causes incomplete filling defects when manufacturing thin walled parts. This innovative idea is suitable for temperature sensitive materials as they might degrade when subjected to excessive heat for longer periods. Analytical and experimental investigations were performed to validate the developed “rheo drop” concept. Simulations were performed using ANSYS fluent and the results confirmed that the concept was able to produce a sufficient amount of shear to significantly reduce the dynamic viscosity between injection molding cycles. To validate the concept experimentally, a hot runner mold was modified to retrofit the rheo drop technology. The results showed that the new concept was able to solve one of the molding significant issues, which is a defect that is caused by incomplete filling.
Internal Damping and Its Variblity of Polyamide 6.6-Based Materials
This paper should help engineers and designers to make best possible use of PA66-based engineering materials in the context of components that are subject to vibration or the damping of vibrations in automotive. It will provide results from material testing, discuss these results and provide guidance, how these measurement results translate into components. Proven concept to reduce the propagation of vibrations is the use of elastomer elements as damper for example at bearing points within the suspension system or in engine mounts. With thermoplastics being introduced to also the rigid parts of these systems, there is an additional potential to eliminate vibrations thanks to the viscoelastic behavior of this class of materials. PA66-based materials are widely used for components in the engine compartment and the suspension system because of their capability to provide sufficient mechanical properties, thermal stability and chemical resistance. The goal of this paper is, to highlight the influence of glass fiber reinforcement, impact modification and humidity content on the damping behavior of PA66-based materials and to explain the variability of the internal damping as a function of these variables.
Investigation of Glass Bubbles iM16K Polyamide 12 Composites for Selective Laser Sintering
Selective Laser Sintering is an additive manufacturing technique that has been increasingly exploited in small-batch production to supplement traditional polymer processing techniques. Integrating specialized additives with PA12 SLS powder allows for the production of parts with tailored properties. 3MTM Glass Bubbles iM16K offers the possibility to reduce SLS powder cost, reduce part weight, and improve mechanical performance. Both intrinsic and extrinsic properties and their effects on SLS processing have been investigated. Tensile testing revealed the average Young’s modulus could be improved by 30% at 5 wgt% loadings, while maintaining ultimate tensile strength.
Keynote: Structural Characterization of Hybrid Composites with Graphene to Increase the Use of Light Weight
Injection molded composites have been used effectively in automobiles, but there is still a need for the development of lighter and greener materials. Hybrid composites, composites with multiple kinds and length scales of fillers, present the opportunity for exciting new material breakthroughs and the opportunity for finely engineer the performance of the manufactured materials. This study presents the structural testing results for a hybrid composite composed of a blend of glass fibers with graphene nano-platelets within a PA6 matrix. This blend is chosen to meet the high demands of the automotive industry for select under the hood applications. The results presented in this work demonstrate that the addition of less than 1% by mass of graphene nanoparticles can allow the reduction of glass fillers by nearly 25% with only a minimal reduction in performance while reducing the density increase relative to the neat polymer by nearly 20%.
Long- and Short-Term Tensile Strength and Morphology of Joined Beta-Nucleated Polypropylene Parts
This paper presents the results of static short-term and long-term tensile tests for beta-nucleated joined polypropylene samples by the hot plate welding process. In the present study different dimensionless joining displacements are accounted for. The results show that high short-term tensile strength does not directly transfer to high long-term tensile strength. The morphology of the weld seam in the joined samples is examined by means of transmitted and reflected light microscopy. For the dimensionless joining displacements of 0.75 and 0.95, stretched spherulites are obtained. X-Ray diffraction can be used as a tool for qualitative and quantitative analysis and eventually for differentiation of samples of various joining displacements.
Low- and High-Pressure Foam Injection Molding of Polypropelene/Talc Through Chemical and Physical Foaming Agents
Recent research in the area of advanced polymer processing has demonstrated the potential of foaming agents to introduce additional functionality within injection molded components. In this research, Talc filled Copolymer Polypropylene (PP) ISO standard tensile bars were produced through low- and high-pressure foam injection molding (FIM). Two chemical blowing agents (CBA), Microcell® 548 and TecoCell® H1, in addition to N2, a physical blowing agent (PBA), were processed at both low-pressure and high-pressure configurations. The 2 foaming configurations were used to create parts with weight reductions of 12.6% and 8.8%, respectively. The samples foamed through CBAs produced stronger mechanical parts in both tensile and flexural modulus. Also, low-pressure foaming through CBA produced parts that had near-perfect surface finishes, matching that of conventional molding. High-pressure foaming through PBA showed an improved surface finish compared to low-pressure (through PBA) but was still inferior to that of the CBA foamed parts.
Machine Calibration Effect on the Optimization through Design of experiments (DOE) in Injection Mold
Quality issue is one of the most important concerns in injection molding. However, before executing mass production, how to retain good quality is one of the crucial factors in injection molding. To retain good quality, it is commonly using CAE to assist from original design to revision and to fabrication. However, even using CAE, it doesn’t guarantee the quality factors obtained from CAE can be applied to real experiments. Moreover, the design of experiment (DOE) method has been utilized into injection molding product development. Today, there are still some challenges when people using DOE in injection molding. In this study, we have designed one injection molding system to define quality factor based on a circle plate. Then, we have tried to perform a series virtual DOE testing for injection molding using CAE to optimize the process condition. Furthermore, we also performed real DOE experiment to verify the virtual DOE concept. Finally, we will discuss about the machine calibration effect on the accuracy of quality comparison. Results shows that before machine calibrated, both virtual CAE-DOE and real DOE optimization can provide better quality for injection parts. However, there is some difference between the virtual and real DOE results. To find out why the difference between the virtual and real DOE results happened, we have investigated the machine feature and tried to calibrate it. After machine calibrated, the difference between the virtual and real DOE results has been improved by 58%.
Machine Learning and Multi-Objective Optimization of Industrial Extrusion
A three-level multivariate control system is described that transforms a vector of machine inputs to a vector of virtual process states, and then these virtual process states to key performance objectives. The multivariate system is implemented on a 150 mm (6 inch) screw diameter producing approximately 500 kg/hr of polyvinyl chloride (PVC) film having a nominal width around 1 m (37 inch) and a nominal thickness of 0.38 mm (0.149 inch). Validation is performed with respect to modeling and optimization of three performance objectives including production rate, energy efficiency, and process capability. The results suggest significant gains with respect to the Pareto optimality (efficient frontier) of energy efficiency and process capability.
Mechanical Properties of Electrospun Fibers from Ozone-treated Lignin
Ligninis a viableprecursor alternative for electrospun carbon fiber. Purification of lignin typically involves chemicals. Ozone treatment is an environmentally-friendly approach to purify lignin. In this study, electrospinning of untreated and ozone-treated lignin was conducted with polyethylene oxide (PEO) as an aid-polymerto form submicron fibrous mats. Morphology and mechanical properties of the electrospun fibers were investigated. Electrospun ozone-treated lignin fibers showedspherical shapes attached to smooth fibers, characterized as beads-on-a-string (BOAS) morphology. It was found that longer duration of ozone treatment resulted in decreased average fiber diameter while increasing bead density, changing spindle-like beads into spherical beads. Ozone treatment did not have significant influence on the strain at failure of the electrospun lignin mats. Bead formation reduced the tensile strength and the elastic modulusof the electrospun fibers. Medium ozone consistency and short reaction duration were found to be the optimum conditions where highest tensile strength and elastic modulus were achieved.
Method for Determining Cooling Time in Injection Molding Using Infrared Thermography
Injection molders face confusion about the best way to determine cooling time. Many methods exist to estimate cooling time, but disagreement among results and fundamental flaws create error that leads to extra work, long cycle times, and a loss of profitability for molders. This paper proposes a new method for determining cooling time at the injection molding machine using infrared thermography and DMA data to relate part ejection temperature to dimensional stability. Experiments showed evidence that dimensional stability is linked to material modulus, which would allow molders to choose cooling times based on required dimensional stability by relating measured ejection temperatures to specific modulus values using DMA data.
Modeling of Heat Generation in Spin Welding
Spin welding is a common joining process for plastic parts with circular joints such as insulated cups and bowls, filter housings, and valves. In this process, heat is developed from surface friction as one part is revolved about the axis of the joint, resulting in a high linear speed. Finite element analysis (FEA) of the process can provide insight into potential mechanical deformation or failure under load that may compromise the weld, as well as aid in determining proper process parameters to achieve sufficient heating for a good weld. In this work, an approach to predict the weld temperature has been investigated and compared to measured results.
Modeling the Non-Isothermal Conveying Characteristics In Single-Screw Extrusion By Application of Network Analysis
This paper deals with the modeling of the conveying behavior of polymer melts in single-screw extruders based on a network-analysis approach. The polymer-melt rheology is strongly temperature-dependent and hence the temperature profile affects the pumping capability. In this work, we propose an approach to predicting the non-isothermal, coupled axial pressure and temperature profiles. We present the fundamental background of the implemented pumping and dissipation models and the network theory for modeling the axial pressure and temperature profiles. The simulation procedure for calculating the non-isothermal conveying characteristics is shown and a few exemplary simulation results are presented. The novel algorithm provides fundamental insights into the non-isothermal extrusion characteristics and enables screw design and process optimization in single-screw extrusion.
Morphology and Mechanical Performance of Pipe Grade HDPE Exposed to Chlorinated Water
Thin samples of a pipe-grade polyethylene with a bimodal molecular weight distribution were exposed to 5ppm 70C chlorinated water for up to 3000 hours. The samples were characterized by tensile tests, size-exclusion chromatography, infrared spectroscopy, and differential scanning calorimetry. Throughout exposure, the molecular weight data showed evidence of degradation: weight-average molecular weight was reduced, and a shift in the molecular weight distribution from a bimodal to a unimodal distribution (decreased dispersity). After 2250 hours of exposure, brittle behavior was observed, in which the average elongation at break was 12%. At this level of degradation, the weight-average molecular weight was 9 % of its undegraded value, and the crystallinity had increased from 70% to 85%. Average tensile strength was reduced from 31.8 to 16.6 MPa. The data imply that the presence of short-chain branching may inhibit chemicrystallization and subsequently delay the onset of brittle behavior.
Multi-layer Co-extruded Annular Structures Burst Pressure Performance
Recent developments in the area of multi-layer co-extrusion have led to the ability to produce annular structures with high numbers of very thin layers. The burst pressure of these pipe structures was investigated. It was observed that die head rotation can have significant impacts on the mechanical properties of these structures due to the elimination of weld lines as well as biaxially orientation effects in the annular structures. It was also observed that following the elimination of the weld lines, the burst strength increases, possibly due to the biaxial orientation effects at higher rotation speeds.
New Development in Adhesion Promotion Using Flame Plasma Surface Treatment - Tutorial
Adhesion promotion technologies have wide application in the numerous industries for a wide range of plastic parts, such as those made of PE, PP, PET, etc. One method used to modify the surface of these and other polymer products to promote adhesion of coatings and adhesives is flame plasma. This paper describes the theory behind natural gas, propane or LPG fired flame plasma surface treatment to promote adhesion of water based inks, coatings, adhesives, labels and other substrate laminates to polyolefin based substrates. Critical parameters in flame treatment are, flame chemistry, flame geometry, plasma output and distance of the burner to the part. The interrelationship between these variables, and how to control them for optimum surface treatment, will be discussed. The use of Schliren imaging technology, high speed photographs of the flame geometry, used to develop new burner designs, as well as advances in equipment technology will be presented. A completely new patented process design has been developed and successfully implemented providing significantly improved control of the flame chemistry, while at the same time simplifying the process control and mechanical hardware required. In addition, the new design improves the overall efficiency of the flame treating process Troubleshooting & maintenance of flame plasma surface treating systems will be discussed.
Novel Method of Compounding Cellulose Nanocrystal Suspensions into Polylactic Acid and Polyvinyl Acetate Blends
Cellulose nanocrystal (CNC) suspensions were compounded into blends of poly(lactic acid)(PLA) and poly(vinyl acetate)(PVAc) using a novel wet compounding approach in which drying and compounding werecarried out simultaneously. The resulting CNC/PLA composites were compared with those produced using a more traditional method of freeze-drying CNC suspensions followed bymelt-blending into PLA. CNCs in wet compounded composites appeared to be well-dispersed in the PLA/PVAc blends, and films extruded from these compounds exhibited high transparency compared with melt-blended composites. Gel permeation chromatography indicated that molecular weight degradation due to wet compounding was comparable to that from melt blending. The formulation, including surfactant modified CNCsand PVAc processing aids, played a significant role in the dispersion and properties of the nanocomposites. The elimination of a stand-alone drying stepfor cellulose nanomaterials can potentially overcome some of the challenges associatedwith producing thermoplastic cellulose nanocomposites and help advance commercialization of these materials.
Numerical Analysis of Polymer Micro-foaming Process in Extrusion Flow
In this paper, effects of microviscosity and wall slip were considered, and a mathematical model of isothermal extrusion micro-foaming process was adopted based on classical nucleation theory and cell model. A simulation scheme of the extrusion micro-foaming process was conducted combining with the cross-section/imaginary area method and the Runge-Kutta method. The simulation program of the extrusion micro-foaming process was realized on MATLAB. The effects of inlet pressure on evolution of cell morphology and cell size distribution during the extrusion micro-foaming process were analyzed by the numerical examples. The results indicate that the higher the inlet pressure, the higher the maximum nucleation rate, and the closer to the die outlet the nucleation spot, the shorter the growth distance of the bubble, which is more conducive to formatting smaller cell radius and higher cell density.
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