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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Floating/Swivel Top-Load Testing and Simulation - a Novel Approach for Evaluating Unit Load Stability at the Early Stage of Primary Package Development
A novel floating/swivel platen approach is proposed in this paper for primary package top-load evaluations. Different from the conventional fixed platen top-load practice, this approach, which frees the translational (floating) and rotational (swivel) degrees of the platens and designates them separately to the bottom and top platens, allows tests or simulations to predict the lateral instability of primary packages. The lateral instability of primary packages becomes increasingly crucial to the tray-based unit load stability with growing cost-saving efforts and design innovations from brand owners, design agencies and packaging suppliers. This study, through both lab testing and virtual computer simulation, has demonstrated that the proposed floating/swivel platen approach accurately captures the package top-load reduction induced by the package lateral instability, while the conventional fixed platen top- load practice dangerously over-predicts the package top-load by a factor of as high as 3.6, due to the suppression of the lateral instability by the fixed platens. Such an over-prediction could lead to unexpected damage to the primary packages and/or unit load collapse during storage and transportation. The proposed floating/swivel platen top-load approach is recommended for light- weighting and design innovation in the early package development stage.
Selective Localization of MWCNTS in Blends of Poly(Methyl Methacrylate) and Styrene-Acrylonitrile Copolymer
Multi-walled carbon nanotubes (MWCNTs) were introduced into poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile copolymer (SAN) blends by melt mixing in an asymmetric mixer. A composition of 70 wt% of PMMA and 30 wt% of SAN was mixed to make a co-continuous morphology. Transmission electron microscopy images of ultra-microtomed samples (70 nm in thickness) showed selective localization of MWCNTs inside the percolated SAN polymer. The occurrence of the double percolation phenomenon resulted in lower electrical percolation thresholds of PMMA/SAN/MWCNT blends prepared at high temperatures. Dielectric spectroscopy indicated a higher electrical permittivity of samples that were molded at 260°C. Due to the higher affinity of MWCNTs to SAN, there was a migration of MWCNTs into the SAN phase during the melt processing.
Cyclic Olefin Copolymer Foams Part 1: Solubility Measurement of CO2 in Cyclic Olefin Copolymer and Preliminary Foaming Study
Cyclic olefin copolymers (COCs) is a novel engineering plastic with excellent thermal and mechanical properties which make them viable alternative to polyolefins. In this study, the solubility of supercritical carbon dioxide (CO2) in COC (Topas 6017) was measured at temperature from 453.15 to 493.15 K and pressure up to 17 MPa by a modified pressure decay system which can be operated in high temperature environment. The volumetric expansion of polymer caused by the dissolved CO2 were calculated by using the Sanchez-Lacombe equation of state (SL EoS) and these volume data were used to correct the apparent solubility data. The results demonstrated that solubility of CO2 in COC increased with the elevated pressure and decreased with the elevated temperature. SL EoS can correlated the solubility within 6% average relative deviation by introducing a temperature dependent interaction parameter. Moreover the COC foams were prepared by using pressure quench process and some preliminary results were obtained.
Effects of Holding Pressure & Process Temperatures on the Mechanical Properties of Moulded Metallic Parts
Metal injection moulding is gaining more and more importance over the time and needs more research to be done to understand the sensitivity of process to different process parameters. The current paper makes an attempt to better understand the effects of holding pressure and process temperatures on the moulded metallic parts. Stainless steel 316L is used in the investigation to produce the specimen by metal injection moulding (MIM) and multiple analyses were carried out on samples produced with different combinations of holding pressure, mould temperature and melt temperature. Finally, the parts were characterized to investigate mechanical properties like density, ultimate tensile strength, shrinkage etc. The results are discussed in the paper. The main conclusion from this study is unlike plastic moulding, the tensile properties of MIM parts doesn’t vary based on the flow direction of the melt, and tensile properties are sensitive to holding pressure and process temperatures. In order to achieve higher tensile strength, higher holding pressure is required. It was also observed that the samples shrunk more in thickness than in the width and length.
Design of an Innovate and Recycle Float-Valve System by Using CAD/CAE/LCA Tools
Due to the growing worldwide interest in tasks such as environment preservation and recycling, a model of float-valve system for domestic water tanks has been proposed. It considers in its design, the use of an urban waste product such as PET bottles, as the floating device of the mentioned mechanism, having as main idea to contribute with environment care. If the new design is compared with known commercial models, it could be considered as innovative due the reutilization of plastics wastes. At the same time, the system functionality is preserved, and the final parts are easy to fabricate at low cost. Also, the estimation of the Life Cycle Assessment (LCA) for the system shows that the proposed design could be catalogued as environmental friendly.
Design of an Isolated Runners Mould by Using CAD/CAE Tools
The main objective of this work was to compare the advantages and disadvantages of using an isolated runner mould comparing with hot and cold runner moulds. It was used CAD and CAE software for the representation of the mould. The isolated and hot runner’s moulds showed advantages regarding volumetric and lineal shrinkages and sink marks of the injected part and there is not loss of material after each cycle by solidification of the sprue and runners when it is compared with the cold runners. The isolated runner mould is less expensive than a hot runner mould.
In Mold Coating of Thermoplastic Parts: Electrical Conductivity Versus Injection Pressure
In Mold Coating (IMC) has been applied to Sheet Molding Compound (SMC) as an environmentally friendly alternative to make the surface conductive; for subsequent electrostatic painting operations. Due to its successful application to exterior body panels made from compression molded SMC, the application of In Mold Coating for injection molded thermoplastic parts is being developed. In order to make the coating conductive, the filler used in IMC is carbon black (CB). However, the injection pressure needed to coat the part is significantly affected by the amount of CB in the coating material. Predicting injection pressures for IMC of thermoplastic parts is more critical than for IMC of SMC. To predict the coating pressures we need to measure the effect of CB on the IMC viscosity. In the present work, we studied the effect of CB on electrical conductivity and viscosity. The pressures needed for coating a typical IMC part with the required conductivity level are estimated.
Morphology and Thermal Behavior of Nylon-6/Clay Nanocomposites Synthesized by In-Situ Solution Polymerization of Caprolactam
A novel in-situ anionic polymerization method for preparation of nylon-6/clay nanocomposites in N- methylpyrollidone is explored. Anionic solution polymerization of caprolactam was performed in the presence of montmorillonite clay. The product was obtained as granules. The morphology of the nanocomposites was studied by using X-ray Diffraction (XRD) technique and Scanning Electron Microscopy (SEM). Differential scanning calorimeter (DSC), was used to study the composites transition temperatures and melting behavior. The presence of clay broadens the melting and crystallization peaks and shifts the glass transition temperature and melting point to higher temperature.
The Effects of Turbulent Flow on Cooling Effeciency in Injection Molding
Cooling plays an important role in injection molding process. A well designed cooling system can effectively shorten cycle time and improve product quality as well. Nowadays, three dimensional cooling analysis has been applied in injection molding simulation. With this function, a complex cooling system design can be validated with its efficiency prior to actual manufacturing. However, the current simulation tool is not perfect yet since it does not consider turbulent flow and pipe surface roughness effect. In the current study, a latest simulation tool was applied which can predict the turbulent flow effect on cooling. Two cooling systems (conventional and conformal) were designed and simulated. The results were compared to each other which are helpful at the design stage in an injection molding cooling system.
Sandwich Injection Molding - Core Breakthrough and Flow Imbalance Studies
We presented numerical simulations concerning two important defects encountered in the sandwich molding process: the core breakthrough in a thin-walled part and the flow imbalance in a multi-cavity mold. The part thickness largely determines how far the skin melt front advance before breakthrough happens. This limits the size of the part and the maximum core ratio. The skin and core advancement in the multi-cavity system is complex due to the temperature imbalance and pressure resistance variation encountered in the runner. An understanding of the melt flow mechanism through simulation is helpful for the part designer to fully utilize the benefits of the sandwich molding process.
Transformation of Measured Viscosity Data of Special Plastic Materials Into Moldflow Software
Special applications in plastic engineering require new different polymers. Therefore new polymers and additives are constantly being developed. A lot of these special polymers are not available in databases and cannot be used in simulation software. But it is becoming more and more important to know as much as possible about polymers in order to avoid problems in product development and the manufacturing process. So the polymers have to be tested. This paper shows a possibility of measuring points of flow curves and transforming them into a mathematic model to do molding simulation with the specific material afterwards.
Role of Simulation in Analyzing Root Cause Failure
Understanding root cause failure mechanisms for plastic packaging is becoming more important. This need has become critical due to new packaging materials, faster production speeds, lighter weight packages, creative designs and challenging product formulations. Often there is a need find and eliminate the cause for failure and come up with a more robust package. Replicating and analyzing failures via simulation can provide rapid feedback and optimal solutions in a shorter time frame than traditional methodologies. This paper looks at some of the common failure mechanisms and not so common analysis and detection procedures. Practical case study examples will be presented.
A Study of Rolling Resistance of Electrospun Polymer Fabrics
Rolling resistance contributes to 6-10% of the overall fuel consumption of vehicles. Little is understood on the relationship between rolling resistance and surface characteristics such as adhesion, surface asperities and topology. In this study, we evaluate the rolling resistance using a free oscillation of a pendulum. Different substrate materials such as asphalt, rubber, wood, high-density polyethylene (HDPE), nylon, polycaprolactone (PCL) and poly(vinylidene fluoride) (PVDF) were tested by a laboratory fabricated pendulum steel roller. The damping factor is examined using an envelope analysis technique based on Hilbert transform methodology. The rolling resistance is found to depend on viscoelastic properties, adhesion and surface characteristics. The damping factor is the highest for asphalt and the second highest for rubber. The damping factor of electrospun polymer fabrics lies somewhere in between those pertaining to asphalt and more rigid substrates such as steel and copper
Key figures for describing and comparing the energy consumption of injection molding processes
This paper deals with energy consumption data for a broad variety of injection molded parts. An analysis shows that key figures can be derived for comparison and reference purposes and allow the evaluation of the energy efficiency in a part dependent production process. The key figures comprise material properties and part geometries to build a focus relative to these particular part characteristics independent of category or application. This approach goes beyond the widely applied method of examining a machine specific energy consumption data. A significant potential of energy reduction for most analyzed injection molding processes is expected.
Microcellular injection molding of in-situ modified Poly(Ethylene Terephthalate) with supercritical nitrogen
The microcellular injection molding (commercially known as MuCell) of in-situ polymerization-modified PET (m-PET) was performed using supercritical nitrogen as the physical blowing agent. Based on design of experiment (DOE) matrices, the influence of operating conditions on mechanical properties of molded samples were studied systematically for two kinds of m-PETs, namely, n-m-PET and m-m-PET synthesized using pentaerythritol (PENTA) and pyromellitic dianhydride (PMDA) as modifying monomers, respectively. The optimal conditions for injection molding were obtained by analyzing the signal-to-noise (S/N) ratio of the tensile strength of the molded samples. The specific mechanical properties, especially the impact strength, of the microcellular samples under these conditions increased significantly. Scanning electron microscope (SEM) analyses showed a uniform cell structure in the molded specimens with an average cell size of around 35 ?m. The m-m-PET modified with PMDA generated a slightly finer cell structure and a higher cell density than the n-m-PET.
Equipment and Material Considerations for Microcellular Foaming
Microcellular foaming processes are now proven technologies and integral part of the “mainstream” in polymer conversion operations. The present paper is a joint effort between two companies (Dow and Mucell) to address key aspects necessary to achieve a more efficient use of materials and resources via physical foaming. The paper reviews in detail all aspects that influence performance, paying special attention to the synergies that arise between hardware and material selection. A comparison of performance between chemical and physical blowing is analyzed, highlighting the advantages of microcellular foaming.
High Temperature Aesthetic Grade Liquid Crystal Polymers for Consumer Applications: Not Just For Connectors Anymore
For many years the use of high flowing engineered resins, such as Liquid Crystal Polymer (LCP), have been used for very detailed and intricate parts in the electronics and connector industries where function and performance far outweigh any need for coloristic attributes. Today we find the uses of such resins extending out to more visible consumer products that need the performance and functionality of the LCP with the additional demand of excellent aesthetics. This paper looks to show where the coloring of LCP and the producing of aesthetically pleasing parts has brought LCP’s from behind the scenes to center stage for the consumer products industry.
Simulating the directionality of liquid crystalline polymers
In this paper a practical method of modeling directionality of crystals in liquid crystalline polymers (LCPs) is studied. The main components of this method represent the effects of shear on crystals, the effects of crystals on each other and the effects of movement of crystals with the flow. The implementation of this simulation is done by coding a user defined function (UDF) in ANSYS® FLUENT®. The results of the simulation are shown in two and three dimensions. The presented results show promising closeness to the physical phenomenon associated with the directionality of LCPs. The proposed method can be used as an estimation of the directionality of crystallines during the processing.
Crystallographic Analysis of Electrospun Poly(?-caprolactone) Nanofibers by 2-D Wide-angle X-ray Diffraction (2D WXRD)
The crystalline morphology of electrospun PCL nanofibers was studied. Random and aligned nanofibers were obtained by a conventional plate collector and a two-parallel-conductive-plate collector, respectively. Scanning electron microscopy (SEM) and 2D wide-angle X-ray diffraction (2D WXRD) were employed to characterize the nanofibers. The degree of crystallinity of aligned nanofibers was higher than that of randomly aligned nanofibers. The crystallites in the nanofibers were highly oriented along the nanofiber axis, as were the molecular chains. The estimated crystallite size in the nanofibers suggested that a single nanofiber was composed of dozens of nanofibrils and a nanofibril was further composed of crystallites along the nanofiber axis with an amorphous region of extended PCL molecular chains between neighboring crystallites.
Mechanical Properties of Interconnected Porous Elastomers Fabricated by a Microsphere-Templating Casting Process
The mechanical properties of interconnected porous polysiloxane elastomers under tension and compression were studied in this work. The porous elastomer was found to be highly deformable and had non-affined tensile deformation. The increase of pre-set strains and strain rates in cyclic tension and compression resulted in an increase of stresses at pre-set strains and hysteresis. The permanent sets after unloading process non-linearly decreased as the strain rates were lowered in cyclic compression while the strain rates seemed to have very limited influence over permanent sets in cyclic tensile testing.
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