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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IS RTC THE LONG AWAITED PANACEA FOR INJECTION MOLDED PARTS?
In contrast to conventional injection molding, where the tool is cooled continuously, in Rapid Temperature Cycle Molding RTC™ the cavity surface is rapidly heated to around the glass transition or melting temperature of the plastic before melt injection. Benefits are summarized and quantitative results cited. These include: achieving fine surface finish and gloss, including for foamed and filled materials (Ra for foamed ABS reduces from 1500 to 30 nm and for LGF PP from 1600 to 150nm); elimination of visible weld line defects; improved transcription of surface micro- features; improved optical properties in clear moldings; reduction of injection pressure, allowing longer flow paths, lower machine tonnage, part thickness reduction with reduced cooling time, and reduced molded-in stress. Implementation of the two leading technologies for implementation of RTC™ are described: heating with steam; or use of external induction heating to rapidly raise the cavity surface temperature, both followed by water cooling. A case study for RTC™ is described, leading to series production of a metalized part for a German automotive OEM. Performance requirements dictated a thin metalized layer (0.2 -0.3?m), formed by physical vapor deposition. This being insufficient to hide weld line defects, and use of a thick primer layer (15 ?m) being unacceptable, raising the cavity surface by RTC™ induction heating was trialed and shown to be entirely successful in removing defects.
NEW DEVELOPMENTS IN FIRE RETARDANCY OF STYRENIC COPOLYMERS
Styrenic copolymers such as HIPS and ABS are taking a very important place in the electronic industry. As they burn easily, brominated flame retardants are used to improve their flame retardancy. This paper presents developments with tris(tribromophenyl) triazine showing its contribution to environment protection by lowering carbon foot print and by its non-blooming behavior. Tris(tribromophenyl) triazine flame retardant systems enable reduction or even elimination of antimony trioxide while maintaining a good level of properties.
ADVANCED COMPUTATIONAL TECHNIQUE FOR THE OPTIMIZATION OF SPIRAL MANDREL DIES
The extrusion-die is one of the main components in an extrusion line and influences the product quality as well as the whole process efficiency. The requirements on extrusion-dies are versatile and the design of extrusion-dies is a very complex process with the necessity for huge know-how. Therefore the whole design process of a spiral-mandrel-die (SMD) based on a parametric 3D-CAD-mastermodel has been coupled with a 3D-CFD-simulation and implemented into a fully automized process. The flexibility of the extrusion dies to reach a high product quality for different materials is one of six criteria for the automatic interpretation of the extrusion die quality.
FIBER LENGTH REDUCTION AND HOMOGENEITY OF INJECTION-MOLDED SHORT FIBER REINFORCED THERMOPLASTICS WITH SPECIAL REGARD TO THE INFLUENCE OF A STATIC MIXING NOZZLE
During the injection molding of fiber reinforced materials, the molded component's mechanical properties strongly depend on the resulting distribution of the fiber lengths in the component. Owing to various influencing factors in the injection molding process, the fiber lengths are shortened in comparison to the pellet's initial fiber lengths. Within the scope of the experimental investigations, the different influencing factors, especially the influence of the mixing nozzle, were identified and analyzed.
HIGH PRESCISION MICRO MOLDING INJECTION OF 2 COMPONENT LIQUID SILICONE
For the production of micro parts with very small shot weights, the micro-injection molding has become an established technology with a variety of concepts. Currently, a trend can be seen that the special procedures will be introduced in the micro-injection molding. The micro injection molding machine , formicaPlast, is prepared for these usual procedures. It does not matter if the micro parts have to be produced as an one component or a two component part, the technology os available to serve the indsutry needs for a high automised micro injection molding process.Furthermore, the powder injection molding and the silicone injection molding is already possible to turn a standard formicaPlast machine. The liquid silicone injection molding requires certain changes to the machine, but these are very limited. The following article presents the possibilities of liquid silicone injection molding production for various tasks and batch sizes of the formicaPlast.
NON-LINEAR STRESS-STRAIN AND DUCTILITY MODELING OF A POLYMER COMPOSITE WITH FILLERS
Traditional composite based micro-mechanics can be used to predict linear elastic properties for thermoset matrix system accounting for the effects of filler type, concentration and size. The focus of this paper is to understand the effect of rigid fillers on the constitutive properties of a fully cured epoxy thermoset polymer covering non- linear regime including failure. A methodology, using a combination of DIGIMAT and ABAQUS based FE-modeling was developed to fully capture the stress-strain behavior using a Leonov -based material model.
ANALYSIS OF NANOSTRUCTURES SYNTHESIZED BY USING RESIDUAL SOLIDS FROM WASTED TIRES AS CARBON SOURCE
This paper focuses on the synthesis and morphological characterization of carbon nanostructures obtained from the decomposition of residual solids waste tire (RSWT) in quartz tubes under reduced pressure (1.33 Pa) at 900 °C for 15 minutes. The synthesis exhibits, principally the formation of two phases: the first a fragmented solid black powder constituted by multi-walled carbon nanotubes (MWCNTs), onion-type fullerenes and spheres, the second a very bright metallic dark film. Analysis by microscopy (SEM and TEM) showed that the MWCNTs had an average diameter of approximately 25 nm and a length greater than 100 nm while the diameter of onion-type fullerenes was found to be 8 nm. The nanospheres showed different diameters, from 500 nm to 1.5 ?m and some have a metallic core surrounded by layers of carbon. The infrared spectra of the nanotubes exhibited absorption bands at 1631 and 1458 cm-1, corresponding to the double C=C and C-C bonds, and signals at 3438 and 1080 cm-1 that are related to the OH and C-O groups from oxidized graphite as it was identified in the dark film.
EFFECT OF NANOTUBE CHARACTERISTICS ON MULTIWALLED CARBON NANOTUBE/POLYAMIDE 6,6 COMPOSITES PREPARED BY MELT-MIXING
Differential scanning calorimetry (DSC), x-ray diffraction, dynamic mechanical analysis (DMA) and electrical conductivity measurements were performed on multiwalled carbon nanotube/polyamide 6,6 composites with three different types of well-characterized tubes manufactured using fixed-bed catalytic processes. The tubes differed in diameter, number of walls and surface chemistry. There were not large differences in behavior with respect to modulus, maximum electrical conductivity and percolation threshold.
OVERVIEW OF THE TESTING PROGRAM ON FIBERS USED IN BALLISTIC APPLICATIONS
The goal of this paper and presentation is to give an overview of the research effort to date being conducted at the National Institute of Standards and Technology on polymeric fibers used in soft body armor (SBA) and a discussion of future directions. The overview covers chemical and mechanical fiber testing, microscopy, and x-ray scattering as means to understand potential mechanisms of degradation in these materials. Tensile testing results at quasi-static and at high strain rates that are comparable to strain rates experienced during ballistic events are also presented.
CRYSTALLIZATION BEHAVIOUR OF POST-INDUSTRIAL WASTE NYLON COMPOSITES
This study examined the crystallization behaviour of polyamide 6 from post-industrial carpet waste (PIW6-GF) and virgin polyamide 6 (PA6-GF) - both reinforced with 30 wt% glass fibers. Neutron activation analysis was used to detect the presence of contaminants – principally TiO2, a common pigment in carpet fibers. Once the Ti content in the glass fibers was accounted for, the TiO2 contents in the resin fraction of PIW6-GF and PA6-GF were estimated to be 0.14% and 0% respectively. Differential scanning calorimetery (DSC) was performed to assess the overall level of crystallinity and rate of crystallization. Experiments showed that, regardless of the cooling rate, PIW6-GF started to crystallize sooner and at higher crystallization temperatures than PA6-GF. This was attributed to the presence of TiO2 acting as a nucleating agent. Towards the end of the crystallization process, the rate of crystallization for PIW6-GF was observed to slow down relative to PA6-GF. At the highest cooling rates attainable in the DSC (200 °C/min), PA6-GF completed crystallization before that of the PIW6-GF compound. This reduction in crystallization rate is again attributed to the nano-scale TiO2 that could be interfering with the later stages of the crystallization process. The total crystallinity of moulded parts was observed to be greater for PA6-GF than PIW6- GF. Dynamic mechanical thermal analysis (DMTA) was performed on both materials one minute after ejection from a 30°C injection mould. This allowed the capture of rigidity data during the cooling of the specimen at a constant temperature of 25°C. PIW6-GF parts exhibited significantly lower complex moduli during the 30 minutes after moulding. Interestingly, modulus values at 25°C of both materials measured one week after the moulding were equal. The slightly lower crystallinity and the slower rate of crystallization are the suspected causes of this stiffness difference.
MODELLING OF HYGROSCOPIC STRESSES DUE TO NON-UNIFORM LIQUID DISTRIBUTION IN HOMOGENEOUS BIOPLASTICS
In this article, numerical modeling is used to simulate the distribution of liquid diffusion in bioplastic material and to determine the hygroscopic stress. The material used is homogeneous PLA based plastic exposed to aggressive automotive liquid. An analytical one-dimensional liquid diffusion solution is also presented to consider liquid concentration distribution, which shows a remarkable agreement with numerical simulation results. The results display non-mechanical stress distribution inside the homogenous material due to non-uniform liquid concentration profile.
OPTIMIZATION OF TEMPLATE PARAMETERS IN TEMPLATE-DIRECTED ELECTROSPINNING OF NANOFIBERS
Electrospinning is a simple and versatile technique to produce fibers. This is accomplished by using an electrostatically driven polymer jet, which thins as it whips towards a grounded target. The micronsized fibers produced from electrospinning are typically collected in the form of a random mat. The size and disordered structure greatly limit their application for areas that require well aligned, highly ordered arrangements such as tissue growth, protective clothing, highly effective thermal insulation and filters for fine particles and reinforcing fillers. Process parameters were studied as a function of percent aligned fibers while microscopy was used to characterize fiber orientation.
INTEGRATION OF INJECTION MOLDING AND STRUCTURE SIMULATION FOR PART LIFECYCLE AND MOLD DEFORMATION ANALYSES
Nowadays, with the increasing variety, complexity, and dimensional accuracy required for plastic products, CAE tools have been widely used in solving product design and manufacturing issues. However, lacking the consideration of process-induced effects on material properties in analysis, there is a significant deviation between the structural analysis results and the real product deformation. Besides, during the injection molding process performed for the production, it is essential to understand how the high pressure and high temperature plastic melt affects the mold surface for further investigation of the life cycle of metal mold. In this paper, we have proposed the simulation technology using Moldex3D-FEA interface to connect injection molding simulation (Moldex3D) and structural analysis (ANSYS). Using this technology, we can predict the injection molding product life cycle to cover injection molding process-induced variation on the part. At the same time, we also can evaluate how the process-induced effects will influence the mold metal life cycle. The results are very important for people to make the comprehensive consideration for full system lifecycle management.
HIGH TEMPERATURE INTUMESCENT MATERIAL
Most commercial intumescent materials consist of hydrated ceramic compounds in a polymer matrix that expand due to water vaporization when heated above 100°C. There are many applications that could benefit from intumescent, fire suppressant/protection materials where the system operating temperatures exceed 100 °C (e.g., aircraft applications, power generation facilities, chemical and materials processing facilities, etc.). To meet this need, a high-temperature intumescent material was developed that will only intumesce when local temperatures exceed 200°C. Once the initiation temperature is reached, the high-temperature intumescent material rapidly expands to approximately 10 times its original thickness, creating a physical barrier that is robust enough to block the spread of fire.
PEEL ABILITY AND MORPHOLOGY OF EASY-PEEL FILMS
Heat sealed plastic bags are widely used in food packages, vacuum-seal, and so on. It is very important to understand about heat sealing properties of these packages to confirm the reliability for using with their products. This research studied the heat sealed properties and peelability of heat sealed poly(ethylene terephthalate) (PET) and oriented polypropylene (OPP) films with low- temperature seal layer (adhesion layer). The peel strength and fracture surface of heat sealed PET-based films and OPP-based films were investigated by using peel testing and SEM. The sensitivity for peelable of heat sealed package was investigated by brain wave measurement.
INVESTIGATION OF CLAY MORPHOLOGY IN HIGH CONCENTRATION POLYPROPYLENE-CLAY NANOCOMPOSITES USING THE SUPERCRITICAL CO2 AIDED MELT BLENDING METHOD
Supercritical carbon dioxide was used with melt blending to form nanocomposites of polypropylene-organoclay. The collapse of the clays is investigated to further understand the processing limitations at high clay content. TEM and WAXD are provided to investigate these effects. It was found that shear forces result in collapse of the exfoliated structure in the composite. However, if the melt is not subject to enough processing, dispersion suffers. An intermediate solution must be determined.
MECHANICAL AND ELECTRICAL PROPERTIES OF MULTI-WALLED CARBON NANOTUBES/SYNDIOTACTIC POLYSTYRENE COMPOSITE AEROGELS
Multi-walled carbon nanotubes (MWCNTs) were employed to improve the mechanical properties and electrical conductivity of syndiotactic polystyrene (sPS) aerogels by exploiting MWCNTs connectivity within the sPS network. The MWCNTs/sPS composite gels were prepared using thermo-reversible gelation process, whereby a hot solution of sPS and a dispersion of Kentera- modified MWNCTs were mixed and cooled at room temperature. Subsequently, MWCNTs/sPS aerogels were obtained by drying the gels under supercritical condition. The morphology of MWCNTs/sPS aerogels was investigated by scanning electron microscopy. The effect of MWCNTs on mechanical and electrical properties of the aerogels was studied. It was seen that the morphology of the aerogels remained almost unaltered with the introduction of MWCNTs. The compressive modulus of the composite aerogels increased compared to the native aerogels. The electrical conductivity enhanced significantly in the presence of a low volume percentage of MWCNTs. In addition, the electrical conductivity increased with compression.
PREDICTION OF ORIENTATION DISTRIBUTION FOR LONG FIBER REINFORCED THERMOPLASTICS IN CENTER-GATED DISK FLOW
Long fiber-reinforced thermoplastic (FRT) composites widespread use in automotive industrial fabrication is more of a requirement than short FRTs. Mechanical properties of FRT products are dominated upon fiber orientation within the part. Recently, we proposed a new mathematic orientation model for two considerations of the interaction and diffusion between the fibers and the fluid [U.S. Patent Pending in USPTO with Application No. 13/168,211 (2011)], namely, iARD- RPR (Improved Anisotropic Rotary Diffusion Model combined with Retarding Principal Rate Model). Following the well- known Jeffery Hydrodynamic Model, this iARD-RPR Model can well determine the evolution of orientation, suitably for long FRTs. In this study, we employed these models to simulate numerically that the long FRT fluid with polypropylene matrix flows through a center gated disk. As a result, predictions of shell-core-structure orientation distribution, through the thickness measured at three regions of the near-entry, the lubrication, and the near-end-of-filling along the radial direction of the disk, were in good agreement with experimental observations.
SURFACE ENERGY EFFECTS OF PC/SAN/MWCNT BLENDS WITH THE ADDITION OF A REACTIVE COMPONENT
Blending immiscible polymers with the addition of Nano- additives is a very suitable method for tailoring the properties of materials. Carbon nanotubes (CNT’s) have shown in recent years to be versatile filler influencing several properties favorably. One property of concern is electrical conductivity of multi-walled CNT’s (MWCNT’s) which can be transferred into insulating matrices by filler percolation. These materials will strongly influence modern electronics, energy delivery, and anywhere composite materials are used presently. Drop Shape Analysis using a variety of test liquids to gather mean contact angle measurements is combined with Owens-Wendt theory of surface energy determining values for each sample. Atomic Force microscopy permitted examination of localization properties of the MWCNT’s with and without reactive component directly impacting thermal conduction and ductility.
NOUVEL NON-LINEAR RHEOLOGICAL PARAMETERS FOR POLYOLEFIN QUALITY CONTROL
The continuous demand of high performance materials with key properties requires the optimization of polymerization and post-reactor treatment processes. A multiscale characterization approach including techniques such as rheology, fractionation and NMR has proven to be essential to understand the links between polymerization conditions, molecular structural properties and end performance. Rheology is a preferred candidate for analytical characterization, since its use provides combined knowledge on molecular characteristics and processability. A key parameter for the performance of materials during processing is the so-called LCB. Rheology, in particular methods exploring the longest relaxation mechanisms, is known to provide a significant insight into the type and amount of longer chains incorporated during polymerization. Most of the existing rheological parameters used by Industry and Academia, to correlate molecular structure and processability, are based on techniques that are often time consuming and which, for most of the cases, are only applicable to a given class of materials. The increasing need to reduce “time to market” requires the development of more sophisticated and efficient characterization tools. The combination of different non-linear viscoelastic methods presented within this work will provide further insight into the links between molecular structural properties and polymerization conditions. The use of the Large Amplitude Oscillatory Shear (LAOS) together with uniaxial extensional flow measurements can bring new understanding on the nature of the non-linear viscoelastic response of LCB materials and its correlation with molecular characteristics.
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