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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This paper discusses how melt flow indices and flow behavior data can be used to predict polymer flow in real industrial processes. The ability to simulate flow behavior can help us establish a robust process that has a large processing window and which accommodates a natural variation. The effect of shear rate on viscosity is of far greater significance. It is therefore important to find the Newtonian region of the curve and set the process parameters in this region for a specified mould thickness. This paper also aims at modifying the flow behavior of polypropylene blends using various lubricants and flow promoters both low molecular weight and polymeric flow promoters
Free quenching of three-layered slabs of PS-PC-PS and PC-PS-PC from various initial melt temperatures to below the glass transition temperature was carried out. The thermal residual stress and birefringence distributions along the thickness direction of the slabs were simulated and the birefringence was measured. Simulations were based on the linear viscoelastic and photoviscoelastic constitutive equations and the first-order rate equation for volume relaxation. The relaxation modulus and strain-optical coefficient functions of polymers as a function of time and temperature were used in the simulations. Comparisons indicated a reasonable agreement between the simulated and measured data.
To make polypropylene automotive components with reduced wall thickness, there rises the need to maintain equivalent load bearing capacity. The paper aims at establishing the basic mechanical property requirements which influence the design of automotive components with reduced wall thickness. A set of elastomer modified polypropylene resins with different levels of reinforcement is investigated with respect to their physico-mechanical properties such as yield strength, yield energy, stiffness, stiffness impact balance and impact strength together with impact energy.
This study investigates the effect of crystallinity and nanoclay content on the barrier properties of polyamides of similar polarity, one amorphous the other semicrystalline. The polyamide resins were compounded with commercial alkylammonium montmorillonite nanoclay to achieve volume percent inorganic contents of 0.125%, 0.25%, 0.5%, and 1%, as confirmed by thermogravimetric analysis (TGA). All formulations were then extruded through a 6 inch cast film die to yield transparent sheets which were then tested for oxygen and water vapor permeability, with the crystallinity of the semi-crystalline materials measured via differential scanning calorimetry (DSC).
Long glass fiber reinforced thermoplastics are widely used in industry because of their low cost and high performances. During the injection molding process, the glass fibers initial length is reduced by breakage and this phenomenon strongly affects some mechanical properties of the components, e.g. their impact strength. The aim of this study is to minimize the fibers breakage in a hot runner channel by optimizing its geometry. Geometrical control parameters were selected to model different geometries using a 3D modeler, and fluid dynamic numerical simulations were conducted using ANSYS Polyflow. An SQP optimization algorithm, implemented in a multi-objective optimization software, was used to determine the values of geometrical control parameters that minimize the fibers breakage.
Of the four pillars required for the successful development of a plastic part; material selection, part design, processing, and service environment, processing is often assumed to be the most controllable. Even when the service environment has been properly defined, the best design principles implemented, and the appropriate material selected, seemingly insignificant changes in processing can grossly and adversely affect an otherwise well developed product. This paper will explore case studies where the failure of the part can be traced directly back to improper processing and how shortcomings in processing ultimately predisposed them to premature failure.
The purpose of this work is to compare the mechanical properties of the different PP/ Filler composites. We considered the effect of treatment of the filler on the adhesion between the filler and the matrix .Modification of polypropylene (PP) with different coated and uncoated fillers is investigated in this paper. Six types of different fillers are used for preparation of filled PP composites. The composite samples were homogenized in a twin screw extruder. The compatibility of PP and fillers focused in this study and modified by using coupling agent. The obtained values of composites were correlated with mechanical properties.
The purpose of this work is to compare the mechanical properties of the different PP/ Filler composites. We considered the effect of treatment of the filler on the adhesion between the filler and the matrix .Modification of polypropylene (PP) with different coated and uncoated fillers is investigated in this paper. Six types of different fillers are used for preparation of filled PP composites. The composite samples were homogenized in a twin screw extruder. The compatibility of PP and fillers focused in this study and modified by using coupling agent.The obtained values of composites were correlated with mechanical properties.
Zn-Al Layered Double Hydroxides (LDHs) containing nitrate as the interlayer anion was prepared by coprecipitation. The resulting suspension was treated with deprotonated stearic acid (octadecanoic acid) to give an organo-modified hydrotalcite compound (Zn-Al LDHStearate).The prepared LDH-stearate was successfully delaminated in hexadecane resulting in a Zn-Al LDH stearate/hexadecane. In situ intercalative polymerization of styrene with the delaminated LDH (with different ratios) resulted in the formation of partially exfoliated polystyrene-based LDH-stearate/hexadecane nanocomposites (polymer/clay nanocomposites). The delaminated LDH nanosheets before and after introduction into the polystyrene matrix were confirmed by elemental analysis Atomic Absorption Spectroscopy (AAS) X-ray Diffraction Spectroscopy (XRD) and Thermogravimetric Analysis (TGA). X-ray diffraction confirmed exfoliation of the LDH through the disappearance of the basal (003) reflection.
Bio-derived thermosets were cured from inexpensive, low-toxicity precursors. Epoxidized linseed oil (ELO) and epoxidized soybean oil (ESO) were crosslinked with a range of crosslinking agents: branched polyethyleneimine (PEI) and triethylenetetramine (TETA). Curing conditions were optimized through solvent uptake and soluble fraction analysis. Properties may be varied from elastomeric to rigid. Rigid bioepoxies, while not as stiff as conventional materials, are expected to display better toughness and may be promising for coatings and as binders in engineered wood products.
Polycarbonates find applications in food industries due to their clarity and ductility. Sometimes failure of a polycarbonate part occurs. In food blender jars molded from polycarbonate, cracks were observed in the sealed joint only a few days after assembly. The root cause was investigated via microscopy, FTIR and GC-MS analyses. It was determined the cracks initiated and radially propagated from the bottom raised lip of the part. The root cause was a combination of a high stress in the lip region due to molding and design, and environmental chemical compounds, i.e., esters from a melt nut used in the assembly. The failure was typical environmental stress cracking (ESC) problem.
Flame retardance, low smoke generation and low smoke toxicity (often referred to as the FST properties) are among the critical requirements for polymeric materials used in building and construction as well as mass transit interior applications. Polyphenylene ether (PPE) is wellknown for its high char formation and low smoke toxicity when burned. Addition of a proprietary smoke suppressant 'LS-1' to a flame-retarded PPE blend results in low smoke density without significantly affecting smoke toxicity and flame-retardance, possibly owing to the formation of intumescent char. In addition to improved FST performance, various PPE compositions exhibit low specific gravity, wide colorability and good mechanical, thermal and electrical properties.
During polymer processing the solidification is accompanied by local and temporarily varying temperature and pressure distributions. The simultaneous occurrence of the molten and solid state leads to the development of inhomogeneous shrinkage and dimensional instability.With a novel processing approach (CIS), the solidification is achieved by uniform compression over the entire part volume, which leads to an even shrinkage.In this paper, the fundamentals for this process were investigated. It was found that the specific volume is dependent on the pathway of compression. As main impact factors the pressure, temperature and compression speed were detected. Finally, the compression heating of the melt was measured and a relation to the volume change was found.
Mesh partitioning technique is used to simulate bilayer coextrusion in a complex profile extrusion die. Mesh partitioning technique allows coextrusion simulation without changing the finite element mesh as the interface between the adjacent polymer layers is changed during a coextrusion simulation. Since the finite element mesh in the die remains fixed during the simulation, the mesh partitioning technique allows coextrusion simulation even in highly complicated profile dies. Effect of polymer viscosity on interface shape, velocity, pressure, shear rate, and residence time distribution in a profile coextrusion die is analyzed. It is found that polymer viscosity has significant effect on the interface shape, velocity, pressure, and shear rate, but only a minor effect on the residence time distribution in the die.
The presented research focuses on the fundamentals of the foaming process in rotational molding and control of final cellular structure. The experimental results of foaming experiments, performed under isothermal and non-isothermal conditions, indicate that the foaming process could be divided into three distinct phases: bubble nucleation, bubble growth and bubble coalescence. It was found that bubble growth and coalescence mechanisms are dynamically competing during the entire foaming process and the degree of uniformity and structure of the final foam are primarily determined by the nucleation stage.
Injection molded micro parts require accurate replication of micro-scale features. This replication is governed by complex mechanisms and its quality depend on the plastic material properties the geometry of the features and the process conditions The objective of this paper is to improve the replication of the micro-scale features by decreasing the polymer viscosity. The effects of melt viscosity and molding conditions on replication of microscopic features in injection molded parts were examined for a PA66 blended with a LCP additive. The replication was measured at different contents of LCP and at different process conditions.
Injection molded micro parts require accurate replication of micro-scale features. This replication is governed by complex mechanisms and its quality depend on the plastic material properties, the geometry of the features and the process conditions The objective of this paper is to improve the replication of the micro-scale features by decreasing the polymer viscosity. The effects of melt viscosity and molding conditions on replication of microscopic features in injection molded parts were examined for a PA66 blended with a LCP additive. The replication was measured at different contents of LCP and at different process conditions.
The localization of multiwalled carbon nanotubes (MWNT) in immiscible polymer blends was discussed based on the aspect ratio of the filler particles and the wetting coefficient. As a model system, MWNT were introduced into compatible blends of polycarbonate (PC) and poly-styrene-acrylonitrile (SAN) by melt mixing in a microcompounder either by pre-compounding small amounts into PC or SAN or by mixing all three components together. In agreement with the presented theoretical considerations, in all blends, regardless of the way of introducing the nanotubes, the MWNT were exclusively located within the polycarbonate phase, inspite of the almost equal surface energies of the two blend phases.
Morphology development of polypropylene /polyamide 6 (PP/PA6) blend in water-assisted injection molded (WAIM) curved pipe was investigated. The blend morphology development was interpreted with the aid of stress and temperature fields within the mold cavity under melt filling and high-pressure water penetration during WAIM process. The results showed that the morphology developed at the position near the water inlet is induced mainly by the melt filling, whereas the morphology at the position near the end of water channel is mainly ascribed to the high-pressure water-assisted filling. Then the water pressure and melt temperature were investigated in terms of their effects on the morphology development of dispersed PA6 phase. It was demonstrated that higher water pressure result in more obvious deformation of the dispersed phase at the position near the end of water channel.
Multilayer materials offer benefits in terms of new materials for packaging and barrier applications. The ability to maintain layer stability as the material flows into different die designs is important for fabrication of these materials. This work investigated different die designs for use in fabricating multilayer films. Three dimensional analyses of different types of manifold designs have been applied to optimize the die design of a coat hanger die. For the horizontal multilayer systems, an elongated tear drop manifold design with a relatively sharp angle provided the most uniform flow and layer distribution. With the vertical multilayer system, however, a gradual change in the manifold geometry enabled more uniform flow. The vertical layered systems also consistently exhibited curving of the layer interfaces. The horizontal layers were not affected by the presence of a secondary manifold, but in vertical layered systems, the secondary manifold produced non-uniformities in the layers and instabilities in the flow.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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