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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Enhanced Structure CAE Solution with Molding Effect for Automotive Parts
An increasing number of automotive parts are made of engineering plastic for its low cost and superior material properties. The traditional structure analysis for automotive injection-molded part is to perform CAE analysis based on the assumption of one or several isotropic materials. However, the material characteristic of plastic part is extremely dependent on molding process. The process-induced properties, such as fiber-induced anisotropic mechanical properties, might not be favorable to the structural requirement of final products. Besides, the mesh requirement for different analysis purposes might not be the same, either. In this paper, we integrate the CAE analysis of structure and injection molding through data-linking and mesh mapping. This approach shows the effects of mutually dependent analyses have been successfully examined in automotive injection-molded parts.
Significance of Creep Rupture and Stress Relaxation Data in Product Design and Material Suitability Evaluation
Premature brittle failures of an injection-molded part made from 20% glass filled Noryl tempted review of product design and material suitability evaluation for the intended application. Fractographic analysis of fracture revealed cracks were present at knit-lines in the part and were due to creep rupture failure mechanism. A stress analysis using finite element analysis technique was performed on the product design to evaluate the stress distribution at the location of fracture. Creep-rupture and stress-relaxation characteristics of the Noryl material were obtained by testing injection-molded samples with a knit line in the center. The usefulness of creep-rupture and stress-relaxation data in product design analysis was demonstrated. The material suitability and part design was assessed with the use of long-term stress-rupture and stress-elaxation data.
Foaming of Nanoclay Reinforced PS/PMMA Polymer Blends
Nanoclay reinforced polymer blends exhibit high potential as a new material for CO2 foaming because they can provide higher CO2 solubility, lower gas diffusivity, and better mechanical properties than foams made of homopolymers. In this paper, a polystyrene (PS)/poly(methyl methacrylate) (PMMA)/nanoclay blend was selected to study the relationship among blend morphology, nanoparticle distribution, and foam structure. PMMA serves as the dispersed domain in PS. Blends with different morphology were obtained by changing the nanoclay content and the screw configuration, which were then foamed by using CO2 in a batch system. Effects of nanoclay content on the blendmorphology, rheological properties, and foam morphology were studied. It is found that the highest foam nucleation efficiency appears at the interface of PS/PMMA/nanoclay.
Analysis of Pressure-Driven Disk-Flow Rheometry
In the pressure-driven disk-flow (PDDF) rheometry, the liquid is pressurized in the center of a pair of parallel disks and flows outward in the radial direction. While an analytical solution to the viscosity can be readily derived for Newtonian liquids, corrections need to be made to determine the actual relation between shear stress and shear rate for non-Newtonian liquids. A data analysis procedure with corrections similar to the Rabinowitsch-Weissenberg correction in capillaryrheometry was developed for the PDDF rheometry, resulting in a relation that correlate wall shear stress with wall shear rate at the exit of the disk flow. Computer experiments with a known viscosity model of a non-Newtonian liquid were carried out using Fluent® to generate data points for the pressure-driven disk flow. The data analysis procedure for PDDF rheometry was implemented and was able to extract the shear-rate-dependent viscosity from the raw data.
Effect of Heat Sealing Temperature on the Fracture Aspects of OPP/CPP Seal.
Failure criteria of the heat sealed part of oriented polypropylene (OPP) and cast polypropylene (CPP) heat seals made by an impulse type heat-sealing machine were investigated. Circular notches and pre-cracks were introduced to direct failure to specific areas such as inside the seal, at the border or the unsealed part. The notched strength as a function of heat-sealing temperature revealed that the seals were stronger in the transverse direction (TD) as compared to the machine direction (MD). Tensile failure that occurred inside the heat seal is more sensitive to sealing temperature while that at the unsealed part is immune. The stress intensity factor (K1) is generally higher along TD. Within the seal, three distinct zones could be identified with increasing temperature. For failure at the unsealed area, the value of K1 was constant irrespective of sealing temperature along the MD while the trend along the TD is similar to that within the heat seal. The weakest part was identified as the immediate neighborhood outside the heat seal.
Distribution of a Minor Solid Constituent in a Transfer Molded E – Pad Leadframe Package
This study investigates the spatial distribution of a minor particulate constituent in a transfer molded exposed die paddle (e-pad) leadframe microcircuit package. Packages were polished at three depths parallel to its top surface. Levels 1 and 2 are above the die and leadframe while level 3 is just below the top surface of the die and leadframe. The distribution of area fraction and size of the particulate was analyzed for each level and with respect to the distance from the gate using micro-photographic image analysis. A non-uniform distribution of the particulate material for both particle size and location is evident, and its relations with gate, die and leadframe are interpreted. ANOVA tests were conducted to assess the statistical significance of the variations.
Combinatorial Compounding and High Throughput Screening
To develop compounds with specific properties and to take full advantage of today’s variety of additives more efficient material development processes are needed. A new method is combinatorial compounding. Based on a twin screw extruder and a following flat film extrusion line compounds are produced and tested with a high frequency. For this the process control has to be altered so that gravimetric feeders continuously change the amount of additives. The composition and parameters specific for the optimization problem at hand are monitored. This information together with Measures of Significance (MOS; parameters or combinations of parameters) is fed into a data base which spans the parameter space. Algorithms known from combinatorial material research help to find a predefined optimum. The optimal compound can than be further tested.In this contribution the equipment, the process and the data management are introduced.
Fibril Formation of Thermotropic Liquid Crystal Polymer and Polyester Blends by Controlling Viscosity Ratio
Polymer blends based on poly(ethylene 2,6-naphthalate) (PEN) and poly(ethylene terephthalate) (PET) reinforced with a thermotropic liquid crystal polymer (TLCP) were prepared by a melt blending process. The TLCP component acts as a nucleating agent in the TLCP/polyester blends, thereby enhancing the crystallization of the polyester matrix through heterogeneous nucleation. The lower value of the structural viscosity index for the TLCP/polyester blends was attributed to the formation of TLCP fibrillar structures with elongated fibrils in the polyester matrix, resulting in better spinnabiliy. The higher intrinsic viscosity of the polymer matrix, higher shear rate, and lower viscosity ratio may favor TLCP fibril formation in the polyester matrix.
Biaxially Oriented Polypropylene Pipes
Since many years, polypropylenes with low amounts of ethylene comonomers (PPR) are used for production of hot-water pipes in sanitary applications. In this contribution we report on a new route for obtaining “biaxially” oriented PPR pipes via a die-drawing process previously developed at Leeds University. This results in a significant improvement of long-term stability as well as hydrostatic pressure and impact resistance, compared to PPR pipes produced under standard extrusion conditions. This unique behavior originates from a non-uniform orientation distribution throughout the pipe cross section, which has been analyzed using X-ray microdiffraction.
Improving Dimensional Stability in PP without Sacrificing the Property Balance
The importance of dimensional stability for the automotive industry is evident from the fact that a car consists of a combination of metal, fiber reinforced composites and polymer blends. Metals have a coefficient of linear, thermal expansion (CLTE) in the order of 10-20 x 10-6 /K.The standard way to match typical requirements is the addition of fillers; this leads to an increase in weight and a different property balance concerning E-modulus and impact strength. In contrast to this we describe a new concept to combine low weight, good mechanical properties and dimensional stability. The basis of a changing dimensional stability lies in the surface morphology and is achieved by introducing a layered rubber-PP structure. This change in morphology reduces the expansion coefficients in the important length and width direction, which is accompanied by a slight increase of CLTE in the direction of the thickness. Our goal is, to achieve a material with a very good dimensional stability without loosing primary properties.
Long-Term Tensile and Compressive Behavior of Polymer Foams
Polymeric rigid foams are increasingly used for highly loaded mechanical applications, e.g. as core in foam sandwich constructions in aircraft or automotive parts. So far the mechanical behavior of rigid foams is not determined precisely. Therefore the core of sandwich constructions is not taken into consideration for the mechanical design. This leads to oversizing and extended material consumption. This paper presents experimental results of long-term tests and indicates a theory to take into account the difference of tensile and compressive behavior of foams. This theory is based on a strength hypothesis and can be implemented in commercial finite-element programs. The proposed method leads to an improved mechanical design and as a consequence a reduction of mass of construction parts.
Removing the Mystery from Rotomoulding: New Insights into the Physiochemical Processes Involved Leading to Improved Quality Control
This paper presents a first report from a longterm collaborative programme between Matrix Polymers Limited and the Manchester Metropolitan University. The purpose of the programme is to examine physiochemical mechanisms of the rotational moulding process using a variety of analytical techniques.The effect on the performance of polyethylene (PE) caused by variation of the rotomoulding cooking cycle is investigated using a combination of infrared spectroscopy and melt rheology. Analytical results are correlated with large scale performance characteristics, measured by established industrial assessment techniques such as low temperature impact strength, brittleness, part density development and yellowness index.
Notched Impact Strengths of Compact and Microcellular Polycarbonate
The notched impact strength of compact polycarbonate depends on the temperature, thickness (with a tough brittle transition at thickness increases), contribution of sharp notches (transition of the flat tension to the flat stretching condition) and processing parameters.Microcellular polycarbonate foams produced by injection molding process using physical blowing agent (MuCell) with or without gas counterpressure process, shows significantly higher notched impact strength then compact polycarbonate, if the compact polycarbonate is brittle under the same test parameters. When the compact polycarbonate breaks toughly, the notched impact strength of microcellular foams is always significantly lower. Therefore it is very important to pay attention to the test parameters by comparing the notched impact strength between compact and microcellular polycarbonate.
The Analysis of the Optimal Parameter Design of Led Light Guide Panel’s Part
In this paper, we will demonstrate the analysis of molding process of Light-Emitting Diode (LED) Light Guide Panel’s part. The purpose of this work is to investigate the influence of design parameters such as gate location, gate dimension, cooling channel layout etc. As the thickness of this part becomes thinner, the distortion of that happens more frequently. The focus of the Light Guide Panel is changed due to dimensional distortion of this part. It creates an optical problem. The comparisons of different gate designs and cooling channel layouts are discussed in order to find the optimal parameters. The study finds that the warpage of this product is influenced apparently by cooling process. The analysis finds out that the important design parameters which influence the melt-flow pattern most are gate location and dimension.
Molecular Dynamics Simulations of Mechanical Properties and Behavior of the Lamellar Structure in Semi-Crystalline Polymers
Computer simulations have been employed to investigate the properties and behavior of the lamellar region in semi-crystalline polymeric materials. For this, the molecular dynamics method was used in conjunction with the statistical segment model. Through computer simulations, the response of the macromolecular chains under an external load was characterized along time.These simulations provide pertinent information about structure-properties relationships, and will eventually lead to a better understanding of the underlying phenomena.
Computational Techniques for Benchmarking OCF Cell Structures and Textures
One of the main challenges faced by the one-component foam (OCF) industry is finding affordable (a) quantitative measuring methods for the cell structures and textures influencing the physical properties of the foams, as well as (b) standard testing procedures to do it.In this paper, a novel computer-assisted technique for characterizing and benchmarking cell structures of OCF systems is presented. This technique couples very simple and cost-effective image acquisition procedures with computer algorithms developed specifically for OCF foam texture and cell structure analysis.The ultimate target of the proposed technique and methodology is to establish a standard for benchmarking and characterization of OCF foam textures and cell structures.
Experimental Data and Constitutive Modeling of Elastomers
The mechanical behavior of elastomers is characterized by Mullins effect, rate- and temperature-dependence, and a non-linear stress-strain response. These experimental features are well recognized and important, and have been extensively studied for more than 50 years. The understanding of the micromechanisms controlling the macroscopic mechanical behavior is much more recent, and advanced modeling tools allowing for accurate predictions of arbitrary deformation histories have only started to become available during the last few years. In this project we have examined the current state of the art in finite element modeling of elastomers. The predictive capabilities of modern constitutive theories are exemplified by comparing model predictions with experimental data for filled chloroprene rubber.
The Effect of Pigmentation on Crystal Growth during Rotomoulding
This paper studies the effect of pigment concentration and pigmentation blending methods on the impact properties, crystallinity and morphology of rotationally moulded polyethylene parts. Hot stage microscopy, differential scanning calorimetry and dynamic mechanical thermal analysis techniques were used. It was observed that the pigmentation blending method used and level of pigmentation had only limited effect on the extent of crystallinity. The reduction in impact performance for turboblended pigmented samples was due to the relatively poor distributive and dispersive mixing of the pigment within the polymer matrix.
Determining the Accuracy of CAE on Deep Drawn Thermoformed Parts
For many years injection molding simulation software has been used to accurately predict plastic flow characteristics and troubleshoot part designs. Recently thermoforming simulation software has been developed as a tool for predicting material behavior during the thermoforming process. The limits and capabilities of Thermoforming Simulation will be evaluated by comparing simulation results from both a mainstream part design and a deep drawn part (linear draw ratio > 4:1) and comparing with actual results from thermoforming processes. Draw ratios which are greater than 4:1 exceed conventional part design guidelines. The results of this exercise show that the simulation’s calculations of the wall thickness for mainstream part designs are relatively accurate,
Analyze Rheology of Polymer Thin Film by Nano-Rheometrics Simulation
This study has built up a nano-rheometrics simulation system to investigate the viscoelastic properties of polymer thin film. Experimental studies and traditional continuum mechanics are difficult to describe some critical nano-effects. By taking advantages of molecular dynamics simulation and the definitions of continuum mechanics, we could effectively analyze viscoelastic properties (i.e. viscosity, stress, elastic and viscous moduli…) on different condition in nano-scale. This proposed system includes a polymeric fluid modeled with the shifted Lennard-Jones potential, while the polymer bond stretching/bending/torsion is modeled with Hook-like model. All simulation results are in a good qualitative agreement with similar experiment.
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