SPE Library

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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Conference Proceedings

Long-Term Tensile and Compressive Behavior of Polymer Foams

A. Kraatz, M. Moneke, V. Kolupaev, May 2005

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

NG Henwood, MA Roberts, A Quaratino, S Collins, P Sharifi, C Liauw, GC Lees, May 2005

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

Andrzej K. Bledzki, Hendrik Kirschling, Georg Steinbichler, Peter Egger, May 2005

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.

Monte Carlo Modelling of LDPE on a Molecular Level; Relating Molecular Structure to Polymer Properties

Peter Neuteboom, Sjoerd van der Hem, May 2005

Although LDPE is amongst the oldest polymers, it is also the polymer with one of the most complex molecular structures. Using a Monte Carlo method a model has been developed with which it is possible to calculate the detailed structure of each and every single molecule. The molecular characteristics have been related to analytical methods like GPC, NMR and DMS. Moreover the effects of the molecular structure on the polymer properties have been studied. The model has proven to be a valuable tool in product and process development.

The Analysis of the Optimal Parameter Design of Led Light Guide Panel’s Part

Yao-Tsung Lin, Chung-Chih Lin, Feng-Yang Xie, May 2005

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

Ricardo Simões, Witold Brostow, Gustavo R. Dias, Júlio C. Viana, António M. Cunha, May 2005

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.

The Role of Numerical Injection Molding Simulation in Predicting Mechanical Properties

Rolf Koster, May 2005

Research objective is to establish manufacturing-related design rules and procedures for engineering design of injection molded thermoplastics parts, and to investigate application of novel materials to support development of design for sustainability. Outputs of numerical injection molding simulations have been compared with tensile and tensile-impact test results for different geometry-material combinations. Combination with simulation results on thick-walled parts reported earlier has led to a systematic with predictive capability of simulation outputs for differences in mechanical performance.

Vibration Welding Non-Planar Surfaces

P.J. Bates, X.Y. Dai, C-Y. Wu, May 2005

This study examines the vibration welding of mating plates whose faying surface lies in two distinct planes. Plates containing both ‘horizontal’ and ‘angled’ surfaces were injection molded using a glass-fiber-reinforced nylon 6. These plates were then vibration welded to create a butt-welded assembly containing two non-parallel weldlines. The tensile weldline strengths were measured at different locations along the weld. Weld pressure, vibration direction with respect to the plate axis and the geometry of the ‘angled’ section were all observed to have significant effects on weld strength.

Computational Techniques for Benchmarking OCF Cell Structures and Textures

Ricardo Simões, Aster De Schrijver, May 2005

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

Jörgen S. Bergström, May 2005

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

M.P. McCourt, G.M. McNally, M.P. Kearns, D.C. McConnell, M. Martinez-Cobler, W.R. Murphy, May 2005

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.

Development and Characterization of Thermoplastic Biodegradable Nanocomposites

Lluís Cabedo, José L. Feijoo, José Ma. Lagarón, Juan J. Saura, Enrique Giménez, May 2005

Biodegradable blends of amorphous Poly(lactic acid) (PLA) and polycaprolactone (PCL) have been developed by melt blending. The morphology of these materials was characterized by means of WAXD and TEM, showing that silicate layers of the kaolinite (chemically modified kaolinite) were intercalated and evenly distributed within the biodegradable matrix. Mechanical, thermal and gas barrier properties of the different blends and nanocomposites were studied and the effect of clay addition on the above-mentioned properties was evaluated.

Determining the Accuracy of CAE on Deep Drawn Thermoformed Parts

Michael D. Harter, Jason M. DyJack, May 2005

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

Chi-Fu Dai, Rong-Yeu Chang, May 2005

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.

Application of Raman Spectroscopy and X-Ray Scattering for Inline Analysis of Polymer Orientation during Processing

T Gough, SE Barnes, HGM Edwards, PD Coates, May 2005

Orientation and crystallinity of polymer films, fibres and moulded products plays a crucial role in determining end product properties. Industrial processes such as melt drawing, blow moulding and injection moulding take advantage of the enhanced mechanical properties introduced into polymer products as a result of increased alignment of molecular chains [1].The overall aim of this research is to develop a methodology for real-time in-process assessment of processed induced orientation in blown film processing and in an injection moulding nozzle.This paper presents preliminary investigations into the application of polarised Raman spectroscopy and small angle x-ray scattering (SAXS) experiments for analysis of molecular oreitnation in solid state micro-injection moulded polyethylene samples as a function of injection velocity samples.

The Rotational Moulding Characteristics of Biodegradable Copolyesters

M.P Kearns, C. McLaughlin, M.P. McCourt, E.J Harkin-Jones, May 2005

Biodegradable copolyesters are processed primarily through extrusion and injection moulding. This paper presents preliminary investigations into the grinding and rotational moulding characteristics of commercially available biodegradable copolyester. Cryogenic grinding and subsequent rotational moulding experiments on the copolyester resin resulted in complete mouldings of uniform wall thickness being produced. It was observed that peak internal mould air temperatures of approximately 150 degC are required in order to produce acceptable mouldings.

Nonlinear Viscoelasticity of Glassy Polymers: Normal Force Behavior

Anny Flory, Gregory B. McKenna, May 2005

Single step torsional stress relaxation experiments are performed on glassy cylinders made of poly(methyl methacrylate) (PMMA) and poly(ethyl methacrylate) (PEMA) as a function of strain and temperature. In this type of experiment, it is required to apply not only a torque but also a compressive normal force to keep the length of the cylinder constant. The origin of the nonlinear effect of the normal force in glassy polymers is not well understood but there is evidence that it is related to the chemical structure of the polymer. In this work we test the hypothesis that the large normal force of PMMA is due to its prominent ?-relaxation. Results show that the ?-relaxation of the PMMA which is related to side chain motions, influences the normal force behavior. This is also confirmed by the fact that for specimens having weaker ?-relaxation, i.e. poly(ethyl methacrylate) (PEMA), the difference between the normal force and torque relaxation behaviors is less.

Chain Length Dependence of Heat Capacity

Dinghai Huang, Sindee L. Simon, Gregory B. McKenna, May 2005

The specific heat capacity was measured with stepscan DSC for linear alkanes, for several cyclic alkanes, for linear and cyclic polyethylenes, and for a linear and a cyclic polystyrene. For the linear alkanes, the specific heat capacity in the equilibrium liquid state decreases as chain length increases; above a carbon number N of 10 (decane) the specific heat asymptotes to a constant value. For the cyclic alkanes, the heat capacity in the equilibrium liquid state is lower than that of the corresponding linear chains and increases with increasing chain length. At high enough molecular weights, the heat capacities of cyclic and linear compounds are expected to be equal, and this is found to be the case for the polyethylenes and polystyrenes studied.

Back-Molding of High-Gloss Films with Long-Fiber Reinforced Thermoplastics Large LFT Parts for Automotive Exterior Body Panel Application

O. Geiger, F. Henning, P. Eyerer, R. Brüssel, H. Ernst, W. Seib, S. Funkhauser, X. Hopfenspirger, May 2005

This present paper focuses on the process technology for manufacturing of large LFT parts for automotive exterior body panel applications by a back-molding technology of high- gloss films with LFT material based on styrene copolymers. The material development as well as the suitable adaptation of the LFT-D-ILC direct process is presented.Fraunhofer Institute for Chemical Technology (ICT) and partners have combined the LFT direct process technology with high gloss polymer films for exterior body panels, e.g. roof modules, door panels etc. The process technology is developed to a prototype status and hence a promising starting point for the manufacturing of large automotive exterior parts.

Nonlinear Viscoelastic Response of Polymer Melts: Hole Burning Spectroscopy

Xiangfu Shi, Gregory B. McKenna, May 2005

A mechanical spectroscopy hole burning (MSHB) scheme was constructed and the experiments were carried out on a low density polyethylene and a polystyrene solution in their terminal relaxation regimes. Mechanical spectral holes were burned analogous to observations from non-resonant dielectric spectral hole burning (DSHB). A continuum nonlinear viscoelastic constitutive model BKZ without invoking an explicit heterogeneous dynamics for the relaxation response can not capture the subtle holes observed in the experiments. This strongly implies the MSHB is a novel tool to study the dynamic heterogeneity in polymeric systems.