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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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.
Application of Raman Spectroscopy and X-Ray Scattering for Inline Analysis of Polymer Orientation during Processing
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 .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.
Nonlinear Viscoelasticity of Glassy Polymers: Normal Force Behavior
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
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
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
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.
No Friction – Less Droplets
The packaging sector is one of the most important area in the plastics industry. More and more plastic films are being coated to gain decorative, protective, technical or functional properties. The coating can be applied with the aid of wet coating procedures. These include the class of rotor atomisers which function following the basic principle of fluid distribution. The rotor technique is now increasingly gaining in importance in the area of film coating. This technique can be used to apply very uniform, streak-free coatings in a continuously variable and inductive manner on moving webs. To carry out specific series of test, this new rotor system was integrated in a flat film line. The 5 major plastics - PVC, PET, PP, PS, PE – were selected and each was coated with slip agent, demister and anti-static agent. The evaluation makes clear that the film coating with the rotor atomizer is problem-free possible and the intended effect is provable immediately.
Interfacial Modification in Polyolefin Blends
Blending of thermoplastic polymers is of great commercial interest since the resultant material combines the properties of the different polymeric phases. The mechanical properties of these multiphasic blends are to a large extent determined by the morphology, i.e., the size, shape and distribution, of the components. One of the key factors for controlling morphology is modifying the adhesion between the phases since the interface represents a weakness across which stress may be poorly transmitted. Graft or block copolymers which locate preferentially at the interface, referred to as compatibilizers, are used to modify the blend morphology. In this work, we have evaluated a new type of interphasic polymer, formed in a two-stage process which results in a segmented compatibilizer with a linear molecular structure for each segment and narrow molecular weight and composition distributions. Improvements in the mechanical properties of blends, as well as changes in the morphology, are presented.
Flame Retardant Polypropylene
To improve the fire retardant properties of polypropylene (PP), it was compounded with aluminum hydroxide (ATH) using two different compounding lines, a twin screw extruder and a co-kneader. Flame retardant, rheological and mechanical tests were performed. The effects of processing machines and process parameters on the properties of the compounds were investigated. The influence of the properties of filler and matrix material was also examined.To minimize the content of additives without loss of the flame retardant properties, modified layered silicates (Nanofil, Suedchemie) were dispersed within PP/ATH compounds and their influence on the processing and compound properties was studied.The present investigation demonstrates the possibility to use a polypropylene as matrix material for halogen free cable compounds.
Thermoplastic Elastomer Nanocomposites Based on Dynamically Vulcanized PP/EPDM: Microstructure, Mechanical and Viscoelastic Properties
Thermoplastic elastomer nanocomposites based on dynamically vulcanized PP/EPDM with three different viscosity ratio and nanoclay content have been prepared by a melt compounding process. Based on the results of X-ray diffraction measurements, dynamic mechanical testing and thermal characterization, the microstructure of the prepared nanocomposite was found to be sensitive to the viscosity ratio of PP/EPDM and the nanoclay content. Xray diffraction and dynamic mechanical studies also suggested that nanoclays were exfoliated into the polypropylene and EPDM. Tensile modulus of the nanocomposite samples increased from 20 to 90% depending on nanoclay content and the viscosity ratio of PP/EPDM. Tension set of the nanocomposite samples also decreased in comparison with unfilled samples. Moreover, the presence of the nanoclay significantly increased the onset temperature of thermal degradation in the nanocomposite samples.
Optimization of the Properties of Polymethylmethacrylate Nanocomposites for Optical Applications
Transparent plastics like polymethylmethacrylate are widely used for optical components. Some disadvantages of plastic components like low hardness and abrasion resistance may be optimized through the modification with nanomaterials. The application of nanoparticles in polymers can also increase its refractive index and thereby broaden the fields of application of optical components.Polymethylmethacrylate nanocomposites with different nanomaterials were prepared by melt extrusion. The distribution of nanoparticles in the polymer matrix and optical properties of nanocomposites were optimized by means of modifying the surface of the nanoparticles and by varying the process parameters. The influence of the particle type and content on the mechanical and rheological properties was studied.
Next Generation of Soft TPUs
The demands made on elastomeric plastics – particularly those destined for applications where tactile properties are key – are growing ever more rigorous. Many such applications make use of thermoplastic polyurethanes (TPUs), drawing on their excellent properties of abrasion resistance, flexibility, chemical resistance and freedom from plasticizers. To gain the softness desired by the marketplace, TPUs are softened by the addition of plasticizers or compounded with other softer materials. Unfortunately these practices usually come at a cost of reduced mechanical or physical properties or raise potential environmental issues. Bayer MaterialScience has recently developed a new series of softer, processing friendly TPUs that are free of plasticizers and are not compounded with any other materials. The basis of these materials is explained below, illustrated using practical examples.
Mono- and Multi-Layer Tubing Incorporating a Silver Based Antimicrobial
The occurrence of device related infection is a common and problematic issue in the medical healthcare industry. This paper examines the effect of antimicrobial content on the rheological, mechanical and bactericidal properties of a range of mono- and multi – layer medical tubing products. The incorporation of antimicrobial masterbatch was shown to have negligible effect on rheological and processing properties of the materials tested. Mechanical properties were altered to some extent, but more importantly the antimicrobial efficacy of all the tubing samples was shown to be acceptable.
Hydrolytically Resistant Polyester
Polyesters are widely used in the automotive industry due to good molding and mechanical properties. However, unmodified polyester including PBT and PET, sometimes show failure in extreme long-term heat aging and humidity aging per USCAR III and USCAR IV tests. A new polyester technology was developed to improve both heat resistance as well as humidity resistance of impact modified polyesters. In addition, design of experiment (DOE) approach has been used to identify key factors to control mechanical properties and viscosity. This new technology has been successfully validated in automotive applications.
A New and Flexible Process for Thermoplastic Foams
Foam injection molding is a special injection molding process and offers many advantages to the processor. Enhanced part properties as well as decisive improvements in the production process are possible. When it comes to processing of physical blowing agents, different concepts are commercially available. These concepts differ mainly in the necessary effort by means of machine technology. The recently introduced Optifoam system is characterized by flexibility and the capability of retrofitting existing machines. It is based on an earlier development by the IKV Aachen. In this paper, the requirements on a foaming process with physical blowing agents are discussed. The process as well as latest research in this area is presented.
Thermogravimetric Analysis of Water Associated with Cellulose Fibers
A new classification of water in a fiber-water system, termed “hard-to-remove (HR) water”, was defined from an isothermal TGA experiment. This HR water was found to include some free water (trapped water) as well as bound water (freezing and non-freezing water). Specific experimental conditions have been defined for an appropriate measurement of the HR water content. The HR water content was correlated with important characteristics of cellulose-based fibers including water retention value and freeness. This test can be performed on extremely small samples as a convenient, insightful characterization technique for cellulose-based fibers.
Experiments in Impulse Welding a Thin Film Lid for Sealing Micro-Channels in Microfluidic Applications
The rapid increase in demand for polymer based MEMS has led to the development of various techniques for joining micro-devices. This paper describes experiments in impulse welding of thin polycarbonate films on a carbon filled polycarbonate substrate similar to the sealing of micro-channels on a microfluidic device. Pressure burst testing was carried out in order to measure the weld strength. The effects of power and heating time on weld width and weld strength were studied. The weld width was found to increase with power and welding time. Weld strength was found to increase with power and time until a point beyond which the strength dropped due to possible degradation. The temperature history on the film and the substrate surfaces was measured using thermocouples. The heating during impulse sealing was then modeled using a two dimensional transient finite element model. Fracture surface analysis revealed that weaker welds had a visually similar fractography irrespective of the welding conditions or thickness of nichrome wire used. Similar observations were made for the strong welds. To evaluate the effects of stress concentrations within the weld during the burst test, experimental and mathematical analysis were conducted. A closed form solution was used to calculate the stress based on the displacement values for the film that were obtained from experimental measurement.
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