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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
Shear Stress Nucleation in Microcellular Foaming Process
Lee Chen, Kent Blizard, Xiang Wang, May 2001
The effect of shear stress on the foaming process has been studied using the Foaming Process Simulator developed previously. The polymer samples were saturated with gas in the test chamber. A rotor was used to apply shear stress to the polymer samples. Foams were obtained by releasing the pressure quickly. Polystyrene, filled and unfilled, was used as the material. The cell density was analyzed with a scanning electron microscope. It was found that the cell density was significantly increased by introducing shear stress. The higher the shear stress the more significant the effect. A cell stretch model has been developed to explain the cell nucleation enhancement with shear stress. The nucleation sites are stretched under the shear stress. The stretched nuclei are much easier to expand for cell formation due to their larger surface areas and non-spherical shapes. The model prediction shows the same tendency of the effect of shear stress observed in the experiment. The key issue with shear stress nucleation is the transformation of mechanical shear energy into surface energy.
Application of the Time Temperature Shift Principle to the Material Behaviour of Rubber under High Deformations
Andreas Grambow, Edmund Haberstroh, May 2001
For the finite element analysis, the stress/strain behaviour of the material has to be given in mathematical formulations (material models). These material models include parameters, which have to be determined by material testing. The material testing has to be carried out at time/temperature conditions, which correspond to those of the rubber part. Depending on the number of different time/temperature conditions, this can lead to a time and costs consuming test effort. This paper describes the possibility of test effort reduction for a wide range of time/temperature conditions with a new method, which uses the time temperature shift principle (TTS-principle). Examples are presented for three rubber materials (NR, ACM and NBR/NR) using this new method in conjunction with the WLF-equation and the van't Hoff-equation.
Introducing New Injection Molding Technologies into Small and Medium-Sized Enterprises
Andreas Franz, Walter Michaeli, May 2001
Special injection molding techniques are well-suited to provide small and medium-sized injection molders with a technological advantage over their competitors. On the other hand the introduction of special processes demands careful and detailed planning in order to be successful, a requirement that often overburdens these enterprises, whose reduced personnel resources often do not permit the elaboration of a thorough concept. This contribution shows a systematic approach of how the project of implementing a new injection molding technology can be structured, regarding not only the technological, but also organizational and personnel-related aspects and the interconnections between them. A choice of these aspects is listed in Fig. 1.
Thermoforming Low Density Glass Reinforced Thermoplastic Sheet
Valérie Bertrand, P.J. Bates, Christian de Grandpré, Abderrahmane Meddad, Enamul Haque, May 2001
Experimental studies were performed to assess the thermoformability of low-density polypropylene sheets reinforced with long discontinuous glass fibers. The effects of material parameters (glass fiber loading and sheet basis weight), mold parameters (cavity depth), and processing parameters (sheet temperature, and pressure) on part thickness, and glass fiber distribution were evaluated. The results indicate that, for the parts studied, pressure assist is required for thermoforming. Part characteristics were observed to be reproducible and constant over a wide range of sheet temperatures and pressure assist levels. Part dimensions were compared with those obtained using a thermoforming simulation package developed at the National Research Council's Industrial Materials Institute. Simulation results show that volume is not conserved when this low density material is thermoformed.
Chraracterization of Properties of Polypropylene Modified with Elastomers Based on Metallocene Catalyst Technology for Automotive Applications
Y.B. Vasudeo, R. Rangaprasad, A.Y. Kharade, May 2001
The fast growing Indian automobile industry has accepted polypropylene (PP) and ‘value addded’ compounded polypropylene based products for wide range of application. Modern fuel-efficient car seen on Indian roads have accepted PP and PP-based compounds. Almost 30 kg of PP and PP based compounds find their way wide range of automobile components like bumpers, instrument panel, pillars, trims, brackets and consoles. For these application PP is modified with elastomers and/or fillers to achieve the best possible balance of melt flow and impact stiffness. Traditionlly, Indian compounding industry has worked with elastomers bazed on Ziegler-Natta catalyst technologies such ethylene propylene diene rubber (EPDM). The metallocene catalyst technoloogies has brought about a revolution in the field of elastomers. These are wide range of MFI, moony viscosity, refractive indices and mechanical properties “tailor made” to suit different applications.
Micro Assembly Injection Molding - Mold and Processing Technology
Christian Ziegmann, Walter Michaeli, May 2001
Micro injection molding is a suitable process not only for the production of microstructures, but for the assembly of microsystems as well. For that specific process, which is based on two-component and insert technologies, an appropriate mold technology has been developed. The process parameters are determined by several sensoric elements, including an endoscopical device. During the investigations the process is characterized with regard to the influence of temperatures, injection parameters, material combinations, as well as the behavior and influence of inlay parts. Different test structures are presented, for example two-component hinges, functional fluidic structures and microoptical fibre connections.
In-Mold Film Decoration - Advanced Process Technology for Innovative Applications
Martin Wielpuetz, Walter Michaeli, May 2001
The requirements on the optical design and exclusiveness of molded parts particularly with regard to the automotive industry and consumer products place high demands on the injection molding process. The in-mold film decoration process is a technique to produce film-decorated, injection molded parts. High surface quality and a flexible surface design may be achieved by various kinds of decoration materials in combination with the advantages of a large scale integration and a highly automated production. New product development tools are necessary to fulfill the demands on quality and to seize new application opportunities despite of the increasing economical and ecological demands.
Gas-Assisted Rubber Injection Molding
Hendrik Wehr, Edmund Haberstroh, May 2001
Gas-assisted injection molding (GAIM) is not only for thermoplastics, which are limited in their physical properties, an interesting manufacturing technique, but also for rubber. In rubber processing, GAIM is an alternative to conventional manufacturing methods like extrusion. Using GAIM, the manufacture of highly integrated media ducts or hollow sealing systems is possible in one shot, which means a reduction of costs. Due to the different processing characteristics of rubber, the experience gained with GAIM in thermoplastics processing are not directly transferable. In this paper examinations about setting parameters, mold design, required material properties and equipment are presented.
Process Optimization for Reactive Blending and Compatibilization of PA 6 and PET in Extrusion
Sven Prollius, Edmund Haberstroh, May 2001
Blends of PA and PET do not have a minor significance in industrial production any more. Especially since the European beverage industry decided to use (multi- and single layer) PET bottles containing PA, the economic and ecological interest in recycling PA and PET is stringently increasing. In former research projects, where IKV has been involved, the compatibilization of PA and PET in extrusion was simply established. New investigations, focussing on the process optimization, enable to correlate the process parameters with the material properties. Therefore an extruder cascade was developed for a one-step-in-situ compatibilization and in addition a new characteristic parameter was constituted which is independent of the type of extruder.
Predicting the Cooling Conditions at Blown Film Extrusion Lines by Modeling the Cooling Air Stream
Friedrich Ohlendorf, Jochen Hauck, Walter Michaeli, May 2001
In order to develop a process model for the cooling air stream in blown film extrusion, an experimental analysis of the cooling conditions such as air velocity, temperature and pressure, was carried out. Thereby, a fundamental correlation between the cooling conditions and the resulting film temperatures was found and has been transformed into a theoretical description, whereat the air stream is described as a steady-state, two-dimensional, turbulent wall stream. With help of this model, the calculation of the air velocity and pressure along the bubble is possible. As a result, the temperature distribution in the bubble inflation area can be calculated by a dimensionless heat transition law.
Analysis of Internal Structure of Injection-Molded Parts Based on a Three-Dimensional Simulation Software
S. Hoffmann, W. Michaeli, May 2001
The computer simulation of the injection molding process is an essential tool to fulfill requirements on technical parts with respect to part quality and efficiency. In addition to melt flow simulation, the calculation of internal properties like crystallization is essential for the prediction of final part properties. After providing the three-dimensional melt flow simulation the calculation of thermally induced crystallization based on a three-dimensional temperature calculation can now be carried out. First results show a good qualitative agreement with experimental studies.
Study on Dynamically Vulcanized PP/EPDM Blends Using Predispersed Additives for Blow Molded & Extruded Products
A.K. Khamrai, Y.B. Vasudeo, May 2001
Thermoplastic vulcanisates (TPV) prepared from rubber -plastic blends by dynamic vulcanization route have gained considerable importance in recent years due to its dual characteristics of elastomers and thermoplastics.1- 4 The present study is aimed at the development of PP/EPDM based TPVs with various elastomer bound chemicals. The elastomer phase of EPDM/PP based TPV were dynamically cured by using different vulcanizing agents alone and with different combinations for e.g. sulfur-accelerator and alkyl-phenol-formaldehyde resin(SP-1045), SP-1045 and predispersed resin(Multisperse XP-1045- 45) . The properties of blends are studied by determining MFI value, tensile strength ,tension set & compression set. Adding SP-1045 resin alongwith predispersed resin (alkyl-phenol-formaldehyde resin in elastomer binder) in PP-EPDM based TPVs showed better tensile properties & lower compression & tension set values. The processability characteristics of all the blends during extrusion is also observed. Among all curatives, best optimum properties together with good processability are observed with a mixed curative system namely resin (SP-1045) and predispersed resin (Multisperse XP-1045-45).
Modified Polypropylene Homopolymer Films for Semi-Retort and High Retort Applications
Y.B. Vasudeo, Anand Gopalakrishnan, May 2001
Monolayer cast polypropylene in combination with PET and Al in multilayer film structures is used for high retort food applications. Similarly, monolayer cast film polypropylene in combination with nylon is used for semi-retort food applications. In the present investigation, work was undertaken by blending Repol® H100EY (MFI: 10gm/10') with ?-olefin copolymers at 20% W/W to study the effect on film processability and final film properties. The films produced for high retort food applications were metallized to study the permeability characteristics Investigation indicates good possibility for the blends in food packaging applications
Studies in Rotational Moulding of Linear Polyethylene Modified with Elastomers and Fillers for Automotive Exteriors
Y.B. Vasudeo, S.M. Nabar, J. Kapadia, R. Rangaprasad, May 2001
The dream of making an all-plastics" car is fast approaching commercial reality. The Indian automobile industry has leapsfrogged and is able to offer to local and international customers`s fuel-efficient and light-weight cars in designer models. Against the background the small electric car is innovation being explored by some automotive OEMs. As a further innovation development of linear low density polyethylene (LLDPE) compounds by rotational moulding technique is being scrutinized. At present vehicle bumpers are conventionally made by injection moulding. But as the initial cost for an injection tool is very high as compared to the rotational moulding tool vehicle manufacturers are looking into the possibility of using Rotational moulding as an alternative process to produce automobile parts. The scope of the present studies was directed towards the optimization of elastomers fillers and flow modifiers during compounding with LLDPE to make a compound suitable for car bumper. The studies were focussed on pulverizing aspects of the LLDPE compound containing elastomers and fillers. The Rotational moulding conditions were optimized for making hollow boxes. The cut specimens from the rotomoulded products were tested for flexural modulus and notched izod impact strength to arrive at the correct recipe."
Effect of Oxidation in Crack Growth Process in Polybutylene Tubing in Potable Water Application
Z. Gao, X. Niu, W. Zhou, Yu. Gogotsi, Alexander Chudnovsky, S.S. Stivala, May 2001
The mechano-chemical processes of degradation and fracture in Polybutylene (PB) tubing in potable water distribution systems have been extensively studied. The fracture is usually initiated in form of microcracks within a layer of degraded PB adjacent to the inner surface of the tubing. Some of those microcracks grow into cracks farther propagating through the pipe wall. Optical and SEM observations reported in the past suggested the presence of continuing chemical degradation in crack propagation stage. In this paper we report the results of micro FT-IR spectroscopy of regions surrounding a partially penetrating as well as breakthrough cracks in PB tubing. The absorption in carbonyl range recorded by the scans perpendicular to the domain surrounding the cracks shows a highly localized presence of carbonyl products along the crack trajectory. It provides a direct evidence of highly localized chemical degradation being a part of fracture process under consideration. The authors previous study of the effect of oxidation on physical and mechanical properties of PB combined with the direct observations of oxidation products presented in this paper serve as a basis for understanding and quantitative modeling of PB degradation and fracture in potable water applications.
Failure Analysis of High Density Polyethylene in Engineering Applications
Wen Zhou, Alexander Chudnovsky, May 2001
Comparative failure analysis of extruded HDPE potable water tubing and rotational cast HDPE automotive gas tank has been performed. Both structural elements have comparable wall thickness and similar sandwich type structure of the wall: a brittle core and relatively ductile outer and inner skin. A peculiar mode of brittle fracture related to the variation of material morphology across the wall has been found in both parts. Optical microscopy of fracture site reveals cracks initiated and propagated in the brittle core. Large deformation (necking) and resulting ballooning was found on the outer skin. The observed mechanism of failure is most likely related to material formulation and processing conditions. Application of fundamental principles and procedure of HDPE testing for lifetime are used for interpretation of the premature failure of structural elements in durable applications.
Optimization of PVC Dry Blend Productivity through Double Batching
V. Kannan, Y.B. Vasudeo, C. Paparao, May 2001
Attempt has been made to optimize the PVC dry blend productivity by adopting Double Batching". PVC resin was mixed with additional quantities of additives in heater mixer and subsequently remaining PVC resin added in cooler mixer before discharging. Both horizontal and conventional vertical cooler mixers were used and performances compared. The dry blends were tested for rheological properties physical properties and extrudability in the twin screw extruder for rigid PVC pipe manufacturing. Various sizes of the pipes were tested as per standards and compared with the pipes made by normal "Single Batching". The study revealed increased dry blend productivity and cost savings on power and labour when "Double Batching" was adopted."
Developments of Polypropylene (PP) Homopolymer Compounds for Automotive Exteriors
Y.B. Vasudeo, R. Rangaprasad, A.Y. Kharade, May 2001
The objective of the present work was to develop compounds from PP homopolymer using a combination of elastomer, glass fibre, filler and other additives to match properties of 15% Wollastonite filled nylon currently in use. The automotive component identified for this material substitution exercise was the front end of a two-wheeler called nose-cone". Blends were prepared by twin-screw melt compounding and later assessed for physical and mechanical properties on standard ASTM test specimens. The results obtained indicate that 15% Wollastonite filled nylon-6 can be easily substituted by low cost PP compounds. PP compounds can also be painted to match those nylon-based materials."
Studies in Polypropylene (PP) / Polybutylene Terephthalate (PBT) Blends for Extruded Products in Refrigerators
R. Rangaprasad, A.Y. Kharade, A.S. Mulay, Y.B. Vasudeo, May 2001
Mineral filled PP and blends and alloys of PP with High Impact Polystyrene (HIPS) or Acrylonitrile Butadiene-Styrene (ABS) or Polybutylene Terephthalate (PBT) are acquiring increased importance as innovative materials for sheet extrusion applications. The objective of this work was to develop an alloy of PP for sheet extrusion applications for refrigerator interiors. As a preliminary study, a blend of homopolymer PP, high impact copolymer PP, polyolefin elastomer and fillers together with anhydride modified PP and PBT was prepared by twin-screw compounding. The resultant product was characterized for physical and mechanical properties and these were compared with those of PP homopolymer.
Polyamide-Imide + Montmorillonite Nanocomposites
Ajit Ranade, Nandika Anne D'Souza, Bruce Gnade, Teresa D. Golden, May 2001
A Polyamide-imide (PAI) + montmorillonite nanocomposite was investigated. The material has a potential application in magnetic wire enamel coatings. Montmorillonite was introduced into an uncured PAI + aromatic solvent suspension. Curing of the sample was achieved by step-wise heat treatment. Polarized optical microscopy was used to confirm uniform distribution of the montmorillonite in the PAI. Transmission Electron Microscopy (TEM) and x-ray diffraction was used to examine clay dispersion. The results showed that a new nanocomposite was developed having a concentration dependent dispersion throughout the PAI matrix. Differential Scanning Calorimetry (DSC) was used to ascertain the impact of the clay on glass transition (Tg) of the resulting nanocomposite.


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