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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Martha J. Rogers, Kurt W. Koelling, Michael D. Read, Mark A. Spalding, May 2001
Resin suppliers and compounders often add fillers to resin base stocks to form high-value filled resins. These resins are typically used for automotive injection molded applications and color concentrates for in-house coloring. Materials are generally compounded on co-rotating, intermeshing twin-screw extruders using a variety of kneading block types. The goal of this work is to describe the effect of three-lobe kneading block configurations on the dispersion of calcium carbonate into polystyrene resins.
Min-Young Lyu, Hak Cheol Kim, Hee Cheol Shin, Jae Sik Lee, Sung-Taek Joo, Yong Hwan Kim, May 2001
Petaloid shape in bottom design for carbonated PET bottle is wide spread. Through this paper we investigated the causes of bottom crack. We then redesigned petaloid bottom to prevent bottom crack. We examined the material property variations according to the stretch ratio of PET and analyzed stretches of bottom in blowing processes. We also performed crack test to observe a crack phenomena. The effective stress and maximum principal stress were examined by computer simulation. We concluded that the bottom crack occurs because of not only insufficient strength of material due to the insufficient stretch of PET but also coarse design of petaloid shape. The crack in bottom of bottle occurred through crazing. The highest maximum principal stress occurred at valley in petaloid bottom of bottle and this strongly affected the crack in bottom. We redesigned petaloid shape to minimize maximum principal stress, and this result in increasing the crack resistance.
In order to obtain detailed understanding of the mechanism and action of PVC stabilizers, a new exact method has been developed for the determination of the stabilizing efficiency of these compounds. This is based on the separation of the direct chemical stabilization, i. e. blocking according to the reversible blocking mechanism of PVC stabilization, and the HCl-scavenging capacity of stabilizers. This new method has been applied to investigate the stabilizing efficiency of different stabilizers, such as metal carboxylates and tin compounds. In this study, the stabilizing efficiencies of these stabilizers will be compared by carrying out PVC degradation under inert and oxidative conditions. The stabilizing efficiencies allowed setting an efficiency order for a variety of stabilizers. These studies also led to surprising findings for thermooxidative stabilization under the applied conditions.
In order to develop a cost effective way to new Polyamide 6 (PA 6)-alloys and blends, solutions of Polysulfone (PSU) in ?-Caprolactam have been polymerized by the widely used hydrolytic process. The resulting materials have been characterized by various analytical techniques. Compared to melt blended PA 6/PSU-samples, materials prepared by the polymerization process reveal a unique morphology with dispersed PSU-particles having average particle diameters below 100 nm. This morphology is a consequence of in situ created copolymers, therefore these samples were designated as in situ PA 6/PSU-alloys. The in situ alloys offer improved heat distortion temperature and excellent toughness.
In order to develop a new polymeric material with a nice combination of high heat resistance, chemical resistance and flow, polysulfone (PSU)/ polyamide (PA) blends have been investigated. The incompatibility of these polymers can be overcome by the addition of functionalized PSU, especially anhydride terminated PSU (PSU-PhA). Since PSU-PhA sometimes contains traces of low molecular weight compound, the influence of such reactive impurities was investigated with phthalic anhydride (PhA) as model compound. The amount of in situ created PSU-PA-copolymers is significantly reduced by the addition of PhA during the extrusion process resulting in a coarsening of the morphology.
Philip Jacoby, Richard Sullivan, William Crostic, May 2001
Over the past decade wood filled polyolefins have gained acceptance as a replacement for lumber in high value outdoor applications, especially decks [1-2]. Most of the products offered have used post consumer polyethylene as the polymer matrix, with wood flour as the typical filler. Polypropylene offers specific benefits over polyethylene in terms of higher stiffness, strength, heat deflection temperature (HDT), and better creep performance. In this paper we compare the properties of wood flour (WF) filled polypropylene and polyethylene at various WF levels. The polypropylene resins include both standard Zeigler-Natta homopolymer (HPP) and high crystallinity (ACCPRO) homopolymer, as well as an impact copolymer (ICP) resin. The polyethylene resins include high density polyethylene (HDPE) and low density polyethylene (LDPE). The effect of different levels of a maleated polyolefin coupling agent were also examined. A substantial improvement in stiffness, strength, and high temperature performance was observed for all of the PP based resins relative to that of the polyethylene based materials, and the ACCPRO based composites gave the highest level of performance.
Thomas C. Yu, Donald K. Metzler, Manika Varma-Nair, May 2001
The addition of selected metallocene plastomers can improve the drop impact strength of parts molded from clarified polypropylene with slight effect on haze and gloss. This paper demonstrates the effects of plastomer structure (melt index, density and comonomer type), on the optical, physical and impact properties of clarified PP. A thermal segregation experiment shows the preferred methylene sequence length to minimize haze. Crystalization half-time experiments show that the addition of plastomer does not seem to hinder the polypropylene crystallization process. Finally, SEM micrographs are provided showing the dispersion of plastomer in an injection molded container.
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.
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.
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.
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.
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 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.
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 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.
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.
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.
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.
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).
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
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