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
Bonding CFRP-Metal Structures in Vehicles
Tino Fuhrmann, O. Hahn, September 2004
As weight reduction is required for ecological aspects and in certain areas of the vehicle for dynamic handling requirements and besides this metallic materials cannot be extensively substituted within the short-term structurally bonding metallic materials with CFRP is necessary. Cathodic dip painting (CDP) which precedes the bonding process is able to offer good protection in order to combat sub-surface corrosion (bondline corrosion) which is also familiar from bonded metal joints. If the CFRP structural part has to be painted together with the entire body-in-white the CFRP component and therefore the joining process may be integrated into the production sequence directly downstream of CDP. If joint painting is not necessary the joining process may be carried out at the beginning of assembly directly following paint drying. High thermomechanical stress in the production process can therefore be avoided and the problem is reduced to the vehicle's operating temperature range. The paper shows the characteristic properties of different adhesive systems e.g. two-component epoxy polyurethane or methacrylate in bonded CFRP-metal joints based on quasi-static test results. Especially the requirements on withstanding thermomechanical stresses in production and vehicle's operating temperature range are shown and evaluated by tests at different temperatures. The results shown in this article are developed in a cooperation project of Volkswagen AG Wolfsburg LWF Transfer GmbH & Co. KG and LWF Paderborn University Germany.
pCBT: A New Material for High Performance Composites in Automotive Applications
Michael Shoemaker, Dave Bank, Peter Cate, September 2004
Cyclic oligomers of butylene terephthalate (CBT®) represent a new chemical route to semi-crystalline thermoplastic polybutylene terephthalate (PBT). The oligomers of interest melt completely at about 150°C to produce a low-viscosity fluid that is ideal for wetting and dispersing fibrous fillers and reinforcements thereby enabling the development of composites that were previously not possible when working with high-viscosity commercial PBT. Introduction of catalyst to undiluted molten cyclic oligomer leads to rapid ring opening polymerization and the formation of high-molecular-weight thermoplastic PBT without the generation of volatile organic compounds. The polymer resulting from this polymerization will be hereafter referred to as pCBT. Treatment of cyclic oligomers in this fashion results in pCBT thermoplastic resin with a high melting point (230°C) and physical performance similar to that of other commercially available PBT resins. The low viscosity of these oligomers enables the selection of processing technologies that are typically reserved for thermosetting systems and that work in conjunction with easy flowing monomers or pre-polymers. The combination of excellent mechanical performance and the ability to utilize processing techniques typically reserved for thermosets enables broad uses for these oligomers in a range of applications including interior exterior and structural automotive components. Additionally the thermoplastic nature of pCBT holds promise to provide a low-capital route to a new family of pCBT-based recyclable materials made using a range of plastic processing technologies.
Evaluation of an Aromatic Amine Antioxidant in Glass-filled Poly(propylene)
Michael E. Gelbin, September 2004
Glass-mat reinforced thermoplastic (GMT) composites have increasingly begun to replace traditional sheet molding compounds in automotive applications owing to their reduced weight. Both processing and end use put special demands on the stabilizer package incorporated in the poly(propylene) resin phase of the GMT composite. A novel ternary antioxidant blend based upon an aromatic amine type stabilizer for superior processing stabilization in GMT will be presented. Processing stabilizer performance data as measured by the critical weight loss test at 230 °C will be discussed. Comparison of the arylamine based blend which is phosphite-free with a traditional phosphite-containing package of otherwise similar composition confirmed the superior performance of the former.
High Performance Natural Fibre Reinforced Sheet Molding Compound for Automotive Applications
Merry Lo, Suhara Panthapulakkal, Mohini Sain, September 2004
This research work aims to replace glass fibres in sheet molding compounds (SMC) by renewable natural fibres. These eco-efficient and cost effective SMC with natural fibres are gaining much attention in the automotive industry because of their specific properties. The specific objective of the work was to develop a high performance natural fibre hybrid SMC to meet the specifications required for automotive parts such as front fenders body panels etc. Hemp fibres with and without a combination of a small amount of glass fibres were used to reinforce vinyl ester resin for making SMC. Different combinations of layers of hemp and glass fibres were made to prepare SMC. Mechanical properties such as tensile and flexural properties and impact strength of the SMC prepared were found to be highly promising. The current OEM specifications for automotive parts for example rare lift gate and front fenders recommend the composite should have tensile strength of 62 MPa and tensile modulus of 2 GPa (Source of Automotive Engineers Car Technology yearbook 2000” USA 2000 Body panels Properties). SMC prepared by the combination of 45% of hemp fibres and 5% of glass fibres showed tensile strength and modulus were more or less same or better than that of the requirements for car body parts such as rare lift gate and front fenders (Tensile strength greater than 62 MPa and tensile modulus of 2 GPa).Use of this SMC with natural fibre is an economically viable alternative to SMC with glass fibres and at the same time it helps reducing the green house gas emission as there is lesser amount of synthetic resins and plastics.
Development of New Green SMC Resins and Nanocomposites from Plant Oils
Jue Lu, Richard P. Wool, September 2004
Sheet molding compound (SMC) is widely used in automotive parts appliances furniture and construction. These materials heavily depend on the petroleum supply which is depleting fast. The use of plant oils as an alternative source for SMC resins presents economic and environmental advantages over petroleum. Two synthetic methods have been used to develop new resins from triglycerides. The double bonds presented on the fatty acid chains were first converted to epoxy or hydroxyl functionality; the hydroxyl groups were maleinized while the epoxies were acrylated and then further maleinized. When these functionalized oils were combined with 33.3 wt% styrene the polymers showed mechanical properties comparable to those of commercial unsaturated polyesters. In addition these new resins exhibit adequate thermo-reversible thickening behavior with MgO. These triglyceride-based resins have good compatibility with natural fibers such as hemp and flax to form low-cost green composites. New bio-based nanocomposites were also developed using these new resins and organo-treated clays and the nanocomposites showed considerable increase in modulus and toughness. These new green materials show the promise to be used in the automotive industry.
Process for Manufacturing a High Performance Natural Fiber Composite by Sheet Molding
T. Behzad, M. Sain, September 2004
In the past few years natural fibers are finding an increased interest in polymer matrices. The natural fibers serve as reinforcement by enhancing the strength and stiffness to the resulting composite structure. In this study a novel processing technique has been developed for water based thermoset polymers to prepare resin-impregnated mats which can be used for sheet molding process to manufacture complex automotive semi-structural and structural parts. In order to optimize the curing conditions the mechanical properties of composites at different curing temperature and the crosslink density of the composites cured at different times were evaluated. The optimum curing cycle was obtained at 180 ºC for 10 min. Composites with one and two layers of impregnated mat with 40 % resin and 60 % fiber were manufactured and their performance were evaluated. The mechanical properties of the cured pure resin and hemp fiber acrylic based composites with two different fiber lengths were measured and the effect of fiber content and fiber length were investigated. The flexural strength was found to be around 94 MPa and the flexural modulus was 14 GPa for the composite.
Electron Beam Curing Demonstration with Automobile Structures
C.C. Eberle, C.J. Janke, C.S. Wang, September 2004
Continuous carbon fiber/epoxy automobile hoods were electron beam cured to demonstrate the capability to achieve curing throughput rates needed on automotive production lines. The project team demonstrated curing speed of 180 hoods/day. This demonstration extrapolates to 1600 hoods/day curing throughput using a more powerful electron accelerator and much higher throughputs may be achievable with innovative design and materials development. Single-pass curing was shown to be feasible. The curing costs are potentially attractive especially at high production volumes Test laminate properties considerably exceeded those of the finished hoods. Hood thermo- mechanical properties and surface finish need improvement. This is not surprising since this was the team’s first attempt to manufacture electron beam cured automobile structures. Several technical barriers were identified that need further attention.
Equal-Channel Angular Extrusion of Thermoplastic Matrix Composites for Sheet Forming and Recycling
T. S. Creasy, Y.S. Kim, September 2004
Equal channel angular extrusion creates novel properties in metal and polymer materials. Recently the authors investigated the effects of this process on commercial short fiber composites. Experiments show that ECAE provides a means for controlling fiber length and orientation in the extrudate. The process might transform continuous fiber thermoplastic matrix composite sheets into high volume fraction discontinuous fiber sheet for thermoforming. In addition the process might provide a method of recycling reground components into high-value sheets with a known fiber orientation.
The Effect of Surface Energy of Boron Nitride on Polymer Processability
Nimish S. Rathod, Savvas G. Hatzikiriakos, May 2004
Fluoropolymers have long been used as processing aids for surface melt fracture treatment of polyolefin extrudates. Recent developments have shown that a small amount of Boron Nitride powder successfully eliminates surface melt fracture and also delays the onset of gross melt fracture. Study of surface energy helps in understanding the different mechanisms of these two processing aids in eliminating extrudate melt fracture.
Fundamentals of Melt Fracture Elimination Using Fluoropolymer Process Aids
S.R. Oriani, G.R. Chapman, May 2004
Fluoropolymer process aids are widely used in polyolefin blown films to eliminate melt fracture. These process aids function by depositing a thin fluoropolymer layer on internal die surfaces, and promoting slip at the fluoropolymer – polyethylene interface. The present work describes how the morphology of fluoropolymer – polyethylene blends can be controlled to increase fluoropolymer deposition rate by using a new, rheology-modified fluoropolymer in combination with an interfacial agent.
Blown Film Characterisation
G.D. Smith, R. Spares, M.T. Martyn, M. Woodhead, P.D. Coates, P. Lafuente, B del Amo Fernández, May 2004
Effects of process changes on polyethylene blown films were studied using profile analysis techniques. The relationship between process parameters, barrel temperature, haul off rate and die gap, and film properties, thickness, blow up ratio (BUR), freeze line height, consistency of bubble profile were studied. An optical analysis system was developed which allowed film characteristics to be monitored during processing.
The Effect of Orientation on the Mechanical Performance and Thermal Properties of Extrusion Cast Metallocene Polyethylenes
B.G. Millar, G.M. Mc Nally, W.R. Murphy, May 2004
Cast films were prepared using a Killion single screw extruder, from a range of metallocene PEs of varied comonomer types (hexene, octene), using different haul off speeds (8-4m/min) and die gaps (700-250?m). It was found that samples with greater orientation in one direction had increased tensile strength and shrinkage in that direction. DSC analysis showed crystallinity to decrease with decreasing haul off speed.
An Investigation into the Cooling of Blown Film
Gregory A. Campbell, N. Ganesh, Sara W. Campbell, Lana Burl, May 2004
The focus of this investigation was develop a relatively simple model which could be used in blown film simulation. We desired to have the model represent the major contributors to the heat transfer for blown film. Our experimental results suggested that the heat transfer coefficient went through a maximum as the the bubble expanded. We have proposed a physical model which is consistent with our experimental observations. The model is based on a 3D representation of the boundary layer of ain around the bubble.
Process Stability Enhancement by Encapsulation Extrusion Method
Joo Sung Lee, Hyun Wook Jung, Jae Chun Hyun, May 2004
A film casting simulation has been used to demonstrate why the encapsulation extrusion process is so effective industrially in enhancing the stability of the extrusion. In the present study, it is intended to explain theoretically why and how the coextrusion of LDPE in encapsulation dies improves the HDPE process. The undesirable neck-in and draw resonance phenomena frequently occurring in the extrusion of HDPE are shown due to its low-melt-strength property, and consequently can be alleviated using high-melt-strength materials in the encapsulating dies.
Novel Barrel Heating with Natural Gas
Johannes Wortberg, Thorsten Schroer, May 2004
Normally for direct heating of barrels in plastic processing machines electrical resistance heaters are used. A newly developed heating/cooling system uses natural gas. This paper explains the design and realization of a unit where the exhaust air from a radial burner heats the barrel by convection and radiation. Integrated cooling possibility by a tangential incoming airflow also meets practical requirements. Transforming basic energy is not necessary, which leads to CO2 reduction and lower energy costs for the processors.
On-Line Visualization of PS/PP Melting Mechanisms in a Twin-Screw Extruder
Hongbing Chen, Uttandaraman Sundararaj, Krishnaswamy Nandakumar, Mark D. Wetzel, May 2004
The melting and deformation mechanisms of polystyrene (PS) and polypropylene (PP) blends were investigated through on-line visualization of the co-rotating twin-screw extrusion process. A sliding barrel technique was used to realize the on-line visualization with one glass window in the barrel. The axial temperature and pressure profiles along the screw channel were measured using the same sliding technique. Different melting mechanisms were found for the PP/PS (80:20) blend and PS/PP (80:20) blend.
Engineering Analysis of Devolatilization of Additives in Intermeshing Co-Rotating Twin Screw Extruders
Jongmin Keum, James L. White, May 2004
An experimental study of various operation conditions and screw configurations was made to understand and solve devolatilization problems in intermeshing co-rotating twin screw extruders. This includes studying additives (Nonane, Hexanol, p-Xylene) of polyethylene. We describe devolatilization through a model of interfacial area and mass transfer coefficients in an intermeshing co-rotating twin screw extruder.
Flow Behavior of Newtonian Fluid through Conveying Elements and Kneading Blocks
Anne Martine de Vries Robbé, David B. Todd, Léon P.B.M. Janssen, May 2004
The flow behavior of a Newtonian fluid through conveying elements and kneading blocks in a co-rotating twin screw extruder was examined by drag and pressure flow experiments. These results are compared with existing computer models. Also the flow behavior of the different kneading blocks and the conveying elements are compared with each other. The results can guide when to decide which mixing elements to use and can help with future computer modeling.
Polytetrafluoroethylene (PTFE) Paste Preforming: The Effects of Viscosity and Surface Tension of Lubricants
Isaias Ochoa, Savvas G. Hatzikiriakos, May 2004
Conventional processing methods are not applicable to PTFE due to its high melting point (342°C). Therefore, PTFE is processed by means of paste extrusion (extrusion of a mixture of PTFE powder with a lubricant). The physical properties of this new phase (lubricant) influence both the preforming stage as well as the rheology of the paste. In this paper, the effects of the physical properties of lubricant (viscosity and surface tension) on the preforming and extrusion pressure of PTFE paste are examined.
Temperature Gradients in the Channels of a Single-Screw Extruder
Mark A. Spalding, Daniel W. Baugh, Kurt A. Koppi, Walter C. Buzanowski, Anthony J. Bur, S.C. Roth, May 2004
A novel fluorescence analytical technique was used to measure the polymer temperature inside an operating extruder. The method allowed the temperature measurement of the polymer without interference from the surrounding metal parts. This paper will show some temperature data for molten polycarbonate in a single-screw extruder under processing conditions.
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