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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Bonding CFRP-Metal Structures in Vehicles
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
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)
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
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
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
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
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
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.
Profiles of Mold Ejector Pin Melt Density Sensors
Ejector pins in a two-cavity mold were retrofitted to sense injected melt flow and volume of the molding process. Two materials, two mold clamp forces, a cold runner sprue, and replaceable hot sprue bushing capability were run in an electric molding machine.Profiles of the sensed melt cavity volume and differences will be presented.
A System Analysis for Injection Molding Screw and Screw Tip
A system analysis for the screw and screw tip in injection molding is one of the keys to promote the machine performance. It explains several critical issues of plasticizing and injecting performances. This is a model to analyze the screw and screw tip with different materials at different machine parameters as a system and to optimize the performance in injection molding.
Increasing the Flexural Modulus of Rigid PVC at Elevated Temperatures
The use of PVC building products in hot climates has demonstrated the need for formulations that exhibit increased stiffness at elevated temperatures. Talc has been used as an additive to increase flexural modulus but this approach can produce an unacceptable drop in impact strength. This report presents the results of laboratory work designed to find ways to increase the stiffness of rigid PVC compounds at elevated temperatures while maintaining their room temperature impact performance
Computer Scale-Up Model for Desolventizing Highly Viscous Polymers in Kneader Equipment
A concentrated rubber solution (less than 20 % solvent) is fed to a high volume kneader in order to remove the solvent down to ppm level. A simulation program has been developed to describe this devolatilization step.The program predicts final solvent content, the filling level and the mechanical torque build-up. The program can be used to refine process control and the scale-up of this type of process.
Comparison of Devolatilization Technologies for Viscous Polymers
Devolatilization of solvents from viscous polymer cement is realized through stripping of solvent with steam in stirred vessels or directly by evaporating the solvent from the polymer. The later so-called direct desolventizing is realized in extruders or high volume kneaders. All 3 methods involve additional energy to drive out solvent either by partial pressure through additional steam (steam stripping), building and releasing pressure in order to explode the polymer bulk (extruder) or dynamic surface renewal (kneader).
Concurrent Engineering Approach for Designing a Novel Plastic Pallet
The concurrent engineering approach was used to design a lightweight, one-piece-tailored and very resistant pallet. Three CAD/CAE software programs were involved in the designing process. The pallet design went back and forth between the software until it was optimized and the part met all the functional, mechanical, processing, and machining requirements at the lowest pallet weight possible.
Material Selector for LLDPE/LDPE Blends for FFS Applications
There is a delicate balance between processability, mechanical properties and seal performance when LDPE/LLDPE blends are used. Choosing the right blend proportion is sometimes a very difficult job, and high resin and time consuming. An easy to- use selector that can run in most spreadsheet programs was devised based on DOE approach.
Properties Predictor for HDPE/LDPE/LLDPE Blends for Shrink Film Applications
A technique that involves design of experiments was developed to generate set of equations that predicts processing, mechanical and shrink properties of HDPE/LDPE/LLDPE blends. The results are presented in an easy-to-use spreadsheet that can be used even in pocket computers.
Effect of Ultrasonic Energy on Polymer Amalgamation
Ultrasonic energy was demonstrated to promote amalgamation between a polymer melt and polymer solid during injection molding. Advantages include the ability to injection mold at significantly reduced temperatures while achieving favorable bond strength. In addition, ultrasonic energy promotes joining chemically dissimilar polymers, bonding to inserts, and co-molding or overmolding dissimilar polymers.
Effect of Atmospheric Plasma Treatment on the Surface Energy of Polymers
This paper describes experiments to quantify surface energy changes on polymers after exposure to atmospheric plasma. Atmospheric plasma treatment permits the functionalization of surfaces at near-ambient temperatures. Various polymers were treated with the plasma unit, and the surface energy changes as a function of time and adhesion characteristics were monitored.
The Vented Barrier Screw
The typical barrier screw (high efficiency screw) concept has been modified to provide for venting (devolatilizing) of polymer through a bore in the drive-end of the screw. The bore is connected to the melt channel by a vent hole in the melt-channel screw-root. The melt channel is deep so that a free surface of polymer melt and path exists to release gasses to the vent. The screw design was tested and shown to process and devolatilize PET powder, PET pellets, and PEN pellets at greater rates and with less power than a conventionally vented two-stage screw in the same extruder with the very same polymers.
Extrusion Process and Screw Design Investigation via Experiment Design and Computer Simulation
This paper explores the value of Design of Experiments (DOE) statistical analytical techniques and mathematical modeling of extruder behavior to characterize extrusion performance.
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