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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Scientifically Designed Barrier Screw
Single-screw extruders are most widely used in processing plastic materials for melting solid plastic into molten state, suitable for forming into desired shapes. The performance of an extruder basically depends on the geometrical feature of the screw. Among various types of special screws developed to improve the extruder performance, barrier screws utilizing a barrier flight have been most successful. The barrier flight divides the screw channel into a solid channel and a melt channel. Only molten plastic material can flow over the barrier flight from the solid channel into the melt channel. Many types of barrier screw with different geometries have been developed and successfully utilized in practice. Advances in machining screws now allow manufacturing of screws with complex geometries without difficulty. A novel barrier screw with a complex geometry is developed which confirms to the extrusion mechanisms along the screw, eliminating the shortcomings of previous barrier screws.
Effects of a Locally Inhomogeneous Atmospheric Pressure Plasma Treatment on the Adhesive Strength
To improve the adhesive strength of bonds for joining thermoplastic parts, atmospheric pressure plasmas are frequently used for pretreatment. To increase the width of the treatment, nozzle designs are deployed with an eccentric orifice rotating around the central axis of the nozzle. This rotating movement of the emerging plasma can result not only in inhomogeneous jet formation but also in uneven pretreatment. To examine the effects of inhomogeneous atmospheric pressure plasma treatment on the properties of the adhesive bonds, peel tests were performed with adhesives on pretreated thermoplastic substrates. Various locally inhomogeneous surface states were achieved by the pretreatment while varying some of the parameters such as the distance between orifice and substrate, velocity, and the position and diameter of the plasma orifice. To describe the intensity distribution of the plasma on the substrate surface, a mathematical model was developed and compared with the attained bonding properties. The results of the peel test correlate well with the modeled intensity distribution of the plasma treatment. In future, this model could be used to obtain a better description of the locally different adhesive properties after atmospheric pressure plasma treatment.
Sandwidh-Structured Thermo Plastic Olefin Resin for Light Weight Automotive Bumper Facias Enables Molding by a Conventional Injection Molding Machine
A high stiffness, Thermoplastic Olefin (TPO) resin material has been developed for light weight automotive bumper fascias. Although most conventional TPO materials for automotive bumper fascias consist of three components: polypropylene, elastomer and filler, this newly developed TPO consists of 5 components: two kinds of polypropylene, two kinds of elastomer and filler. The composition in this TPO was designed to enable sandwich- structure molding by a conventional injection molding machine. This TPO has not only a much higher modulus, but also better flow-ability when compared to conventional TPO ’s. By using this TPO for automotive bumper fascias, the wall thickness can be reduced from 2.5mm to 2.0mm, while maintaining equivalent performance. The new material, with sandwich structure molding, achieves a weight reduction of approximately 20%. Moreover, in the bumper production process, the thinner wall thickness reduces cooling time for molding by about 50%. As a result, the bumper molding time can be reduced from 60 to 30 seconds, leading to major reductions in the amount of energy consumed in the production process.
Experimental Verification Of Process-Parameter-Dependent Temperature Simulation Of The Two-Stage GITBlow-Process
The Two-Stage-GITBlow-process is based on the idea of combining advantages of injection molding and blow molding techniques. This is achieved by producing a preform with gas-assisted injection molding, which is then inflated into a larger cavity in the same mold. In this paper the transient development of the temperature distribution in the preform is calculated via finite element method for the entire molding process. Material-specific temperature-optima are simulated and subsequently verified with experimental studies.
Modeling of the glass fiber length distribution in the compounding of short glass fiber-reinforced thermoplastics
The use of short glass fiber-reinforced thermoplastics for the production of highly stressed parts in the plastics pro-cessing industry has experienced an enormous boom in the last few years. The reasons for this are primarily the improvements to the stiffness and strength properties brought about by fiber reinforcement. These positive characteristics of glass fiber-reinforced polymers are governed predominantly by the mean glass fiber length and the glass fiber length distribution. It is not enough to describe the properties of a plastics component solely as a function of the mean glass fiber length. For this reason, a mathematical-physical model has been developed for describing the glass fiber length distribution in compounding. With this model, it is possible on the one hand to optimize processes for the production of short glass fiber-reinforced thermoplastics, and, on the other, to obtain information on the final distribution, on the basis of which much more detailed statements can be made about the subsequent properties of the molded part. Based on experimental tests, it was shown that this model is able to accurately describe the change in glass fiber length distribution in compounding.
Integrative approaches for the mechanical mold design in injection molding
The injection mold faces a number of different loads during the injection molding process of plastic parts. The effect on the mechanical behavior of the mold, inserts and adjacent processes can be complex and may cause bad final parts. By using an integrative simulation approach it is possible to take the process influence into account when calculating the solid body behavior of the mold in a structural simulation. A newly developed approach at IKV uses the advantages of the integrative approach and extends it by an automatic back coupling of deformation results during the filling simulation. This way the interaction of the melt flow and the deformation of inserts or mold components can be considered during the filling phase.
Creating Sustainable Growth by Incorporating Sustainable Development Behavior in Supplier Selection
As we work to make our companies more sustainable, it’s necessary to evaluate not only ourselves but also those we select to help us achieve an improved “triple bottom line”. Our vendors and suppliers today will need to be collaborative partners tomorrow if we want to achieve more impactful financial, societal and environmental results. To evaluate a potential sustainable collaborator, consider a teachable, measurable and repeatable process that outlines the questions and judges the responses; then look for potential suppliers that have an observable culture of sustainable development and continuous improvement. You should be able to witness their culture in action when dealing with company officials and representatives. There are clear signs for companies with sustainable development cultures. When they are combined with a set of stewardship behaviors that drive sustainability, they make great suppliers. We have identified seven distinct stewardship behaviors that can be broken down into contributors to the Triple Bottom Line aspirations of every company focused on their on sustainable growth. For the environmental bottom line, consider “touch”; for societal goals, consider the behaviors such as “teach, treat and tout”; and for the profit driver, focus on behavior resources such as “time, talent and treasure”. These seven behaviors have attributes that can, and should be evaluated and measured as we chose our suppliers. In our presentation, we take a look at each separately to give us insight into the complete value a supplier can deliver.
Ultrasonic welding of hygroscopic materials - influence of moisture on the welding process
The welding of hygroscopic materials such as polyamide can lead to unstable conditions during the welding process. Due to changing material properties the ultrasonic welding process is influenced largely by the moisture level of the welding parts. To achieve stable welding processes and high weldline qualities it is necessary to learn more about the influence of moisture on the material properties and the ultrasonic welding process. To perform a scientific examination of the influence of moisture on the ultrasonic welding process, the interactions between the material properties and the welding process are determined in relation to the moisture content. With the aid of welding tests, it can be shown that with constant welding parameters the attainable weld strength decreases with increasing moisture load. With recommendations on optimum moisture contents and a process-integrated control of the actual moisture content, poor-quality welds can be avoided. Through a direct control of the actual condition it is possible to dispense with complete predrying, which has until now been seen as the only way to ensure reliable welding of hygroscopic materials.
Influence of self-bias on barrier and elongation properties of barrier coatings deposited on flexible PET films
Polymers gain more and more market shares due to their favorable properties such as lightweight, flexibility and transparency which makes them suitable for food packaging, organic light emitting diodes (OLED) and flexible solar cells. Nonetheless, due to their macromolecular structure plastics do not offer sufficient barrier functionality against oxygen and water vapor permeation, which is a key demand in a variety of applications. A common solution in plastics processing is the deposition of thin silicon oxide layers using microwave (MW) excited plasma processes. Unfortunately for some applications silicon oxide layers do not fulfill requirements concerning elongation properties especially when deposited on flexible plastic films. It is known that because of the brittle behavior of the coatings, induced strain of 1 – 2 % results in a cracking of the deposited thin coating and therefore a loss in barrier properties. Adaption of the self-bias using a radiofrequency (RF) source is one possible way to enhance barrier properties due to deposition of coatings with a higher density. When deposited on flexible substrates, a possible impact on elongation properties has to be taken into account. Since a variation in self-bias leads to a change in surface structure, the mechanical properties of the films have to be taken into consideration.
Development of a Process Technology for High Volume Production of Thermoplastic Composites Based on Hybrid Rovings
Continuous fiber reinforced thermoplastics are increasingly used for lightweight construction parts due to their relatively easy processing. Yet, a cost effective use for structural components is still limited due to the absence of an appropriate and economic high volume production technology. Therefore, a new process technology for the production of lightweight parts within short cycle times is being developed at the Institute of Plastics Processing (IKV) at RWTH Aachen University. This paper presents first results of the research on the process technology based on fiber spraying and consolidation of preforms made of chopped hybrid rovings.
Recycling of Polylactide for Packaging Applications
Polylactide (PLA) is a bioplastic which has a high potential for packaging applications. Due to a high raw material prize and a limited availability the usage of PLA is limited apart from some niche products at the moment. Nevertheless, the number of applications is increasing. At the Institute of Plastic Processing (IKV) the recycling behavior of PLA is evaluated. Recycling helps to cut the raw material consumption and lowers material costs. Additionally, it improves the ecological balance. Following the industrial praxis different recycling strategies are analyzed. This paper gives a review about the multiple processing of PLA and the processing with melt degassing.
Continuous Extrusion of Physically Foamed Silicone Rubber Profiles
The foaming of rubber products offers saving potential with respect to component weight, material consumption and costs, while damping properties can be improved. For foaming of high-temperature vulcanizing (HTV) silicone rubber, the use of chemical blowing agents is state of the art. Physical blowing agents such as inert gases have ecological, economical and process-engineering advantages. This paper presents results of a current research project focusing on the development of a continuous process for the physical foaming of solid silicone rubber using nitrogen as blowing agent. The main aim is the achievement of a constant process in order to produce homogeneously foamed rubber profiles and the identification of quality-determining parameters.
Interdependency of Machine Settings and Temperature Profiles - An Experimental Study on Extrusion Embossing for the Replication of Microstructures
Replicating microstructures for functional surfaces in a fast and economic way is crucial for many technical applications. In this paper an experimental study on the variothermal extrusion embossing is presented. Polyethylene and polypropylene grades are used to manufacture hydrophobic films. Microstructure geometries as well as static and dynamic surface behavior in contact with purified water are analyzed. A theoretical approach to estimate the distinctive temperature profile that is generated according to processing conditions (e.g. haul-off speed, temperature of the embossing roll, etc.) is verified experimentally. Thus, the assumption is confirmed that a set of processing conditions (responsible for a specific replication accuracy) can be transferred to another set of conditions while keeping the replication quality constant.
Piezo-Based Mold Design for Injection-Compression Molding of High Precision Plastics Lenses with Minimized Centering Error
Centering errors in the alignment of the surfaces of optical lenses lead to aberrations. In spite of very precise molds and processes, a lateral offset between the two mold halves and therefore between the optical inserts occurs and leads to centering errors in the replicated optical components. A newly developed mold design with integrated piezo-actuators allows the adjustment of the die-sided optical insert and with it the minimization of the centering error. Therefore it is possible to influence and reduce the geometrical error and raise the optical performance of plastics lenses without a machining of the mold.
Manufacturing of Elastomeric Hollow Bodies Using the Projectile Injection Technique
Injection molding is the most important process to manufacture complex polymer parts. However, today the injection molding of elastomers almost entirely produces solid workpieces. Functionalized complex hollow components, e. g. for the conduction of medias, are often manufactured in costly multistep processes. The projectile injection technique offers a new approach to easily produce elastomers in a one-step process into complex hollow parts. This paper discusses the requirements on peripheral equipment and mold design and gives impressions of the effect of the process parameter variations on important quality criterias for this innovative process.
Temperature and Sliding Distance Dependency of Assembly Molded Friction Clutches
The market for mechatronic actuator devices in the automotive sector, as well as in the field of white goods (household appliances), brown goods (home entertainment), and red goods (air conditioning in buildings) has been growing constantly throughout recent years [1, 2]. During use, the actuators not only have to mechanically withstand the nominal load, but often also higher peak loads. Peak loads occur, for example, in the case of blocking, reaching the end position of the adjustment rail of a car seat or a car mirror. There are four commonly used approaches for overload protection: adjustment of component to applied load over-sizing of mechanical parts - limiting load electrical current limitation - use of sensors use of a mechanical overload protection system. An over-sizing of machine elements, e.g. gears, is easily achievable but not desirable, since overall weight and costs increase. Electrical current limitation and use of sensors are almost weight-neutral, since the circuit board will be extended by only a few electronic components. However, with a higher level of complexity, the risk of defects rises and overload protection in an unpowered state, e.g. for the case of vandalism, is not possible. Another approach is the use of a machine element with an integrated mechanical overload protection, such as a friction clutch. A friction clutch combines the function of motion transmission and mechanical overload protection. A benefit is its full function in an unpow-ered state, which thus provides effective protection against vandalism. The technology of assembly injection molding opens up an economic way to produce these plastic multi component machine elements, see Fig. 1. When made by assembly injection molding, additional costs due to a more complex mold have to be taken into account, though, by using function integration within transmission components, this cost increase can be kept low. Well-defined design should allow weight and com
Shear and Extensional Rheological Evaluation of Polylactide-Nanographite Platelet Nanocomposites through Constitutive Equations
Polymer based nanocomposites are fabricated through the incorporation of nanoscale inorganic solids into polymeric matrix. The focus of this research was on the production and rheological investigation of polylactide (PLA) and nanographite platelets (NGP) based bionanocomposites. In the current study, the linear viscoelastic behaviour of the samples was investigated in order to study the effects of the enhanced dispersion of NGP fillers on the rheological properties of the nanocomposites. Uniaxial extensional experiments were also carried out to analyse the impacts of the nanofillers on linear viscoelastic envelope (LVE) and non-linear viscoelastic behaviour (strain hardening region) of the nanocomposites. Furthermore, in order to provide an accurate prediction of the extensional viscosity behaviour of PLA/NGP nanocomposites, the modelling of strain-hardening behaviour of neat PLA and its nanocomposites was investigated using steady shear viscosity, relaxation spectrum and damping function based on Papanastasiou-Scriven- Macosko (PSM) version of Kaye-Bernstein-Kearsley-Zapas (K- BKZ) model.
Evaluation of Mechanical Property and Flame Resistance on Bio-Based Polymer Compounds
This paper describes the evaluation of the mechanical properties and flame resistance on bio-based polymer compounds of Poly (lactic acid) (PLA) and Polyamide 11 (PA11). A compounding technology and mechanical properties of PLA and PA11 using a compatibilizer were firstly studied to improve the thermal resistance and the impact strength of PLA. Some compositions of PLA/PA11 blends using a compatibilizer were investigated. After some flame retardants which were not halogenated and toxic materials were blended to the composition of PLA/PA11/compatibilizer, the mechanical properties and flame resistance were also evaluated as compared with the commercialized PLA and Polycarbonate (PC) alloy. The flammability test was conducted with the multi-cone calorimeter to obtain the relation between the heat release rate or the integrated heat release value and the combustion time.
Calculation of the Anisotropic, Temperature-Dependent Thermal Expansion Coefficient (TEC) of Parts Made From Short-Fiber-Reinforced Polymers
For the design of injection molded parts made of short-fiber-reinforced polymers, the anisotropic, geometry- and temperature-dependent thermal expansion coefficient (TEC) is often needed at the early stages of the design process, for example during material selection. The data usually available from material suppliers does not consider temperature dependency and the influence of geometries such as part thickness. State-of-the-art calculation methods such as the rule of mixture neither include these effects. Hence the development of simple models designed to estimate the TEC at the early stages of development is of interest. This paper deals with a method for engineers working in research and development to calculate the geometry- and temperature-dependent anisotropic TEC of parts made from short-fiber-reinforced polymers under consideration of fiber orientation. To evaluate the validity of the method, the results from the calculations were compared to measurements conducted on parts of different thicknesses. Here a good correspondence with the anisotropies of the TEC in different part directions was achieved.
Non-Isothermal Melt Crystallization Behavior of Poly(Ethylene Terephthalate)/Graphene Nanocomposites
Poly(ethylene terephthalate)(PET)/graphene nanocomposites were prepared by melt mixing to characterize their gas permeability and mechanical properties. With 2 wt% of few layered graphene, PET/graphene composite films show more than 70% decrease in N2 gas permeation and 10–21% increase in storage modulus, E'. Their non-isothermal crystallization phenomena from the melt were also investigated by differential scanning calorimetory (DSC). Crystallization temperature, Tc, of PET/graphene nanocomposites was higher than that of PET/MWCNT nanocomposites. This suggests that the nucleation effect of graphene was higher than that of MWCNT and was enhanced with the increase in concentration of graphene. On the other hand, PET/graphene nanocomposites show shorter half crystallization time, t1/2, than neat PET at lower concentrations, and t1/2 increased along with concentration of graphene. From Raman spectroscopy, it was shown that PET chains in nanocomposites are confined strongly in the presence of an excess of graphene. This confinement effect suggests that crystal growth rate of PET was suppressed by graphene in nanocomposites.
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