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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Part and Mold Design Guidelines for the High Volume Compression Molding of Carbon Fiber Reinforced Epoxy
The objective of this paper is to discuss unique part and mold design requirements for high volume, cost competitive compression molding of carbon fiber reinforced epoxy (CF/E) uni-directional prepregs (UD). The typical part and mold design for compression molding of chopped fiberglass reinforced polyester sheet molding compound (SMC) will be used for comparison. Information that can be used as a design and processing guide for composites engineers involved with the development of high stiffness and strength CF/E for application in the transportation industry will be shared.
High Throughput Compounding: Application Specific Thermoplastic Compounds Developed
Polymaterials has developed a new high-throughput compounding (HTC) technology which generates thermoplastic formulations and DIN-ISO compliant test specimen accepted by engineers and the plastic industry. This technology accelerates the development of new compounds and is also much more cost-effective since only a fraction of material and time is needed compared to the conventional process. HTC not only increases the output significantly but also generates more insights enabling one to push innovation and to cut time to market for new products. The presentation introduces the technology and illustrates its capabilities by demonstrating several case studies.
THERMAL CONDUCTIVITY OF HYBRID FILLED HDPE NANOCOMPOSITES
In this study composite materials based on highdensity polyethylene (HDPE) with fillers containing nanostructures were prepared using melt mixing. Vapour Grown Carbon Fibers (VGCF), multiwalled carbon nanotubes (MWCNT) of the types Baytubes® C150P and NanocylTM NC7000, anthracite powder, microsilica, organoclay and expanded graphite (EG) as well as mixtures of these fillers were used. The amount and mixing ratios of the hybrid filled systems have been varied to determine the effect on the achievable level of thermal conductivity as measured on pressed plates. The filler dispersion and phase adhesion were studied using scanning electron microscopy. When limiting the maximum filler content to 10 wt%, the highest enhancement in thermal conductivity by 166% was found for VGCF followed by a 1:1 filler combination of VGCF with EG (148%).
A REVIEW OF LONG FIBER THERMOPLASTICS (LFT) COMPOSITES DESIGN
Long fiber thermoplastic (LFT) composite design studies often emphasize fiber content but are sketchy on fiber-orientation, fiber-matrix interface and mold design. In this paper we detail a comprehensive approach to designing with LFT materials. Specific examples are given. Carbon-fiber compounds were successfully substituted for die-cast magnesium parts by redesigning the metal part for injection molding. Tailored fiber architectures were achieved through strategic gate locations, as advised by Finite Element Analysis (FEA) and Mold Flow Analysis (MFA). Mechanical properties were enhanced through modified molding processes.
Influence of the Mould Cooling on the Quality and Reproducibility of Injection Moulded Parts
The use of pulsed cold water instead of tempered coolant is suggested to be a versatile and cost-efficient technique for the cooling of injection moulds. However, the advantages and limitations of such discontinuous cooling strategies are still a controversial issue. In this paper the behaviour of a discontinuous temperature control system is analysed with a particular focus on the reproducibility of the process and the realisable dimensional stability of the parts and compared to that of a continuous cooling. For the investigations both a conventional and a conformal cooling channel geometry are considered. It turns out that at high mould temperatures the warpage of the parts can be reduced by use of discontinuous cooling, but at the same time the reproducibility of the process is affected adversely. The regulation of the discontinuous cooling proved to be challenging especially in combination with conformal cooling.
CONSIDERATION OF WELD LINE STRENGTH WITHIN THE SIMULATION OF SHORT FIBER REINFORCED THERMOPLASTICS
Weld lines are formed during injection molding, when two flow fronts meet. They are often not avoidable in complex technical parts. Their presence reduces mechanical strength, especially in high performance short fiber reinforced materials. Evaluating the load of highly stressed parts requires accurate knowledge of the interrelationship between the type of weld line, its morphological structure and the resulting mechanical properties. This paper aims at the development of a simulation method which enables the mechanical properties of weld lines to be considered precisely in part design.
DESING OF INJECTION MOLDS FOR FLOATING VALVE SYSTEM USING PET BOTTLES AS FLOATING DEVICE
The plastic parts for a float-valve system were designed. In the design was considered the use of PET bottles as floating device instead of the regular spheres, in order to promote the reuse of this plastic container and to decrease plastics residues. Additionally, the part thickness was reduced to use less plastic on the parts, and to decrease cycle times. All molds are two-plate and two cavities. The refrigerating system proposed uses U-shape channel, and the expulsion system is composed by ejector pins. Threaded connector´s mold is more complex due to require two-step opening.
Modeling Container Shelf Life & Top Load Performance
The use of performance modeling is becoming more and more critical to the packaging industry. This trend is driven both by lightweighting efforts and the need to shorten package development times. The primary driver for reducing the amount of material used in packaging is cost reduction, with environmental positioning an ancillary benefit. However, it is critical to not compromise the shelf life or creep performance of the package, particularly in regions of the world with temperature extremes. This paper will explain key elements necessary for precise modeling of package shelf-life performance. The mathematical models considered are M-RULE® Container Performance Model and Virtual Prototyping™ Software. Some examples of how computer modeling has been applied to optimize package performance will be discussed.
A self-optimising injection moulding process extendable by an incremental cooling system
The conventional control of the injection moulding process is based on machine variables, which cannot sufficiently characterise the course of the process. Hence, a system that controls the injection moulding process based on process variables has been developed at the Institute of Plastics Processing at RWTH Aachen University during the last years. The concept of the self-optimising injection moulding process is based on this research. This paper describes the concept of the self-optimising injection moulding process during the holding pressure phase and the idea of an extension by an incremental cooling system using small-sized cooling areas.
ON MULTISCALE SIMULATION OF THERMOPLASTIC PARTS – CALCULATING MOLECULAR ORIENTATION
The general aim of the Cluster of Excellence “Integrative Production Technology for High-Wage Countries” is to overcome the actual contradictions between value- and planning-orientation as well as between scale and scope in production technology. One important aspect of this approach is the development of virtual production systems to increase simulation accuracy and thereby to reduce development times and costs as well as to optimise the utilisation of material. In this paper new developments in the field of the calculation of molecular orientation are described and a validation with different experimental measurements is presented.
OPTICAL ANALYSIS OF EXTRUDATE SWELLING OF POLYMER MELTS
Miniaturization and individualization are some of the current and in future ongoing trends in producing business in general and they also are influencing the plastics processing industry. To meet the upcoming challenges a lot of research is being done in the field of micro-extrusion. This work investigates a method to identify the phenomenon of extrudate swelling of micro extruded polypropylene using an optical analyzing method. Experimental data varying the pressure is presented and an optical analysis is explained. The results show the suitability of the method but reveal that some more experiments have to be done in order to formulate clear statements.
Three Dimensional Finite Volume Method Simulation of the Melting Zone in a Single- Screw Extruder
This paper presents a 3D numerical model to analyze the melting process in a single-screw extruder. The fundamental equations of fluid dynamics are solved using the Finite Volume Method. The software Fluent distributed by ANSYS, Inc. was used for the numerical calculations. The computing domain is a helical-shaped screw channel. The solid bed is modeled as a fluid with a very high viscosity by adjusting the formulation of the Carreau model for temperatures below the melting temperature. The model predicts the melting length, pressure build-up and the velocity and temperature distribution within the channel.
In-Vitro Modeling of Blood Vessels
There has been much research in the biomodeling of human blood vessels. Models of human blood vessels can be used for aids in future research of new medical devices that can be preliminarily tested in an in vitro setting and that could potentially lead to breakthroughs in the medical device industry. There is also the possibility to use such models for the training of surgeons, especially for complex operations, analysis of arterial diseases, and to provide the basis for hemodynamic studies. Within the last two decades accurate models have been fabricated using corrosion casts obtained from cadavers and the lost wax process. Recently, there has been a trend towards replicating the properties of blood vessels more accurately. The use of hydrogels has the potential to achieve this, as it is possible to represent properties such as viscoelasticity, anisotropy, and lubriciousness, all of which have been shown to be present in human blood vessels. The goal of this study is to apply casting methods to a core, which represents similar tortuosity and dimensions to a section of blood vessel, and achieve a low cost model that will represent the dimensional accuracy as well as representing physical properties of blood vessels as accurately as possible. In order to achieve this, poly(vinyl alcohol) (PVOH)/poly (acrylic acid) (PAA) hydrogels were chosen as a material that has the potential to match the properties of blood vessels. The PVOH/PAA hydrogels were prepared using a freeze/thaw processing technique.
Barrier Coating of Flexible Substrates
In the presented project a new coating plant for large area microwave (2.45 GHz) excited low pressure plasma coating with substrate bias has been designed, which allows the coating of foils up to a size of 300 * 300 mm². The objective of the research work is to characterize the effects of the process parameters on the properties of plasma-polymerised coatings, particularly regarding their behaviour under strain. Investigations are carried out using a microwave plasma source and polyethylene terephthalate (PET) as substrate material. As layer forming monomers for plasma polymer barrier coating of the substrates are used.
NEW STRUCTURAL BIOCOMPOSITES FOR CAR APPLICATIONS
Recently advances in research and manufacturing techniques of biocomposites have allowed the car manufactures to use bio-composite in various applications. Biocomposites are fast emerging as viable alternative to traditional materials due to their low cost, lightweight, good mechanical performance and biodegradable properties. ECOSHELL project (Development of new light high-performance environmentally benign composites made of bio-materials and bio-resins for electric car application) proposes to achieve a full bio-composite made of high performance natural resins matrices, resulting in the use of totally natural, environment friendly composites, with enhanced strength and bio-degradability characteristics designed for the electric car.
THE PRODUCTION AND USE OF SUPPORTED NANO-SILVER PARTICLES IN POLYMER SYSTEMS
Silver is a known antimicrobial agent, and has found use in protecting a range of products against bacterial growth. The inherently large surface area of silver nanoparticles allow for a high release rate of silver ions to the environment, where they can be active against a wide range of microbes. Herein, we report a new method of producing silver nanoparticles using a plasma furnace. This process easily allows for the support of the nano-silver material on micron-sized inorganic particles. Silver formed in this manner is more easily dispersed in polymer systems, while maintaining antimicrobial activity against gram positive and negative bacteria.
Proposed UV Rating Method for UV Stabilized Injection Moulding Polyethylene
The European injection moulding market is filled with numerous injection moulding resins that claim resistance to ultraviolet light from outdoor exposure. However, few, if any, have actual comparable data that allows a buyer to distinguish the performance of one resin to another. Likewise, if artificial weathering results are given, how does this relate to actual outdoor performance? Can a relation to outdoor performance be translated to geographic variances in weather? This paper gives a summary of several published artificial ultraviolet exposure studies, some known standards with industry acceptance and how the tests relate to outdoor exposure with a concise experiment between two UV test methods. Finally, a proposal is given of standardized ultraviolet resistant testing for the injection moulding world of polyethylene. This includes estimating outdoor performance with the variances of solar radiation based on geography.
Material Handling and Blending Systems for Molding and Extrusion
Molding and extrusion lines rely on the auxiliary equipment that works with them. This equipment supplies the regrind, resin and additives, cools the process, maintains critical temperatures and even monitors the entire operation. Inadequate process cooling, material handling or size reduction equipment can cause many problems, including the following:; Inadequate process cooling can reduce product output; Poor temperature control can cause product quality issues; Material can be contaminated if not handled and stored properly; The output of the line can be reduced, and even interrupted, if the material is not conveyed to the extruder at the required rate; Product quality will suffer if the material is not blended and metered into the extruder throat at the correct ratios; Excess dust caused by poor size reduction equipment can create processing problems. The following auxiliary equipment is crucial to any molding or extrusion process, and needs to be taken into consideration:; Cooling tower system; Chilled water system; Temperature control units; Bulk storage of the raw material; Material conveying system; Blending and feeding equipment; Crystallizing and drying systems; Size reduction systems. This paper will focus on material handling and blending systems – the other areas will be discussed at a later time.
STRAIN HARDENING: AN ELEGANT AND FAST METHOD TO PREDICT THE SLOW CRACK GROWTH BEHAVIOR OF HDPE PIPE MATERIALS
Resistance to slow crack growth is an important material property of polyethylene which determines the application lifetime, especially for utility pipe applications. Usually, the slow crack growth resistance of materials is accessed by time consuming testing methods such as NPT, FNCT, PENT, etc. These methods require often the use of notched samples, the use of specific fluids (e.g. detergents) and elevated temperatures. Here we present the outline and validation of an elegant method to predict slow crack growth resistance in materials in a simple, accurate and fast way. The resistance to slow crack growth is predicted from a simple tensile measurement at 80 C. It will be shown that the slope of the stress-strain curve above the natural draw ratio (i.e. the strain hardening regime) correlates very well with the results obtained by the full notch creep test (FNCT), Notch Pipe Test (NPT) and the stress intensity ranking of the cyclic loaded Cracked Round Bar test (CRB) of the same materials. This strain hardening method is elegant in that it does not require notched specimen and/or detergents. Besides the advantage that the method is easy to implement in laboratories, its main advantage is the dramatic decrease of measurement times from thousands of hours to only a few. This method is very suitable in the development of new grades, but also very valuable as a batch release test for both resin suppliers and pipe converters.
TOUCHNESS OF MICROCELLULLAR POLYCARBONATE FOAMS AND IT’S DEPENCE OF THE TEMPERATURE
This investigation analyses the notched impact strength of microcellular polycarbonate which was produced by injection molding using physical blowing agents. By varying different processing parameters, such as blowing agent concentration or the injection velocity, injection moulded plates were produced and characterized with regard to morphology and the Charpy notched impact strength. A temperature-dependent analysis concerning the correlation between the foam morphology and the notched impact strength was carried out. Additionally investigations were performed to find out if the failure mechanisms, which occur at low temperatures, also function the same when exposed to temperatures higher than 80°C.
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