Würzburg, Germany
Würzburg, Germany

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Kraus E.,German Plastics Center
Journal of Applied Polymer Science | Year: 2016

We report on the surface energy characteristics of composite materials based on low-density polyethylene with addition of bentonite and organic clay. Investigated were the surface free energy, its components and parameters by wetting methods according to Berger, spatial method, and method of nonlinear systems. The determined characteristics were carried out by the selective wetting conditions for the individual constituents of the composition, including the clay powder. The thermal, mechanical, and morphological properties of obtained composites were investigated. The possibility for predicting the surface properties of composite materials based on component-wise analysis was demonstrated. © 2016 Wiley Periodicals, Inc.


Stoehr N.,German Plastics Center | Baudrit B.,German Plastics Center | Haberstroh E.,RWTH Aachen | Nase M.,Hof University of Applied Sciences | And 2 more authors.
Journal of Applied Polymer Science | Year: 2014

The objectives of the presented work were to investigate films based on polylactic acid (PLA) and polyethylene glycol (PEG) in order to improve ductility and weldability of PLA films. The effect of plasticizer amount on the thermal, rheological, and mechanical properties of PLA plasticized films was investigated. The PEG content does affect the glass transition and the cold crystallization temperature of PLA in blends, while the melting temperature was not affected by the addition of PEG. The complex viscosity of the neat PLA granules and of plasticized films showed strong temperature and angular velocity dependence. The Young's modulus and tensile strength of plasticized films were improved with increasing plasticizer concentration, while the elongation at break stays rather constant. Plasticized PLA films were furthermore heat welded. These investigations showed that plasticized PLA films can be welded by heat welding. The obtained weld strength is strongly depending on the PEG amount as well as on selected welding parameters. © 2014 Wiley Periodicals, Inc.


Zanzinger H.,German Plastics Center | Engelsing K.,German Plastics Center | Hausmann S.,German Plastics Center
10th International Conference on Geosynthetics, ICG 2014 | Year: 2014

Geosynthetics (GSY) and geopipes (GPI) used for landfill applications should have a guaranteed service life of at least 100 years according to the up-to-date landfill directive in Germany. Bearing in mind the high permanent temperatures in landfills, GPIs and GSYs have to have an excellent long-term stability. Almost all GPIs installed in landfills are made of polyethylene (PE). The most common reasons for failure of polyolefins are oxidation, stress cracking and leaching. For this study, GPIs have been taken from three different landfill sites after up to 20 years in service at approximately 40°C and tested in the laboratory. For comparison, two state-of-the-art PE-samples (PE80 and PE100) were tested too. A High Pressure Autoclave Test (HPAT) was used to determine thermo-oxidative and leaching behaviour. Stress crack resistance was determined by Full Notch Creep Test (FNCT) and Strain Hardening Method. The laboratory tests revealed that after only approx. a fifth of the required minimum service life of 100 years, material properties of some samples are by far worse than the requirements for new products. The test results show that a service life of at least 100 years can most likely not be fulfilled by many products, which however did meet the requirements for GPIs for landfill applications in state as delivered, described 20 years ago.


Hochrein T.,German Plastics Center
Journal of Infrared, Millimeter, and Terahertz Waves | Year: 2014

Although a lot of work has already been done under the older terms “far infrared” or “sub-millimeter waves”, the term “terahertz” stands for a novel technique offering many potential applications. The latter term also represents a new generation of systems with the opportunity for coherent, time-resolved detection. In addition to the well-known technical opportunities, an historical examination of Internet usage, as well as the number of publications and patent applications, confirms ongoing interest in this technique. These activities' annual growth rate is between 9 % and 21 %. The geographical distribution shows the center of terahertz activities. A shift from the scientific to more application-oriented research can be observed. We present a survey among worldwide terahertz suppliers with special focus on the European region and the use of terahertz systems in the field of measurement and analytical applications. This reveals the current state of terahertz systems' commercial and geographical availability as well as their costs, target markets, and technical performance. Component cost distribution using the example of an optical pulsed time-domain terahertz system gives an impression of the prevailing cost structure. The predication regarding prospective market development, decreasing system costs and higher availability shows a convenient situation for potential users and interested customers. The causes are primarily increased competition and larger quantities in the future. © 2014, Springer Science+Business Media New York.


Langfeld K.,BAM Federal Institute of Materials Research and Testing | Wilke A.,BAM Federal Institute of Materials Research and Testing | Sut A.,BAM Federal Institute of Materials Research and Testing | Greiser S.,BAM Federal Institute of Materials Research and Testing | And 5 more authors.
Journal of Fire Sciences | Year: 2015

Multicomponent flame retardant systems containing aluminum diethylphosphinate in thermoplastic styrene-ethylene-butylene-styrene elastomers are investigated (oxygen index, UL 94, cone calorimeter, and mechanical testing). Solid-state nuclear magnetic resonance, scanning electron microscopy, and elemental analysis illuminate the interactions in the condensed phase. Thermoplastic styrene-ethylene-butylene-styrene elastomers are a challenge for flame retardancy (peak heat release rate at 50 kW m-2 > 2000 kW m-2, oxygen index = 17.2 vol%, no UL-94 horizontal burn rating) since it burns without residue and with a very high effective heat of combustion. Adding aluminum diethylphosphinate results in efficient flame inhibition and improves the reaction to small flame, but it is less effective in the cone calorimeter. Its efficacy levels off for amounts >∼25 wt%. As the most promising synergistic system, aluminum diethylphosphinate/melamine polyphosphate was identified, combining the main gas action of aluminum diethylphosphinate with condensed phase mechanisms. The protection layer was further improved with several adjuvants. Keeping the overall flame retardant content at 30 wt%, aluminum diethylphosphinate/melamine polyphosphate/titanium dioxide and aluminum diethylphosphinate/melamine polyphosphate/boehmite were the best approaches. An oxygen index of up to 27 vol% was achieved and a horizontal burn rating in UL 94 with immediate self-extinction; peak heat release rate decreased by up to 85% compared to thermoplastic styrene-ethylene-butylene-styrene elastomers, to <300 kW m-2. © The Author(s) 2015.


Kocic N.,German Plastics Center | Lederhofer S.,German Plastics Center | Kretschmer K.,German Plastics Center | Bastian M.,German Plastics Center | Heidemeyer P.,German Plastics Center
Journal of Applied Polymer Science | Year: 2015

The nucleation parameter Kg of filled PP, HDPE, and PA6 is determined through nonisothermal DSC measurements. A novel method is proposed for the determination of the size distribution of critical nuclei, where the most commonly found fraction lpeak∗ was obtained as a peak value. The models are tested at different cooling rates and different filler loadings. Kg varies up to a certain cooling rate and afterwards remains constant. The introduction of talc in PP and HDPE facilitates nucleation and thus reduces Kg. An opposite trend occurs upon the addition of bentonite in PA6. The changes of Kg and lpeak∗ are reflected on sample morphology, as confirmed with SAXS. The ratio between the final crystal thickness and lpeak∗ amounts to approx. 2 and thus agrees well with the one listed in literature. The simple linear correlations of the obtained Kg are established with Young's modulus and yield stress. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41433. © 2014 Wiley Periodicals, Inc.


Feifel S.,Karlsruhe Institute of Technology | Stubs O.,German Plastics Center | Seibert K.,German Plastics Center | Hartl J.,German Plastics Center
European Journal of Wood and Wood Products | Year: 2015

Due to emerging markets for environmentally benign products there is an increasing need for reliable evaluation and transparent information. In this regard, products made of natural materials, like the wood polymer composites (WPC) examined in this study, have to meet particularly high performance levels. To be economically successful they have to prove themselves as products with lower environmental impact compared to alternatives. The required information can be provided by a comparative life cycle assessment (LCA). The purpose of the study at hand is to assess the competitiveness of WPC in environmental terms in its main market of terrace floorings. In this LCA study, two different types of WPC, differing in composition and geometry are compared to two wood decking materials, consisting either of bilinga (tropical wood) or of pressure-impregnated pine (regional wood) with an identical geometry. The functional unit is 1 m2 covered terrace. Process steps identical in all products process chains are excluded. The impact assessment is done with a standardized method for different impact categories. Cumulated energy demand (CED) is shown as separate inventory. Under the assumption of identical lifespans, results show that for all impact categories the terrace made of pine is the most environmentally benign one. Compared to tropical wood WPC is mostly advantageous. WPC terraces may show in particular higher lifespans than wooden terraces and could furthermore be recycled as well. Both would lead to improvements which could result in comparable environmental impacts of WPC and pine wood. © 2015 Springer-Verlag Berlin Heidelberg


Kraus E.,German Plastics Center | Baudrit B.,German Plastics Center | Heidemeyer P.,German Plastics Center | Bastian M.,German Plastics Center | And 2 more authors.
Journal of Adhesion | Year: 2016

We demonstrated an efficient surface pretreatment with excimer laser at 193 nm, which could be successfully used as a surface preparation tool to improve the adhesion and mechanical properties of bonded polymer joints. The effect of the ultraviolet (UV) light can be used both as a method for increasing the specific surface area improving the mechanical adhesion and as a method for activating the polymer surface improving the physical adhesion. Mechanical tests and studies on the failure of bonded polycarbonate (PC) and polyetheretherketone (PEEK) samples showed a significant increase in the quality of bonded connections by using pretreatment with UV laser. As a result of the studies, the bond strength of the PC samples was increased by about 32% using a PB437 UV curing adhesive. By using Loctite 9466 applied to PEEK samples, a strength increase of about 36% was achieved. © 2016 Taylor & Francis


Ashkar R.,German Plastics Center
Welding and Cutting | Year: 2012

Gulf Cooperation Council (GCC) countries are reducing water losses in the region by introducing German welding standards to improve the sustainability of high-density polyethylene (HDPE) piping systems. Many users have shifted from conventional piping systems, such as ductile iron, steel, glass-reinforced plastic, to achieve this objective. SKZ, the German Plastics Center is approaching this problem by providing training, education, testing, and certification according to the internationally acknowledged German welding standards from DVS, German Welding Society and DVGW, German Technical and Scientific Association for Gas and Water. More than 500 specialists have been successfully trained at the SKZ Training Center Middle East which has been functioning from August 2008. Training courses are offered for the welding of HDPE piping systems, along with the welding of polymeric sheets and membranes.


Schober G.,German Plastics Center | Heidemeyer P.,German Plastics Center | Kretschmer K.,German Plastics Center | Bastian M.,German Plastics Center | Hochrein T.,German Plastics Center
AIP Conference Proceedings | Year: 2014

The degree of dispersion of filled polymer compounds is an important quality parameter for various applications. For instance, there is an influence on the chroma in pigment colored plastics or on the mechanical properties of filled or reinforced compounds. Most of the commonly used offline methods are work-intensive and time-consuming. Moreover, they do not allow an all-over process monitoring. In contrast, the ultrasonic technique represents a suitable robust and process-capable inline method. Here, we present inline ultrasonic measurements on polymer melts with a fundamental frequency of 1 MHz during compounding. In order to extend the frequency range we additionally excite the fundamental and the odd harmonics vibrations at 3 and 5 MHz. The measurements were carried out on a compound consisting of polypropylene and calcium carbonate. For the simulation of agglomerates calcium carbonate with a larger particle size was added with various rates. The total filler content was kept constant. The frequency selective analysis shows a linear correlation between the normalized extinction and the rate of agglomerates simulated by the coarser filler. Further experiments with different types of glass beads with a well-defined particle size verify these results. A clear correlation between the normalized extinction and the glass bead size as well as a higher damping with increasing frequency corresponds to the theoretical assumption. In summary the dispersion quality can be monitored inline by the ultrasonic technique. The excitation of the ultrasonic transducer's harmonics generates more information about the material as the usage of the pure harmonic vibration. © 2014 American Institute of Physics.

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