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The bond between polymer fibers and the surrounding cementitious matrix is essential for the development of concrete reinforcement. The single fiber pull-out test (SFPT) is the standard characterization technique for testing the bond strength. However, the different phases of debonding cannot be distinguished by the SFPT. This study investigates the debonding of different polymer fibers from the surrounding cementitious matrix with a modified SFPT and proposes methods to change the SFPT setup to generate more valuable information on the debonding mechanism. The SFPT was equipped with linear variable differential transformers (LVDT), digital image correlation (DIC) and acoustic emission (AE) analysis. The results demonstrate that the modified SFPT allows a better understanding of the different phases of debonding during fiber pull-out. Furthermore, bond strength values calculated by different methods reveal that the chemical bond of the investigated polymers is not different as reported by previous studies. Deformation measurements performed using LVDTs and DIC are suitable measuring techniques to characterize the debonding mechanism in SFPT. A correlation between recorded AE and debonding phases was not found.
Corrosion of steel reinforcements in concrete constructions is a big topic for the building industry. Polymeric materials are a possible alternative due to their ability to withstand corrosion. To replace steel reinforcements, fibers with high mechanical properties and a good bonding ability between fiber and concrete are needed. Today different approaches for concrete reinforcement by polymer fibers have been investigated. The bonding ability of the fibers can be increased by mechanical anchoring, e.g. crimped or embossed fibers, as well as by a chemical bonding between concrete and fiber surface. To realize the requirements of high mechanical properties and a good bonding behavior, a fiber that is drawn from a co-extruded filament shall be produced and tested. The filament owns an innovative core-shell-structure. The core maintains the fiber-stiffness and the tensile strength while the shell allows using another material to affect the bonding behavior of the fiber. This study shows the usage of fibers with differing shell materials to examine their influence on the mechanical properties of the fiber in total and the adhesion abilities to concrete. As core material, an unfilled polypropylene (PP) is used. The shell materials are varied using different polymers e.g. polypropylene or ethylene acrylic acid copolymer, as well as two PP based compounds filled with wood particles and calcium carbonate blended with a maleic anhydride based coupling agent. The mechanical properties of the fibers are tested by fiber tensile tests to compare the younǵs modulus and the tensile strength. The influence of the shell phase on the bonding ability to concrete is evaluated by the interfacial shear strength calculated from single fiber pull-out tests. Microscopy is used to interpret changes before and after pull-out. The results depict incredible positive effects and allow new insights in possible materials for fiber reinforced concrete constructions.
One major problem of a continuous process like plastic extrusion is their incapability to deal with non-local gas pressure. This is an inherent problem because a continuous process has an open end in the feeding port where pressure can escape. In this study a novel feeding system was developed to enable granulate feeding into gas pressurized processes inside a single- or twin-screw extruder. With this apparatus gas pressure can be applied inside the extrusion process. The apparatus separates the pressurized extruder from the dosing equipment that feeds the extruder. It keeps the pressure inside the system while continuously feeding new material into the process. A small-scale prototype was designed for proof-of concept. The small size of the prototype was able to handle small amounts of granulates of around 100 - 200 g/h. An applied gas pressure of 8 bar was achieved. In future optimizations, throughput can be increased and maximum applied gas pressure towards 15-20 bar.
Ein Verfahren zur Einbettung von Dekor-Körpern in eine Silikongummi-Matrix umfasst das Auftragen einer ersten aushärtbaren Polysiloxanzusammensetzung auf eine Grundplatte und Angelieren der ersten Polysiloxanzusammensetzung; das Aufbringen der Dekorkörper auf die angelierte erste Polysiloxanzusammensetzung; das Ausfüllen von Zwischenräumen zwischen den Dekorkörpern mit einer zweiten aushärtbaren Polysiloxanzusammensetzung; und das Aushärten der Polysiloxanzusammensetzungen zu einer transparenten Polysiloxan-Matrix mit darin eingebetteten Dekor-Körpern. Ein weiteres Verfahren zur Einbettung von Dekor-Körpern in eine Silikongummi-Matrix umfasst das Auftragen einer aushärtbaren Polysiloxanzusammensetzung auf eine Grundplatte und Aufbringen der Dekor-Körper vor dem Angelieren der ersten Polysiloxanzusammensetzung; das Einsinkenlassen der aufgebrachten Dekor-Körper in die aushärtende Polysiloxanzusammensetzung derart, dass die aufgebrachten Dekor-Körper von der Polysiloxanzusammensetzung vollständig umschlossen werden; und das Aushärten der Polysiloxanzusammensetzungen zu einer transparenten Polysiloxan-Matrix mit den darin eingebetteten Dekor-Körpern derart, dass eine Mehrzahl der eingebetteten Dekor-Körper von der Polysiloxanzusammensetzung vollständig umschlossen bleibt.
Beschichtung für ein medizinisches Instrument, das nach seinem Einführen in einen menschlichen oder tierischen Körper mit dessen Körperflüssigkeit in Kontakt gelangt, umfassend eine Materialzusammensetzung, die wenigstens ein Phosphorylcholin umfassendes Polymer enthält, dadurch gekennzeichnet, dass die Materialzusammensetzung für ein medizinisches Instrument, das auf seiner Oberfläche Polyurethan enthält oder das daraus gänzlich besteht, eine auf das medizinische Instrument aufbringbare Haftungsvernetzungsschicht aus einem chemischen Haftvermittler und einem mit diesem vernetzten Alkohol, mindestens einem zweiwertigen Alkohol mit zwei primären OHGruppen, und das wenigstens eine Phosphorylcholin umfassende Polymer enthält, welches auf der Haftungsvernetzungsschicht als gesonderte Schicht aufgebracht sowie auf dieser und gegebenenfalls mit dieser vernetzt ist.
Die Erfindung betrifft eine Brustprothese, die aus einem schalenförmigen Körper aus einem weich-elastisch eingestellten Kunststoff besteht, der in Kunststoffolien zu einer oder mehreren Kammern eingeschweißt ist. Erfindungsgemäß wird das Füllmaterial mit polymeren Farbstoffen eingefärbt. Die Erfindung betrifft weiterhin ein Verfahren zum Färben von Brustprothesen.
A crucial problem in concrete engineering is the corrosion of steel reinforcements. Polymer fibers as alternative reinforcement material can prevent corrosion; however, high adhesion to concrete and good fiber mechanics are necessary for polymers to be considered as an alternative reinforcement. This study tested different thermoplastic polymer materials to evaluate their level of adhesion to concrete. The adhesion properties of different self‐drawn polymer fibers were analyzed by extracting the fibers from concrete using single fiber pull‐out test (SFPT). To determine the adhesion mechanism, different polymer properties were analyzed and correlated to SFPT. Strong evidence was found that the fibers mechanical properties correlate with SFPT. Roughening the fiber surface increases the SFPT results significantly. While highly polar materials can support the adhesion process, a clear correlation could not be found. This study identifies high stiffness and roughness as the crucial properties of polymer fibers used in concrete engineering. If these factors can be engineered into the fiber, polymer fibers can present an alternative to steel in concrete reinforcement.