Processing Fiber-Reinforced Polymers: Specific Wear Phenomena Caused by Filler Materials

Fiber-reinforced polymers allow for the implementation of plastic materials in structural components. However, increasing incorporation of fibers up to 50 wt% causes accelerated component wear in injection molding machines. In particular, the barrel and screw in the compression zone suffer from increased wear. The abrasive fibers of the compacted polymer pellets in the solid bed protrude from the surfaces of the resin having an abrasive, brush-like behavior. A modified pin-on-disk testing system with specially designed polymer pins was used to emulate the described tribological system in laboratory scale. Through varying contact pressure, temperature, and surface modifications of the counterparts (blank or coated powder-metallurgical steel), abrasive wear as observed in industrial-sized extruder screws could be successfully simulated on a laboratory-scale testing system. Detailed investigations of the pins and disks highlighted that the glass fibers plow and cut the surface leading to abrasion as observed in the real field application. Temperature has been proven to be the most decisive driving force. Surface modifications such as protective physical vapor-deposited CrN coatings are effective against abrasive wear, clearly outperforming untreated steels. The presented pin-on-disk-test setup will improve screening of materials for extruders, thus enhancing the durability of injection molding machines. POLYM. ENG. SCI., 60:78–85, 2020. © 2019 Society of Plastics Engineers     

X-ray line profile analysis—An ideal tool to quantify structural parameters of nanomaterials

For a long time the shift and broadening of Bragg profiles have been used to evaluate internal stresses and coherent domain sizes, i.e. the smallest crystalline region without lattice defects. Modern technology provides both enhanced detector resolution and high brilliance x-ray sources thus allowing measurements of x-ray peaks with a high resolution in space and time. In parallel to the hardware, also diffraction theories have been substantially improved so that the shape of Bragg profiles can be quantitatively evaluated not only in terms of the crystallite size and its distribution, but also in terms of the density, type and arrangement of dislocations, twins and stacking faults. Thus state-of-the-art x-ray line profile analysis enables the thorough characterization especially of nanostructured materials which also contain lattice defects. The method can be used also to prove the existence of dislocations in crystalline materials. Examples of nanostructured metals, polymers and even molecular crystals like fullerenes are given.     

居德布兰河谷旅游项目—河边桑拿

河边桑拿位于一条美丽的河边,可以全景观赏远山的景色。它建在菲多斯景观酒店附近,供酒店的客人使用。桑拿房有一面玻璃墙,朝向景区。建筑物建在地形中,除玻璃墙外,四周用青草覆盖。     

Erfassen von Ursache-Wirkungs-Beziehungen in Flusslandschaften: Vermittlung von Systemwissen in Schulen als Beitrag für ein nachhaltiges Flussgebietsmanagement

A scientific understanding of the processes at work in river landscapes represents an important basis for including the local populace in effective and sustainable river landscape management. By conveying system-based knowledge to students, these future inhabitants and users of river landscapes will be better able to recognize contexts and connections, understand project-related decisions and policies, and support sustainable planning efforts. As such, in October 2012 the Austrian Federal Ministry for Science and Research started the “FlussAu:WOW!” project, part of the “Sparkling Science” research program. In the project, scientists work together with the students from two upper-level high-school classes over a period of two years, investigating research questions on river landscape management. The scientific goal of the project is to create a set of indicators to represent the functionality of floodplains. In the first school year, the researchers worked on key questions together with the students in workshops, performed field surveys and analyzed the results of fieldwork. In the subsequent discussions, the researchers constantly pointed out the complex interrelations at work in river-floodplain systems. Students’ knowledge was evaluated in pre-project and post-project tests. The analysis of the pre-tests revealed major knowledge gaps on questions concerning river landscape management, e.g. on factors that place major pressures on these regions. A comparison between the pre- and post-tests confirmed a significant improvement in the students’ factual knowledge after the first year; however, the post-project tests only showed a coupling of that knowledge with a recognition of cause-and-effect relations in sporadic cases. Beyond factual knowledge, it is above all a grasp of the interconnections between individual system elements that serves as an essential basis of education. Interactive, modern approaches are critical to conveying interdisciplinary knowledge. As part of the “FlussAu:WOW!” project, in the second school year system-based learning is implemented with the help of innovative modeling and simulation software. In both the pre- and post-tests, questions on the students’ interests revealed a high level of motivation to join in the research, and considerable interest in questions concerning nature and the environment. As a result, by the end of the first school year the cooperation between researchers, educators and students had already made a valuable contribution to sustainable river landscape management.     

Microhardness of quenched and annealed isotactic polypropylene

The influence of molecular weight on the microhardness of quenched and subsequently annealed isotactic PP is shown. A clear dependence of microhardness on molecular weight and annealing temperature was detected. Even in the quenched state, where it was difficult to detect morphological differences between the materials, microhardness shows differences. In all states, quenched and annealed, the lower molecular weight samples have the higher hardness values. Up to an annealing temperature of 70 °C the hardness increases only slightly in all samples, above 80 °C a more pronounced increase was observed. For the microhardness of the samples annealed at 140 °C the ratio of the amorphous to the crystalline length is the dominating morphological parameter.