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- ItemProcess-morphology-property-relationships of titania-filled polypropylene nanocomposites(India : Integrated Publishing Association, 2015) Schlarb, Alois K.; Lin, Leyu; Suwitaningsih, Dwi N.; Suksut, BunchaAlthough the research and development of nanocomposites for almost a decade focused on structural properties, these properties remained until today far below expectations, which were forecast at the beginning of the new millennium. However, even if it is well known that the processing history has a major impact on the structure and properties of final components, this aspect was not subject of intensive research in the past. The talk focuses on the role of the manufacturing sequence on the morphology and properties of polypropylene based nanocomposites. In general it can be stated that the incorporation of nano-sized TiO2-fillers improves the some mechanical properties of the resulting nanocomposites as long as the production enables a good dispersion and distribution of the nanofiller agglomerates. However, with increasing filler loading, the morphology of injection molded parts changes: The size of the spherulites and the degree of crystallinity decreases while the crystallization/solidification proceeds faster. Simultaneously a slight improvement in the mechanical performance up to a certain filler loading can be found. However, improved mechanical properties of the nanocomposites in the final component cannot be exploited if its production in a subsequent welding step is required. The reason for the decrease in the mechanical properties is the decrease in the viscosity by the addition of the fillers, and thereby caused extreme flow processes and subsequent orientation of the fillers as well as the weakening of the filler/matrix-interphase in the welding zone. In summary, it can be observed that nanocomposites increasingly offer great opportunities for applications where single-component materials reach their limits. The key to success is the processing. Therefore it is of crucial importance that the total manufacturing history is understood and controlled. Only then it is possible to sustainably exploit the potential of polymer nanocomposites in the application.
- ItemSelf-Healing Iron Oxide Polyelectrolyte Nanocomposites: Influence of Particle Agglomeration and Water on Mechanical Properties(Basel : MDPI, 2023) Oberhausen, Bastian; Plohl, Ajda; Niebuur, Bart-Jan; Diebels, Stefan; Jung, Anne; Kraus, Tobias; Kickelbick, GuidoSelf-healing nanocomposites can be generated by organic functionalization of inorganic nanoparticles and complementary functionalization of the polymer matrix, allowing reversible interactions between the two components. Here, we report on self-healing nanocomposites based on ionic interactions between anionic copolymers consisting of di(ethylene glycol) methyl ether methacrylate, sodium 4-(methacryloyloxy)butan-1-sulfonate, and cationically functionalized iron oxide nanoparticles. The materials exhibited hygroscopic behavior. At water contents < 6%, the shear modulus was reduced by up to 90%. The nanoparticle concentration was identified as a second factor strongly influencing the mechanical properties of the materials. Backscattered scanning electron microscopy and small-angle X-ray scattering measurements showed the formation of agglomerates in the size range of 100 nm to a few µm in diameter, independent of concentration, resulting in the disordering of the semi-crystalline ionic polymer blocks. These effects resulted in an increase in the shear modulus of the composite from 3.7 MPa to 5.6 MPa, 6.3 Mpa, and 7.5 MPa for 2, 10, and 20 wt% particles, respectively. Temperature-induced self-healing was possible for all composites investigated. However, only 36% of the maximum stress could be recovered in systems with a low nanoparticle content, whereas the original properties were largely restored (>85%) at higher particle contents.