Absolute measurement of the ^{1}S_{0} − ^{3}P_{0} clock transition in neutral ^{88}Sr over the 330 km-long stabilized fibre optic link

We report a stability below $7\times 10{}^{-17}$ of two independent optical lattice clocks operating with bosonic ${}^{88}$Sr isotope. The value (429228066418008.3(1.9)${}_{syst}$(0.9)${}_{stat}$~Hz) of the absolute frequency of the ${}^{1}S_{0}$ - ${}^{3}P_{0}$ transition was measured with an optical frequency comb referenced to the local representation of the UTC by the 330 km-long stabilized fibre optical link. The result was verified by series of measurements on two independent optical lattice clocks and agrees with recommendation of Bureau International des Poids et Mesures

The effect of short polystyrene brushes grafted from graphene oxide on the behavior of miscible PMMA/SAN blends

A new concept of utilization of particle-polymer hybrids as multifunctional additives for polymer blends was introduced in this study. Graphene oxide particles with short densely grafted polystyrene brushes (GO-g-PS) were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP). Melt rheology studies revealed that GO-g-PS suppressed the phase separation of miscible poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) (PMMA/SAN) blends. The studies suggested specific interactions of GO-g-PS with the PMMA phase and this was confirmed based on calculations of activation energies of segmental relaxations by broadband dielectric spectroscopy (BDS). These unusual interactions of GO-g-PS with PMMA phase were assigned to the specific and precise architecture of the GO-g-PS particles as well as chemical nature of PS polymer brushes. The short chains of PMMA and PS provide miscibility originating from UCST behavior of PMMA/PS blend of short polymer chains. Additionally, BDS also revealed improved charge transport in PMMA/SAN blend in presence of GO-g-PS hybrid. © 2020 Elsevier LtdAction Austria - Slovakia, Co-operation in Science and Education program [56337]; National Science Centre, PolandNational Science Center, PolandNational Science Centre, Poland [UMO-2016/23/P/ST5/02131]; European Unions' Horizon 2020 research and innovation program under Marie Sklodowska-Curie grant [665778]; Research & Innovation Operational Programme - ERDF [313021T081]; project VEGAVedecka grantova agentura MSVVaS SR a SAV (VEGA) [2/0129/19]; Technology Agency of the CR [TN01000008]; Ministry of Education, Youth and Sports of the Czech Republic - DKRVO [RP/CPS/2020/003

Natural Rubber Composites Filled with Crop Residues as an Alternative to Vulcanizates with Common Fillers

This present study is focused on exploring the possibility of using agricultural waste in the form of cereal straw as an active filler of biocomposites. The effect of lignocellulosic filler addition on the multifunctional properties of natural rubber composites was investigated. The results were compared with the properties of vulcanizates containing commonly used reinforcements in elastomer technology (carbon black, silica, chalk, talc). Rubber mixtures filled with straw showed the highest torque increase during rheometric measurements, which indirectly indicated a high degree of crosslinking and hardness of composites. It was found that the effect of straw addition on vulcanization time of elastomer blends was comparable with the results obtained for other conventional fillers. Moreover, the results confirmed that novel composites based on natural rubber filled with crop residues were attractive materials owing to their capacity for the formation of “structure” in combination with a good impact on reinforcement. Vulcanizates with the addition of straw showed the best barrier properties and resistance to thermo-oxidative aging from all tested samples. Furthermore, straw-based composites demonstrated that cereal straw waste could be used as an alternative, biodegradable and eco-friendly reinforcement of natural rubber composites

Thermoplastic Elastomer Biocomposites Filled with Cereal Straw Fibers Obtained with Different Processing Methods—Preparation and Properties

This work is focused on thermoplastic elastomers composites (TPEs) reinforced with straw. Crop waste with different particle size was used as a filler of ethylene-octene rubber (EOR). Application of cheap and renewable natural fiber like straw into a TPE medium is not fully recognized and explored. The effect of fiber orientation induced by two processing techniques on the different mechanical properties of composites was investigated. Microscopic images were used to present the tested straw fractions and observe the arrangement and dispersion of fibers in the polymer matrix. It was found that the usage of an injection molding process allowed for the forming of a more homogenous dispersion of short fiber particles in the elastomer matrix. An oriented straw filler and polymer chains resulted in the improved mechanical strength of the whole system as evidenced by the obtained values of tensile strength almost two times higher for injected composites. In addition, all composites showed very good resistance to thermo-oxidative aging, where the aging factor oscillated within the limits of one, regardless of the processing method and the amount of bioadditive used. On the other hand, vulcanized composites were characterized by greater tear resistance, for which Fmit values increased by up to 600% compared to the reference sample

Reinforced, Extruded, Isotropic Magnetic Elastomer Composites: Fabrication and Properties

The study involves the development of isotropic magnetorheological elastomer composites (i-MREs) with improved mechanical properties, their preparations, and properties characterizations. The novelty of the research is the use of extrusion process in the preparation of composites containing two different fillers: carbonyl iron powder (CIP) as magnetic filler and carbon black (FEF, N550) as reinforcing one. So far, the process of extrusion has been used to prepare magnetic composites without filler that improve mechanical properties. It is worth mentioning that the polymer matrix (ethylene-octene copolymer, EOR) offers excellent performance in extrusion applications. In this research, two methods of magnetic composites preparation were reported: traditional, during two-roll mill, and a new one using extrusion process. It was found that the usage of new processing technology allowed forming more homogenous dispersion of particles in elastomer matrix and oriented polymer chains, resulting in an improved rheometric characteristic, increased crosslink density, and decrease of the storage modulus (Payne effect). Based on both static/dynamic mechanical properties and damping properties under the influence of compression stress, the positive influence of extrusion process on material characteristics was confirmed. Moreover, all composites proved very good magnetic properties and resistance to thermooxidative ageing

Thermoplastic Elastomeric Composites Filled with Lignocellulose Bioadditives. Part 1: Morphology, Processing, Thermal and Rheological Properties

Thermoplastic elastomer blends based on natural rubber (NR) and ethylene-vinyl acetate copolymer (EVA) with different weight ratios (30, 40, 50, 60 and 70 parts per hundred rubber (phr) of NR) and 10, 20 and 30 phr of straw were prepared and characterized. Current environmental problems were the motivation to produce this type of system, namely: the need to replace plastics at least partly with natural materials; increasing the amount of renewable raw materials and managing excess straw production. When using this bioadditive in traditional materials, the high processing temperature can be problematic, leading to the degradation of straw fibers. The solution can be polymer mixtures that are prepared at significantly lower temperatures. Scanning electron microscope (SEM) imaging was used to investigate the particle size of fibers and phase morphology of composites. Moreover, determination of the thermal properties of the filler and composites showed that the processing temperature used in the production of NR/EVA blends reduces the risk of degradation of the natural filler. Differential scanning calorimetry (DSC) was used to determine the thermal behavior of the filled composites. Finally, rheological tests of materials allow the determination of optimal processing parameters and properties of materials in dynamic conditions. The proposed blends exhibit elastic properties, and due to the lack of chemical cross-linking they can be processed and recycled like thermoplastics. In addition, they offset the disadvantages and combine the advantages of natural rubber and ethylene-vinyl acetate copolymer in the form of thermoplastic elastomeric biocomposites