Band 44, Heft 8

Shear thickening fluids (STF) represent stabilized and concentrated colloidal suspensions, wherein hard nanoparticles are dispersed within a liquid medium (polymer). Under the influence of impact forces, they exhibit non-Newtonian behavior, effectively dissipating energy through shear thickening. The optimization of the dispersion medium’s viscosity is critical, as it not only fosters shear thickening but also facilitates proper particle dispersion. This study investigates the impact of graphene oxide (GO) as an additive in STFs, analyzing both static and dynamic rheological properties. STFs were formulated using colloidal silica particles (600 nm) and polyethylene glycol (PEG-200), with varied concentrations of GO particles (0.12–0.5 % w/W). The systems underwent comprehensive analysis concerning steady-state and dynamic-state rheological behavior under diverse conditions. The findings reveal that the inclusion of GO augments both static and dynamic rheological properties, reaching an apex at an optimal concentration of 0.36 % w/W. GO functions as a network builder within the STF, interacting with the existing particle network to create a more robust and interconnected structure. These enhanced properties underscore the potential of the synthesized STF for applications requiring impact resistance.

Engineering plastics are increasingly used for gearing systems, such as in the automotive sector, e-mobility sector, and household appliances. The basic task of the gearing system is to efficiently transfer power from the source to the application user. The use of engineering plastics for gearing applications is conditioned by the lack of tribological characteristics of material pairs which influence on fatigue and wear behaviour of the whole gearing system. The paper presents testing of the steel/Polyamide 66-gear by determining fatigue life in an infinite area, considering high precision optical measurements in the range of micro-meter accuracy of abrasion flank wear together with surface temperature in contact, providing an important database for engineers about material suitability for appropriate mechanical systems. Observing the results, gear flank wear of PA66 HT is directly proportional to the meshing temperature and torque. Thermal melting is a characteristic failure mode of the polymer gears which are exposed to higher load levels. In the middle torques, the dominant failure mode is flank fracture known as pitch point fracture. The greater impact of the gear wear mechanism occurs at lower torques where initial crack propagation starts at the pitch point and ends in the tooth root area.

Osteomyelitis is a complex infectious disease caused by bacterial infection, which has always been a difficult problem for clinical orthopedic surgeons. Although the traditional methods are effective in treating osteomyelitis, the heavy use of antibiotics and surgical treatment cause serious side effects and lead to bone loss and healing difficulties after surgery. Chitosan (CS), a natural polymer material, is a deacetylated derivative of chitin, which has good biodegradability, antibacterial, and osteogenic properties, and has been widely used in the treatment of osteomyelitis. In this review, the recent research progress in the application of CS based composites such as micro-nano drug delivery carriers, hydrogels, coating materials, and bone tissue engineering scaffolds for the treatment of osteomyelitis is summarized, in order to provide certain experimental and theoretical support for the development of CS based composites.

Phase inversion involves in a complex process due to numerous factors affecting the membrane formation. Among them, polymer chain entanglement from polymeric membrane materials plays a critical role in regulating membrane structure and is still worth further exploration. Herein, a series of methacrylate copolymers with different contents of poly(ethylene glycol) methacrylate (PEGMA) were designed and synthesized, and ultrafiltration membranes cast from these copolymers were systematically investigated regarding structural evolution and filtration performance. Surface zeta potential of membranes gradually transformed from positive to negative with the increasing PEGMA content due to nonsolvent-induced surface migration of element oxygen, and meanwhile the transformation from finger-like pore structure to sponge-like pore structure in the support layer was observed, which could be attributed to chain entanglement of the PEGMA-rich copolymer. Filtration experiments indicated that sponge-like membranes possessed better separation effect of Victoria blue B compared with finger-like membranes, and the optimized mPP40-15 % showed a retention rate of 99.55 % and permeance of 110.26 L m −2  h −1  bar −1 and displayed good selective separation of dye/salt mixture. Besides, sponge-like membranes also exhibited easy regeneration, anti-fouling property and filtration stability. This work will provide guidance for modulating membrane structure and offer an alternative material for membrane separation in handling dye wastewater.

This study examined the effects of silane-modified polyimide polymer (PIS) on cement mortar. The PIS was added to replace cement in a specified ratio. Obtained results revealed that the PIS caused retardation on setting time, and accelerated UPV mostly by encapsulating unhydrated cement particles, filling pores, or reacting with C–S–H and Ca(OH) 2 with shifting to Si–O vibrations. SEM results showed a good compact interface without forming considerable agglomeration and voids on the microstructure, and this improved flexural and compressive strength properties. In conclusion, silane-modified polyimide as an admixture or cement replacement can be recommended for construction industries to enhance the properties of cement mortar.

Roll coating plays a significant role in various coating industries such as magnetic records, wallpapers, wrapping, adhesive tapes, books and magazines, photographic and plastic films. The thin layer coating of a magnetohydrodynamic (MHD) viscous hybrid nanofluid by passing through the space between two co-rotating rolls has been studied in an isothermal and incompressible analysis. The governing equation of mass and momentum are obtained then dimensionless using lubrication approximation theory (LAT). The velocity, pressure gradient, and pressure distribution are determined by the exact solution. Using Simpson’s (3/8) rule for numerical integration, the complex integral is examined. Important engineering parameters including power and roll separating force delivered by the rolls to the fluid are also estimated numerically. Raising the volume fraction of nanoparticles raises the pressure distribution and pressure gradient while having little effect on the velocity profile. It seems that the magnetic field and hybrid nanofluid, both seem very advantageous for the efficient roll coating process, controlling the separation force, power input, and distance between the attachment and separation point.

Excellent oxygen barrier films were prepared by blending very small loadings (<1 wt%) of dihydroxyacetone (DHA), erythritol (ET) or xylitol (XT) in thermoplastic starch (TPS), and/or processing with supercritical carbon dioxide (scCO 2 ) assistance. The minimum oxygen transmission rates (OTR) and all free-volume-hole characteristic (FVH) values of each scCO 2 -processed TPS/sugar alcohol film series are somewhat smaller than those of corresponding TPS/sugar alcohol film series without scCO 2 -assistance, and decrease with the decrease in sugar alcohol’s molecular weight. The minimum OTR values acquired for scCO 2 -processed TPS/DHA and TPS/ET blown films are only 3.6 and 4.3 cm 3 /m 2 ·day·atm, respectively, which meet the demand of high oxygen barrier films having OTR ≦5 cm 3 /m 2 ·day·atm. The longitudinal or transversal tensile strengths acquired for each scCO 2 -processed TPS/sugar alcohol series films are ∼30 % to ∼40 % higher than those of the TPS blown films. Dynamic mechanical relaxations of each TPS/sugar alcohol or scCO 2 -processed TPS/sugar alcohol film series reveal that the sugar alcohols are compatible with TPS, as their sugar alcohol contents are ≤ the corresponding compatibility values. The decreased OTR and FVH values acquired for TPS/sugar alcohol or scCO 2 -processed TPS/sugar alcohol films are most likely due to them being scCO 2 -processed or incorporated with smaller molecular weight of sugar alcohols.