Stiff-Elongated Balance of PLA-Based Polymer Blends

In this study, polymer blends with a mechanical property balance based on poly(lactic acid) (PLA), stiff polymer, and elongated polymer were developed. First, the binary blends PLA-elongated polymer [ethyl vinyl acetate (EVA) or polyethylene], or PLA-stiff polymer [polystyrene or poly(styrene-co-methyl methacrylate) (SMMA)] blends were studied using dynamic mechanic analysis (DMA) and analyzed using Minitab statistical software to determine the factors influencing the elongation or stiffness of the blends. Then, ternary blends such as elongation-poly(lactic acid)-stiff, were made from the binary blends that presented optimal performance. In addition, three blends [EVA–PLA–SMMA (EPS)] were elaborated by studying the mixing time (5, 15, and 15 min) and the added time of the SMMA (0, 0, and 10 min). Specifically, the mixing time for EPS 1, EPS 2, and EPS 3 is 5 min, 15 min, and 15 min (first EVA + PLA for 10 min, plus 5 min PLA-EVA and SMMA), respectively. Mechanical, thermal, rheological, and morphological properties of the blends were studied. According to DMA, the results show an increase in elongation at break (εb) and do not decrease the elastic module of poly(lactic acid). Nevertheless, EPS 3 excels in all properties, with an εb of 67% and modulus of elasticity similar to PLA. SMMA has a significant role as a compatibilizing agent and improves PLA processability.

Investigation of Mechanical and Magnetic Properties of Co-Based Amorphous Powders Obtained by Atomization

Properties of Co-based alloys with high Glass Forming Ability (GFA) in the form of powder are still not widely known. However, powders of high GFA alloys are often used for the development of bulk metallic glasses by additive manufacturing. In this work Co47.6B21.9Fe20.4Si5.1Nb5% at. and Co42B26.5Fe20Ta5.5Si5Cu1% at. were developed by gas-atomization. Obtained powders in size 50–80 µm were annealed at Tg and Tx of each alloy. Then SEM observation, EDS analyses, differential thermal analysis, X-ray diffraction, nanoindentation, Mössbauer, and magnetic properties research was carried out for as-atomized and annealed states. The gas atomization method proved to be an efficient method for manufacturing Co-based metallic glasses. The obtained powder particles were spherical and chemically homogeneous. Annealing resulted in an increase of mechanical properties such as hardness and the elastic module of Co47.6B21.9Fe20.4Si5.1Nb5% at and Co42B26.5Fe20Ta5.5Si5Cu1%, which was caused by crystallization. The magnetic study shows that Co47.6B21.9Fe20.4Si5.1Nb5 and Co42B26.5Fe20Ta5.5Si5Cu1 are soft magnetic and semi-hard magnetic materials, respectively.

Investigations on the Influence of Annealing on Microstructure and Mechanical Properties of Electrodeposited Ni-Mo and Ni-Mo-W Alloy Coatings

Ni-Mo and Ni-Mo-W coatings were electrodeposited on a stainless steel sheet, and then were annealed at 200, 400, and 600 °C. The effect of annealing heat treatment on the microstructure of Ni-Mo and Ni-Mo-W electrodepositions, their nano-hardness, and tribological properties were investigated. It was revealed that the average crystalline are refined and phase separation are promoted with formation of Mo-W related intermetallic precipitates at temperature exceed 400 °C on account of the co-existence of Mo-W elements within Ni-Mo-W coatings. Annealing heat treatment leads to hardening, and the hardness and elastic module increase significantly. The grain boundary (GB) relaxation and hard precipitated intermetallic particles are responsible for the annealing-induced hardening for ≤400 °C annealed and 600 °C annealed Ni-Mo-W coatings, respectively. In addition, both adhesive wear and abrasive wear are observed for coatings, and abrasive wear becomes predominant when annealing temperature up to 600 °C. The wear resistance of coatings is improved eventually by formation of a mixture of lubricated oxides upon annealing at 600 °C and the enhancement of H/E ratio for ≤400 °C annealed Ni-Mo-W coatings.

Ultra-Structural Characteristics of Aloe vera-Based Nanofibers as MRSA-Phage Nanocarriers

This study investigates the mechanical, thermodynamic, and morphological changes and surface topography of Aloe vera (AV)-based nanofibers as the nanocarriers of methicillin-resistant Staphylococcus aureus (MRSA). After making the AV-based solutions, the nanofibers were made by electrospinning device and the topography and roughness coefficient of the nanofibers were obtained by atomic force microscopy (AFM). A tensile test was used to evaluate the mechanical properties of the nanofibers and simultaneous thermal analysis (STA) was used for thermal testing. The results of AFM showed nanofiber deformation in the combination of AV-phages. It was observed in the mechanical test results that with the addition of phage to AV-nanofibers, although the elastic module decreased, the elongation percentage increased, with high resistance to stretching. Also, the thermal analysis results were such that the addition of phage to AV-nanofibers increased the thermal stability of the nanofibers. The addition of MRSA phages to the Aloe vera nanofibers was increased thermal stability and the percentage of elongation of the nanofibers. The combination of AV-phage nanofibers creates a new carrying capacity at the nanofiber level to be a candidate for wound dressing as a therapeutic agent.

Evaluation of torque moment in esthetic brackets from bendable alloy wires

ABSTRACT Objectives To examine the torque moment that occurs between esthetic brackets and bendable alloy (stainless steel [SS], titanium-molybdenum [Ti-Mo], and titanium-niobium [Ti-Nb]) wires. Materials and Methods This study examined ceramic (CR), zirconium oxide (ZC), polycarbonate (PC), and conventional metallic brackets (MT) (upper, 0.018-inch and 0.022-inch slots) combined with SS, Ti-Mo, and Ti-Nb wires using elastic module ligation. The torque moments delivered by various wire and bracket combinations were measured using a torque gauge apparatus. The wire torque angles at 5–40° were examined. Results The torque value increased in the order of CR, ZC, MT, and PC brackets for both 0.018-inch and 0.022-inch slots. The fracture points of the CR and ZC brackets combined with SS and Ti-Mo wires were approximately more than 30° and 35°, respectively. No fracture points were detected in the combination of ZC brackets and Ti-Nb wires. Conclusions The current study identified the material characteristics of CR, ZR, and PC brackets during torque tooth movements. The present results demonstrate a characteristic combined effect between different esthetic brackets and bendable alloy wires.

Strain, natural frequency, damping coefficient and elastic modulus of mortar beams determined by fiber Bragg grating (FBG) sensors

Structural health monitoring can detect anomalies in time, allowing the implementation of more efficient maintenance and repair actions in special engineering structures. An alternative in the monitoring and evaluation of structures in civil engineering is the use of optical fibers inscribed with Bragg gratings (FBG or Fiber Bragg Grating). This paper aims to compare available techniques to estimate the elastic module of cementitious composites, as well as contribute to the application of optical fiber sensors in the monitoring of strain, natural vibration frequency, damping coefficient and elastic modulus of mortar beams. The FBG sensors manufactured and calibrated by the authors presented a good precision for measuring those parameters in mortar samples. The results show that FBG sensors and strain gauge sensors present a similar result for strain and estimation of the elastic module (static and dynamic), therefore, bare FBGs could be further investigated for non-destructive testing.

Diagnostic assessment of an impact of static and dynamic vehicle loads on covering of roadway

The article presents diagnostic possibilities for testing covering of roadway through dynamic and static loading units. The article presents features, advantages and principal characteristics of the equipment: die unit, Dina-3M, UDN-NK, Dynatest unit. The main parameters of the dynamic impact units. The article also presents results of tests by dynamic and static loading, defines «flexural bowls», elastic module and the coefficients of reduction of the elastic modulus to the static modulus.

ANALYSIS OF THE MECHANISM OF REINFORCEMENT OF THE ROAD STRUCTURE WITH A UNLOADING SECTION

The problem posed is about the mechanism for reinforcing the road structure with a slab with an unloading cut. The reasons for the appearance of transverse cracks in the upper layer of the road surface in winter have been investigated. Solvable equations are formulated, their finite element analogs are constructed. Cases of loads at different values of elastic module and plate sizes are considered. At low temperatures, the upper layers of the road try to reduce their length, however, due to their almost infinite length, they cannot do this and transverse disordered cracks appear in the upper layer, which, due to the action of transport loads and the forces of frozen water, lead to further delamination and destruction of the road structure. Therefore, the introduction into another layer of a reinforced slab made of a stiffer and more durable material that is capable of absorbing increased stresses allows the upper layer to shorten and lengthen freely and removes the arising longitudinal thermal stress. Due to the fact that this plate is located in the zone of stress concentration, these stresses become less dangerous. KEYWORDS: AUTOMOBILE ROAD, ASPHALT-CONCRETE COATING, LOADING RISK, TRACKED TRACKS, TRANSPORT LOADS, STRESS FIELD, THERMO ELASTIC STATE

Obtaining functional gradient coatings based on Al2O3 by detonation spraying

The article deals with the phase composition and hardness of Al2O3 coatings obtained by detonation spraying. It was found that a decrease in the delay time between shots is leading to an increase in the hardness and elastic module of Al2O3 coatings. It was found based on X-ray diffraction analysis that the main reason for the increase in hardness with a decreasing in the delay time between shots is associated with increases in the volume fraction of α- Al2O3 phase. A high content of the more ductile γ-Al2O3 phase at the substrate-coating interface leads to an increase in adhesion characteristics, and a high content of the α-Al2O3 phase on the coating surface provides high hardness and wear resistance. The studies of X-ray diffraction presented that the highest phase content is achieved when the coatings are formed with a delay time between shots of 0.25 s. It was found that increase in the volume fraction of the α-Al2O3 phase is caused by the secondary recrystallization γ → α, which occurs due to the heating of particles during coating formation, i.e. due to increase in temperature above 1100 ºС in single spots of the coating when they are put each other

Degradation Features Of Polyethylene And Gelatin Compositions

In this work, biodegradable properties of gelatin and polyethylene compositions, in addition to, influence of ultra violet radiation and peroxide groups were studied. In order to obtain thermoplastic gelatin water and glycerin were used as a plasticizer. For polyethylene/gelatin blends, to provide compatibility polyethylene functionalized with maleic anhydride. It was found that as gelatin content increases, biodegradation also grows while mechanical properties (elastic module and yield strength) decrease.