Study of polymer-based adhesive mortar with higher durability

This paper deals with the study and development of polymer-based adhesive with high filling ratio of secondary raw materials and waste materials. The goal of this paper is to develop adhesive mortar with the highest filling rate of secondary raw materials and waste materials as possible while preserving very high physical-mechanical properties, including flexural and compressive strength, pull-off bond strength and abrasion resistance. High-temperature fly ash, waste slag and waste packaging glass are used in this paper as fillers. The resulting mortar shows high physical-mechanical properties, including high abrasive resistance and very high bonding strength to a large variety of building materials including concrete, steel, glass, and tiles.

Abrasive resistance of polyetherurethane ureas

The relationship between the structure of the polymer chains and the abrasion resistance of segmented polyurethane ureas based on polyoxytetramethylene oligoether was studied. Experimental data were obtained for systems with the hard segments content above 39%. It was found that the function of the volumetric wear of polyurethane-urea samples on the content of hard segments had an extremum; at high contents of these segments (more than 35%), a further increase in this content lead to a deterioration in the abrasion resistance. The reasons for this effect can be associated with a sharp deterioration in the strength and strain properties of the studied elastomers when additional amounts of diisocyanate are introduced into the system, which can lead to the formation of excessive interchain bonds.

An Evaluation of the Microstructure of High-Aluminum Cast Iron in Terms of the Replacement of Aluminum Carbide with Titanium Carbide or Tungsten Carbide

One of the problems with recycling is that of widespread contaminated steel scrap with an unwanted aluminum addition. In this paper, we will present a specific solution to this problem. The implementation of high-aluminum cast iron production has been considered. This cast iron is a cheap material resistant to high temperatures; additionally, it has increased abrasion resistance. Despite the above-mentioned advantages, high-aluminum cast iron has not been widely used in the industry so far, due to the difficulties encountered during machining and the occurrence of the phenomenon of spontaneous disintegration. The paper presents a method for replacing aluminum carbide with titanium carbide or tungsten carbide. This research shows that the carbide replacement procedure is sufficient in stopping the phenomenon of self-disintegration of a casting made of high-aluminum cast iron. Moreover, a new material was obtained, i.e., high-aluminum cast iron with precipitates of hard tungsten carbide and flake graphite. When considering the abrasive resistance of this material, flake graphite can be treated as the natural lubricant phase and tungsten carbide precipitation, as the hardening phase.

Recycled Tire Rubber in Additive Manufacturing: Selective Laser Sintering for Polymer-Ground Rubber Composites

Natural and synthetic rubber is gaining increased interest in various industrial applications and daily life sectors (automotive industry, acoustic and electrical isolators, adhesives, impermeable surfaces, and others) due to its remarkable physicomechanical properties, excellent durability, and abrasive resistance. These great characteristics are accompanied by some recycling difficulties of the final products, particularly originated from the tire waste rubber industry. In this study, recycled tire rubber was incorporated in polymer matrices using selective laser sintering as 3D printing technology. Two polymers were used-polyamide and thermoplastic polyurethane, for their rigid and elastomeric properties, respectively. Polymer composites containing various tire powder amounts, up to 40 wt.%, were prepared by physical blending. The final materials’ morphological characteristics, mechanical properties, and thermal stability were evaluated. The proposed ambitious additive manufacturing approach looked over also some of the major aspects to be considered during the 3D printing procedure. In addition, examples of printed prototypes with potential applications were also proposed revealing the potential of the recycled tire rubber-loaded composites.

Impact of Different Fiber Reinforcement on Flexural Strength, Fracture Toughness and Abrasive Resistance of Provisional Restorative Resin

Aim: To assess and compare the impact of reinforcement of PMMA with glass fibre, polyethylene fibre and carbon fibres on flexural strength, fracture toughness and abrasive resistance. Background: In view of inadequate mechanical and physical characteristics of PMMA which include low impact strength and low surface hardness and resulting lowered clinical performance of the prosthesis, the study was designed to investigate the impact of reinforcement of PMMA with glass, polyethylene and carbon fibers on flexural strength, fracture toughness and abrasive resistance. Methods and Findings: Rectangular specimens (n=120; 30 each from 4 groups; 65 × 10 × 3.3 mm3) were fabricated and loaded on Universal Testing Machine until fracture for flexural strength and fracture toughness and on Taber Abrasive Tester for abrasive resistance. Data were analyzed using one–way ANOVA followed by Post Hoc test - Bonferroni multiple comparison analysis, using significance level of 0.05. Significant increase in fracture toughness was observed in specimens reinforced with polyethylene and carbon fiber, albeit the values of flexural strength were increased insignificantly. Specimens reinforced with glass and carbon fiber had significantly low values of abrasive resistance. Conclusion: Findings indicate that reinforcement of PMMA by non-specific fibers like glass, polyethylene and carbon resulted in significant increase in fracture toughness and decrease in abrasive resistance.

MICROHARDNESS OF BORIDE COATINGS OBTAINED ON 65G STEEL FROM DIFFERENT COMPOSITIONS OF BORATING MIXTURES

The surface of the working organs of tillage equipment is subject to wear during operation. To obtain a surface layer of a part with high hardness and strength, corrosion resistance and abrasive resistance, there are used methods of chemical-thermal treatment, which consist in simultaneously exposing the surface to temperature and substances that can react chemically with the organ material. In this article, we consider the method of diffusion boronizing in coatings using the method of non-contact heating by high-frequency currents to study the microhardness of various boride coatings. (Research purpose) The research purpose is in studying the mechanical properties of boride coatings obtained by boronizing by heating 65G steel with high-frequency currents using various borating mixtures. (Materials and methods) An HDTV-40AV furnace was used to study the processes of boronizing using high-frequency surface heating. The temperature of the boronizing process was 950-1250 degrees Celsius, and the saturation process time was 40-180 seconds. Boron-carbide-based compositions were used. (Results and discussion) As a result of the studies, the microhardness of samples with different compositions of boronizing mixtures was studied. 65G steel was boronized. (Conclusions) According to the results of the study, the greatest microhardness was obtained using composition 6, containing manganese boride crystals (HV100 of 27570 megapascals, coating thickness of 250 micrometers) for a time of 120 seconds. However, the most suitable and less expensive to use in the agricultural industry were compositions based on boron carbide.

Development of a polyurea-based composition with an extended life span

Objectives. Improvement of the technology for obtaining polymer-sprayed coatings based on polycarbodiimides (polyureas) with high chemical, hydrolytic, and abrasive resistance and improved physical and mechanical properties, as well as obtainment of polyurea compositions with a lifetime of at least 5 min without loss performance characteristics (i.e., “hand-applied” polyureas) suitable for repair of coatings already in use.Methods. The reaction rate between isocyanate and amino groups is almost a hundred times higher than that between isocyanate and hydroxyl groups, necessitating the use of special highperformance and high-pressure installations equipped with self-cleaning mixing chambers and heating of components. The following are determined from the obtained materials: strength, elongation at break according to the standard method, Taber abrasion, and Shore hardness.Results. Three methods of slowing down the reaction are investigated: 1) the synthesis of prepolymers with the content of NCO groups from 10.5% to 18%; 2) the addition of a plasticizer into the prepolymer in the amount of 1–10 mass parts; and 3) the introduction of polyesters into the composition and radiation of the so-called “hybrid” systems. When using 14% polyesters with a molecular weight of 2000 Da, only “hybrid” systems make it possible to obtain compositions with a lifetime of more than 5 min. At the same time, the tensile strength decreases by 20%, and the abrasion increases by 40%; however, such “hybrid” systems have a higher adhesion force and are cheaper than pure polyureas, allowing them to be used as “repair” systems.Conclusions. The developed composition and technology of applying “hybrid” systems allow for the repair of existing coatings without using specialized devices. “Manual” polyurea is easy to use and does not require special training.

Graphene Oxide/Reduced Graphene Oxide Enhanced Noniridescent Structural Colors Based on Silica Photonic Spray Paints with Improved Mechanical Robustness

In contrast to traditional pigment colors, structural colors have developed a great potential in practical applications, thanks to their unique nonfading and color tunable properties; especially amorphous photonic structures with noniridescent structural colors have attracted considerable attention and their applications have expanded to more fields. Herein, graphene oxide (GO) and reduced graphene oxide (RGO) enhanced noniridescent structural colors with excellent mechanical robustness were established by a time-saving approach named spray coating, which allows for rapid fabrication of angular independent structural colors by spraying different photonic spray paints (PSPs) to ensure color multiplicity that was adjusted by the silica nanoparticles (SiO2 NPs) sizes onto the substrates. The incorporation of poly(methyl methacrylate-butyl acrylate) (PMB) improved the adhesion existing among SiO2 inter-nanoparticles and between SiO2 NPs and the substrates, taking advantages of the low glass transition temperature (Tg) of butyl acrylate derivative polymer and made PMB embedded PSPs coated patterns being imparted with good mechanical robustness and abrasive resistance. The peculiar light adsorption of GO and RGO across visible light spectrum facilitate higher color saturation. The improvement in color saturation of GO and RGO doped PSPs is expected to boost the promising applications in structurally colored paintings, inks and other color-related optical fields.

Study of Cracking Mechanism and Wear Resistance in Laser Cladding Coating of Ni-based Alloy

Ni-based coatings with the addition of a plastic phase- an austenitic stainless net were prepared using laser cladding technology, and the CeO2 was added in cladding layers. The cracking mechanism, microhardness, microstructure, phase composition, and wear properties were investigated. The relationship between thermal stress and the elastic and plastic fracture had been developed from the standpoint of fracture mechanics and thermal elastic fracture mechanics. The Fracture criterion of the nickel-based coating was obtained, and the study has shown that the crack sensitivity could be reduced by decreasing the thermal expansion coefficient Δα. Then a new method was proposed, in which the substrate was prefabricated the stainless steel net. It was found that the number of cracks reduced significantly with the addition of stainless steel net. When the stainless steel net with 14 mesh was added in Ni-based coatings, the average microhardness of nickel composite coating was 565 HV0.2, which was 2.6 times higher than that of the 45 steel substrate. Although the rare earth oxide 4 wt.% CeO2 and stainless steel net were added in the Ni-based coating reducing the microhardness (the average microhardness is 425 HV0.2), the wear resistance of it improved substantially. The wear volume of Ni-Based composite coating was 0.56×10-5mm3·N-1·m-1, which was 85.1% lower than that of 45 steel and 61.9% lower than that of Ni-based coating without CeO2 and stainless steel net. The experiment results have shown that the Nickel-based composite coating is equipped with low crack sensitivity and high abrasive resistance with austenitic stainless net and the rare earth oxide 4 wt.% CeO2.