Tribology of Polymeric Materials Part 2 - Properties and tribological behaviour of polymeric materials

Tribološka ispitivanja mogu se provesti na nekoliko razina, od mikrorazine do nanorazine. Na toj osnovi mogu se istražiti korelacije između viskoelastičnosti, krhkosti i tribološkog ponašanja materijala na osnovi polimera koje odražavaju utjecaje sastava, orijentacije u magnetnom polju i obrade površine. Relacija između stupnja viskoelastičnog oporavka i krhkosti analizirana je u radu 2006. U raspravi su istaknuta znatna poboljšanja svojstava, uključivo i tribološka, dodatkom anorganskih mikročestica i nanočestica punila. Uočen je utjecaj površinske i međupovršinske napetosti u multifaznim sustavima na tribološka svojstva. Opisane su računalne simulacije tribološkog ponašanja kao dopuna eksperimentima. Predstavljene su osnovne razlike izme|u mikrotribologije i nanotribologije.Tribological investigations can be conducted at several size scales, from micro-level to nano-level. On this basis we can develop correlations between viscoelasticity, brittleness and tribological behaviour of polymer-based materials that reflect the effects of composition, orientation in the magnetic field and surface treatments. The relationship between the degree of viscoelastic recovery after sliding wear and brittleness was analyzed in 2006. Significant improvements of properties, including the tribological ones are discussed, by addition of inorganic micro-particles and nano-particles of fillers. The importance of surface and interface tensions in multiphase systems on tribological properties has been noted. Computer simulations of tribological behaviour as supplement to experiments are described. The basic differences between microand nano-tribology are presented

Waste and recycling materials used in concrete

Materials with higher strength and high performanceprovide excellent benefits. But after a very short useful-life become waste and contribute to environmental degradation. Some investigations are focused on recycling by using innovative and clean technologies. In this work, waste and recycled materials as well as gamma radiation are proposed as tools for improving mechanical properties of concrete; polyethylene terephthalate of bottles, automotive tire rubber as well as cellulose of Tetra Pak packages are studied as materials.Autonomous University of the State of Mexico (UAEM), Grant 3886/2015F

Physical and Mechanical Properties of Polymer Composites with High Content of Wastes Including Boron

Article describes study examining the physical and mechanical properties of polymer composite with wastes that incorporate boron

Properties of lightweight concrete blocks with waste zeolitic tuff

El artículo presenta el estudio de los efectos de la ceniza volcánica en las propiedades mecánicas y térmicas de blocks de concreto ligero

Zeta potential-viscosity relationship in kaolinite slurry in the presence of dispersants

AKÜ-BAPK / 042.MUH.03Kaolinite is a widely used additive for industrial applications. Hence, the properties of kaolinite affect the quality of the final materials. The fact that kaolinite is a heterogeneous mineral with dual charges has to be taken into account. In this study, the zeta potentials and the apparent viscosities of kaolinite suspensions in water in the presence of three dispersants; sodium silicate, sodium tripolyphosphate and sodium-polyacrylate at pH values of 4, 7 and 10 were determined. Diagrams of zeta potentials (ZPs) and viscosity as a function of dispersant concentration all show minima. The concentrations at which minima of these two properties appear do not coincide, except for those mineral dispersants at high pH values. The results are explained in terms of the spatial distribution of charges on basal and edge surfaces of kaolinite plates in acidic, neutral, and basic media.AKÜ-BAPK / 042.MUH.0

Waste materials from Tetra Pak packages as reinforcement of polymer concrete

In this work, different concentrations (from 1 to 6 wt%) and sizes (0.85, 1.40 and 2.36 mm) of waste Tetra Pak particles replaced partially silica sand in polymer concrete. As is well known Tetra Pak packages are made up of three raw materials: cellulose (75%), low-density polyethylene (20%) and aluminum (5%). The polymer concrete specimens were elaborated with unsaturated polyester resin (20%) and silica sand (80%), and irradiated by using gamma rays at 100 and 200 kGy. The obtained results shown that compressive and flexural strength as well as modulus of elasticity decrease gradually, when either Tetra Pak particle concentration or particle size is increased, as regularly occurs in composite materials. Nevertheless, improvements of 14% on both compressive strength and flexural strength, as well as 5% for modulus of elasticity were obtained when polymer concrete is irradiated

Thermal and mechanical properties of EPDM/PP + thermal shock-resistant ceramic composites

Abstract Dynamic vulcanizate blends of polypropylene (PP) and ethylene-propylene-diene rubber (EPDM) were filled with 5 wt% of micro-scale ceramic powder. To overcome the difficulty of particles dispersion and adhesion, the filler was modified through grafting using three kinds of organic molecules. A combination of Raman data with thermogravimetric analysis (TGA) results prove that grafting of organic macromolecules onto ceramic surfaces takes place. Dynamic mechanical analysis (DMA) has been performed from -100 to ?50°C; addition of the ceramic increases the storage modulus E 0 , more so for modified filler. Compared to PP and thermoplastic vulcanizate (TPV), a higher thermal expansion is seen after addition of the ceramic filler, a result of creation of more free volume. The tensile modulus of the composites is about 1.2 times that of pure TPV, an increase in the rigidity clearly caused by the ceramic. Fracture surfaces show weak bonding of filler particles to the matrix. In the sample containing modified filler the tensile deformation is going through the polymer matrix. The brittleness, B, decreases upon surface modification of the ceramic. The highest value of B is seen for the PP ? unmodified ceramic while lower B values are obtained for TPV and its composites

Preparation of Surface-Modified Nanocellulose from Sugarcane Bagasse by Concurrent Oxalic Acid-Catalyzed Reactions

Article presenting research where concurrent oxalic acid-catalyzed reactions, including cellulose hydrolysis and esterification of the hydrolyzed cellulose, were performed to prepare the nanocellulose from sugarcane bagasse

Accuracy in locating glass transitions: aging and gamma sterilization of vulcanized thermoplastic elastomers

Abstract: We have studied nine thermoplastic vulcanizate elastomers (TPVs) in four series: as made, after accelerated aging, after γ irradiation, after both irradiation and aging. The materials exhibit two glass transitions, one seen in crosslinked regions and the other in un-crosslinked amorphous regions. Three techniques of determination of glass transitions have been used and the results compared, all three based on dynamic mechanical analysis (DMA): as a peak in the loss modulus E''; as a peak in tan δ; and as the midpoint of the rapid decrease in the storage modulus E'. We recommend the last method for both fundamental and practical reasons

Evaluation of the Vibration Signal during Milling Vertical Thin-Walled Structures from Aerospace Materials

Article describes how the main functions of thin-walled structures are to reduce the weight of the finished product and to increase the rigidity of the structure. The authors compared the vibration signal for different approaches to machining thin walled-components with vertical walls made of Ti6AI4V titanium alloy and Inconel 625 nickel alloy