Photocurable polymethacrylate-silica nanocomposites: correlation between dispersion stability, curing kinetics, morphology and properties

A comprehensive study of model systems based on poly(ethylene glycol) dimethacrylate and two methacryloxy-modified silicas (Aerosil R7200 and R711) were investigated to find possible correlation between the stability of the monomer/silica dispersion, curing kinetics, composite morphology and physical and mechanical properties of the final hybrid material. The monomer/silica dispersions were cured photochemically. The investigated parameters: Zeta potential, polymerization rate and conversion, glass transition, surface roughness and mechanical properties were found to be synchronous; when plotted as function of silica content, they showed maxima or changes in the trend at the same filler loading. This threshold (optimum) silica content in the composition was about 5 wt.-% for the investigated systems. The results obtained are discussed in terms of the solvation cell (which influences dispersion stability) and the interphase layer formation as well as their changes below and above of the threshold filler content

Recovered carbon black; material characterization and in-rubber performance:Sustainable future of tire manufacturing

Carbon black is widely used as a reinforcing filler in tire industry.This project aims to recover high quality carbon black from used tires using a novel pyrolysis process. The influence of process temperature on the recovered carbon black(RCB) properties was studied. Pyrolysis was carried out using passenger car tire(PCT) feedstock at temperatures of 500°C(PCT500) and 550°C(PCT550). Material properties and in-rubber performance were compared to a reference carbonblack commonly used in tires

Magnetosomes - Bacterial Magnetic Nanoparticles

The magnetic properties, magneto-optical effects and hyperthermia effect were studied in solution of magnetosomes extracted from cultivated bacteria Magnetospirillum sp. AMB-1. The properties of magnetosomes were changed using different conditions during synthesis and by modification of particles after synthesis by using sonication and ultracentrifugation methods. It was shown that adding a higher amount of Wolfe's vitamin solution (WVS) or ferric quinate (FQ) cause increase of the mean diameter from 47 nm (normal condition) up to 52 nm and 58 nm respectively. Hyperthermic measurements were performed for three types of magnetosome samples: (I) M - not influenced by separation method (long - chains magnetosomes), (II) UM - after centrifugation procedure, and (III) SM - after centrifugation procedure including sonication. The Specific Absorption Rate (SAR) decreased depending on chains shortening and decrease in hysteresis too. The SAR values were 1083, 934 or 463 W/g for the sample M, UM and SM, respectively

Effect of the Chain Length and Temperature on the Adhesive Properties of Alkanethiol Self-Assembled Monolayers

Stable and hydrophobic self-assembled monolayers of alkanethiols are promising materials for use as lubricants in microdevices and nanodevices. We applied high-rate dynamic force spectroscopy measurements to study in detail the influence of the chain length and temperature on the adhesion between methyl-terminated thiol monolayers and a silicon nitride tip. We used the Johnson-Kendall-Roberts model to calculate the number of molecules in adhesive contact and then the Dudko-Hummer-Szabo model to extract the information about the position and the height of the activation barrier per single molecule. Both parameters were determined and analyzed in the temperature range from 25 to 65 °C for three thiols: 1-decanethiol (measured previously), 1-tetradecanethiol, and 1-hexadecanethiol. We associate the increase of the activation barrier parameters versus the chain length with lower stiffness of longer molecules and higher effectiveness of adhesive bond formation. However, we relate the thermal changes of the parameters rather to rearrangements of molecules than to the direct influence of temperature on the adhesive bonds

A multi-technique characterization of the tribofilm formed by a fully formulated CVT fluid

In this work, the morphology, thickness, chemical composition and mechanical properties of the tribofilm formed by a fully formulated CVT fluid are investigated by multiple techniques and linked to the frictional and wear characteristics of a pin-on-disc tribosystem. It is found that the tribosystem shows higher friction and wear when tested at 150 °C than at 80 °C. The main reason is that although the morphology and thickness are similar, the tribofilms formed at different temperatures have different chemical compositions and mechanical properties. The tribofilm formed at 150 °C is Fe richer and has greater hardness and shear strength, which leads to a higher tribochemical wear rate and a greater interfacial shear force

Sialon and Alumina Modified UV-Curable Coatings with Improved Mechanical Properties and Hydrophobicity

This article describes the modification of UV-curable coatings with silicon aluminum oxynitride (Sialon) and aluminum oxide (Alu C), which improve the hydrophobicity of the coating surface and the scratch hardness. The contact angle is greater due to surface roughness being enhanced with inorganic fillers. Improved scratch resistance results from the formation of a sliding layer triggered by the diffusion of Sialon or alumina on the coating surface. One can observed an increase in the surface hydrophobicity as well as in the scratch hardness (up to 100%) when small amounts (5 wt.%) of the inorganic compounds are added. Imaging microscopies, i.e., SEM, OM, and AFM (with nanoscopic Young’s modulus determination), revealed the good distribution of both types of fillers in the studied matrix

Reversible acetalization of cellulose: A platform for bio-based materials with adjustable properties and biodegradation

Bio-based and biodegradable polymers are essential for a sustainable society. Cellulose is the most abundant biopolymer on earth; however, derivatization is necessary for its processing, which slows down its biodegradability dramatically, e.g. used cigarette filters made from cellulose acetate are barely biodegradable. We developed the first reversible modification of cellulose, which allows processing and guarantees full biodegradation even at high degrees of substitution as the linkers, acetals, can be cleaved first during the degradation process releasing native cellulose that biodegrades in a second step. Acetalization is a versatile platform approach to bio-based and fully degradable cellulose-derivatives, which are characterized by solubility in common organic solvents (alcohols, aromatic and chlorinated solvents), adjustable glass transition temperatures (-48 °C < Tg < 80 °C), young's modulus (1.9 MPa < E < 58 MPa) and contact angle (86°< θ < 124°). In contrast to previously known cellulose modifications, cellulose acetals remain fully degradable as the acetal bond is reversible and undergoes an acidic cleavage under desired conditions, for instance in compost, followed by enzymatic degradation of the remaining cellulose backbone. With climate change and plastic pollution, these new and versatile cellulose acetals provide bio-based and biodegradable alternatives to fossil-based and non-degradable polyolefin plastics, leading to a more sustainable future for our planet