Mechanical Properties of Polylactide Admixed with Carbon Nanotubes or Graphene Nanopowder

The aim of this work was to verify the material properties of polylactic acid (PLA) with an addition of carbon nanotubes (CNTs) or graphene nanopowder (GNP). The pure polylactide and admixed polylactide samples were subjected to chemical–physical tests to determine their stiffness and strength parameters. The tensile and impact tests were performed on samples without UV (ultraviolet) treatment and after UV treatment, in a physiological saline solution. The investigations were composed of two stages. The first one was related to the examination of the properties of pure polylactide, denoted as the following: 3001D, 4032D, and 4043D. The second stage was based on an analysis of the properties of PLA 4032D with an admixture of GNP or CNTs, at 0.1 wt.% and 0.5 wt.%. By comparing the strength and the stiffness of pure samples with samples with the considered admixtures, an essential increase was not observed. However, it is stated that the presence of GNP and CNTs in the samples positively influenced the resistance of the materials to the ageing process.

Structure and Stability Analysis of Antibacterial Substances Produced by Selenium Enriched Bacillus Cereus

Microorganisms can produce many antibiotics against bacteria and fungi, which have been used as potential choice of new antibiotics. In this paper, Bacillus cereus, was used to study the properties of antibacterial substance in its fermentation supernatant. The results showed that the source of antibacterial activity of Bacillus cereus was mainly the antibacterial substance produced by acid precipitation method, and further characterization speculates that the antibacterial substance may be lipopeptide substance. Then the antibacterial spectrum of the antibacterial substance was investigated, which showed that the antibacterial substance only had good inhibitory effect on Gram-positive bacteria and fungi, and selenium enrichment could significantly enhance the antibacterial activity of lipopeptide antibacterial substance produced by Bacillus cereus, and the inhibition mode of antibacterial substance to indicator bacteria was determined. The effects of different treatment methods on the stability of antibacterial substance were studied and the results showed that the antibacterial substance were stable to heat, ultrasonic and ultraviolet treatment, and their antibacterial activity would not be greatly affected. However, they were sensitive to pepsin. The optimum pH range of antibacterial activity was 3-5. This study may contribute to reuse the fermentation supernatant often discarded in the previous fermentation process. At the same time, the lipopeptide antibacterial substance extracted from the fermentation broth of selenium enriched Bacillus cereus can be used in the development of antibiotics and biopesticides, and open up a new way for the control of plant diseases.

Experimental Studies of the Physical and Mechanical Properties of Glued Building Materials Based on Modified Veneer

Today, glued timber products occupy a significant place in the volume of finished products of modern construction and woodworking enterprises. Plywood is one such product. The durability and structural characteristics of plywood depend on the quality of binder, the type of wood and the quality of veneer. The paper explores the technology of ultraviolet treatment of thermally modified birch veneer with subsequent production of waterproof plywood. The results of a study on the influence of the operating parameters of veneer modification on the complex of sorption and strength characteristics of plywood materials are presented. It is established that the combination of thermal modification of wood throughout the entire volume with surface treatment with ultraviolet radiation allows creating glued wood material with increased water resistance and high-quality adhesive interaction.

Increasing the Strength of the Glue Line in the Production of Thermally Modified Wood Paneling

This work is devoted to the study of the effect of ultraviolet rays for the surface activation of pine wood thermally modified at temperatures of 180−240 °C in order to increase the surface roughness, enhance the wettability of thermal wood and the adhesive strength of the glue in the production of wood block furniture panels. Studies were carried out to measure the contact angle of wettability of thermally modified wood samples of pine, as a result of which it was determined that the ultraviolet treatment process contributes to an increase in the adhesion properties of the surface layer of thermally modified wood by more than 13% due to the reactivity of ultraviolet rays to oxidize and degrade ligno-containing wood products. At the same time, the most active process of surface activation takes place during 60 min of ultraviolet irradiation of wood with a total irradiation of at least 125 W/cm2. It was revealed that the combined effect of two-stage wood processing, including preliminary volumetric thermal modification followed by surface ultraviolet treatment, causes an increase in the moisture resistance of glued wood products by 24%. So, if the strength of the glue seam when gluing natural wood samples after boiling decreased by 46%, then the samples that underwent two-stage processing showed a decrease only by 22%. In connection with the results obtained, an improved technology for the production of furniture boards for the manufacture of moisture-resistant wood products is proposed.

Investigation of nitrogen purging prior to UV treatment on quality of milk

Ultraviolet treatment (UV-C) is well known for its antimicrobial effects and current research shows that it has the potential to inactivate microorganisms in milk at much lower temperatures than conventional thermal treatment. However, Ultraviolet irradiation may result in adverse effects on milk quality, which arises due to photo oxidation in the presence of oxygen. Limiting the dissolved oxygen content in milk can minimize oxidative damage and thus, result in a better product quality. Nitrogen purging could be an effective method for reducing dissolved oxygen from liquids. The present study evaluates effects of nitrogen purging (prior to UV treatment) on milk quality. It was found that nitrogen purged UV treated milk causes minimal changes to physicochemical properties of milk.