REVIEW OF THE PHYSICAL AND MECHANICAL CHARACTERISTICS OF POLYURETHANE NANOCOMPOSITES

Polyurethane nanocomposites are promising materials in many industries, they have superior physical and mechanical properties compared to the original polyurethane. This paper presents an analysis of the physical and mechanical properties of polyurethane nano-composites with various types of fillers such as organoclays, carbon nanotubes, polyhedral oligomeric silse-squioxanes, graphene, graphene oxide, polytetrafluoroethylene, and metal nanoparticles. The concentration-dependent effects in changing the structure and properties of polyurethane composites under the influence of the added fillers were also considered. It is noted that the values of physical and mechanical properties are influenced by the uniform distribution of nanofiller particles in the composite and their chemical modification. It was found that with a uniform distribution of nanoparticles in the polymer matrix, the physicomechanical properties of the resulting composites increase.

ANATOMICAL PROPERTIES OF STRAW OF VARIOUS ANNUAL PLANTS USED FOR THE PRODUCTION OF WOOD PANELS

The aim of this study was to determine basic anatomical features of annual plant fibers used as wood substitutes for the production of wood-based panels. For this purpose rye, wheat, triticale, rape and corn straw were used. The determination of the morphological features of the fibers was conducted on the macerated material. Fiber lengths, fiber diameters and lumens were measured, and then the fiber wall thicknesses and slenderness ratios were calculated. The result clearly showed significant differences among all fiber characteristics of the tested plants. The strength and direction of the relationship between the anatomical properties determined in the study and the physicomechanical properties of the boards produced with straw from the tested annual plants were identified.

STUDY OF VARIOUS QUALITY CHARACTERISTICS OF POLYESTER FIBERS OBTAINED ON THE BASIS OF PRIMARY AND SECONDARY POLYETHYLENE TEREPHTHALATE

The aim of study is comprehensive determination of various quality characteristics of polyester fibers obtained on the basis of primary and secondary polyethylene terephthalate. The analysis of the raw material base of pre-oriented yarns (POY) threads has been carried out. The technological, physicomechanical properties, as well as the structure of the primary and secondary polyethylene terephthalate used in the production of the threads have been studied. The structure and properties of polyethylene terephthalate changed: the properties were worse, the structure were amorphous, the molecular weight decreased. The structure of recycled polyethylene terephthalate changed as a result of technological conversions in the production of POY fibers. This is due to a change in the thermophysical characteristics and structure of secondary polyethylene terephthalate under the influence of heat, moisture, and shear stresses. A comparative analysis of the physicomechanical properties of POY yarns obtained from primary and secondary polyethylene terephthalate has been carried out.

Physical/Mechanical and Antibacterial Properties of Orthodontic Adhesives Containing Calcium Phosphate and Nisin

Enamel demineralization around orthodontic adhesive is a common esthetic concern during orthodontic treatment. The aim of this study was to prepare orthodontic adhesives containing monocalcium phosphate monohydrate (MCPM) and nisin to enable mineralizing and antibacterial actions. The physicomechanical properties and the inhibition of S. mutans growth of the adhesives with added MCPM (5, 10 wt %) and nisin (5, 10 wt %) were examined. Transbond XT (Trans) was used as the commercial comparison. The adhesive containing a low level of MCPM showed significantly higher monomer conversion (42–62%) than Trans (38%) (p < 0.05). Materials with additives showed lower monomer conversion (p < 0.05), biaxial flexural strength (p < 0.05), and shear bond strength to enamel than those of a control. Additives increased water sorption and solubility of the experimental materials. The addition of MCPM encouraged Ca and P ion release, and the precipitation of calcium phosphate at the bonding interface. The growth of S. mutans in all the groups was comparable (p > 0.05). In conclusion, experimental orthodontic adhesives with additives showed comparable conversion but lesser mechanical properties than the commercial material. The materials showed no antibacterial action, but exhibited ion release and calcium phosphate precipitation. These properties may promote remineralization of the demineralized enamel.

Influence of the nature of a polysaccharide on the surface-morphological and physicomechanical properties of sol–gel plates

Thin-film sol–gel plates based on chitosan and glucomannan polysaccharides in a wide range of compositions were obtained. The effect of the polysaccharide component on the SEM surface morphology and physicomechanical properties was evaluated. It was found that the introduction of the polysaccharide glucomannan (and/or Aloe Vera juice) into the composition of chitosan sol–gel plates increased the elastoplastic characteristics of the samples and had a significant effect on the surface relief of their solid phase. The obtained structures can be used for the design of bioadhesive sensor coatings with a high therapeutic effect, which is an urgent area for theranostics and regenerative medicine.