International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This work investigate electromagnetic and thermal properties of poly(lactic) acid-based composites with graphene nanoplates (GNP) and multiwalled carbon nanotubes (MWCNTs), produced by solution blending method. It was found that the MWCNT carbon nanotubes are an effective filler for both absorption and reflection of electromagnetic waves in the GHz and THz frequency domains. The higher aspect ratio of carbon nanotubes, compared to industrial MWCNT, is the cause of better electromagnetic characteristics of nanocomposites prepared by solution blending method (SB). The DSC analysis of the samples shows that the glass transition is around 60oC, followed by cold crystallization with enthalpy and melting temperature around 150oC. The TGA analysis show, that the thermal stability of PLA polymer is improved by addition of 6% MWCNTs and GNP.

The paper researches the influence of two tillage systems – conventional tillage and strip tillage on soil nutrients content, soil acidity and microbiological activity over a reseаrch period of four year – from 2014 to 2017 included. The test are carried out on the same fields in Northeastern Bulgaria. Soil nutrient testing can help determine the necessary amount of fertilizers to be used on a specific field.