The effect of chemical treatment of hemp hurds slices in three solutions (EDTA (Ethylenediaminetetraacetic acid), NaOH and Ca(OH)2) on the properties of natural material was discussed in this paper. Changes in the morphology, chemical composition and structure as well as thermal stability of hemp hurds before and after their modification were investigated by using FTIR (Fourier transform infrared spectroscopy), XRD (X-ray powder diffraction analysis) and TG (thermogravimetry)/DSC (differential scanning calorimetry). Size exclusion chromatography (SEC) measurements were used for determination of degree of cellulose polymerization of hemp hurd samples. Chemical modification is related to the partial removal of non-cellulosic components of lignin, hemicellulose and pectin as well as waxes from the surface of hemp hurd slices. Another effect of the chemical treatment applied is connected with increasing the crystallinity index of cellulose determined by FTIR and XRD methods. Decrease in degree of cellulose polymerization and polydispersity index in chemically modified hemp hurds compared to the original sample was observed. Increase in thermal stability of treated hemp hurd was found. The most significant changes were observed in alkaline treated hemp hurds by NaOH.
Sustainability goals are essential driving principles for the development of innovative materials in the construction industry. Natural fibers represent an attractive alternative as reinforcing material due to good mechanical properties and sustainability prerequisites. The study has been focused on the comparative investigation of chemical and physical treatments of hemp hurds and their influence on the thermal behavior of main hemp constituents in air and nitrogen atmosphere. Thermal decomposition of hemp hurds involves several parallel reactions related to heat and mass transfer processes. A comparison of DSC and TG/ DTG results of hemp hurds samples before and after treatments demonstrates a better thermal stability for treated samples. It is caused by changes in chemical composition due to a partial removal of non-cellulosic components from hemp hurds structure, an increase in cellulose content and decrease in its degree of polymerization. The results show different thermal behavior of the hurds samples heated under nitrogen and air atmosphere. Based on DTG records, several-stage process of mass loss has been found for the samples under air, whereas only two-stage process under nitrogen.
The radionuclide activities of 226Ra, 232Th and 40K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices) of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in the cements ranged from 8.58–19.1 Bq·kg−1, 9.78–26.3 Bq·kg−1 and 156.5–489.4 Bq·kg−1 for 226Ra, 232Th and 40K, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Raeq = 67.87 Bq·kg−1, gamma index Iγ = 0.256, alpha index Iα = 0.067, the absorbed gamma dose rate D = 60.76 nGy·h−1, external hazard index Hex = 0.182 and internal hazard index Hin was 0.218. The radionuclide activity in composites ranged from 6.84–10.8 Bq·kg−1 for 226Ra, 13.1–20.5 Bq·kg−1 for 232Th and 250.4–494.4 Bq·kg−1 for 40K. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.
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