In this study fire retarded HDPE/WF composites based on high density polyethylene (HDPE) and wood flour (WF) were investigated. Polymer and WF ratio was kept at 70/30 while concentration of fire ...retardant was 20 mass %. Ammonium polyphosphate and aluminum hydroxide were used as fire retardants. To diminish the influence of high loadings of fire retardants on mechanical properties two different types of organically modified nanofillers (CaCO3 and SiO2) were used. Surface modification of HDPE polymer and nanofiller was done to enhance the compatibility in composite and improve the mechanical properties and fire performance. Mechanical properties were characterized by dynamic mechanical analysis while compatibility of components in composites was followed through morphology by scanning electron microscopy. Thermal and fire properties were characterized by thermogravimetric analysis, pyrolysis combustion flow calorimetry, and limiting oxygen index. The obtained results show that addition of surface modified nanofiller considerably affects the morphology resulting in the enhancement of mechanical and fire properties. Ammonium polyphosphate fire retardant in combination with SiO2 nanofiller showed the highest limiting oxygen index value, the lowest heat release rate, and total heat released in pyrolysis-combustion flow calorimetry test indicating best overall fire performance.
Thermal properties and degradation of polyethylene LDPE (nano)composites were investigated by isoconversional thermogravimetric analysis in air and nitrogen atmosphere by applying the ...Kissinger-Akahira-Sunose method. Low-density polyethylene (LDPE) composites containing 3 wt.% nanofiller Cloisite 20A and 4, 6, and 8 wt.% of natural zeolite were prepared using extrusion/injection moulding. The parameters of thermal stability of the samples were determined i.e. onset temperature of the degradation (T
90
), which exhibit initial mass loss (10 mass %) and maximum loss rate temperature (T
max
). Also, activation energy (E
a
) of samples was calculated and interpreted in terms of thermal degradation mechanisms. Under nitrogen, the thermal degradation of LDPE (nano)composites follows a random scission pathway but it was retarded and slowed by the presence of the fillers. The results show that thermo-oxidative degradation of studied (nano)composites is induced at lower temperatures and appears as much more complex and multi-stage process.
A low-cost and fast potentiometric surfactant sensor for cationic surfactants, based on the new ion-pair 1,3-dioctadecyl-1
-imidazol-3-ium-tetraphenylborate (DODI-TPB), is presented. The new cationic ...surfactant DODI-Br was synthesized and characterized by NMR, LC-MS, and elemental analysis, and was used for synthesis of the DODI-TPB ionophore. The DODI-TPB surfactant sensor was obtained by implementation of the ionophore in PVC. The sensor showed excellent response characteristics with near-Nernstian slopes to the cationic surfactants DMIC, CPC, CTAB, and Hyamine 1622. The highest voltage responses were obtained for DMIC and CPC (58.7 mV/decade of activity). DMIC had the lowest detection limit (0.9 × 10
M) and the broadest useful linear concentration range (1.8 × 10
to 1.0 × 10
M). An interference study showed remarkable stability. Potentiometric titration curves for the titration of cationic surfactants (DMIC, CPC, CTAB, and Hyamine 1622), with DDS and TPB used as titrants, showed sigmoidal curves with well-defined inflexion points and a broad signal change. The standard addition method was successfully applied with recovery rates from 98.9 to 101.2 at two concentrations. The amount of cationic surfactant found in disinfectants and antiseptics was in good agreement with the referent two-phase titration method and the surfactant sensor on the market. This new surfactant sensor represents a low-cost alternative to existing methods for cationic surfactant detection.
Organophosphate esters (OPEs), are used as flame retardants and plasticizers to protect or enhance the properties of plastics, textiles, and many other materials. Sampling was carried out in ...groundwater from the karst aquifer Bokanjac–Poličnik near the city of Zadar, Croatia. To determine their continuous presence, samples were taken once during each season for one year. In the collected samples, nine OPEs were identified: tris(2-butoxyethyl) phosphate-TBEP, tricresyl phosphate-TCP, triphenyl phosphate-TPPA, tris(1-chloro-2-propyl) phosphate-TCPP, tris(2-chloroethyl) phosphate-TCEP, tris(1,3-dichloroisopropyl) phosphate-TDCPP, diethyl phthalate-DEP, tri-n-butyl phosphate-TBP, and di(2-ethylhexyl) adipate-DEHA.
Adequate, safe, and accessible water constitutes an essential resource for life and is an indispensable factor for the survival of humanity. In order to ensure uncontaminated water for water ...supplies, industry and agriculture, water quality is defined by microbiological, biological, chemical, and physical indicators. Water monitoring is regulated with the aim to protect human health from the adverse effects of polluted water by monitoring indicator parameters. For the purpose of proving drinking water safety, water sampling was performed at ten different locations, which are part of the water supply network of the town of Virovitica, in Croatia, and its surroundings. The results showed that all the analyzed parameters were in accordance with the ordinance, i.e., that the quality of water for human consumption was satisfactory.
This work demonstrates the poly(ethylene terephthalate) (PET) washing process, which is the very important step in the overall PET recycling procedure. The samples of waste PET bottles were washed in ...sodium hydroxide at two different temperatures, that is, at 70 and 75°C, at a time intervals of 15 and 30 min. The cleaning efficiency of the washing processes was determined through the identification of the residual impurities and products of PET degradation. The samples before and after the washing procedure were characterized by gas chromatography/mass spectrometry (GC/MS), gel permeation chromatography, thermogravimetric analysis and differential scanning calorimetry. Due to low obtained oligomer molecular masses, it can be concluded that the degradation during all washing processes is not strong. Results show good purity of washed PET, especially at 75°C, due to very low content of adhesives, toxic compounds and formed monomers. The washing process carried out at 75°C for 15 min can be considered as the most successful. It results with low polymer degradation and the removal of the high quantity of contaminants in short time interval.
Mechanical and morphological properties of composites containing styrene—acrylonitrile (SAN) copolymer, ethylene— propylene—diene (EPDM) polymer, and different types of precipitated calcium carbonate ...(PCC) were investigated and their properties were analyzed in regard to PCC surface properties and the way of sample preparation (with or without use of a masterbatch (MB)). Contact angles of test liquids on PCC samples were measured in order to determine surface free energies of filler and to predict strength of filler—polymer interactions. Filler—polymer interactions play a significant role in determining preferential localization of the filler in the composite. The tensile and impact strength results of the composites without the MB show much higher values than composites prepared with the MB. Significant decrease of tensile strength is observed for the samples prepared with the MB due to change in morphology, which is elongated dispersed EPDM particles in SAN matrix, compared to the samples prepared without the MB that have droplet morphology.
In this work, the mutual effect of the filler aluminum hydroxide Al(OH)
3
and the compatibilizers ethylene-propylene copolymer (EPR) and ethylene-vinyl acetate copolymer (EVA) on the properties of ...blends based on polyethylene (PE) and polypropylene (PP) was studied. The microstructural and morphological changes as well as mechanical features of samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and by tensile tests. Morphology of the samples prepared with the compatibilizers and filler is much finer in comparison to virgin blend. Due to established interaction between components that enhance the intimate adhesion among the components finer droplets dispersion within the blends matrix is observed. The addition of the filler and compatibilizers produced an increase in the elasticity particularly for the samples prepared in two-stage extrusion process where filler is first extruded with PE matrix and then extruded with other polymers of the blends.
Radon (222Ra) is a colourless and odourless natural radioactive element in gaseous state. The concentration of radon in the air is usually low, but it can be very high inside of a living space, ...because of its possibility to penetrate from a foundation soil over a basement into a building itself. People are daily exposed to a certain concentration of radon that is found in soil, water, air and food. This paper shows a correlation analysis of environmental parameters by using the model of multiple regressions. It defines certain statistical relations between environmental parameters such as temperature, humidity, and atmospheric pressure with measured values of radon concentrations. Measurements were carried out at several locations in various residential buildings in north-western Croatia. The results indicated that individual environmental parameters and radon concentration at individual locations were connected. For example, at one location the concentration of radon was decreasing if atmospheric pressure was increasing. Measurements at another location indicated that the concentration of radon was increasing if air humidity was increasing. Due to large number of different parameters affecting the concentration of radon in residential buildings, a satisfactory statistical model to predict the concentration of radon with environmental parameters is not easy to achieve since it was observed variability of radon concentrations with environmental parameters within different local sites. It is necessary to consider a longer period to determine with certainty a mathematical model that would give the most accurate prediction of radon concentration dependence on environmental parameters which can affect human health and quality of life.
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