Due to the widespread use of wood-plastic composites (WPCs), high-density polyethylene-wood flour composites (HDPE/WF) were studied in order to determine their stability in different application conditions. UV degradation and periodic absorption/desorption of moisture cause damaging changes to material during WPCs’ exterior application, so it is necessary to ensure WPCs’ durability against atmospheric influences. Samples were characterized by FTIR spectroscopy and scanning electron microscopy (SEM) in order to study the degradation after simulated weathering. The degree of water absorption was also determined. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used for the determination of composites’ thermal properties. Results show that the stability of the HDPE/WF composites to UV treatment highly depends on stabilizer content and its dispersion in the polymer matrix. Incompatibility of HDPE and wood particles is a major problem that should be solved to achieve good durability and satisfying properties in use.

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.

(1) Background: Radon concentrations in the environment are generally very low. However, radon concentrations can be high indoors and can cause some serious health issues. The main source of indoor radon (homes, buildings and other residential objects) can be soil under the house, while other sources can be construction materials, groundwater and natural gas. Radon accumulates mainly in the lower levels of the buildings (especially low-ventilated underground levels and basements). (2) Methods: in this paper, we have measured the indoor radon concentrations at 15 locations in various objects (basements and ground floor/1st floor rooms) in the area of northern Croatia. (3) Results: the results show a higher concentration of radon in the basement area in comparison to values measured in the ground floor and first-floor rooms. The arithmetic mean (AM) and geometric mean (GM) of basement rooms were 70.9 ± 38.8 Bq/m³ and 61.2 ± 2.2 Bq/m³ compared to ground floor and first-floor rooms 42.5 ± 30.8 Bq/m³ and 32.8 ± 2.9 Bq/m³, respectively. (4) Conclusions: results obtained (AM and GM values) are within the maximal allowed values (300 Bq/m³) according to the Euroatom Directive. However, there are periods when maximum radon concentration exceeds 300 Bq/m³. Indoor radon concentrations vary with the occupancy of the rooms and it is evident that the ventilation has significant effect on the reduction of concentration.

Surface properties of blends prepared of styrene-acrylonitrile and ethylene-propylene-diene changing the homopolymer proportions and compatibilized by high impact polystyrene have been studied by contact angle measurement. The surface free energy of interphase of homopolymers pairs, work of adhesion, and wetting coefficient were calculated using Wu’s geometric mean method and the total surface free energy and acid–base components of the blends by using van Oss, Good and Chaudhury method. Blends were also characterized by dynamic mechanical analysis and by scanning electron microscopy. The miscibility of studied blends was estimated through changes of surface free energy, energy of interface and through the shifts of glass transition temperature and changes in morphology. From the results, it can be seen that added compatibilizer reduces the interface energy and provides more homogenous system by interfacial segregation and rearrangements of molecules at the blend surface. The results of morphological observations reveal that the addition of a small percentage of compatibilizer decreases the domain size of the dispersed phase and enhances the compatibility of the blends.