Papers by Keyword: Hexabromocyclododecane

Abstract: In connection with the significant volume of polystyrene embedded in buildings as thermal insulation, in the next few years it will be needed to solve the matter of its disposal after the end of its life cycle. Hexabromocyclododecane (HBCDD) has been used as a flame retardant in polystyrene thermal insulation (EPS and XPS) for the last 50 years. The internationally recognized Stockholm Convention on Persistent Organic Pollutants prohibits future production, use and recycling of materials that contain HBCDD. It also, to a large extent, limits the options of waste management of such materials. European legislation, in particular Regulation (EC) No 850/2004 and the so called REACH Directive, established a binding legal framework for EU Member States which reduces waste management options of material containing HCDBB practically only to incineration. In the coming years, this fact requests fundamental changes in disposal of construction and demolition waste containing the polystyrene insulation and related processes on construction sites in the Czech Republic. The research is based on the analysis of the international and the Czech legislation related to this issue, and the analysis of material and technological context. The paper focuses on possible operational, economic, energy and environmental impact on the construction industry and environment, and compares the current situation in the Czech Republic with other European countries, and assesses the readiness of the Czech Republic to deal with the upcoming legislation changes.

Abstract: In the lost foam casting (LFC) of aluminum alloys, the expandable polystyrene (EPS) foam characteristics (foam composition, polymer processing and bead fusion) influence the formation of deleterious fold defects in the final casting. In this research, four types of EPS beads were investigated: (1) the regular EPS beads, (2) 2wt% hexabromocyclododecane and 2wt% dicumyl peroxide added to the EPS beads during the polymerization process, (3) 2wt% silicaalumina blended to EPS beads after the pre-expansion process of the beads and (4) 2wt% hexabromocyclododecane blended to EPS beads after the pre-expansion process of the beads. The density of the regular and modified EPS beads was kept constant at 25.63 kg/m3. Aluminum alloy A356 was poured at 1023 K into the window pattern. The window patterns with regular EPS beads did not fill completely and had identifiable carbon/oxide defects on the surface. The window patterns with the additives were completely filled with a few surface defects. From thermogravimetric analysis (TGA), it was found that the EPS beads with silica-alumina had a reduced onset temperature of degradation of EPS (from 634 K to 618 K) and a reduced activation energy (from 188 kJ/mol to 147 kJ/mol) relative to the regular beads. In the organic brominatedmodified EPS (both through blending and polymerization), it was found that the value of the preexponential (rate equation) was significantly increased. Through light optical microscopy (LOM) and scanning electron microscopy (SEM), it was found that the polymerization process additives increased the degree of bead fusion whereas the post pre-expansion additives decreased the degree of bead fusion. Finally, the EPS beads treated during the polymerization process produced castings with the least overall surface, subsurface and internal defects.