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Povzetek: Polyurethane foam (PUR) is a lightweight, thermally insulating, widely used, and highly flammable material that has after its use an adverse effect on the environment, i.e., PUR disposal is considered hazardous. Its flammability can be mitigated using various fire retardants, but they do not change the hazardous nature of waste PUR. Therefore, in the current study, waste PUR with and without flame retardants based on N and P was incorporated into a geopolymer, the alkali-activated material (AAM) based solely on metakaolin, to evaluate the potential recycling route of waste PUR while taking into account its flammability, so it can enter safely into the circular economy through the building industry. To enhance the mechanical properties of the composite, a fresh mixture was irradiated with microwaves. However, the irradiation of geopolymer containing PUR negatively influenced mechanical performance, which led to the evaluation of the behaviour of the complex dielectric constant of PUR and fire retardants. Materials and composites were evaluated regarding their chemistry, mineralogy, microstructure, and porosity to connect the structure with extrinsic properties like geometrical density, thermal conductivity, and fire properties. Nonetheless, positive influences of PUR being encapsulated in the geopolymer were lowered density (from 1.8 to 1.6 kg/l) and improved thermal insulation ability (from 940 to 860 mW/(m·K)) of the composites: with the inclusion of <5 % of PUR, thermal insulation improved by nearly 10 %. However, the contribution of PUR to the composite originated from its skeleton, which has more than 15 times bigger geometrical density (0.81 kg/l) compared to the density of the skeleton (0.047 kg/l). This offers an open field for further advancements of thermal properties, but would also lead to a decrease of the compressive strength, which was already lowered from 90 MPa for 30 % with <5 % of added grated PUR. Furthermore, the flammable nature of PUR and its other drawbacks can be controlled by permanent embedding in the noncombustible structure of geopolymer, making the envelope of sustainable buildings green and safer. Overall, including grated waste PUR in geopolymer represents a promising, easy, cost-effective recycling path with low energy consumption, where the composite cannot develop fire on a scale of pure PUR, even in the worst-case scenario, but only if the composite is designed in a way, that flammable materials cannot join flames during their combustion. This paper gives prospects to other flammable waste materials to be safely used in the circular economy, and to porous materials to shape properties of the composite by their intrinsic and/or extrinsic properties.
Ključne besede: waste polyurethane foam, polymeric flame retardants, alkali activated material, metakaolin, microwave irradiation, thermal-fire behaviour, mechanical strength
Objavljeno v DiRROS: 01.03.2024; Ogledov: 184; Prenosov: 169
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Povzetek: Alkali activation is a chemical process whereby materials rich in aluminosilicate, which dissolves in basic media at room temperature, form binding phases by polycondensation. The alkali- activated materials (AAM) are a promising alternative to binding materials such as cement or other products in civil engineering (van Deventer et al., 2012). This study investigates the early age shrinkage behavior of Slovenian ladle and electric arc furnace slag - based alkali activated materials at different curing temperatures. The dimensions of specimens cured at room temperature and elevated temperatures up to 90 °C were measured over the first 7 hours (every 10 min). The results show that the most shrinkage occurred at the highest temperature, owing to the highest rate of evaporation of liquid content. Loss of mass follows from the drying shrinkage.
Ključne besede: alkali activated materials, shrinkage, compressive strength
Objavljeno v DiRROS: 01.03.2024; Ogledov: 115; Prenosov: 78
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Ključne besede: gozdovi, gozdni proizvodi
Objavljeno v DiRROS: 29.02.2024; Ogledov: 165; Prenosov: 43
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Povzetek: Prispevek predstavlja ključne vidike nove evropske uredbe, imenovane EUDR, in analizira njene posledice za zunanjo trgovino Republike Slovenije. Uredba je bila sprejeta kot odgovor na vedno večje težave glede krčitev in degradacije svetovnih gozdov. EUDR uveljavlja pravila in sistem potrebne skrbnosti za sedem ključnih primarnih proizvodov, ki so odgovorni za največji delež krčitev in degradacije gozdov, in sicer za dajanje na trg v državah članicah Evropske unije (vključno z uvozom iz tretjih držav) ter za izvoz v tretje države. To pomeni široko razširitev v primerjavi z dosedanjo uredbo EUTR, ki je prav tako določala obveznosti gospodarskih subjektov, ki dajejo les in lesne proizvode prvič na trg Evropske unije. Uredba EUDR nalaga nove zadolžitve gospodarskim subjektom in trgovcem, vplivala pa bo tudi na pristojne organe in carinske službe. Zaradi predvidevanja mogočih vplivov začetka izvajanja uredbe se prispevek osredotoča tudi na dve, za Slovenijo ključni kategoriji, in sicer lesni proizvodi in guma, ter predstavlja značilnosti zunanjetrgovinske menjave Slovenije z državami članicami in nečlanicami EU.
Ključne besede: uredba EUDR, krčenje gozdov, sistem potrebne skrbnosti, zunanja trgovina, tveganje
Objavljeno v DiRROS: 29.02.2024; Ogledov: 168; Prenosov: 55
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Ključne besede: recenzije
Objavljeno v DiRROS: 29.02.2024; Ogledov: 162; Prenosov: 0
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