This research determines whether the materials of volcanic ash (CV), rice husk ash (CR), and thermally treated solid waste (RS-T), coming from the pyrolysis of plastics, have some flame-retardant effect when added to polypropylene flame-retardant additives (such as ammonium polyphosphate and pentaerythritol). These materials were characterized by specific surface area by nitrogen adsorption analysis (Brunauer–Emmett–Teller) and X-ray fluorescence and X-ray diffraction methods. It was determined that SiO2 and Al2O3 are considered as flame-retardant minerals. Composites composed of polypropylene, ammonium polyphosphate, pentaerythritol, and these materials at several concentrations, from 1% to 9%, were prepared. The thermal stability and flame retardancy of the composites synthesized were investigated based on the limiting oxygen index, thermogravimetric analysis, and cone calorimetry. It was determined that these materials have a synergistic action with flame-retardant additives by increasing the fireproof properties of polypropylene. Mechanical properties were determined by tensile tests.
Plastic waste and its inadequate final disposal are a serious problem of environmental pollution, which has increased considerably in this time of pandemic due to the use of masks, gloves, food packaging or others, which will eventually reach the oceans, increasing the problem of the islands that are made up of plastic waste. Since the final disposal techniques of plastic waste are insufficient, in this research the catalytic pyrolysis has been evaluated using zeolites synthesized from volcanic ash of the Ubinas volcano (Peru), as catalysts. For this, two catalysts were synthesized, Z1 and Z2 zeolite, made at 150 and 180 °C in a 5 M NaOH solution, respectively. The pyrolysis was carried out at a catalyst/polymer ratio of 10 and 20 % and it was compared with a synthetic zeolite (ZSM-5) and without catalyst at a reaction temperature of 450 °C. The essays were carried out with PP virgin and plastic waste. It was determined that catalytic pyrolysis using natural zeolites synthesized from volcanic ash are appropriate for the treatment of plastic materials and that they tend to generate a higher proportion of pyrolytic gases and do not generate carbonaceous residues.
This work studies the feasibility to employ a combination of volcanic ash (natural waste) with different raw materials in the production of geopolymers: fly ash and mining tailing (considered hazardous solid waste), natural pozzolan, and metakaolin. This study compares the properties of geopolymers based on volcanic ash with fly ash, pozzolan, metakaolin, and mining tailing in a relation of 1:1 with the addition of NaOH 15M and Na2SiO3 as alkali activators. FTIR and XRD assays and mechanical tests were employed to characterize the geopolymers. The results showed that those materials can be used as raw materials to produce geopolymers. Additionally, the results revealed that prime material composition and their mineralogical characteristics influence the geopolymerization reaction and compression strength, reaching values of 35 MPa for the volcanic ash-pozzolan mixture. The pozzolan is a good source of Al2O3 and SiO2 and is highly reactive to the alkali activators resulting in a better geopolymerization in comparison to the mixtures of volcanic ash with metakaolin, fly ash, or mining tailing.
In this study, metallic constantan (Cu55–Ni44–Mn1wt%) alloy substrates were investigated as an alternate choice of substrates to grow carbon nanotubes (CNTs). No additional catalysts were used other than the as-rolled and annealed substrates to process CNTs on them. High density CNT growth was observed to take place on these substrates when suitable conditions were used in a thermal chemical vapor deposition (CVD) furnace with C2H2 as the carbon precursor. Scanning electron microscopy and transmission electron microscopy on these samples indicated the presence of several micron long CNTs ranging in 20–100nm in diameter. Raman spectra taken from the samples confirmed the presence of G band peaks (peak at ∼1580cm−1) and D band peaks (peak at ∼1320cm−1) commonly observed in CVD grown multiwall CNT samples with varying intensity ratios depending on the processing conditions.
In this research, the influence of natural zeolites obtained from the volcanic ash of the Ubinas volcano has been studied as synergistic agents in a flame-retardant system (composed of ammonium polyphosphate, pentaerythritol, and polypropylene). Four zeolites were synthesized from volcanic ash, including those that had been calcined and those that had not. These were then placed in an alkaline solution at three synthesis temperatures. Zeolites were characterized through X-ray diffraction, specific surface area by nitrogen adsorption analysis (Brunauer–Emmett–Teller) and scanning electron microscopy. Polypropylene matrix composites were prepared with ammonium polyphosphate, pentaerythritol and zeolites at 1, 5 and 9%. Its thermal stability and fire resistance were evaluated by thermogravimetric analysis, limiting oxygen index, vertical burning test and cone calorimeter and its morphological structure by scanning electron microscopy. It was determined that the synthesis temperature and the use of calcined and without calcined volcanic ash have an influence on the characteristics of the zeolites and on its synergistic action.
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