Ecological, health and environmental concerns are driving the need for bio-resourced foams for the building industry. In this paper, we examine foams made from polylactic acid (PLA) and micro cellulose fibrils (MCF). To ensure no volatile organic compounds in the foam, supercritical CO2 (sc-CO2) physical foaming of melt mixed systems was conducted. Mechanical and thermal conductivity properties were determined and applied to a net zero energy model house. The results showed that MCF had a concentration dependent impact on the foams. First structurally, the presence of MCF led to an initial increase followed by a decrease of open porosity, higher bulk density, lower expansion ratios and cell size. Differential Scanning Calorimetry and Scanning Electron Microscopy revealed that MCF decreased the glass transition of PLA allowing for a decrease in cell wall thickness when MCF was added. The mechanical performance initially increased with MCF and then decreased. This trend was mimicked by thermal insulation which initially improved. Biodegradation tests showed that the presence of cellulose in PLA improved the compostability of the foams. A maximum comparative mineralization of 95% was obtained for the PLA foam with 3 wt.% MCF when expressed as a fractional percentage of the pure cellulose reference. Energy simulations run on a model house showed that relative to an insulation of polyurethane, the bio-resourced foams led to no more than a 12% increase in heating and cooling. The energy efficiency of the foams was best at low MCF fractions.
Biopolymer foams manufactured using CO2 brings a novel intersection for economic, environmental, and ecological impact. PHBV has a low solubility in CO2 while PCL has a high CO2 solubility. In this paper, PCL is used to blend into PBHV and unfoamed and foamed systems are examined. Foaming the binary blends at two depressurization stages with subcritical CO2 as the blowing agent, produced open-cell and closed-cell foams with varying cellular architecture at different PHBV concentrations. Differential Scanning Calorimetry results showed that a reduction in miscibility occurred as the concentration of PHBV increased in PCL matrix, while Scanning Electron Microscopy results showed the occurrence of bimodal cellular properties in some of the foam fractions, which improved their performance properties significantly. The results on the acoustic performance showed limited impact from foaming over the unfoamed blends but mechanical performance of foams showed a significant impact from PHBV presence in PCL. Thermal performance reflected that foams were affected by the blend thermal conductivity, but the impact was significantly higher in the foams than in the unfoamed blends.
A low-grade gold ore from Ilesha-Itagunmodi, south western Nigeria was panned, dried and ball-milled before sieving into fractions. The morphological, mineralogical and chemical composition was studied by optical microscopy (Reflected and Transmission), X-ray diffraction (XRD) and Energy Dispersive X-ray fluorescence (XRF), respectively. The sieved fractions were subjected to chemical analysis (AAS). The +106 μm sieve had the highest concentration of the mineral and was then selected for the upgrade through froth flotation using standard reagents. In this paper a report on a 2 k factorial experiment that provides an understanding of the impact of operational variables on the quantity of gold mineral obtained from the ore during froth flotation is presented. Analysis results showed that Ilesha-Itagunmodi gold ore is non-refractory with fine grain particles, amenable to froth flotation and contained about 20 other associated minerals, gold had a concentration of about 0.0024%. A combination of P-Xanthate and amine glycol collectors at a pH of 9.2 only produced a considerable increase in gold yield. This translated to about 87.13% increase in recovery of gold from the ore. Analysis of variance (ANOVA) was carried out and the model equation obtained was subsequently optimised to obtain a model equation that could be used in predicting the recoverable quantity of gold, indicating that F 11,1-values for Collector concentration, Frother concentration, pH and Conditioning time were 156.86, 6.96, 43.81, and 56.77 respectively. A model with an F value of 88.41 was obtained which indicated that the model was significant. The model equation obtained was subsequently optimised to be able to predict the recoverable quantity of gold. A "Pred R-Squared" value of 0.9365 (93.65%) was also obtained and is in reasonable agreement with the "Adj R-Squared" value of 0.9534 (95.34%). It was established that Ilesha placer gold ore is amenable to froth flotation using standard reagents.
Materials design and development continue to be more relevant as applications continue to rise for additively manufactured carbon-fiber-reinforced-plastic (CFRP) composites. Plastic matrixes bond and protect the fiber and help to transfer load through the composite to support intended applications. This makes it more necessary to understand the influences of thermoplastic matrixes on the mechanical performance of the composites fabricated through the additive manufacturing (AM) technique. This study investigated Acrylonitrile–Butadiene–Styrene (ABS) and Polyamide (PA) matrixes, which represent the bulk of the amorphous and semicrystalline engineering-grade thermoplastics matrixes, respectively, used in CFRP composite applications. Mechanical properties: tensile, compression, flexural, and thermal properties were examined, with the results showing the thermoplastic matrixes compositions and morphologies influences on the mechanical properties. The CF-PA was found to offer superior strength, ductility, and toughness because of their close-packed ordered lamellar matrix morphology, while the CF-ABS was found to offer superior modulus because of their loose morphology which more easily rearrange in reaction to stress upon elastic deformation. The mechanical properties results were reinforced by the fracture failure modes and the thermal analysis results which showed the CF-PA composite’s ability to withstand higher mechanical performance and temperatures before failure.
With initiatives on carbon capture utilization, use of CO2 in the manufacture of foamed polymers is valuable. The low solubility and strong temperature/pressure correlation to utilization remains a limit. Here we explore two aspects of green manufacturing. Use of a biopolymer and CO2 to foam it. Microcellular foams were produced from amorphous polylactic acid (PLA) with 12% d-lactide content using the batch foaming method. The batch method produces foams that are affected by cell nucleation, growth and solidification. In the thermal soak method, CO2 was introduced into PLA above its Tg, depressurized resulting in solidification, followed by soaking in a hot water bath for trapped CO2 to be released. In a second method, CO2 injected above the Tg was held at a temperature above ambient to encourage cell growth followed by a quench. The results showed that foams made through the decompression technique at foaming temperature of 55 °C were rigid in nature and had a better mix of cellular architecture due to their well-defined bimodal cellular structure compared to the foams made at foaming temperature of 75° C. Excellent mechanical and good sound absorption properties were attributed to the bimodal distr. Thermal conductivity values of (0.031–0.063) W/mK obtained for the PLA foams made using the thermal soak and decompression techniques was equivalent to that of petroleum based extruded polystyrene (EPS) and expanded polystyrene (XPS) foams ∼ (0.03–0.06) W/mK valuable for building insulation.
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