The objective of this study was to valorize a microbial oil (FDR) with a composition akin to vegetable oils and a degree of unsaturation (»130 g I2/100 g) typical of semi-drying vegetable oils (e.g., soybean, corn, and sunflower oils). Considering this, it was deemed appropriate to apply the methodologies used for epoxides and polyols synthesis from vegetable oils commonly employed in condensation polymers (e.g., polyurethanes, polyhydroxyurethanes, and polyesters) production. A set of experiments using a two-step mechanism was performed starting with epoxide production (oxirane ring formation from C=C bonds) with in situ performic acid followed by insertion of -OH groups (polyol synthesis) by oxirane ring-opening with phosphoric acid or glycerol. Two epoxides were obtained (4.6 % of oxirane content) with reagent ratio FDR: HCOOH: H2O2 = 100:6:160, one from crude FDR at 60 ºC for 4 h, and another one after treatment by winterization (FDRw) at 85 ºC for 3 h with improved color, and lower viscosity. From those epoxides were produced two polyether polyols, UPT (f = 4.0, -OH = 82.3 mg KOH/g ) and JG (f = 8.9, -OH = 265.3 mg KOH/g), and one polyester polyol KCO obtained melting epoxide with castor oil (f = 5.5, -OH = 104.2 mg KOH/g). In a proof-of-concept, polyurethane rigid (PUR) foams with MDI (diisocyanate) were prepared, integrating the FDR-based polyol (UPT) in the backbone, and sugarcane bagasse ash (SCBA, 4.5 %) used by its high content in silica for added fire-retardant properties. Comparing with reference foam without ash (PF), the analysis of structure and thermo mechanical properties indicated that ash particles acted as nucleating points with no chemical interaction, reducing foam’s density (PF, 134.7 kg/m3 ; PFA, 105.7 kg/m3 ), cell's size (PF, 496 nm; PFA, 480 nm), and thermal conductivity (PF, 0.0482 W/m·K; PFA, 0.0461 W/m·K). The added plasticizing effect increased the polymer chain mobility, thus decreasing the glass transition (Tg) temperature (PF, 74.0 ºC; PFA, 71.8 ºC) and delaying the decomposition onset temperature (Td) (PF, 215 ºC; PFA, 230 ºC). The flammability test results suggest that SCBA has improved the foam performance in compliance with the fire protection standard UL 94, class HB. To remove the toxic isocyanates from that equation the safer route was to prepare non isocyanate polyurethanes (NIPUs) and their hybrids (HNIPUs). Two methods were explored (cycloaddition of CO2 to epoxide and transcarbonation with polyol JG) for cyclic carbonates synthesis (the monomeric units). The result of the latter was a hard HNIPU, with lower gel content (6.8 %) and Tg (60.6 °C) comparing with the glycerol-based reference (gel = 80.0 % e Tg = 106.8 ºC), though harder and with higher melting temperature, Tm (171.6 ºC vs 147.9 ºC) mainly due to wax crystals content. Using polyols KCO and UPT (from FDRw), were prepared two polyesters (KCO and UPT) with elastomeric properties, low Young’s modulus (1.92 × 10-3 and 3.9 MPa) and elongation up to 150 ad 185.4 %, respectively. Polyester KCO, was tailored for controlled release of active principles for wound dressing applications, with proved skin biocompatibility and degradability, hydrophilic character, low Tg (−51.2 ◦C), and high Tm (169.8 ◦C). The second (UPT) showed an amorphous structure and shape memory behavior between - 47 and 12 °C, apt for low-temperature applications where it is required to maintain the mechanical integrity of components, eventually subjected to large deformations during service conditions. Applying the same principles of sustainability and circularity to the building and construction (B&C) industry, an experimental campaign was envisioned integrating FDRw and SCBA into cementitious mortars to ultimately enhance the hygrothermal properties in 3 D impressed specimens. Thermal conductivity (λ), water absorption by capillary action (Aw), and in saturated state the moisture content (Wsat), and water absorption (Ab) were determined in cured specimens. The variation found when comparing the results for specimen containing only FDRw 1% (λ = 1.493 W/m·K, Aw = 0.048 kg/m2 . s0.5, , Wsat = 53.47 kg/m3 , and Ab = 2.58 %), and reference (λ = 1.411 W/m·K, Aw = 0.045 kg/m2 . s0.5 , Wsat = 36.15 kg/m3 , and Ab = 1.74 %) suggests that pore distribution, pore size and interconnectivity are driving factors inducing inner defects and major voids partially filled by the presence of SCBA (Mix SCBA/ FDRw = 5/1) improving the mortar’s hardened properties (λ = 1.382 W/m·K, Aw = 0.041 kg/m2 . s0.5 , Wsat = 41.43 kg/m3 , and Ab = 1.99 %).
Date of Award | 29 Jan 2024 |
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Original language | English |
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Awarding Institution | - Universidade Católica Portuguesa
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Supervisor | Ana Lúcia Silva Oliveira (Supervisor) & Ana Sofia Moreira dos Santos Guimarães Teixeira (Co-Supervisor) |
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