This study aims the synthesis of copolymers of poly (l-lactic acid) and polycaprolactone by ring opening polymerization. The reactions between l-lactide (LLA) and ε-caprolactone (CL) monomers, in 100/0, 95/5, 90/10 and 80/20 LLA/CL mass ratios, were conducted in refluxing toluene, using Stannous octoate as iniciator, methanol as co-iniciator and inert atmosphere (N 2 ). The reaction medium was maintained under stirring at 120 °C for 24 hours. The samples were characterized by carbon-13 and proton nuclear magnetic resonance (C 13 -NMR and H 1 -NMR), and gel permeation chromatography (GPC). Monomers were characterized by thermogravimetry (TG). Copolymers were formed only in samples containing 20 wt% ε-caprolactone. NMR spectra of the other samples showed no evidence of CL units. This fact may be associated with the low-temperature volatilization of monomers. The GPC analysis showed that the increase of CL concentration decrease the molecular weight of copolymers.
In this study we evaluated the effect of the addition of hydrophilic and hydrophobic silica nanoparticles on the electrical properties of polyhexahydro‐s‐triazine (PHT), a new chemically recyclable thermoset produced from 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane and paraformaldehyde. Chemical recycling as well as thermal and mechanical properties were also investigated. Regarding the electrical properties, electrical conductivity near 10−8 S m−1 at 100 Hz and dielectric constant close to 4.00 at 1 kHz were observed for neat PHT polymer. Better results for electrical properties were observed with the addition of hydrophobic silica nanoparticles. After the addition of the highest concentration (4.5 wt%) the dielectric constant increased about 8% at 1 kHz. Concerning the thermal properties, PHT polymer exhibited a glass transition temperature (Tg) of 185 °C. The addition of hydrophilic or hydrophobic nanoparticles into the neat matrix did not lead to significant variations of thermal properties, but Tg values were decreased compared to the neat resin. Additionally, for mechanical properties, values of reduced modulus (4.58 GPa) and nanohardness (0.38 GPa) were observed. Besides, for all nanocomposites, there was an increase in the reduced modulus for all samples studied. Finally, the chemical recycling of both neat polymer and all nanocomposites after acid treatment was successfully characterized via NMR analysis. © 2021 Society of Industrial Chemistry.
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