In this study, a novel phthalonitrile monomer containing pyrimidine ring, 4,6-bis[3-(3,4-dicya-nophenoxy)phenoxy]pyrimidine (BCPM), was successfully synthesized by nucleophilic substitution reaction with resorcinol, 4,6-dichloropyrimidine and 4nitrophthalonitrile. The BCPM monomer was cured by different temperature programs with 4-(aminophenoxy)phthalonitrile (APPH) as catalyst to give the polymers.The molecular structures of the BCPM monomer and the polymers were investigated by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. Differential scanning calorimetric (DSC) analysis was performed to study the processability of the BCPM monomer, which showed a wide processing window of about 117°C. The mechanical properties and thermaloxidative stability of the polymer were characterized by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively, which indicated that the polymers exhibited excellent storage modulus, high glass transition temperature over 400°C, and outstanding thermal stability. The polymers also have low water absorption capacity and are suitable for humid environments.
In this study, a novel phthalonitrile monomer containing a pyridazine ring, 3,6-bis[3-(3,4-dicyanophenoxy)phenoxy]pyridazine (BCPD) with a low melting point (74 °C) and wide processing window (178 °C), was prepared by a nucleophilic substitution reaction. The molecular structure of the BCPD monomer was identified by Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (NMR). Poly(BCPD) resins were derived from the formulations by curing at 350 and 370 °C. The thermoset that was post-cured at 370 °C demonstrated outstanding high heat-resistant (glass transition temperature (Tg) > 400 °C, 5% weight loss temperature (T5%) = 501 °C, Yc at 900 °C > 74%) and was flame-retardant (limiting oxygen index (LOI) = 48)). Further, the poly(BCPD) resin simultaneously exhibited a superior storage modulus, which could reach up to 3.8 Gpa at room temperature. Excellent processability and heat resistance were found for phthalonitrile thermosets containing the pyridazine ring, indicating poly(BCPD) resin could be potentially applied as high-temperature structural composite matrices.
Nano montmorillonite (MMT) was modified by low molecular weight polylactic acid (PLA), then, the PLA modified MMT and raw MMT were added into thermoplastic starch (TPS) to prepare biodegradable nanocomposite films, respectively. For both nanocomposite films with raw MMT and modified
MMT, the Tmax of degradation was enhanced and the mechanical properties were improved. The composite films containing 4 wt.% MMT displayed tensile strength of 5.06 MPa, approximately 1.4 times of that for the pure TPS films. The tensile strength of composite films containing
4 wt.% modified MMT is 6.74 MPa approximately 2 times of those for pure starch films. On the other hand, the composite film containing 4 wt.% modified MMT displayed elongation at break as high as 34.25%, which is 1.3 times of that of the pure starch film, while the composite films containing
raw MMT had reduced elongation at break. This study showed that the MMT modified with PLA could significantly enhance the mechanical properties of TPS, and provides a new method to prepare fully biodegradable starch-based nanocomposites.
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