A novel polymer/kaolinite nanocomposite based on polyurethane-imide (PUI) foams was prepared by in situ polymerization. The PUI foams were synthesized via the reaction between isocyanate terminated polyimide prepolymers and polyether polyol. The kaolinite was modified with an intercalating agent of potassium carbonate. XRD analyses of the intercalated kaolinite and the PUI/kaolinite nanocomposite foams indicate that both intercalated and exfoliated structures are formed. The cell structure, cell size distribution, thermal stability and mechanical properties of the PUI/kaolinite nanocomposite foams are characterized by SEM, TG and an electronic universal testing method. Kinetics of thermal degradation and thermal aging life of the nanocomposite foams are investigated and forecasted compared with those of the pure PUI foams. The results show that addition of the kaolinite significantly improves the heat resistance and mechanical properties. However, the functional groups of PUI foams don't change obviously. View Article Onlinekaolinite. It can be seen that the mean cell size of nanocomposite foams decreases rstly and then increases with increased contents of intercalated kaolinite. When the content of intercalated kaolinite is of 5 wt%, the mean cell size reaches the minimum value (0.70 mm). As the content further increasing to 7 wt% and 9 wt%, the mean cell sizes increase to Fig. 4 SEM micrographs and cell size distributions of PUI/kaolinite nanocomposite foams: (a) 1 wt% Kao-KAc, (b) 3 wt% Kao-KAc, (c) 5 wt% Kao-KAc, (d) 7 wt% Kao-KAc, (e) 9 wt% Kao-KAc. 53214 | RSC Adv., 2015, 5, 53211-53219 This journal is

Phthalonitrile resin/exfoliated hexagonal boron nitride ( h-BN) composites with high thermal conductivity were fabricated using a novel approach. The route included two steps, micro- h-BN was coated and dispersed by phthalonitrile monomers via the function of heterogeneous nucleation, and then micro- h-BN was exfoliated by heat release during the phthalonitrile curing process. The composites achieved a high thermal conductivity of 0.736W (m·K)−1 containing 20 wt% micro- h-BN, which is 3.17 times higher than that of pure phthalonitrile resin at 0.232W (m·K)−1. Compared to traditional routes, the novel preparation approach requires less BN fillers when improving the same thermal conductivity. Importantly, other thermosetting polymers can also encapsulate BN through this strategy, which paves a new way for preparing thermally conductive thermosetting polymer–matrix composites.

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Fluoropolymers find applications in heat‐resistant cables, chemical‐resistant linings, electronic components, cladding materials, and weather‐resistant films. Therefore, it is imperative to improve their temperature resistance level and dielectric properties. In this study, a series of new fluorinated epoxy‐phthalonitrile resins with different mass ratios were prepared by adding phthalonitrile to the epoxy resin matrix, followed by a two‐step reaction of the amine with the epoxy resin at low temperature, and then by the reaction of the nitrile with the epoxy resin and the nitrile group at high temperature. The thermal stability and thermal oxidation stability of the cured products were improved; the initial decomposition temperature for 5% weight loss in air was 375.3°C, indicating good heat resistance performance. In addition, the glass transition temperature and storage modulus of the fluorinated epoxy‐phthalonitrile resins cured products increased with an increase in phthalonitrile content. The storage modulus remained above 1500 MPa until 150°C. The glass transition temperature of fluorinated epoxy‐phthalonitrile resins (at a mass ratio of 5:5) was 180°C, much higher than that of the epoxy resin (which was 140°C). Moreover, the dielectric constant of fluorinated phthalonitrile‐epoxy resin (5:5 mass ratio) was 2.01, which was 39.63% lower than that of fluorinated epoxy resin. The thermoset matrix has potential applications in the fabrication of a variety of low dielectric constant composites for electronic device related industries.

Polylactic acid (PLA) is a biodegradable plastic that currently has limited application owing to its poor fire resistance and brittleness. Herein, a multifunctional silicon‐phosphorus acrylic resin(P/Si‐ACR) is designed to endow both flame retardancy and toughness to PLA. P/Si‐ACR is prepared by seeded emulsion polymerization with polysiloxane as the core layer and diethyl methylphosphonate acrylate and 9, 10‐dihydro‐9‐oxa‐10‐phosphophenanthrene‐10‐oxide acrylate as the shell materials. P/Si‐ACR has a particle size of approximately 200 nm and glass transition temperatures of −38 and 152°C for the core and shell layers, respectively. Addition of 7 wt% P/Si‐ACR to PLA increases the notched impact strength and elongation at break by 124% and 46%, respectively. This improved mechanical performance is due to the elasticity of silicone rubber and the promotion of crystallization by P/Si‐ACR. Combustion testing revealed that the limiting oxygen index increases from 19.1% to 22.5%, while the peak heat release rate decreases by 36%. This enhanced flame retardancy is due to the synergistic effect of phosphorus and silicon, with the former promoting graphitization and inhibiting the free radical degradation of PLA, and the latter stabilizing the char residue. Therefore, P/Si‐ACR is a promising multifunctional modifier that can achieve an optimal balance among flame retardancy, crystallization performance, and toughness in polymers.

To improve the processability of biphenyl phthalonitrile resin, a flexible siloxane structure was introduced into the phthalonitrile monomer through molecular design, which was then blended with a biphenyl monomer to prepare phthalonitrile alloy resins. When the ratio of phthalonitrile monomer containing flexible siloxane to biphenyl phthalonitrile monomer was 1:1, the processing window widened from 58 to 110°C, as compared to that of biphenyl phthalonitrile. Due to the introduction of the biphenyl structure into the phthalonitrile alloy resins, the initial decomposition temperature of the silicon-containing phthalonitrile resin increased from 385 to 516°C. More importantly, the phthalonitrile alloy resin exhibited a high bending strength (66 MPa) and bending modulus (3762 MPa), indicating that it could be potentially applied as high temperature structural composite matrices. Furthermore, it provides a new strategy for processing phthalonitrile resins with a high melting point and narrow processing window.