Lactide-Caprolactone copolymer (LACL) was added to a Polylactide/Poly(ε-caprolactone) (PLA/PCL) blend as a compatibilizer through solution mixing and the casting method. The melt crystallization behavior and crystalline morphology of PLA, PLA/PCL, and PLA/PCL/LACL were investigated using differential scanning calorimeter (DSC) and polarized optical microscopy (POM), respectively. The temperature of the shortest crystallization time for the samples was observed at 105 °C. The overall isothermal melt crystallization kinetics of the three samples were further studied using the Avrami theory. Neat PLA showed a higher half-time of crystallization than that of the PLA/PCL and PLA/PCL/LACL blends, whereas the half-time of crystallization of PLA/PCL and PLA/PCL/LACL showed no significant difference. The addition of PCL decreased the spherulite size of crystallized PLA, and the nuclei density in the PLA/PCL/LACL blend was much higher than that of the PLA and PLA/PCL samples, indicating that LACL had a compatibilization effect on the immiscible PLA/PCL blend, thereby promoting the nucleation of PLA. The spherulites in the PLA/PCL and PLA/PCL/LACL blend exhibited a smeared and rough morphology, which can be attributed to the fact that PCL molecules migrated to the PLA spherulitic surface during the crystallization of PLA.

A nickel-functionalized copper metal–organic framework (Ni@Cu-MOF) was prepared by a facile volatilization method and a post-modification synthesis method at room temperature. The obtained Ni@Cu-MOF electrode delivered a high capacitance of 526 F/g at 1 A/g and had a long-term cycling stability (80% retention after 1200 cycles at 1 A/g) in a 6 M KOH aqueous solution. Furthermore, an asymmetric supercapacitor device was assembled from this Ni@Cu-MOF and activated carbon electrodes. The fabricated supercapacitor delivered a high capacitance of 48.7 F/g at 1 A/g and a high energy density of 17.3 Wh/kg at a power density of 798.5 kW/kg. This study indicates that the Ni@Cu-MOF has great potential for supercapacitor applications.

To expand the use of polylactic acid (PLA) in high-temperature environments, crystallization morphology regulation was studied to enhance the heat resistance of PLA. PLA crystallinity was controlled using heat treatment and nucleating agent (zinc phenylphosphonate, brand TMC). The heat deflection temperatures of PLAs with same crystallinities considerably varied using different treatments. The crystallization morphology of PLA (4032D) and PLA/TMC composites was studied using X-ray diffraction (XRD) and polarized optical microscopy. XRD test results show that TMC can improve the crystallization rate and heat treatment can enhance the crystallinity and thickness of PLA, suggesting that the crystallization morphology improved after heat treatment. Nucleating agents can increase the crystallinity of PLA but cannot improve its crystallization morphology. The findings indicate that at the same crystallinity, PLAs exhibit improved crystallization morphology and high heat resistance; these results can provide guidance for improving the heat resistance of PLAs and facilitate the design of new nucleating agents.

Phenethyl-bridged DOPO derivative (DiDOPO) was combined with graphene nanosheets (GNSs) in epoxy resin (EP) to improve its flame retardancy. The results indicated that the introduction of only 1.5 wt% DiDOPO/1.5 wt% GNS in EP increased the limited oxygen index (LOI) from 21.8% to 32.2%, hence meeting UL 94 V-0 rating. The thermogravimetric analyses revealed that char yield rose in presence of GNSs to form thermally stable carbonaceous char. The decomposition and pyrolysis products in gas phase were characterized by thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR), and the release of large amounts of phosphorus was detected in the gas phase. The evaluation of flame-retardant effect by cone calorimetry demonstrated that GNSs improved the protective-barrier effect of fire residue of EP/DiDOPO/GNS. The latter was further confirmed by digital photography and scanning electron microscopy (SEM). Also, Raman spectroscopy showed that GNSs enhanced graphitization degree of the resin during combustion. Overall, the combination of DiDOPO with GNSs provides an effective way for developing high-performance resins with improved flame retardancy.

Flame-retardant epoxy resin (EP) composites were prepared by the incorporation of a phenethyl-bridged DOPO derivative (DiDOPO) and modified layered double hydroxide (OLDH).

Polypropylene (PP), as a general thermoplastic polymer, is broadly used in different fields. However, the high flammability, melt dripping and poor mechanical properties of PP are a constraint to the expansion of its applications. In this paper, PP composites containing a combination of a phenethyl-bridged DOPO derivative (PN-DOPO) and organic montmorillonite (OMMT) were prepared via melt blending. The synergistic effects of PN-DOPO and OMMT on the flame retardancy, thermal stability and mechanical properties of PP composites were investigated systematically. The results showed that 20 wt% addition of PN-DOPO with OMMT improved the flame retardancy of PP composites. In particular, the introduction of 17 wt% PN-DOPO and 3 wt% OMMT increased the LOI values of the PP matrix from 17.2% to 23.6%, and the sample reached the V-0 level and reduced the heat release rate and total heat release. TGA indicated that OMMT could improve the thermal stability of the PP/PN-DOPO blends and promote the char residues of PP systems. Rheological behaviour showed a higher storage modulus, loss modulus and complex viscosity of PP/PN-DOPO/OMMT composites, suggesting a more effective network structure. In addition, the tensile strength, flexural properties and impact strength of the PP/PN-DOPO/OMMT composites actually increased for a good dispersion effect. Combined with the char layer analysis, the introduction of OMMT promoted more continuous and compact structural layers containing an aluminium–silicon barrier and phosphorus-containing carbonaceous char in the condensed phase. OMMT can improve the flame retardancy, thermal stability and mechanical properties of PP, and, thus, PN-DOPO/OMMT blends can serve as an efficient synergistic system for flame-retarded PP composites.