Wenwen Guo,Xin Wang,Jiali Huang,Wei Cai,Lei Song,Yuan Hu
To overcome the flammability and brittleness of DGEBA, cardanol was selected to synthesize bio-based epoxy in this work because of its unique structure with both rigid aromatic rings and flexible long fatty chains. A novel intrinsically anti-flammable and self-toughened cardanol-derived novolac epoxy was synthesized through condensation, phosphorylation, and epoxidation processes, with a cardanol-based epoxy monomer without phosphorylation (ECF) as a contrastive sample. TGA results showed that the char yield of ECF-PO(OPh) 2 /DDM was much higher than those of DGEBA/DDM and ECF/DDM thermosets due to the catalytic charring effect of phosphate species. The DGEBA/DDM and ECF/DDM thermosets exhibited high flammability, whereas the ECF-PO(OPh) 2 /DDM possessed exceptional anti-flammability. Specifically, the cured ECF-PO(OPh) 2 /DDM possessed a high LOI value of 33.5 % and UL-94 V-0 rating; the PHRR, THR, and TSP values measured by cone calorimeter test were declined by 69.5 %, 28.6 %, and 16.4 % compared to those of the commercial DGEBA/DDM thermoset. Besides, the cured ECF-PO(OPh) 2 /DDM thermoset showed good toughness originated from the long fatty chain of cardanol. This as-synthesized phosphorylated cardanol-derived novolac epoxy possesses simultaneously fire-safe and toughening characteristics, which could be a renewable substitute for commercial DGEBA counterpart to overcome its flammability and brittleness.
Haoxin Niu,Yu Li,Ping Zhang,Wenwen Guo,Xin Wang,Yuan Hu
Due to their excellent properties, thermosetting polymer materials have been widely used in many fields. Owing to the restriction of the crosslinked network, traditional thermosetting polymer materials exhibit insolubility and immiscibility. Therefore, the reprocessing of thermosetting polymer materials is a great challenge. With the depletion of petroleum-based resources, the utilization of natural resources for the preparation of bio-based thermosetting polymer materials is a major trend. In this study, eugenol-based covalent adaptable thermosets were prepared via UV curing and thermal curing according to thiol click chemistry. The mechanical properties of the eugenol-based covalent adaptable thermosets, which are better than those of the control sample, can be regulated according to the components. The eugenol-based covalent adaptable thermosets exhibited excellent transparency and UV shielding properties. The introduction of a dynamic covalent boronic ester (BSH) promoted the formation of residual char and enhanced the fire safety of the eugenol-based covalent adaptable thermosets. Owing to the dynamic borate ester bonds in the cross-linked network, the eugenol-based covalent adaptable thermosets exhibited significant stress relaxation behavior, and excellent shape memory function and self-healing properties. The samples were reprocessed at 100 °C several times. After three cycles of pulverizing and hot pressing, the recovery ratio of tensile strength of the reprocessed samples remained above 85%. This study provides a novel strategy for preparing self-healable, reprocessable and anti-flammable covalent adaptable thermosets with tunable mechanical properties.
Dan Xiao,Meng-Ting Zheng,Fang-Juan Wu,Xiao-Xia Cao,Xing-Fang Huang,Li Huang,Xue-Qing Xiao
Aiming to develop the crystallization and anti-flammability additives for creating high performance PLA, in this paper, a novel multifunctional bio-based furan derivative phenyl P-(N-N'-di-(furan-2-ylmethyl))phosphonamidate (PFPA) is synthesized and then is incorporated into PLA to enhance its comprehensive properties. The low loading of multifunctional bio-based PFPA not only as the nucleating agent increases the crystallinity and crystallization rate for PLA matrix, but also significantly improves anti-flammability properties of PLA. The V-0 classification in UL-94 and LOI result of 30.7 % for PLA with only loading 3 wt% PFPA are achieved. Moreover, the heat release values in cone-calorimeter measurement of PLA/3%PFPA composites are obviously decreased. The anti-flammability mechanism displays that PFPA forms highly-efficient fire-retardant radicals, accelerates heat away, suppresses combustible gases, and enhances stable residual carbon during PLA/PFPA combustion. This work provides a facile and efficient strategy for preparing multifunctional bio-based additives crystallization and fire-safety agent for PLA as well as promises broad application in engineering materials.
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