Wenzong Xu

Natural rubber (NR) and cis‐polybutadiene rubber (BR) are widely used due to their respective advantages, such as high strength, excellent processability, wear resistance, and low‐temperature resistance. However, the high flammability and the toxic smoke released during combustion of these two rubbers limit their application. To address this issue, this study developed a microencapsulated flame retardant named PBEG@Cu, consisting of expanded graphite (EG) as the core and copper ions together with bis[2‐(methacryloyloxy)ethyl] phosphate (BMEP) as the shell. This flame retardant was incorporated into NR/BR composites. Experimental results showed that when the total addition of PBEG@Cu reached 20 phr, the fire hazard of the composite was significantly reduced. The limiting oxygen index increased from 19.6% to 25.3%. Compared with pure NR/BR, the total heat release (THR) and peak heat release rate (pHRR) of the composite decreased by 26.1% and 31.7%, respectively. Furthermore, the maximum smoke density (D _s,max ) dropped by 24.6%, while the thermal conductivity increased by 65.3%. By achieving a synergistic balance among flame retardancy, smoke suppression, and thermal conductivity, it offers new insights for the design of high‐performance rubber composites for applications with stringent fire safety requirements.

Natural rubber (NR) has high elasticity, high tensile strength, and excellent processing performance, but its high flammability limits its application. Adding aluminum diethylphosphinate (ADP) to natural rubber can improve its flame retardancy, but its mechanical properties will be greatly reduced. Therefore, it is still a challenge to improve the flame retardancy of NR while maintaining its mechanical properties. In this study, a new flame retardant synergist mDT@Ni was synthesized, which was compounded with ADP and added with NR to study the effect of the composite system on the flame retardancy and mechanical properties of NR. The results showed that compared with pure NR, the oxygen index of NR composites with 0.75 phr mDT@Ni and 19.25 phr ADP increased from 19.2% to 25.5%, the total heat release (THR) decreased by 21.1%, and the maximum heat release rate (pHRR) decreased by 25.7%. At the same time, its mechanical properties have also been improved; the tensile strength and elongation at break increased by 14.5% and 18.2%, respectively. In addition, the flame retardant mechanism was studied in detail by residual carbon characterization and TG‐FTIR test.

Polyvinyl alcohol (PVA) has superb chemical and physical characteristics, making it important for applications in many areas, but its combustibility limits its broader use. In this work, ZIF‐67@BN, a flame‐retardant and heat‐conducting filler, was synthesized via the in situ growth technique, and its structural and morphological characteristics were studied. ZIF‐67@BN and ammonium polyphosphate (APP) were added to PVA. The findings verify that the LOI value of PVA composites with 1 wt.% of ZIF‐67@BN and 7 wt.% of APP attained 28.1%, which was 36.4% greater than that of pure PVA. In addition, the total heat rate (THR) was 39.0% lower than that of pure PVA, and the peak heat release rate (pHRR) was 61.6% lower. This is because ZIF‐67@BN has a physical barrier effect as a filler and catalyzes the carbonization effect. When heated, APP's decomposition generated non‐flammable gas dilution; at the same time, the production of phosphoric acid and metaphosphoric acid contributed to the dehydration during the carbonization of PVA.

Polyvinyl alcohol (PVA) is a biodegradable, water‐soluble polymer with excellent film‐forming properties, but its flammability severely limits its applications. A key challenge in PVA functionalization research is enhancing flame retardancy of PVA films. It must be achieved without compromising transparency and mechanical properties. This work presents a novel supramolecular flame retardant, DAD@Ni, containing nitrogen, phosphorus, sulfur, and nickel. It is synthesized via ion‐metal ligand coordination and incorporated into PVA to form PVA/DAD@Ni composites. The PVA/10%‐DAD@Ni composite's limiting oxygen index (LOI) increased from 19.0% as in pure PVA film to 32.3% and achieved the ideal UL‐94 V‐0 rating. Meanwhile, its peak heat release rate (PHRR) and total heat release (THR) were reduced by 63.3% and 46.8%. Compared to pure PVA film, PVA/DAD@Ni composites demonstrated excellent UV resistance in the UVA and UVB regions. The investigation revealed that integrating PVA and DAD@Ni, facilitated by a hydrogen‐bonded cross‐linked network, enhanced mechanical properties while preserving optical clarity in composites. This work presents a feasible method for fabricating multifunctional, flame‐retardant, and UV‐resistant materials. The PVA/DAD@Ni composites has potential applications in outdoor protective materials, electronic device packaging, safety protective equipment, and other fields.

Natural rubber (NR) has high strength and excellent processability, and cis‐polybutadiene rubber (BR) has excellent abrasion and low‐temperature resistance, but both NR and BR are highly flammable in air, and it is a challenge to improve the flame retardant properties of NR and BR while maintaining high mechanical properties. In this study, polyaniline (PANI) coated with aluminum diethyl hypophosphite (ADP) was used to form a microencapsulated flame retardant PANI@ADP. The flame retardant was characterized by FTIR, XPS, SEM, particle size analysis, and TGA. PANI@ADP was added to natural NR/BR composites. The results showed: compared with ADP, the limiting oxygen index of NR/BR composites with 15 parts PANI@ADP was increased from 23.5% to 24.7%, and the LOI of NR/BR composites with 20 parts PANI@ADP was 27.4%. The flame retardant mechanism of PANI@ADP was analyzed through the characterization of residual carbon in NR/BR composites. In addition, the addition of PANI@ADP to NR/BR improves the vulcanization properties of the composites and enhances the mechanical properties of the composites compared to ADP. This study enabled the NR/BR composites to maintain high mechanical properties while improving the flame retardant properties.

Natural rubber (NR) has high strength and excellent processing performance, and cis‐polybutadiene rubber (BR) has excellent abrasion resistance and low temperature resistance, but both NR and BR are highly flammable and emit large amounts of smoke. Therefore, it is a challenge to improve the flame retardant and smoke suppression properties of NR and BR while maintaining their high mechanical properties. In this study, metal ion complexed boron phenolic resin (BPF) is used to coat aluminium diethyl hypophosphite (ADP) and adsorb with melamine (MF) to form a microencapsulated flame retardant (FeBADP/MF). The flame retardants are characterized by FTIR, XPS, SEM, EDS, and TGA. The microencapsulated flame retardants are added to NR/BR composites. The results show that the LOI of NR/BR composites with 15 phr of FeBADP/MF is increased from 23.1% to 24.2%, and the maximum smoke density is reduced by 35.1% compared with ADP; and the LOI of NR/BR composites is 27.2% with FeBADP/MF added in the amount of 20 phr. The NR/BR composites were characterized by residual carbon and TG‐FTIR studies to analyze the flame retardant mechanism of FeBADP/MF. It is also found that the addition of FeBADP/MF to NR/BR improves the vulcanization properties of the composites and enhances the mechanical properties of the composites. This study tries to solve the problem of the decreased mechanical properties of NR/BR composites during the improvement of flame retardant and smoke suppression properties, and to provide an important theoretical and experimental basis for the development of high‐performance flame retardant rubber materials.