Durable flame-retardant, strong and tough epoxy resins with well-preserved thermal and optical properties via introducing a bio-based, phosphorus-phosphorus, hyperbranched oligomer

• Published in: Polymer degradation and stability Vol. 207; p. 110235
• Main Authors: Ye, Guofeng, Huo, Siqi, Wang, Cheng, Song, Pingan, Fang, Zhengping, Wang, Hao, Liu, Zhitian
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2023
• Subjects: Durable flame retardancy; Epoxy resin; Hyperbranched oligomer; Mechanical properties; Phosphorus-phosphorus synergism; Epoxy resin; Mechanical properties; Hyperbranched oligomer; Durable flame retardancy; Phosphorus-phosphorus synergism
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2022.110235

•A bio-based, phosphorus-phosphorus, hyperbranched oligomer (DIT) was synthesized.•DIT enabled EP to achieve durable fire safety.•DIT significantly improved mechanical robustness and toughness of EP.•DIT well maintained high transparency and thermal resistance of EP. The manufacture of transparent, durable fire-safe, strong yet tough epoxy resins (EPs) remains a great challenge. Herein, a novel hyperbranched, P-P synergetic, bio-based flame retardant (DIT) was synthesized, which was composed by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), bio-derived itaconic anhydride (ITA) and trihydroxymethylphosphine oxide (THPO) moieties. Adding 2 wt% DIT enabled the EP/2DIT sample to achieve a UL-94 V-0 rating and a limiting oxygen index (LOI) of 36.6%. The peak heat release rate and total smoke production of EP/4DIT sample with 4 wt% DIT were 23.8% and 19.9% lower than those of virgin EP sample. Notably, the EP/DIT sample featured durable flame retardancy because of the oligomeric structure of DIT. The high flame-retardant efficiency of DIT was mainly due to the synergism between DOPO and THPO. DIT simultaneously strengthened and toughened EP thermoset at a low addition (≤2 wt%), and 2 wt% of DIT increased the elongation at break, tensile strength, flexural strength and impact strength of EP/2DIT sample by 35.8%, 40.5%, 24.2% and 21.2%. Moreover, the glass transition temperature (Tg) of EP/2DIT sample was equal to that of EP sample, and the high transparent was maintained. Hence, this work offers an all-rounded design for the creation of durable flame-retardant EPs with superior mechanical properties, thermal resistance and transparency by introducing hyperbranched, P-P, bio-based flame retardants, which shows huge potential and broad prospect. [Display omitted]