Preparation of Flame‐Retardant Reinforced Recycled PBT Building Materials Suitable for Hygrothermal Environments: Flame Retardancy and Hygrothermal Resistance Improvement via Aluminum Phosphite/Paragonite Synergy

Glass fiber‐reinforced flame‐retardant PBT (FR‐GF/PBT) is widely used in various insulating, structural, and flame‐retardant components for building electrical applications. Many of these components are used in hygrothermal environments. To reduce the performance degradation of FR‐GF/PBT under hygrothermal conditions, a series of GF‐PBT composites were prepared by melt extrusion using recycled poly(butylene terephthalate) (R‐PBT) as the matrix, glass fiber (GF) as the reinforcement, aluminum phosphite (Al‐P) as the flame retardant, and Paragonite (Pgt) as the functional additive. The effects of Pgt and Al‐P on the flame retardancy, thermal properties, and mechanical properties of the GF‐PBT composites were investigated. The results showed that Al‐P could effectively improve the flame retardancy of GF‐PBT but caused significant reductions in the strength, toughness, and thermal stability of the composite. Al‐P and Pgt exhibited a synergistic flame‐retardant effect in GF‐PBT, and Pgt improved the mechanical and thermal properties of the composites. Pgt could effectively reduce the degradation of flame retardancy and mechanical properties of GF‐PBT/Al‐P/Pgt composites under hygrothermal environments. This work provides a novel strategy for preparing flame‐retardant reinforced PBT building materials with excellent comprehensive properties for applications in hygrothermal environments.