Comparison of different flame‐retardant agents for polylactic acid/fiber composites by a film‐stacking method: Flame‐retardant performance and mechanical properties

In this work, the flame retardant ISA‐APP, obtained by modification of ammonium polyphosphate (APP) with isopropanolamine (ISA), was employed in epoxy resins (EP) in an attempt to enhance the fire resistance of EP. The findings indicate that, with an incorporation of 20 wt% ISA‐APP in the EP, the limiting oxygen index (LOI) of EP/ISA‐APP attains 33.5%, accompanied by a UL‐94 test V‐0 rating. This performance surpasses the flame retardancy observed in EP/APP composites at equivalent content. The outcomes derived from the cone calorimeter test (CCT) demonstrate that EP/ISA‐APP significantly suppresses the release of heat, generation of smoke, and emission of noxious gas during EP/ISA‐APP combustion. The peak‐heat release rate (pHRR) and total heat release (THR) of EP/ISA‐APP are decreased by 74.4% and 63.6%, respectively, compared to pure EP. Further analysis of the char residues of EP/ISA‐APP shows that the POC structure generated during combustion effectively contributes to a high‐quality char layer formation. This investigation presents a viable approach for enhancing flame retardant and economic benefits of APP and advancing the development of highly effective flame retardants.

Isopropanolamine‐modified ammonium polyphosphate for improved flame retardancy of epoxy resin

Zou,

Shi,

Cui

et al. 2024

Construction of a hydrophobicity, phosphorus‐ and nitrogen‐containing layered double hydroxides‐based synergistic effect flame retardant for poly (lactic acid)

Wang,

Gao,

Zhang

et al. 2024

In this work, a synergistic effect strategy was explored for fabricating hydrophobicity, phosphorus‐ and nitrogen‐containing layered double hydroxides nanosheets (LDHs) based flame retardant (LDHs‐K@DM). This fabricating process was achieved by amination of the surface of LDHs and, subsequently, interfacial self‐assembly with high P content of diethylenetriaminpenta (methylene‐phosphonic acid) (DTPMP) and high N content of melamine (MEL). The chemical construction and thermal stabilization properties of LDHs‐K@DM were confirmed via different characterization approaches. The results revealed that LDHs‐K@DM was successfully prepared and the surface of LDHs‐K@DM was transformed into hydrophobicity with high water contact angle. Moreover, LDHs‐K@DM had better thermal stability. After that, LDHs‐K@DM was molten compounded with biobased polylactic acid (PLA). It was suggested that LDHs‐K@DM were uniformly dispersed in the PLA matrix and could accelerate the decomposition of PLA to form char residues. Most importantly, the addition of 20 wt% LDHs‐K@DM into PLA can endow the composite to achieve a desirable UL‐94 V‐0 rating and the limiting oxygen index value of 30.9%. Finally, the synergistic effect flame retardant mechanism of LDHs‐K@DM was comprehensively analyzed. This synergistic decorating strategy for preparing LDHs‐K@DM flame retardant is promising for industrial production.

Mechanical Properties and In Vitro Degradation Study of Modified‐Polylactic Acid Block Copolymers/Polyetheretherketone Biocomposites

Shi,

Zhu,

Lin

et al. 2024

Polylactic acid (PLA) plays a crucial role in addressing global environmental concerns, particularly the challenges of achieving carbon peak and neutrality goals. Polyetheretherketone (PEEK) has emerged as a potential orthopedic implant material due to its excellent mechanical properties, elastic modulus similar to human bone, wear resistance, and good biocompatibility. In this study, PEEK/PLA (PEEK/PLA) composites were prepared using a film‐casting method. PEEK exhibits a spherical structure and can be dispersed in the PLA matrix, demonstrating good compatibility with PLA. Additionally, PEEK acts as a heterogeneous nucleating agent, reducing the surface free energy barrier for the crystallization nucleation of PLA molecules and promoting PLA crystallization. When the PEEK content is 8%, the tensile strength and Young's modulus of the composite material increase by 15.45% and 91.23%, respectively, compared to pure PLA. Furthermore, the introduction of the copolymer (PCxLyA) not only improves the compatibility between PLA and the blend but also successfully regulates the mechanical properties and in vitro degradation of the composite by adjusting the ratio of ε‐caprolactone and L‐lactide in the copolymer. This study not only delves into the modification strategies and methods for PLA composites but also provides new insights for developing biomedical materials with excellent properties.