Biobased Lignin as a Sustainable Flame Retardant Additive for Recycled Polyester Fabrics

Area of Science:

• Materials Science
• Textile Chemistry
• Sustainable Chemistry

Background:

• Recycled poly-(ethylene terephthalate) (rPET) textiles are challenging to finish with flame retardants due to their hydrophobic nature and tendency to melt-drip.
• Existing flame-retardant treatments often struggle with durability and environmental impact.

Purpose of the Study:

• To develop a sustainable, halogen-free flame-retardant coating for rPET textiles.
• To investigate the efficacy of incorporating biobased lignin into flame-retardant systems.

Main Methods:

• A novel coating system was formulated using aluminum diethylphosphinate, biobased lignin, sericin, poly-(vinyl alcohol), and citric acid.
• The coating was applied to rPET fabrics, and flame retardancy was assessed using Limiting Oxygen Index (LOI) and UL 94 tests.
• Durability was evaluated through multiple laundering cycles, and mechanical properties were also assessed.

Main Results:

• Incorporating just 1% lignin in the coating achieved a high LOI of 37.5% and UL 94 V-0 rating.
• The treated rPET fabrics maintained flame retardancy after five laundering cycles and exhibited self-extinguishing behavior.
• Lignin promoted char formation and suppressed melt dripping, enhancing overall flame retardancy without compromising mechanical integrity or hydrophobicity.

Conclusions:

• A low loading of lignin (1% owf) is sufficient for effective flame retardancy in rPET textiles using a phosphorus-nitrogen coating.
• This sustainable coating system offers a viable solution for improving the safety and performance of recycled textiles.