Ultra-light polylactic acid/combination composite foam: A fully biodegradable flame retardant material

Area of Science:

• Materials Science
• Polymer Chemistry
• Fire Safety Engineering

Background:

• Polylactic acid (PLA) is a biodegradable polymer with limited flame retardancy.
• Existing flame retardants often require high loading or lack synergistic effects.
• Developing effective and efficient flame retardant systems for PLA is crucial for its wider application.

Purpose of the Study:

• To develop a novel, low-density flame retardant system for polylactic acid (PLA) foams.
• To investigate the synergistic effects of lignin fiber (LF), ammonium polyphosphate (APP), resorcinol bis(diphenyl phosphate) (RDP), and SiO2 aerogel in PLA composites.
• To evaluate the flame retardancy and thermal stability of the prepared PLA foams.

Main Methods:

• Preparation of low-density PLA flame retardant foams using a combination of LF, APP, RDP, and SiO2 aerogel.
• Supercritical foaming technique was employed for foam preparation.
• Evaluation of flame retardancy using UL-94 vertical combustion test and limiting oxygen index (LOI) measurements.
• Assessment of thermal stability through thermogravimetric analysis (TGA).

Main Results:

• Individual components (LF, RDP, SiO2 aerogel) showed limited flame retardant effect on PLA.
• Ammonium polyphosphate (APP) required high addition levels for significant flame retardancy.
• The synergistic combination of LF/APP/RDP/SiO2 aerogel significantly improved flame retardancy at lower addition levels.
• The developed PLA flame retardant foam achieved a V-0 rating in UL-94 tests and an LOI of 30.5%.
• The intumescent system formed a dense carbon char layer, enhancing thermal stability and reducing weight loss.

Conclusions:

• A synergistic flame retardant system comprising LF, APP, RDP, and SiO2 aerogel was successfully developed for PLA foams.
• This system effectively enhances flame retardancy and thermal stability of PLA.
• The prepared low-density PLA foams exhibit excellent fire safety performance, meeting stringent V-0 rating requirements.