Improving poly(lactic acid) fire performances via blending with benzoxazine

Improving the mechanical performance of PLA via reactive blending with thermosets is an interesting approach, however, not well explored for its fire performance improvement. With our approach, the fire performances of PLA were improved by blending PLA with a commercially available bisphenol-F-based benzoxazine. To establish the proof of concept, the benzoxazine was initially pre-cured at either 100 °C or 150 °C for a pre-selected time i.e. 60′, 80′, or 120′. The benzoxazine samples were then blended with PLA matrix via an extrusion process at 10 wt.% or 20 wt.% loadings. Detailed thermal and chemical investigations via Differential Scanning Calorimetry (DSC) and Size Exclusion Chromatography (SEC), and the evaluation of the mechanical properties, confirmed that the addition of benzoxazine does not influence the intrinsic properties of PLA. The fire performance was tested by Mass Loss Cone (MLC) calorimetry. PLA formulation with 20 wt.% of the benzoxazine cured 80′ at 150 °C, lead to a 43 % reduction of the peak of heat release rate compared to neat PLA. This was attributed to increased char formation during the combustion process. Also, the char formation permits a significant delay in the temperature increase of the sample.