Reactive extrusion of PLA and of PLA/carbon nanotubes nanocomposite: processing, characterization and flame retardancy

Abstract

Aliphatic polyesters such as polylactide (PLA) currently deserve particular attention in the area of environmentally degradable polymer materials. PLA is produced via polymerization of renewable products, namely lactic acid or lactide. In this work, the synthesis of PLA is done by reactive extrusion via ring opening polymerization of L,L-lactide using a continuous single-stage process which is a fast and an easy method. The resulting PLA is fully characterized by solid state NMR. It is shown that it exhibits properties similar to those of PLA synthesized by the traditional methods. A kinetic model based on a phenomenological approach permits one to describe the polymerization of L,L-lactide. PLA nanocomposites containing multi-wall carbon nanotube (MWNT) are also prepared by reactive extrusion. Reaction to fire of PLA nanocomposite shows a slight improvement of the flame retardancy. The nanodispersion characterized by transmission electronic microscopy (TEM) is acceptable but should be improved to obtain the best flame retardancy.

Effect of imidazolium phosphate and multiwalled carbon nanotubes on thermal stability and flame retardancy of polylactide

“…Continuous layers of network-structured carbon can be formed to significantly reduce the heat release rate since the layers can act as thermal shields to avoid energy feedback of the flame [11][12][13][14]. This had been demonstrated in the flame retardance studies about polypropylene (PP)/CNTs [11], polymethyl methacrylate (PMMA)/CNTs [12], PLA/CNTs [13,14] composites, etc. One of the major challenges was then to evenly disperse CNTs in the polymeric matrix to get the best flame retardancy properties [15].…”

Polylactic Acid (PLA) Carbon Nanotube Nanocomposites

“…Reaction to fire of PLA/MWCNT nanocomposites indicated a slight improvement of the flame retardancy in Bourbigot et al's study, and the nanodispersion could be improved to obtain the best flame retardancy [43]. In another work, the synergic effect of MWCNT and sepiolite nanoclay (Sep) utilization in PLA nanocomposite demonstrated improved flame retardancy as well [44].…”

Flame retarded poly(lactic acid): A review

“…They may work, however, also as potential flame retardants since they may be involved in the development of a thermal insulation layer on the surface of burning material during combustion. Such nanoparticles could be montmorillonite, expandable graphite, halloysite [51], bentonite, carbon nanotubes [52], and sepiolite [53]. Expandable graphite (EG) has low density, and it is non-burnable and capable of insulating the polymer substrate against radiant heat.…”

“…This was attributed to the excellent dispersion of f-MWNT in PLA. PLA/MWNT nanocomposites were prepared by Bourbigot et al [52] by reactive extrusion. They synthesized PLA by ring opening polymerization of L,L-lactide, then mixed in the MWNT in a continuous single-stage process.…”