Development of Inherently Flame—Retardant Phosphorylated PLA by Combination of Ring-Opening Polymerization and Reactive Extrusion

Abstract

In this study, a highly efficient flame-retardant bioplastic poly(lactide) was developed by covalently incorporating flame-retardant DOPO, that is, 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide. To that end, a three-step strategy that combines the catalyzed ring-opening polymerization (ROP) of L,L-lactide (L,L-LA) in bulk from a pre-synthesized DOPO-diamine initiator, followed by bulk chain-coupling reaction by reactive extrusion of the so-obtained phosphorylated polylactide (PLA) oligomers (DOPO-PLA) with hexamethylene diisocyanate (HDI), is described. The flame retardancy of the phosphorylated PLA (DOPO-PLA-PU) was investigated by mass loss cone calorimetry and UL-94 tests. As compared with a commercially available PLA matrix, phosphorylated PLA shows superior flame-retardant properties, that is, (i) significant reduction of both the peak of heat release rate (pHRR) and total heat release (THR) by 35% and 36%, respectively, and (ii) V0 classification at UL-94 test. Comparisons between simple physical DOPO-diamine/PLA blends and a DOPO-PLA-PU material were also performed. The results evidenced the superior flame-retardant behavior of phosphorylated PLA obtained by a reactive pathway.

Flame retardant polymer materials: An update and the future for 3D printing developments

“…The resulting material can be judged indirectly in terms of the homogeneous dispersion of FR agent at molecular level. The chemical modification of polymers, by incorporation of molecules presenting flame-retardant effect within the macromolecular chain [77] is a very promising way to overcome the migration of FR additives [45], and to enable the development of non-opaque flame-retardant materials [78]. Moreover, using a reactive pathway can prevent the deterioration of the polymer's mechanical properties caused by the presence of heterogeneous FR additives, and improve its processability (for example in the production of fibers or films) and transparency.…”

“…All these reactions could be performed by REX. Mincheva et al [77] described a method for developing in-situ flame retardant PLA. In the first stage, a bifunctional DOPO-based diamine was synthesized, then the product was used as an initiator of ring opening polymerization (ROP) of L,L-lactide (L,L-LA) in the bulk, and lastly a bulk chain-coupling reaction was accomplished between the thus-obtained phosphorylated-PLA oligomers and hexamethylene diisocyanate (HDI) through REX.…”

Fire-Safe Polymer Composites: Flame-Retardant Effect of Nanofillers

“…UL 94 testing is also widely used in both industrial and academic research with an aim to categorize polymer materials hierarchically and meet industrial requirements [ 144 , 145 , 146 , 147 , 148 ]. Nevertheless, the information thus obtained is limited due to its basic and unfixed nature.…”

New Insights into Antibacterial and Antifungal Properties, Cytotoxicity and Aquatic Ecotoxicity of Flame Retardant PA6/DOPO-Derivative Nanocomposite Textile Fibers

“…The health and environmental concerns related to the persistent, bioaccumulative and toxic (PBT) halogenated flame retardants stimulated the search for alternative solutions and the development of more sustainable flame retardants [ 1 , 2 , 9 , 10 , 11 ]. Organophosphorus compounds (OP), i.e., organophosphates, organophosphonates, organophosphinates, organoposphine oxide, and organophosphites, are currently being intensively investigated as alternatives to PBT flame retardants due to due the chemical versatility of phosphorus’ different oxidation states and their ability to provide effective flame retardant protection in both the condensed and gas phases [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ].…”