An effective flame retardant containing hypophosphorous acid for poly (lactic acid): Fire performance, thermal stability and mechanical properties. (September 2019)

• Record Type: Journal Article
• Authors: Wang, Xingguo; Sun, Jun; Liu, Xiaodong; Jiang, Shengling; Wang, Julin; Li, Hongfei; Bourbigot, Serge; Gu, Xiaoyu; Zhang, Sheng
• Is Part Of: Polymer testing. Volume 78(2019)
• Publication Date: 2019-09
• Subjects: Poly (lactic acid) -- P/N-containing flame retardant -- Flammability\; Polymers -- Testing -- Periodicals; Polymères -- Tests -- Périodiques; 620.1920287
• DOI: 10.1016/j.polymertesting.2019.105940
• Languages: English
• ISSNs: 0142-9418

Abstract

Abstract: An effective flame retardant N, N′-bis [salicylidene hypophosphorous acid]-1, 2-ethylenediamine (SHPE) was synthesized by a Kabachnik-Fields reaction between hypophosphorous acid and a Schiff base compound. The chemical structure was confirmed by FTIR, 1 HNMR and organic element analysis. SHPE was melt blended with poly (lactic acid) (PLA) matrix to enhance the flame retardancy. Fire behavior evaluation of PLA composites indicated that the presence of 10 wt% SHPE increased the LOI value up to 28.3%, developed the UL-94 grade to V-0 rating, and significantly decreased the peak heat release rate (pHRR) and total heat release (THR) of PLA composites. The analysis of X-ray photoelectron spectroscopy (XPS), FTIR, Raman spectrum and scanning electron microscope (SEM) demonstrated that SHPE exerted flame retarding effect in both gas and condense phases. It was proposed that the presence of SHPE catalyzed random chain scission of PLA, and accelerated the formation of melt dripping to take away heat during combustion. The elongation at break of PLA/SHPE composites were increased compared with that of PLA. The compatibility of SHPE and APP in PLA was also compared. Graphical abstract: Image 1 Highlights: The novel P/N flame retardant SHPE was synthesized and characterized. The fire performance of PLA was improved by the presence of SHPE. The released inert gas and polyphosphoric acid are beneficial to form intumescent char layer. The PLA sample reached V-0 grade in UL-94 test by the presence of 5% SHPE. The introduction of SHPE improved the elongation of PLA.