Effect of clay minerals on the flame retardancy of polylactic acid/ammonium polyphosphate system

Abstract

The overview of the literature reveals the lack of comprehensive study on the effect of clay minerals in flame-retarded polylactic acid (PLA) composites. This research focuses on sepiolite (SEP) and montmorillonite (MMT) clay minerals and their impact on ammonium polyphosphate (APP)-based intumescent flame-retardant (IFR) system in PLA. The effects of the clay mineral types, their surface modification (O-SEP and O-MMT, respectively) and their concentration in PLA/APP composites on the flame-retardant properties were comprehensively evaluated through thermal and flammability tests. Overall, the sepiolite-containing samples showed the greatest decrease in pHRR and THR values at the 3 m/m% loading level. The sepiolites showed stronger interfacial interactions with the PLA matrix than the montmorillonites, and the organomodification proved to improve the compatibility of both types of clay minerals according to the dynamic mechanical analysis (DMA) results. Yet, the organomodification had a contradictory effect on the flame-retardant properties. In the case of sepiolites, it proved to be beneficial as the O-SEP added composite achieved a 60% decrease in the pHRR value and reduced the THR value to 60%. For montmorillonites, the improved compatibility by the organomodification with the PLA matrix seemed to hinder its flame-retardant effectiveness, as the critical point to its flame-retardant mechanism is the rapid migration and accumulation of the clay minerals towards the surface of the polymer.

Biopolymers-Clay Nanocomposites: Synthesis Pathways, Properties, and Applications

“…Drug delivery [77][78][79], tissue engineering [80][81][82][83][84][85][86], flame-retardant [87][88][89][90][91][92], wastewater treatment [93][94][95][96][97][98], environment [99,100], food packaging [101][102][103][104][105], and antibacterial activity [37,65,106,107] are just a few of the many high-tech sectors that utilise biopolymer/clay composites (Table 1). Moreover, these materials exhibit biodegradability and safety.…”

Flame Retardancy and Smoke Suppression of Silicone Rubber Foam with Microencapsulated Sepiolite and Zinc Borate

“…In its structural unit, the silicon-oxygen tetrahedron and magnesium-oxygen octahedron alternate with each other, with the transitional structure characteristics of layer and chain [21]. Sepiolite (SEP) appeared the demonstrated excellent flame retardancy as a flame retardant from numerous research results [22][23][24][25][26][27]. SEP could significantly enhance the stability of the carbon layer and improve the flame retardancy of silicone rubber [28].…”