Synthesis of aromatic-aliphatic polyamide acting as adjuvant in polylactic acid (PLA)/ammonium polyphosphate (APP) system

A potential adjuvant for polylactic acid (PLA)/ammonium polyphosphate (APP) system, a novel polyamide (PA) containing aromatic and aliphatic groups, was synthesized from a polycondensation reaction of adipic acid with 4,4-diaminodiphenyl sulphone. The synthesized PA was characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance (H-1 NMR, C-13 NMR), size exclusion chromatography (SEC) and thermogravimetric analysis (TGA), respectively. As a potential adjuvant, this PA has been used in a PLA system combined with and without APP in order to investigate the flame retardancy. The flammability of PLA and PA are studied by microscale combustion calorimeter (MCC). The flame retardant properties and thermal decomposition behaviors of PLA-PA composites were investigated by cone calorimeter test (CCT) and TGA, respectively. In the presence of APP, in some extent PA shows a synergistic effect on improving the flame retardancy of PLA composites at the fixed mass ratio 2:1 of APP and PA, reflecting delayed time to ignition (TTI) and slight decrease in the peak heat release rate (pHRR) in the cone calorimeter test. In order to further improve the flame retardancy, 1wt% clay was introduced to the PLA-PA-APP system while the total loading of additives kept at 15 wt%. The results of PLA-PA-APP-clay composite from cone calorimeter test showed significant decrease in heat release rate (HRR), total heat release rate (THR) and total smoke release (TSP). (C) 2013 Elsevier Ltd. All rights reserved.