Abstract
Through a straightforward approach, a new meltable, halogen-free, nitrogen-phosphorus-based flame retardant (FR), 6-(2-(4,6-diamino-1,3,5-triazin-2-yl)ethyl) dibenzo[c,e][1,2]oxaphosphinine 6-oxide (DTE-DOPO) was synthesized and incorporated in polyamide 6 (PA6). It was proved that a very low phosphorus content of 1.46 wt% for DTE-DOPO additive improved the flame retardancy of PA6, leading to a non-flammable material. The performance of the new additive was compared to that of the commercially-available Exolit® OP 1230. The PA6 formulations were evaluated by measuring the rheological, mechanical, and flammability behavior. Using compounding by melt extrusion, 17 wt% additives was introduced into PA6 matrix and the corresponding formulations were characterized. The results evidenced a higher homogeneity of DTE-DOPO with PA6, a high thermal stability with a catalyzing decomposition effect on PA6 caused by the presence of the new developed FR, enhanced elasticity for the PA6/DTE-DOPO formulation and a V0 rating for both formulations. Thermal and fire analysis indicated a primary gas-phase activity, combined with a complete suppression of the self-sustained burning for the PA6/DTE-DOPO formulation.
Highlights
Polyamide 6 (PA6) is one of the most important engineering plastics which has been widely used in advanced technologies including electronic industries, telecommunications, and automotive production.Despite its attractive properties, the use of polyamide 6 (PA6) is still restricted in many applications where fire safety is important because of its inadequate flame retardance and severe flammable dripping [1]
Along with the observations obtained from the pyrolysis combustion flow calorimetry (PCFC) and thermogravimetric analysis (TGA) measurements, namely a decrease value of total heat release and a comparable thermal stability, it can be inferred that the enhanced flame resistance of the DTE-DOPO flame retardant (FR) additive may be mainly due to a gas-phase activity
A new meltable, halogen-free, triazine-DOPO (DTE-DOPO)-based flame retardant for PA6 was synthesized, characterized and its flame retardant efficiency was compared with a non-meltable
Summary
Polyamide 6 (PA6) is one of the most important engineering plastics which has been widely used in advanced technologies including electronic industries, telecommunications, and automotive production. One source of difficulty relates to their application in polyamides, i.e., the use of high processing temperatures, greater than 240 ̋ C in extrusion or injection molding operations [30] Apart from their thermal stability and migration issues, key factors such as compatibility, effect on mechanical and electrical performance, toxicity, cost-effectiveness, ability to cause corrosion, color stability, recyclability, as well as sustainability in general, need to be kept in mind while developing new non-halogenated FR for polyamide 6. The main aim of this work has been to develop a new phosphorus-nitrogen-containing halogen-free flame-retardant for PA6 which allows maintaining the excellent mechanical properties, high thermal stability, and good processability of the polymer while improving, at the same time, its flame resistance to a V0 rating in the UL 94 test. To evaluate the influence of their incorporation in a PA6 matrix, two formulations containing 17 wt % additives each have been obtained using compounding by melt extrusion, and their mechanical, thermal, rheological, and flammability properties have been evaluated and compared with neat PA6
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