Synthesis and Application of a Novel Polyamide Charring Agent for Halogen-Free Flame Retardant Polypropylene

Abstract

A novel charring agent, poly(p-ethylene terephthalamide) (PETA), for halogen-free flame retardant polypropylene was synthesized by using p-phthaloyl chloride (TPC) and ethylenediamine through solution polycondensation at low temperature, and the effects of PETA on flame retardance of polypropylene (PP)/IFR systems were studied. The experimental results showed that PETA could considerably enhance the fire retardant performance as proved by evidence of the increase of limiting oxygen index (LOI) values, the results of UL-94 tests, and cone calorimeter tests (CCT). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) demonstrated that an appropriate amount of PETA could react with PP/IFR system to form cross-link network; a more compact char layer could be formed which was responsible for the improved thermal and flame retardant properties of PP/IFR systems. However, the superfluous amount of PETA would play the negative role.

Effect of Particle Size of Additives on the Flammability and Mechanical Properties of Intumescent Flame Retarded Polypropylene Compounds

“…In each experiment 2 × 9 g APP was milled by keeping the ball to powder weight ratio at 20 and by setting the milling machine to maximum power. The effect of milling time and ball diameters (5,8, and 11 mm) on the morphology of APP particles was comprehensively studied. Accordingly, a milling time of 72 min and the use of 5 and 11 mm balls in a weight ratio of 2 to 1 were selected to produce APP of reduced particle size in larger amounts.…”

“…The fire retardant mechanism of IFRs involves the formation of an expanded charred foam layer on the polymer surface, which acts as a heat insulator, limiting the heat transfer from the heat source to the polymer and the mass transfer from the polymer [5][6][7]. In general, the intumescent formulations are composed of three main ingredients: acid source, char forming agent, and blowing agent [8]. A typical example in the case of polypropylene (PP) is the ammonium polyphosphate (APP)/pentaerythritol (PER) system [9].…”

Synergistic fire retardancy of melamine resin modified with pentaerythritol and ammonium polyphosphate in PP

“…Tris(2-hydroxyethyl) isocyanurate (THEIC), pentaerythritol (PER), and other low molecular hydroxyl compounds were used as charring agents in early stage, however, they have some drawbacks, such as poor thermal stability, very high-water solubility, easy migration and precipitation from the matrix, and poor fire retardancy of IFR compounded with them. [3][4][5] To address the above issues, lots of charring agents such as polyamide, [6][7][8][9][10][11] phenolic resin, [12][13][14] thermoplastic polyurethane (TPU), [15][16][17] tris(2-hydroxyethyl) isocyanurate derivatives (THEIC), [18][19][20] macromolecular triazine charring agents, [21][22][23][24][25][26][27][28][29][30] and the derivatives of PER [31][32][33][34][35][36][37][38] have been developed. Phenolic resin is weak in charring and is mainly used for polyamide 12,13 and polycarbonate.…”

“…14 In the early days, polyamide-6 was mainly used as a charring agent, 6 but its charring capability was poor. Some new polyamide charring agents [7][8][9][10][11] developed in recent years have better charring capability than polyamide-6, but their synthesis process is more complicated. The charring effect of TPU is also poor, but it can be used in combination with PER.…”

“…To address the above issues, lots of charring agents such as polyamide, 6–11 phenolic resin, 12–14 thermoplastic polyurethane (TPU), 15–17 tris(2‐hydroxyethyl) isocyanurate derivatives (THEIC), 18–20 macromolecular triazine charring agents, 21–30 and the derivatives of PER 31–38 have been developed. Phenolic resin is weak in charring and is mainly used for polyamide 12,13 and polycarbonate 14 .…”