Flame-Retardant Mechanism and Mechanical Properties of Wet-Spun Poly(acrylonitrile-co-vinylidene chloride) Fibers with Antimony Trioxide and Zinc Hydroxystannate

Abstract

To produce flame retardant poly(acrylonitrile-co-vinylidene chloride) (PANVDC) fibers with limiting oxygen index (LOI) values above 28%, flame retardants are added to fibers. Because antimony trioxide (ATO) used widely for PANVDC is suspected as a carcinogen, non-toxic zinc hydroxystannate (ZHS) could be the alternative for reduction of ATO usage. Moreover, a flame retardant efficiency of the combination of ATO with ZHS could be expected because it was reported that ATO resists flame in the gas phase, whereas ZHS reacts in the condensed phase. Therefore, this study discussed the flame retardant mechanisms of ATO and ZHS in PANVDC, and evaluated the efficiency of the combination. PANVDC fibers with ATO and ZHS in 15 phr were produced by wet spinning. When ZHS was added, a more cyclized structure was detected (e.g., 1-methylnaphthalene) through pyrolysis−gas chromatography-mass spectrometry (Py-GC/MS). As a result of SEM-EDX analysis, Sb and Cl hardly remained in char layers of PANVDC-ATO; meanwhile, Zn, Sn, and Cl remained in that of PANVDC-ZHS. This implied that SbCl3 from reaction of ATO and HCl reacts in the gas phase, whereas ZnCl2 and SnCl2 from ZHS and HCl promotes the cyclization reaction of PANVDC in the condensed phase. The LOI values of PANVDC, PANVDC-ATO, and PANVDC-ZHS were 26.4%, 29.0%, and 33.5%, respectively. This suggests that ZHS is a highly effective for PANVDC. Meanwhile, the LOI of PANVDC containing ATO-ZHS mixture is 31.0%. The combination of ATO and ZHS exhibited no efficiency. The addition of ATO and ZHS slightly reduced the tenacities of the fibers, respectively, 3.11 and 3.75 from 4.42 g/den.

Study on the Flame Retardancy and Hazard Evaluation of Poly(acrylonitrile-co-vinylidene chloride) Fibers by the Addition of Antimony-Based Flame Retardants

“…The second-stage weight loss appeared to be caused by the decomposition of the char layer produced by the subsequent reaction after dehydrochlorination [ 16 ]. The TMR2 values of PANVDC, PANVDC-ATO(3), and PANVDC-ATO(4) were 612 °C, 576 °C, and 569 °C, respectively.…”

“…Figure 2 represents the scheme of wet-spinning system. The PANVDC fibers, along with the types of flame retardants, were prepared using a laboratory-scale wet-spinning system [ 16 ]. DMSO was used as the solvent because it is relatively less toxic than other solvents.…”

“…Therefore, various studies were conducted to reduce the antimony oxide used for halogen compounds and use a human-friendly flame retardant additive that could replace it [ 9 , 14 ]. In a previous study, a flame retardancy was confirmed by adding a different type of flame retardant to replace antimony trioxide, and, as a result, it was reported that flame retardancy was indicated even when a small amount of antimony trioxide was mixed or entirely replaced [ 15 , 16 , 17 , 18 ]. On the other hand, research on new flame-retardant additives is needed because it is difficult to sufficiently reduce the use of antimony trioxide.…”

“…Flame-Retardant Mechanisms Pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) was investigated using the sampling procedure reported elsewhere [16]. Py-GC/MS was conducted on a pyroprobe (PY-2020iD, Frontier, Fukushima, Japan) combined with a gas chromatograph (7890, Agilent, Santa Clara, CA, USA) and mass spectrometer (5975, Agilent, Santa, Clara, CA, USA).…”

“…Flame Retardancy of PANVDC Film Flame retardancy was investigated by performing two tests reported elsewhere [16,17]. All samples were prepared in the form of a film.…”