Abstract
A novel intumescent flame retardant (IFR) agent designated as Dohor-6000A has been used to prepare halogen-free flame retardant polypropylene (PP) fibers via melting spinning. Before being blended with PP resin, a surface modification of Dohor-6000A was carried out to improve its compatibility with the PP matrix. The rheological behavior of flame retardant Dohor-6000A/PP resin, the structure, morphology, mechanical properties, flammability of the Dohor-6000A/PP fibers were studied in detail, as well as the action mode of flame retardant. X-ray diffraction (XRD) showed that the addition of Dohor-6000A did not damage the crystal as well as the orientation structure of PP matrix, which was helpful to the maintenance of mechanical properties. The presence of the IFR significantly improved the flame retardant performance and thermal stability of PP fibers. When the content of Dohor-6000A reached 25%, the fibers displayed a limiting oxygen index (LOI) value of 29.1% and good melt-drop resistance. Moreover, the peak heat release rate (PHRR) and total heat release (THR) from microscale combustion colorimetry (MCC) tests were decreased by 26.0% and 16.0% in comparison with the same conditions for pure PP fibers. In the condensed phase, the IFR promoted a carbonization process and promoted the formation of a glassy or stable foam protective layer on the surface of the polymer matrix. In addition, the IFR decomposed endothermically to release of non-combustible gases such as NH3 and CO2 which dilutes the combustible gases in the combustion zone.
Highlights
Introduction published maps and institutional affilPolypropylene (PP) fibers are produced from the melt spinning of isotactic PP [1].As one of the main fiber varieties, due to their low density, low moisture absorption rate, high toughness, good thermal insulation, antibacterial, chemical stability, and good antifouling, PP fibers are widely used in interior decorations and industrial fields [2,3,4,5,6]. PP fiber has many excellent properties, high flammability still limits its further applications and development [7,8]
It is ascribed that the flame retardant is well dispersed in the polypropylene matrix, which hinders the entanglement of matrix
From the fiber cross section, it can be seen that the intumescent flame retardant (IFR) is evenly dispersed in polypropylene and there are no clear boundaries between the flame retardant particles and the matrix
Summary
Polypropylene resin (T30S, MFI = 2.6 g/10 min) was sourced from Lanzhou Petrochemical Co., Ltd., Lanzhoou, China. Maleic anhydride grafted polypropylene (E43) was purchased from Westlake Chemical Co., Ltd., Houston, TX, USA as the compatibilizer. Υ-Aminopropyltriethoxysilane (KH-550), glacial acetic acid and absolute ethanol were obtained from Chengdu Kelong Chemical Reagent Factory, Chengdu, China. Dohor-6000A (powder, average size < 7 μm) was obtained from Dohor New Material Technology Co., Ltd., Dongguan, China. Dohor-6000A is a blended nitrogen-phosphorus IFR and the mass contents of the phosphorus, nitrogen and carbon are 19.78%, 21.31% and 17.45%, respectively.
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