Using PA6 as a charring agent in intumescent polypropylene formulations based on carboxylated polypropylene compatibilizer and nano‐montmorillonite synergistic agent

Abstract

ABSTRACT:The intumescent fire retardant polypropylene (IFP/PP) filled with ammonium polyphosphate (APP), melamine (M), and PA6 (charring agent) is discussed. Intumescing degree (ID) and the char yield were determined. Only when the three main components of IFR coexist at appropriate proportions, it has optimal ID and higher char yield. The appropriate proportion is PA6 : APP : M ϭ 10 : 10 : 5. A new compatibilizer, carboxylated polypropylene (EPP), was added to PP/PA-6 blend. Flow tests indicated that the apparent viscosity increased with the addition of EPP, thermal characterization suggested that EPP has reacted with PA6, PA6-g-EPP cocrystallized with PA6, and EPP-g-PA6 cocrystallized with PP; SEM micrographs illustrated that the presence of EPP improved the compatibility of PP and PA6. All the investigations showed that EPP was an excellent compatibilizer, and it was a true coupling agent for PP/PA6 blends. Using PA6 as a charring agent resulted in the IFR/PP dripping, which deteriorated the flammability properties. The addition of nano-montmorillonite (nano-MMT) as a synergistic agent of IFR enabled to overcome the shortcoming. The tensile test testified that the addition of nano-MMT enhanced the mechanical strength by 44.3%. SEM showed that nano-MMT improved the compatibility of the composites. It was concluded that the intumescent system with nano-MMT was an effective flame retardant in improving combustion properties of polypropylene.

Intumescence: Tradition versus novelty. A comprehensive review

“…They prepared thermoplastic poly(urethane) (TPU)/APP intumescent blends, using different contents of TPU, to enhance the flame retardancy properties of PP. PA6-EVA alloy (unloaded or loaded with 5wt.-% of an organophilic montmorillonite) turned out to be more efficient char forming polymers for PP with respect to TPU, as documented by Tang et al [100] and Ma and coworkers [101]. In the first study, the classical intumescent formulation consisting of APP, PER and MP (melamine phosphate) was mixed with different PA6-EVA alloys (having molar ratios from 1:1 to 1:6) in the presence of maleic anhydride-gpolypropylene (MAPP) [100].…”

“…Table 9 PA6 as a carbonization agent in IFR formulation has been successful used in PP [173]. However, using PA6 resulted in dripping, while nano-MMT as a synergistic agent was able to overcome PP dripping, by accelerating char yield and enhancing its density [101]. Analogously, Tang et al…”

“…Ma and co-workers [101] found that a formulation consisting of PA6: Alternative to PA6, Yang et al [104] proposed two novel copolyamides as charring agents on flame retardancy for PP. The results showed that these copolyamides have better dispersion and compatibility in PP matrix than PA6 and significantly increased the mechanical properties as well as the fire performances in terms of LOI and char yield achieved.…”

“…Thermoplastic poly(urethane) + APP PP [99] PA6-EVA alloy + APP + pentaerythritol + melamine phosphate PP [100] PA6 or PA6-montmorillonite nancomposites + APP + melamine PP [101] EVA + ethylene-butylacrylate-maleic anhydride APP PP/PA6 blends [102,103] Copolyamides PP [104] Hyperbranched poly(amine) + APP PA6 [105] Hyperbranched poly(amine) + APP PLA [106] Triazine-based polymer + APP PE [107] Triazine-based polymer + APP PP [108] Triazine-based polymer + CD with silicon oligomers PP [109] M a n u s c r i p t A c c e p t e d M a n u s c r i p t A c c e p t e d M a n u s c r i p t M a n u s c r i p t Table 9 PHRR values of IFR-MMT-PP nanocomposites from ref. [172] Sample A c c e p t e d M a n u s c r i p t Table 11 Nanoparticles functionalized with intumescent components Nanoparticle Functionalized structure with IFR Reference CNT [196] ZrP [187] LDH [186] MMT [212] M a n u s c r i p t LOI=30.5%, PHRR * reduction = -75% [224] A novel organophosphorus (24wt.-%) + melamine (6wt.-%) V0 UL94 classification, LOI=31.6%, PHRR * reduction = -85% [225] APP + PPM Triazine HF (total loading of 20wt.-%) V0 UL94 classification, LOI=31%, PHRR * reduction = -91% [226] Poly(p-ethylene terephthalamide) (7.5wt.-%) + APP (22.5wt.-%) V0 UL94 classification, LOI=35% [227] Ionic liquid containing phosphorus (5wt.-%) + APP (25wt.-%) V0 UL94 classification, LOI=31.8%, PHRR * reduction = -72% [228] M a n u s c r i p t V0 UL94 classification, PHRR * reduction = -84.0% [229] M a n u s c r i p t Table 13 Novel components in PP/IFR formulation.…”

Flame Retardance and Thermal Degradation of Intumescent Flame Retardant Polypropylene with Microencapsulated TPMP

“…Consequently, present research is mainly focused on looking for halogen-free additives in the form of intumescent flame retardant (IFR), which are being thought as the alternatives of the halogen containing flame retardants (Gao et al, 2006;Ma et al, 2006). Generally, IFR contains three main ingredients: acid source, carbon source, and gas source.…”