Thermal stability and combustion behavior of flame-retardant polypropylene with thermoplastic polyurethane-microencapsulated ammonium polyphosphate

Abstract

In this article, thermoplastic polyurethane-microencapsulated ammonium polyphosphate (MTAPP) is prepared and well characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis (TGA). MTAPP and APP are added onto polypropylene (PP) as a novel intumescent flame-retardant system to improve the flame retardancy of PP. The flammability, thermal stability, and mechanical properties of the flame-retardant PP composites are investigated by limiting oxygen index (LOI), UL-94 vertical burning test, cone calorimeter test (CCT), TGA, and mechanical properties tests. The results show that MTAPP exhibits better flame retardancy and thermal stability than that of the APP in the flame-retardant PP composites. The LOI value of the PP/MTAPP composite at the same loading level is higher than that of PP/APP composite. The dripping of MTAPP system disappears compared with APP system from UL-94 test. The results of the CCT also indicate that MTAPP is an effective flame retardant in PP. The improvement may be attributed to the better charring capacity of MTAPP from TGA. Additionally, the mechanical properties of MTAPP are better than those of APP in PP.

Effects of wool fibres, ammonium polyphosphate and polymer viscosity on the flammability and mechanical performance of PP/wool composites

“…It is believed that phosphoric acids released from APP during thermal decomposition catalysed the dehydration and cross-linking of polymer end chains and reactive groups, initiating char formation [37]. In addition, ammonia of APP acted as blowing agents to swell and produce the insulating multicellular protective char layer [38]. However, shrinkage or damage of the intumescent occurred during the test, Fig.…”

Influence of polyamide 6 as a charring agent on the flame retardancy, thermal, and mechanical properties of polypropylene composites

“…The small migration percentage for PP/MTAPP composites is attributed to the isolation effect of the encapsulated shell effectively protecting the APP powders from being attacked by water. Moreover, the formation of hydrogen bonds between the APP powders and TPU molecular chains improve the compatibility, which decreases the migration of the MTAPP . However, it is well known that PA6 has a high solubility in water due to the strong polar group in the side chain.…”

“…Ammonium polyphosphate (the degree of polymerization, n > 1000) (APP, Z201) was offered by Shifang Taifeng New Flame Retardant, China. (TPU)‐microencapsulated APP (MTAPP) was prepared according to the method . All materials were dried at 80°C for 12 h before use.…”

“…In most cases, ammonium polyphosphate (APP) is chosen as acid source and blowing agent in IFRs. Our previous work showed that the addition of elastomer‐microencapsulated APP (MTAPP) in the flame‐retarded PP composites obtained better mechanical properties and flame retardancy compared with PP/APP composites. However, it is very difficult to reach the flame retardant rating in UL‐94 test for the flame‐retardant composites filled with MTAPP alone due to the scarcity of charring agents.…”

Synergistic flame‐retarded effect between carbon nanotubes and ammonium polyphosphate in Nylon6 and Nylon6/polystyrene blends

“…Intumescent flame retardant (IFR) has attracted considerable attention from those interested in the development of flame retardation in polymers not only because they are more environmentally friendly than halogen‐containing flame retardants but also as they have high flame‐retardant efficiency. On heating, IFR additives form a foamed cellular charred layer on the surface of the product, which decelerates heat and mass transfer between the gaseous and condensed phases . A typical intumescent formulation consists of three ingredients: an acid source (ammonium phosphates [APP] or polyphosphates), a carbonizing compound (pentaerythritol, arabitol, sorbitol, inositol, saccharides, polysaccharides, etc), and a blowing agent (melamine and isocyanurate) .…”