Intumescent systems zeolites

An extensive study was conducted on the effect of chemical and structural aspects of zeolites on the fire performance of the intumescent system, ammonium polyphosphate-pentaerythritol (APP-PER), where a marked improvement of the fire-retardant properties within different polymeric matrices has been observed.56 58 The synergistic mechanism of zeolite 4A with the intumescent materials was investigated using solid-state NMR. Chemical analysis combined with cross-polarization dipolar-decoupled magic-angle spinning NMR revealed that the materials resulting from the thermal treatment of the APP-PER and APP-PER/4A systems were formed by carbonaceous and phosphocarbonaceous species, and that the zeolite enhances the stability of the phosphocarbonaceous species. 

In an attempt to provide compatibility between the FR and polymer matrix, Wang et al. reported recently on a novel microencapsulated intumescent system containing 4A zeolite as a potential flame retardant for natural rubber (NR).61 The flame-retardant properties of NR composites loaded with different amounts of intumescent flame retardant (IFR), IFR-4A zeolite, and microencapsulated intumescent flame retardant (MIFR)-4A zeolite agents were studied and compared. The LOI data demonstrate that the NR composite filled with 50phr of MIFR-4A zeolite agent and 50phr of IFR-4A zeolite shows better FR properties as compared to NR and 50phr of IFR-filled systems. 

This approach has been followed in the case of APP/PER (Pentaerythritol) systems, with or without zeolite (such as 4A zeolite for example), in order to better understand the synergistic effect of these aluminosilicate fillers in polyolefin-based intumescent systems.15... 

The comparison between the 7, values of the two systems (Figure 10.5) shows that their behavior compared to HTT is different. At 280°C, the 7 , value of the system with the zeolite is twice as large as that for the APP/PER system. It was concluded that the materials formed at this temperature are structurally different. Indeed a slower 7) means that the molecular motions may be hindered and therefore that the structure may be more rigid. Between 280°C and 350°C, the Tx values decrease and become identical. At 350°C, both systems are organized in stacks of polyaromatic species and it may be proposed that the two materials are structurally, in the NMR sense, similar. At higher temperatures, the 7 , values of the systems with zeolite are always larger. The carbonization process of the two intumescent materials develops in different ways. The zeolite allows molecular motion and the carbonaceous shields keep mobile structures. 

W. Yuan, H. Chen, R. Chang, L. Li, Synthesis and characterization of NaA zeolite particle as intumescent flame retardant in chloroprene rubber system, Particuology, ISSN 1674-2001 9 (3) (June 2011) 248-252. http //dx.doi.oig/10.1016/j.partic.2010.05.016. 

In previous work we have combined the intumescent APP-PER system with zeolites in an ethylene-butyl acrylate-maleic anhydride terpolymer (hereafter called LRAM3.5) and we have observed (in particular with 4A zeolite) a high degree of improvement in fire-proofing properties (Figure 6.4). 

Instead, these type of flame retardants exhibit some drawbacks compared with bromine-containing flame retardants, such as low flame retardant efficiency and low thermal stability. Improved intumescent flame retardant systems have been found by formulating with zeolites and organoboron siloxanes (9). 

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