Cone calorimeter structure

The effects of metal-containing POSS on the combustion behavior of polypropylene have been investigated.46 Metal-POSS was prepared from incompletely condensed structures by reaction with organometallic compounds. The dimeric and oligomeric of Al and Zn-isobutyl silsesquiox-ane (POSS) have been evaluated as potential flame retardants for polypropylene, and the results were compared with PP/octaisobutyl POSS. The cone calorimeter data (Table 8.2) revealed that... 

The nature of the organomodifier plays a role in the existence of true nanocomposite structures (intercalated for 15A and 30B, exfoliated for 25A, microcomposite for 10A), cone calorimeter results associated with x-ray diffraction (XRD) suggest that increased flame retardancy are more dependent on physical and thermal cross-linking of clay particles and polymer chains than on formation of nanocomposite structure. However, it can be concluded that the role of clay is crucial since PHRR values are reduced up to 70% in the presence of clays. 

In the work of Wilkie et al.,55,56 oligomers of styrene, vinylbenzyl chloride, and diphenyl vinyl-benzylphosphate and diphenyl vinylphenylphosphate (DPVPP) have been prepared and reacted with an amine and then ion-exchanged onto clay. The resulting modified DPVPP clays have been melted blended with polystyrene and the flammability was evaluated. XRD and TEM observations proved the existence of intercalated nanocomposite structures. Cone calorimeter tests have shown a substantial reduction in the PHRR of about 70% in comparison with pure PS. According to the authors, this reduction was higher than the maximum reduction usually obtained with PS nanocomposites. Other vinylphosphate modified clay nanocomposites were also elaborated. The reduction in PHRR was greater with higher phosphorus content than for DPVPP. Consequently, the reduction in PHRR seemed attributed to both the presence of the clay and to the presence of phosphorus. 

The quality of char formed for metal hydroxide/MMT combinations seems of prime importance to maximize the barrier effect. Incorporation of silica in combination with MH and MMT by partial substitution of MMT has been investigated by Ferry et al.,64 Laoutid et al.70 to improve the cohesion of charred and expanded structure. Even though silica generated cracks in the char and reduces its resistance, as measured by indentation, tire behavior, as studied by cone calorimeter was improved. 

Van Hees P, Axelsson J. Modelling of euroclass test results by means of the cone calorimeter. In Multifunctional Barriers for Flexible Structure Textile, Leather, and Paper. Duquesne S, Magniez C, Camino G, Eds. Springer Berlin, 2007. 

For tests other than E-84, there have been some studies on the effects of fiber loading and fiber layup on composite flammability. This has primarily been work done by the U.S. Navy on the flammability of composites used in naval vessel flammability,19-20 or work by Kandola et al.10-21-22 on the effect of fiber type and content on polymer composites studied by cone calorimeter. More work is being conducted in studying the effects of fiber orientation and lay-up not on overall flammability performance, but flammability performance under structural load. This is the most important for aircraft, vehicles, and buildings where the composites are structural members. The concern here is... 

The principal effects observed in cone calorimeter tests are a marked reduction in peak and average rate of mass loss and in heat release. There appears to be little reduction in total heat of combustion or in smoke levels. The workers at NIST report that there seems to be little difference between intercalated and delaminated forms of nano-clay, despite evidence that polymer thermal stability can be more improved by the intercalated structure. 

Cone Calorimeter data of a nylon-6,6 composition with PVA oxidized by KMn04 (Mn - chelate complexes) show improvement of peak rate of heat release from 476.7 kW/m (composition of nylon-6,6 with PVA) to 399.5 kW/m (composition of nylon-6,6 with PVA, oxidized by KMn04) [212]. On the other hand, the exothermal process of smoldering for the composition of nylon-6,6 with PVA, oxidized by KMn04 has been noted [213]. This reaction is evidently provided by chelated Mn-structures which increase the total heat release of nylon-6,6 with PVA, oxidized by KMn04 in comparison with nylon-6,6 with PVA. 

This process creates a polymer-layered silicate nanocomposite with the either a delaminated hybrid structure or an intercalated one. The intercalated structure, which forms when the mass fraction of clay is greater than 20%, is characterized by a well ordered multilayer with spacing between the silicate layers of only a few nanometers. The delaminated hybrid structure, which forms when the mass fraction of clay is less than 20%, contains the silicate layers individually dispersed in the polymer matrix. The thermal, mechanical and FR properties of nylon-6 clay nanocomposite with only 5% of clay fraction show excellent improvements over nylon 6. In the paper by Gilman it was pointed out that cone calorimeter data show the reduction of RHR (max.) by 63% in a nylon,6/clay nanocomposite containing a clay mass fraction of only 5% [233]. This nanocomposite has the same heat of combustion as the pure nylon-6. 

The data for nanocomposites polymer/organoclay on the basis of polyamide-6 (PA-6), polyamide-12 (PA-12), polystyrene (PS) and polypropylene (PP), which are listed in table 11.1, were used for the relationships structure-flame-resistance characteristics. The maximum rate of heat release measured with the use of a cone calorimeter according to the standards ASTM 1354-92 and ISO/DIS 13927 [2], the values of which are also listed in Table 11.1, was used as flame-resistance characteristic of the indicated nanomaterials. 

A Japanese patent issued to Sekisui Chemical Co. Ltd." describes cone calorimeter data for polyethylene (PE)-derived nanocomposites in which organically modified layered silicates (OMTs) were combined with a variety of conventional flame retardant additives. The ammonium salt-modified silicate (SBAN-400) was incorporated into the PE compositions at 10 phr (Table 8.10). The PHRR results for the PE nanocomposite materials are 50% lower than the PHRRs for pure PE and PE with 10 phr pristine clay (MMT). These results suggest that without suitable organic treatment of the clay, the addition of MMT has little effect on flame retardant properties. Due to the favorable interactions arising from the organic surface treatment of the clay, the OMT forms a nano-dispersed structure in the PE matrix, while the PE-pristine MMT material is an immiscible or conventional composite. At 10-phr loading levels, where the OMT reduces the PHRR substantially for PE nanocomposite, DB-AO has little effect and APP alone has only a weak effect on PHRR of PE, respectively. Addition of either 15 phr of DB-AO or 15 phr of APP to pure PE decreases the PHRR values by only 10 to 20% from that of pure PE. However, addition of 5 phr of APP to a PE-SBAN N-400 nanocomposite with 10 phr of SB AN N-400 causes a 63% reduction in the PHRR. The addition of 5 phr of phenylphosphate and 10 phr of SB AN N-400 also reduces the PHRR by 60% (Table 8.10). 

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