Cone calorimetry

Applications. A cone calorimeter, named after a truncated cone shape of the furnace, is a heat release rate calorimeter which permits the determination of heat release under controlled conditions. It determines the critical fire parameters required for a range of natural and synthetic materials using small samples (100 mnL), and simple materials, and is used for composites and combinations of different materials. This apparatus allows simultaneous and continuous determinations of heat release rate, smoke production rate, mass loss rate, concentration of the various combustion gases formed, ignitability, heat of combustion and soot production data for the materials tested. 

Testing procedure. The equipment was developed by NIST and is produced by PL Thermal Sciences, 300 Washington Blvd., Mundelein, IL 60060, USA. Testing according to ISO 5660 requires a heat flux of 25 kW/nr and an air flow 24 1/s. The 

Major results. Due to the computerized determination of many parameters of material combustion and the well controlled process of combustion, this instrument is fi equently used in studies of materials containing fillers. 

Flammability tests include (a) UL94, (b) limiting oxygen index (LOI), and (c) cone calorimeter tests. LOI is used to obtain the limit of oxygen concentration that sustains combustion, whereas UL94 studies the ignition from a small flame and subsequently the 

Flame retardant nanocomposites with polymer blends 

Study by Chuang et al. [15] also revealed that there is no difference in the TTI for an EVA/linear LDPE blend when OMMT is added. 

Note The values shown here were calculated as averages of the tests at all the heat fluxes. 

TABLE 8.6 Peak Heat Release Rate and Peak Mass Loss Rate of PA6 Materials  

Cone calorimetric data for PU and corresponding flame retardant nanocomposites are listed in Table 8.7. The data include the peak heat release rate (PHRR), mass loss rate (MLR), specific extinction area (SEA), amount of CO released. 

TABLE 8.9 Cone Calorimetric Data for PS Nanocomposites Prepared Using 55% DPVPP-Modifled Clay and 75% DPVPP-Modifled Clay, Respectively, via Melt Blending  

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). 

An important parameter which proves the effectiveness of flame retardancy of samples is the heat release rate, which is variable in time and reaches its maximum PHRR. The shape of the curve of the heat release rate for the high-density polyethylene is significantly different from the shape of the rest of the composition containing the MDH. In the case of high-density polyethylene (sample no. 0), the maximum rate of heat release (PHRR) occms just before flame out (tp g = 468 s). For the rest of the 

Symbol of composite T (s) PHRR (kW/m ) PHRR (s) PHRR reduction (%) AHRR (kW/m ) 

With the increase of MDH in PE-HD the maximum rate of heat release (PHRR) decreases, which for all composites containing 60% MDH weight particle was reduced approximately 90% in comparison to the output of polyethylene. 

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Price, D., Bullett, K. J., Cunliffe, L. K., Hull, T. R., Milnes, G. J., Ebdon, J. R., Hunt, B. J., and Joseph, P., Cone calorimetry studies of polymer systems flame retarded by chemically bonded phosphorus, Polym. Degrad. Stab., 2005, 88, 74—79. 

Tang et al.84,85 also examined the incorporation of MMT in intumescent PP with a compatibilizer (hexadecyltrimethylammonium bromide) which is usually used as surfactant for making OMMT. Evidence of making a nanocomposite is shown with and without the intumescent system. Cone calorimetry shows a large improvement in the flammability properties when using OMMT. The results are similar to what we showed above. They postulated a mechanism of action suggesting the formation of an aluminophosphate structure but no evidence was given. 

Using this concept, it has been shown by cone calorimetry that over a 3 min combustion period, 3 and 6 mm thick laminated structures, made with different fire-retardant skin and unfilled core combinations can give similar resistance to ignition and comparable HRR and smoke extinction area (SEA) results to fully fire-retardant compositions (Table 7.4). Mechanical properties, in particular impact strength, were also found to be greatly enhanced by this approach, since less fire-retardant filler is present in the material. Whereas this approach has been demonstrated to be effective with hydrated fillers, it is applicable to all fire-retardant types. 

Cone Calorimetry Results for Multicomponent Structures (Magnesium Hydroxide in Polypropylene)... 

Scudamore MJ, Briggs PJ, Prager FH. Cone calorimetry—a review of tests carried out on plastics for the Association of Plastic Manufacturers in Europe. Fire Mater. 1991 15 65-84. 

Gradient Heat Flux Environments and Rapid Cone Calorimetry.434... 

CASE STUDY 2. HIGH THROUGHPUT POLYMER FLAMMABILITY CHARACTERIZATION USING GRADIENT HEAT FLUX ENVIRONMENTS AND RAPID CONE CALORIMETRY ... 

Morgan, AB, Bundy, M, and Ohlemiller, T. 2007. Cone calorimetry analysis of UL-94 V-Rated plastics, Fire Mater., 31, 257-283. 

In our earlier study, we studied the flammability of these knitted fabrics by cone calorimetry,83 but could not get reproducible results. This was due to samples being very thin and there was considerable bubbling and flowing of the polymer during burning which caused anomalies in the balance... 

Bourbigot et al.85 at Lille have used poly(vinylsilsesquioxane) (POSS) in PP (110 wt%) to melt spin filaments, which were then knitted into fabrics. POSS was thermally stable and no degradation was detected in the processing conditions. They have tested the flammability of the fabrics using cone calorimetry. POSS presence had minimal effect on peak heat and total heat release values of PP fabric, but delayed the TTI. This behavior of POSS is opposite to that of layered silicates, which have minimal effect on TTI, but reduce PHRR. Authors claim that POSS does not act as a FR but only as a heat stabilizer via a decrease of the ignitability. 

Researchers in the Lille group have also been successful in preparing yarns from polypropyl-ene/multiwalled carbon nanotubes (MWNT) (1% and 2% by mass) nanocomposites.6-86 Fabrics knitted from these yarns were tested by cone calorimetry. PHRR reduced by 50% for a fraction of nanotubes of only 1 wt % but the TTI of the nanocomposite was shorter. This is shown in Figure 24.9. 

Nazare S., Kandola, B.K., and Horrocks, A.R. 2002. Use of cone calorimetry to quantify the burning hazard of apparel fabrics, Fire Mater., 26 191-199. 

Cone calorimetry according to the ASTM E1354138 or ISO 5660139 standards are commonly used in the laboratory to screen flammability of materials by measuring heat release characteristics of the compound.116140 This device is similar to FPA but does not have the versatility of FPA. The cone calorimeter can determine the ignitability, heat release rates, effective heat of combustion, visible smoke, and C02 and CO development of cable materials. This test has been used extensively for wire and cable material evaluation. The microscale combustion calorimeter (MCC), also known as pyrolysis combustion flow calorimeter (PCFC), was recently introduced to the industry for screening heat release characteristics of FR materials.141142 This device only requires milligram quantities of test specimen to measure the heat release capacity (maximum heat release potential). Cone calorimetry and MCC have been used in product development for flammability screening of wire and cable compounds.118... 

Correlations were also established between UL 94, LOI, MCC, and cone calorimetry for both halogenated and nonhalogenated FR wire and cable compounds.149 The study (Figure 26.5) indicated that LOI has poor correlation with MCC parameters due to different flame combustion mechanisms in the LOI (incomplete combustion) and the MCC (forced complete combustion) tests. This correlation was improved by taking into account the burning efficiencies (i.e., combustion and heat transfer efficiencies) of the polymer compounds.150... 

The UL 94, LOI, and cone calorimetry were also conducted on the jacketing materials (see Table 26.2). The results show that EVA-MH-NanoM sample had the lowest PHRR, longest TTPHRR,... 

Genovese, A. and Shanks, R.A., Fire performance of poly(dimethyl siloxane) composites evaluated by cone calorimetry, Composites Part A, 2008, 39, 398-405. 

The results are reported of an in depth study of the structure, thermal properties, dynamic mechanical properties, flammability and smoke properties of melt blended PVC-sodium montmorillonite nanocomposites. Investigative properties employed included X-ray diffraction, TEM, TGA, DMA and cone calorimetry. The effects of clay loading, DOP concentration, annealing, blending time and molec.wt. on the formation of the composites are discussed and fire properties of PVC-organically modified clay and PVC-sodium clay nanocomposites are presented and discussed. 15 refs. USA... 

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