Polypropylene heat release rate

Fig. 12.8 The heat release rate for the burning of several polyolefins in cone calorimeter PMP poly (4-methyl 1-pentene), PP polypropylene, PE polyethylene), the cone radiancy 35 kW m ...

Figure 11.1. Chemical heat release rate for a 100-mm diameter and 25-mm thick horizontal slab of polypropylene exposed to 50 kW/m of external heat flux in normal air, under well-ventilated condition, in the ASTM E2058 Apparatus [31]. Airflow rate 2.9 X 10 m /s. Data up to about 900 s are for the combustion with very small bubbles formed at the surface of the solid slab of PP. Beyond about 1150 s, the data are for the combustion with deep liquid pool over the solid slab of PP. Data were measured in our laboratory.

FIGURE 33.2. A plot of heat release rate (HRR) for pure polypropylene compared with a 4% loaded polypropylene/ clay nanocomposite. 

The critical values of the mass pyrolysis rate, heat release rates, and water application rates for flame extinction for polymers, are listed in Table 53.14. For the polymers listed in the table, the critical values of the heat release rates do not depend on the generic namres of the polymers. The average critical values of the chemical, convective, and radiative heat release rates are 100 + 7, 53+9, and 47 +10 kW/m, respectively. The critical water application rate required for flame extinction is polyoxymethylene, polymethylmethacrylate and polyethylene with 25% chlorine (2.1-2.5g/m -s)[Pg.913]

When used in a flexible PU foam, smoke and toxic fume emissions are greatly educed compared with untreated foam or ones with halogenated FRs present. When utilised in a polypropylene composition, the heat release rate is much lower lhan for a halogen- or a phosphate-based FR, with a much-reduced peak. 

Lately Qin at al. reported data on polypropylene/montmorillonite (PP/MMT) microcomposites thermal degradation and flammability [11]. They mentioned that PP microcomposites exhibit higher thermal stability and considerably reduced peak heat release rate due to physico-chemical adsorption of the volatile degradation products on the silicates... 

In the present study the combustibility of polypropylene nanocomposite was evaluated by a cone calorimeter. The tests were performed at an incident heat flux of 35 kW/m using the cone heater [21]. Peak heat release rate (RHR), mass loss rate (MLR), specific extinction area (SEA) data, earbon monoxide and heat of eombustion data measured at 35 kW/m2, are presented in Figs. 11 and 12. 

Figure 6.7 A comparison of the effect of two similar magnesium hydroxide fillers on the heat release rate from polypropylene using cone calorimetry.

Figure 14.34 Heat release rate and total heat release for maleic anhydride bonded polypropylene with various concentrations of exfoliated montmorillonite added.

The effect of the additives on the oxygen index of PMMA, PS and nylon-6, 6 has also been measured. [227). The results are shown in Table 5.5. The trend in oxygen index response for PMMA and PS is similar to the trend in the peak and average heat release rate data from the cone calorimeter. Scung reports similar results fo r polypropylene with additives or fillers, in their comparison between cone calorimeter and traditional tests (oxygen index, glow wire test, etc.) [229]. The correlation is very poor, however, between the LOI and rate of heat release for nylon-6,6 with silica gel / KjCOj additives. 

Figure 11.30 presents the heat release rate curves of polypropylene (PP) and its composites with 1 wt% CNTs or Ceo-rZ-CNTs. The incorporation of CNTs considerably reduced the peak heat release rate (PHRR) of PP (reduction around 66). At the same loading level. 

Polymer/fullerene [Ceol nanocomposites can be considered environmentally friendly alternatives to some traditional flame retardants. The presence of Ceo can markedly delay thermal oxidative degradation and reduce the flammability of polypropylene at very low loadings. It can decrease the heat release rate of polymeric materials by trapping the free radicals created through thermal degradation and combustion, and subsequently forming three-dimensional gelled networks. This network can increase the melt viscosity and consequently slow down combustion. Furthermore, the incorporation of Qo does not affect the physical properties of the polymer. 

It can be concluded that polyvinyl alcohol incorporated in nylon 6,6 reduces the rate of heat release and increases the char yield. Cone calorimetry data for permanganate-oxidized polyvinyl alcohol indicate an improvement in peak rate of heat release compared with polyvinyl alcohol alone, but the smouldering process is exothermic. Silicon/stannic chloride systems act as ecologically friendly flame retardants for both nylon 6,6 and polypropylene. 

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. 

The research [22] revealed high activity of nanoscale powders obtained by electrical explosion of wires (EEW) to reduce polyolefin flammability. Aluminum hydroxide Al(OH)3, bayerite P-AlaOs-SHaO, boehmitey-AlOOH, low-temperature modification of aluminum oxide y-Al203 produced by the method of electrical explosion of wires (EEW) [23, 24] were used as fillers in polypropylene. All additives are resistant to oxidation under heating up to 400 °C, all of them release water in endothermic decomposition, except y-Al203. The results of the smdy indicated that the oxidation rate decreases when polypropylene was filled with gibbsite and bayerite at concentration of 0.5-10 wt%. 

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