Mass loss indices

The reactivity of crystalline silicon with tetrafluoromethane, CF4, has been investigated by Holcombe et al. [36]. They found a mild exothermic reaction with onset at about 500 °C (peak at 530 °C) with no significant mass change and the onset of a strongly exothermic reaction at 990 °C (peak at 1020°C) with a significant mass loss indicative of volatile SiFx formation. Samples held under CF4 atmosphere for 75 min at 1030 °C exhibited both S-SiC and metastable carbon formation on the sttrface of Si. The exotherm at 500°C is believed to occur from highly reactive amorphous silicon present on the surface of crystalline Si. The formation of metastable carbon, particularly diamond phase on both Si and SiC substrates by thermal treatment in fluorocarbon atmosphere has been the subject of a disclosure by Holcombe et al. [37]. 

As seen before with the TG-MS coupling, a fraction of CO2 is detected during the second loss, and a fraction of CO during the third mass loss, indicating the presence of some trace of air in the furnace during the experiment. 

Basic Equations We make following assumptions that 1) the mass loss occurs steadily and 2) the flow is polytropic with index n within the secondary. In these assumptions, the energy conservation is given by... 

LOI limiting oxygen index (by ASTM D 2863 as volume fraction or vol %, may also be expressed in mass or molar units) m mass rate of burning or mass loss per time unit... 

To generalize the mass loss (or gain) rate term formulation, a staggered grid arrangement is used shifting the velocity index notation ... 

Metal oxide semiconductor chemical sensors in combination with MDA have been shown to be useful to estimate the oxidative stability of polypropylene during processing instead of traditional melt flow index analysis (50). An array of sensors was used to receive a detailed analysis of volatiles. At quality measurements of different poly(butylene adipate)s the use of indicator products has been proven better than analyses of the decrease in molecular weight or mass loss for early degradation detection. Adipic acid, quantified using gas chromatography, was then used as the indicator product [51]. 

Fig. 20. The border between radiative and adiabatic regions of the shocks in supernovae as a function of shock velocity and ejecta density profile index r] (p oc v v j. The boundaries depend upon the composition of the ejecta through which the shock may be propagating as also the mass loss parameter of the progenitor stellar wind and the ejecta velocity scale (Fig. courtesy T. Nymark [160])...

The specimen holder of an oxygen index apparatus can be coupled to a balance beam for continuous monitoring of the mass loss of the specimen during the combustion. Such an apparatus was used by Methven for studying polyester resins filled with alumina trihydrate and polyester fabrics finished with flame retardants. 

PEEK obtained from Intrinsic viscosity (m /kg) Glass transition temperature TgK Melt temperature Tm,K Cp., MPa Sp.% Mass loss temp., K Oxygen Index, %... 

Usually the TG curve should be determined at a slow heating rate, and E was estimated for low conversion (say mass loss 5%) by using the Ozawa-Flynn-Wall method. If we assume t( = 20 000h, Tf equals the thermal index of the material. With the use of higher temperatures, the shorter is the lifetime, as shown in Figure 5.1. 

The rod assemblies are usually exposed to the environment in question for 90 days, after which the wires are removed, cleaned, and reweighed. The percentage mass loss of the aluminum is the corrosion index for that time period. The data obtained can then be used to describe the severity of the atmosphere by comparing the values obtained to those empirically determined by exp>erience or by relevant testing. Environmental corrosivity is classified from negligible to very severe on this basis. Some typical atmosphere assessments made using this procedure are shown in Table 2. It has been found that a series of exposures must be made to fully characterize an environment, as the corrosion varies with the season of the year and the exposure is only for three months. 

A simplified model of ignition and burning of polymers which docs not require one to work with partial differential equations has been proposed by Rychly [49]. It was applied to the combustion carried out in a mass loss cone calorimeter system [50]. A series of simulations of heat release rate curves was performed for polymers with intumescent additives [51]. The model was also used for the prediction of limiting oxygen index (LOI) [52],... 

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