Overall Accelerated test

Anticipated problems and counter measures for the listed protocols have been included in individual steps of the basic protocols. In addition, a detailed troubleshooting section for particle size analysis can be found in unit d.u however, the difficulty of properly conducting accelerated tests should again be stressed. While the method is extremely useful, as it can drastically reduce the required time for the overall test, results may not accurately reflect... 

The overall efficiency o a catalyst Is defined in terms of activity, selectivity and life. Of these, catalyst life has received by far the least attention in the literature, partly because life testing makes heavy demands on resources and partly as a result of the fact that accelerated testing may be unreliable. Nonetheless, catalyst life Is a factor that can control the economic viability of industrial processes 1]. 

Furthermore, this value is not far away from the value which could be deduced from the overall bending test, assuming each corner would take 1/4 of the total load. In fact as the panel fractured at around 35-45 kN, the maximum load capacity of the corner which could be expected would be approximately 8.75-11,25 kN. These values are lower than the values obtained in the individual tests. This can be explained by the fact that in the overall test, once one corner began to crack it induced in the component additional moments and forces which had the effect of accelerating the failure mechanism and thus reducing the ultimate load. This was not the case in the corner test because the corner was isolated , even if it was still attached to the rest of the panel. 

The problem of non-equivalent kinetics is inherent to polymer reactions in solids [2], In this case particles existing in different surroundings react with different rate constants. As a result, the most active particles will be removed from the reaction, and the overall rate constant will decrease with time. On the other hand, relaxation processes in polymers restore the initial distribution of particles and so their reactivity. Thus the kinetics will depend on the relation between the rate of the chemical reaction and the rate of the relaxation processes [3], This fact also makes it necessary to reconsider critically the validity of extending the results of accelerated tests for polymer ageing. 

The same undesired effect—oxidative degradation catalyzed by impurities— was noticed when talc (hydrated magnesium silicate) was employed in such PP formulations up to 15 wt% [84]. The study concluded that the outdoor conditions concurred to the overall degradation, despite the low energy of the UV radiation as compared with the accelerated test. It was demonstrated that the presence of talc did not inhibit the degradation rate and the photochemical behavior was severely affected by the presence of the acidic rain. 

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