INDEX tensile behavior

Therefore, plasticized compositions using DOP and zinc stearate at various levels were prepared by melt blending, and their tensile properties and flow behavior are shown in Table II. It is seen that the addition of zinc stearate at modest levels (5 and 10 pph) markedly improves melt flow as measured by melt index. Furthermore, this improvement in flow is achieved without a loss in tensile properties in fact, a modest improvement is noted. For comparison, the unplasticized, unsulfonated PS exhibited a melt index of 30 under these conditions. Therefore, a combi-... 

In products with a large wall thickness, the influence of weathering is often limited to a surface layer, either due to limited oxygen diffusion or to limited UV penetration. The depth of this layer may be small ( 0.5 mm) compared with the whole wall thickness ( 4 mm) but it can causes brittle fracture. Mechanical behavior depends on the oxidation (degradation) profile, a critical degradation profile accounted for the failure of samples, that is time of failure. Tensile tests were performed on films microtomed from the samples [39]. The density of weathered samples can increase because of chemicrystallization, increase in polar groups, oxygen uptake or the loss in volatile products. The decrease in the nominal strain corresponded to an increase in the vinyl index and in the density. The carbonyl index showed too much scatter. 

To date, all index tests are examined at standard temperatures, but in certain areas, GTXs are installed at low temperatures and at elevated temperatures. Especially the stress—strain behavior of PP GTXs at very low temperatures is an issue, eg, in Nordic countries. In this case a tensile test somehow becomes a performance test. 

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