Virgin tensile strength

During the first 100 h of oxidation there were no significant differences between the samples, i.e. they all seemed unaffected by thermo-oxidation and no influence of repeated processing was found [65]. However, after 500 h of thermo-oxidation, all recycled samples showed a marked deterioration in tensile strength whereas the virgin material remained unaffected. The magnitude of the decrease in tensile strength corresponded well to the number of times the material was extruded. After 1200 h of thermo-oxidation the deterioration in mechanical properties was even more pronounced and at this point the polyamide 6.6 recycled three times retained only 20% of its... 

A good correlation between the formation of degradation products and the simultaneous reduction in tensile strength during thermo-oxidation was observed [65]. Figures 12 and 13 show the increase in the relative amount of the most abundant thermo-oxidation product, l-pentyl-2,5-pyrrolidinedione and the simultaneous decrease in tensile strength for virgin and once recycled material, respectively. 

Fig. 12 Correlation between formation of 1-pentyl-2,5-pyrrolidinedione and simultaneous decrease in tensile strength for virgin polyamide 6.6 during thermo-oxidation at 100 °C. Reprinted from [65] with permission of John Wiley Sons, Inc. John Wiley Sons, Inc (2002)...

The mechanical properties of virgin PP, treated and untreated sisal PP composites, as a function of fiber loading, are presented in Table 9.3 [71]. It is evident that the mechanical properties of the composites increased linearly with the increase in fiber loading from 6.8 to 21%. Tensile strength increased to about 64%, whereas flexural and impact strengths increased to about... 

Provided that the energy of activation is known for the base polymer, this data can be plotted in a diagram with the selected life criterion, in this case 50% of the tensile strength of the virgin material, as displayed in Figure 2.14 to obtain a... 

Figure 7.11 Tensile strength for 100% and 25% recycled short-fibre reinforced PA 66 (normalised to the value of virgin material) versus ageing time at 140°C [21].

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