**4. Fractography**

The purpose of the fractography was to evaluate whether the fracture surfaces added any additional information to the mechanical properties already measured. Four sample pairs were chosen to judge key comparisons:


The effect of PCR was gauged by comparing two unaged, white samples with the same MFR. One sample was a conventional PC, while the other was 50% PCR.

From **Figure 8**, both samples have ductile features such as hackle lines, chevron marking (V shaped features) [20] visible across their fracture surfaces. This is consistent with the fact that there were no mechanical property or molecular weight differences between these two samples. The elongation at break and tensile strength between unaged conventional PC and 50% PCR were comparable. Extensions at max load were 20.19 and 19.25 mm and max tensile strength were 67.3 and 65.52 MPa for those specific unaged conventional PC and 50% PCR samples.

The effect of aging on white PCs was determined by comparing two white conventional PC samples with the same MFR. One sample was unaged, while the other was aged for 500 hours at 60°C 90% RH.

From **Figure 9**, the differences in the fractography are more obvious. While the unaged sample has large regions of ductility, the aged sample shows a smoother surface, which indicates a more brittle material. As well, there is an obvious smooth initiation site in the middle of the right half of the surface, which indicates a slower crack growth. This sample still has chevrons and ductile features. The sample on the right (tensile strength: 63.32 MPa) had degraded mechanical properties as

#### **Figure 8.**

*A comparison of conventional and 50% PCR PC fracture surfaces.*

*Effect of Environmental Aging on Tensile Properties of Post-Consumer Recycled (PCR)… DOI: http://dx.doi.org/10.5772/intechopen.99528*

#### **Figure 10.**

*A comparison of unaged and aged black 75% PCR PC fracture surfaces.*

compared to the unaged sample (69.72 MPa), and this is consistent with the differences in the surface morphology.

Finally, the effect of aging on black PCR samples was evaluated. One sample was unaged, and the other was aged for 500 hours at 60°C 90% RH.

Similarly, to the comparison between aged and unaged white samples, the black 75% PCR samples have differences between the aged and unaged samples (**Figure 10**) that agree with the differences in mechanical properties between these two sample groups. The unaged sample has large ductile features, whereas the aged sample has more drawing.
