PSI - Issue 28

Anurag Singh et al. / Procedia Structural Integrity 28 (2020) 2218–2227 Anurag Singh/ Structural Integrity Procedia 00 (2019) 000–000

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Figure 8: With increase of degradation time, thinning and pigmentation of PGLA fibres

3.2. DSC results Table 2 shows the DSC results of PGLA fibres. T g and T m decrease with the increase of degradation stages; implying glassy to rubbery behaviour now happen at an earlier temperature. Percentage crystallinity of PGLA shows an increase at the beginning of the degradation stages, indicating the increase in the crystallinity of the PGLA samples with the degradation. As degradation starts to occur primarily in the amorphous region, causing it to deplete; thus increasing the relative crystallinity of PGLA. However, after 30 days of degradation, the cumulative depletion of the crystalline and amorphous phase takes place. However, for all cases, percentage crystallinity remains in the range from 30 - 40 % leading to a conclusion that degradation does not have a severe effect on the crystallinity of the PGLA fibres.

Table 2: DSC result of PGLA fibres

Degradation (in days)

Glass transition Tg (°C)

Melting temperature (°C)

Crystallinity (%)

0 5

40.2 39.9 39.6 39.3 38.9 37.4 38.4

203.3 203.6 203.8 204.5 197.2 189.6 204

34.33 36.14 40.80 37.13 37.79 40.96 32.31

10 15 20 30 40

4. Conclusions In this work, PGLA fibres are the blend of PLA (10%), and PGA (90%), they were subjected to progressive in-vitro degradation for 0, 5, 10, 15, 20, 30 and 40 days in PBS at 37 °C. Consequently, thermal transitions, namely T g and T m, were studied using DSC. PGLA fibres then subjected to uniaxial quasi-static tensile tests, mechanical properties of PGLA fibres was studied at different strain rates viz. 0.0001, 0.001, 0.01, 0.05 and 0.1 s - 1. From the thermal transitions, with the hydrolytic degradation, change of behaviour from glassy to rubbery behaviour happens at a lower temperature. As explained by Vieira et al. this lowering of glass transition temperature makes the polymer soft. From