Healing efficiency

Fig. 25 Elongation at break of healed HM PAAm gels (2b) plotted against the healing time Co = 10 %, C17.3M = 2 mol%, SDS = 7 %, NaCl = 0.5 M. The horizontal line represents 2b of the virgin sample, denoted by 2b,o- The dashed area represents its standard deviation. The inset illustrates the healing efficiency of the hydrogels as a function of Co healing time = 30 min. From [33] with permission from the American Chemical Society...

F. 27 (a) Elongation at break of healed (2b) and original (2b,o) HM PAAm gel samples, (b) Healing efficiency ch for prepared using seven different hydrophobes in 7 % SDS + 0.5 M NaQ solution hydrophobe content = 2 mol%. From [34] with permission from Elsevier... 

The ratio of a physical property of a pristine material to that of a corresponding healed sample gives an indication of the success of healing. When expressed in percentage terms, this ratio is termed the healing efficiency ( /eff) [18]. An /e f value... 

Fig. 13 Healing efficiency of the tensile modulus as a function of healing time at 50 °C for a supramolecular blend comprising 7 and 8. (Reprinted with permission from [75], copyright 2009...

Fig. 21 Healing efficiency //eff as a fimction of healing time for a series of D-A containing supramolecular materials with increasing loading levels of CNCs. (Reprinted with permission from [84], copyright 2012 ACS)...

Healing experiments were conducted through established procedures the sample was cut, edges overlapped and the sample heated to 80 C for varying periods of time. All samples exhibited more than 90 % healing efficiency (//eff) for their tensile moduli (Fig. 21), although the time required to reach this value increased from about 5 min (at 1.25 wt% of CNCs) to about 20 min (at 10 wt% of CNCs). 

Healing efficiency was also measured by carefully controlled fracture experiments for both the virgin and the healed materials using a well established protocol [5]. 

The efficiency of the microencapsulation process for the above described formulation was not evaluated because for this new formulation other experiments on the self-healing efficiency were carried out. This analysis does not require a hard-working procedure if we use the infrared spectroscopy by way of example, hereafter, in the section "Methodologies" we report a procedure to analyze the efficiency of the microencapsulation process for microcapsules only filled with DCPD. 

Li, G., Ajisafe, O., and Meng, H. (2013) Effect of strain hardening of shape memory polymer fibers on healing efficiency of thermosetting polymer composites. Polymer, 54, 920-928. 

As discussed previously, the thermoplastic healing agent and the thermosetting SMP matrix need to have a certain miscibility in order to have a higher healing efficiency. If the two materials do not have any miscibility, it will be difficult for the thermoplastic molecules to diffuse into the thermosetting SMP matrix and establish physical entanglement. If the two materials are fully miscible, they will become a uniform mixture at a certain temperamre, which... 

The crack-closing ability of the composites with various CP contents can also be understood from the point of view of the stress recovery ratio. The stabilized programming stress (SPS) is the stress at point C. The stabilized confined recovery stress (SCRS) is the stress at point F. If the stress recovery ratio is defined as the ratio of the SCRS at point F to the SPS at point C, the stress recovery ratios of the composites are 66%, 60%, and 44% when the CP contents are 3%, 6%, and 9%, respectively. Therefore, we again see that the crack closing capability reduces as the CP content increases. However, this does not mean that the less of the CP content the better of the healing efficiency. The reason is that the CTH needs two steps, close and then heal. The above conclusion is based on the first step. For the healing step, it is obvious that the CP content must at a certain level. Otherwise there is no sufficient CP to fill in the narrowed crack and diffuse into the fractured PSMP matrix, that is, no healing. Therefore, an optimized CP content exists in practice. 

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