It is challenging to obtain balanced properties with good stretchability, mechanical stability, small response time, high output voltage, and finally optimum mechanical hardness. Thus, the present work supports that balanced properties can be obtained with good interfacial interactions during composite fabrication. Here, the ingredients involve the addition of mild functionalized graphite nanoplatelets (mf-GNP), silicone oil, and vulcanizing agents into the silicone rubber (SR) as a rubber matrix. The justification for the “mild” functionalization of GNP was validated through spectroscopic studies in this work. Robust functional groups like carboxyl (O-H), carbonyl (C=O), epoxy, and alkoxy (C-O) on the surface of mf-GNP expect improved interactions with the SR matrix. Moreover, results show that adding 5 per hundred parts of rubber (phr) of mf-GNP in the SR matrix increases compressive modulus, hardness, and stretchability. However, the addition of a different content of thinner lowers the hardness making the composites mechanically soft and ultrasoft. For example, the hardness was 25 (control sample), 27 (5 phr of mf-GNP filled sample)., 24 with 10 phr thinner (T10 sample), and finally 16 with 30 phr of thinner (T30 sample). The results further insight the stretchability was increased with different contents of mf-GNP or thinner in the SR matrix. For example, stretchability was 111% (control sample), 144% (5 phr of mf-GNP filled sample), 156% (T10 sample), and finally 129% (T30 sample). Also, the energy harvested tests were performed to obtain output voltage and response time for industrial applications of this work. For example, the response time at 30% compressive strain was 154 milliseconds (ms) (5 phr of mf-GNP filled sample), 184 ms (T10 sample), and finally 225 ms (T30 sample). The power density was ~2.65 nanowatt per centimeter square (nW/cm2) (mf-GNP sample), ~8.34 nW/cm2 (T10 sample), and finally ~1.69 nW/cm2 (T30 sample). Moreover, the piezoelectric coefficient was 14.5 picocoulomb per Newton (pC/N) (mf-GNP sample), 66.2 pC/N (T10 sample), and finally 19.37 pC/N (T30 sample). Finally, the results support the T10 sample as best with the balance of good stretchability, relatively optimum response time, higher durability, and finally good output voltage.
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