Natural gum integrated polymer composites: A study of mechanical, water absorption, visco-elastic and dielectric properties

The study has explored the impact of adding gum from Moringa oleifera (MG) as a bio, based particulate filler to unsaturated polyester (PE) composites on mechanical, dynamic mechanical, thermal, dielectric, and moisture absorption behaviors. Composites with (5, 10, 15, 20, and 25 vol%) MG are made via vacuum assisted casting technique to determine the structure property relationship. Tensile strength obtained the peak up to 29.6 MPa at 15 vol% MG, which is also accompanied by enhanced flexural and impact performance, thus the efficient stress transfer at moderate filler loadings is confirmed. Dynamic mechanical analysis showed that with the increase of MG content, storage modulus has gradually increased, whereas the glass transition temperature only has slightly shifted up at 20 vol%, thus the interfacial interaction to polymer chain mobility is limited. Thermogravimetric analysis confirmed that thermal stability has been improved as the temperature of initial degradation has increased from 198° C for neat PE to 210° C at 20 vol% MG. Dielectric strength is also significantly rose from 19.3 kV/mm to 32.5 kV/mm, peaked at 20 vol% filler and probably resulted from elevated interfacial polarization and lower charge mobility. At 15 vol% MG, the interfacial compatibility between the matrix and filler are greatly improved, and the formation of microvoids are reduced resulting in the least water absorption. On the other hand, too much filler in the mix (25 vol%) caused particle agglomeration and led to a decrease in properties. In general, by utilizing 15, 20 vol% MG as the filler, one can achieve a simultaneously improved thermomechanical and dielectric performance, which demonstrates the viability of MG as a green reinforcement for polyester, based composites.