Synthesis of polymer-grafted thermally reduced graphene oxide by RAFT polymerization and their effects on properties of cured unsaturated polyester resins. II. Volume shrinkage, mechanical properties, thermal conductivity, and surface resistivity

Abstract

Effects of concentration (0–0.5 wt%) and type of thermally reduced graphene oxide (TRGO) and diblock copolymer-grafted TRGO, namely, TRGO-g-poly(butyl acrylate)-b-poly(methyl acrylate-co-glycidyl methacrylate) (TRGO-Gx-yK) with GMA compositions in P(MA-co-GMA) at 10 or 20 mol% (x = 10 or 20) and M_n for grafted polymer PBA-b-P(MA-co-GMA) at 30 K, 17 K, or 8 K (y = 30, 17, or 8), as low-profile additives (LPA) for unsaturated polyester resins (UP), on cured sample morphologies and properties of low-shrink UP after cure at 110 °C have been investigated. The decreasing order of compatibility for styrene (St)/UP/TRGO-polymer system before reaction, as predicted by the molecular polarity difference per unit volume between UP and grafted polymer of TRGO-polymer, showed that TRGO-Gx- 8 K > TRGO-Gx- 17 K > TRGO-Gx- 30 K, and TRGO-G20-yK > TRGO-G10-yK. The trend was in agreement with that of decreasing mutual miscibility of St/UP/TRGO-polymer system after cure at 110 °C, as observed from SEM and TEM micrographs. Adding 0.5 wt% of TRGO-polymer with M_n = 8000 for PBA-b-P(MA-co-GMA) and 20 mol% GMA in P(MA-co-GMA) as LPA can lead to a decrease of volume shrinkage by 64%, an increase of Young’s modulus by 12%, a slight decrease of tensile strength by 9%, a decrease of impact strength by 14%, an increase of thermal conductivity by 22%, and a decrease of surface resistivity by 99.9%, when compared with that of neat St/UP cured system. All properties depended on M_n and GMA composition for grafted polymer onto TRGO, and followed the decreasing order of TRGO-Gx- 8 K > TRGO-Gx- 17 K > TRGO-Gx- 30 K and TRGO-G20-yK > TRGO-G10-yK > TRGO.