In-situ polymerization of poly (butylene terephthalate) in presence of graphene-related materials: effects of nanoparticles structure and defectiveness on crystallinity and thermal conductivity of the relevant nanocomposites

Cyclic butylene terephthalate (CBT) were polymerized into poly (butylene terephthalate) (pCBT) in presence of different types of graphene-related materials, with variable size and structural defectiveness. Selected nanoflakes were annealed at 1700°C in vacuum, resulting in a reduced amount of defects, as consistently proven by several techniques [1]. Nanocomposites were prepared by pre-dispersing nanoflakes in CBT, followed by catalyzed ring-opening polymerization during extrusion. This technique allowed obtaining superior dispersion of nanoflakes compared to conventional melt processing methods, thanks to facile infiltration of CBT between the nanoflakes and further dispersion as a result of shear applied during mixing [2]. Thermal conductivity tests showed significant variability as a function of nanoparticle defectiveness, surface area and lateral dimensions. A dramatic increase in the thermal conductivity of the nanocomposite was observed in presence of annealed nanoflakes (up to 1.7 W/m∙K with 10 wt.% loading), compared to the pristine nanoflakes, evidencing the importance of using low defective materials. The study of nanocomposite thermal conductivity before and after polymerization was also addressed, to gain insight in the modification of nanocomposites morphology upon polymerization [3]. Furthermore, the effect of different processing parameters (time, temperature, shear rate) when preparing nanocomposites was addressed [4]. The presence of nanoflakes was found to strongly affect crystallization of nanocomposites evidencing for nucleating effects and the formation of a new high-temperature melting phase depending on the nanoparticle grade.