Poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) are the most important and most used commercial thermoplastic polyesters. PBT has the advantages of rapid crystallization rate and good mouldability properties compared to the PET. Besides, the rigidity of PET is superior to those of PBT. The blending of these two polymers is advantageous in that it is possible to obtain a new material with extensive and comprehensive properties [1]. Due to the literature research, blends of PET and PBT shows more advanced properties like higher tensile strength (approximately 3-4 times more compared to the pure component), higher flexural modulus and higher impact strength comparison to the virgin polymers [2,3]. The DSC studies show the significant increase of crystallinity due to the decrease of crystallization temperature [4]. In addition, in recent years, much attention has been given to graphene/polymer nanocomposites owing to improve the thermal conductivity and stability, mechanical and flame retardant properties of polymers [5]. Like the other nanofillers, interfacial interactions are the main parameter of graphene/polymer nanocomposites. Because these parameters directly influence the properties of the prepared nanocomposites [6]. The mechanical properties of composites become stabilized by graphene oxide (GO). Goal: In this work, it was aimed to investigate the effects of different process parameters on the properties of reduced graphene oxide (RGO) reinforced PET/PBT composites. Extruder screw speed and retention time for melt mixing method were selected as process parameters. Then, a series of reduced graphene oxide (RGO) reinforced PET/PBT composites were produced at two different screw speed and retention time. Method: Firstly, PET/PBT (95/5) blends were prepared as control samples and after that two different RGO ratio added to the blend as 0,5 wt.% and 1 wt.% respectively. All composites were compounded on a laboratory scale co-rotating twin-screw mini-extruder (Micro-compounder). Firstly, the control samples were processed screw speed is fixed at 100 rpm by using different retention time as 3 min and 4 min respectively. After that, screw speed is changed to 75 rpm by using 3 or 4 min. retention time. RGO reinforced PET/PBT composites are produced in the same way. Samples were subsequently injection molded by a laboratory scale injection molding machine with a 10 bars injection pressure. Discussion: Characterization of the composites were performed by differential scanning calorimetry (DSC), tensile test and thermogravimetric analysis (TGA). Results: The Tg values of the composites significantly is effected from process parameters. It has changed as approximately 20 0C. The highest Tg value was obtained for 1wt.% RGO including PET/PBT composite at 100rpm/3min. That can be observed that 0,5wt.% RGO addition increased to percentage crystallinity value of PET/PBT composite compare to the other composites. The highest crystallization degree at 75rpm/ 4min for 0,5wt.% RGO including PET/PBT composite. The maximum tensile strength observed for PET/PBT blend at 100rpm/ 3min (59,76 MPa) among the blend samples. The best tensile strength value was seen for 0,5GO/ 100rpm/ 3min composites (54,10 MPa) into the composite samples. Due to the TGA, degradation beginning temperature (Tonset) of composites has changed between 383 and 403 0C. It is effected from process parameters. Also, minimum char residue was observed at 100rpm/ 3min (2,3 %) for PET/PBT blend and maximum char residue percentage observed for 1wt.% RGO including PET/PBT composite at 100rpm/ 3min (21,2 %).
Keywords: Poly(butylene terephthalate), Poly(ethylene terephthalate),Thermal Conductivity, Thermal Stability.
|
