The effect of carbon black percentage on mechanical properties and microstructure of polybutylene terephthalate/polyamide 6/carbon black blends

This study focuses on analyzing the influence of carbon black (CB) on Polybutylene terephthalate (PBT)/Polyamide 6 (PA6) blends. This study aims to solve the source of waste from toothbrush filament during production. This PBT/PA6 mixture does not meet the mechanical properties due to the incompatibility of these two plastics, which means this waste must be discarded and cannot be reused. When combined with CB, it creates a new type of plastic with more stable mechanical properties that can be applied in many areas of life and, at the same time, helps manufacturing businesses save on waste treatment costs. To create these PBT/PA6/CB blends, the research team used injection molding with a PBT/PA6 ratio of 75/25 combined with 0, 4, 8, and 12 % carbon black. The tensile and impact strength were tested according to the ASTM D638 and ASTM D256 standards. The results found that when adding 4 % CB to the PBT/PA6 plastic mixture, the tensile strength decreased from 34.9 to 34.8 MPa. Meanwhile, the tensile strength is improved when adding 8 % CB (35.3 MPa). At 12 % CB, a difference in tensile strength results, decreasing to 29.7 MPa. This result shows that the ratio 75/25 can give the best tensile strength value of the PBT/PA6 mixture with 8 wt. % CB. The impact strength was 3.5, 2.9, and 2.7 kJ/m2 according to 4, 8, and 12 % CB samples. Mechanical quality tests have shown that the tensile strength is improved when combining CB into the PBT/PA6 mixture, but the impact strength is reduced. SEM results show that most CB interacts with PBT/PA6 mainly because the PA6 particles are spherical and tend to separate easily from the mixture. The research found that increasing CB density worsens the bonding ability between PBT and PA6. These results help us provide experience for the most appropriate application for each purpose