| Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV) is a kind of thermoplastic biodegradable polyesters, with the mechanical properties similar to polypropylene (PP). It could ideally substitute for petroleum based conventional plastics and attracts a great deal of domestic and international researchers’ attention. However, the application of PHBV is seriously restricted by its inherent disadvantages, one of which is high crystallinity and large spherulites, which resulting its rigid and brittle. Being one of the most useful conventional engineering plastics, PP has a great number of advantages and could improve the toughness of another biomaterial, Polylactic acid (PLA), effectively, which makes PP an ideal material to melt blend with other polymers and produce more excellent blends in all directions.In this work, PHBV was blended with PP at various ratios with a melt-blending technique in an attempt to improve the mechanical properties of PHBV. Maleic anhydride(MAH)-grafted PP(MAH-g-PP) was used as the reactive compatibilizer to induce miscibility in the blend. The main works and conclusions were listed as following:1. Via the orthogonal experiment, the optimal combination of the screw speed, melt-blending temperature and time was confirmed as50rpm,180℃and4min, respectively. The results of mechanical tests showed that the toughness of the PHBV/PP blends containing2.5wt%and5wt%PP improved much more compared to the pure PHBV. The elongation at break of PHBV/PP/MPP blends increased with the increasing amount of MPP and the breaking elongation ratio of the blends containing2.5wt%PP and3wt%MPP increased by315.09%and116.7%compared to the pure PHBV and the uncompatibilized blends, respectively. The thermal gravimetric analysis (TGA) results revealed that the initial degradation temperature and the maximum decompose temperature of the blends was improved with the addition of PP. Therefore, the addition of PP improved the thermostability of PHBV, which is extraordinarily important to their melt blending processing. Only one thermal degradation of the blends happened after the cooperation of MPP, which means the effect of MPP on the incompatibility of PHBV and PP.2. Scanning electron microscopy(SEM) showed that the interface of PHBV and PP phase was very distinct, indicating the incompatibility of them. PP phase was well-distributed with nanoscale within the PHBV matrix. After the addition of MPP, the interface of the two phases became ambiguous and the domain size of the dispersed phase decreased by35.35%. The plastic deformation of PP was observed with incorporation of MPP, proving the adhesive between the interface of PHBV and PP was enhanced by MPP. The results of fourier transform infrared spectroscopy (FTIR) showed that there was no interaction force between PHBV and PP. In PHBV/PP/MPP blends, the carbonyl group of MAH acted with the end hydroxyl of PHBV, improving the incompatibility of PHBV and PP.3. The results of differential scanning calorimeter(DSC) demonstrated that melting point of the blends decreased gradually with the increasing amount of PP while the crystallization temperature increased, and the crystallinity of PHBV in PHBV/PP blends was increased, which was explained by the results of polarized optical microscope(POM) tests that the tiny sphrulites of PP acted as the crystal nucleuses of PHBV, enhancing the crystallizing ability of PHBV while destroying its crystal structure and finally decreased its melting point. In PHBV/PP/MPP blends, that melting point of the blends decreased gradually with the increasing amount of MPP while the crystallization temperature increased. However, POM showed that MPP weakened the crystallization of PP, indicating that the main reason of the improving toughness of PHBV/PP/MPP blends was the improvement of the adhesive between the interface of PHBV and PP, which resulted in the plastic deformation of PP particles in PHBV matrix in the effect of tensile stress. |
PDF Full Text Request