Effects of Chitosan Nanoparticles and 4,4′ Methylene-Diphenyl Diisocyanate on the Polylactic Acid/Poly (Butyleneadipate-Co-Terephthalate) Composite Properties

Polylactic acid (PLA) is considered a mature alternative to synthetic plastics made from petroleum by-products, possessing the advantages of good mechanical strength. However, it also has some disadvantages such as brittleness and low toughness. In order to overcome and improve some of these unfavorable properties, PLA/PBAT composites were prepared by blending PLA with Poly (butylene adipate-co-terephthalate) (PBAT), and adding 4,4′-methylene diphenyl diisocyanate (MDI) and chitosan nanoparticles (ChNPs) as compatibilizers to investigate the effects of different compatibilizers on the properties of the composites. The main observations are as follows: FT-IR indicated that MDI did not add new groups, while the addition of ChNPs added a substantial amount of hydroxyl and methylene groups. The addition of both MDI and ChNPs did not have any effect on the crystalline shape of the composites, but could potentially reduce their crystallinity, increase the melt peak temperature, wet the boundary of the PLA and PBAT phases, decrease the size of the dispersed phases, reduce the number of dispersed phases, and improve interfacial compatibility. The incorporation of MDI increased the tensile strength from 13.02 MPa to 19.24 MPa, whereas the addition of ChNPs substantially enhanced the elongation at the break from 3.84% to 19.24%. Furthermore, the inclusion of MDI conferred enhanced moisture resistance, whereas the addition of ChNPs seemed to weaken the resistance to moisture.