PLA PBAT Blend Foams

Poly (butylene adipate-co-terephthalate) (PBAT) is an interesting polymer [116,117] and has attracted more attention. PBAT is also a biodegradable poljmier, which has proper viscosity and elasticity. Moreover, the balance of biodegradability (e.g., life time) and its physical properties (e.g., thermal and mechanical properties) can be adjusted by controlling the molar ratio of comonomers in the copolymer [118,119]. It has been reported that the aliphatic/aromatic copolyester with aromatic units within the range of 35 - 55 mol% offers an optimal compromise of its biodegradability and physical properties. 

Yuan et al. [120] has reported the research on PLA/PBAT blend foam. Maleic anhydride is used to enhance compatibility between PLA and PBAT. The compatibilization mechanism of maleic anhydride (MAH) is that MAH enhances intermolecular force by forming hydrogen bond between grafted MAH and polymer backbone. Grafting MAH onto PLA and PBAT is performed by reactive extrusion, which can improve the interfacial adhesion between PBAT and PLA matrix. In order to increase the maleicing reaction activity, a free radical initiator, 2, 5-dimethyl-2, 5-di-(/er/-butylperoxy) hexane (LlOl), can be used. 

PLA and PBAT are premixed as pre-foaming master batches. Maleic anhydride and LI01 are then added to PLA/PBAT blend pre-foaming master batches as a multi-compatibilizer. PLA/PBAT foams are prepared by reactive extrusion. AC is added as blowing agent and nano-Si02 as nucleation agents. The formulations for all experiments are shown in Table 5.11. 

Rheological properties are important for foam extruding process. Dynamic frequency scanning is performed at a definite temperature 170 C and strain range. 

Loss modulus represents the loss of energy as heat during the deformation of materials. When loss modulus becomes low, damping loss factor decreases, which means the material is closer to ideal elastic material. The loss modulus of maleicing PLA/PBAT blends is higher than that of both PLA/PBAT blends wifliout maleicing and plain PLA, which means that better impact resistance of modified PLA foams can be achieved. 

---