# Poly(lactic acid)-Based Blends: A Comprehensive Review
## 6 Composites of Poly(lactic acid) with Poly(3-hydroxybutyrate)
[PERSON] et al. [99] have investigated the compatibility of PLA and PHB by block copolymer of ethylene oxide/propylene oxide in the form of flakes and a mixture of two liquid natural surfactants with variable lipophilic-hydrophilic composition. A morphological analysis of the compatibilized blends has shown that liquid surfactants are more effective than solid copolymers in improving homogeneity, as also evidenced by the results of rheological measurements. In addition, thermal analyses have shown that the presence  
Figure 15: SEM images of the blends of PLA/PHB: 100/0 (**a**), 0/100 (**b**), 75/25 (**c**) [98]. of both types of compatibilizers causes an increase in the degree of crystallinity of the polymers. A noticeable increase in an elastic modulus value for the compatibilized blends has been identified in comparison with pure analogues. It has been shown that both selected surfactants improve the compatibility of PLA and PHB and give them improved mechanical properties. In the further study [100], the ability of PHB acting as a nucleating agent for PLA has been investigated. It has shown a positive influence of PHB on the mechanical resistance and barrier properties of PLA. [PERSON] et al. [101] have developed the materials on PLA, PHB, and cellulose nanofibrils (CNF). It has been proven that the mechanical properties of neat PHB improved markedly due to the good intermolecular interaction between PLA and PHB. The thermal stability of PHB has increased by the addition of PLA. The dynamic mechanical and rheological properties of PHB generally improved with adding both PLA and CNF. [PERSON]. [PERSON] et al. [102] have reported the development of the composites with improved impact strength due to the preparation of triple mixtures with PHB and two flexible-chain polyesters obtained from succinic acid, namely, poly(butylene succinate) (PBS) and poly copolymer (butylene succinate-co-adipate) (PBSA), by reactive extrusion. The results obtained have shown that the introduction of flexible-chain polymers improves the toughness and elasticity of PLA/PHB blends. The addition of epoxidized vegetable oils (soy and olive) slightly improves the compatibility of all three polyesters in the blends, which gives additional improvement in plastic properties compared to the original triple mixtures. In addition, the operating temperature range of these materials is expanding. [PERSON] et al. [103] have studied the triple blends of biodegradable polymers PLA/thermoplastic starch (TPS)/PHB with a constant content of TPS (50 wt.%). The PHB content in the mixtures varies from 0 to 20 wt.%. The results showed that differences in morphology strongly affect the mechanical properties of the studied materials with the same composition. [PERSON] et al. [104] have studied the blends of PLA, PHB, polyethylene glycol (PEG) and corn starch (CS) with PEG in three different concentrations (2, 5, and 10 wt.%). The glass transition temperature and crystallization temperature have decreased with increasing PEG content, while the thermal stability of the materials did not change. The physical properties have turned out to be optimal at a ratio of 70 PHB/30 CS. Starch granules act as nucleating agents for PHB. Intermolecular hydrogen bonds have been observed in the blends, and the bonds are stronger between PHB and starch with a high amylose content. It has been determined that PLA and PHB are not compatible; however, they demonstrate some molecular interaction. PHB enhances the recrystallization of PLA. The addition of PLA improves the mechanical properties of PHB. The blend of 75 PLA/25 PHB demonstrates significantly high tensile properties compared to pure PLA. The biodegradability of the mixtures improved with an increase in the PHB content. [PERSON] et al. [105] have obtained the blends of PLA/PHB plasticized with lactic acid oligomer (LAO) at three different concentrations (15, 20, and 30 wt.%) to improve processability and mechanical properties.