# Poly(lactic acid)-Based Blends: A Comprehensive Review
## 6 Composites of Poly(lactic acid) with Poly(3-hydroxybutyrate)
It has proven to be a good plasticizing effect of LAO (glass transition temperature has significantly decreased and plasticity has increased). At the same time, the barrier properties have improved. The blend of PLA/PHB with 30 wt.% OLA has been chosen as an optimal composition for food packaging, since it provides an optimum between plasticity and barrier properties for oxygen and water vapor with almost no migration of OLA. [PERSON] et al. [106] has studied the thermal degradation of PLA/PHB mixtures with the addition of Ag and Cu nanoparticles. The blended materials demonstrate a fairly high rate of degradation with an exception of the composition of PLA/PHB = 70/30. According to the authors, it is evidence of the best compatibility of polymers in this mixture. The PLA/PHB/nanoparticle blends have showed a higher value of Young's modulus. TGA shows two different decomposition temperatures for all mixtures and a mass loss proportional to the percentage of the initial components of the mixture; however, for the blend of 70 PLA/30 PHB, decomposition intervals have not been observed, which may indicate some compatibility (Figure 16). [PERSON] et al. [107] have attempted to explain the kinetics and mechanism of thermal decomposition of PHB and PLA in the blends. They concluded that the thermal stability of PLA in a mixture with PHB is lower than that of pure PLA, in contrast to PHB with higher thermal stability in a mixture with PLA. Consequently, the mechanism of thermal decomposition of PLA/PHB mixtures should be considered as a complex physicochemical phenomenon (Figure 16). Moreover, the choice of additive strongly affects the thermal stability of the mixtures. The method of processing and localization of the additive in different phases or at the interface of phases are factors determining the ultimate heat resistance of the mixture. [PERSON] et al. [109] have shown that PLA and PHB are not compatible, but there is a molecular interaction between these two polymers in the entire range of compositions. It has been noted that the crystallization of PLA increased in mixtures of PLA/PHB with an increase in the content of PHB to 25 wt.%. It has been established that, according to rheological and thermal properties, the blends with a content of 20-25 wt.% of PHB are the most promising. Figure 16: Typical of TGA (**a**) and DTA (**b**) of PLA/PHB blends [107; 108]. [PERSON] et al. [110] have developed 3D printing filaments from mixtures of PLA/PHB with PEG for use in 3D printing technology as an alternative material for making a model of a bone frame. The fibres were manufactured with a ratio of PHB/PLA: 100/0, 90/10, 70/30, 50/50, 30/70, 10/90 and 0/100 wt.%. The results of the DMA showed that the optimal 3D printing temperature for all mixed rods is 190 \({}^{\circ}\)C. Changes in thermal properties indicate partial compatibility of PHB and PLA in the mixtures. PLA plays a key role in improving the mechanical properties of PHB (Figure 17). [PERSON] et al. [111] have conducted a comprehensive in vitro study of the characteristics of a mixed material based on PLA, PHB, and thermoplastic starch (TPS) in order to assess its potential for use in the field of tissue engineering. The authors focused on the biological behaviour of the material, mechanical, and morphological properties, as well as the possibility of manufacturing a frame from a mixture using a 3D printer. It has been found that the materials have no toxic effect on cell culture and, therefore, can be considered biocompatible. In addition, the mixture is applicable for 3D printing. The printed frames had a highly porous morphology and were also capable of absorbing water. The work demonstrates that cells can attach and multiply/reproduce on the surface of the frame. The material can be successfully used in tissue engineering.