PLA/PHB blend

Table 11.6 Mechanical properties of V-PLA, V-PHB, PLA/PHB blends and blend nanocomposites [35]...

A similar increase in impact strength of the blend was also reported with the incorporation of MA. The notched impact strength of V-PLA increased from 25.7 J/m to 49.2 J/m in the case of PLA/PHB blend with 7 wt% of MA concentration. The result is around 99% higher than that of V-PLA, which further reveals the fact that compatibilization of PLA and PHB with MA results in the formation of a bridge-like network at the interface, thus... 

PHB is accumulated by a large number of bacteria as an energy and carbon reserve. PHB is a biodegradable and biocompostable highly crystalline thermoplastic with very low water vapor permeability, similar to that of LDPE [105]. PLA/PHB blends have been studied with the goal of producing PLA-based materials with different physical properties and improved processability [106]. 

Arrieta et al. [97] in the incorporation of CNC on the PLA-PHB blend analyzed the presence of CNC and found that it positively affected the interaction between PLA and PHB. 

Copolymerization offers considerable potential of engineering the properties and degradation rate of PHB over a broad range. HB has been copolymerized with a number of related species, e.g., e-CL, LA, 4-hydroxybutyrate and hydrox-ypropionate. Furthermore, a number of PHB blends have been prepared. Miscibility of PHB with PCL, PLA, POE, poly(mandelic acid), and poly(sebacic anhydride) has been demonstrated. PHB-poly(sebacic anhydride) blends offered controlled release of bupivacaine at a rate dependent on the PHB content [141]. Blending of P(HB-co-HV) with natural polysaccharides was proposed as a way... 

MA restricts various -C=0 functionalities present in both polymers to a uniform vibrational frequency. Presence of such kinds of interactions results in better miscibility in the blend, as proven by the sharp single peak of aroxmd 1725cm for carbonyl groups (-C=0) in the FT-IR spectra of PLA/PHB/MA. 

Figure 11.9 (a) Biodegradable bottles from PLA/C30B nanocomposite and (b) biodegradable film from PLA/PHB/MA blend [73]. 

It is known that PLA forms miscible blends with polymers such as PEG [53]. PLA and PEG are miscible with each other when the PLA fraction is below 50 per cent [53]. The PLA/PEG blend consists of two semi-miscible crystalline phases dispersed in an amorphous PLA matrix. PHB/PLA blends are miscible over the whole range of composition. The elastic modulus, stress at yield, and stress at break decrease, whereas the elongation at break increases, with increasing polyhydroxybutyrate (PHB) content [54]. Both PLA/PGA and PLA/PCL blends give immiscible components [55], the latter being susceptible to compatibilization with P(LA-co-CL) copolymers or other coupling agents. 

Figure 9.6 SEM micrographs of biocompati- PLA in the blend 20wt%, (b) PCL of 20 wt%, ble biodegradable polyesters after their melt (c) PHB after melt spinning from a PVA/PHB blending with PVA with extrusion, cold draw- blend 90/10 by wt%, and (d) the same at ing, and extraction with water, (a) Amount of higher magnification.

A., and Ray6n, E. (2014) Ternary PLA-PHB-Limonene blends intended for biodegradable food packaging applications. Eur. Polym. J., 50, 255-270. 

The properties of polyanhydrides ean be modified by ehanging polymer composition and structure. This is obtained by realizing copolymers, polymer blends, erosslinking between ehains, partial hydrogenation and reaction with epoxides. Low moleeular weight PLA, PHB and PCL are miscible with polyanhydrides whereas high moleeular weight polyesters are not. 

Albertsson, 1999). In general, polyanhydrides of different structures form uniform blends with a single melting temperature. Low molecular weight PLA, PHB, and pol-y(caprolactone) (PCL) are miscible with polyanhydrides, while high molecular weight polyesters M > 10,000) are not compatible with poly anhydrides. 

Figure 9 shows the remarkable toughness improvement for PLA as a small amount of PHBHx is added. The fortuitous increase of the property of PLA/PHBHx blends is believed to be related to the suppressed crystallization of very finely dispersed PHA particles. It is well known that PHAs do not readily crystallize when they are very finely dispersed as discrete domains ( S fim). The retardation of the crystallization is a result of the relatively low frequency of spontaneous nucleation of PHAs. The nucleation rate of PHB at biological temperatures, for example, is estimated to be less than one event per cubic millimeter per second (75). Therefore, under very finely dispersed state, the probability of nucleating all the segregated PHA particles becomes extremely low. Indeed this is how bacteria maintain PHA granules in their body in the amorphous state over their lifetime (76). 

The FT-IR transmission spectrum of a PHB/PLA 50/50wt% polymer blend is shown in Figure 22.7. In order to prepare the FT-IR contour plots for PHB, the 2x v(C=0) absorption band was integrated between 3449 and 3426 cm, while for PLA the integrated intensity between 3524 and 3490 cm was evaluated with a common baseline in the region of 3550-3410 cm. In order to visualize the changes in phase separation as a function of temperature, PLA/PHB and PHB/... 

At 175 °C neither in the visible nor in the FT-IR images of the PLA- and PHB-specific regions can the structures of phase separation be detected, which confirms that both phases of the PHB/PLA polymer blend are molten and that a more-or-less homogenous liquid phase remains. 

Figure 22.14 Visual images (left), PLA/PHB band ratio FT-IR images (center) and PHB/PLA band ratio FT-IR images (right) of the PHB/PLA (50/50wt%) blend film at (a) 25°C, (b) 125 °C, and (c) 165 °C.

Figure 22.17 PHB/PLA ratio images of a 175 (im x 175 nm area derived from the 1730/1776 cm (top) and from the 843/878 cm (bottom) specific band pairs of the PHB/PLA polymer blend measured at 25 °C and 165"C...

Figure 7.11 Visual images, PLA-PHB band-ratio, and PHB-PLA band-ratio FTIR images of the PHB-PLA (50 50 wt%)-blend film at 25 (a), 125 (b), 165 (c), 170 (d), and 175 C (e). Vogel et al. [46], Reproduced with permission of the American Chemical Society. (See color plate section for the color representation of this figure.)...

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