Blends with Poly lactic acid

The miscibility of solution cast blends of poly(lactic acid) (PLA) and PVB has been reported (23). PLA was blended with PVB through a solution casting method using chloroform as solvent. 

The films obtained were characterized for miscibility by DSC, tensile testing and fourier transform infrared spectroscopy spectroscopy. DSC measurements showed that the glass transition temperature associated to PLA and PVB are not dependent on the composition of the blend. Two glass transition temperatures in the blends indicate an knmiscibility of the base materials. Mechanical analysis showed that the tensile strength and elongation decreased due to blending (23). 

Blends of poly(caprolactone) (PCL) with PVB were studied for biodegradation in soil and by bacterial strains of Bacillus subtilis and Escherichia CoU. Films of PCL/PVB blends of different compositions were buried in soil in the laboratory and in the outside environment 

Blends with a low polyester concentration of less than 30% PCL were clear and transparent and no spheruHte formation was observed. Above 30% PCL spherulites could be observed. The size of the spherulites increased with increasing PCL concentration. 

The films were examined for changes in the physical appearance and mass loss every week. Weight loss was observed in all the blends. Blends rich in PCL showed more degradation, which was faster in the natural environment than in the laboratory. 

---

G. li, P. Sarazin, W.J. Orts, S.H. Imam, B.D. Favis, Biodegradation of thermoplastic starch and its blends with poly(lactic acid) and polyethylene Influence of morphology. Macromol. Chem. Phys. 212, 1147-1154 (2011)... 

Poly(E-caprolactone) blends with poly(lactic acid) have been compatibilized in the presence of polyepoxide or either di- or trisisocyanate (Harada et al. 2008). 

Teixeira, E., Curvelo, A., Correa, A., Marconcini, J., Glenn, G., and Mattoso, L. (2012) Properties of thermoplastic starch from cassava bagasse and cassava starch and their blends with poly (lactic acid). Industrial Crops and Products, 37(l) 61-68. 

WAN 01] Wang H., Sun X.Z., See P., Strengthening blends of poly(lactic acid) and starch with methylenediphenyl diisocyanate , Journal of Applied Polymer Science, vol. 82, no. 7, pp. 1761-1767,2001. 

Blends of poly(lactic acid) and poly((butylene-adipate)-co-terephthalate) have been prepared with the addition of either 2,2 -(l,3-phenylene)-bis(2-oxazoline) or phthalic anhydride (Dong et al. 2013). Blends were characterized using DSC, SEM, and mechanical properties. 

Krishnaswamy et al. (2013) prepared blends of poly(lactic acid) with poly (3-hydroxybutyrate-co-4-hydroxybutyrate) containing 17 10 wt% 4-hydroxybutyrate in the presence of radical initiator. Blends were characterized by melt strength, viscosity, and mechanical properties. Blend properties were compared to control blends without RI. 

Li et al. (2012c) prepared blends of poly (lactic acid) with PP in the presence of radical initiator. Blend characterization techniques included DSC. The effects of different radical initiators and different concentrations of RI were studied. 

Imre et al. (2013) also prepared compatibilized blends of poly(lactic acid) with polyurethane elastomer by coupling reaction under extrusion conditions. Copolymer formation was shown by SEM, AFM, DMA, and mechanical property measurement. 

Table 5.7 Summary of Reported Mechanical Properties for Blends of Poly(lactic Acid) (PLA) with Polycaprolactone (PCL)... 

Lee, S., Lee, Y., and Lee, J.W. (2007) Effect of ultrasound on the properties of biodegradable polymer blends of poly (lactic acid) with poly(butylene adipate-co-terephthalate). Macromd. Res., 15, 44-50. 

The subject of IR and Raman-spectroscopic imaging has been covered comprehensively in a recent book [86]. In contrast to mapping, modern imaging techniques are based on the use of focal plane array detectors which allow the rapid characterization of multicomponent polymer samples such as blends of PMMA or poly(ethylacrylate) with polystyrene, or of poly(3-hydroxybutyrate) with poly(lactic acid). 

Polymer Blends. The miscibility of poly(ethylene oxide) with a number of other polymers has been studied, eg, with poly (methyl methacrylate) (18—23), poly(vinyl acetate) (24—27), polyvinylpyrroHdinone (28), nylon (29), poly(vinyl alcohol) (30), phenoxy resins (31), cellulose (32), cellulose ethers (33), poly(vinyl chloride) (34), poly(lactic acid) (35), poly(hydroxybutyrate) (36), poly(acryhc acid) (37), polypropylene (38), and polyethylene (39). 

Other blends such as polyhydroxyalkanoates (PHA) with cellulose acetate (208), PHA with polycaprolactone (209), poly(lactic acid) with poly(ethylene glycol) (210), chitosan and cellulose (211), poly(lactic acid) with inorganic fillers (212), and PHA and aUphatic polyesters with inorganics (213) are receiving attention. The different blending compositions seem to be limited only by the number of polymers available and the compatibiUty of the components. The latter blends, with all natural or biodegradable components, appear to afford the best approach for future research as property balance and biodegradabihty is attempted. Starch and additives have been evaluated ia detail from the perspective of stmcture and compatibiUty with starch (214). 

The blending of different polymers is a frequently used technique in industrial polymer production to optimize the material s properties. The biodegradable polymer poly(3-hydroxybutyrate) (PHB) [45, 46], for example, which can be produced by bacteria from renewable resources, has the disadvantage of being stiff and brittle. The mechanical properties of PHB, however, can be readily enhanced by blending with another biopolymer, poly(lactic acid) (PLA) [47]. In order to prepare the optimum blend, it must be noted that the miscibility of different polymers depends on their concentration, the temperature, and their structural characteristics [48]. 

One of the most promising applications of polyolefin hybrids is a compatibilizer for blend polymer for polyolefin and non-polyolefin. In Figure 7, TEM micrographs of PP/PMMA and EBR/poly(lactic acid) (PLA) blend polymers with and without polyolefin hybrids as a compatibilizer are displayed. Figure 7(a) represents the phase stracture of a PP/PMMA (62/38 wt%) blend polymer. Since PP and PMMA are immiscible, huge PMMA domains (> 20 pm) exist in the PP matrix. When 5 wt% of PP-g-PMMA (PMMA contents 38 wt%) was added to this blend polymer as a compatibilizer, PMMA domains were finely dispersed as is shown in Figure 7(b). As a result, the physical properties for both FM and FS were drastically enhanced from 35.3 MPa for FS and 1800 MPa for FM to 61.4 MPa for FS and 2200 MPa for FM, respectively. 

Ren, J., Fu, H., Ren, T., and Yuan, W. (2009]. Preparation, characterization and properties of binary and ternary blends with thermoplastic starch, poly(lactic acid] and poly(butylene adipate-co-terephthalate]. Carboh dnPoI m., 77, 576-582. 

Zhang, N., Wang, Q., Ren, J., and Wang, L. (2009]. Preparation and properties of biodegradable poly(lactic acid]/poly(butylene adipate-co-terephthalate] blend with glycidyl methacrylate as reactive processing arent. I. Mater. Sd.. 44, 250-256. 

---