Poly lactic Acid and Polycaprolactone Blend

Broz et al. (2003) investigated the binary blends of PLA and PCL by dissolution in methylene chloride with a total polymer mass fraction of 10%. They found that the elongation at break only increased significantly for 60 wt% PCL content, and 

Yuan et al. (1998) synthesized semi-interpenetrating pol50ire-thane/PLA networks. The polyurethane was prepared using PCL diols and triols and toluene-2,4-diisocyanate. The optimum was found to be 5 wt% of crossUnked polyurethane network blended with PLA. The elongation at break increased to 60% and the tensile toughness increased to 18 MJ/m compared to 1.6 MJm for neat PLA. 

Grijpma et al. (1994) studied blends of PLA and a rubbery copolymer of caprolactone (CL) and trimethylene carbonate (TMC) (poly(TMC/CL)). They reported an increase in the notched Izod impact strength of neat PLA with the addition of 20wt% copolymer (from 40J/m to a maximum of 520 J/m). 

However, for homopolymer poly(TMC) and PLA blends, the corresponding wt% of mbber phase did not improve the notched Izod impact strength. Joziasse et al. (1998) have investigated blends of PLA homopolymer with poly(trimethylene carbonate) (poly(TMC)) mbbery copolymers. They found that the samples with 21 wt% of the mbber block of poly(TMC) in PLA did not break in an unnotched impact test. Diblock copolymers of L-lactide and caprolactone (P(LA/CL)) were also blended with PLA to determine their influence on the mechanical properties. The addition of 20 wt% of diblock copolymer improved the unnotched impact strength of the blend from 5 kJ/m to 50 kJ/m.  

Chen et al. (2003) observed that the addition of a low quantity of surfactant (i.e. copolymer of ethylene oxide and propylene oxide) could improve the elongation at break, but other mechanical properties, such as tensile strength and modulus, were simultaneously weakened. Moreover, the addition of a small amount of PLA—PCL—PLA triblock copolymer ( 4 wt%) to PLA/PCL (70 30) blends improved the dispersion of PCL in PLA and enhanced the ductility of the resultant ternary blend. The elongation at break increased from 2% for a PLA/PCL (70 30) blend to 53% for the ternary blend (Maglio et al.,1999). This has been proven to have been caused by the dispersion of PCL domains, which decreased from 10—15 to 3—4 im on addition of the triblock copolymer (4 wt%) as calculated from scanning electron microscope (SEM) micrographs of liquid-nitrogen-fractured surfaces of the blend. The mechanical properties for the PLA blends with PCL for the above studies are summarized in Table 5.7. 

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