Part 7. Effects of poly(L‐lactide‐co‐ϵ‐caprolactone) on morphology, structure, crystallization, and physical properties of blends of poly(L‐lactide) and poly(ϵ‐caprolactone)

Abstract

Blended films of poly(L-lactide) [ie poly(L-lactic acid)] (PLLA) and poly(ε ε ε ε ε ε-caprolactone) (PCL) without or mixed with 10 wt% poly(L-lactide-co-ε ε ε ε ε ε-caprolactone) (PLLA-CL) were prepared by solution-casting. The effects of PLLA-CL on the morphology, phase structure, crystallization, and mechanical properties of films have been investigated using polarization optical microscopy, scanning electron microscopy, differential scanning calorimetry and tensile testing. Addition of PLLA-CL decreased number densities of spherulites in PLLA and PCL films, and improved the observability of spherulites and the smoothness of cross-section of the PLLA/PCL blend film. The melting temperatures (T m ) of PLLA and PCL in the films remained unchanged upon addition of PLLA-CL, while the crystallinities of PLLA and PCL increased at PLLA contents [X PLLA = weight of PLLA/(weight of PLLA and PCL)] of 0.4-0.7 and at most of the X PLLA values, respectively. The addition of PLLA-CL improved the tensile strength and the Young modulus of the films at X PLLA of 0.5-0.8 and of 0-0.1 and 0.5-0.8, respectively, and the elongation at break of the films at all the X PLLA values. These findings strongly suggest that PLLA-CL was miscible with PLLA and PCL, and that the dissolved PLLA-CL in PLLA-rich and PCL-rich phases increased the compatibility between these two phases.

Microstructure, Thermal Properties and Rheological Behavior of PLA/PCL Blends for Melt-blown Nonwovens

“…An improvement of the toughness of such brittle polymers can generally be achieved by blending a ductile secondary phase into the base polymer. PCL, a ductile biodegradable polymer, has been chosen as a blending partner for PLA, [10][11][12][13][14][15] and the fracture properties of PLA/PCL are found to be greater than those of pure PLA. However, it is also found that the immiscibility of PLA and PCL causes phase separation, and tends to lower the fracture properties.…”

Fracture Mechanisms of Biodegradable PLA and PLA/PCL Blends

“…In general, a blend of immiscible polymers such as PLLA and PCL creates macro-phase separation of the two components due to difference of solubility parameter. This kind of phase separation dramatically affects the physical and mechanical properties of the blend (Dell'Erba et al, 2001;Maglio et al, 1999;Tsuji et al, 2003). Dependence of PCL content on the critical energy release rate at crack initiation, G in , is shown in Fig.9.…”

“…Blending with ductile biodegradable polymers such as PCL (Broz, 2003;Dell'Erba, 2001;Chen, 2003;Todo, 2007;Tsuji, 1996Tsuji, , 1998Tsuji, , 2001Tsuji, , 2003, poly(butylene succinate-co-ε-caprolactone) (PBSC) (Vannaladsaysy, 2010) and poly (butylene succinate-co-L-lactate) (PBSL) (Shibata, 2006(Shibata, , 2007Vannaladsaysy, 2009;Vilay, 2009) has extensively been investigated in order to improve the fracture energy of PLA. Amoung of them, PCL is known to be bioabsorbable and bioaabsorbable, therefore has been applied in medical fields.…”

“…Its importance has led to many studies on its mechanical properties and fracture behavior which found that the mode I fracture behavior of PLA is relatively brittle in nature (Todo et al, 2002;Park et al, 2004Park et al, , 2005Park et al, , 2006. Therefore, blending with a ductile biodegradable and bioabsorbable polymer such as poly (ε-caprolacton) (PCL) has been adopted to improve the fracture energy of brittle PLA (Broz et al, 2003;Dell'Erba et al, 2001;Chen et al, 2003;Todo et al, 2007;Tsuji & Ikada, 1996, 1998Tsuji & Ishizuka, 2001;Tsuji et al, 2003); however, it was also found that phase separation originated by immiscibility of PLA and PCL tends to degrade the mechanical properties of PLA/PCL blends . It has recently been found that such phase separation can dramatically be improved by using an isocyanate group, lysine tri-isocyanate (LTI) Harada et al, 2007Harada et al, , 2008, and the fracture properties of PLA/PCL/LTI are much higher than those of PLA/PCL.…”

Characterization of Correlation between Microstructure and Fracture Properties of Poly(lactic acid) Polymer Blends

“…Its importance has led to many studies on its mechanical properties and fracture behavior [3][4][5][6][7] which found that the fracture behavior of PLA is relatively brittle in nature. Therefore, blending with ductile biodegradable polymers such as poly (ε-caprolacton) (PCL) has been adopted to improve the fracture properties [8][9][10][11][12][13][14]. Although PCL blend increases the fracture energy of neat PLA, it was also found that the polymer blend exhibits phase separation as a result of the immiscibility of the polymers [9].…”