Toughening of Poly(l-Lactide) with Branched Polycaprolactone: Effect of Chain Length

Abstract

In this work, a series of branched polycaprolactone (BPCL) samples with different ε-caprolactone (CL) chain lengths were synthesized and used to toughen poly (lactic acid) (PLA). The spherical structure increased the free volume, facilitating the free movement of the PLA chain segment and increasing the ductility. In addition, the hydrogen bonds between the multiterminal hydroxyl group of BPCL x and PLA improved the interaction between them. The glass-transition temperatures (T g ) and crystallization temperatures (T c ) of the blends were significantly lower than those of PLA, and these temperatures increased with the chain length of polycaprolactone. BPCL x increased the crystallization rate of PLA through heterogeneous nucleation. A longer chain length of CL increased the mutual entanglement in the blends, reduced the hydrogen bonding between BPCL x and PLA, and increased the entanglement of BPCL x chains. When the chain length of CL was 6, the impact strength and elongation at break of the PLA/BPCL blends exhibited an increase of 151.72 and 465.8%, respectively, as compared with PLA.

Effects of hetero‐armed star‐shaped PCL‐PLA polymers with POSS core on thermal, mechanical, and morphological properties of PLA

“…4 Yang et al also concluded similar results, they observed increments with the increase of chain length at first, but then a decrement was observed especially in toughness because of chain entanglements. 29 Likewise, Liu et al determined 15% branched PCL content as optimal concentration to toughen PLA without injuring other properties such as tensile strength, crystallization, and rheological behaviors. 34 The yield strength increased with PLA/SPLA blends prepared at 95/5 and 90/10 ratios, but there was no significant change with blends prepared at 80/20 ratio.…”

“…26 It is given in the literature that polymers with different branched three-dimensional structures improved the processing and mechanical properties of PLA. [27][28][29][30][31][32][33][34] Deokar et al prepared different molecular weight multiarmed star copolymers with PLA and PCL. The elongation enhanced with the increment of arm number of the copolymers.…”

“…The spherical structure of the branched polymer increased the free volume providing the free movement of the PLA chain segment and increased the ductility. 29 A long chain branched copolymers of PCL and PLA were another synthesized branched polymer for enhancing mechanical properties of PLA. 33,34 In our previous study, we synthesized POSS cored eight arm star PCL polymers (SP) and prepared blends with commercial PLA at different blending ratios.…”

“…Broz et al prepared a series of PLA/PCL blends and found that there were minimum interactions and adhesion at the interface of two polymers 26 . It is given in the literature that polymers with different branched three‐dimensional structures improved the processing and mechanical properties of PLA 27–34 . Deokar et al prepared different molecular weight multiarmed star copolymers with PLA and PCL.…”

“…Yang et al synthesized branched PCL polymers having different chain lengths and mixed with PLA. The spherical structure of the branched polymer increased the free volume providing the free movement of the PLA chain segment and increased the ductility 29 . A long chain branched copolymers of PCL and PLA were another synthesized branched polymer for enhancing mechanical properties of PLA 33,34 .…”