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.

A series of multiarm structure hyperbranched polyester‐b‐poly(ε‐caprolactone) (HEPCLs) with different lengths of poly(ε‐caprolactone) (PCL) segments (s = 3, 6, 7, 8) were synthesized. Hyperbranched polyester (HE) was synthesized from glycidol and succinic anhydride and used as a macromolecular polymerization initiator for ε‐caprolactone. The HEPCLs were used as polyvinyl chloride (PVC) plasticizers and the mechanical properties, thermal properties, morphology, and migration stabilities of PVC films were explored. The plasticizing efficiency increased with the increase in PCL segments, and the plasticizing efficiency of HEPCL8 exceeded that of dioctyl phthalate. Scanning electron microscopy and solid‐state 1H NMR showed that the HEPCLs possess better compatibility with PVC than HE. Moreover, HEPCLs exhibited excellent migration stability even at very harsh condition, indicating that HEPCLs can be used as no‐migration PVC plasticizers in medical products, children's toys, and food packaging. J. VINYL ADDIT. TECHNOL., 26:35–42, 2020. © 2019 Society of Plastics Engineers

Bio-based phytic acid is a nontoxic naturally occurring compound and has the potential for use in polymers for flame retardancy due to its high phosphorus content. In this work, two novel phytic acid-based compounds, phytyl octyl glycidyl ether (PAOc) and phytyl phenyl glycidyl ether (PAPh), were prepared through the addition esterification of 2-ethylhexyl glycidyl ether and phenyl glycidyl ether with phytic acid. The chemical structure of PAOc and PAPh were confirmed by 1 H NMR, 31 P NMR, and FTIR spectra. The mechanical, thermal, and fire performances of the PLA/PAOc and PLA/PAPh blends were investigated by various tests including mechanical, thermal (DSC, TGA), morphological (SEM), and flammability (LOI, UL-94). The results showed that the addition of PAOc and PAPh improved the thermal stability of PLA through hydrogen bonding. PAPh was more effective to improving the mechanical properties and crystalline properties of PLA than PAOc. When PAPh was 5 wt %, the elongation at break of PLA increased from 2.9% to 16.7%, the tensile strength increased from 32 to 37 MPa, and the crystallinity increased from 30.6% to 36.7%. Moreover, introduction of phenyl group was beneficial to phytic acid improving the flame retardant properties of PLA. At an addition level of 10 wt%, the LOI of PLA/PAPh reached 27.5% and achieved UL-94-V0 rating while improving the mechanical properties.