Strengthening soft poly(vinyl chloride) plastics via three-arm star copolymeric plasticizers

Besides the good flexibility and extensibility, plasticized soft poly(vinyl chloride) (PVC) possessing the extra characteristics of high modulus, tensile strength and toughness are desired for wider applications. Herein, a series of three-arm star copolymers possessing the hard polylactide (PLA)-rich core and the soft poly(e-caprolactone)rich (PCL) shell (S3-PLA-PCL) were prepared, which were used as the plasticizers for the preparation of soft PVCs. The monomer ratio of e-caprolactone to lactide (LA), the average polymerization degree of LA and the type of LA (racemic or L type) were optimized to achieve the best mechanical performance of soft PVCs. With the similar elongation at break, S3-PLA-PCL plasticized PVC exhibited higher modulus, strength and toughness than PVCs plasticized by the corresponding linear PLA-PCL and other traditional low molar-mass and polymeric plasticizers without hard core. This pointed out the importance of the star topology and the hard PLA-rich core of S3-PLA-PCL in strengthening soft PVCs. The transparency of PVC plasticized by S3-PLA-PCL was similar to the neat PVC and PVCs plasticized by the traditional plasticizers. Migration stability tests demonstrated that S3-PLA-PCL had excellent migration resistance in PVC matrix. Moreover, both PLA and PCL are sustainable, biocompatible and biodegradable, hence, the as-prepared S3-PLA-PCLs can be called as high-performance, green polymeric plasticizers for PVC plastics.