Synthesis of a Cross-Linked Poly(vinyl chloride) Microsphere by Self-Stabilized Precipitation Polymerization and Its Contribution to Superior Enhancement in Toughness and Mechanical Strength of Rigid PVC

It remains a formidable challenge to explore novel synthetic approaches and realize a high performance for conventional plastics, especially for poly(vinyl chloride). Herein, we synthesize cross-linked poly(vinyl chloride) (CL-PVC) microspheres via self-stabilized precipitation (2SP) polymerization by using diallyl maleate (DAM) as a cross-linking agent. The effects of solvent composition, DAM concentration, stirring rate, monomer and initiator concentration, and monomer feeding modes on the particle size, gel content (GC), and morphology of the resultant CL-PVC microspheres are evaluated thoroughly. The mixture solvent of n-hexane and ethanol is suitable for conducting the 2SP polymerization of CL-PVC. Monodisperse microspheres have a linear increase in diameter from 405 to 648 nm with the DAM increasing from 0.25 to 16%. The GC values are highly reliant on both the amount of DAM and its feeding modes. Subsequently, the CL-PVC and dioctyl phthalate-extended CL-PVC (DECL-PVC) microspheres are utilized as functional polymeric fillers in a rigid PVC resin. It is encouraging that both mechanical and impact strengths are enhanced concurrently. When 5 phr DECL-PVC (GC = 30.08%) and DECL-PVC (GC = 76.23%) are added to the rigid PVC resin, the tensile strengths thereof can reach 73 and 78 MPa, respectively, which are much higher than that of the contrast (∼54 MPa). Meanwhile, the highest impact strength can reach 4.36 kJ/m2 by using 5 phr DECL-PVC (GC = 30.08%) as a toughening modifier, which increased by 53.0% than that of CL-PVC (2.85 kJ/m2) at a similar loading content and 209.2% than that of pure PVC (1.41 kJ/m2). This work offers a novel strategy for the synthesis of the CL-PVC microsphere and opens a new scope for its further use.