Synthesis of poly(vinyl chloride)-co-poly(acrylic acid) by precipitation polymerization and its usage as CaCO3 modifier in rigid PVC composites

Incorporating carboxyl group into the poly(vinyl chloride) (PVC) resin can endow PVC with reactivity in some applications. In this work, poly(vinyl chloride)-co-poly(acrylic acid) random copolymer (PVCA) with low average number molecular weight (Mn, ∼10 k) is synthesized by precipitation polymerization. By tuning acrylic acid dropping rate, the PVCA copolymer with much more uniform copolymer composition is obtained in comparison to all monomer-in process. Subsequently, the PVCA is utilized as a novel polymer modifier for the surface treatment of CaCO3 particles and its effect on the mechanical properties of obtained rigid PVC composites are evaluated systematically. As a result, the PVAC modified CaCO3 particles exhibit uniform dispersibility and excellent compatibility in PVC matrix. Additionally, the thermal stability is improved significantly owing to the calcium ions on the surface of CaCO3 particles, which scavenge the hydrogen chloride and retard the autocatalytic dehydrochlorination process. Impressively, it also has an enhancement both in tensile strength (ca. 46.4 MPa, and 119.8% elongation at break) and in impact strength (2.7 kJ m−2) in comparison to those modified by commercialized agents such as stearic acid and titanate ester. This work provides valuable insights for the preparation of vinyl chloride copolymers and opens a new application.