Photodegradation of some poly(vinyl chloride) (PVC) blends: PVC/ethylene‐vinyl acetate (EVA) copolymers and PVC/butadiene‐acrylonitrile (NBR) copolymers

Poly(vinyl chloride) (PVC) and its blends with polybutadiene‐acrylonitrile (NBR) (containing 21.7 weight‐percent acrylonitrile (AN), a heterogeneous two‐phase system; and containing 41.6 weight‐percent of AN, a homogeneous one‐phase system) and with polyethylene‐vinyl acetate (EVA) (containing 45 weight‐percent of vinyl acetate (VA), a heterogenous two‐phase system; and containing 65 weight‐percent VA, a homogeneous one‐phase system) were UV‐irradiated (at 3500 Å UV‐light (solar spectrum)). After UV irradiation the kinetics measurements were made of the formation of hydroperoxy (OOH) and carbonyl (CO) groups and the changes of mechanical properties: tensile strength, elongation to break, and impact energy. As a result of the photooxidative degradation of PVC blends, decreases of mechanical properties were observed. The effects are more severe in PVC/NBR blends, which contain unsaturated bonds (polybutadiene segments) than in the case of PVC/EVA. The phase structure plays an evident role on the UV degradation only of PVC/NBR blends. The photostability of PVC blends can be slightly improved by introducing Tinuvin P or Ni‐chelates photostabilizers.