Organic thermal stabilizers for rigid poly(vinyl chloride) VIII. Phenylurea and phenylthiourea derivatives

Evaluation of the stability of rigid poly(vinyl chloride)/biologically active phthalimido phenyl urea composites using thermogravimetric analysis

“…This may be attributed to the presence of the methyl group with its highest donation power that can increase electron density on both the phenyl urea and phthalimide moieties most easily and thus accelerate the replacement of the labile chlorines and increase the disruption of the formation of conjugated double bonds leading to increasing the stability of the PVC sample and consequently the degree of the discoloration decreased. The results obtained for the degree of discoloration give an additional proof for the stabilization mechanism reported previously[20,26]. 3.7.…”

“…This mode of action has previously been published together with experiments to prove it [20,26]. In view of structural similarity of the investigated stabilizers to phthalimide combined with phenyl urea, their mechanism is outlined by assuming that both of their parts (phthalimide and phenyl urea) can displace the labile chlorine atoms on PVC chains deactivating their reactivity.…”

“…Furthermore, phenyl urea derivatives can exhibit their stabilizing efficiency through effective absorption of the degradation product (hydrogen chloride gas) by their basic groups preventing or at least minimizing its catalytic degradation effect [26]. This mode of action has previously been published together with experiments to prove it [20,26].…”

“…It has been previously suggested that N-substituted phthalimides [20] and phenyl urea derivatives [26] owe their stabilizing efficiency to the replacement of the labile chlorine atoms on the PVC chains by more relative thermally stable phthalimide and phenyl urea moieties. Thus, the phthalimides and phenyl urea derivatives are able to be incorporated into the body of the polymeric chains deactivating the reactive sites (primarily allylic chlorines bearing carbon atoms) on the PVC.…”

Additives effects on the shrinkage behavior of PVC sheets

“…3,[6][7][8][9][10] Nevertheless, thermal degradation of PVC is one of the inherent problems associated with the manufacture and use of some polymers. 11 These problems can be minimized by introducing stabilizing additives, which generally contain heavy metals such as cadmium and lead, organotin compounds, 12 phosphites, 13 and calcium and zinc salts. 14,15 But it is shown that the latter ones have less toxicity and so they can be used as heat stabilizers in most applications, especially food packaging and medical devices.…”