SynopsisThe G H C~ values of 7-irradiated PVC mixtures were studied after addition of various amounts of three epoxy stabilizers: diglycidyl ether of 2,2-bis(4-hydroxy-3-methylphenyl)propane (I); diglycidyl ether of l,l-bis(4-hydroxyphenyl)cyclohexane (II), and butyl-cis-9,lO-epoxystearate (111). The results indicated that two processes are essential for the stabilization: HC1 capture by the epoxy groups, and an external protective effect, due to the remaining part of the stabilizer molecule. The role of the benzene rings in stabilizers I and 11, as compared with the protective effect due to the long chains of stabilizer 111, is not as dominant as one would expect.

SynopsisThe concentration of conjugated polyene sequences was studied in y-irradiated PVC with 4% admixture of four epoxy stabilizers: diglycidyl ether of 2,2-bis(4-hydroxy-3-methylphenyl)propane (I), styrene oxide (1,2-epoxy ethyl benzene) (IV), epoxidized ricinus oil (VI), and epoxidized soybean oil (Drapex 6.8) (VII). As in the former investigations (Papers I and II), the process of the formation of the polyenes occurs in two stages. The concentration of polyene sequences with n double bonds, H , the total amount of polyene sequences, ZH,, the average length of the polyene sequence, Fi, and the two extents of reaction Y and p , were computed. The stabilizing effect of all compounds used agrees with the increasing content of epoxy groups. The addition of stabilizers diminishes the value of Fi. The decrease of the fraction of long sequences and the increase of short ones occurs. Apart from the binding of evolved HCl, the protective effect towards the macromolecules of PVC consists mainly in the inhibition of growth of chain dehydrochlorination by the epoxy groups.

SynopsisThe G H C~ values of y-irradiated PVC mixtures and the changes of the epoxy group concentration were studied after addition of various amounts of five epoxy stabilizers: diglycidyl ether of 2,2-bis(4-hydroxy-3-methyl pheny1)propane (I), diglycidyl ether of 2,2-bis(4-hydroxy-3-nitrophenyl)-propane (II), styrene oxide (1,2-epoxy ethyl benzene) (IV), epoxidized ricinus oil (VI), and epoxidized soybean oil (Drapex 6.8.) (VII). It is stated that only about 50% of epoxy groups, declining in the system, take part in binding of HC1; the rest of these groups disappear as a consequence of other reactions. In connection with the data of the previous paper,' the results presented indicate that the process of stabilization goes in two stages. In the first stage the process consists of the HCI capture by the epoxy groups; in the second stage, due to the remaining part of the stabilizer molecule, a protective effect occurs. This effect consists, for the stabilizers I, 11, IV, of gaining the energy by the benzene ring and, for the stabilizers VI, VII, of a mechanical drawing of polymer chains, which makes the energy transfer more difficult. Having the greatest content of epoxy oxygen (about lo%), the styrene oxide (IV) stabilizes best.

SynopsisThe concentration of hydroperoxides, produced in the process of radiolysis, was studied in y-irradiated PVC samples with 4% admixture of four epoxy stabilizers: diglycidyl ether of 2,2-bis(4hydroxy-3-methyl pheny1)propane (I), styrene oxide (1,2-epoxy ethyl benzene) (IV), epoxidized ricinus oil (VI), and epoxidized soybean oil (Drapex 6.8.) (VII). The results indicate that the process of radiation oxidation occurs in two stages. Only the stabilizers with benzene ring demonstrate the antioxidative action. The stabilizers VI and VII do not act as the antioxidants, and, moreover, as a consequence of their plasticizing properties, they facilitate the penetration of the oxygen to polymer. The epoxy groups have no influence upon the oxidation process, in the case of compounds VI and VII.