摘要:

AbstractThe kinetics of the initiated cumene oxidation at 60°C in the presence of polyarylenes (polyanthracene (PA), polynaphthalene (PN), copolymers of benzene with anthracene (AB), and naphthalene (NB) has been investigated. The initial oxidation rate dependence upon the initial concentration of inhibitor has been described by the equation obtained for inhibition mechanism which defines the radical attaching to a molecule of inhibitor as the rate limiting step of the reaction, rather than the reversible complex formation. Radical reactivity of polyarylenes increases in the order NB

ISSN:0360-8905    

DOI:10.1002/polc.5070400113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractSeveral materials derived from kraft lignin have been shown to exhibit distinct antioxidant activity for the stabilization of raw rubber against heat accelerated degradation. Selected lignin derivatives alone or in combination with amine or sulfide antioxidants were effective stabilizers for an oil‐extended styrene‐butadiene rubber (SBR). Synergism with a phosphite has been demonstrated with unextended SBR.Candidate stabilizers were screened using the relatively rapid torsional braid analyzer (TBA) technique. Pertinent samples were then tested with the conventional, but slower, technique of measuring Mooney viscosity. Mooney and TBA tests correlated for lignin derivatives, but the TBA predictions were low for typical commercial stabilizers such as phenyl‐beta‐naphthylamine (PBNA). Apparently the more volatile stabilizers, such as PBNA, escape during the aging process from the thin rubber sample employed in TBA testing. This observation limits the utility of the TBA technique to samples of similar and preferably low volatility.Lignin derived stabilizers are unique in that they are non‐discoloring, nonstaining, and relatively low in volatility

ISSN:0360-8905    

DOI:10.1002/polc.5070400114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe efficiency of homolytic splitting of the OH bond of different phenols, bisphenols, thiophenols, naphthols, and benzophenones and the transfer of the hydrogen atom to an alkoxy or alkyl‐peroxy radical is a function of the electro‐affinity of the substituent in the ortho position. The stability of the formed phenoxy radical is in relation to the delocalization of free electron in the para position, especially if the substituent has aromatic character. The inhibition effect of thermal oxidation is found to be the highest in that case where the substituent does not hinder the recombination of RO2radicals with those of antioxidant.According to the electron paramagnetic resonance spectra of the generated phenoxy radicals the differently substituted phenols can be divided into five main groups: 1) phenols which form primary stable free radicals; 2) phenols which form secondary stable free radicals, 3) phenols which give stable phenoxy radicals only after coordination into the ligand field of the transition metal; 4) phenols whose radicals undergo disproportionation; 5) phenols substituted with NO2groups which do not form free radicals in nonpolar solvent.Cobalt traces induce the decomposition of hydroperoxides generated in thermal initiation of polymer oxidation by quite a similar redox mechanism as the one observed in the fixation of RO2radicals on transition metal. But the cobalt compounds are not active in polymers if those are free from oxidation products (hydroperoxy grou

ISSN:0360-8905    

DOI:10.1002/polc.5070400115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractIn nonpolar solvents the mechanism of bimolecular substitution reactions between t‐butyl‐peroxy and t‐butoxy radicals with different phenols and diarylamines was quantitatively studied by means of electron paramagnetic resonance (EPR) spectroscopy in the temperature range of +70 to −140°C. The selective reactivity, in the ligand field, of cobalt complex‐bonded radicals [Co] BuO2, [Co] BuO., and the free continuously generated noncomplex‐bonded BuO2and BuO radicals to antioxidants are compared. The antioxidant ArH forms with cobalt (II)‐acetylacetonate a complex [Co(acac)2]2[Arh]n= 1‐4 and prevents the subsequent reactions of the primarily generated RO. radicals with the transition metal (RO. + Co(II) → RO′ + Co(III)) and with the excess of hydroperoxides (RO. + ROOH → ROH + RO2). The concentration and the ratio of RO. and RO.2radicals in a chain oxidation process in the presence of phenyl β‐ or α‐napthylamine (Ar1HNAr2) can be determined from the different EPR spectra of fixed [Co] [Ar1NAr2]. and free stable

ISSN:0360-8905    

DOI:10.1002/polc.5070400116

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe ESR method has been used for the study of the inhibition effect of some antioxidants on polymerization of methyl methacrylate proceeding in the surface of synthetic faujasite of the Na Y type. From equilibrium levels of trapped radicals the inhibitor efficiency has been elucidated as follows: hydroquinone>diphenylamine>2, 6‐di‐tert‐butyl‐4‐methylphenol>pyrogallol>N‐phenyl‐2‐naphthylamine>1‐naphthol.Mechanism of hydroperoxides decomposition on zeolite surface has been

ISSN:0360-8905    

DOI:10.1002/polc.5070400117

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe chemiluminescence method was used to study the reaction of peroxy radicals with stable radicals of X2NO.type where Corresponding courses of chemiluminescence intensity were followed either in low molecular solvents (ethyl benzene, dioxane) or in benzene solutions of polystyrene and in poly(ethylene oxide). The ratio ki/kt0.5of rate constants of peroxy radicals and stable radicals recombination (ki) and mutual peroxy radicals termination (kt) was measured at 60°C. This value for ethyl benzene is 54.2 (1. mole−1sec−1)0.5, for benzene 27.7 (1. mole−1sec−1)0.5, and for 5% benzene solution of polystyrene 19.3 (1. mole−1sec−1)0.5, respectively.Similar systems in dioxane and poly(ethylene oxide) exhibited different courses of chemiluminescence intensity than those in ethyl benzene

ISSN:0360-8905    

DOI:10.1002/polc.5070400118

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe reactivity of (‐)‐ephedrine, free or bonded in copper complex, in the transfer reactions with free radicals was studied. The reactivity of the ligand functioning as a hydrogen donor was expressed by the ratios of the rate constants of the interaction of 2,2′diphenyl‐1‐picrylhydrazyl (DPPH) with bis‐(−)‐ephedrine copper(II) chelate (k1), (−)‐ephedrine (k2), and cumene (k3). Thus the values 100 mole0.51.−0.5and 2.5 mole0.51.−0.5were found for the ratios k1/k2and k1/k3, respectively. These data indicate a significant effect of copper ion on the reactivity of (–)‐ephedrine in the transfer r

ISSN:0360-8905    

DOI:10.1002/polc.5070400119

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

Abstract4,4′‐isopropylidene‐bisphenol and some of its methyl and tert‐butyl derivatives were studied by inhibiting the radical polymerization of vinyl acetate. Alkyl groups in the bisphenol increase the radical reactivity. The substituent effect is significantly additive, i.e., the individual groups contribute independently to the reactivity. As a contrast, in the case of 2, 6‐tert‐Bu2substitution a steric effect emerges. The analogy between the reactivities of phenols and bisphenols is

ISSN:0360-8905    

DOI:10.1002/polc.5070400120

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe changes in concentration of 2‐hydroxy‐4‐octyloxybenzophenone, Cyasorb UV‐1084, and Tinuvin P during the photooxidation of films of polypropylene, stabilized by these compounds, is determined. The change in concentration of the benzophenone derivative obeys zero‐order kinetics, while that of Cyasorb UV‐1084 tends to be first order. The concentration of both compounds has strongly decreased at the end of the induction period. The concentration of Tinuvin P decreases strongly only after the induction period. The implications of these results for the mechanism of UV stabilization ar

ISSN:0360-8905    

DOI:10.1002/polc.5070400121

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractOxidative dehydropolycondensation of diphenylamine (DPA) at 200–260°C leads to the formation of polymers with a system of conjugation, this process being a first order reaction with an activation energy of 20 kcal/mole. Polymeric products of the reaction (PDA) are found to contain fragments of quinone imine and triphenylamine structures and an insignificant quantity of NH groups. PDA reactivity towards peroxide radicals is significantly lower than that of DPA. PDA has higher activity than DPA by the inhibition of thermal oxidation of 1,4‐cis‐polybutadiene, ceresine, and SKN‐26 rubber, the largest effect being observed when PDA mixtures with DPA are used. PDA has high thermal and thermooxidative stability. PDA loses its solubility at the initial stages of destruction, then its destruction rate increases in air and remains constant in argon. Paramagnetic centers of PDA take part in the inhibition of destruction in air until the polymer completely loses its so

ISSN:0360-8905    

DOI:10.1002/polc.5070400122

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY