摘要:

AbstractThe kinetics and mechanism of the photochemical reactions of the peroxide radicals have been investigated in polytetrafluorethylene by electron paramagnetic resonance. Under irradiation by UV light, with λ<300 nm, the peroxide radicals ˜CF2CF(O2)CF2∼ and ∼CF2CF2O2are dissociated and the end fluoralkyl radicals ∼CF2CF2are produced. The activation effective energy of the photodissociation of the peroxide radicals is equal to approximately 1‐2 kcal/mole. Quantum yield of the dissociation of peroxide radicals is equal to about 1. In the presence of oxygen the photorecombination of the peroxide radicals takes place. The photorecombination of the peroxide radicals bring about a reversal of the reactions of the dissociation of the end peroxide radicals and the addition of oxygen to the end fluoralkyl radical. Due to a dependence upon the initial concentration of peroxide radicals, the quantity of molecules of CF2O produced varies from 25 to 45 per one vanished radical. The rate of the photorecombination of the peroxide radical is in linear dependence on light intensity and in the interval 150‐500 torr does not depend upon oxyg

ISSN:0360-8905    

DOI:10.1002/polc.5070400103

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe photodecomposition of films of poly(vinyl chloride) containing benzoyl peroxide and two aliphatic peroxides is investigated. It is proposed that the aromatic peroxide decomposed as a result of absorption of the irradiation, thus speeding up the early stages of the reaction but resulting in a lower final conversion. The aliphatic peroxides broke down as a result of energy transfer from polyenes and contributed to the propagation of the removal of HC1 with an increase in conversion. Films containing acenaphthene were ultimately more stable than the reference but decomposed faster in the early stages. It is suggested that energy transfer plays an important part in the mechanism.

ISSN:0360-8905    

DOI:10.1002/polc.5070400104

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe chemical transformations of poly(vinyl alcohol) (PVA) film by ammonium dichromate on exposure to ultraviolet irradiation have been investigated. The oxidative transformation was followed spectrophotometrically and the extent of crosslinking reaction by measuring the solubility and the viscosity changes of the exposed film. The influence of the time of exposure as well as the concentration of ammonium dichromate on the above reactions has been established.The ultraviolet and infrared data of exposed film showed that hydroxyl groups are oxidized to carbonyl groups. Absorption bands at 230, 270, and 330 mm, attributed to the presence of the double bond conjugated with carbonyl, were increased during the exposed period.The bromination and hydrogenation of the dissolved films decreased those absorptions. This indicated that the content of the carbonyl groups and double bonds were increased during the irradiation.The partial insolubilization of the exposed film was attributed to the formation of complexes of alcohol and carbonyl groups to chromic ions formed by reduction of the dichromate.

ISSN:0360-8905    

DOI:10.1002/polc.5070400105

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

年代:1973

数据来源: WILEY

摘要:

AbstractSimultaneously with the preparation of 2‐hydroxybenzophenone light stabilizers with a reduced extractability from polypropylene, the mechanism of the propagation reaction of 2‐hydroxy‐4‐(2,3‐epoxypropoxy) benzophenone with phthalic anhydride was studied under different concentrations and temperature conditions, with tert‐amines, potassium benzoate, and potassium hydroxide being used as catalysts. If the polymerization of epoxide with anhydride is performed in melt at 125°C, an alternating copolymer is formed whether an equimolar ratio or a molar excess of anhydride with respect to epoxide has been used. Provided epoxide is present in molar excess with respect to anhydride in the reaction system, some changes in ultraviolet absorption spectra are observed in comparison with the spectra of alternating copolymers which indicate that some undesirable reactions of the orthophenolic groups of benzophenone occur simultaneously with the catalyzed polyaddition reaction, and that the polymeric stabilizer

ISSN:0360-8905    

DOI:10.1002/polc.5070400106

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

年代:1973

数据来源: WILEY

摘要:

AbstractMonomeric carbazole derivatives show phosphorescence in the wavelength region between 400 and 500 nm. Poly(vinyl carbazole) (PVCA) in dilute frozen solutions also shows phosphorescence in this region and, in addition, delayed fluorescence owing to triplet‐triplet annihilation. The latter depends on the molecular weight of the polymer, high‐molecular weight samples showing very strong delayed fluorescence, whereas in low‐molecular weight products phosphorescence prevails.The phosphorescence of solid PVCA is governed by traps. Comparison with low‐temperature fluorescence and measurement of decay times suggest that two traps are important for both singlet and triplet excitons. The excimer‐forming site is one of them. The maximum of triplet excimer emission is at about 500 nm, the decay time is 7.9 ± 1 sec (compared to 410 nm and 43 nsec in the singlet system). The second trap emits in the same wavelength region, decay time 1.4 sec, and corresponds to a second intrinsic singlet trap emitting at 380 nm (decay time 12 nsec). The range of the triplet exciton at 77°K is drastically reduced by these traps, as in the case of the sin

ISSN:0360-8905    

DOI:10.1002/polc.5070400107

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe Stern‐Volmer constant of 40 quenchers was determined at 366 nm for poly(vinyl phenyl ketone) photolysis in benzene and dioxane solution at room temperature. Aromatic hydrocarbons, dienes and olefins were used as quenchers. A procedure for quantitative separation of the screening effect of quenchers absorbing at irradiation wavelength was elaborated. The correctness of this procedure was checked using 2‐hydroxy‐5‐methyl benzophenone over the concentration range 0‐10−3mole/1. The values of the Stern‐Volmer constants lay within the range 0‐250 1./mole, expressing changes of the rate constant of quenching. Stern‐Volmer constants were found to be constant for naphthalene, its alkyl, halogen derivatives and esters at about 70 1./mole, that of 1‐naphtyl amine 1‐ and 2‐naphtol being, however, substantially higher. Electron‐deficient olefins were equally effective as dienes. There has not so far been found a parameter to characterize unambiguously the quenching efficiency of t

ISSN:0360-8905    

DOI:10.1002/polc.5070400108

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe effect of thermal‐oxidative processing on the stability to ultraviolet irradiation of high density polyethylene containing a catechol hindered‐phenyl phosphite has been studied by periodic observation of carbonyl index by infrared spectrometry and by recording embrittlement times.Certain of the possible thermal‐oxidative reaction products of catechol hindered‐phenyl phosphite, catechol hindered‐phenyl phosphate and mono‐(σ‐hydroxyphenyl)phosphoric acid have also been studied. The results are consistent with the theory previously developed that the latter or its dehydration product, catechol hydroxy phosphate, is the effective antioxidant produced dur

ISSN:0360-8905    

DOI:10.1002/polc.5070400109

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe behavior of organic phosphites as antioxidants for polyethylene, costabilizer, and metal‐deactivator for poly(vinyl chloride) (PVC), has been studied by Thermox‐meter and Brabander plastograph. It was found, that their antioxidative effectivity is determined by the self‐stability of the investigated phosphites, namely the volatility, the hydrolysis and oxidation sensitivity. At the same time, the stabilizing and metal‐deactivating effect for PVC with this technique did not show significant diff

ISSN:0360-8905    

DOI:10.1002/polc.5070400110

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe decomposition of the cumene, tetralin, andt‐butylhydroperoxides in the presence of zinc diisopropyl dithiophosphate and of radical‐type inhibitors has been studied. A poisoning of the catalyst and a further change into an inactive form has been found. This leads to an inhibition of the overall decomposition rate of the hydroperoxides. It is suggested that the accumulation of RO* radicals arising from the thermal decomposition of the hydroperoxides reactivates the inactive catalyst. Based on the consumption of phenyl‐β‐naphtylamine and the stable 2,2,6,6‐tetrametylpiperidinoxyl radical, a homolytic decomposition of the hydroperoxides has been shown to take place. The rate of decomposition of the hydroperoxides to free radicals is 103times slower than that leading to molecula

ISSN:0360-8905    

DOI:10.1002/polc.5070400111

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe inhibiting activity of poly (2‐methyl‐5‐ethynylpyridine) (PEP) has been studied in the cumene oxidation reaction initiated by azobisisobutyronitrile at 55–65°C. According to the kinetic data the reaction between RO2radical and PEP is irreversible. About 12% of the most active macromolecules of PEP react during the induction period followed by retarded oxidation of cumene. The quantity of terminated peroxy radicals reaches 1.5 per molecule of the inhibitor. This quantity is not altered when PEP concentration changes. Macromolecules of PEP differ in their radical reactivity. An increase of PEP molecular weight leads to the increase in PEP reactivity and in the fraction of active molecules. The paramagnetic centers of PEP interact with peroxy radicals at the maximum rate and disappear at the initial stage of o

ISSN:0360-8905    

DOI:10.1002/polc.5070400112

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

年代:1973

数据来源: WILEY