光交联聚乙烯材料的光稳定性研究

本文中用紫外光敏化的方法对低密度聚乙烯进行了交联,并利用ESCA和ATR-IR等手段研究了交联后材抖的光稳定性及其改进办法。     

Metal salts of 2-[(1-hydroxy-2-naphthalenyl)carbonyl]-benzoic acid as a new class of photostabilizers

Metal salts (Co²⁺, Mn^2?, Ni²⁺) of 2-[(1-hydroxy-2-naphthalenyl)carbonyl]-benzoic acid can be considered as a new class of stabilizers effective against free radical photo-oxidation and singlet oxygen oxidation of cis-1,4-polybutadiene. These metal salts are active by a combination of several important effects such as reducing the number of photons absorbed by polymer chromophores, deactivation of excited carbonyl groups, scavenging of free radicals and quenching of singlet oxygen.     

MAGNETIC FIELD EFFECT ON PHOTOPOLYMERIZATION OF STYRENE MICROEMULSION

External magnetic field increases the photo-induced polymerization rate of styrene microemulsion.The type of photoinitiator plays an important role. The photoinitiators, used are dimethoxyphenyl acetophenone(DMPA), 1-hydroxycyclohexyl phenylketone (Irgacure 184) and dimethylhydroxyacetophenone (Darocur 1173). No magnetic effect was observed by using dibenzylketone (DBK) as photoinitiator. The molecular weight of the polymer is slightly affected by magnetic field. The influence of temperature has also been investigated.     

DYE-SENSITIZED PHOTOOXIDATION OF 1,4-POLYDIENES

Abstract— The reaction of singlet oxygen with polydiene polymers produces hydroperoxides by the typical 'ene' type reaction. The observed chain scission process cannot be explained by the photodecom-position of hydroperoxide formed by visible light, because these hydroperoxides do not absorb light in this repion. Spectroscopic and EPR studies of the dye-solvent systems show the formation of reactive free radicals. which are probably responsible for the abstraction of hydrogen from the polymer molecules. The next step is the well known free radical oxidation mechanism which is responsible for the chain scission reactions.     

Studies on modified benzotriazoles as photostabilizers for poly(vinyl chloride)

It has been found that modified benzotriazoles: (2-(2-hydroxy-3-chlormethylacetamid-5-methylphenyl)2H-benzotriazole, 2-(2-hydroxy-3[(N,N-di-n-butyl)acetamidmethyl]-5-methyl-phenyl)2H-benzotriazole and 2-(2-hydroxy-3[(N,N-di-n-octyl)acetamidmethyl]-5-methyl-phenyl)2H-benzotriazole) have photostabilizing properties similar to those of Tinuvin P (2-(2-hydroxy-5-methylphenyl)2H-benzotriazole) for the photo-oxidative degradation of PVC under 3665 and 2537 A. The migration rate of stabilizers in a polymer matrix is decreased by introducing long chain groups. The possible mechanism of photosensitization is discussed.     

LAMINATION OF POLYMER FILMS BY BULK SURFACE PHOTOGRAFTING PROCESS AND PROPERTIES

A new process for lamination of polymer films by "bulk surface photografting" has been developed. The chemicalcomponent of the invention is that the curing of reactive solution between two substrates is initiated by the surface freeradicals produced by aromatic ketones and surface-hydrogen of substrates. Using the new approach, two or more polymerfilms are bonded together by a grafted polymer network which is grafted to adjacent substrate surfaces. The technique hasbeen applied to film substrates of different polymers such as polyolefins, polyesters. and polyamides which have abstractablehydrogens at the surface. The photolaminated film composites containing carrier films and an intermediate functional film of low permeability give strong laminates with high barrier properties, e.g. for oxygen and air.     

The effect of 1,3-diphenylisobenzofuran on the photo-oxidative degradation of cis-1,4-polybutadiene

1,3-Diphenylisobenzofuran (DPBF) is easily photo-oxidized by two mechanisms viz free radical oxidation and singlet oxygen oxidation. The final products of DPBF oxidation by these two mechanisms are the same. Using light in the range 280–480 nm, DPBF is an effective sensitizer of photooxidative degradation of polybutadiene in the solid and in solution. In a system with methylene blue (MB) in methanol-benzene solution (0.5:9.5) where free radicals from MB and ¹O₂ are formed during irradiation with visible light, DPBF is oxidized by both ¹O₂ and free radical mechanisms. DPBF cannot stop free radical degradation of PB initiated by MB radicals in MB-methanol-benzene solution. These results show that the DPBF is an ineffective stabilizer for polydienes against ¹O₂ and free radical oxidation. It rather acts as a sensitizer for photo-oxidation of polydienes.