Radiation-induced Crosslinking Of Poly Research Articles

Radiation-induced crosslinking of poly(styrene–butadiene–styrene) block copolymers and their sulfonation

Several crosslinked poly(styrene–butadiene–styrene) (c-SBS) block copolymer films were prepared using a gamma ray or electron beam with various irradiation doses and the prepared c-SBS film was then subjected to sulfonation using a chlorosulfonic acid (CSA) solution to introduce a sulfonic acid group. To estimate the degree of crosslinking, the gel fractions and FT-IR spectra of the c-SBS films were used and the results indicate that the degree of crosslinking is increased with an increase in the radiation dose. The surface morphology and mechanical property of the c-SBS films were observed using SEM and UTM instruments, respectively. The sulfonated c-SBS films were investigated by measuring the ion exchange capacity (IEC) and by observing the cross-sectional distribution patterns of sulfonic acid group using an SEM-EDX instrument. The IEC and SEM-EDX studies indicate that the sulfonated c-SBS membranes can be successfully prepared through the radiation crosslinking of the SBS film and the subsequent sulfonation with a diluted CSA solution.

Radiation-induced crosslinking of poly(methyl methacrylate)-poly(ethylene oxide) blend

Radiation-induced crosslinking of poly(methyl methacrylate) (PMMA)-poly(methylene oxide) (PEO) blends was studied. It was found that PMMA in PMMA-PEO blend can be crosslinked in the range of certain doses (1 approximately 20 x 10(4) Gy) and composition (PMMA% = 30 approximately 70) under the absence of oxygen. Moreover, it was also found that the crosslinking degree of PMMA in the blend in which the content of PMMA is 70% is the largest. The crosslinking degree of PMMA in the blend is closely related with the polymer miscibility. The crosslinking degree of the blend prepared at 60-degrees-C is far higher than one at ambient temperature.

Primary Processes in Radiation-Induced Crosslinking of Poly(2-phenylbutadiene)

The radiation-induced crosslinking of poly(2-phenylbutadiene) (PPB) in ethylene dichloride solution was studied in vacuum at 303 K. The G value of the crosslinking was estimated to be about 7.2. In order to detect the reaction intermediates under irradiation, optical absorption spectra in rigid matrices and ESR spectra in bulk were measured. The absorption spectra due to radical cation of PPB and due to α,α-disubstituted benzyl cation were observed in butyl chloride glass. ESR spectra owing to polyenyl type radical was found in the irradiated specimens of PPB and Diels-Alder type dimer of 2-phenylbutadiene. The primary processes in radiation-induced cross-linking of PPB were discussed on the basis of the results obtained.

Radiation-induced Crosslinking of Poly(vinylidene fluoride)

The radiation-induced crosslinking, chain scission, and oxidation of poly(vinylidene fluoride) (PVdF) have been studied. The irradiation was carried out with r-rays and electron beams at ambient temperature under vacuum and in the presence of oxygen. The gel formation, solution viscosities, and number average molecular weight of the PVdF so treated, as well as the evolutien of hydrogen fluoride (HF) and other gases were measured. IR and UV spectra were also obtained.When PVdF was irradiated under vacuum, the G value for crosslinking was O.6, vO.8. This was equal to the G value for chain scission (Table 1). Double bonds including polyenes were formed as a result of dehydrofluorination. The concentration of polyenes was, however, low and decreased with increase in the number of conjugated unsaturation. Polyenes 1enger than tetraene were hardly observable (Fig.6). The G value for the formation of HF was reduced from 3.5 to 3.0 when HF was removed with dry potassium hydroxide during irradiation (Table 3). This result suggests the accelerating effect of HF on the radiolytic dehydrofluorina tion of PVdF.Oxygen accelerated the chain scission and dehydrofiuorination of PVdF (Figs.1, 3, 4, and Table 3). Those effects are dependent on dose rate and the thickness of samples. At high dose rate (electron beams), there was little effect, while the remarkable effect was obserVed at low dose rate; the thinner the sample the more the effect. Carbonyls such as acid fluoride and carboxylic acid were detected as the oxidatien products (Figs.8 and 9).The reactieR mechanism is discussed in connection with the results obtained here and ESR

On the mechanism of radiation-induced crosslinking of poly(vinyl chloride) in the presence of some polyfunctional monomers

Some features of low-temperature radiolysis of poly (vinyl chloride) and the effect of added polyfunctional monomers such as triallyl cyanurate have been studied using the technique of infrared spectrophotometry. It has been found that the radiation yield of HCl formed in the radiolysis of poly(vinyl chloride) alone at 100°K is equal to 2.5. Additives form a complex with radiolytically produced HCl. The structure of this complex corresponds to on oxonium compound. The radiation yield of the complex reaches 50–80 per 100 eV of energy absorbed by additives. At the same time, the addition of triallyl cyanurate in poly (vinyl chloride) decreases the radiation yield of HCl associated with polymeric matrix by 2–3 times. The reaction of the allyl groups of the additive with the polymer free radicals already occurs at low temperatures. On heating, the irraditated at low temperature samples, the complex of additive with HCl decomposes, the remaining allyl groups disappear, and triazine rings are partly transformed to the isocyanurate form. These results are interpreted in terms of a mechanism which postulates the localization of the dehydrochlorination process of poly(vinyl chloride) in the vicinity of the additive molecules and the promotion of crosslinking efficiency by the formation of complex of additive with HCl.